Xterra supercharger on a VG30 project

[hoov100]

The Z31 turbo ECU is more than capable of adjusting for them. You can make anywhere from 170whp to 260whp on the stock Z31 ECU, and it'll still be rich as a pig at high RPMs in boost. But thats the issue, is its rich as **** and can't be relied on for the most power you can get.

 

Did you change the MAF yet like I told him to to tell you before, and like others have told you? Just curious how this thing is coming.

 

What does this have to do with HP? the ECU is tuned for stock cams, going with a higher lift and/or a longer duration will throw that tune off. No matter how much you change the timing, it will not correct the tune.

[Tony D]

Is there any way of telling which are low and which are high?

Jeremy

 

Multimeter.

[JHine5588]

I never thought of that Tony... Guess I figured the signal was the deciding factor, not the actual injector, but it does make sense!

 

Hopefully any issues with timing and all of that will be fixed with the chip. I need to write down the serial number and get a hold of JWT to find out what exactly is done to it. It has some letters that are circled but I couldn't figure them all out. All I do know is the "T" wasn't, while the "F" and "C" were, I think... telling me Timing is stock where Fuel and Cams are tuned. I'm not sure if I'm accurate in my guess but it would make sense.

 

 

 

Jeremy

Edited October 13, 2010 by JHine5588

[michaelp]

What does this have to do with HP? the ECU is tuned for stock cams, going with a higher lift and/or a longer duration will throw that tune off. No matter how much you change the timing, it will not correct the tune.

 

Because the Z31 doesnt have a POS vane air meter like 280Zs and 280ZXs. Its a hot wire MAF, and can compensate a decent bit for changes in AIR FLOW and MASS. With cams, you'll have more air, which is MAF will meter and the ECU will compensate for by selecting the proper load factor. If my ECU can handle a jump from 6.8psi (170whp) to 14psi (260whp) and not run lean, and still run rich as ****, then it can handle cams that are going to add a max of 10-20hp at the FLYWHEEL. The ONLY issue you'll run into with cams not running properly on the stock ECU is if they're designed to work past the 6400rpm rev limit, in which case you have bigger things to worry about than your rich as **** stock tune...like the bottom end and the fact that the VGs stock oiling system us garbage.

 

FWIW, I've run a Z31 with aftermarket cams and the stock tune, at more than stock boost. It ran fine, and the AFRs were still ridiculously rich and safe. Car made more power with the cams than they did with the stockers. So, someone needs to learn how MAF cars work.

Edited October 13, 2010 by michaelp

[JHine5588]

Yeah, MAF really can compensate a great deal when it comes down to it. The only time you start to have problems is when you up the boost and/or displacement a LOT to the point the VAF can no longer read, then all you need is a new sample tube.

 

It is way more lenient than a MAP setup because MAP sensors have a predetermined limit, most factory ones stopping at 14.7 psi, 1 bar. In fact, I believe the limiting factors in any MAF setup is fuel due to running out of injector size or fuel pump.

 

VAF sensors are also like a MAP sensor in that they have a limit as to how much they read. In fact I can only think of 2 reasons why a MAP sensor would be used and those are they require 4 things to run: a vacuum line, power, ground and a signal wire. A MAF and VAF both need to be plumbed into the intake track.

 

 

 

Jeremy

[michaelp]

Yeah, MAF really can compensate a great deal when it comes down to it. The only time you start to have problems is when you up the boost and/or displacement a LOT to the point the VAF can no longer read, then all you need is a new sample tube.

 

It is way more lenient than a MAP setup because MAP sensors have a predetermined limit, most factory ones stopping at 14.7 psi, 1 bar. In fact, I believe the limiting factors in any MAF setup is fuel due to running out of injector size or fuel pump.

 

VAF sensors are also like a MAP sensor in that they have a limit as to how much they read. In fact I can only think of 2 reasons why a MAP sensor would be used and those are they require 4 things to run: a vacuum line, power, ground and a signal wire. A MAF and VAF both need to be plumbed into the intake track.

 

 

 

Jeremy

 

I think the record for most power on the stock Z31 MAF is 440whp atm, but thats with a different tune, larger injectors, rescaling the MAF, etc.

[BLOZ UP]

MAP sensors can't correct for changes in flow. Megasquirt, when setup to use a MAP sensor, uses the MAP, RPM, and a predetermined VE to inject fuel. If your engine flows more at the same pressure, you'll run leaner.

 

The VE is what accounts for engine flow/efficiency. This is why, on a map car, you should to retune whenever you change something. On MAF cars, it retunes itself because it can sense the increase in flow. Up to a point.

[JHine5588]

This is why, on a map car, you should to retune whenever you change something.

 

Including elevation...

 

 

 

Jeremy

Edited October 13, 2010 by JHine5588

[michaelp]

Including elevation...

 

 

 

Jeremy

 

Most map cars use a BARO sensor to determine atmospheric pressure for elevation change, or use the MAP sensor as a BARO sensor prior to startup to determine elevation.

 

BLOZ UP, thats exactly right, which is what we were trying to explain to hoov.

[JHine5588]

BLOZ mentioned Megasquirt, where you can turn the option of baro correction off, which simply just uses the MAP sensor as the baro upon initialization.

 

 

 

Jeremy

[michaelp]

BLOZ mentioned Megasquirt, where you can turn the option of baro correction off, which simply just uses the MAP sensor as the baro upon initialization.

 

 

 

Jeremy

 

YUP, thats actually exactly how modern Nissans handle elevation. Modern Nissans utilize MAP and MAF, and use the MAP upon initialization for a BARO reading to determine altitude. Combined with MAP, BARO, and the MAF...they can adapt GREATLY for changes, and stay within optimum AFRs for power. I've seen A32 maximas boosted without tuning it, just forcing air into the engine, blow-through MAF style.

[JHine5588]

I wonder if the supercoupe T-birds do the same because they have a MAP and a MAF too... I've always thought that was very weird.

 

 

 

Jeremy

[mario_82_ZXT]

Measure the resistance.

 

If you want to use low-z injectors with a high-z ECU, you need injector resistors, that you can either make or use from a number of Nissans.

[JHine5588]

Yeah, I remember doing that with a megasquirt build I was working on. It just didn't click that the injectors themselves are what's either high or low impedance.

 

 

 

Jeremy

[JHine5588]

Well, a few things have progressed. First of all the MAF fixed the idle problem... Second I found out that the injectors in the car are low impedance yet the turbo ones I have are high. This explains why when they were in the car with the stock ECU they weren't firing. Now, I just need to figure out if the chipped ECU is for high impedance injectors and if so, I'm set.

 

 

 

Jeremy

[michaelp]

Do you know what year the JWT ECU is for?

[JHine5588]

Straight from the JWT guy in an email "The ECU core part number is for a 1986 300ZX non-turbo, M for manual transmission and F for federal emissions spec. It is programmed for use with stock non-turbo 185cc injectors and stock OEM non-turbo MAF sensor, speed limiter removed, rev limiter moved slightly higher and for 91+ octane fuel."

 

In other words, not at all what my buddy thought it was, nor what I want!! Anyone have a turbo ECU around for high impedance injectors??

 

 

 

Jeremy

[JHine5588]

All 84-87 injectors are low impedance, with 88-89 being High.

 

Is there a difference in resistance between turbo and non-turbo? If I compare the stock 87's to the "turbo" ones that he bought the "turbo" ones are a significantly ohm reading, like triple. I was getting around 5 with the stockers and about 15 with the "turbo" ones. Also they're red in color where the stockers are white.

 

 

 

Jeremy

[JHine5588]

I think we'll be going the Nistune route which means this 86 JWT ECU is for sale. Anyone interested?

 

 

 

Jeremy

[michaelp]

The turbo injectors are 88 or 89 turbo, then, not 84-87. NA or Turbo 84-87 injectors should be low resistance (~5ohms)

 

If the JWT ECU is programmed for NA though, not turbo, you can't use it anyways. NA uses 180cc injectors, if you're using turbo they're 260cc (idk where the JWT guy you talked to got 185, but they're 180...)

 

I would suggest Nistune with some 450cc injectors just to play it safe, then you can run a smaller pulley on the SC more safely too. DSM black or blue top injectors are great 450cc's for the Z31. You will need aftermarket fuel rails, or 84-86 single-feed fuel rails though.

Edited December 1, 2010 by michaelp