High compression pistons

[smufguy]

I been sleeping on this for a long long long time. ANd here is the question out loud. What is the max hp (@what rpm) and max torque (@what rpm) would u get from a high compression piston? lets say 11.0:1 compression!!

PS: b20A is the same 2.oL right? where does the 160hp come from? what kinda comp dees it have? thanks guys

[Jims 86LXI HB]

Hmmmm, the B20 is 4 valves per cylinder vs our 3 valve's, that's part of the power gains. As much as I agree with the thought of bumping compression, man I was pinging on premium in the summer time on throttle tip in. Maybe it's from carbon build up and stuff, up I'd be worried about detonation with going higher with the compression. I'd go with 10.5, even then I'd be worried. Just my 2 cents.

BTW, I'm a bigger fan of a all motor build up of our engine vs a swap, so I'm with ya. I'd be happy with whatever gains could be had. If I needed more than that I'd buy another car, that's my 3 cents.;) :D

[A20A1]

You know what you need to do... retard... ignition. :D

[smufguy]

ur a sneaky bastard MIke. :D

Jim, me too man. I dont have the dreams of getting a B20, not anymore. Besides, i wanna go with a full motor build pretty soon in the future when i get the money and get my baby totally put together.

This is what i know from reading thru mods by individuals and reading about general stuff.

High comp pistons: pushes the highest hp above stock in number and rpm (ex. 120@5500rpm VS 160@6200)

THey also seem to push the torque gain, which is not that much. (122@3600 rpm VS 130@5000rpm)

The numbers are just for example and not exact. So is it true that it happens like that?

My other thig is going with a Turbo which boosts ur hp and boosts ur torque hugely and often does it in low rpm which is awsome for lowend pull.

So which do u guys think is worth the money? Also to note, I am not gonna be racing down the track or even racing every damn guy on the road trying to rule the road. :d. I jus want to squeeze the max out of the A20 puppy.

Thanks for the input Jim and u too MIke, good to know in the future.

PS: like ur pic mike :D

[Scorpion88LX]

if you want to have a turbo you don't want high compresion pistons just good forged piston. the two don't function well with each other.

[smufguy]

yeah ryan, its either higher comp pistons OR turbo.

[A20A1]

I vote High-comp.

[anchovies]

na all the way!!

[Site]

Originally posted by smufguy
yeah ryan, its either higher comp pistons OR turbo.

Kraftaroni has 10:1 pistons and turbo at 18 psi in his dune buggy. He runs water injection to avoid detonation. The high compression helps the turbo to spool faster, reducing turbo lag.

[pric]

Here's a link to your Comp. Ratio question

http://3geez.com/showthread.php?s=&threadid=5526

[1988starter]

dosen't work man

[Scorpion88LX]

yea but is it easy to get the engine cool enough to avoid detonation, if you can thats one thing but with the added boost it is easy to kill tje engine.

[pric]

3geez.com/showthread.php?s=&threadid=5526

This should work.

[89accordboi]

bah that doesnt work either
i think you need some:
:help: :help: :help: :help: :help: :help: :help: :help: :help: :help:

[Jims 86LXI HB]

:huh: well it works for me and I fixed the original one to:wave:

[smufguy]

dude pric, it does not answer my questions. I read that thread and have answered it but my question is WHAT HP AT WHAT RPM??? WHAT TORQUE AT WHAT RPM???? Read my question and what i am asking for!!

I know ppl who have got high comp pistions have not dynoed their car, but i wanna get a logical answer from u ppl who have worked around cars. It does not have to be 3g. but any car engine that u guys have upped the compression and have dynoed it. I wanna know how the hp and torque get pushed.

[Jims 86LXI HB]

Something to read while I see what I can find on the subject. I thought it was interesting.

http://www.motortecmag.com/archives/2001/jun/JUN01-01/JUN010101.html

[Jims 86LXI HB]

Hmm, something else on the subject. Is their a tie in between upping compresion ratio's and needing more radical cam duration's? I notied while looking at the crane cam site at B18a cams that the when you looked at more aggressive cams, that they required that you use higher compression pistons.

www.cranecams.com/import/hnonvteccams.htm

[POS carb]

The high compression helps the turbo to spool faster, reducing turbo lag.

Compression is largely responsible for torque output of the motor, and since turbo motors generally have low compression pistons, the feel would simulate that of less turbo lag. I dunno if this is correctornot, I'm just hypothsising here: You raise compression by reducing cylinder/combustion chamber volume for a given stroke so that would mean there is actually less exhaust volume which would technically cause more turbo lag

smufguy, I think going high compression is better for someone with a regular budget, turbo gets costly but definately worth it if you have the cash to do it right.

[smufguy]

Jim This is from the first link u gave me "Before arbitrarily deciding on the compression you want for your motor consider that what you might like for compression is actually irrelevant - it's what the motor wants that counts. Just how much can usefully be used depends on a variety of variables which will be detailed shortly. What is not commonly appreciated is how much power and torque can be sacrificed by not giving sufficient thought and attention to maximizing a motors CR."

I have no clue what that means, but my guess is that i gotta know what the max handling of the A20 before i choose the comp ratio rather that just pick one out of nowhere?

The wilder camshaft requiring a compression of 12:1 seems like WHOA. i have no clue why it is like that. I mean, the camshaft actually opens the intake ports and lets more gas in right? so u use higher compression to create more burst? Is that wilder cam just for naturally aspirated? cause if not, why should the turbo require u drastically down ur compression. For example from ur 9.3:1 to around 8:1?

my guess is that jim that Wilder cam is only for naturally aspirated motors right? or with nitros and not for any forced induction setups? Thats my guess on that.

Eric, its just my research man. I wanna get to know how everything works before i put my money and work into it. I know turbo is the solution, but also i wanna know what the higher compression does to ur motor? where and how it pushes the hp and torque to the max and at what rpm.

Thanks to everyone who have posted and also i am really appauled by what u guys say cause its teaching me somethin :D

[A20A1]

The wilder camshaft has more lift and normally more duration and overlap, so there is an increased chance of reversion, Who knows what that would do to the turbo or manifold's/head?

[pric]

dude pric, it does not answer my questions. I read that thread and have answered it but my question is WHAT HP AT WHAT RPM??? WHAT TORQUE AT WHAT RPM???? Read my question and what i am asking for!!

I answered your question. Read my post, It's linear across the entire RPM range. If you only increase the comp. ratio and leave everything else stock your peak output will still be at the same RPM.

EX. You increase your comp. from 9.0:1 to 10.0:1 it is an increase of 2.2% through out the entire RPM range of the stock output.

[smufguy]

Prick, this is the equation you gave me right?

power increase or decrease (%)=[(1-1/r(0.4 th power)divide 1-1/R(0.4 th power))-1]x100

So using R as 9.1 and r as 11.0 the % increase comes around 5.148%.

So that is saying that its 5.148% increase over the stock (98hp in my case cause of my A20A1).

if i am doing my math right the total HP after the high comp piston is put in. It equates to

5.148% of 98 = (5.148*98/100) = 5.045

So the hp u end up with is 98 + 5.045) = 103.045 hp

That is not worth the money. Its either the equation they came up with in the Mag is bullshit. cause i did it twice on my calcualtor and still end up getting the same damn answer. And like Injab said in the last post in the link u gave me prick, seems like the result is not worth it, IF WE USE THE EQUATION.

:werd:

[quagmire]

The thing with "wild" cams is high lift and long duration, and usually more overlap. In a naturally aspirated app, valve overlap acts to draw the air fuel mixture into the combustion chamber. As the exhaust gases leave the combustion chamber, there is a void left at a given piston position causing the intake charge to hurry in and replace the exhaust gases. With a turbo, overlap is undesireable because having the exhaust valve open as the overpressured intake charge enters causes a portion of said intake charge to blow out the exhaust valve. More lift and duration is fine with a turbo, even better if the cam has been design to be used with it.

As far as high compression, its generally felt that to make power with a turbo, low compression and large boost are better than high compression and low boost. The latter is okay for daily driver/ production car apps, because one can minimize turbo lag. On a small motor the former can be kind of a pig in traffic, due to the lack of low end torque available.

[pric]

Well you calculated correctly. However, I think you maybe missing the point. If you keep everything stock on the motor and only change the comp. that's the increase you get. Plus you are comparing a motor that only has 98hp not a whole lot to start with if you compared that to something like 400+hp then you got a nice increase. Now when you add the other variables into the equation like I/H/E, cam, P&P that increase will be greater. Not a huge increase but another way to squeeze out a few more horses out of the motor.

[quagmire]

Pric is exactly right. A powerfull motor is not about just a single element. It's about a motor with components matched to one another, the success of the head,cam and intake packages that Holley and Edelbrock make for domestics is evidence to this. So, to get good power, its not jsut about having a "wilder" cam on your stock motor or just increasing compression. Basically, I would probably pick the most feasable compression to run, then get the head worked on, then cam the motor properly.
As far as the compression you want to run at, you really need to watch for detonation, otherwise you'll have to use octane booster and/or retard timing, which isnt necesarily good for low end power if I remeber right.
Thats my two cents. Of course, after all this, if you've done forged pistons, then you can get silly with the nitrous. But thats another story...

[pric]

Here's the web site to the mag. I got the equation from.

www.dragsport.com/

The web site doesn't go into detail as much as the mag. does.

[smufguy]

hmmmmn...... nice. From all the stuff i have learnt today. finally came up to a decision. well i am gonna have a full exhaust put on soon and its gonna have an intake just like most of the guys here do. Those are preliminaries. one thing for sure is A20 is staying, nothing is gonna be done to it as in swapping it out. Once i have enough money i am gonna put a cam like most of u guys have and in like the future when i got like, lets say, $5000 i am gonna turbo it. Thats my verdict :D. Compared to all the addons and bolt ones and esp having a efi, i think going turbo is what i need.

Thanks a Lot to you prick, leaned a lot from u man. And thanks to everyone who posted here to give me your views and facts. Thanks for everything.

[Site]

Originally posted by quagmire
As far as high compression, its generally felt that to make power with a turbo, low compression and large boost are better than high compression and low boost. The latter is okay for daily driver/ production car apps, because one can minimize turbo lag. On a small motor the former can be kind of a pig in traffic, due to the lack of low end torque available.
For those who know, could a good balance of low end torque and moderate HP gains be reached by running a turbo with increased compression pistons?

Please don't simply reply with "you'll detonate for sure". There are work-arounds for reducing detonation risks.

[kraftaroni]

Yes. I put a drag turbo kit on a type R for my friend and did no internal modifications. With an apex afc and 10 psi his car did 330hp to the wheels and he has driven the car daily for about 16 months. As for detonation if you have the head off you can have your combustion chamber reshaped or do it yourself.you can also gain the compression by welding on the combustion chamber instead of getting pistons. this might be a better option. why? because if you buy pistons they are cut for a 16 valve motor and if there high compression often with a 12 valve you have piston to valve interference. I know this because I was a machineist for ross racing pistons and I made a couple of sets of pistons for my car. back to the head- If you reduce the quench area and take off all the sharp edges,polish chamber and c.c. head you will reduce the chances of detonation. I have 10:1 comp on my turbo aircooled vw engine and have no problem with detonation. I can run it on 91 up to about 8psi above that I use leaded race gas.