Timing Advance ?

[carmat76]

I am running a '91 T with a 60 trim T3, WRX TMIC with water spray, 550cc 5th injector above 13psi (injector flow and trigger psi adjustable), Wlabro FP, 4.10 gears with rear lsd, 195/45/15 wheels (for the gearing), Auto tranny with cooler.

Tuning for the 1/8 mile drags using EGT sensor.

I used the standard diode trick on the MAP sensor and I want to do the same on the MAF for advanced timing.

What MAF wire do I tap into? What voltage should I target. So far, I am not getting any audilble detonation at 15psi.

I need timing advance ; )

[tris91ricer]

Whoa. I don't even think we've discussed this topic.

Good show for bringing up something our turbo guys will maybe want to think about later.

I'm going out on a limb with this one, but I believe there's a wire sensor going into the timing case that may very well be for the timing control. Wouldn't you want to alter that signal, instead of the MAF?

[carmat76]

Which wire is this? I am very interested! I thought that if the MAF reported less air flow that the ECU would maintain advanced timing longer and I would make up for the fueling with my 5th injector.

Where is the timing case?

Thanks!

[tris91ricer]

It's a wire that goes into the right hand side of the timing cover.. it's black, has a plug-type head on it..

I'm not certain that's what this is for, however, it does run into where I know the timing belt is, so it seems a logical guess.. What about controling timing via engine management? You're already running a 5th injector, why not go standalone and control it all?

[vrg3]

"Timing case?"

http://bbs.legacycentral.org/viewtopic. ... 813#107813

I hope you know what you're doing...

[tris91ricer]

I dunno what you'd call it, but I'd think a wire going into the timing cover would probably have something to do with the timing, right?

[vrg3]

Ah... Yeah... That sensor's the camshaft position sensor. You can tweak timing by messing with that signal and the crankshaft position sensor's signal. It ain't simple though -- you need a device like an S-ITC or something.

[carmat76]

VRG3: Do you follow what I am trying to do? What wire do I want to tap into with resistance to modify the reported amount of air?

Thanks!

[tris91ricer]

I don't see how mod'ding the MAF signal does anything for timing...?

[vrg3]

I follow what your idea is -- if the ECU thinks there's less airflow, it'll think there's lower load, and it'll advance the spark more.

The voltage on the signal line is how the ECU measures airflow. The transfer function is quadratic. If you're curious you can find it by searching some more.

I don't know what you mean by tapping in with resistance... I'm reluctant to give advice on this because it seems like an easy way to blow the motor up. How do you plan to tune this?

[carmat76]

Ok then... I guess I'll look for the answer in some other thread's. Just wanted to know the wire that sends the signal. I guess it's the red one with the stripe??

[rallysam]

I'm a noob, but it seems like lowering the MAF signal would do a lot more than just adjust timing... like make you run lean for example

[greg donovan]

I'm a noob, but it seems like lowering the MAF signal would do a lot more than just adjust timing... like make you run lean for example

thats why he has the 5th injector.

i still have my doubts as to the success of this plan as well. but i say go ahead and try as long as you can afford a rebuild on your engine.

[vrg3]

Follow the link I gave you, carmat76. I have already posted a very clear description of which MAF wire is which.

Wait -- what red wire with stripe?

Clamping the MAF signal will absolutely make you run lean unless you do something about it. And I'm not sure that a pressure-triggered fifth injector will do it. Though I guess if driveability isn't needed it might be okay.

Good luck!