I know that 8.5:1 CR would be the safest but I want as little turbo lag as possible. What factors are involved in making the best decision? I am leaning more towards 9.0:1

My goals are 600rwhp on 94octane with the APSTT kit.

 

The power gained from higher CR is not equal to that of which you can gain by having higher boost due to the lower CR.

(Just put a 75 shot of nitrous till the turbo's spool)

 

I think the poster was considered with off boost and part throttle response....and an increase in spool time. CR alone doesnt determine power...but is does have an effect on how that power and trq is delivered across the power band.

I went with 9.0:1 for these very reasons.....i am looking for a sub 600whp daily driver car, and felt that 9.0:1 was the best CR for me.

 

I am not choosing the 9.0:1 for power gain. I want to know if I can reach 600rwhp on 94octane because the higher CR I choose the least amount of HP i can run on pump gas.

 

Id say the 9.0:1 pistons would be on the high end of the spectrum with 94 pump. You would have to get cams, head work, good exhaust, and delete the cats for sure. With this you might as well get springs, retainers, and valves. You can also consider using a thermal coating on the head of the pistons and combustion chamber on the heads and maybe even the ports. This should net you 600 rwhp with excellent tunning.

Your 600 rwhp goal on pump was my same goal. I went with the off the shelf 8.6:1 Arias pistons.

 

I am not yet at this stage but when I get there I will be aiming for sub 600rwhp band as well and will be going with a compression ratio of something in the 9 range (assume detonation resistant dish design) with carefully matched ignition timing settings.

As the 350z is not a high rever I think its important to keep the spool times quick as possible as not to reduce the effective on boost rpm band.

 

If u want to run 17-19psi on pump gas then go with a C/R between 8.1 to 8.6 max. Im going with 8.5 C/R to run 16-17psi on pump gas later on.

 

I went with 9.5:1 pistons and the APPS kit. I also went with a set of JWT cams. Charles at CJ motorsports is tuning it right now and should have some results shortly.

Jeff

 

i went with 9.0:1 compression...is there an actual "max boost" that one can shoot for with this ...on 91 pump gas?
i was hoping to run 16-19psi...but really , whatever it takes to get to 550rwhp uncorrected!
also...believe it or not, i still have the stock cats in!...what should i go for (as far as straight pipes?) i dont want it to be too loud..should i even push toward hi-flo cats or is that a waste of time?

thanks
TODD

 

Jeff, we are picking up the block from the machine shop on Monday or Tuesday... hopefully by the end of the week the engine should be all together.

 

9.5:1 on the APSTT is very interesting. I look foreward to your numbers.

 

I'll like to see this when its done.

 

Rayden...love the sig pic man. SWEEET!