jeepguy553

I finished some MAJOR construction in the Jeep today and now it is time to start really tuning things and getting it up to par. I started working on putting the OEM A/C unit I have in it too. Not gonna be fun.
Anyway, I have a Holley 670cfm TB (from an old ProJection system) I want to put on the engine (AMC 360 with TBI and 1228746 ECM). The questions are:
1.) Should I put it on now or wait till after I get a good tune with the OEM GM TB? I was thinking that I could just put it on and tune the thing like that...or is that a really stupid idea?
2.) What kind of tuning issues will I come upon with the install of that TB? Will it be mostly VE% table work?
3.) Is it REALLY worth the trouble to drill/tap the TB for the IAC?
4.) Will I need to change the injector pod and FPR assembly out in favor of the one off the GM TB?
5.) If all I have to do is tune VE%, where would a good starting point be? Could I bump the whole VE%1 table up by a percentage that represents the change in flow surface area (because of the larger bores in the Holley TB)?
Thanx in advance guys!

Grumpy

I try to do one thing at a time. I'd suggest using the stock TB and get things at least real close, so you have some idea of where to begin, and if things don't go right, you can just pop the stocker back on while you try and figure out what's going on wiht the 670.

The IAC is getting to be a real love/hate item it seems. When it's right it's nice, but it can be a real headache getting there. On my car the stock start posistion is 175. As things are now, anything over 55 and it will hardly idle when cold. I've had to take out all the spark advance at start-up, and first run, to even get it to try and act like it has a choke. While it will idle perfectly on a cold start now at 900 RPM it took ALOT of work to get that. And then I've had to kill the T/F, to get rid of a slight surge when the IAC opens, and close. Yet, I have got to figure out something to help prevent the stall after burn out syndrome......

jeepguy553

So I could get rid of stuff like IAC Park and the others and it would be okay. What about the throttle follower stuff? Is there a way to zero all of it out?

JPrevost

No suprise here, I agree with Grumpy, use the stocker first.
The IAC TF steps can be limited in the ecu file you have. It's a constant 13th from the bottom of the constant list, "Max IAC throttle follower steps." Stock ANLU is 96 steps, I've had mine at 36 now for about a year and have had great success. This is with a Holley 670 though, so the IAC operates a little differently than the stocker. I believe the Holley IAC flows more air with each step, or it might just be me.
You can also limit the max IAC steps (constat is right about the TF limit). You should keep the Max steps above the max TF steps. For a while now I've gotten the hold on how the IAC operates making it easier to tune. For a new tuner I'd disable the IAC by setting max to 0 on a warm engine in no traffic and try and be as smooth as possible with the throttle (no hard lifting) which means left foot brake! This was one stumbling block when I had my fuel pressure at 28 psi and the IAC fuel adder when opening was an "on time", not based on inj constant.... hence some low throttle issues never seemed to go away, now it's gone .

jeepguy553

Jon, my setup isn't gonna be direct from Holley. I will be using the stocker IAC on the Holley ProJection TB. I am going to drill and tap the IAC boss that is already there as a blind casting. Will that make a difference in how the IAC works?
So for my initial tuning (I am a newbie of sorts) I should completely disable the IAC by setting Max IAC Steps to ZERO in my .BIN. I just looked at it (it is a special .bin from another member) and the Max Steps read 191 (0x0532, $BF value). I can take them to zero, no problem. What you are saying about the TF is a little confusing, though. I found that one as well (0x0538) and it is set to 100 ($64). Should I zero this one out too? Will this make my engine croak if I floor it at a light?