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3.2 direct injection pentastar


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62 replies to this topic

#41 redhed

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Posted May 13, 2011 at 11:10 pm

The 3.6 is an oversquare engine with a 96 mm bore x 83 mm stroke. If they were to destroke it, to achieve 3.2 would be somewhere around 73-74 mm stroke. Theoretically this would make a higher revving engine as it would have an even higher bore to stroke ratio.

I think a smaller bore of 90-91 mm would be what would be used if keeping the same stroke.(Still an oversquare setup) Or they could go to a square setup of 88 mm x 88mm.

Addendum:
I should say, I do not know if the head setup would allow for a smaller bore.


i was approaching my assertion from a factory tooling standpoint where it might be easier to de-stroke the motor than offer up different bores if the 3.6l and 3.2l engines are built on the same line. i'm kinda guessing at this...maybe bob can shed some light??

#42 Bob_Sheaves

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Posted May 14, 2011 at 06:33 am

Bob,
I have a question,
How does the effect of a fairly flat torque curve affect the BSFC, specifically in that flat area?

My guess would be a fairly higher BSFC flat curve in the area of the flat torque
and turning sharply at higher rpm's to meet a semi linear line of most engines.
Thus giving a fairly high BSFC during the majority of the flat peak torque = significant better fuel mileage at the low rpms?

The BSFC curve is roughly (VERY ROUGHLY) comparible to the torque curve, in the sense that a flat torque curve will roughly corrospond to a flat BSFC curve.

More info-

http://www.eng-tips....d=144109&page=9

http://autospeed.com...16/article.html (note where the red and green line cross in the Jaguar v12 chart-drop down a vertical line from that point and you will hit the lowest BSFC point, showing the least amount of fuel burned at that combination.)

http://en.wikipedia....uel_consumption A good basic article on calclating BSFC on Wiki

i was approaching my assertion from a factory tooling standpoint where it might be easier to de-stroke the motor than offer up different bores if the 3.6l and 3.2l engines are built on the same line. i'm kinda guessing at this...maybe bob can shed some light??

Duckie is a better one to answer that-he knows the tooling and what's available far better than I do. Sorry.

#43 MoparNorm

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Posted May 14, 2011 at 08:53 am

i was approaching my assertion from a factory tooling standpoint where it might be easier to de-stroke the motor than offer up different bores if the 3.6l and 3.2l engines are built on the same line. i'm kinda guessing at this...maybe bob can shed some light??


It depends upon how much they "de-stroke" the engine. Any change in the deck to combustion chamber ratio, creates issues.
Assuming that every micro-change affects emissions, and may inhibit a stroker engine, I'd still say an engine with a greater stroke to bore relationship, is a better performing engine.
Modern engines are over square because rpms help burn the fuel more completely and frankly because early V6 engines needed to be buzzy to move the vehicle.
The Pentastar (using a modified Hemi/Poly combustion chamber) overcomes this somewhat and produces more torque than any comparable sized Mopar V6.

When I build engines, I care little for horsepower, I concentrate on usable, low to mid range torque, the horsepower will follow. When you accelerate, what you feel is torque, not horsepower.
Engines with massive low rpm torque are fun to drive, get appreciably better fuel economy, but may not be emissions friendly, due to how clean today's engines have to be.
All that being said less bore and more stroke make a better performing engine.*
If you ever get a chance to look at the insides of a V-10 you are going to see relatively long stroke and small pistons, but a lot of them... ;)



* completely dependent upon your intended usage. The old 340 was a high rpm engine, with most of it's torque at high rpm, great for the Trans Am series, poor for a daily driver or truck, yet the same block in 360 form, was just the opposite, a good torque motor, a poor road racer.

Edited by MoparNorm, May 14, 2011 at 08:56 am.


#44 MoparNorm

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Posted May 14, 2011 at 09:33 am

i was approaching my assertion from a factory tooling standpoint where it might be easier to de-stroke the motor than offer up different bores if the 3.6l and 3.2l engines are built on the same line. i'm kinda guessing at this...maybe bob can shed some light??

I can now verify, its the same stroke, smaller bore.... :ph34r:

So,... it will be a higher torque to hp ratio. ;)

Using the same stroke means sharing connecting rods, crank, engine block deck height, etc. etc.

#45 drew54

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Posted May 14, 2011 at 09:41 am

I can now verify, its the same stroke, smaller bore.... :ph34r:

So,... it will be a higher torque to hp ratio. ;)

Using the same stroke means sharing connecting rods, crank, engine block deck height, etc. etc.


What other info can you bleed from your source?

DI? Multi Air?

#46 MoparNorm

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Posted May 14, 2011 at 09:58 am

What other info can you bleed from your source?

DI? Multi Air?

My sources are not bleedable... :lol:
Over the years, I've developed many, many contacts, many are friends and we stay that way by not pressing...especially now...and I'm often told more than I reveal, under a firm bond of trust and a desire to see Chrysler do well.
I can be disgruntled with Jeep, without being disloyal to Chrysler... B)

#47 drew54

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Posted May 14, 2011 at 10:10 am

My sources are not bleedable... :lol:
Over the years, I've developed many, many contacts, many are friends and we stay that way by not pressing...especially now...and I'm often told more than I reveal, under a firm bond of trust and a desire to see Chrysler do well.
I can be disgruntled with Jeep, without being disloyal to Chrysler... B)


Ok, probably not wise to bleed them, as they could run dry. Then we wouldn't have future speculation confirmations.

#48 redhed

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Posted May 14, 2011 at 02:45 pm

It depends upon how much they "de-stroke" the engine. Any change in the deck to combustion chamber ratio, creates issues.
Assuming that every micro-change affects emissions, and may inhibit a stroker engine, I'd still say an engine with a greater stroke to bore relationship, is a better performing engine.
Modern engines are over square because rpms help burn the fuel more completely and frankly because early V6 engines needed to be buzzy to move the vehicle.
The Pentastar (using a modified Hemi/Poly combustion chamber) overcomes this somewhat and produces more torque than any comparable sized Mopar V6.

When I build engines, I care little for horsepower, I concentrate on usable, low to mid range torque, the horsepower will follow. When you accelerate, what you feel is torque, not horsepower.
Engines with massive low rpm torque are fun to drive, get appreciably better fuel economy, but may not be emissions friendly, due to how clean today's engines have to be.
All that being said less bore and more stroke make a better performing engine.*
If you ever get a chance to look at the insides of a V-10 you are going to see relatively long stroke and small pistons, but a lot of them... ;)



* completely dependent upon your intended usage. The old 340 was a high rpm engine, with most of it's torque at high rpm, great for the Trans Am series, poor for a daily driver or truck, yet the same block in 360 form, was just the opposite, a good torque motor, a poor road racer.


yeah, i have noticed that most v6s today tend to be oversquare...except for honda's for some odd reason. i see your point about low end torque but it seems like today's 6,7,8 speed trannies are offsetting the low end torque deficit with some pretty short gearing, so even high strung engines seem pretty spry at low rpm these days... :-)

I can now verify, its the same stroke, smaller bore.... :ph34r:

So,... it will be a higher torque to hp ratio. ;)

Using the same stroke means sharing connecting rods, crank, engine block deck height, etc. etc.


thanks...that does make sense!

#49 The Mad Duck

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Posted May 14, 2011 at 05:34 pm

Having One "Hole" Size is a TON Easier to Do & Aids Productivity.

Having to Change Over All the Tooling - Rough Bore, Final Bore, Hone and Related Gages Can be Tedious and Time Consuming.

Then You Have to Get Every Thing on "Size".

Did I Mention there May Be the Scrapping of a Few Blocks May Be Involved.

After It's Done a Number of Times, Scrapped Blocks Dissipates to Almost "Zero".

If You Have to Ask the Price of a Mostly Machined Aluminum Iron Liner Block You Can't Afford One.

Looking Back Thru Some of My Old Paper Work the Total Costs Involved with a Finished 4.0L Alum. Block was About $358 a Copy.

TMD

Edited by The Mad Duck, May 14, 2011 at 11:04 pm.


#50 redhed

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Posted May 16, 2011 at 03:10 pm

thanks for the info...duckie!

#51 MoparNorm

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Posted May 16, 2011 at 04:26 pm

Having One "Hole" Size is a TON Easier to Do & Aids Productivity.

Having to Change Over All the Tooling - Rough Bore, Final Bore, Hone and Related Gages Can be Tedious and Time Consuming.


Just to clarify, as I do not see that I wrote about it, the displacement (bore size) is changed by the thickness of the cylinder liner.
Stroke, etc. stays the same. Piston and rings change, depending upon the liner diameter, to arrive at the various Pentastar displacements.

#52 ShadowRider

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Posted May 17, 2011 at 03:23 am

I can now verify, its the same stroke, smaller bore.... :ph34r:

So,... it will be a higher torque to hp ratio. ;)

Using the same stroke means sharing connecting rods, crank, engine block deck height, etc. etc.

Not so! The crank has 4-5 mm smaller diameter pins and mains and is much lighter which means different rods and possibly lower deck height for the block.

#53 AC TC

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Posted May 17, 2011 at 03:49 am

Bob Sheaves: "The most fuel efficient point is where the torque curve crosses the HP curve-this is the most efficient point for any engine,"

Is this really true?
And if so, how do you scale the axis for torque and hp (change scaling and or sort and the crossing point will move)
I have somewere learned that the optimum efficency is at the point of max torq.

One must also remember that these figures presented are full throttle runs and not
representative to everyday use, they dont say s..t about part load efficency.

#54 Bob_Sheaves

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Posted May 17, 2011 at 03:52 am

Bob Sheaves: "The most fuel efficient point is where the torque curve crosses the HP curve-this is the most efficient point for any engine,"

Is this really true?
And if so, how do you scale the axis for torque and hp (change scaling and or sort and the crossing point will move)
I have somewere learned that the optimum efficency is at the point of max torq.

One must also remember that these figures presented are full throttle runs and not
representative to everyday use, they dont say s..t about part load efficency.

SAE has the specs, which are too involved to go into here. Part load or full load makes no difference. Pounds of fuel per horsepower hour is not load dependent. That is why it is called BSFC. You need to go back and read that article with the Jaguar example - it explains the way BSFC works.

#55 AC TC

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Posted May 17, 2011 at 08:21 am

SAE has the specs, which are too involved to go into here. Part load or full load makes no difference. Pounds of fuel per horsepower hour is not load dependent. That is why it is called BSFC. You need to go back and read that article with the Jaguar example - it explains the way BSFC works.

Bob, you´r correct about BSFC but ive never seen a partload curve.
What im concerned with is that one might belive that the full load curve is the same as
part load curve, and i´ve never seen a manufacturer show anything but full pull....

#56 MoparNorm

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Posted May 17, 2011 at 09:01 am

Not so! The crank has 4-5 mm smaller diameter pins and mains and is much lighter which means different rods and possibly lower deck height for the block.

The rods could be interchangeable, I'm not saying they are. From an economic standpoint they could be, from a performance standpoint, they don't have to be.
The deck height appears to be the same.

#57 Dave

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Posted May 17, 2011 at 09:02 am

Moving back a bit, there is another consideration ... while we here may all agree that it's better to have a well balanced engine with good low end torque, the fact is that whenever an engine is produced, there's a SINGLE NUMBER the average dingleberries pay attention to -- peak horsepower. So that's a consideration because if you can't market an engine, it doesn't (economically) matter how good it is.

Brings back memories of the 2.5 TBIs... would you rather have the Dodge Shadow 100 hp / 129 lb-ft engine or the Honda Civic EX 125 hp/100 lb-ft engine? The answer is, that depends on whether you're racing down the flats or trying to go uphill with the a/c on...and have passengers.

#58 Bob_Sheaves

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Posted May 17, 2011 at 09:14 am

Bob, you´r correct about BSFC but ive never seen a partload curve.
What im concerned with is that one might belive that the full load curve is the same as
part load curve, and i´ve never seen a manufacturer show anything but full pull....

BSFC is the amount of fuel burned PER horsepower and ANY load. You take the hp generated times the BSFC to get the amount of fuel burned total. Part load or full load doesn't matter as the amount of fuel burned is related directly to the amount of horsepower generated. Just because an engine may be turning 4000 rpm at peak HP under full load, does not mean that the total fuel burn at 4000 rpm is always the same. As horsepower varies, the fuel burn varies. The engine does not always produce 290hp at 4000 rpm if the load is not there.

Now, that being said, the BSFC PER hp does vary with RPM, which is why a curve is generated and not a single point.

#59 CJDsalespro

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Posted May 17, 2011 at 09:21 am

I am still trying to figure out what the exact application would be for this 3.2? Would this be offered as a replacement to Wranglers 3.8 or used as an entry level V6 for Ram. or possibly a standard engine for 2012 Caravan. I would just hate to see it offered in the vehicles that already use the 3.6. Like the previous generation Sebring. It did not need 2 v6 options especially since 3.5 could hardly be deemed a performance V6.

I love that the new LX's start with 3.6s this year. I hate to see us cheapen them less than a year later by offering them with less potent engines. Can you guys that are in the know clarify this ?

#60 MoparNorm

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Posted May 17, 2011 at 10:20 am

I am still trying to figure out what the exact application would be for this 3.2? Would this be offered as a replacement to Wranglers 3.8 or used as an entry level V6 for Ram. or possibly a standard engine for 2012 Caravan. I would just hate to see it offered in the vehicles that already use the 3.6. Like the previous generation Sebring. It did not need 2 v6 options especially since 3.5 could hardly be deemed a performance V6.

I love that the new LX's start with 3.6s this year. I hate to see us cheapen them less than a year later by offering them with less potent engines. Can you guys that are in the know clarify this ?


It's actually the exact opposite. The 3.2 will be for smaller lighter performance models, not models that need low rpm torque, such as Wrangler and Ram.
I'm not sure you saw my earlier post comparing the 360 with the 340. The 340 was a "Performance" engine that delivered high rpm torque and horsepower, the 360 was the low rpm performing engine. The 340 was perfect for cars but terrible for trucks.
The same analogy can be given for the 3.6 vs the 3.2. The 3.2 will have things like VVT, MultiAir and be a higher horsepower engine for the new lighter CUSW vehicles, the 3.6 will be the workhorse.


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