Custom designed JE 81.5mm 10.8:1 ITR Pistons for boost...
Eagle Rods
GEM Block
FJO Wideband
AEM EMS
EGT
etc.
etc.

All pistons melted @ the lowest point of the dome on the intake side... Cylinder walls were slightly scratched but just needed to be honed a bit to clean it up.
I was at about 11:1 because the block was slightly decked. Tuning is key, but with a daily driver I wouldn't recommend going my route. Safer is better (lower comp), especially if your car isn't a trailer queen... Having more room for error will save you some money. If you are into drag and not autox or rr, then go with a slightly lower comp. Any tuner will tell you that you get bigger hp & torque #'s with lower comp. Basing your turbo sizing for what the car is gonna be used for will help negate the extra lag from the lower comp. I was once a big fan of high comp/turbo, because it was the best of both worlds. It is, but tuning is very difficult and I would do it if I were to build a car specifically for the track and wasn't gonna drive the car daily through traffic and 100 degree weather.

First time I read about using NA pistons for boost. I know JE makes NA, Turbo and Nitrous pistons and I figure you would order the correct piston design for your application. I know that there are advantages in the rollerwave pistons (Wiseco Piston). I don't think that they distinguish between FI, NA, and Nitrous applications, like JE does.

I think that high comp/turbo is a good idea but is a ***** to tune.... 10:1 (stock GSR/prelude) is the highest i would go on a street car, to give yourself a tuning curve. It's your car and your decision. I learned the hard way from my mistakes..




[Modified by 00ITR #543, 10:40 PM 12/9/2002]

 

Looks like you ran a little lean there buddy. Needed to increase the fuel or your improve the fuel delivery. What kind of Intercooler were you running? You would have noticed a temp. spike with that Egt. Maybe you had a slight boost spike. Was that EMS controlling your boost or was it vacuum controlled? That wasn't caused by high compression looks more like a tuning error possibly a hick-up in the AEM unit. They are a little too new for me to trust one still, sorry. I build all my own electronics and test them quite harshly with a simulator and circuit tester before we run it on a safe engine.(safe as in won't go BOOM if it messes up) I'm sure they did this, but those boxes are mass produced; a few bad ones are bound to get past inspection. Sorry never had that happen before.

 

Greddy type 24 ic. Possibly boost spike. Ran a Profec B and it held boost perfectly. A/f on the wideband read good at all times (11.6-8:1). Though I didn't log 100% of the time (daily driven). EGT's were a little on the high side at times and that is what probably did it in. Like I said it was daily driven.. It was definelty tuning which is the issue with high compression, because you are tuning and running on pump gas... Which you do have to worry about with low cr also. My point is that lower compression would have given a bit more of a learning curve. Not everyone does what you say you do with electronics. You seem to be more on a professional level, which many of us aren't. This was my first experience with 11:1 compression and boost. I learned that there was not much room for error. Also with lower compression you have a bigger tuning window, where you can actually squeeze more power out. Meaning that the timing and a/f can be manipulated to yeild higher numbers. With high compression you can do the same, but you can only run so much timing because of detonation and you can only dump so much fuel until you get to the point that you are not adding hp because your running way too rich.

 

When I hit that tuning wall I'll be switching to straight Methanol. Then the real fun begins. I'll turn it into a track only car then.

 

how the hell do you do this when you might be running 15psi or so like I will be...Won't you spin like there is no tomorrow ?

 

I was doing 12 psi and on street tires I would spin all the way to 4th gear....

 

Tzsir I would love to see dyno charts, pics of your setup and your ride.
Also I notice you live in Wisconsin and was wondering if you ever ran your
setup at Great Lakes Dragway?

I personally have a 9.5:1 turbo setup and plan to run 14-16 pounds on stock sleeves and a soon-to-be EMS standalone.


AzianAvenger

 

i understand the ideas being stated about low C/R and high C/R turbo setups.
i was going to use my current motor with 11:1 C/R and install my turbo kit for the time being until i get $$ to resleeve a block for higher boost levels (as well as possibly overbore to 84mm with lower C/R pistons for easier tuning). and of course tune it very well with my Hondata 2B and my friend's laptop/wideband O2 sensor.

i was just kinda of weary of the whole high C/R + moderate boost on a daily basis.
if something would go wrong even for a second, it could mean starting over. also the pistons are SRP which seem to be a tiny bit less of quality than the JE's when i compared them, though they are the same company. my SRP's are coated by Swain Tech. and deburred of most sharp edges too so that could help resist detonation. i was thinking of 10.3-10.5:1 C/R when i redo the block, just for a more balanced block with a decent C/R but easier tuning.