I am going non sequantial in a couple of weeks and I am gathering up the parts. The car has a greddy intake, greddy IC with the elbow (no bov flange), and will be complemented with a midpipe and DP along with a 3" exhaust. Clutch and other parts will also be upgraded. What bothers me is that the mechanic, a good one, told me that below 14psi, there is no need to upgrade injectors, pump or the computer. I believe him, but I have doubts about this. Any input on this. I am at 3000 ft of altitude more or less if it matters.

 

ive heard if your going over 10 psi on the stock ecu, you need to get a remapped ecu because the stock ecu cant handle the overboost situation and youll be running extremely lean and can end up with detonation from a bad A/F mixture.

 

fire your mechanic because that will without a doubt blow the motor.

 

+1


Beside you will hit fuel cut at 12 psi. from all the mods that you are listing, you will need an Boost controller to keep the spikes down or you will be buying a new motor GUARANTEE!!!! A PFC is a good recommendation also.

 

BUMP for more info. Yes, I have a Greddy Profec boost controller to aid with the boost spike.

 

are you talking 14psi of absolute pressure or guage pressure. The reason that I am asking at altitud there is a difference. I am 6k feet, colorado and guage psi of 14 is 11 psi of absolute pressure from every single datalog that I have seen on varius cars. There is an atmospheric pressure difference with altitud.

 

I question the fuel cut at 12psi. My FD is stock (meant to be stock) after purchasing it, I got a boost gauge and it was running 12 psi, spiking to 14psi, yet didn't hit fuel cut... do I come to the conclusion that I have a remapped ECU?

 

is your car a jap model? it might have a fuel cut defender installed by the previous owner.

 

A car won't hit fuel cut at low rpm @12psi. Fuel cut happens at higher rpm, when the computer can't provide enough fuel volume to keep up. You probably won't hit fuel cut in 1st or 2nd gear either.

 

Fuel Cut isn't instantanous. This is why boost spikes can be dangerous. Mazda did this on purpose as they realized that some mild spikes may occur in stock form. Owners would be pretty ticked if the car kept "hitting the wall" when a small spike happened.

The problem is that the larger spikes can occur which are dangerous. They can happen quickly during that "allowed" time and cause damage. If you are able to sustain 14 PSI, then someone has removed fuel cut from your car. If you are just spiking to 14 PSI, that should be controlled with an electronic boost controller as the stock computer will not account for spikes.

 

Mahjik, just the person I was hoping to respond I remember with my 1st 3rd gen, I did not hit any type of fuel cut and it would spike up to 15 psi for over 10 seconds, and I assume it would continue at 15 if I did not let go of the throttle.

Norbak, my mechanic, I assume is talking about gauge psi, not absolute. He is in Albuquerque, which is at an even higher altitude than El Paso. He is a competent mechanic, and many people can vouch for that, which is what bothers me cause I keep reading about fuel cut above 12psi and how dangerous it could be to let the stock ECU handle that much boost without extra fuel.

Would it be wise to buy a remapped ECU from pettit and raise the boost to lets say 15? Upgrade my fuel pump and maybe the injectors?

Thanks guys.

To control boost, like I said, I am installing the Greddy profec b spec II.

 

See attached...

 

uhh the smartest thing to do would be to get a wideband and just monitor whether the car is leaning out or not instead of playing this guessing game. they are cheap enough now that there's no excuse for not having one

 

True, that is very true. One wide band in the shopping cart.

 

While you are waiting for a wideband, I would personally take a look at the ECU. You can pull the ECU and then open it up. Look for a daughter board. If there is one then it's some remapped ECU (which one, who knows ). If you don't see a daughter board soldered onto the main board, then it is most likely the stock ECU.

 

Not a remapped ECU, or at least the previous owner did not list that in his list of mods. However, I will do a check.

BTW, I called Pettit, and asked if they had a remapped ECU and they did, but they had a 94 ECU, my car is a 95. Can my car run on the 95 ECU?

 

Some pictures of what you are looking for:
https://www.rx7club.com/3rd-generation-specific-1993-2002-16/help-bought-pettit-ecu-410197/

The main issue with the '94 is the EGR. I don't remember if the 95's have the electronic controlled EGR or not (I'm sure someone will pipe in here with the answer). If it doesn't, then you'll get an EGR code from the 94 ECU. If it does have the electronic controlled EGR, then you'll be fine.

 

Mazda should have setup up an iginition cut followed by a delayed fuel cut to prevent the lean conditions associated with fuel cut.

I'm assuming the PFC allows you to control both of these values much the way the EMS does?

 

I called Pettit again, and Cam said it would not be adviceable to use a 94 ECU on a 95 vehicle. I migh just pony up a few more dollars and get the PFC.

Now, since I am getting the PFC, and I am keeping my stock twins, would it be wise to upgrade the fuel pump and injectors along with it? I plan to up the boost to 15psi.

LOL, 1st I said I only wanted to fix things, now I have PFC, wideband, and wanting to use more boost. How easily projects change.

 

If you plan to run 15 PSI quite a bit, then yes I would recommend updating your fuel system. A simple drop-in fuel pump replacement and 4x850's would probably work well for that setup. Don't forget to budget time and money for proper tuning of the PFC.

 

Definately going to spend quality time at the dyno for tunning. Thanks Mahjik and everyone else for answering. It really helped out a lot.

 

Yeap same set up I had. I made 365 whp with a conservative tune.

 

I went from a straight reman swap out, to a ported rebuild with about 4k in goodies on top of that, and the list keeps getting longer and longer.

It's so addicting, it's scary. Atleast I'm staying modest and tasteful on my upgrades, I can't imagine how expensive it would get if I was going for big gains.

 

LOL, I know what you mean. Initially, I was just going to fix the boost problem, now I have volk wheels, tein flex, launch kit, radiator...etc...so far its over 4k...and I still need to order the4 damn clutch...ouch. Gotta pay to play I guess.

 

Yeah it is Jap model.. not sure to be honest... it was meant to be stock when I purchased it?