cpet

They told me via email that turbocharging a stock rotary engine in an RX8 does not break the engine. They said the engine fails due to backpressure.

Their response:

"It is not the boost that breaks the motor. It is the backpressure. If you have a backhousing ratio of less than 1 then you'd be okay but that would be a really big turbo that wouldn't get boost until 5000-6000 rpm.

You can run the stock rotors and be fine but the turbo has to be huge.

Most customers get the rebuild non turbo for reliability."

They didn't comment on the reduction of the compression ratio of 10:1 to 7:1 or less for turbocharging.

RIWWP

iTrader: (2)

Well, the fact that an engine is turbocharged doesn't also inherently mean it's broken. It's just usually the result. There are quite a few reasons why a turbocharger install would break an engine, and saying that there is only 1 source of the problem is irresponsible. Every potential damage source has to be addressed.

I.E: sure, solve whatever "backpressure" issue they are referring to (I'm skeptical of the terminology used), but ignore AFRs and let it get to 14s+ under boost, and no, you aren't suddenly fine.

cpet

I'm having a hard time not believing a company that specialises in rotaries. They've been working with rotary engines for 20 years.

I also really can't find information on turbocharging the RX8. I've been reading the forum for weeks and most of the posts are generalities, not specifics. Also, everyone I talk to has their own opinion on whether the RX8 can handle a turbo or not.

Something tells me if I want more HP I need to remove the rotary engine and drop an inline v-6 in the thing and turbocharge that. I've only seen people drop that LS1 V8 into the RX8 tho. That engine seems far too big for the RX8.

Stray

A+ thread. Would read again.

paimon.soror

iTrader: (15)

Yep, god forbid any profitable business in the USA should fib just a bit to get a potential customer to spend $$$$

Take note 98.3244666% of them have no first hand experience.

And this thread is gone to the sky

RIWWP

iTrader: (2)

I'm not saying that they are wrong, just that their choice of terminology seems to be a bit poor, and even if that was clear, claiming that there is only 1 problem with turbocharging the 8 is very very short sighted. I'm sure the responder knows that there are actually plenty of other problems with turbocharging, and is just not really thinking about them at the time, assuming that they are "given".

Just a caution to not take the statement as the entire story.

cpet

Well, the fact is, a V6 would handle a turbo and they aren't alien to people.

Pettit also has 25 years working on rotaries. Hard to believe anyone, I agree, as everyone so far as given me a different story, even if they aren't trying to sell me something.

If I removed the alien part from the car, yes it would kill the cars spirit, but it would also put the cars limits in a known state.

RIWWP

iTrader: (2)

Fact:
You can buy an E36 M3 for less than the cost of turbocharging an RX-8.

There is your inline 6

cpet

The thing is I really love the way this car looks. I hate to say I bought it because of the design but that in part is true.

I would rather drop the money into making this car as awesome as it looks.

Mazda dropped the ball. I will probably take the advice of Pettit racing. I'll most likely drop one of their rebuilt rotary engines into her and turbo that.

They do a lot to improve the engines reliability:

Every engine receives the following enhancements:

FLEX ARMOR APEX SEAL FORTIFICATION— OUR LATEST TECHNOLOGY TO FURTHER STRENGTHEN AND SAFEGUARD YOUR ENGINE

BLUEPRINTED, STREET PORTED, AND ALL CRITICAL WEAR / CONTACT SURFACES RECEIVE OUR PROPRIETARY FINISHING TREATMENT

PETTIT HOUSING MODS IMPROVE COOLING TO MINIMIZE SURFACE PROTRUSION AROUND LEAD PLUGS

MODS TO SEAL PATH AND PORTS HELP TO BETTER MAINTAIN COMPRESSION SEAL INTEGRITY DURING PORT CROSSING AND CLOSURE

OIL SYSTEM MODS IMPROVE OIL FLOW TO BEARINGS

MAIN & ROTOR BEARINGS CLEARANCED TO RACE P-SPECS

EIGHT QUALITY CONTROL INSPECTIONS

CLEAN-ROOM ASSEMBLED W/ROTOR PRO TOOLS

STATIC COMPRESSION TESTED, CAPPED AND SKIN-SEALED FOR SHIPPING

I'm willing to bet if I get one of their engines I can put a smaller sized turbo on it without risking failure. If they say otherwise my backup plan will be to get rid of the rotary and replace it with a piston engine. No it won't be able to rev to 7500+ RPM but that will be a moot point when it has 400+ HP.

TrickWilliams

The rotary isnt an alien part. The fact is these "alien" parts have been being worked on for 20 or 25 years ( you seem to not be sure). There is plenty of information out there on if the rotary can handle boost or not. Believe it or not most of that information is on this site. Just look for it. There is alot more on here then just general information. Ive learned alot of this site on boost with rotaries. That being good or bad, I guess I wont know until my engine is done and ready.

RIWWP

iTrader: (2)

Yes, getting a built engine prior to boosting it is a good thing, and yes, Pettit builds some of the best engines available.

I'm just pointing out that you STILL have to have a clear plan to address every single one of the failure methods. Miss one, and that will be the one that pops your engine. A proper tune, a properly sized turbo, a properly designed intake, the right cooling and oil system changes, the right oil and water lines and fittings, the right fuel system choices, EGT heat management, etc ...

It's more than a simple "backpressure" problem that causes turbo Renesis engine failures.





A claim that a $30,000+ engine swap is the backup plan is also something we chuckle at.

cpet

It is an alien part. Take that car to a mechanic in town and ask him to work on it for you. I've been turned down by a lot of speed shops. They don't know anything about rotaries. Speed 6 in Jacksonville, FL told me they can't work on them. I've only found 2 shops in FL that can work on rotaries. They are in south FL.

It's not even remotely standard. 99% of all other cars have piston engines.

I said in an earlier post I've read through all the "Read this first posts" regarding turbocharging the engine. There is no manual for turbocharging this car. Even you don't know yet -- you're waiting to see if it's a good idea. It may not be. You're engine may run great for 100K miles, or it may blow up in 10K miles. The point is you as well as most people, including myself, don't know.

9krpmrx8

iTrader: (46)

Gotta love rotary "experts".

kevinande

meh, just buy a different car. Plenty cars that go fast in a straight line.....with piston engines.

gwilliams6

cpet listen to the good advice of RIWWP . I have owned three turbocharged RXs, a first gen RX7 converted to racing with a Racing Beat built turbocharged 13B rotary engine that could produce upwards of 400 HP. But everything had to be changed for the car to handle that, the engine was specially built with low compression rotors and special seals and race porting, a racing radiator to handle the extra heat, extra oil coolers, racing strengthened and lightened flywheel, strengthen clutch, racing driveshaft, transmission upgrades, racing limited slip rear end. Racing ignition with special high energy coils and wires and racing plugs. Braided lines for all systems. High flow fuel pump and a 4 barrel Holly Carburetor (yes the Holly worked better than the early fuel injection systems for the rotary). Full freeflow racing beat exhuast. (the car wasn't really smog legal for the street. ) All kinds of suspension upgrades and safety upgrades and aerodynamic body additions like a full rear wing to keep it on the road. I spent more on that engine than the original First Gen RX7 cost to buy. When I was all done the car had to be insured by LLoyds of London. Then I owned a stock Second Gen RX7 Turbo II with 200 hp, and later a Third Gen FD twin turbo RX7 with 255 hp.

The point to all this is just what RIWWP says, there are so many things that if they aren't just right can contribute to you killing a turbo charged rotary engine. Just a few include heat , cooling, ignition, fuel delivery, exhaust and so many other things.

I have used Pettit racing products over the years with success and yes they have built some killer rotary engines and race cars, but RIWWP is correct that Pettit is giving you too simple an answer to your inquiries. The Renesis engine was frankly NOT designed to be turbocharged with the highest NA compression of any stock rotary to date. When you add turbocharging you are adding even more compression and if the engine parts aren't significantly strengthened and the fuel, ignition and boost are not carefully controlled, you WILL kill this engine.

pistonhater

Under-budget is what kills a turbo charged engine - rotors and pistons alike.

So many people get caught up with JUST getting the money to do the turbo install...to then realize they need twice the amount of money they just spent on tuning and addressing the other million issues mentioned above.

When they realize they are out of money, then they start taking short-cuts.

ShellDude

iTrader: (12)

70,500 miles on the odo … hit it today

been boosted since 20,000 ish

Original motor

Third turbo

go figure

gwilliams6

hi shelldude, I am from suburban new jersey, outside philly. Maybe we have met at some area meet in the past. Tell us why three turbos, what turbo setup, and what tuning and fuel management and boost pressure are you using, and were there any internal upgrades to your engine and seals ? And what upgrades do you have for cooling, exhaust etc. on the car

ShellDude

iTrader: (12)

Way way too much for me capture in a single post. I have all kinds of build/mod threads throughout the forum...

It is not cheap guys.

Carbon8

iTrader: (4)

Cam needs to update that website, they do not use flexforce seals anymore for FI rebuilds.

Stray

OP can't find a rotary shop in florida.




Top lel. Drive to Sanford and throw a rock. There. I found a rotary shop for you. I don't mean that in a bad way or anything, I just used to literally pass at least a half dozen mom and pop rotary shops on my way to work. Of course, you could always drive to Palm Beach and check Petit out in person, I suppose.

TrickWilliams

Of coarse there is no manual, but there are alot of tried attempts at boosting. Failed or not. Read turbo build threads. Learn from them. What worked for them and what didnt work. Then with the best of your new learned knowledge start in. Its alot of trial and error. Listen to these guys. They have done all of this and are trying to lead you in the right path. Just dont cheap out. Reliability and a rotary can go hand in hand. With the right parts and the right tunning. Your just not putting in any effort. You called one shop and they told you enough to try and get a sale. Thats it.

cpet

Where did you read that? I'm fairy certain I said I found two...

Brettus

iTrader: (2)

There are many examples of people fitting small (greddy ) turbos to their stock block renesis 8 and having no engine problems whatsoever . These are people that took the time to find out the correct way to install/tune it . Unfortunately for every person that did it right there are probably 2 that didn't .
What Pettit are saying only applies to certain situations and borders on being labeled as utter BS when applied to a street car with a small turbo running low boost that is well setup, well tuned and well maintained.

niteshade247

Just let him slap one on and when he posts "failed engine" give him a big fat "I told you" or get it in writing that they guarantee that the turbo they sell you will in no way do or cause eney harm to your stock engine under reason. I would bet my car they will not do this that is because they can not and know better than give you such a guarantee.