question about raised compression

[t2000gts]

monkeywrench racing is selling a set of 4 wiseco pistons (along with rings/wrist pins/etc. for only $525 in any compression so i'm seriously considering buying some later this year...

my only question is what else would i have to do, to run a higher compression? i was thinking something like 12 to 12.5:1...something that i can preferably run on 93-94 octane.

do i just get a shop to install the pistons, and that's it? do i gotta mess with the ECU or anything?

[GTS LAID]

the big thing is before you even by the damn things you have to find a tuning shop... you have to be able to regulate the timing to reduce knock if it is to occur... which pretty much means some form of management... i'll have to look and see how the stock contributes to anti-knock and how much it varies the timing based on that... but it might even be enough coming to think of it.

[t2000gts]

Originally posted by GTS LAID
the big thing is before you even by the damn things you have to find a tuning shop... you have to be able to regulate the timing to reduce knock if it is to occur... which pretty much means some form of management... i'll have to look and see how the stock contributes to anti-knock and how much it varies the timing based on that... but it might even be enough coming to think of it.

yeah, that's why i didn't want something as high as the 13:1 of the TRD pistons...i was hoping only 12:1 would be safe for premium gas here in New York without need to alter the timing. even 12.5:1, since we can get 94 octane here as well...

is there any way to find out the minimum octane of gas required for a certain compression ratio?

[NSX_GTR_LM]

why dont you just run your gas really low ( like 2 bars) and go through in like 2 gallons of 89 or 87 and see how the engine reacts. I dont think it would hurt the engine if it was done for a short period of time, not to mention you could immediately fill back up with 94 after that.

[M SPEC]

Personally, I'd got for a 12.5:1 set for daily driving. I think at this point the TRD set is pushing your luck with detonation.

[t2000gts]

but would 94 octane be enough for 12.5:1 compression?

will i have to start ordering xylene by the barrel and stock up for the year?

[NSX_GTR_LM]

I think 94 would be safe for 13:1, but i think you should be ok with 12.5

[GulfCoastGTS]

Yeha I know a guy at a shop who can do pistons for really cheap. Anyways, Im trying to decide between low comp + forced induction or high comp all motor. What kind of gains will you see with 12:1, 12.5:1 and 13:1 compression vs. stock?

[autxr]

12:1 about 1 hp
12.5:1 about 3 hp
13:1 about 6 hp

Scott

[GulfCoastGTS]

Originally posted by autxr
12:1 about 1 hp
12.5:1 about 3 hp
13:1 about 6 hp

Scott

Are you serious??/ Thats it??? Then whats the point of spending all this money for 6 hp from the TRD pistons? Plus installation, thats alot for 6hp. you sure about those numbers?

I realize this isnt a z28, but in a catalog I say, a head gasket increased compression by 1/2 point on the 93-97 z28/trans-am and they get 10 hp from it. from 1/2 point. I just figured it would be more.

[EzRidA]

I'm pretty sure 12.5:1 will create more than 6hp. Something else that as an advantage is that a CAI, header, and exhaust will make more hp than they did on the 11.5:1 ratio. So in the end you'll probably up the HP a pretty significant number.

[Griffin]

Originally posted by EzRidA
I'm pretty sure 12.5:1 will create more than 6hp. Something else that as an advantage is that a CAI, header, and exhaust will make more hp than they did on the 11.5:1 ratio. So in the end you'll probably up the HP a pretty significant number.

Maybe not as much as you would think, at least not without running a serious number for your octane. Compression increase to HP increase is a law of diminishing returns. as you go up in ratio the gains for each increase get less and less. The REAL gains are made when you take a 9.0 NA can and bump it ro 9.5 or 10:1. Down at that end you make a significant difference. But when you start at 11.5:1 you don't have much room to work with. Your better off dropping compression and figuring a way to go FI.

Griffin

[autxr]

Thanks for replying for me Griffin!

Like he said, it isn't a linear scale. The higher the compression the greater the gain.

So that Camaro got a 10hp gain with a 0.5 percent bump in compression.

What percentage of power is that?

It is not a linear scale.

Are you serious??/ Thats it??? Then whats the point of spending all this money for 6 hp from the TRD pistons? Plus installation, thats alot for 6hp. you sure about those numbers?

Those are the numbers that my research indicates. For a 180 hp base, a bump to 13:1 from 11.5:1 doesn't even net 10hp. I wonder why all the people want to do it as well.

Scott

[Griffin]

Just double checked my chart. an 11:1 to 12:1 increase will net a 1.3% gain, and a 12:1 to 13:1 nets 1.2%. Mind you thats based on a purely mechanical formula and dynamic compression due to possible positive pressure created by the CAI could result in a minor improvement to that number. So lets be VERY generous and say 2%... thats a whopping 3.6 HP gain. There will be some "hidden" gains in fuel efficiency at low to mid throttle, but it probably won't help you total power significantly.

Now say for example your engine was 8:1 compression and you went to 14:1 compression - that would be a 8.7% power gain (again based on static compression). The fact that this is a PERCENTAGE based formula is what explains how a 300+ HP car could expect decent gains. after all - to hom 1% is 3 HP to you its 1.8.

Heres the Table you can use to calculate static compression based power gains: (the output is in percentages) The X axis will be Original compression, the Y axis will be New compression.

**.*:*|08.0:1|09.0:1|10.0:1|11.0:1|12.0:1|13.0:1|1 4.0:1
14.0:1|*8.7%|*6.7%|*5.0%|*3.5%|*2.2%|*1.0%|*0.0%
13.0:1|*7.6%|*5.6%|*3.9%|*2.4%|*1.2%|*0.0%
12.0:1|*6.5%|*4.5%|*2.8%|*1.3%|*0.0%
11.0:1|*5.2%|*3.2%|*1.5%|*0.0%
10.0:1|*3.7%|*1.7%|*0.0%
09.0:1|*2.0%|*0.0%
08.0:1|*0.0%

Hopefully this helps.

Griffin

[GTS LAID]

damn how long did that take you to type... or is it a copy and paste job? either way thanks.

[Griffin]

Originally posted by GTS LAID
damn how long did that take you to type... or is it a copy and paste job? either way thanks.

Had to type it by hand. And not too long. My typing may have a lot of typos to it, but the speed is reasonably fast. And yer welcome :)

Griffin

[GulfCoastGTS]

so why is everyone so worried about getting the TRD high compression pistons. Ill admit, horsepower is horsepower, but with the potential problems with our gas (if there are any), the $700 pricetag, and god knows what people will charge for installation, I think its a bit much for a few horsepower.

[Griffin]

Originally posted by GulfCoastGTS
so why is everyone so worried about getting the TRD high compression pistons. Ill admit, horsepower is horsepower, but with the potential problems with our gas (if there are any), the $700 pricetag, and god knows what people will charge for installation, I think its a bit much for a few horsepower.

Agreed - unless your building a hard core track car its probably not worth it.

Griffin