t618z upgrade question
 

hi again guys. so my friend purchased a greddy turbo kit for his rx-8 and was wondering if he could upgrade his little turbo to something bigger...now from what i understand the greddy turbo kit is a EXTREMLY TIGHT FIT! another thing is when it comes to upgrading the turbo you need to be space concious due to the fact there isnt much room for play.

he is kinda upset that the turbo can only hold around 6 psi, i was told from a guy who knows a lot about rx-7's he said you CAN boost higher than 6 psi but the turbo will lose pressure at higher rpms's and sit back down on 6psi.

my friend would like to get around 9-10 psi and would like to get 300 hp.

he was wondering if there is a better turbo that he could upgrade to.

from what i understand he needs to find a turbo with a bigger rear a.r while the actual turbo physical size remains the same.

do any of you rx-8'ers know a turbo he can purchase that will give him what he needs.

tuning-
he will be purchasing interceptor x for tuning in the near future

thanks a million

-mike

4 turbo kits were just released by mazsport that will get you well over the 300whp mark, and they do so far more reliably than the greddy setup. they're a forum vendor here, so look around.

Short answer: No.

Long answer: I used to believe the boost drop problem was related to the wastegate. Now I believe its due to running the turbo up near the choke line.
This is especially a problem for those of us at high altitudes where you have to run a higher pressure ratio to get the same power output. The turbo was sized properly for higher boost - if you never go past about 6kRPM. So, it seems to me that GReddy looked only at the displacement of the Renesis and forgot about the insane redline.

There is an 'upgrade' from Bullseye, but we really haven't heard anything about how it performs. You're really looking at a separate kit altogether, like the ones now available from SFR, and Mazsport. I have heard that one forum member put a GT30 in that spot. According to that turbos maps you should be able to flow plenty of air at the higher RPM. I have no idea what it would take to get it to fit down there.

Greddy's kit was more or less sized to run 6 psi. Running 9 psi requires 15% more flow than design. Greddy sized a turbo that would provide 50-60 whp in the mid range up to the power peak. That's where the highest efficiency of the turbo likely is. Bumping up your pressure ratio is going to bring you up toward the surge line and out of the high efficiency area. You can't really blame Greddy that their kit doesn't push 10 psi through redline when it is designed for 6. There are, I believe, some greddy kits out there getting close to if not 300 rwhp with just an interceptor tune done well.

I would contact Scott at Mazsport and see about his greddy upgrade. With his mods to the turbo and a good tune you'll get a good 280ish with a nice powerband. that kit is not designed to go above that point.

Scotts powerband with his previous greddy cars has been down right scary.

Just a note: Surge line is on the lefthand side of the map. Choke line is on the right side.

9-10psi at redline is possible with the Greddy kit, at least at lower elevations. You need to tighten down the WG actuator and get a free flowing exhaust, I recommend the TurboXS exhaust and racepipe. I put down 287whp at 7psi. I'm running 9-10psi now, so I should be pretty damn close to 300whp if not a little over. I can post datalogs if anyone doesn't believe its possible.

If he wants more, then upgrade to a better kit. I wouldn't bother with trying to fit a bigger turbo to the Greddy kit.

Right - upping your boost will push you up towards the surge line (which usually curves in) at lower RPM. Trying to to hold that boost all the way to redline depends on the choke line.

yeah talk to scott at mazsport and he'll make a whole game plan for the 8, just tell him what you want. That's what i did. as of now i'm running the greddy and pushing close to 300, but soon i shall have one of his other kits which as just plain badass.

so do any of you know of a turbo replacement that he could buy?

Yes. the GT55 should be good for about 1000HP.

Read the friggin responses you already got.

good info, thanks :)

alright thanks.