I have done the math and set my constant. Now it wont idle. Does anyone know what I should do with the VE tables and the spark tables? I have the Supercharger reflash and stepped up to 48# injectors from the charger injectors. The car is a 2002 2.4L 5 speed with a t3 turbo .48/.42 50 trim.

Ok, better double check some things first. Some of this info I've seen, but I don't know off the top of my head.

What is the fuel pressure for the 2002 engine when stock? What is it at now?

What are the 48# injectors originally from, or, do you happen to know what pressure they're rated at?

I seem to remember that the some Z24's use higher fuel pressure than most cars. This will make a difference.

-->Slow

Increase your Idle VE numbers until you get a decent idle, thats probably where you are having the most issues. A good starting place is to look at an idle VE table from a non-s/c 2.4.





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They are Accel 48# injectors. Rated at 43.5 psi. The car is running 50 at idle and 55 WOT. I just ordered an AFPR from Summit. Im going to turn the pressure down to about 43.5 when I get it. When I did the math for the constant I converted the flow rate of the injectors according to the 50 and 55 psi and came out with. 51.46# at 50 psi with a constant of 0.18864. and 53.97# at 55 psi with a constant of 0.17987.

Quote:

When I did the math for the constant I converted the flow rate of the injectors according to the 50 and 55 psi and came out with. 51.46# at 50 psi with a constant of 0.18864. and 53.97# at 55 psi with a constant of 0.17987.

This looks good. Have you run the engine using the S/C calibration and 30# injectors? Did it idle well? Did it run well? IOW, is that calibration a reasonable match for your current engine?

When the injector constant was set to .29 did it idle too rich? (I know the WOT AFR was too rich).

As you get into changing VE, you also run into other tables that need tweaking. It's best to avoid that if possible. But if the S/C calibration is a poor match for the engine you'll end up adjusting VE anyway.

-->Slow

Your car won't idle because it is still dumping too much fuel in. I know you adjusted for the higher fuel pressure, but going by Shifted's formula, your constant is too high it should be .10125. I have 30lb injectors on my car and have the constant set @ .162 and she runs fine




Jason
99 Z24

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Johnny Mack Turbo Systems
Engineered Performance

It ran mint with the reflash and 30# injectors. It got a little lean in the top end. That is why I bought the HPTuners and the 48# injectors. I have only started to have a problem once I put in the injectors and started changing the constant. With the constant set to.29 it seams to idle rich when it is cold and then it idles OK but a little choppy. when I come to a stop light and it idles down sometimes it wants to stall. I had this solved with the reflash and the 30# injectors by copying and pasteing the Idle VE table from the 2.4 N/A Flash.

Do the injectors sound very different with the small injector constant... do they seem to be louder, ticking less often?

A 48# injector is fairly large for the displacement of the engine. Having sequential injection control should make it better than with older batch fire systems. It's a little tough to get a 45#/hr injector to idle with batch fire mode.

I'm wondering if the pulsewidth needed is so small the injector won't control fuel accurately. That could explain why setting a larger constant results in reasonably correct fuel, while a smaller constant results in way too little fuel. I have run into that problem before. When it happens the usual cure is to lower the fuel pressure.

More later, gotta go fix cars.

-->Slow

I will be getting my adjustable fpr tomorrow. Turning it down to 43.5psi at WOT. Or should I set it at 43.5 psi at idle?

Pressure should be set with key on, engine off.


You should use the last good calibration you had in the car. If you were using the S/C cal with patched idle VE and it worked, start with that one. Then you've got a comparison to the way it ran before.

-->Slow

hows it going for you? Get it going yet?

On the Accel Injectors...... I tried using some smaller ones back in the day, had the same issue...... check the spray pattern...... I believe that was the problem we had....... just something to look at, if all else fails.




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