Help with Bosch 1600cc Idle
Thread Starter
Joined: Nov 2004
Posts: 1,273
Likes: 3
From: Rochester, NY
Help with Bosch 1600cc Idle I went ahead and got some Bosch 160lb injectors with a Versafueler driver box. I'm running twin Walbros with a boost referenced regulator set at 4 bar base. 8AN feed, stock feed as return. This is in a 2004 GTO. I am running E85.
So far, the leanest I can get my idle is about 11.5:1 (gasoline AFR). I've lowered the Min Pulse Width to 1.3ms. If you look at the flow graph of these injectors, if you allow then to go below 1.3ms, they can start doing some funny things.
Anyways, I also tried adjusting the Short Pulse Adder in the 1-2ms range. I've lowered them by about 80% now and while it helps, it's still very rich. If I zero out the Short Pulse Adder altogether, the damn thing doesn't even hardly run.
One thing I haven't played with yet is the voltage offsets, both the "Flow Rate Modifier vs Volts" and the "Offset vs Volts vs Vacuum". I'm thinking this might be where some of my problem lies. I've noticed that with low load on my electrical system, the car runs MUCH richer than when there is a load (such as fans on, lights on, etc). I'm talking like 2 full points here.
Now I know some people are going to say just deal with the shitty idle, but I know I can at least get it slightly better. I can't seem to find much offset data for these injectors.
Can anyone shed some light? I want to start WOT tuning
Thanks,
Adam
So far, the leanest I can get my idle is about 11.5:1 (gasoline AFR). I've lowered the Min Pulse Width to 1.3ms. If you look at the flow graph of these injectors, if you allow then to go below 1.3ms, they can start doing some funny things.
Anyways, I also tried adjusting the Short Pulse Adder in the 1-2ms range. I've lowered them by about 80% now and while it helps, it's still very rich. If I zero out the Short Pulse Adder altogether, the damn thing doesn't even hardly run.
One thing I haven't played with yet is the voltage offsets, both the "Flow Rate Modifier vs Volts" and the "Offset vs Volts vs Vacuum". I'm thinking this might be where some of my problem lies. I've noticed that with low load on my electrical system, the car runs MUCH richer than when there is a load (such as fans on, lights on, etc). I'm talking like 2 full points here.
Now I know some people are going to say just deal with the shitty idle, but I know I can at least get it slightly better. I can't seem to find much offset data for these injectors.
Can anyone shed some light? I want to start WOT tuning
Thanks,
Adam
See if the fp can be lowered by adjusting the reg. If you haven't got at least 5 psi adjustment, I'd be really suspect of the ability of that return line to handle the flow...
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I know you stated you had it set at a 4-bar base, do you have a fuel pressure gauge? ...and if so, have you checked what your fuel pressure is doing at idle?
Also, the voltage offsets are important. Adjusting that value should help you get it dialed in. I would imagine someone running that sized injector on Pump Gas would be experiencing your symptoms, but E85 usually allows for a much easier idle dial in.
Also, the voltage offsets are important. Adjusting that value should help you get it dialed in. I would imagine someone running that sized injector on Pump Gas would be experiencing your symptoms, but E85 usually allows for a much easier idle dial in.
Thread Starter
Joined: Nov 2004
Posts: 1,273
Likes: 3
From: Rochester, NY
Pressure at idle is getting pulled down like it should. I remember checking it when I first set it, but I don't recall exact pressure. I wanna say it was around 50psi at idle.
I could turn down the base pressure, but I'd like to figure this out if I could. Running 160lb injectors on 3 bar is kinda like running 120lb injectors on 4 bar. If that were the case I should have just saved a few bucks and got 120s.
I could turn down the base pressure, but I'd like to figure this out if I could. Running 160lb injectors on 3 bar is kinda like running 120lb injectors on 4 bar. If that were the case I should have just saved a few bucks and got 120s.
If you were needing the flow out of the 160#, you are getting 160# @ 3bar. The 120# @ 4 bars are flowing less than 140#.
160# @ 3 bar are enough for over 1300hp on E85 and still keeping your IDCs respectable.
160# @ 3 bar are enough for over 1300hp on E85 and still keeping your IDCs respectable.
...and I get what you trying to do as well.
But, if the pulse width at idle isn't low enough to allow you to get the idle where you want, you can bump the idle up a couple rpm to help the injectors out or lower the fuel pressure so the higher minimum pulse-widths aren't spraying too much fuel.
Like you said earlier, though, if you haven't tuned the voltage offsets, that's probably the best place to start.
But, if the pulse width at idle isn't low enough to allow you to get the idle where you want, you can bump the idle up a couple rpm to help the injectors out or lower the fuel pressure so the higher minimum pulse-widths aren't spraying too much fuel.
Like you said earlier, though, if you haven't tuned the voltage offsets, that's probably the best place to start.
Honestly with those old 160lb low impedance injectors with the driver box you are more than likely going to have to turn down your base fuel pressure to not ride the minimum pulsewidth of the injector. They are an old injector that gets very sloppy down low so it really would be in your best interest to turn down the fuel pressure to 43.5 psi base. This is even more important since you have dual walbros as the lower base pressure will aid in how much flow the pumps can actually deliver. Besides, those injectors on E85 will go the distance and more with that turbo at 43.5 psi so you would be running unnessarily high pressures for nothing. You really want to set your pressures accordingly as nothing says you should be running 4 bar just because that's factory fuel pressure.
I can make some changes to your file to assist with that and email them to you so send me your email address.
I can make some changes to your file to assist with that and email them to you so send me your email address.
Thread Starter
Joined: Nov 2004
Posts: 1,273
Likes: 3
From: Rochester, NY
So it sounds like I'll just have to deal with the sloppiness down low or else lower my fp. I'll give it a go. Let me get the info you requested in the morning and I'll get back to you. Appreciate the help everyone.
thats what i was thinking... his 160's are flowing what like 184 on a 4 bar pressure. even for a 370 that seems like a ton of fuel at idle. and im worried about tuning my 60# injectors when i get them... lol...