SR Build Questions

[sil80dude]

Im getting high crank case pressure and think my rings are starting too go. I didnt have the time to test it before i tookoff up north to find the exact problem. 1991 SIL80 sr20det 5spd>Stage4Clutch/Short throw/Intake/Gt2871rBBar.64>tub.Mani>3" alum.turbo back/electric cutout/ 550cc/4"Intercooler 2.5' CX Piping/Apexi.BoV/FPR>Watermeth>22PSI ROMTune

I want to do pistons and rods and another cosworth HG maybe some more headwork and cams.

I have a gt2871r ar.64 and i love it. I had upgraded the HG to the Cosworth 1.5mm metal. I noticed the car had more lag downlow and I bet the HD lowered the compression but I dont know how to figureout how much it would have.

My question is how do I figure out what my compression ratio would be with a 1.5mm HG and 10.0 or 11 comp pistons?

Im aware that the enjuku racing car had a SR20 11:5:1 compression with C16 fuel and a GT2871r


Im aware of the high comp/turbo arguements. I would rather run a little higher comp. with lower boost to get the response that you get from higher comp. motors and having the boost comeon quicker. I know some guys run 10.0 comp ratios and 20 psi on similar 2L setups aslong as you dump enough fuel and are able to pull timing uptop. Thanks

[oni jake]

My question is how do I figure out what my compression ratio would be with a 1.5mm HG and 10.0 or 11 comp pistons

This is really the only question I found in your post. I'm so confused, so much information, what exactly do you want? Suggestions on what to built?

To find the volume of a cylinder = (3.14)(Radius)2(Stroke(+/- HG thickness))

Or you could just plug all the information in on this site and it'll pop out an answer. Engine Size and Compression Calculator (http://hotrodworks.net/hotrodmath/engine.html)

[Davidna2fi]

Go 11.5:1 and take it to a shop that is known for tuning Honda engines, no joke, it seems that the shops that I have seen tune stock bottom end high compression S2K engines, K20s, and the ITR B18C5 engines have got it down to a science and know where to make adjustments to timing and fuel tables. Hopefully there is a good tuner in your area that is willing to try something different.

[sil80dude]

Wrote it fast. Better to have more info then less i guess. I want to raise the compression for a little better response downlow. 30psi on a t3 is cool and all but i like the response of a smaller turbo w/higher compression, much funner to drive around town IMO. I know that cylinder head pressure gets high with higher compression and the sr heads can lift easier then some other motors.

I want a higher then stock compression ratio and keep my 71r. With the thicker HG i was wondering was how higher compression pistons with the SR would even be a good idea as it seems not many people do this but lots of the honda guys do it. I think a end ratio of 11.0 to 1 on 15psi would be a really fun street setup and around 330whp but I didnt know that formula Oni Jack posted that will help me alot. Any thoughts on cylinder pressure at 7500 rpm at 11 5 to 1?

[oni jake]

Most people stay away from higher compression because it leads to reliability problems. Honda motors are not Nissan motors. Head flowrates, difference in materials, etc.

If you were to go the high compression route, think about getting into different fuels. E85, C16, etc. However, maintenance and upkeep is extremely costly for a street car. You'll see more of this stuff at local competition events.

Your goal is 330whp, so keep it simple and rebuild. From your mod list it seems all you need is a good set of camshafts and a retune.

[ultimateirving]

Most people stay away from higher compression because it leads to reliability problems. Honda motors are not Nissan motors. Head flowrates, difference in materials, etc.

If you were to go the high compression route, think about getting into different fuels. E85, C16, etc. However, maintenance and upkeep is extremely costly for a street car. You'll see more of this stuff at local competition events.

Your goal is 330whp, so keep it simple and rebuild. From your mod list it seems all you need is a good set of camshafts and a retune.

I too have wondered what it would be like to venture into Higher comp sr motors.. but the thing that stands out to me is these are designed to be high revving. so i dont really care about boost in the low rpm because the car will be redlining frequently. If drag racing is what you are into and you want low end response then by all means try something different

[oni jake]

I too have wondered what it would be like to venture into Higher comp sr motors.. but the thing that stands out to me is these are designed to be high revving. so i dont really care about boost in the low rpm because the car will be redlining frequently. If drag racing is what you are into and you want low end response then by all means try something different

For what end goals are you talking about here? As a general rule, low end torque precedes high rev when you're trailing a V8 in tandem.

[sil80dude]

Most people stay away from higher compression because it leads to reliability problems. Honda motors are not Nissan motors. Head flowrates, difference in materials, etc.

If you were to go the high compression route, think about getting into different fuels. E85, C16, etc. However, maintenance and upkeep is extremely costly for a street car. You'll see more of this stuff at local competition events.

Your goal is 330whp, so keep it simple and rebuild. From your mod list it seems all you need is a good set of camshafts and a retune.

Ive always used 94chevron, I want to build the car to be reliable as a fast street car with as little lag as possible. WHP goal of around 330 350 or higher in the future with a t3. I would rather overbuild them under and do it again a year later.

I think an end compression of 10 to 1 on a 2871r would be a really fun car to drive and at 15-20psi and on 94 should be safe for detonation. I want to build the engine aswell with supporting internals.

Tomei 256 Ponicams, BC springs, retainers and new guides/seals,
CP 11.0 87mm pistons, Eagle Rods, New Bearings, 1.8 MM Costworth HG, ARP Studs.

The reason i ask about the higher compression pistons is the jump goes from 9 to 11 their is no 10 to 1 option so its either 9 to 1 and a 1mm HG or 11 to 1 and a 1.8mm HG and build the engine so i can throw on a gt30 later on. I just bought a new garrett bb 71r and want to use it for a little while.

I want a responsive reliable 330 350whp car that will rev like a b18c.
the parts i have chosen i think will get me to this goal but im no expert and their are so many SR combos that i wanted some input.

Questions

Would i benifit from adjustable cam gears? I know these arnt some 270 pro cams so i dont think i will need them but with the higher compression i think it could help with timing and tuning

Would say a 9 or 10 to 1 compression SR lift the head at 8/9k rpm? Cyliner pressures have go to be stupid high. I know my gt2871r wont cut it but gt30 in the future is where i will probably go.

Thanks