^ I second the statement on variability. There is no way to build a single map that's good for even most 8's. I debated this point before the Interceptor was delivered but some people (ahem) claimed that having the control that the interceptor gives would make it so we can all run the same map. Now that the Interceptor has been installed on a few 8's we know this is far from true. Yes, running a map tuned for certain mods when you don't have those same mods is stupid. But, its been proven with the eManage, and now the Interceptor - there is no way to generate a set of engine management parameters that will work on everyone's car, even with the same nominal hardware. That's why the stock ecu adapts in the first place. If you install a turbo kit and expect it to be plug and play, you are a fool and you should expect to: (A) have $hitty performance because the engine runs too rich, or, (B) blow your engine because its too lean.

With regards to the issue of gas: I would argue that if the difference in gas is really causing problems, then the map sucks to start with. Anything tuned that close to the edge is playing with fire. That would be like tuning with a water injection system and running it so close to the edge that it detonates without the H20. When you run out of water you blow your seals. I doubt its really the difference in fuel, but if it is, you guys should tune a little more conservatively. You might get some bad gas one day yourselves...

 

Sammy, the tuner that tuned my car, and PURNRG's car had no previous microtech experience. He was able to figure it out with the help of Scott, and mentioned it was one of the easiest to tune software that he has personally dealt with. I'd of course recommend someone who already knows the software, but if not, make sure he speaks with Scott before and while you are tuning.

 

The reason why you can not use the sam boost maps for different setups is due to efficiency of the turbo system. If you have a sturbo on car A that has a stock exhaust and a turbo system on car B that has a fre flowing exhaust, the differences in exhaust backpressure will effect turbo efficiency. It would be possible for car B to run less boost but make more power. The turbo wouldn't be working as hard to overcome the backpressure which would mean it isn't making the intake air charge heat the car with the stock exhaust is. A map based tune doesn't know of these efficiency differences. It goes beyond just a simple intake temperature sensor. It just knows that at a certain boost level it is to send a certain amount of fuel to the engine with a certain amount of ignition timing. If we added a larger turbo that could flow the same air in cfm but at a lower boost level, it would obviously be sending more air to the engine if it were at the same pressure level. More air needs more fuel. It is a little confusing.

The Renesis engine is actually very consistent engine to engine. What is not consistent is the ecu. A standalone system like the Interceptor should also have consistent results with tuning on different cars provided each other car has the same basic setup. If another car doesn't, there may be issues. If a piggyback style of ecu is used, the inconsistent factory ecu is not being taken out of the equation and can continue to mess things up. This is why I wouldn't touch a piggyback with a ten foot pole on this car.

The RX-8 is nothing special and neither is the engine. Sorry to break the news. The Renesis and the RX-8 are not rocket science. It is not the engine or the car that is inconsistent. It is the factory ecu. The Formula Mazda cars all use the same factory built engine that is off of the exact same assembly line as the RX-8 engines. Nothing different about them at all. They all use the same Motec tune and they all make very consistent numbers. This alone proves there is no issue with the engine as far as consistency is concerned. The fact they have a Motec does nothing to affect the consistency anymore than a Haltech, Microtech, etc would.

As far as tuning goes, it may be a good idea to take the car to be tuned by someone with a Microtech only because they know how the Microtech software works. A Haltech, Microtech, Motec, Megasquirt, Wolf, etc all work the exact same way in what they do and how they do it. The software is the biggest difference as is the number of load points. The theory and understanding is all the same. Someone who can tune one of them properly should be able to tune any of the others properly as well.

 

Nobody is saying that you can run the same maps for different setups. We are saying you can't run the same map for the same setup. I believe if you read the Mazsport forum, you'll see this for yourself.


huh? Can you explain this?

There is no external power applied to the turbo. It can't 'work harder' or easier to make boost. The turbine only spins at what ever rate its design gives for a given set of exhaust gas flow parameters. It can't 'work harder' to overcome slow exhaust gasses - it just won't spin as fast and won't make the boost or will have a lot of lag. The compressor efficiency is what it is for the pressure ratio and intake flow rate. The work done making boost, or making heat, is the same regardless. Its only dependent on compressor design. The compressor side doesn't know or care whats going on on the turbine side.

 

You can absolutely run the same map for the exact same setups on different vehicles. How do you think every car gets tuned from the factory? The RX-8 is absolutely not any more special or dificult than any other car in this regards. It is only the stock ecu itself which is an issue. It's not an engine problem.


The exhaust side of the turbo has everything to do with what is going on with the intake side. Pressure is not always a constant with flow. There is more to it than this. As a generalization (not set in stone), for every 1 psi of exhaust backpressure you have, you need 2 psi of intake pressure to overcome it. Decrease your exhaust backpressure by 1 psi, you can run less boost to make the same power level. If you ran equal boost with less exhaust backpressure, you would have to retune the ecu as you would be making more power. It is not pumping air at the same efficiency and this means that you can not run the same fuel or timing. There is alot of information on this topic all over the internet.

 

With a program that adapts to the variability of the cars. You can run the same maps. There's nothing to stop you. But you get vastly different results. This is true even for totally stock 8's and has been shown many times over.

Now that I agree with. Your other post talks about the turbo working harder to overcome the back pressure. It didn't sound to me like you were talking about running less boost, it seems like you were talking about back pressure changing the compressor efficiency.... something in the statement "the differences in exhaust backpressure will effect turbo efficiency" made me think that....

 

If a turbo were setup to make equal power on 2 different cars but one had a better flowing exhaust, the turbo would be working harder on the car with the more restrictive exhaust just to make the same power. It would need more boost, which is more heat, and a faster spool rate. Compressor speed may be related to boost pressure but it is not related to power output. Boost pressure is never directly related to power output on it's own. It is also not directly related to engine stress. If we have a more restrictive exhaust, boost pressure in the intake manifold may stay the same but power will go down as the turbo isn't compensating for the power loss. You need to work the turbo harder by spinning it faster to get the same power level.

 

quick and easy.

if the exhaust flows better. the exhaust turbine spins faster at a given rpm.. also with that the intake compressor spins faster. thus more flow at the same rpm...

more flow same map would go toward lean...

beers

 

There is no variability to the cars. They are very consistent. What makes them seem like there is, is really only a variability with the factory ecu itself. That's what causes all the issues. No program adapts to a variability between cars. That would be impossible to tune and would be like expecting an ecu to automatically compensate for either a V8 or a V6 engines differences compared to each other if we were to install the same ecu between either one. Isn't going to hapen.

 

That would only be true if there was no wastegate.

 

sorry,

before the waste gate opens.... does not the waste gate open at a set psi...not flow volume????

i am trying to get this back from years gone past...

beers

going to make a cocktail now

 

Oh I see. That explains all the different results that people have with the same hardware, even when removing the factory ecu from the equation using the Interceptor.


Really? I guess I would point out that the fuel trims are one very obvious way that the ecu changes the management parameters from the baseline configuration and adapts to that particular vehicle's characteristics.


You state that the engine is quite consistent, but its not just the engine that we are dealing with. Its a complete system. While one component might have a fairly tight distribution, the assembly of engine, sensors, flow characteristics, etc. doen't necessarily. Its just statistics. Each car is going to be different. Those differences have been documented over and over on this forum.

 

Fred -

Try moving a PCM from one stock RX-8 to another.

Allowing that they all have the same flash, why do the problems follow the engine, not the PCM?
I like what you are trying to do, but you are basically wrong.
The PCM is IDENTICAL from one RX-8 to the next (provided they are on the same EEPROM). What changes are the tolerance on the sensors, actuators, injectors and coils and a whole slew of variables on the motor itself that mostly stem from dynamic seal clearances.

 

It may be possible that there is a large deviation between the temperature sensors and mass air flow sensor used between cars that will cause these readings but the Renesis engine itself is incredibly consistent. They all make about the same power regardless of who's car it is in. It is not an engine issue.

An ecu like the RX-8's doesn't adapt to different engines. If it did it would adpat to being installed on a 4 cylinder. It can't. It try's to look at it's readings that it receives and maintain a certain value according to what it is tuned to do. That is not adapting to a different engine. That is making your tune work properly according to what you see. This goes back to the above statement. If there is a low tolerance for consistency between sensors, this will affect what the ecu sees and it could be interpreted as a deviation between engines when it isn't an engine issue at all. These engines are extremely consistent. There are no issues with them. If there are still issues, check the sensors or the ecu's. If the ecu's check out consistent, check something else. Don't blame the engine though. That will never fix anything as it isn't the problem.

 

It makes sense that the variability is in the engine and the sensor readings that the ECU gets from that engine. It does not make any sense that the ECU's are different. Programming is programming. With the same flash...the programs are the same..........

I would think that the ECU gives different sensors varying amounts of importance...and thus variability in specific sensors would have larger effect than others on the output of the ECU....

What sensors seem to be most important ?? MAT IAT Baro ECT TPS?? I would expect few variables in the Eccentric shaft sensor...it will either work or not....

 

Mazda sourced the MAFs from more than one vendor, so that might explain the HP differences between cars. Even though they're built to the same Mazda-supplied spec, variations in manufacturing techniques, materials, etc. result in significant functional variance.

 

All of the MAFs are from Mitsubishi. They are the same MAF as on the Subaru WRX, BTW.
They do have some varying output, however.

 

functional varience of the maf has been talked about for almost 2 yrs now. It's there. Canzoomer tried dealing with it. Now whether or not this in itself causes the differances being spoke of here--probaly not. It has been shown that changing maf's between cars really doesnt change how the car runs.
Just our luck it has to be something very complex. There is something to be said about a distributor and a holley carb.
Olddragger

 

Yes. That is the point. The sensors have variations that may or may not affect the function of the motor. However, different motors perform differently regardless of their subset of sensors and PCM. This is because of some variation in the motor itself.

I preferred Carter carbs, but you haven't lived until you've rebuilt a Rochester.

 

Weber, no contest.

 

Webbers are easy to rebuild. Its synchonizing all 12 of them that was hard.

wOOt ! Two Thousand Posts!

 

I have 6X2 brls on my 275 and had 4X3 brls on my Boxer. Does that count as 12?
Or does it have to be 12 units? If so what the hell was that on?

 

I stated in an earlier reply that my nephew's car died 2 days after installing the Greddy turbo kit. He did not have it tuned. It was towed to the Mazda tuner afterwards where it was found to have been blown from an extremly lean mixture. He did have an aftermarket exhaust on the car. If anyone is reading this and is thinking about installing a turbo kit without having it tuned please think again. This is going to be about a $6000 dollar lesson.

Gunnar

 

$6k?!? Just how bad did he mess it up?

 

2.5k for a new motor and 3.5k for the install.

a fool and his money.

beers