RB20 Tuning

zrated · Post by **zrated** » Wed Feb 06, 2008 9:18 pm

Hey Guys,

I'm tuning an R32 with a T04E turbo, aftermarket manifolds and GTR injectors (444cc) and I'm having trouble controlling the fuel...

At low boost (12 - 13psi) I can achieve my target of 12:1 AFR at high load/rpm but I'm having to fuel up the cells in the primary fuel map to around the 8.0+ mark to achieve this.

When I turn the boost up to around the 15psi+ mark obviously it's leaning out but I have added as much fuel as I can (7.38 ) and it's still running too lean. Any more fuel than that the map goes the cells go to 29.40 which I gather is the leanest of lean so I can't go past 7.38?

I've tried increasing the K-value which works but there is only so much I can increase it by before idle and the closed loop section is running 10:1 instead of a good 14.7

There's gotta be something I'm missing here... The R32 is new water for me, I'm used to tuning Z32s which are usually way too rich to start with.

zrated · Post by **zrated** » Thu Feb 07, 2008 9:10 pm

Anyone? I'm dying here!

Matt · Post by **Matt** » Fri Feb 08, 2008 12:11 am

I'll get pete to have a look at this. He was just working on one the other week (normally he only does SR20s)

Same thing as you are doing GTR injectors... thread below
viewtopic.php?t=511

PL · Post by PL » Fri Feb 08, 2008 8:14 am

I had exactly the opposite problem! Too rich on boost and too lean at idle. Hmmmm. viewtopic.php?t=511

What size resistors did you fit to make up the fact that R32 runs high impedance injectors and GTR injectors are low impedance? The car I was looking at used 10 ohms.

Regards
Pete L

Fusion Ed · Post by **Fusion Ed** » Fri Feb 08, 2008 8:21 am

Have you tried the latency? Usually that's the problem in cases like this I have found. It can take a lot of work to get the whole map reading correctly over virtual/real values.

PL · Post by PL » Fri Feb 08, 2008 9:29 am

Hey Ed,

Yeah, I fiddled with latency (increased it quite a bit actually) but I'm starting to wonder if maybe this resistor sizing may be a critical value. It would kinda make sense.

PL

Fusion Ed · Post by **Fusion Ed** » Fri Feb 08, 2008 11:48 am

Hmm resistance issue is interesting, high impedance on a low impedance setup would be fine, the opposite should as you say use resistors to stop overloading the injector drivers (and heating the injectors too much) I have to admit however that in practice I have never had a problem using all different kinds of systems and injectors.

I have however had some quite bizzare behaviour on some nissan ecus with injector scaling. Usually once a correct value has been found it all seems fine.

Unless that is a rising rate FPR is used then there is no hope.

PL · Post by PL » Fri Feb 08, 2008 12:01 pm

He he he - sounds like you have about as much time for rising rate FPR's as I do Ed!

Have you ever measured the value of the resistors that they use on GTiR's Ed? This would probably be a good starting point.

You'd think that you'd just need a suitable value to bring the total resistance up to a "normal" hi impedance injector (12 to 16 ohms?). That's why I suggested 10 ohms.

I must admit that I had a problem even using low impedance injectors with resistors to make them look like high impedance. Sure, it keeps the injector drivers happy but theoretically you're dissipating most of the power across the resistors. So I'd expect a prett lazy injector response. That's why I didn't have a problem increasing injector latency to nearly double the std value to make it run right.

I was surprised when I heard that people were doing this. But then I saw that Nissan do it on the GTiR (and others I guess) so it obviously works.

PL

GZ@hybridka · Post by **GZ@hybridka** » Sat Feb 09, 2008 10:04 am

Heres an interesting hardware solution.

http://www.jbperf.com/p&h_board/

If I recall he goes into a little bit of detail on the chips he is using.

I try to stay away from peak & hold injectors as much as possible with the nissan ecus. I havent tried this hardware addition but looks to me like it could be used easily with our ecu's.

Well, 4cyl with that board anyways.

Fusion Ed · Post by **Fusion Ed** » Sat Feb 09, 2008 11:03 pm

This is strange I have never had a problem, the GTi-R uses peak and hold injectors (of about 3.5 ohm iirc) with the resistor pack in the engine bay. (lol just seen you said this pete) However I have seen this done everywhere, many other ECUs also use resistors for the injectors. Greddy e-manage, suggests you should do this as does Omex ecus etc..

LM1949 is an interesting chip however! Injector driver controller IC, I never even knew one existed

zrated · Post by **zrated** » Mon Feb 11, 2008 9:36 am

Thanks for the comments guys... It was actually the FPCU or lack there of that was causing the issues. Turns out when a Z32 pump was installed the FPCU was removed and this caused a lack of fuel pressure at the top end.

Plugged her straight in and what was 12.1:1 went to around 9:1

PL · Post by PL » Mon Feb 11, 2008 11:04 am

Hey Gabe,

That injector driver board is an interesting option. If I was running Lo-Z injectors on an RB I reckon I'd go for that option. It's gotta give you better injector control.

It'd be intersting to tune an engine with the resistors and then fit the injector driver and see what difference it made.

PL