z31 ecu mods?

[ZR8ED]

Hey guys.

 

I'm looking at upping the boost in my z a few more psi. I'm running 11 psi now and am running an a/f ratio of 13:1 (cutting it close on safety I know) I have a large i/c and a free flow exhaust and a larger throttle body, and a t3/t4 hybrid turbo high flow fuel pump and an aftermarket fuel pressure reg. I'd like to run it to 13-15 psi. if I can.

 

I have the fuel pressure sitting at or near stock. I'd like to up the fuel pressure a bit to eek out a few more cc's of fuel

 

I've been inquiring into some info on burning a new eprom for my z31 ecu. Currently the ecu is from a 1986 300zxt 2+2. and it is stock. Do you think I can reprogram it to give me some more fuel from the stock inj? enough for what I want? and is it worth the effort?

 

 

 

Any ideas? suggestions. An aftermarket ecu is out of the question as well as the jim wolf setup or even the msa unit. my engine failure this summer put me way over budget for this year, and maybe next, so I'm looking at some stop-gap ideas to hold me over for a while.

[SleeperZ]

You don't need to reprogram the ECU to run more boost or fuel. Just up the fuel pressure to get a better mixture at WOT, the ECU will adjust the midrange for you. You may be approaching the limit of the stock injectors if you raise the boost much more - I believe I was pushing it running 14 psi with stock injectors and a similar turbo/IC (but I'm 5800' elevation, equivalent to 12 psi at sea level).

 

I am now running 16 psi with SVO 370cc/minute injectors and 43 psi static base fuel pressure, and that A/F ratio is running about 12.0-12.5 to 1. You can see my dyno numbers in my signature; I have not made significant adjustments since. I am able to make the SVO injectors act like stock by installing the MAF hot wire element in a larger intake (3-1/2" OD exhaust pipe). I even passed Colorado emissions testing with no adjustments on this new setup.

 

All this on a factory '86 turbo ECU. If you are still interested in reprogramming the EEPROM, I understand it is somewhat complex - I have the added benefit of less intake restriction from the stock MAF housing. Bernard may read this and post his work on the subject, but the bottom line is Jim Wolf earns his money on modified Z31 ECUs.

[yo2001]

Mine is set 12psi of boost with 44psi static fuel pressure on 87 turbo ECU. (I'm newer than Sleeper by a year Still both 8bit ECU) I'm running pretty aggresive timing though. 22-23deg initial

[ZR8ED]

Yea I've been talking with Bernard. That is where I got some of my ideas from.

 

I know little to nothing about stock ecu's

 

Not sure about your set up. you say your using 370 merkur inj. what are the stock inj sizes? L28 right?

 

I'm using a VG motor, and the turbo VG injectors which I believe are 330cc (can't recall for sure)

 

I kinda see what you mean about the ecu correcting the mid range. I suppose I should try upping the fuel pressure and not adjust the boost, and see how the mid range driveability is affected if at all. I have an aftermarket a/f ratio monitor that uses the stock o2 sensor. I've now learned that they are not much better than a toy, but it is better than no monitor.

 

Thanks.

[SleeperZ]

Yea I've been talking with Bernard. That is where I got some of my ideas from.

 

I know little to nothing about stock ecu's

 

Not sure about your set up. you say your using 370 merkur inj. what are the stock inj sizes? L28 right?

 

I'm using a VG motor' date=' and the turbo VG injectors which I believe are 330cc (can't recall for sure)

 

I kinda see what you mean about the ecu correcting the mid range. I suppose I should try upping the fuel pressure and not adjust the boost, and see how the mid range driveability is affected if at all. I have an aftermarket a/f ratio monitor that uses the stock o2 sensor. I've now learned that they are not much better than a toy, but it is better than no monitor.

 

Thanks.[/quote']

 

Stock VG injectors are the same as stock L28ET units at 260cc/min. That's how the initial swap is so easy. By just upping the fuel pressure, you should get safer A/F ratio, and the midrange (cruising, not WOT) will correct to 14.7. And I use a "toy" mixture meter as well - it's a good troubleshooter, and gives an indication of how the ECU is operating. I think the factory ECU is an excellent unit with the only limitation being the rev limit - good for factory cam, but not so good when you want to make power at higher revs.