High comp pistons

[LOUDSHO92]

250 Wheel HP + 8% gain with compression, TADA! 300+ Crank

Yep, never back anything up huh?

Maybe I missed Phoenix's original numbers so I do not know where he is at.

The link given below only talks about a 5% gain for the 2ratio gain in compression. Basically looking for something backing up the gains in compression.

Yes on something you haven't. I am just looking for something to back this up as I am curious to the gains from compression. I do not know as much about it so just looking for more info. Is that too much to ask?

I was talking to SinisterSHO, and I said it to back up what you said up there. I think you got confused or something.

Yeah I got confused.

 

[AREA 91]

Well most of you guys already know my sho setup.

Now im seriously looking into hi comp pistons , but im asking myself some questions , like what gains I might get from it.

Its either pistons , or a re-ring job (puffs blue @ 8k)

Anyone here has any working shos with high comp pistons?

Oh and please let go the blower , I aint going that route.

As a general rule, every full point increase in compression yealds a 3% increase in power.

 

[illSHOyou]

Maybe I missed Phoenix's original numbers so I do not know where he is at.

The link given below only talks about a 5% gain for the 2ratio gain in compression. Basically looking for something backing up the gains in compression.

Yes on something you haven't. I am just looking for something to back this up as I am curious to the gains from compression. I do not know as much about it so just looking for more info. Is that too much to ask?

"Ive seen illSHOyou throw around alot of numbers with not much backing it up"

I really didn't appreciate the "backing it up" statement. Sorry if I took it the wrong way.

The usually estimate is 4% increased power per 1 point compression.

So a rough estimate of 2 points, a 8% increase, should yield almost 20hp above a fully loaded 3.2L SHO engine. This is a guess though...

 

[SeanMc]

Your greatest qualities are showing.

You give me a lot to work with.

 

[Phoenix]

Thanks guys , and no I havnt put it on the dyno yet. Ive been telling me to go to the dyno for more then a year , and still havnt done it. I should kick myself now.

 

[SinisterSHO]

255 whp is not hard to achieve

 

[LOUDSHO92]

You give me a lot to work with.

I would appreciate it if you would stop.

255 whp is not hard to achieve

Yeah but I don't know if I have seen anyone pull 270whp N/A.

 

[SHODWN]

Should I scan my dyno sheet for you?

 

[Bob Gervais]

Should I scan my dyno sheet for you?

No, because technically, he didn't SEE it. (footnote: always leave a loophole for idiocy.)

 

[SinisterSHO]

I would appreciate it if you would stop.



Yeah but I don't know if I have seen anyone pull 270whp N/A.

thats becaues there isn't many high comp motors

 

[AREA 91]

Should I scan my dyno sheet for you?

I'd like to see it. It would be nice to compare it to mine. I KNOW you make more power than me, you just keep it to yourself.

 

[LOUDSHO92]

Should I scan my dyno sheet for you?

Sure I would love to see it. I always wondered what that SHO was running.

 

[St Louis SHO]

You people do understand that 12.5:1 compression is like WAY out of the realm of pump gas right?

 

[ST 2 SHO]

You people do understand that 12.5:1 compression is like WAY out of the realm of pump gas right?
__________________

I may be the best here to make a comment on Hi comp N/A power plants. After years of running a Type A1 WV at 15.75 to 1 and a Ford Focus at 12 to 1 with stg 2 Ford cams and a SVT intake and header system. The focus never lived up to the money that had been invested in it. BUT it did run a std. 94 octane fuel.
The Type 1A VW was running on AV-Gas 100 with a Knock System and a O-ringed block. This set up ran every well due to the fuel being used.
You may find yourself with the main problem that comes from HI-comp Pistons....... That is a timing system that retireds itself due to compression firing of the cheap fuel.
Can it be done... sure... well it work well off 94 pump gas ???? Most likely not well without a retired timing killing any gains that you may have gotten running a lower comp ratio or better fuel..........
just my 2 cents.
Thanks Avery


Can you say O-ringed block with a knock system.... ?????? = 94 unleaded

 

[St Louis SHO]

And who here will spend the money to do it? Do you realize this is a $1500 car?

:facepalm:

 

[zak]

St. Louis injects sanity into this discussion.

It has been years since I ran the calculations, but you can add about 0.2 compression ratio by milling the heads to the maximum limit. This will retard cam timing a tad.

You can also add about 0.3 points by cheater stroking the engine, which is far less expensive than a set of pistons.

Finally, static compression ratios are sort of a meaningless number as the dynamic compression will dictate what the engine octane requirement will be. You can run additional static compression on pump gas as long as you increase the cam duration and overlap, effectively keeping dynamic compression the same while raising VE. HC emissions will rise.

Just some thoughts - zak

 

[ST 2 SHO]

It has been years since I ran the calculations, but you can add about 0.2 compression ratio by milling the heads to the maximum limit. This will retard cam timing a tad.

I wasn't going to get into all the nickel and dimes of it....LOL

1) find a dished piston with a 11 to 1 or better comp ratio.
2) Cut the piston down .... remove some of the dish...( remove to a safe limit )
3) Install crank / rods / pistons in block.
4) Find thickness of head gasket compressed.
5) Mill block down so the piston is above the block BUT 3/4 the distance of the compressed head gasket
6) measure the distance of the steel ring on the head gasket ( block side )
Add 2ths and bore size to this measurement. Cut grove in block for .010 wire centered to bore aligning the rings of the head gasket to the bore groves
7) Mill head to max. ( Remove to a safe limit )
8) Install adjustable cam gears ( you will need them to bring Valve timing back within spec.

Finding someone to o-ring a block maybe hard ....... Its a OLD-SCHOOL Trick
but can be done with over head cam power plants just as it was done in the day.
Boost guys !!!!! You'll be hard pressed to blow a head gasket using this block trick......

 

[sho_sc]

Finally, static compression ratios are sort of a meaningless number as the dynamic compression will dictate what the engine octane requirement will be. You can run additional static compression on pump gas as long as you increase the cam duration and overlap, effectively keeping dynamic compression the same while raising VE. HC emissions will rise.

Correct! My Hayabusa is running a static compression ratio of a calculated 13.4:1 ... makes it's best power on pump gas using the 89 octane flavor. Some tall cams I have ......

 

[illSHOyou]

St. Louis injects sanity into this discussion.

It has been years since I ran the calculations, but you can add about 0.2 compression ratio by milling the heads to the maximum limit. This will retard cam timing a tad.

You can also add about 0.3 points by cheater stroking the engine, which is far less expensive than a set of pistons.

Finally, static compression ratios are sort of a meaningless number as the dynamic compression will dictate what the engine octane requirement will be. You can run additional static compression on pump gas as long as you increase the cam duration and overlap, effectively keeping dynamic compression the same while raising VE. HC emissions will rise.

Just some thoughts - zak

Well said, you beat me to it.

This trick could yeild stock power to 6,500 rpm by bleeding off compression and then continue making power on the high end towards 8,000 rpm. The intake after 6,500 rpm will start to starve the engine of needed air and keep from having too high cylinder pressure to need higher octane fuel, but at the same time still have above stock cylinder pressure in this region.