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Mopar 2.2 and 2.5 TBI Power Upgrades

Neither Allpar nor any of the contributors take any responsibility for the results of your actions or for the results of following the steps or advice presented below. Some of these may shorten the lifespan of your car and/or its components.

What is a TBI engine?

Mopar Muscle magazine

The TBI engine is essentially any 2.2 or 2.5 with fuel injection but without a turbocharger (some exceptions were been made in Mexico). These engines were used on many cars, minivans, and light trucks. The computers and the engines underwent many changes as the years went on.

While turbocharged engines had multiple-port fuel injection (each cylinder had its own injector), the TBI models had only one, which is considerably less efficient - and that is one reason why the Neon 2.0 has 132 horsepower and 129 lb-ft of torque, while the 2.5 TBI engine had only 100 horsepower (albeit with 135 lb-ft of torque). David Zepeda tells us that the 2.5 liter engine in Mexico, where multiple-port injection was sometimes used instead of TBI, reached 110 hp, but gas mileage cannot be compared, and other adjustments may have been made to adapt it to high altitudes and lesser gas. We've heard since then that some turbo TBI engines were sold in Mexico in the 1980s.

Modfications to Chrysler/Dodge/Plymouth 2.2 and 2.5 liter TBI engines

There isn't much you can do (cheaply) to a TBI engine, and the following modifications may not affect your performance too much. The most common advice, "get a turbo!", is not always practical, though we have a comprehensive TBI-to-turbo conversion page.

The 2.2/2.5 TBI engines were competitive at the time they were made, for most of the models they were in (e.g. Sundance, Omni, Reliant). In the lighter cars (Omni, Reliant, Charger, etc.) with a five-speed, they could be quite quick; however, as Dan Stern points out, the automatic transmission's gearing did not help much. Again, even with an automatic, they were usually competitive in their price class, e.g. against the Cavalier, Escort, Tercel, and non-EX Civics (the EX added 25 horsepower and quite a bit of cash, taking the Civic out of EEK territory unless you were talking turbo-EEK). The 2.2 liter Reliant or Omni, with a five-speed, can keep up with most current economy cars.

These engines have nice low-end torque for four-cylinder models but are lacking in horsepower due mainly to poor breathing and fuel starvation. With good heads, MPI, and turbocharging to get air in there, the 2.2 was capable of high performance. (The 2.5, due to its long stroke, tended to be less racy in the high revs, but was quite satisfactory for most street use).

Dan Stern: Mexican parts

There are lots of interesting components and systems found on Mexican-spec 2.2 and 2.5 engines that we never saw here.  For example, all of the non-turbo AA-bodies got multi-port (rather than throttle body) injection, but some of the 2.5s lacked balance shafts.  Many of the engines had a very nice factory header system, and of course there's always the 8v 2.5 intercooled turbocharged engine used in the "regular" Spirit R/T and Phantom.

Edward Kelly:

I am not sure if there are any performance cams for the normally aspirated 2.2.

If you have some $$$ to spend you could have the head ported, 3-angle valve job, back cutting of the valves done, port matching of the manifolds. Back cutting the valves and 3-angle valve job will both help the head flow better especially at low valve lift... The valve guides are probably worn, you can have them replaced or spiraled to bring them back into tolerance...new valve guides will last longer. Spiralling is cheaper.

The porting is probably the most costly and also the most difficult to judge effectivness... That said, there are some simple things that can be done that will be improve the flow. This is especially true [if] you aren't looking for max performance, just improved performance.

Shaving the head to up the compression ratio would also increase hp. If you shave it too much you will need to run an oversized timing belt tensioner or an undersized belt (both sold by MP). You may also need to run higher octane fuel. If you decide you don't like the increase compression, you can get a copper shim gasket (Felpro makes one) to move the compression back to stock...

Degreeing the cam will also help...

Ted Raisor noted:

There is a long tube super competition header for 2.2 and2.5 equipped cars available from Hooker Headers. It only lists up to an 1988 but I know it also fits an 1989 daytona. Also I have a set of Eibach 1" drop springs on my Daytona but you have to buy them for a Dodge Spirit. And I've squeezed a little more top end power out of my TBI by cutting a hole in the hood slapping on a scoop, and using a Spectre intake tube to connect to the air box; all I had to do was make a tray and bracket and put some foam on it

Derek Beland wrote:

The problem with tweaking TBIs is that very few changes are individually noticeable. Most mods you can make will yield an increase in power that is a factor of the baseline power from the factory. Baseline power being rather low at 95-100hp, gains come in 2-5hp increases.

Some ideas are:
- advance ignition timing to 15 degrees
- play with cam timing via offset keys
- K&N drop in filter
- remove intake elbow
- remove heated air flap in airbox inlet
- hotter coil, wider plug gap
- cooler thermostat, remove coolant lines to TB
- bore out TB
- modify butterfly (shave shaft, shorten screws, knife edge leading side)

The expensive/time consuming stuff:
- ported head
- bigger valves
- convert to carbs
- shave head to raise compression

This assumes of course that your engine is in top running shape. A compression test might be wise, and potentially a ring-job. Beware that performing enough of these mods will run you lean. Get an air fuel meter to tune with, like any other motor!

There are differences between the later model TBIs and early ones. My stock fuel pressure is 39 psi for example, so I'm sure the injector is a different flow rate as well. My head has the "TS" stamp on it, which Gary's website says indicates a turbo head - but this one is definately the original. Perhaps flow is better. I know the intake manifolds for later models are slightly different. There was a TSB about hard starting that indicated the manifold could be switched to a later revision to cure the problem.

I don't want to upset anyone, but the automatic tranny TBIs are dogs. The previous owner of my 5-speed 92 car was given a loaner while they worked on it, and the loaner was identical in every way - except it was auto. "Couldn't get out of its own way" were his words.

Most people have to mod what they have. It doesn't stop the Honda guys though! They'll slap cold air intakes and headers on their cars to the point that if they summed up the total expense, I'm sure for a bit more they could have bought a turbo kit. I don't propose being that dumb, but I don't think it's unreasonable to think you can get another 20-30hp out of the motor, with a reasonable budget. My goal was only to be able to keep up with (hopefully a bit more than!) the 16V Cavalier & Sunfire class of cars on the road, not to make a track-dominating monster. :)

...

I like my MSD6A [ignition system]. Cars pulls to redline at a steady speed, vs running out of steam at the higher RPMs. Lots of other people say they do nothing (particularly the turbo crowd). I have my car setup so that I can bypass the MSD and run straight to the coil, and there is a small but noticable difference. Is it worth the $200 price tag? Dunno, that's a subjective thing I guess. BTW, you need to mate it with a Blaster 2 coil.

Lots of people say they've had problems with the MSD breaking down. I had one Blaster coil die on me, an interior connection snapped off. Because my coil is mounted on the thermostat and thus subject to a lot of vibration, I switched to the "High Vibration" version (filled solid with resin) and haven't had a problem since. I've had the MSD setup in the car going on five years now, 3.5 on the new coil. I mounted the MSD with rubber isolators, so maybe these people were screwing them down solid to the frames/fenders and they got shaken to death?

Timothy Pindell wrote:

I took my Daytona to the Nats for a few passes. My reaction times were abysmal, but the car is now capable of mid 17s with a good reation time. Here's what I did to mine for "race" day:

  1. MP camshaft P4529320 252/252 duration, 36 overlap, 108 centerline, (uses factory .430 lift)
  2. Cam installed "straight up" with the help of the offset keys
  3. Accell super coil, .05 gap on the Champions
  4. ignition timing set to 15 advance
  5. fuel pressure raised to 15.5 psi (it idles like crap, not sure if it's cam or fuel pressure related but it is lopey and sounds cool)
  6. removed rear seat, spare, jack
  7. 2 gallons fuel
  8. removed AC and PS belts
  9. rear tires to 55 psi, fronts to 35
  10. removed air filter, left the box
  11. Dynomax muffler/ 2.25 exhaust from the manifold/ no cat (it's rather loud with a straight-pipe edge to it)

I shifted at 6200! (indicated) rpm. Yep, it was still pulling, but not much.

This illustrates my belief that you can't get much out of a TBI unless you go lots more radical. It's got a bit more than what it had when it left the factory, but not as much as the tubo guys get for the same effort. Don't teach a TBI to go real fast. It wastes your time, and annoys the engine. (But it's fun to experiment =] )

Summary of low-buck approach

David Reynolds wrote: "the best performance you can get from a 2.2L n/a car is to be had by (in order of expense):

  • advancing ignition timing to 14-15 degrees (free)
  • K&N drop-in filter ($35)
  • 2.25" exhaust (around $100)
  • raise compression *a little* by shaving the head and/or block ($$$)

I have done all of this to my Sundance, and I have very good drivability for a 2.2L n/a. I am also using a Comp Cams camshaft, but I'm not convinced it makes a big difference over the stock cam. For an '87 or earlier slider cam, though, you may want to consider switching to an '88 or later roller cam. Switching cams is actually a fairly easy thing to do yourself, and you can usually get a used one pretty cheap.

Note that the changes I made to my Sundance require 93+ octane and raised fuel pressure to keep it from knocking. I raised the fuel pressure by squeezing the regulator in a vise (a la Gus) a little at a time, then testing to see if the knocking improved.

All of this taken together has given me a strong power band between about 2000-3400 rpm, which is great for my city driving to and from work. It has next to no top end, though.

2.2 / 2.5 TBI breathing

Exhaust

Dan Stern wrote: A Magnaflow (similar to an Ultra-Flo) muffler and low-restriction catalyst perceptibly helped.

Herb DaSilva wrote: "Smooth out the exhaust - there are several ultra-high flow cats on the market - go 2-1/4 all the way back to a turbo-flow muffler."

Bradley Miller suggested: "Daytona/Laser mufflers will fit our cars. (HINT!) Stock pipe is 1 7/8". Lambros Race Engineering has an adjustable fuel pressure regulator that will allow for fixing lean conditions. They also have different gear ratios (provided you don't mind losing top end) and they have different pulleys. This will spin the accessories a little slower to reduce parasitic horsepower losses." He later wrote: I just got my exhaust on Friday. It really helped with the sound of the car and the mid-range pull. I've now got 2 1/4" pipe all the way back to a Walker Super Turbo muffler. You can step down on the accelerator and really get a good shove in the pants without the car downshifting. In the upper RPM bands it doesn't really help too much.

tucumano1@aol.com suggested using an exhaust wrap, to keep heat in the pipes and maintain exhaust gas velocity. He also suggested using a TBI spacer of at least an inch to help out the low end.

Derek Beland wrote:

I have the Super Turbo on my 92 Daytona 2.5L NA (TBI). Sounds really nice. I lost some grunt on the low end, but the high end is slightly improved. I had Midas fabricate a 2" pipe (stock is 1 7/8") pipe from the cat back into the muffler, which is 2 1/4" in/out. It's significantly louder, but not annoyingly so. Make sure the install is good and the tailpipe exits past the bumper (it'll need a bend to do it, a pipe straight out from the muffler would hit the rear bumper). Mine is too short, and above 3000rpm I get a booming resonance inside the cabin. My stock exhaust was leaking in about three places, so I took advantage of that and replaced it with a performance exhaust.

The installer talked me out of putting a bigger pipe on -- I'm glad he did. I wouldn't want to lose any more torque than I did (cause then it'd be a Honda).

Click here for muffler replacement instructions, tips, and stories

Jerry Adams warned:

I have used K&N oil-wetted gauze air filter on several vehicles - some carbed and some injected. They do flow more freely than paper. However, their usefulness stops there in my experience. When I inspected each one before I installed it, I wondered at the light I could see through holes in the gauze! Every one of the intakes got very dirty downstream from the filter. Partly due to oil that was carried by the air and caught on the side of the intake or carb and partly due to dirt that got through the K&N filter.

So I went looking for a substitute that would flow freely and be very efficient at stopping the abrasive particles. I found several oiled foam air filters - HKS Super Mega Flow, Amsoil, Finer Filter, Dura-Blue and Accel. I reviewed the available test data which showed K&N flows more air and more dirt than paper - as I suspected. It also showed the oil foam flows more air than paper and almost equal to K&N - except K&N's data showed their filter best. One test [for motorcycles] suggested using K&N only for road racers and use oiled foam for dusty conditions.

If you drag race, K&N is probably okay, but I will not use them on the street again. If money is no object, you could use the K&N with the K&N Pre-Cleaner - a oiled foam cover for the cylindrical K&Ns. It seems even K&N knows their filter needs help so they sell it!

[Webmaster note: the test results Jerry referred to were made on motorcycle magazines, which may or may not affect their applicability. There is a lot of controversy over the K&N filters.]

Bradley Miller wrote:

    Before you get your injectors (uh . . injector for TBI), check to see what you are actually getting first. Everyone is concerned about airflow and going lean on the 3.0L engines and I have yet to see anything near too lean with my modifications. I suspect you'll find the same with the soda straw limitations of the TBI intake...

    Rule number one is, don't add more fuel till you need it. Ask any of the turbo guys and you'll realize that bigger injectors is the first purchase that bites you on the butt with a stock computer and boost level. Tricking your computer for more fuel flow without any work to the head or the TBI itself would be in that category. Typically most hotrod computers for other brand-x cars actually lean the mixture out. The same would hold true here I imagine -- but find out for yourself and document the changes. I did all the bolt-ons I could within reason on my Duster and didn't see any neglible improvements. Going from 100 to 110 hp in a 2900 lb. car . . . well you get the picture.

Intake manifold

Dan Stern said there was an updated intake manifold to solve the long crank time on cold starting. Joe Pfeiffer also suggested replacing the intake. Vincent Cheng described reworking the intake manifold:

Use a high speed hand grinder and smooth out the plenum and runners. Round off all sharp turns. Rounding off the edges and enlarging and smoothing the inside contours of the runners can add breathing efficiency without any notable sacrifice in other area. (From "Performance with Economy" by David Vizard).

Air filters and related stuff

Dave wrote:

Keep the filter clean: on my Sundance, all air goes into a 2 inch square section of filter, which gets filthy quickly, while the rest of the filter stays clean! IMHO, the K&N, by itself, does little to improve performance. It is cleanable and pays for itself in replacement air filters if, like me, you are conscientious about replacing those things.

Bradley Miller said:

  • Between the headlight and the battery there will be a little plastic "bucket" that's supposed to keep snow/debris from going up the intake hose to the air cleaner. Pull this off. Smooth pipe from the airbox to the air duct by the battery will also help. Do not remove the hose. This hose pulls air across the drive transistors for the injector. Without this hose, you WILL burn out the transistors. [Note: one EEK! member took off the hose but added a fan to blow air onto the transistors. Others, including Gus McMahon, have been running for years without it, and suggested that the airflow was probably only needed in desert areas or during extreme heat. Jeff Chojnacki wrote that he has been doing without computer cooling since 1989.]

    Cut a hole (about 3" dia.) in back of air box. This is supposed to give you a little bit more low end torque. Make sure to put a mesh up there to keep large objects out of the air box. OR - Change the airbox altogether. (Webmaster's warning: cutting the hole in the back of the air box will delay warming, especially in cold weather, because it bypasses the stove. The best way to do this would be to have a control, like a manual choke, where you can shut it off or turn it on from inside the car; if you like electrical stuff you might even be able to fit a solenoid in there somehow. I do not suggest cutting the straight hole for most people who live in "normal" climates. Those who are in very hot climates, e.g. South America, may be able to get away with it more easily. A cold engine has lower fuel economy and power, higher emissions, and shorter life).

Using cone filters on cars that K&N doesn't make cone filters for

Webmaster note: Though this is a common performance practice, bypassing the standard airbox may result in longer warm-up times, especially during cold weather, because when the engine is not yet at operating temperature it "recycles" heat by taking air from around the engine itself, rather than from the outside. This really does make a dramatic difference in warm-up times (you can find out for yourself by disabling the switch!). In addition, EEKs cool the computer using the air going into the engine; some have hooked up small 12V fans to blow at the computer instead (standard computer fans work). This is really a modification for those with high-performance engines (e.g. Turbo III/IV) or those who have already done other modifications to increase power and airflow.

Paul Smith:

The hose from the back valve cover to the Air Box pulls air into the engine, where it is sucked in by the pcv valve. It would be wise to filter this intake air along with the main air intake.

On the K&N filter. I went to Auto Zone, looked in the catalog, found a filter size I liked and ordered it. Mine clamps onto the throttle body with a hose clamp. The one I ordered was actually for my turbo inlet, but same principle. K & N makes all sizes of "cone" filter to clamp onto a pipe or nipple or throttle body. You can get them 2" long, 2" dia, to clamp onto a 3/4" pipe, all the way up to 6" dia. 8" long and bigger. The have filters to clamp onto 2" pipe, 2.25" pipe, 2.375" pipe, 2.5 pipe etc. etc., with lots of sizes for each pipe size. I picked the RU 0640. It fits on a 2.25 inch pipe, and is 4.5" dia, 5.5" long. $36.00 You could also get 5.5" dia, 7" long, $39.00, or the 4.5" dia, by 4.5" long for $32.00. What I am saying (in a real rambling drug out way) Is that they could get like 20 different size cone filters just for the 2.25" pipe, with lots of choices for EVERY size pipe you could want. Just measure the dia. of what you want to clamp it to, and buy the biggest one that will fit. They order it, and you have in two or three days.

Mark Housley wrote:

I just cut the intake hose close to the end (around the ribs where the filter clamps on) and made my own little adapter to use with the 5.0L cone filter. Paul Berkebile did the same. It was his idea.

Another take on this process

Andrew Dodd wrote about Matt Karl's ram air mod, posted on Matt's web site.

You'll need the following from Home Depot or a similar store - Prices in $US

  • 3" aluminum heater ducting - $5.49 or $5.99 for an 8-foot length. (8 feet is its maximum length - it starts out much shorter, and you can expand it as needed.)
  • 3" pipe coupler
  • 2 3" worm clamps (aka hose clamps)
  • 1 4" worm clamp

Remove the stock air hose from your airbox/intake - pretty easy, it's not on there very tight.

Snake the heating duct downwards through the space between the radiator hose/electrical wire and the transmission housing. It's a tight fit - Getting at your tranny dipstick will be a bitch after this mod. Once you have a bit, stretch it out and route it to the fascia, right between the two holes. If you don't have enough, stick more down. :)

Stick the 3" coupler into the end of the ducting. You'll want it relatively far in (but not all the way.

Open the 4" clamp all the way, and thread it through the holes. Use it to fasten the coupler/duct assembly there. MAKE SURE that the clamp is ON the ducting, if it's just on the coupler, it WILL fall out. (Trust me, been there, done that. :) Tighten it down, keep on feeling the assembly for sturdiness. It'll be a bit squashed and oblong by the time you're done.

Use one of the 3" clamps, install it around the ducting/coupler just behind the 4" clamp. (Just around the coupler/duct for this one...) - It's probably unnecessary, but I have it on anyway just in case.

Stretch the uppper portion of the pipe to the airbox, and clamp it to the airbox using the last 3" clamp. You'll have to tighten it down a lot - the airbox only has a 2.5" inlet.

You might want to use RTV to seal everything, too. I haven't yet, I will do that when I mod my airbox.

This mod doesn't reach its full capabilities without a K&N filter. I haven't noticed too much difference except at highway speeds. (Around 70 MPH is where I start noticing a big difference - This number will probably decrease a lot once I put in a K&N and mod the airbox, I believe what's happening is that at around 70, the airbox just isn't able to leak any more of the excess air, so it FINALLY starts getting forced into the engine. :)

Andrew clarified:

Jury is out as to whether this helps on the Spirit ES with the air dam on the front bumper - It may be preventing air from getting to the intake. I still can't tell for sure whether I've had improvements, other than the highway, and even then highway driving at those speeds is so rare when I'm at school that I can't be sure. People without the airdam/foglight assembly (less blockage) have had good success. (Shadows, non-ES Spirits).

Also, 4" to 3" reducers to replace the coupler are bad news. They reduce ground clearance just enough to get ripped off easily. Basically, using a 4" to 3" reducer (with the large side facing towards the front) adds a half inch radius to the whole thing AND results in the forward lip of the reducer being about an inch or so farther forward than when using a straight coupler with the front lip even with the front part of the fascia. It's JUST enough to make it very easy to rip the reducer off going over large bumps. (Whereas with Matt's intake as described, you just have to be careful about curbs when parking).

Matt seems to have found a stiffer coupler than what most of the other EEKers have been using. The ones we've used are thin aluminum and distort easily.

Martin Rempel wrote:

Before my turbo van I had a 89 Spirit TBI. One of the things I did was pick up a throttle body (TB) off of a wrecked car and had it bored out. There is not a whole lot of material to bore out. There are two very small vacuum ports that are in the bowl area. These tend to open up as you bore it out. I had a larger throttle plate made and had the TB on the car for a while. It made some difference but not much. I still have the bored out bottom half of the TB if you want it. The throttle plate I made was not quite big enough so my idle went up about 2-300 rpm. According to Gary Donovan, the major problem is the intake. Check out his site for more insight. He recently completed the TBI database. www.thedodgegarage.com

Ignition

The general consensus is that the stock ignition system works well enough for most purposes - unless you really hot-rod the engine, which as you noticed we do not recommend (given the effectiveness of a turbo-swap).

Mike King wrote that overgapping the spark plugs to .040", rather than the stock .035", helped in power. This had also come up in the EEK mailing list several years ago. The consensus was that Chrysler tended to be conservative in plug gap - other makers have larger gaps. Mike said that the power boost was stronger when coupled with midgrade gas. Note that this increases the strain on the ignition system, but that others have reported no problems.

Transmissions

Dan Stern wrote: Most of the TBI cars came with a final-drive ratio of 2.78. This is great for cruising at 75 mph all day, but around-town the engine is working below its torque peak and straining against the low-stall torque converter together with the high final drive ratio. This is also why early Slant-6/auto Darts feel peppy, while later cars feel "mushy" and slow --the early A-bodies have 3.23 or 2.93 gearing, while the later cars have 2.76s (and even later cars got 2.45s and 2.26s!). There was also a 3.22 ratio available for this A413 3 speed auto used with the 2.2 and 2.5 engines.

Sensors and stuff

Some advise a lower-temperature thermostat (e.g. 180 degree) - this is fine if you want to pollute more and lower your gas mileage, but is not really a sensible way to run your car. The engine was designed to have a certain amount of heat, and preventing it from warming up fully in order to keep the mixture rich is not the sort of thing we'd expect from Mopar folk.

Bradley Miller wrote: I was concerned that I might be running into a lean condition, the car gets a bad "soft spot" in 2nd and 3rd gear with a load. I haven't tried this yet, but they suggested a "poor man's lean/rich" sensor. There is generally three or four wires from the O2 sensor on the exhaust manifold/pipe. One of these will be either 5 or 12 volts positive. One or two will be ground and one will be the sensor lead. Take a voltmeter (DVM, not an old analog) and probe to find the correct wire. They said to connect the DVM and monitor the thing at idle with the + lead of the DVM hooked to the sensor wire and the - to ground. You want the setting to be in hundredths of a volt (if your DVM isn't autoranging). The thing should bounce around on voltage readings at idle. (Make sure you've warmed up the car for a little while.) By hooking the thing up inside the car, (tap into the wires and run into passenger compartment) you can monitor the conditions of the fuel/air mixture. Lambros stated the voltage should be form .88 to .94 volts during acceleration (load). Any lower than this is going to be lean, and any greater is going to be rich. Now, I don't know for sure if these numbers apply to all cars. Their number is 314-725-7181. They will be more than happy to help you. These voltage numbers should apply to TBI normally aspirated cars. This test will also show if your O2 sensor is working properly.

Fuel injection

Herb DaSilva: "If you start to get lean, get in touch with some of the companies that specialize in fuel injectors and get an 8% or 10% oversize injector. The stock computer will be able to handle it." (This is if you make other power modifications which cause the stock injector to be unable to handle the load.)

Conversion to multiple port fuel injection is generally considered more trouble than swapping in a turbo engine.

Bradley_W._Miller wrote: "we have the little blue bottle. (NOS) The ultimate equalizer. A system runs under $400, depending on where you get it. An extra 50-75 hp is about the safe limits, with stock parts. You just have to be careful to keep adequate fuel pressure and not to use it at too low of an RPM. Dropping 2 seconds off your ET with one of these is no problem."

Manifolds

Stefan Mullikan wrote: Pierce Manifolds sells the side draft Weber kits [that fit the 2.2 and 2.5 engines[ as well as the manifolds for our 2.2/2.5 motors.

The complete side draft Weber kit from Pierce is: $823.20

The side draft Weber manifolds, it's $293.24

They can be reached at:

Pierce Manifolds
321 Kishmura Dr.
Gilroy, CA 95020
1-800-874-3728

Camshafts and balance shafts

Taking out the balance shafts from the 2.5 engine is said to provide a very small power gain at the expense of smooth idling.

Gus Thomas wrote: The rumor of increased performance from disconnecting the balance shafts in the 2.5 engine is the result of a tech article by a Chrysler engineer a few years ago. It was re-written by Gary Donovan last year, and put in the SDAC newsletter. He said that 14 HP is gained at 6,000 rpm. How long are you at 6,000 rpm? For less than 1/10 of one percent of your engine's life? You're sure not gonna feel that 14 HP much!

Because frictional losses increase as the square of the increase of rpm, at 3,000 rpm (a real-world everyday rpm) you only gain 3.74 hp (the square root of 14). That's difficult to feel in the seat of your pants. I do it anyway (remove them) because I get slightly better gas mileage, don't whip up the oil as much, and get a little edge when I am at 6,000 rpm at the track. When you're heading into the 11s with a 2,770 lb Acclaim, you need every bit of free help.

[Dan Stern wrote, "there isn't much to be gained and quite a bit to be lost in the way of livable engine operation" - a statement which Gus essentially agreed with.]

Herb DaSilva suggested that 2.5 owners get a Mopar Performance cam and getting underdrive pulleys from LRE (Lambros) or others.

Bradley W. Miller wrote:

  1. A Purple cam shaft for the 2.2 TBI will work on the 2.5s. There are two different numbers, one for automatics and one for 5 speeds. Lambros does porting and other head work. Lambrose is real good to work with.

    New cam would improve bottom end with top horsepower about the same ([according to] Forward Motion).

    Here's the price and part numbers of the camshafts - P4529321 - Manual $89.25 (List $119) P4529319 - Automatic $89.25 (List $119) (1996 figures)

    Here's the bio from Forward Motion: RPM Range 2800-5800 (2500-5500 on automatic). Best choice for those looking for more midrange and top end horsepower. Really likes a ported cylinder head but it will work well on stock. Excellent Nitrous Oxide camshaft with Stage. 2 head. We have run 13.80's @ 107 mph with this piece.

    Note that those prices are probably about the same that you can get it through a local Dodge dealer by whipping out your Shelby Dodge club card. About a 25% discount on parts.

John Basol wrote:

  1. Competition Cams has a cam for the 2.2L the has 260 degree duration and a .460" lift. produces a power band of 1200-5000 rpm. That's what I need, the best of both worlds. The slightly higher lift to improve low end torque without the loss of high end power, and the slightly longer duration to increase high end horsepower without sacrificing low end torque. With a power band that wide I'll be smoking turbos not only off the line, but even after I shift it will drop right back into the powerband. Cost of the wondrous wand of steel: only $128. I don't think miracles come much cheaper than that!

    I do believe the cam that I found will also work in a 2.5, provided it isn't a turbo. Our stock cams are the same (part no. and all). As for why the factory did not use this type: all of the cams they have designed have been for race use. In drag and track the long duration short lift provides the power in the high rpm range. In rally racing the cams that they have designed for that purpose provide the torque required. They apparently didn't see a market for modified street use. The cam I found being both high lift and longer duration will require me to use the heavier springs from Mopar. This is due to the "lumpiness" of the cam. It should however maintain the correct idle for the motor. Competition Cams' part number for this particular cam is 22-123-4. They can be reached at 1-800-238-0341. Direct from Comp. Cams it runs $128.73.

  2. High Energy
    Powerband: 1200-5000 RPM 22-123-4
    Powerband: 1500-5200 RPM 22-127-4
    Magnum
    Powerband: 1800-5500 RPM 22-131-4
    Turbo
    Powerband: 3000-6000 RPM 22-124-4

Dale W. Kentoph wrote about 2.5 TBI performance upgrades, and his progress on his own 1988 Dodge Daytona:

I purchased a spare cylinder head and ported it myself. The only problem was, I didn't do a valve job on it, and it had sticky valves. Thus I ran the stock head for the summer.

I installed a Comp Cams cam, part number 22-127-4. This was total experimentation, as this was one stage up from the one John Basol wrote about, and I wasn't sure it would work with the stock computer. I had to advance the timing a bunch (by ear), but it works pretty well. The power band is 1500 to 5200, and it dowsn't have the torque of the Mopar cam I had before, but the power stays about the same clear past 5000.

I had the head shaved .015, added a K&N air filter, a high output coil, and a mildly over-rich fuel injector.

It really runs up through the revs easily. As an extra benefit, my mileage improved by about 2 mpg.

I almost forgot, I had two and a quarter inch pipe installed, along with a turbo muffler. The bigger exhaust actually quieted it at the low and medium rpms.

I found that the service manager at the Hibbing Chrysler Center, located about 30 miles from me, knows a lot about 4 cylinder performance. He told me a lot of interesting things. He says that .020 is about the limit on head milling gor running street gas. He also said that a Shelby computer limits the total advance to 38 degrees instead of almost 50 for the stock computer.

This winter I will get a valve job done to my ported head. Next spring I plan on trying to get a set of headers on it too, and hopefully a Shelby distributor.

Many people have had success with simply advancing their cam timing, which can raise gas mileage and power. Click here for instructions.

Match porting

Vincent Cheng wrote:

  1. Use 80 grit sanding rolls for this job. First start by applying dye to the intake gasket surface of the head. Fit studs into the head to help position the intake gasket during the next step. Carefully slip the intake manifold gasket over the studs and against the head so it most nearly matches the intake ports of the head. Working carefully so the gasket isn't moved, scribe a line around each intake port, following the inside diameter the gasket hole. Do the same on the intake manifold. Use bolts to locate the gasket in place. Remove gasket and set it aside.

    Next, with a carbide cutter, grind away the intake port and manifold to match the lines scribed on the mating surfaces. Dip the cutter in beeswax or kerosene to prevent clogging. Blend the new contour into the intake port about one to two inches. Then, you can streamline the valve guide boss, don't remove much material from the guide for fear of weakening it. Remove just enough metal to blend the guide into the port walls.

    After that, with a carbide cutter, carefully and slowly taper the port so that the surface is smooth where the valve seat and the port meet. As you smooth the passage, be very careful not to nick the valve seating surface. The object here is not to remove a lot of material but to eliminate any ridge between the head and seat. Blend and smooth the rough cut into the port wall. Don't take off a lot of material here: Grinding excessively may actually reduce flow! Then, surface the port using the sanding rolls. Don't try for a mirror polish, since a slightly rough finish will be best compromise between flow and fuel atomization.

    Repeat the procedure for each exhaust port, being careful not to enlarge the exhaust port more than the size of the exhaust manifold. Lastly, finish the exhaust port surface with fine paper (220 to 300 grit). A mirror polish in the exhaust port is desirable because it reduces carbon buildup. This is from the Toyota Performance Handbook by Pat Barden. 

TBI to Turbo

Maurice Barrett wrote:

I would stick with the stock rods, less reciprocating mass, better throttle response. Early T1's and 2.2 TBI both used light weight rods and I don't see why you would need anything else if you are not going to push more than 200hp.

(Responding to the question of using forged or cast pistons) Neat little trick I heard from a turbo dodge friend, was on 88 Tall Deck TBI 2.5L's you can use early flat top 2.2 pistons. This would kill two birds with one stone, higher compression, beefier first ring land.

(On using Weber side-draft induction)

Totally agree, or you could even go fuel injected and run a turbo intake and batch fire all 4 injectors off a TBI computer (Check out the page on Dereks site). Just as long as you ditch the TBI or carb manifold (heard carb manifold flows better than TBI, but I doubt it compares to side drafts or a 1 piece turbo intake).

(On a $3,000 cost estimate)

You can probably cut some off that 3000 predicted total and still build a engine the right way. The engine you are describing sounds like overkill in some aspects for a NA engine

The great thing about Chrysler is they like to use parts which are usually never pushed their potential in stock form. Find the right combination of parts and you can build a nice little engine.

Timothy Prindell wrote back:

I totally agree regarding the point on increased throttle response and recip mass. Here's my logic behind me and the later rods: It's not the power output I'm worried about, it's the RPM needed to make it. The NA engine is going to need to turn some rather serious RPM to get to 200hp. This RPM increases piston speeds and the need for increased strength to stop and start that piston. The late turbo floater rods wiegh 40g more than the early T1 rods and only 8 more grams per each than the early carbed rods (5203384). I guess it depends on the individual comfort level. If I had the heavier rods on-hand, I'd probably use them if I weren't going to build a turbo motor.

(On the cost): I agree. Some of it is overkill. Some machine work isn't exactly required, but I make sure I at least get the block, crank, rods and head checked and cleaned up. That adds up quick. I overbuild my shortblocks and suggest that to other enthusiasts. The rest can be easily modified later without pulling the engine. Build a great platform, and it doesn't matter what I do later. I know it'll handle it. Don't skimp on the machine work tho. That can bite you later.

Some suspension notes

Stefan P. Mullikin wrote this guide to Shelby Daytona springs and EEK / Daytona suspensions in general:

The front Koni's have 5 (?) adjustment settings and are accessible from the top with a small screw driver. The rear unfortunately are only adjustable by compressing the strut and turning the housing. Generally I find that you don't need to adjust them very much as the middle setting seems pretty good all around. For track days and the like, just adjust them up while you're performing the typical routine maintenance one would do before hitting the track (checking for loose items, broken wiring, leaks, bleeding brakes, changing oil, etc)

You can probably "fix" the height difference front to rear with some spacers on the rear springs. Not ideal, but easier than adding jack screws to the rear perches (similar to NASCAR racers since their spring setup is similar to ours as its separate from the shock)

The Shadows, Daytonas, Lebarons, Lancers, etc share their suspension with the K-car so they can all use the same struts, springs, sway bars, cross members, etc. So the spring's measurements should be similar. The differences being free length and wire diameter (which determines height and stiffness) If you search the archives you'll might find the actual rates of the Eibach spring kits. I do know that the Shadow kit has a higher rate spring (280lb/in on the front if I remember correctly) Not sure of the free length difference between the two of them.

Independent rear suspension for the K-car would be plausible, but the gains would be unknown as the real issue is really with the front. Horrible camber curves, binding sway bars and control arm bushings, bump steer, lots of soft rubber to eliminate any hope of maintaining what little geometry you have, etc. The later model k-members help alleviate some of that, but it's still a strut front end and it will always have that as its main Achilles heal.

The best things you can do is to eliminate the bump steer with rack spacers. Reduce the sway bar's binding by either running a Quickor end link bar (better but not perfect) or running a custom unit that is mounted to the front core support. The idea is that the sway bar is only active during chassis roll, not during bounce or rebound (i.e. it would be nice to be able to move the control arms by hand with or without the sway bar attached)

Once the above has been done, the car won't pull much more lateral grip than before, but it will be much more repeatable. So when you turn into a corner, you should be able to the set the wheel into position and assuming you're driving relatively well you shouldn't move the wheel until you exit. Stock, you typically have to adjust the wheel a little while the suspension compresses. This makes predicting how quickly you can go through some corners difficult because they may have bumps in them that upset the suspension (and therefore the driver, heh).

On the rear the issues are typical trailing arm/solid axle issues. It's very similar to the rear suspension under a NASCAR vehicle only we don't have power transmitting through it so that eliminates that issue (at least its not as bad as a stock Mustang rear suspension) Specifically the change in wheel base as the suspension moves up and down among others. Chrysler also adds a neat element where the rear locating bar moves the suspension laterally as the trailing arm moves up and down. Sort of a rear steer solution only it works when you compress enough of the stock soft rubber bushings and flexible rear arm to make a noticeable difference. Since it's also a solid axle setup the standard solid axle solutions apply quite nicely. Watts linkage, mumford links, etc. Specifically look at some of the solutions that the Lotus Super Seven clone builders are implementing.

If you have your heart set on independent rear suspension, I'd look at a De Dion solution (modified solid axle setup, used on some Alfa Romeo's, etc.) that would probably be a little easier to implement since it shouldn't take up much more room than the stock rear axle solution. Next up would be to troll the local U-Pull-it type yards with a tape measure and find a suitable candidate. A completely removable sub frame would be easier to work with (Miatas and 2nd gen RX-7s come to mind) along with similar rear track and control arm length to the front suspension would help keep both ends working together. Though Bill Cultitta mentioned that the Stratus rear suspension would be a good solution since it's a little beefier than the Neon pieces and it should be 5x100.

Stefan Mullikin's 2.2 - 2.5 equipped car upgrades

If you feel like doing some manual labor, you can bolt in the turbocharged 2.2 or 2.5 liter motor found in the later K-based Chrysler cars.

Find yourself a rusted out Daytona turbo car and pillage it for its stiffer suspension (larger swaybars, quicker ratio steering, and 4 wheel disc brakes) Grab the turbocharged drivetrain, wiring, fuel tank (buy a new pump and fuel lines though) and swap it all into place.

Now the wiring will be tricky, but you should be able to find a later TBI-equipped K-car to grab the wiring harness from which can be combined with the Daytona harness, etc.

To further the cheap and relatively easy suspension modifications, you can use the '90 and later cast aluminum control arms, K-member and uprights to greatly improve the suspension geometry of the car. If you really want to make a difference, build some spacers for the steering rack to decrease the bump steer (as the suspension moves, the steering angle will change slightly, kind of annoying) Buy a strut tower brace (fwdperformance.com) or modify a 240SX (Silvia) front bar to work on the K-car. This will increase the turn in response of the car immeasurably. The rear control arm from a later Daytona/Shadow/Lebaron performance model will have rear discs and a larger sway bar. John Spiva has Polyurethane suspension bushings for both the front and rear suspension (polybushings.com)

For wheels, whatever you can find will work. I think 16's are about the max I'd run on my cars but then I don't want to spend $2000 on wheels and tires for a $600 car. I've seen people running Daytonas with 17x8's and they look positively mean. So I bought some 15x7" American Racing Spyder rims off Ebay and shod them with 205/60 15 Yokohama's. When those wear out I'll probably put some 225/50 Kumho's on it. Luckily the bolt pattern of our cars matches with many other FWD cars. If you've got 4-lug wheels its 4x100, if you've got 5-lug wheels it 5x100. Heck if you want to use the larger 5x114 that the Mitsu use, you can swap to later model minivan hubs.

Neons are a great source of wheels as they came with either 4 or 5 lug depending on the option package/year.

As far as the engine goes: You can upgrade to the turbocharged drivetrain, just make sure you nab everything under the hood from the donor car as it's a system. Of course the modifications for the turbo motors are well documented on Gary Donovan's website as well as many other sites. Now, for the stock drivetrain, ditch the stock carb and emissions system. You can replace the carb with a Weber 32/36 DFEV (bolts on with some finagling of the throttle arm) You only need the one or two vacuum lines to run the car, the rest is just excess and my Rampage 2.2 passes emissions testing just fine this way. You can still find headers for the carbureted 2.2's which really help. Just make sure to use a long flex coupler and increase the pipe diameter of the system to at least 2-1/4" all the way back. IF you want to have some fun, pick up a side draft weber setup from Pierce Manifolds and freak some people out :) There was also a dual downdraft carb intake sold through Mopar Performance that used two stock carbs or two Weber 32/36 carbs. Also, Mopar Performance sold a supercharger kit for the early 2.2's which could raise the output to 150hp, which is about the same as a standard turbo motor with just much better throttle response.

Dynomax Street Systems

The setup is available for these Mopars (cost is about $100 plus shipping, except for the Neon, which is about $150). Make sure they throw in a reducer (part 35253) for your convenience (not available or needed on Neons).

The street system, according to people who have installed it, gives a nicer tone - not too loud, but deeper and more mellow. It looks like stock unit, and comes with mounts, clamps, and a tailpipe. It is not a catback system.

  • Part 17488:
    • 84-86 Laser 2.2 & 2.5
    • 84-91 Daytona 2.2 & 2.5, including Shelby, ES, IROC
    • 86-89 Lancer/LeBaron GTS 2.2 & 2.5, including Pacifica]
    • 87-94 Shadow/Sundance 2.2 & 2.5
  • 95-98 Neon 2.0

Part 17488 includes the over-axle pipe, muffler, and tailpipe; the extension pipe, which on turbo cars (and some V6 models) is part of the catalytic converter, remains stock.

According to Benjamin Hook, since Dynomax only offers the rear section of the exhaust, a Dynasty and an Acclaim would interchange, if a system was available. However, Dynomax part 43262 (over-axle pipe) will fit any EEK, except minivans. "It orients the muffler straight out the rear of the car, instead of towards the left rear corner like on AA and K bodies, giving a better performance look." Bejamin said he has used this pipe with good results on Spirits, Daytonas, Omnis, Sundances and Reliants.

Mike Holler’s mods and repair tips

Mike Holler, known on Allpar forums as mpgmike, also contributes to mpgResearch.com. He has contributed many columns to Allpar:
Interiors Budget interior restoration: making the inside of your car look like new again
Red carpet treatment: Installing new carpet in an old car
Headliner repair
Porting Porting heads for performance: step by step
Head porting example, part 1 | part 2
Intake manifold porting
Exhaust manifold porting (turbo)
Poly Quad heads: porting revisited

Turbochargers Turbochargers - all you need to know (interview)
Turbocharging the slant six for power and economy • Revisiting the turbocharged slant six
Budget turbocharger rebuilding (and Turbo Rebirth)
Installing a boost gauge

Other Powder-coating for a brilliant, durable finish
Custom pistons: roll your own!
Prepping valves for performance: grinding and polishing
Old cars: an opinion
Discuss Mike’s articles! (if you are not registered for the forums, register first )

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