thunderstruck507

iTrader: (18)

My roommate just cammed his Trans Am and aside from his being a manual versus my auto and the FAST90mm setup, they are very similar.

I did a quick ballpark tune for him and it already idles better than mine, especially cold. He can remote start his car and it will run perfect...mine surges like crazy and usually I have to hold it at 1500rpms for a few minutes before it will stay running.



I'm going to save my current tune but make a copy and put everything with idle back to stock. From there I'm going to go through the same steps I did with the other car.

But due to the TB, are there extra things I should pay closer attention to? Like should I change the IAC affected area since the tb is larger? Should I pull the TB off and port the IAC bore so it flows better?

The TB was previously drilled by an old owner, I plugged the hole...should I try unplugging that?

I know tuners say the Fast tb are difficult to work with. Should I just ditch it and try to find some other 90mm tb?

T/A KID

iTrader: (12)

I say bring to NE Arkansas and I can fix it for ya

thunderstruck507

iTrader: (18)

I really do appreciate that kind of offer, but I am really trying to learn as much of this as I can. I have a lot of friends who have ls1/lqx cars and trucks and I really like being able to "pay it forward" and help them out with tuning for as close to free as I can.

So far the cars have all been stockish to bolt ons and I've not had any issues. This is the first cammed car other than mine and I was shocked at how well it idled on the stock tune and even more so after very basic adjustments to idle speed, desired airflow, and timing.

It really makes me hate the Fast tb on mine. It took me 2 weeks or more tuning it in my free time to get it to idle how it does now...and judging by the reactions I got when I posted my tune file last time...it's more a little luck with a bad tune than it is me having done a good job with it.

MMWS6

Fast 90 intake and TB? SD only or MAF and SD tune?
First simple question, if you are running with a MAF, does yours have the honeycomb in place?

thunderstruck507

iTrader: (18)

It's a 90mm intake and tb. Maf tune with gm 85mm maf and sonax airflow straightener

It's had a stock screened maf before and the idle is actually better now.

DrkPhx

iTrader: (15)

The NW 90mm TB is $$; but well worth it imo. I remember the older FAST TB having issues; but that was when they first came out. Check the set screw to see if it's backing out. I've seen that happen before and it can cause havoc with the IAC.

MMWS6

I'd like to see a pic of your MAF set up if at all possible. I am wondering if you may have the MAF too close to a bend. Just shooting in the dark here, but if the MAF is too close to a bend it can cause exactly what you have described here, even with the honeycomb in place. What is the distance from the honeycomb to the sensor? With the FAST I've read that about 2" from the MAF sensor is ideal

thunderstruck507

iTrader: (18)

The car runs and drives good, but not on a cold start. And what's more strange is even if you let it get warm it will idle poor if you try to drive it until the car is turned off for 15-20 seconds and restarted. The only exception being a slight hanging idle until the car comes to a stop for a couple seconds.

Cold starts are the big problem.

The air filter has a trumpet shaped bell reducer in it. On the maf I removed the stock screen and replaced it with the aftermarket one.

MMWS6

That bend after the MAF is pretty aggressive, but first things first. I was looking at your mods in your signature but you don't say what injectors you are running there. Stock injector or larger? Reason I ask is proper injector data is key to idle and cold starts. There are four tables in there that really need to be right. Just want to check a couple of things off the list.
Did you tune SD then MAF? How did you go about defaulting to MAF and MAP tuning?

thunderstruck507

iTrader: (18)

I found one of my old threads where I was struggling with the idle tune and Jesse from wait4me near the end of the thread gave me a really good step by step for idle tuning I need to look at again because I think I may have been in too big a rush and botched his good advice. Going back to that was my original plan but I wanted to make sure no one had some special tips for dealing with the 90mm tb/intake to add to the list. I recently read that the IAC bore is too small on the FAST intake and can lead to issues.



I agree, but due to tight space between the radiator and hoses and such it's hard to route the intake ducting anywhere else.


The injectors are the white GM injectors used for the supercharged 3800 cars. I used the injector Excel sheet available on the tuning forums to calculate and tune the IFR table. This was done based on their rated flow/rated flow rail pressure versus the LS1 rail pressure (I checked mine with a gauge as well to make sure it was in that ballpark).

I think that was the only injector specific table I altered but I did ask here if others needed to be changed and was not told otherwise (aside from obvious retuning of the VE and MAF tables).



I tuned the VE and MAF through the use of the CALC.VET function of EFI Live which has you set up a PID set and build a couple tables so that you hook up the wide band and go drive trying to vary load, speeds, and rpms to get enough hits in the cells to create a good average map of MAF and VE error. Then either paste or paste/multiply to the VE and MAF and do hand smoothing from there.

So it is my understanding that tuning this way prevents you from having to fault the MAF to tune the VE and from having to lower the "MAF only" rpm/throttle to tune the low end of the MAF. It seems to have worked well as the car drives excellent and has great LTFT (-5%-0% with no positives, no KR).


The biggest thing that concerns me about my idle tune is how high the Desired Airflow tables are. That table starts in the 30s cold and ends around 13. I was told in the other thread this might not be a big deal since the idle is higher than stock (850 in P/N, 900 in drive) and the TB, cam, and heads change things.

MMWS6

OK man, I'm working today but tonight when I get home I am going to shoot you a few pointers on setting up the injectors first, then see what the effect is on your idle. I say you start with good injector data, then tune from there. May go "back to formula" on your tune here, but it is a fairly quick process. If we go from square one, we'll find it I'm sure
EFI Live is a little different form the HP I'm used too, but I am not totally unfamilar with it either. I know where the tables are in it that we need to set up your injectors and the flow tables we need to address

MMWS6

Want to PM me a e-mail address bud? I'll shoot you the info on those injectors. I have the injector offset table, short pulse adder table, min fuel and short pulse limit for you. Ill shoot you the IFR table as well so you can compare to what you came up with

Exidous

iTrader: (11)

If its fine hot but not cold I'd give you RAF table a look. Once dialed in the idle VE cells may need another look.

thunderstruck507

iTrader: (18)

I definitely will be redoing that whole table for sure as I'm certain that's where a lot of the problems are, but it's also more complicated than just "hot versus cold".


I can start the car after it's sat all night and it's difficult to get it to run and idle on it's own until I keep it running about a minute. If it dies I have to crack the throttle with my foot while cranking to get it to start like it's flooded (or is it to get more fuel once the injectors kick on?). From there it can warm up for 30 minutes and still will surge and die if I touch the throttle or put it in gear.

But if I turn the car off for long enough to reset the pcm at any point (yesterday the coolant temp was still below 80*F when I did it) and restart it, it will idle fine and not respond negatively to throttle or gear changes.

For there it can cool down for many many hours and start back up and run ok (other than the high rolling idle/cruise control). The big problem just seems to be a dead cold "first start".

MMWS6

I am even more convinced it's a lot to do with the values you are running on those injectors. I e-mailed you the entire file I have on the Whites...

thunderstruck507

iTrader: (18)

Thank you, I will load those as soon as I get home at 5pm today and see if anything seems to change. If nothing else it should give me a cleaner start to begin the idle tune process over from some more stock like values.

thunderstruck507

iTrader: (18)

Made most of those changes. Nothing notable different in the warm start idle, so I adjusted the in gear DAF to be higher like the P/N table (not sure why I had them different...) and then started cutting back hard on the throttle cracker.

The car is MUCH better now. No cruise control, fires up and idles steady, and idle drops when I get off the throttle. Also doesn't idle up going from in gear to park. I will have to see about the cold start tomorrow.



One other question on something it does. When I start it, it idles high a moment then surges up to 2k rpm before slowly dropping to a normal idle. It does this every time it's started.

thunderstruck507

iTrader: (18)

Spoke too soon. Made another short trip today perfect.

Parked it for 2 minutes and got in to drive again and it's back to cruising itself around. I'm pulling my hair out here.

DrkPhx

iTrader: (15)

I have a feeling it's the drilled hole in the TB blade causing the problem. Try disabling the Throttle Cracker completely by maxing out the value and zeroing all of the airflow values. This should completely remove the cruise control effect and may even cause some idle dipping; but that can be fixed with the Throttle Follower and increasing base idle airflow. Each car is different; but this should help.

MMWS6

Drilled blades are the right way to go sometimes, but I can surely see where your blade could have been drilled too large to compensate for poor injector data too. Do you know to what extent it was drilled? Was your blade ever opened a couple of % and then reset to 0 in your tune? If so, try closing the throttle to 0% to see if the hole is now enough to run the car... might be worth a shot too man