Alright guys, I thought I would start up a discussion on engine characteristics and how they affect our cars in particular instead of all the normal threads we have going about parts and stuff.

This thread will be about: Displacement

I know in our the 2001-2003 gen CL-S the compression ratio is rather high and this, I'm guessing, has a big factor with the amount of displacement our engines produce.

Question #1: If we could increase the displacement therby lowering the compression ratio, would that allow our cars to run a higher boost either from a turbo or sc, and therby increase the amount of power our engines output?

Question #2: Does increasing the displacement increase the amount of torque our engines are capable of laying down?

 

I am increasing my displacement via the 3.5 upgrade. This will lower us to around 10.14:1. However, with my plans so increase the blower's psi to near double the stock boost, I had the JE pistons custom forged to have the 3.5 yield a compression ratio of 9.0:1 which should eliminate detonation problems associated with that level of boost. On an increase in torque, the answer is yes. Just no definitive numbers yet.

 

1- yes

2- yes

 

Yea, i've heard of people dropping in the mdx engine to up the displacement, but doesn't the 3.5 motor weight more than our engine J32?

and if it does weight more isn't it possible to increase the displacement of our engine thereby keeping the same weight but increasing the displacement?

 

1 - Lowering the Compression ratio by changing out the piston is NOT going to increase displacement. Displacement is bore x stroke. Compression ratio has to do with the piston-top shape and the volume of the combustion chamber. If you change the bore of the piston, you will increase the displacement. If you increase the stroke and maintain the same piston-top shape and combustion chamber, you will increase compression and displacement (more air being compressed in the same TDC volume)

2 - Increasing the displacement with all-else equal has the 'potential' to increase torque and horsepower. Honestly better cams will give you just as much or more torque/horsepower than the currently available 3.5L conversion.
Now... if you add cams to the increased-displacement motor, you will take advantage of this extra 'potential' achieved by the increased displacement

Motor performance is not a direct correlation to displacement as the 1950-1980 American ideology of 'no replacement for displacement' or 'bigger is better'. However, torque is more directly correlating factor with increased displacement

Hope this clarifies things for you!

 

yea it does make perfect sense. Increasing the bore and stroke are the way to go because you are increasing your potential, and that opens the door to more mods like upgrading cams to utilize the increased potential.

I'm surprised someone hasn't tried doing this yet though. I'm sure our motor's can handle the power increase. I guess the only dilemna is finding a tranny for our car that can

 

There is a small misconception here:

• Increasing displacement does NOT necessarily decrease compression ratio. I'm guessing you're making the assumption that you're increasing displacement by increasing the stroke. It's also possible to increase displacement by increasing the bore, or the width of the cyllinder. Assuming you're referring to the former, whether or not that affects the compression depends on if you do anything to the crank. Compression is defined by the difference in cylinder volume between BDC (bottom-dead-center, when the piston is at the bottom of it's stroke) and TDC (top-dead-center, when the piston is at the top of it's stroke). It is theoretically possible to shorten the rod but change the crank, or even change the piston, giving you a longer stroke with the same compression ratio.
• By lowering compression, you reduce the risk of detonation, and yes, this will allow you to run higher boost
• Increasing the displacement increases the torque, but how the torque can be affected will vary by how you increase displacement (i.e, are you changing the bore or are you changing the stroke to get more displacement?) I'm sure there are empirically derived formulas for this that mechanical engineers will be able to expound upon more

 

I had 400+ at the crank at one time... and encountered no problems... motor/car can handle the power.

 

You are correct... I assumed identical bore - hence said nothing was changed in regards to the piston. In the 3.5L conversion currently available, bore remains the same (hence the assumption).

I didn't get into a lot of the emperical details because its endless. If you maintain the same combustion-chamber with a piston of bigger bore (yet same dome/squelch area), you don't decrease the compression.

Also the idea of how the increased displacement is achieved (like you mentioned) is critical in predicting/evaluating potential engine performance.

 

Possibly it is that you mistyped this though I thought I would offer a clarification in case accuracy is important to anyone needing this.

The displacement is specificaly: (pi/4)(Bore^2)(Stroke)

 

well you did but there is no way you can assure car wouldn't have had problems down the road.

 

titand's car seems to be fine though

 

Yup... I should have been more accurate - was trying to point out the fact that only bore & stroke are contributing factors - I stand corrected

 

I'm talking about after a year or so. Moreover, i'm talking about running the car at high boost, relatively speaking of course.

 

I didn't mean to impile that my lower compression pistons were the cause for an increase in displacement. I was wrong as I assumed that the bore was slightly increase in the MDX block, hence the increase in displacement. I stand corrected.

 

Have any of you guys considered increasing the bore and upgrading the pistons and rods to see what the gains would be on the J32 engine?

 

why bore when stroke is so much easier....the gains speak for themselves

 

how do you upgrade stroke?

 

3.5L shortblock increases stroke. mainly the crank i think.

 

very off topic and please let me know if there was any resolution to this

http://www.acura-cl.com/forums/showt...light=sly+dyno

I really want to see the dyno

 

yea i know, zapata reminded me about this in another thread, it had slipped my mind when i got busy with work. i dont have a scanner so as soon as i can get access to one i'll have it scanned!

 

you do realize that i have an '01 acura cl -S with a 3.5L engine? via a honda oddessey crank

 

i didn't know, that's why i'm asking. i started this discussion to help people that don't know about this learn somethin new about our cars. intakes headers exhaust, i know how all that crap works, but motor enhancements i could use some tips.

 

believe me dont take this the wrong way but most people here are well aware of the benefits of discplacement increases ...i've run 13.794 @101.54 headers ,intake,tires,stroker

http://www.acura-cl.com/forums/searc...der=descending

 

well like you said, most are aware, i was aware of it too, that's why i started this thread. i just wanted to look at all the different things people MAY have tried. that's all.

 

no prob...so far the only thing tried has been strokers