I know this may sound stupid to the motorheads but since i was gonna build my motor, i was thinking

if i put 8.5:1 CR pistons, and keep the boost at 8 lbs on my TN kit, i will lose power correct? Unless i boost higher.

So pretty much, with low compression pistons, you gotta boost higher to be around the same power as high compression pistons with lower boost? Is this correct? I'm not gettin high compression pistons anyways but i was just curious about this. its bothering me not knowing, ive been thinking about it all day and i just had to get this outta my head.


Please dont flame, i love you all.

 

oh and one more thing i wanted to add. If i go with 8.5 CR, will i have to get a retune. Im just running on the TN reflash. Will the flash still be good or do i need a tune now.

 

I'm the last guy that you would want to ask, but I'm assuming people will say that if you are spending the money to build a motor, you should no doubt be running something like the UTEC - since you are going to want to push more timing to get more power over the reflash, and your motor can handle it.

 

you are correct

 

I wouldn't run the stock reflash on any 350Z with the TN kit unless it had minor mods like exhaust only.

engine build doesnt fall under minor. you should get a Utec

 

well according to VTR, reflash is good unless you are going for more power and i kinda agree. reflash is fine till you want to push more, then there is more to consider.

i agree that engine build is not minor however, when i get a EMS, im going haltech. I just dont have the money yet cuz this build is already costing me big time. Im probably going to be running the reflash for a couple of months after the build.

Any concerns on this. about a running a reflash on a built low CR motor.

 

lol. ppl are not telling you wrong. why would you spend a grip on a bottom end build only to rely on a generic reflash to control your motor no matter how much boost you are running? good management is vital to engine longivity on a boost'd car that doesn't come boost'd from the factory. UTEC minimum....haltech or FCON VPRO preferred. More control = less risk.


if I were you I'd get the management you really want (haltech) now, have peace of mind now and you won't be buying this mod twice. Call it, cheap insurance for your built bottom end.

 

dropping to 8.5:1 CR will lose you about 20 tq/whp worth of power across the whole rpm band. Most people with FI won't really notice it much. You can increase your boost, but adding more boost won't really make a turbo spool up any sooner in the powerband (like below 2500 rpms) so you'll be trading low rpm power for more high rpm power with lower compression and more boost

IMO I wouldn't be touching 8.5:1 pistons unless you were shooting for at least 600whp. Otherwise I'd choose at least 9:1 for a turbo car

 

Just go with a utec, you can find them used for $600-700. Then resell it on here when you want to go Haltech. Sure it is some extra money but is much needed protection and I'm sure you will pick up 50+ hp when you can tune your new setup, rather then rely on a flash that is designed for a stock setup. I can promise you that spending money on the right parts (and this will be the "brain" of your whole system) will always cost you less in the long run!

 

+1

 

well thats what im shooting for. around 600whp. but thats when i go twins next summer. I just cant build the motor, get a ems and tune and go twins all at the same time. thats like almost 12 grand haha.

 

+1 for troof...

I personally like the custom pistons that Performance Factory/Titan Motorsports are producing at 8.8:1 CR. It sits right in the middle, but seriously I doubt you'd tell much of a real difference anyway.

I also agree that the reflash would not be acceptable on a lower compression motor. When you start modifying your setup past maybe an exhaust or plenum spacer, then you need a custom tune.

 

alright i guess ill go with a utec now and then get haltech when i go twins next summer.

 

If you kept the same tune, you'd lose power! BUT, you shouldn't keep the same tune. With low comp pistons and 8 psi of boost, you can safely run your motor with an A:F in the mid 12s and add more timing than you have now. ....and more timing and a leaner mixture will give you more power and better repsonse.

 

We have done this before... built 9:1 motor with turbonetics kit and reflash.

From what I understand the reflashes are hit or miss - in this situation it was a 'hit'. We wanted to make sure it would run fine so we broke the motor in and then proceeded to strap it down on the dyno and verify that timing and AFR were safe. FYI, it made within a couple whp of what a stock motor turbonetics kit makes.

Is there power left on the table? Yes. The customer has plans to come back and get a Haltech Platinum installed and tuned (including boost control).

 

the only reflash I'd trust is a Cobb Access port flash where you can actually tune the ECU in real time. Lowering the compression is something that can easily be adjusted for