We've seen cracking at the spark plug holes on NA cars. Is that what you're talking about?

 

Yeah, high EGTs and localized heating/inadequate cooling. You'll see the same thing if you get too aggressive with a blower too. Back-pressure doesn't have a thing to do with it. Never mind that a turbo system that is set up properly won't create much back-pressure in the first place.

 

No, he was talking about the lip around the opening of the exhaust ports I think.

 

you dont read well do you.
i know nothing about your SC's. maybe they are efficient at 12psi, i doubt it, but feel free to turn off your water/meth and find outwhat your IAT's look like.

again the point being, that data is all based on turbo kits that were meant for 5-6psi and run at twice that, OUT of the efficiency range.

you mean Pettit has a solution for this: so you're saying that producing a supercharger kit is far cheaper than simply selecting the proper sized turbo for the conditions you will put it through.... fantastic

 

The Pettit paper is carefully constructed to construe that the presence of the turbo and manifold caused the high EGTs.
Obviously, that was meant to imply that S/C don't elevate the EGTs as well.

The problem is not an external restriction - its the exhaust ports themselves.
Any time you ask the exhaust ports to flow twice the amount of air they were designed to flow, the residual heat is going to increase.

The S/C owners have yet to push that kind of power/air-flow through the motor and will not be able to without a substantial amount of W/M injection which offsets a lot of the EGT issue.
Meanwhile, there have been quite a few turbo cars pushed well beyond the design limits of the kits and the motor without a lot of secondary charge cooling.

 

Theory on cause of turbo Renesis seal failures, by Pettit

Basically the whole thing is a marketing sham to push their product on less understanding people. There is plenty of market for an FI kit that will put you in the 280-330whp range. So how do you ensure you can produce a kit that will sell?

1) Produce a solution that reaches the desired output via a means not already well marketed(SC).
check

2) Produce some legitimate research data on the well marketed options(TC), but very carefully and intentionally be vague about certain details, imply certain things, and hope that fanboi's and ignorant people will run with it.
check

Basically what it comes down to is that any turbo charger is going to be a restriction of some degree in the exhaust stream, how much - no one has flow tested pre and post turbo to my knowledge...?
And none of the Pettit SC'd guys will ever get near the power levels that the turbo guys reached a year ago unless they are trailering 1,000 liters of water/meth behind them. The blower is just too small and inefficient.

 

Theory on cause of turbo Renesis seal failures, by Pettit

Pettit's paper is a marketing strategy.

-We all know Pettit knows the turbo game well
-Pettit knows that you only run into the issues presented in their paper if you are running a turbo beyind its design limitations and/or pushing massively more air out the exhaust ports than they were designed for
-There are plenty of potential FI owners not looking for extremes, but just a bump in power

So you take some legitimate research, color it up pretty and carefully word what you say and dont say, all while leaving the impression on those who wouldnt know any better that turbo's are somehow bad and not as safe as a SC. Never mind that the issues you researched were found in applications flowing 30% or more exhaust than the SC your marketing ever will...

 

Woah....

Pettit was turbocharging Renesis engines well before anyone on this board was doing it and produced more power with them then anyone here has managed to do up until this year. I think that would indicate they know what a properly sized turbo is

 

pettit turbo'd an RX-8? links plz.

 

Its not a large secret Petit did the engine development for Diasio including the Diasio D962R Turbo which has a renesis with a GT35 turbo....

https://www.rx8club.com/rx-8-multimedia-photo-gallery-6/diasio-track-car-renesis-powered-104551/


... you can also find reports out there in cyber land of lots of troubles with the engine in the early cars - which would be where I would assume Pettit came up with enough information to publish the said paper. I'm not going to say they were right or wrong in their decision to go supercharger over turbocharger, but I would venture to guess they picked supercharging for several reasons and "not knowing how to size a turbo" or "no experience with a turbo" is not one of them.

 

Pettit actually installed the greddy in my car.

 

man sebring has such a rough surface. i hate it every time i play it in forza. the diasio was ripping it up though.

seriously, they should repave it. screw its history.

 

Where did I even imply that somehow my supercharger functioned outside of the laws of physics? I may have a thick head, but I minored in physics, so I'm well aware.

As for that, not all of the information they compiled fit this description, it's just that particular example.

MM's right, the location of the exhaust ports is the problem. Pettit's findings are that a turbo will amplify this problem (more so than a supercharger would) unless certain modifications are made to the engines internals. They have addressed these issues with their race winning 370 whp Renesis engines that they build for Diasio, and for that, we should all be thankful. Isn't it great that there are race cars flying around that are making 370 whp reliably and winning races with pretty much the same engine you have under your hood?!?

 

How is this helping the OP answer his question. This has turned into a super vs turbo argument. Boost is Boost. The engine doesn't care where it came from.

 

The point of my previous post is that this is incorrect.
There is no difference in this respect if it is TC or SC.

Well, the OP asked if he should go turbo or not. The TC vs. SC "argument" is an integral part of this decision making process.

Boost is boost. And while it is a bit of a simplification to say that the engine doesn't care where it came from, the process by which the increased manifold pressure is generated is integral to the discussion of net power.

 

Hello and welcome to the short bus, please sit in the back with the other kids who can't read.


The only way that the above isnt true is if that data and those engines came from diasio cars. They chose the 35 turbo because it does fit the application, but it's more what MM said:

..................................



Lemme make it pretty and organized:
-There are 2 probable sources that those photos and data came from. Diasio cars, Greddy kits
-There are two problem areas to discuss. Exhaust ports, spark plug holes.
-The issues at both of these areas is heat, both areas have experienced conditions that exceed the cooling capacity of the motor.


Scenario 1 - Greddy kit motors/data
-Kit was designed/meant for 5-6psi. Run nearly, or at twice that.
-Running out of the efficiency range generates extreme IAT's. This creates excessive combustion chamber temps. Exceeding the cooling capacity of the area around the spark plug holes is inevitable. This issue has also been seen on NA cars
-Excessive combustion temps = excessive exhaust temps. Add to that, the possibility that the far undersized(for application) turbo creates excessive back pressure. Cooling capacity has been exceeded in the area of the exhaust ports..
Solution to Scenario 1:
-Properly size your turbo
-Dont expect your hardware to perform beyond their means of intent without consequences.

Scenario 2 - Diasio motors/data:
-Turbo sized properly for its application.
-Compessing air generates heat. More air = more heat. Those turbo flow a LOT of air - a requirement for producing that kind of power. Even if you had a 100% effecient intercooler and ambient IAT's, flowing 45lbs/min through this motor @ 10:1 generates excess heat. Exceeding the cooling capacity of the area around the spark plug holes is inevitable. This issue has also been seen on NA cars
-Excessive heat already exists due to compessing twice the air mass the motor was designed to flow. Now flow the resultant, hotter than norm, exhaust gases through the same ports that were designed for half the flow.
**Combine all that with the fact that these are TRACK ONLY cars and not even street legal, the motors spend their entire lifespan under track or dyno conditions.**

These are not hard concepts, i dont get too deep into physics, but these are simple principles.

** Go take your car and drive the rest of your motors life on the track and see how long and how well it holds up.

 

Tell me how the spark plug holes are affected by back pressure created by a turbo? Do you know how much time the spark plugs and the exhaust ports spend in the same chamber?? The SC is no "softer" here.

IF you guys had SC's that could make that kind of power without trailering a swimming pool full of W/M you'd find that SC's would have the same exhaust port issues.

I hope to GOD someone eventually tries a larger SC. Then you would all shut up when you realized that you have all the same weakness' as TC guys do, only your car would suck until redline with a SC that big.

 

Man, this is pretty disapointin to me, I did some background check on the car before I got it, I knew bout the flooding, and other possible problems but did't think the car was this "delicate", If i knew this i would of jus bough the JDM FD i test drove in Montreal it was a 1993 with 92 km for $9500 but thought that since it was an older car it would'nt last too long as i was lookin for a DD that I would still be able to modify to my liking, SHIEEET shoulda gone with the FD if anythin i could of jus got a new 20b or sumthin.

 

The Renesis motor is magnitudes tougher than the REW motor was.

All the nonsense above is about pushing the Renesis to its limits. Although this motor is much more resiliant than previous rotaries, they arent as easily kicked into 400+ HP range, largely due to 10:1 compression. Really that doesnt matter for a street car anyway. No one needs a street driven RX-8 with more than 330-350whp.

 

Its the port restrictions that are going to hold it back.
The higher compression just means it will take less boost to make the same power.

 

wow...you sure did your research didnt you?

 

ehhh, my head is mush from the other crap today. it seems like i understand a lot of thee type things until i open my mouth, then it goes all to hell lol.

oh, sometime after the holiday hangovers have worn off, lemme know about the misc stuff we talked about

 

why do people completely loose their minds on this forum when it comes to this subject???


Pettit went SC for 1 of 2 reasons.... either ...
a) They felt there was truely reliability concerns going with a turbo on this engine
b) They felt for some reason they could market a supercharged rotary over a turbo rotary in some kind of niche market

What you believe it entirely up to the individual because there is no frikkin evidence outside of Pettit to prove either senarios.... so everyone stop talking like there is!!!

 

All I have to say is

The only thing that is a disappointment is another 8 owner like you.

 

I don't mind Pettit having a SC. I welcome more FI options.

I just dislike misleading statements. It's one thing if the SC guys made more power or something that is factual that they can brag about, it's another to come in with mumbojumbo stuff.

Anyway, I'd like to hear if what Bastage was talking about was the housing by the spark plugs cracking or something else. Because we have plenty of NA engine teardowns that we can compare with to see if the supposedly "turbo caused" issues are present in NA form.