Only if I can HAVE THE BEWBIEZ!

 

I lol'ed.

But, seriously, the whole "soft" boost versus "hard" boost issue has gotten completely out of hand.
These days, with the advent of Snuggles and Downy, there just isn't any reason to run "hard" boost any more and risk damage to your exhaust valves.
Boost should ALWAYS be soft.
And, if you want to run high, soft boost, you can always get a performance camshaft to lower the compression to a much safer, 5.648:1 ratio.

 

is this your way of saying No ?

 

Absolutely fantasic comment!

 

this white paper has nothing to do with "soft boost" vs "hard boost." Anyone who says that has not actually read it and is wetoddid.



They chose to try a supercharger solution because of these issues, and were able to develop a very successful product. Pettit Racing loves turbos, they sell them and rebuild them for the RX-7s and have installed plenty of them on RX-8s. However, they will not recommend a turbo solution for the RX-8 without significant modification to the Renesis engine's internals. They make these modifications to the Renesis for the Diasio Racing turboed model, and have been able to run them at over 370 whp @ 12 psi safely with these modifications.

 

I read it. I've run 12 psi for about 10k miles, and my engine internals looked nothing like that.

Maybe it's because I run the sohn adapter, and take other precautions and don't just slap on a turbo kit and expect it to run properly.

Honestly, I was expecting my engine to look like ****, because I didn't baby it. I boosted all the time when I drove it.

I don't have a problem with the information Cam put out, I just have an issue with what you're implying with your sig. My point is, if 12 psi does cause that damage, it will happen regardless of FI method used. Your sig implies otherwise.

 

My sig is the title of the document; exactly.

BTW, since they wrote that paper a few years ago, they've rebuild dozens of failed turboed Renesis engines, most of them had the same problems. Maybe your sohn adapter helped, or maybe you don't drive your car as hard as you think you do. You definitely don't drag race or autocross it

 

I won't argue those points. However, a true litmus test on your sig would be if cam came out with a similar document that mentioned superchargers. Would you so proudly put it in your sig?

 

I probably would have gone (and I actually almost went with) a turbo, but that isn't the case. They developed the supercharger for the reason described in that document.

I link that document in my signature because I think the information contained within it is worth sharing.

 

are you sure they didn't write the doc AFTER ther developed the SC ? Because that would be quite smart of them if they did ......

 

They actually documented their findings years before they came out with the kit (it's only been out since April of 2007).

If Cam spent any time on this forum it would have come to light much sooner, and probably would have sold twice as many supercharger kits. He's not sly when it comes to being a businessman, he takes more of the old-fashioned approach of just keeping his customers happy, and for the year and a half that I've been a customer he's done a really good job of that.

 

How exactly is the SC any different from any other FI kit that runs at 6 psi? If the only saving grace is that you had no higher psi pulley, that is easy to achieve on a turbo setup by simply not buying a boost controller and saving a few hundred dollars in the process.

 

umm exhaust gas flow path? please don't be that ignorant...

 

Are you sure you've read the document? Read it again, I think you're missing the point of it. There's a reason why those problems exist specifically for turbo applications.

BTW, I've always been at 8-9 psi, as was everyone who bought the Pettit kit after me up until Norman and Juan who recently got the 10-12 psi pulley.

 

I haven't seen any elevated EGT's. I also don't run a cat.

20k miles of FI and 30k NA, and the internals looked normal, and as I said, normal compression to boot.

Go figure.

 

Heat transfer into the exhaust port would be effected by EGT, backpressure, and flow... I don't think i've seen anyone measuring pre-turbo EGT or backpressure and comparing it to a supercharged pre-cat EGT and backpressure

until then... it remains a mystery

 

I'm certainly not going to drill into my manifold to test it.

All I can say is that I have a fairly typical turbo setup and had no issues from it even after a full engine tear down and inspection. A better test would be to go 50k - 100k miles with FI and do the same. But to have 50k FI, most people don't go FI till they have 30-50k miles on the engine, so we're talking about a 80-100k vehicle when it only came out in 2004.

However with NA engines falling apart without any modifications, the results may be worthless unless we have enough of a sample.

 

That may have been so in your case(when you were still boosted), but it wasn't the case for the many turboed engines that Pettit has had to rebuild, many of which were driven in really hard racing conditions.

Is it correct for me to say that most of your hard driving consisted of dropping to a lower gear while on the highway and flooring it? If that's the case, it's no wonder why you haven't seen anything different.

 

Petit's theory is a bit far fetched. There is some good information in that document, but to say that some additional back-pressure is the only reason for failure is quite a leap.

Take and abuse ten engines, half turbo charged, and half supercharged, that make the same output (not just PEAK output, but across the board), and then tear them down and have a look. I'll bet anything that you won't see anything that points to either being more reliable.

 

jesus man, you dont get it do you.... the whole "hard boost/soft boost" arguement is because what you IMPLY by throwing this stuff around in such an uneducated manner is that the turbo itself is to blame.

RTMFM dude. your OWN posted image has it all:
thats the potential effect of running a turbo beyond where its efficient.

will a supercharger do the same thing when run far more boost than designed/efficient for? no.
but, you tell me what happens when you have a supercharger compressor meant for 6psi and efficient at that flow - and then you just swap pullies and start trying to crank out 10-12psi.....

OOPS... its no different huh?

Pettit didnt make the SC kit cause they knew why turbo motors were failing. They know that the issues they advertised in that image are solved by using a properly sized turbo. Pettit chose to advertise that data, in the manner they have, as a frigging gimmick for people like you who would buy it blindly, or just plain not know any better.

 

That's exactly the problem. There aren't nearly as many Pettit SC cars on the road as greddy (or other turbo kits). Add to it that the Pettit kit came out years after the GReddy had been around - back when we were still figuring out how to properly piggyback on it.. then factor in that the Pettit guys were limited to 7 psi or whatever it was, when every TC'ed numbskull with a boost controller can flip it up at a whim...

Now you start to get a better picture of the situation.

So... if we only had 2 dozen turbo owners, they couldn't go beyond 7 psi boost, and fuel management was PCM flash based and the kit has only been out for 1-2 years, I'm sure the results would be similar.

 

Exactly. If you go much higher than 9 psi, the greddy makes heat instead of boost. Which is one of the reasons why the 3071R is attractive. It's a real ball bearing turbo, flows better, scales better, and is all around a better solution.

 

everyone knows how far ppl were pushing the greddy turbo, which is practically all anyone knew about or had availible prior to the time you say Pettit came up with all this research.

now, you may still be well and good in the efficiency range with a 10-12lb pulley... i dunno honestly. turn your water/meth off and see.

but go ahead and get a pulley made for double the psi you kit is intended for(that'd be what 16-17psi?) and see what happens. cause thats what the Greddy owners were doing...

maybe there is THAT much backpressure with a turbo then... its really irrelevent. at that point you'd need a tanker truck full water/meth to keep your temps down, assuming you hadnt already scattered the SC all over you engine bay.

they are different things, the operate differently to achieve the same basic goal. when you design them poorly, put them together poorly, push them beyond their limits(design or physical), or maintain them poorly, they will both fail. Perhaps in unique distinctive ways. the point is though, they will BOTH fail

 

Totally get it, but there is no hard/soft boost argument. What's uneducated about the manner I "throw this stuff around?" Just read it, there's nothing misleading about it. I don't, however, get the RTMFM, not hip to the internet-speak I guess.

I don't get this though, since you're completely contradicting yourself here. BTW, I've driven a Pettit SCed car at 12PSI, and all I noticed that was different was I got pushed a little harder into the back of my seat.

You certainly can't prove that, and I'd bet a pretty penny that no one has bought the supercharger kit because of that document, so this point is moot. It's just there because it's worth sharing.

 

The damage that they're consistently seeing on turboed Renesis engines is at the exhaust port (see the document, and the pictures of the "chatter" indications just past the plug holes). Can you think of another explanation for that particular damage? If so, please share it with us.

It's not just about reliability, it's about diagnosing a problem and proposing a solution. They have a proven solution for it, and they've implemented it on the many Renesis engines they've built for the turboed Diasio Sports Racers. The problem is, that solution is far more expensive than just using a conventional supercharger to boost an engine.

Oh, and my purchase decision wasn't "blind," although I wish I was wealthy enough to blindly spend that kind of money.