ROTORHP

Has anyone ever messed around with this rather than buying a Pettit ecu? I have a guy in town that can apparently tune stock ecu's. He has a chassis dyno in house and modifies GM's and Fords but I don't know if I trust him with my baby.

I was also told that this guy(with the help of Adam @ Rx-7 Specialties) was able to get 40 hp out of an Rx-8, just by tuning the ECU. I was planning on getting a PFC but I could use this to buy me some time and keep my car running healthy. Is it worth the shot or should I stay away? How much power can the stock ECU be capable of handling?

Thanks for any answers.

Kento

Once you get to the point where the stock injectors can't handle the fuel delivery load (generally acknowledged to be around 14-15 psi on a stock port with the usual bolt-ons), you are beyond the capabilities of a remapped stock ECU. Don't try to judge the capabilities by horsepower, as each car is different.

If your friend doesn't have any experience modifying the ignition and fuel characteristics of the FD, I'd recommend against trying this route.

Mahjik

iTrader: (1)

I don't think it's that simple with the FD3S ECU. Pettit, M2 and the others add a daughter board into the stock ECU so they can reprogram them. They wouldn't go through all the added labor/expense if it wasn't absolutely necessary.

MazdaRx7Racer4Life

In other words, it costs more for a reason, if not everyone would just remap their stock ecu.

ROTORHP

Oh so there is no way a guy can remap the single factory board that is in the ECU by itself without adding a daughter board? Even if it was a little bit?

I have some mods(sig) and Adam told me that I need to do a fuel mod. I am going to get a Cosmo pump or Nippondenso over the winter, then I was thinking to alter my ECU. If I did the pump, would it compensate enough for my mods without doing the ECU? I am thinking about an M2 cold air box as well.

The reason I am also considering this is because not only do I get dyno time, I then know that my ECU would supply enough for my engine, and I could probably get a deal on doing it. Remember I am in Canada.....


Thanks again

MazdaRx7Racer4Life

Its not that you Can't, Im sure you can, its that its not recommended and probably not as reliable as an actgually piggyback or standalone

Mahjik

iTrader: (1)

Well, like I said, there must be a reason all the other upgraded stock ECU's ALL have a daughter board mounted in them.

I have no first hand knowledge of it, so I guess you can always take your car over there to see if he really can reprogram the stock unit. However, I would go ahead and prepare yourself for disappointment.

Kento

The memory chip that the ECU uses to determine fuel/ignition curves is a "read only" memory chip. That means the chip itself cannot be changed. Installing a "daughterboard" onto the main "motherboard" basically is stepping in at circuit board level and altering the memory with another ROM chip.

ROTORHP

Mahjik, what about the pump? Will it help me enough until I can get a PFC then?

Mahjik

iTrader: (1)

The fuel pump alone will do nothing for your A/F mixture. The injectors and FPR will still be sending the same amount of fuel with the stock pump or upgraded fuel pump.

You only need to upgrade your fuel pump when you are losing fuel pressure (i.e. your car is requiring more fuel due to larger injectors or a RRFPR and your fuel pump cannot keep up with the new demand).

ROTORHP

Gotcha.... should of thought of it a bit myself.

Kento, thanks for the info. Would the Rx-8 ECU operate in the same fashion as the 7's? If it does, maybe he has ROM boards that he can program?

yzf-r1

iTrader: (1)

I heard a rumor Pettit is working on a new ECU allowing use of larger injectors....can anyone confirm or deny this?

Mahjik

iTrader: (1)

I can confirm the rumor is a real rumor. I have no idea if it's true or not, yet. Hopefully a certain member on this forum will be able to tell us in a month or two.

ROTORHP

Can't you use a larger injector with the Pettit ECU's now? They program parameters for what upgrades you have don't they?

Kento

No, the RX-8 ECU is a 32-bit unit with a much higher memory/computational capability, while the FD's (since it was designed way back in the early 90s) is only an 8-bit unit.

Mahjik

iTrader: (1)

No, you can't use larger injectors with any of the reprogrammed stock units (M2, Pettit, GForce, etc).

ROTORHP

I see...while we are on the subject of injectors, how much rwhp can the factory injectors provide at a safe duty cycle?

Mahjik

iTrader: (1)

Duty cycle is not as important as A/F ratio. I've seen the stock fuel system go around 360rwhp (using a Pettit ECU on a ported engine). I really haven't seen a programmable ECU max out the stock injectors as people usually go to a programmable ECU just so they can upgrade the stock injectors.

ROTORHP

You still don't want to run your injectors at max though am I right? A/F ratio is obviously the most important. Yikes...360rwhp. I am hoping for about 330rwhp. So I shouldn't have a problem using the stock sizes and getting the correct A/F ratio? I do plan to keep my twin setup(sequential as well). Thanks for all the info.... you've helped me huge...again

Mahjik

iTrader: (1)

Check this thread about fuel system upgrades:

https://www.rx7club.com/showthread.p...hreadid=259912

It has a lot of good info, I'm just not in the mood to retype it right now.

330rwhp on the stock fuel system shouldn't be a problem.

ROTORHP

Wade's site has some good info that totally makes sense. Thanks for the thread link and all the info

j9fd3s

iTrader: (3)

the reason you can reprogram the gm and ford ecu's is beacause the code is well known, along with the other stuff about the fd being read only

ROTORHP

The guy must know some codes however since he worked on a Rx-8 ECU....thats what I want to know....is that ECU read only? What did he do to alter it?...... hmmm I guess I could phone him

Mahjik

iTrader: (1)

For starters, the ROM or chip has to be reprogrammable (i.e. the way computer BIOS chips can be reflashed with new/different code).

If the chip is not flashable, then you can't reprogram it. I would assume most if not all new cars support flashable chips as they (and the supporting hardware/software) are not nearly as expensive to use these days as they were in the late 80's and early 90's.

So, I would wager that the stock ECU is not flashable, hence the reason that Pettit, M2 and the others remove the chip to install a daughter board with a different reprogrammed chip.

ROTORHP

Ok, we dicussed the daughter board stuff allready but now you confused me Mahjik. First you say that most if not all ECU's would be flashable that are now made in new cars , then you bet that you cant flash them? WTF? Are you refering to rx-7 comp again when you say this?