Hey, I was reading this link tonight, and in your first post you talked about IAC counts and setting them for the 10-40 range to help with the "tip in stumble" seen with bigger injectors. I think I may be having this problem, and am wondering if this may be it:

When in low rpm, all gears, as I roll into WOT, I get a split second hesitation. It just cuts, then comes right back. I've logged several of these incidences on datamaster, and Alvin@Pcmforless and myself can see nothing at all wrong with the car. FYI, I've got 30# SVO's and ported heads/224/230 cam. This isn't the same car that you helped me with before, it's my other one. Anyway, does this sound like the "tip in stumble" that you mentioned??

Unfortunately, I can't do anything with the car until I return from the mid east in mid october, but any guidance you could give me would be greatly appreciated. I'm really hoping that this is the problem. I do have my laptop with me with several of my datamaster logs on it that I'm going to take a closer look at.

When you said to set the IAC counts, how would I go about this with tunercat???

Thanks!

 

Well, by tip in I'm talking about going from no TPS (or VERY little) to 1/4 throttle or so.
You can even feel it just revving the car in park.
It's just this slight hesitation before the engine revs.
Is that what you're experiencing? Doesn't sound like it.

If you want, send me the datalogs and bin file and tell me what to look at/for.


Sorry I didn't catch this sooner...my beeper didn't go off

 

I really think this can be addressed with the VE tables but have never tested it. All you non believers.

Jeff D.

 

Unless you are non MAF, VE tables will not work. They are a backup in case the MAF fails, nothing else in cars that have them. The computer has no reason to reference them since it estimates its air flow from the MAF.

Ben

 

I dont think their is any evidence of if thats true or not. Larger cams have some reversion from overlap and some of this fuel goes back into the plenum and is sucked into a different port. Cause of Split BLMs?? This adds to the rich mixture that many see with cam swaps I believe. Changing the VE tables in the low RPM low MAP regions would seem to help this. I wish I know if someone has tested it.

Jeff D.

 

Before I modified my MAF tables (back when I was green) I tried VEMaster thinking that was my answer. With ever iteration of the program, the VE's were farther away from stock with the BLM's still in the exact same area.

I have tested it and I know for a fact VE (on my car, won't answer for yours) is not used.

Ben

 

Dan, that's probably not my problem then. I get it pretty much at any speed, low rpm right when I roll it to WOT the car cuts. And I mean CUTS out. I'll email you a datamaster file later on today (I don't have my laptop handy right now) that has several of these "anomalies" that were purposely induced by me for the sake of the logging. Thanks!

 

Wanna find out if the ve tables do anything in your car?
Set them all to 0 or 100 or something and see what happens. Pretty easy way to test.

There have been people that have tested this and have found that it didn't change a thing.

 

i wouldnt have even mentioned this but i noticed your list of mods. when i installed my 30# SVO injectors, my car did the exact same thing and still does. i installed them before my cam and made all the necessary adjustments like offsets and injector constant. it seems to happen more when the car is cold but the hesitations definitely didnt exist before my injectors were installed.

 

How did you alleviate this problem?? I really need to get rid of is since it's a real annoyance.

 

can someone tell me how to lower the IAC counts using tunercat.

 

im not saying our problems are from the same source.. we just have a slight similarity in mods. i have not yet been able to fix mine either unfortunately. one of these days i might throw in some 24#ers to see if my hesitation clears up.

 

What I have heard is that the hesitation is caused from the larger injectors, and that a fix would be to program in some more IAC counts. As read from that other post I linked at the top at least. However, I haven't been able to verify this as I'm 1/2 way around the world from my car right now.

 

i believe a more reasonable fix would be to adjust the injector offsets or PE table b/c what it appears to me is happening is an overly rich condition the instant you hit WOT. i dont have tunercat on this computer im using at the moment or id check but i believe PE correction factors typically start at 2000 RPM instead of the bottom of the table which is 400 or 800 RPM... at least mine is "0" until around 2000 RPM. so if you were running rich at 2000 RPM and had to adjust the PE to raise your AFR then its probably save to assume that degree of correction may be needed even lower where the current values read "0" or no correction... the same area where the hesitation occurs.