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Turbo Build-Up - Mike Holler and Bob O'Neill discuss Chrysler turbochargers

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In this article I discuss a turbo engine build up with Bob O'Neill. He has some general goals for the build up. The following is what we talked about.

Mike, I understand that you customize cylinder heads for different applications. Let me start by telling you about my situation.

I recently purchased an '86 Dodge Daytona Turbo Z C/S. It's got all kinds of cools options like T-tops but those don't relate to my question so I'll leave them out. The car was available because of a blown engine. The lower end needs work and the head was cracked. I've located another head but it will need at least a valve job, so thought I'd have some custom porting done too. Doing some research for this on the and forums, I discovered you and your work. So here are my goals and some questions.

First, the engine is an 1986 Chrysler 2.2 T1 Turbo. This engine came with an ugly intake manifold and setup. I say ugly because I plan to show this car. I originally thought I would like to keep it totally original and to that end I'll hold on to all the '86 parts just in case I want to go back. But because the '86 intake is so ugly I thought I would install the newer style. From my research I have discovered that to do this several other things need to change as well. We can chat about those changes another time but I have some goals for this build and would like to ask you about them.

Q: Thinking about this conversion I wonder if there is any way to take it one step further. Is it possible to increase power from the stock 141hp and increase fuel economy?

A: Any modifications that will increase combustion efficiency will improve both power and economy. Improving volumetric efficiency alone will increase power, but won't necessarily improve economy. If anything, it could make it worse. The things I target to improve both power and economy can be categorized as:

  1. Better vaporize the fuel
  2. Better homogenize the fuel with the air
  3. Maintain optimum velocity throughout the ports
  4. Promote better flame propagation in the cylinder
  5. Enable more even pressure distribution across the top of the piston
  6. Better evacuate the cylinders to reduce intake charge dilution

The tools I use to accomplish these feats are Powre Lynz, Powre Ringz, port biasing, Edging (thanks dana44), Somender Grooves, ports sized to valve size and cam lift (called Curtain Area), combustion chamber reshaping, and various textures and shapes.

Q: That sounds great but my goals are still fairly modest. I know some folks may not agree with me but all I want from the power is somewhere between 180 and 200 HP on 87 octane fuel. Is this possible? If so, what would you recommend?

A: Since you aren't chasing the Holy Grail 300+ HP mark, the port size can remain conservative. Although larger than stock, the ports will still be smaller than the "killer" heads. Smaller sizes will keep the velocity high in the RPM range you will be running the engine. The Powre Lynz are like screw threads turned into the intake ports between the fuel source (injectors) and combustion chamber. By varying the pitch of these Lynz, specific velocity ranges can be targeted to optimize certain engine operating conditions. Compression is another factor. You can actually run a slightly higher CR than the "killer" heads because of the modest boost you've targeted and still live on 87 octane fuel.

In short, improving combustion efficiency means converting more of the chemical energy in the fuel to kinetic energy at the crankshaft. The BSFC number on your dyno sheet is the quantified scientific designation for this value. By improving the combustion efficiency, your 180-200 HP numbers are easier to achieve, and your 30+ mpg is more realistic.

Q: That sounds like it will make the head flow better, and with the breakthroughs you have made with Power Lynz and the Grooves it sounds like my goals for this car are possible. What other things would you suggest?

A: I will be taking great care to maximize the exhaust ports for optimal cylinder evacuation. A ported exhaust manifold would be a minimum requirement, while a custom manifold would be even better. Downstream of the turbo, exhaust restrictions will hurt you. A larger pipe with mandrel bends would be recommended; at least 2.5". Heating the fuel to about 110° F will help it to phase change from a liquid to a vapor easier as it passes through the injectors. This can be done with an engine coolant-heated heat exchanger. Hot air will promote better vaporization, but will also promote detonation under boost. A relatively new trick is called the "D-Valve", which is a sump pump (household basement) check valve rigged in between the turbo and throttle body with a "T". Under normal driving conditions, the engine draws from the D-Valve routed from behind the radiator drawing heated air. The moment you hit boost the check valve slams closed allowing the cold air system to reduce detonation tendencies. Ignition should be in top shape, as should the bottom end. Light weight oils suck up less parasitic losses while actually lubricating BETTER than the heavier oils on a tight engine (not so with one that has excessive clearances in the bearings). 5W-30 oil in the manual transmission will keep parasitic losses to a minimum also. (Recommended by retired Chrysler engineer and racing division developer Ed Peters.)

Q: What about the boost? Will I need to boost higher than stock?

A: Depends. If you are talking about the stock TI 7 psi, then yes. If you're talking about the TII LM's stock 12 psi, then no. You should be in the neighborhood of 190-200 HP with the above listed mods at only 10-12 psi boost.

Q: Ok, so if I want the best protection I should add an intercooler? Is this required or will the cool air from in front of the radiator work for me given my modest power gain requirements?

A: The experts recommend using an intercooler for anything over 10 psi boost. It would be recommended that you use an IC, especially considering your intent to use 87 octane fuel. What you might find is that to run 12 psi boost without the IC you'll need 89 octane fuel, or that you can only run 9 psi boost on the 87 octane juice. An electronic 2 setting boost controller would allow you to set the boost for a comfortable 7# for daily driving with 87 in the tank, then flip the switch to 12 when you have the more detonation resistant 92 octane fuel on board.

Q: Really, great. Since I only want to boost to a max of 12 psi and my goals for power are around 180, then are you saying that these goals can easily be reached with the port work you doing and only 12 psi?

A: First understand that registering boost indicates a pressure differential. To achieve a pressure differential, there must be a restriction. In the case of an engine, the manifolds and cylinder head ports represent the restriction. As the restriction is opened up (porting), the pressure differential becomes less with a given volume and flow of air. This is why ported heads are able to make more power at less "boost". Another consideration is as you compress the incoming air, you also heat it. By ingesting a given volume of air (and fuel) at a lower pressure, you are ingesting it at a lower temperature. This is good for power and good for detonation resistance. So after saying all that, the answer to your question is yes.

Q: It sounds like I may not need to boost all the way to 12psi to make the HP goals. What boost levels do you think will be necessary if I only want around 180hp yet stay with 87 octane? Or, is it even possible? I know this is speculation on my part but if I don't need to go to 12psi and an intercooler to make my goals wouldn't that be a good thing?

A: My recommendation is to start at 7 psi boost and gradually increase the boost until you get the "seat-of-the-pants" feel that you desire. You will either get detonation or that "this is fast enough" feeling. Then if you like, look at the boost gauge and see how much it required.

Q: Ok so if I do set a maximum of 12psi boost, how can I be sure that it will stop boosting when I reach 12psi? What are my choices?

A: If you chose the '86 GLHS or '87 TII LM, the answer is easy…let the factory system do its job. These LMs are set at 12# boost. If you chose an '87 TI LM, then the factory system will limit boost to 7psi. To raise the boost setting to the desired 12 psi you can either control it mechanically or electronically.

Mechanically, a "G-Valve" is a spring loaded check valve that will allow air to flow past only when the spring pressure has been exceeded. Set the spring pressure to 12 psi and when boost exceeds that, air pressure is diverted to the wastegate canister.

There are a myriad of electronic methods available. One is a Hobbs switch. It is a pressure switch that will close once the set pressure is reached. Rig it up to manifold pressure, set it to the desired 12 psi, connect it to your factory wastegate solenoid, and when it is activated your wastegate opens. There are also expensive aftermarket controllers, some of which have a pretty impressive list of bells and whistles. Most of the "Tuner" mags will have ads for several different versions. I'm currently working on a 2-setting electronic controller that works with the MAP sensor and activates the wastegate solenoid when a preset boost level is reached. It has a switch and 2 knobs so 2 different boost settings can be used.

As a side note, once flow through the manifolds and head is increased to a certain point, the factory wastegate on the factory turbos becomes inadequate and boost creep starts. The hole in the scroll for the wastegate bypass should be enlarged as much as possible, but still allow the wastegate to seal when closed. This gives the maximum amount of bypass to take into account the additional volume of gasses that will be passing through the exhaust.

Q: This sounds great. I've located an '87 T2 computer. With the mods you're doing to the head and with my modest goals, I can reach these goals with the stock computer and I won't need anything more to limit boost to 12 psi. I guess I'll need to get the hole for the wastegate opened. This should allow me to reach my goal of 180 HP.

What about fuel economy? Will there be anything we've discussed here that would lower fuel economy? I'm hoping to be able to get around 30mpg on the highway. What do you think?

A: Well, running the engine at 180 HP will drop fuel economy in a heart beat. As far as the modifications go, none of them, including the modest porting, will reduce fuel economy so long as the car is driven modestly. Like I said, we are targeting improved combustion efficiency and that will improve both performance and economy.

Thanks, Mike. It sounds like my goals can be met fairly easily but with some custom work. I really can't wait to get this project rolling. I know that as with all things I have to be flexible in my plans. But so far it sounds like you've put me on a good track. Thank you for your time. I look forward to working on this project and with your help I'm confident my goals can be met.

Also see our 2.2 turbo page.

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