FAST Tuners, I need some tech help

[67ragtp]

Im trying to get my engine to fire quicker cold and hot, seems like its on the starter a bit longer than I would like. It cranks real fast and voltage is good. The IAC position vs cooling temp is around 155 to 169 at 73 deg f and tapers down as temp goes up. The fuel pressure is right where it needs to be 43lbs.

Not sure what direction to go on the iac position vs cooling temp and if the blades on the throttle body need adjustment. Any advice is appreciated- Thanks Rich

[camcojb]

I would change your cranking fuel first. I usually only make one change at a time. You may have to bump it up or lower it depending on where it is now. Depending on injector size and type of induction, plus engine combo these settings can be quite different from car to car. The Mule tune has about 24 ms on the cranking fuel at your temp, and the IAC is nearly fully open, near 170 counts or so. My Camaro with the Procharged big block was much lower on both.

As far as getting your throttle blades set, this is my method. The main thing is you don't want the IAC to be opened a bunch just to get the car to idle at temp with no load. Then you don't have anything left for load situations like the a/c turning on, or higher cold idle, etc. First, get the engine fully warmed. Shut off any idle timing compensation (timing trim) and set the idle speed to something well below your desired speed and what it will even idle at, like say 400 rpm. Also make sure all the timing tables around the idle speed are the same, so it's not bouncing back and forth between tables with different timing amounts.

Fire it up and set the throttle blade opening so the engine is at your normal idle speed, say 900 rpm or whatever it will be idling at normally. That way, the throttle body will have the right amount of air bypass to idle the engine without the IAC getting involved when it's warm. You'll then have full use of the IAC when you need it; cold start, a/c or other load kicks in, etc. Reset your TPS settings for idle, turn the timing trim back on, and re-adjust any timing tables you may have changed and you should be good to go.

[parsonsj]

Listen to Jody!

I learned my lesson on a MEFI car last year. Turn off all the compensatory tables, and get your hot start working, using the cranking fuel vs temperature table. Then get your cold start working, and set the idle speed with just a touch of IAC. Then bring in the timing tables, and last: bring in the CTS compensation. If you try to get it all working at the same time, you'll be in an endless tail-chasing game.

[67ragtp]

Thanks Jody, it looks like I have 42ms @ 73 deg f , its a normally asperated SB engine with a small hyd cam and big cubes 427 inch. Which direction Do you think I should go?

Thanks again Rich

[parsonsj]

Rich,

You didn't ask me... but I think 43ms is too high. What size injectors do you have on the car? Does your car seem "loaded" when it does start (lots of black smoke out the tailpipe)?

[67ragtp]

John, They are 42lbs injectors, cam duration 244/252 @ .050 and 112 lsa. Doesn't really seem like it fires black smoke.

[camcojb]

Originally Posted by 67ragtp

Thanks Jody, it looks like I have 42ms @ 73 deg f , its a normally asperated SB engine with a small hyd cam and big cubes 427 inch. Which direction Do you think I should go?

Thanks again Rich

Originally Posted by parsonsj

Rich,

You didn't ask me... but I think 43ms is too high. What size injectors do you have on the car? Does your car seem "loaded" when it does start (lots of black smoke out the tailpipe)?

yeah, looks way high to me. Does it start easier if you crack the throttle slightly? I'd start chopping it down a lot, mid 20's maybe to start.

[supremeefi]

Originally Posted by camcojb

The main thing is you don't want the IAC to be opened a bunch just to get the car to idle at temp with no load. Then you don't have anything left for load situations like the a/c turning on, or higher cold idle, etc. First, get the engine fully warmed. Shut off any idle timing compensation (timing trim) and set the idle speed to something well below your desired speed and what it will even idle at, like say 400 rpm. Also make sure all the timing tables around the idle speed are the same, so it's not bouncing back and forth between tables with different timing amounts.

Fire it up and set the throttle blade opening so the engine is at your normal idle speed, say 900 rpm or whatever it will be idling at normally. That way, the throttle body will have the right amount of air bypass to idle the engine without the IAC getting involved when it's warm. You'll then have full use of the IAC when you need it; cold start, a/c or other load kicks in, etc. Reset your TPS settings for idle, turn the timing trim back on, and re-adjust any timing tables you may have changed and you should be good to go.

Wow, and the Accel gets a bad wrap for being "hard to tune". At least on that you simply do "Forced Timing" so it holds it at any rpm etc. Then shoot for IAC counts of 8-10 at idle hot with no load. A lot of the rest of the IAC stuff takes care of itself from there, geez.

Anyway, I agree with Jody on most everything but a couple things to remember. I like a little IAC at idle when hot, sometimes it will decel a little better. With a cam that size the IAC isn't really stabilizing the idle anyway, your spark control is taking care of most of that.
Also your starting fuel will bleed over into your initial running fueling, keep that in mind.
And if possible, turn the key on, let the O2 heat up and then try to fire it while checking your air/fuels. Yes your fuel pump will cycle but it will restart the second it sees an ignition signal. That may help in directing as to which way to go. I agree, 42ms seems excessive.

[camcojb]

Originally Posted by supremeefi

Wow, and the Accel gets a bad wrap for being "hard to tune". At least on that you simply do "Forced Timing" so it holds it at any rpm etc. Then shoot for IAC counts of 8-10 at idle hot with no load. A lot of the rest of the IAC stuff takes care of itself from there, geez.

Anyway, I agree with Jody on most everything but a couple things to remember. I like a little IAC at idle when hot, sometimes it will decel a little better. With a cam that size the IAC isn't really stabilizing the idle anyway, your spark control is taking care of most of that.
Also your starting fuel will bleed over into your intitial running fueling, keep that in mind.
And if possible, turn the key on, let the O2 heat up and then try to fire it while checkng your air/fuels. Yes your fuel pump will cycle but it will restart the second it sees an ignition signal. That may help in directing as to which way to go. I agree, 42ms seems excessive.

the way I described has always ended up with some IAC at idle for me. I agree, you want a bit, just not half or more of your adjustment range being used up just to get it to idle when warmed up. And Accel was harder to tune for me than any other system I've tried (Gen VII anyway). Does not make it bad or not capable.

[supremeefi]

Originally Posted by camcojb

the way I described has always ended up with some IAC at idle for me. I agree, you want a bit, just not half or more of your adjustment range being used up just to get it to idle when warmed up. And Accel was harder to tune for me than any other system I've tried (Gen VII anyway). Does not make it bad or not capable.

Yes I know I hear that sometimes. But I gotta tell you, now that I've done both the XFI is cumbersome to me. There are whole lot more viable shortcuts on the Accel than the XFI. And I still think the software on the Accel is head and shoulders above the XFI, especially on the 3D graphs.

With the Accel, I've just always adjusted the throttle blades so that I get an IAC count of about 8-10 out of a possible 100 hot in neutral, done.
Having to turn this and that off, changing your spark table, that's a hassle. That's just one reason why I'm so amazed that the Accel has gotten such a bad wrap from time to time.

Oh well it is what it is I guess. Best of luck 67ragtp.