When I bought my car, I had a lengthy discussion with the finance and sales reps who said there were internal rumors of R&D going into a branded turbo kit to be released as a supported product you could have installed at the dealer.

In addition, he said that if the RX-8 performed well, they were looking at bringing back the RX-7 with a twin-turbo'd version of the Renesis.

Think he was full of it? I kind of do.

The only redeeming point on this was an independant review from consumerguide that mentioned that a turbo mod was in the works for the RX-8 by Mazda, and if the car sold well that the 7 might return. Seems to corroborate it some, or perhaps consumerguide just heard the same rumors...

I love the idea of a turbo "accessory" coming out that the dealer could install, but I really can't see that happening.

 

wow i hope thats after my birthday when im getting my car.... that would be awesome what type of hw u think that would add i say we would have 260.would the engine over heat??????

 

He must have a really good source if its true? About 75000 RX8s
built so far, so I think any major changes are far down the road.....

 

Sales reps don't know ****. They'll say anything, so don't take what they say to heart.

 

As great as it sounds, there is just no way Mazda is going to put together a turbo kit. They may make a turbocharged version of the car, but not a kit. There are just too many things beyond the turbo that need to be done at the same time to make everything work right.

 

From where I go for all of my 8's tunning needs...
A turbo conversion is possible but the engine would have to be dismantled, exhaust, and intake ports would have to be reshaped and or relocated in the rotary housing, due to the fact that this particular engine unlike the rx-7s is very highly pressured. Forcing any other air, such as using a turbo, supercharger etc. would cause for blown apex seals. Unless, AGAIN, the engine is broken down and rebuilt to withstand the air induced force from a turbine. Or the use of a low-boost turbo which could very well be a big waste of money considering the other mods that can be done to the 8 instead.

The advice I was handed was to either swap my engine for a rotary that can handle a full turbo conversion or stick to the mods other than the turbo... fly wheel (huge improvement in getting into the high rpm range off the "line"), full exhaust modification, header, high flow cat or no cat, ecu configuration, intake, and possibly a carbon fiber drive shaft when all of this is available.

I could be wrong but I'm going by what a mechanic who has been building, modding, and racing rotary for over 30 years. The finance managers want to tell you what you want to hear... remember they get a percent of that pretty car their saleman just sold you. It's too bad it has to be like that.

 

Apparantly RE Amemiya, GReddy/Trust, Knight Sports, Blitz and a few others are planning on lots of liabililty from blown Apex seals, or low sales of their kits. This mechanic is wrong about a low boost T/C or S/C. Check out this thread.

Is it my bad memory, or doesn't the RX-8 already have a carbon fiber drive shaft??

 

RX8 already has a carbon fiber driveshaft.

 

I'd rather have an 8 with bigger rotors or a third rotor.. I highly doubt Mazda wants to repeat the FD debacle..

 

From what I've learned over the past few months the 8 is pretty much turbo ready. Take for instance the fuel system. Two electronicaly controlled fuel pumps. The ECU controls fuel pressure directly at the pumps, so increasing fuel pressure and volume is just a matter of inserting the proper code. All that would be needed then would be larger injectors.

 

There is a very logical reason why the RX-8 has 2 fuel pumps. If you have ever noticed, the fuel tank sits on either side of the transmission tunnel but there is no connection below the transmission. Dual fuel pumps are needed to provide fuel from each side of the tank.

I do agree with what you are saying though. Modify the signal to the pumps and install larger injectors. We still need an ecu to tune everything though.

 

I would hardly call the RX-8 "tubo-ready." Certainly, the Renesis' high compression and intake configuration (at least on the high power US model) do not seem ideal for an FI setup. This has been discussed ad nauseum and I'm sure you could add FI to it in its present form, but I wouldn't say its an ideal situation, especially if you're looking at anything but low boost applications. There was also some talk (rumors or truth, who knows) about the side seals taking the brunt of the extra strain in the side port configuration, something they may not be so well suited to do...but I don't know anything more about that beyond what I've read here.

jds

 

The use of a low boost system isn't a waste of money. Everyone thinks about boost from purely a pressure a boost pressure standpoint when this is really irrelevant without knowing the cfm at which that pressure is available.

The Renesis (6 port) has lots of port timing. This allows us more time to push air into the engine. It also has a high static compression ratio which means a little boost goes a long way.

There are 2 types of compression ratio in an engine. Static compression ratio is the one that everyone knows as 10:1. The other is the effective compression ratio. This is based on the efficiency with which we get air into the engine. It is the function of efficiency and static compression ratio combined. The more air we have in the engine, the higher the effective compression ratio. A higher static compression ratio is also exerting a much greater squeeze on the mix which also raises the effective compression ratio.

Lets put this into perspective. Let's say we were to take an engine apart and lower the compression ratio and compare it to one that is stock. Both use forced induction. It would take the lower compression ratio engine more boost just to get the same power as the high compression low boost engine. How is low boost a waste of money? Obviously it isn't the way to go if someone desires a full blown high horsepower race car but these people are going to rebuild the entire engine anyways.

There is no reason whatsoever that the Renesis ports need to be enlarged to turbo it. The intake ports are already 30% larger than the previous rotaries. Those engines need to be ported to match the stock port timing of the Renesis. The Renesis exhaust ports, which admittedly can be improved, have 50% more area than the stock 13B exhaust ports. Their timing, while less, is more condusive to making power. You can have too much port timing and this was just a function of old port location.

Any engine, even a specially built one, can be blown up if it isn't tuned properly. There is no reason why a properly tuned stock Renesis can't get 350+ hp wothout harm. People used to say the older 13B engines had to be rebuilt because the seals couldn't handle the boost but there have been 600 hp RX-7's that use totally stock Mazda seals. Several years ago Ari Yallon from Rotary Performance ran a stock ported Mazda remanufactured engine with 26 psi of boost (with a T-76) and nitrous for an entire season without an engine failure! It dynoed at 620 rwhp on nitrous.

People say that due to the shorter Renesis apex seals they are more prone to break. This however is offset by the fact that they are stronger than the previous apex seals.

The number one thing that kills engines is bad tuning. Unfortunately this is more common and easier than good tuning. Your mechanic told you wrong.

 

Sorry... that isn't enough to consider it "turbo ready." According to the JDM pros like GReddy/Trust and RE Amemiya, the Renesis engine can't take more than low boost. Not even just a compression problem... they say it's the whole system... cooling, fuel, etc. So no... it's not really "turbo ready."

 

Japan8, When isn't it the whole system? Compression ratio isn't the problem in any FI application, effective compression ratio is. That is the equivalent compression ratio that physical CR plus boost equals.

I stated a single example, Rotarygod wrote his usual treatise ( always informative ). The Renesis was designed to be more durable than the 13b ( although I must add that aside from FI engines rotarys are fairly durable anyway. ). It seems to me that the turbo 13bs' history of failures under high boost is being used as the benchmark for the Renesis. No one has yet put forward a convincing arguement for the Renesis being less durable the the FDs' 13b.

I'm not going to argue technical merit ( because I don't feel like it ). Rather I will take the wait and see approach. Of course there is nothing really daring about betting against the "It can't be done" crowd, it's usually only a matter of time till they're proven wrong.

 

Oh no, if you've read all my posts on the subject, I say the opposite. I say that F/I and specifically turbos are possible... just not necessairly high boost applications.

To oversimplify it...if you are purchasing a "complete bolt-on kit" many would think that it's like getting a cat-back. No "thinking" required... no chaning rotors, apex seals, radiators, etc. And I do know that is what GREddy is trying to build with their upcoming kit... an inexpensive, no-brainer.

BTW, I know adding FI raises the effective compression ratio, not the physical CR. I was aiming for brevity not precision of words. I don't recall seeing RG's typical treatise when I posted... so I do apologize for the redundance my post created in the end, however, these was no need to be snotty.

 

Regardless of what I am about to say I do feel that the cooling system should be improved. It like to play it safe. You can't have too much cooling ability.

Just so no one thinks that the car will automatically have cooling issues, you need to think about under what circumstances it may experience this. Even a high horsepower turbocharged car isn't making any more heat when off boost than a nonturbo car. This pretty much leaves the stock cooling system completely adequate for a clear majority of the cars driven life.

High boost isn't usually held for very long anyways. People are usually on the gas and then off again within a matter of seconds. The entire cooling system isn't going to heat up to critical in that time. You'll probably be off the gas for long enough to bring the temperature back down again fairly quickly. Now we can see that it will be fine for the occasional spirited driving that people do.

If the car was being drag raced, it is only going a quarter of a mile under boost and this isn't long enough to get the entire cooling system up to critical unless it isn't working at all. The stock cooling system would work for drag racing.

The problem with the cooling system under high boost would be for people who are on the gas hard for a long period of time. It would not be adequate for road racing. There are people who drive their cars very hard on the street so it is in fact possible that cooling may become an issue for a few. I don't think this will be the case for a 300 hp system but you never know. The stock 3rd gen RX-7 cooling system sucks yet many people use te stock system with very high power levels. Many also overheat. The RX-8 cooling system is much better than the RX-7 so I don't see why cooling issues would be a necessity with any of the current kits.

It really just comes down to how you drive it. For a majority of the people the stock system will be fine. For the serious people ane those that really drive hard, it won't.

 

Someone brought up the issues of the side seals possibly being a weakness. I need to address this also.

The Renesis side seals are wedge shaped compared to the older seals being flat (relatively). The new seals are made from a stronger material and are thicker. They are a stronger seal from any standpoint.

The typical response to this fact is usually that unlike the peripheral exhaust ports of the older engines, the side seals are now exposed to the hot exhaust gasses. In actuality it isn't as much as one would think. Gas will have inertia and want to flow out of the engine. The exhaust gasses will pass off to the side of the rotor face and out the exhaust port. However they aren't blowing across the side seals. The side seals are down around the side of the rotor rather than on its face. Much of the heat is being shielded be the edge of the rotor so it isn't getting all of the heat energy directed at it. None of the seals are. On the older engines the apex seals did have gasses rushing across them. If anything, this is a way to argue in favor of the new apex seals and their strength.

The side seals really aren't getting much more heat exposure than the older seals. They are also stronger. I don't see how the issue is with them. Every seals gets exposed to the gasses of combustion in some way. If they didn't we wouldn't need them.

The number one issue is still going to be proper tuning. It is safer for a company to say that an engine can't handle boost and then limit it. When that company does figure out ways around the issue and they do release a high power kit, they will look like miracle workers. From a marketing standpoint I would do the same thing. Every company has admitted issues with the stock ecu and retuning it. Better to start low on your claims and end high later. Mazda needs to learn this about their ratings.

 

Good info, Rotarygod...I don't remember exactly where, but somewhere on the forum there was a discussion about the side seals...the concerns seemed to have merit at the time, but from what you've said here it sounds like its not such a big issue after all...which is of course a good thing!

jds

 

Remember this truth:

Salesmen facts are no more than rumors. There rumors are no more than _____________.

Fill in the blank accordingly.

-Mr. Wigggles

 

devious12: who is your rotary mechanic?

 

Sorry for sounding snotty Japan8, that was not my intention. I tend to write as I speak and robbed of inflection my words sometimes appear overly harsh.

My intent in my original post was to simply state that producing a "simple" bolt-on FI kit skouldn't be any more difficult for the RX8 than for any other car. The fuel pumps example was added as an illustration.

 

Ok... I see. No problem. That is just something endemic of electronic medium. As long as we all keep fairly cool heads, misunderstandings like this can quickly and easily be resolved...

Outside of the issues of ecu tuning and space, I agree... creating a bolt-on FI system for the 8 shouldn't be much more difficult than any other modern car.

 

As far as my comments were concerned...they applied purely to the idea of Mazda producing such a kit. I have no doubt that several companies will be selling add-on FI kits before its all said and done...I just don't believe Mazda will be one of them.

jds

 

original post: devious12: who is your rotary mechanic?



I've been going to J&R in Hempstead NY they have been doing rotary for 30 years but I could have misinterpeted what the mechanic told me but I don't think I heard him wrong when he spoke of the 8 having a high compression ratio and being a waste at getting a low-boost turbo for it. Also this is a different engine from what he usually had been working with, the 7. I'm just going by what I was told. DOES ANYONE HAVE ROTARY MECHANICS ON LONG ISLAND NY? THANKS