OtherSyde

With the Pettit kit, our engines should be limited to about ~8,800ish RPM, which is where mine cuts off. This is sub-redline and boost/torque/hp starts dropping off beyond that range anyway, so it's pointless to go much higher. And you're right - in general, superchargers are great for low-to-mid-range power/torque, whereas turbochargers are what you want for mid-to-high-range power. I personally prefer the SC route, but I do want to have a turbo car eventually as well

Brettus

iTrader: (2)

Sorry .... that's not even close to reality (for the Rx8 platform anyway). Unless you are talking about an oversized turbo with poor spoolup .............. and sure there are plenty of those around.

jcbrx8

Yeah, I'm going to have to disagree w/ that statement as well. Fortunately, this is knowable... Have any SC VDs to compare HP / Trq?

Brettus

iTrader: (2)

It's all readily available info on the highest whp thread anyway : https://www.rx8club.com/series-i-maj...m-here-180037/ ....


Note the highest whp SC dyno we've ever seen (in yellow) is bettered pretty much by every turbo dyno everywhere in the power band (including the Greddy) .

jcbrx8

Real talk..., but it'd be nice to see torque as well, and current member SC VDs vs RX8club best ever VDs...

OtherSyde

Yeah I guess that's kind of what I had in my head, the old stereotype. When I joined in ~2013, I read about all those issues in the threads left over from the early 2004-2012 days when this was more the conventional wisdom and people were doing so many poorly-engineered turbo setups and blowing engines left and right. I forget that a lot of modern turbo setups have largely mitigated the spool-up issue. Still, I'll stick with the SC route until someone finally makes a drop-in all-billet Renesis so I can turbo away like a crazy person without fear

TeamRX8

iTrader: (25)

well there was this in the same thread

jcbrx8

Bravo. Thanks, Team.

I do believe there's value in the drive-abilty of the "direct" response of a supercharger vs. a turbo, but beyond that... these HP and torque dynos clearly indicate which mode of FI has the higher HP & torque...across the rpm range on the Renesis.

TeamRX8

iTrader: (25)

not really, but I can appreciate you not wanting to rub it in

obliterx8

iTrader: (3)

Excuse my randomly jumping in after a 2 year hiatus...

I am going the S/C route due to concerns others had posted about the turbo trapping more heat in the exhaust ports (especially the center iron) which could be not so great for the Renesis. This makes sense to me since a turbo is adding a restriction to the exhaust flow, though I haven't seen (and don't know how to find) proof of this. So my decision on S/C vs. turbo was more for longevity (hopefully) than from an expected torque vs horsepower, throttle response, driveability, etc. standpoint. I also liked the more complete nature of the Pettit kit, though since purchasing it, I have swapped out almost all the components, save the S/C and castings, so that didn't end up mattering much.

Is this still fair to say a S/C helps keep the engine more reliable than a turbo with the more modern turbo kits for these cars? I mean a turbo is a turbo as far as exhaust restriction/heat buildup, regardless of the kit.

And inb4: rear mount turbos are stupid.



Also, for anyone who wonders where I went for the last couple years:
I sent the Pettit castings to be polished, the shop moved, closed, held my parts hostage, and then finally gave them back looking worse than when they went in. I had someone else "fix" them then ceramic coat them. Well, they got coated without the polish residue being cleaned off, so they're not polished very well and have clear ceramic coating with black **** underneath. My only options are to leave it that way or sandblast them and re-re-polish. I also had a bunch of stuff powder coated that somehow took a year to do, and some parts were damaged/lost in the process. I'm currently looking for replacements (luckily this is just stock RX-8 stuff, not Pettit related). I'm hoping to be running in the spring. We'll see.

I've been paying attention to some of what you guys have going on, and everyone's 8's are looking pretty nice! Keep holding down the fort here. I'll be back in action soon.

TeamRX8

iTrader: (25)

those are good points about the exhaust port situation, but at the boost/power level of what we see with the SC it’s not really applicable to that. The issue being that most of the turbos you’re referencing for that conclusion were undersized and/or having insufficient turbine flow or held back by other issues such as poor design or lack of proper resources/capabilities to do it right.

I can appreciate how much easier this is to bolt on without getting your hands dirty dealing with all that though, but again, without intending to bash or knock going SC, the serpentine belt issue and power loss drag of having to drive all that friction and momentum mechanically are always going to be offsetting factors.

A cog belt system can at least address the serpentine slippage problem, but will require making the effort to accomplish it and assumes there’s a suitable belt available in the proper width and length. That’s more of an issue for creating higher boost than Pettit had intended.
.

ChrisHolmes2014

Has anyone junked the Pettit charge cooler and replaced it with an air/air intercooler?