Throttle Cracker Airflow

[Dale]

I am working on my throttle cracker and I have noticed that most of these have massive quick drops at the lower rpms and speeds. I am thinking in my head that this should be more of a flowing drop correct? Why the sudden drop?

Was wondering if some of you could post screen shots of your modified B4309 charts for me to look at?

Thanks

[cmitchell17]

Yeah that stuff is really confusing.

Is there any tutorial or something about this? Like what all happends when you let off the gas and on the brake how does the PCM control idle airflow when your slowing down.

How can you reduce the follower and cracker settings to idle the motor down when it comes to a stop or the throttle is shut closed from being all the way open. Or after revving it make it come down to idel a lot quicker instead of hanging for 2 or 3 seconds?

[Goldfinger911]

Here is mine. My setup is in my sig. Throttle cracker is a complex thing to tune sometimes. You need to get not just the airflow right, but the Decay and Decay Delay as well. Not to mention, you need to make sure your Throttle Follower is tuned properly and not adding to any idling or decel problems. I had a stalling problem and it took me over a week to get it right.

[Dale]

Mitchll, thats what cracker does is adjust the IAC valve for when you quickly let off the throttle. Also for when coming up to a stoplight.

Goldfinger, thanks! Thats what I was thinking it should look like. I have a stall problem. Been on it for about 3 weeks now. "might" have figured it out last night. (btw, nice tummy in the sig!)

[Goldfinger911]

Yeah, I know about working on stall problems. I got my car running great. Except... I would back out of the garage, push in the clutch and wham. It would die. I could slow from a faster speed at a stop light and it wouldnt always die, but just simply backing up.. everytime. I finally got it ironed out. The problem wasn't just the Cracker. The Follower was also causing issues. If you want to see my tune let me know, I am always up for sharing. :)

Keep us posted how it goes.

[Dale]

Thanks for the offer, but I have a setup that only about 15ppl in the country have. None of them seem to be willing to share info.

I think I have tuned on my desired idle so much when the motor was still "cold" that once its warmed up and truly hot... It requires a different desired airflow. I have tuned myself out of the truely hot acceptable range. But I know once I get it back up to where it needs I will have the "cruise control" affect. So at the same time I am trying to work on that.

Maybe I'm trying to tackle to many problems at once for someone who is new to tuning.:doh:

[Dale]

Got my idle and stalling fixed. Now onto working on the "cruise control" and "jerkys".

Lesson for future searching. Tune your 80/92C idle airs AFTER the motor is well warmed up and has been driven for a few.

[The Alchemist]

Hey Goldfinger, Nice cracker map mate! The factory ones can be way off and usually cause idle hanging issues at intersections or auto pilot problems at lower engine speeds in 5th or 6th gear!
DALE: The idle airflow map DOES need to be right first before doing anything else as you have found out :)
Think of the throttle cracker as no more than " the amount of air that the IAC lets through when you take your foot off the loud pedal"
IE: it controls the amount of engine breaking you get when you throttle off. Too much and you get no engine breaking and idle hanging, not enough and you get thrown foward with engine breaking when you throttle off. Its as simple as that really.
Simply log TC airflow and follower airflow plus rpm, speed, map and go for a drive. Observe where the TC goes to on the TC map on decel and adjust according to your taste. I test on the road and aim for a steady decel from 70km/hr down to 5km/hr in 4th or 5th gear.
Hope this helps,

Mike

[Goldfinger911]

Thanks bro. I spent a long getting it set right. Both cracker and follower. I hate the stock tune where when you rev it, it seems to hang then come down slowly, but on the other hand I hate stalls. My car revs very quick (it will trip the shift light at 7000 rpm almost instantly) so I wanted it to "rev down" quick too. Sounds better that way with the cutouts open. :)

Also, I have zero surging while decelerating or driving at slow speeds. Makes it nice while driving through the neighborhood late at night.

If you want to see anything, let me know.

[Dale]

Thanks Alch,
I'm still tweaking the desired idle table. I'm setting it for a warm motor and screw the cold motor. So much difference I dont know if I can find a happy middle.

Also starting to flow my TC like gold has. I am finding that around 1000-1800 and 40-50mph I have a nice cruise control going on. So that will be my first spot of attack.

[cmitchell17]

I thought throttle cracker was right before or when the throttle is open just a little and it lets in air through the IAC?

I though throttle follower was for when the throttle closed and it let in air and slowly decayed through the IAC?

[5.7ute]

Throttle follower is related to throttle position. It is airflow added purely dependant on throttle position.
Throttle cracker is RPM/Speed dependant. It has no relationship at all with your actual throttle position.

[Dale]

mitchell. I thought that too at first. But they work exact opposite of how they sound. I found that doing some reading.


Follower is when pressing on the gas from a stop
Cracker is when you let off the gas and slowing down with "motor brakes"

[cmitchell17]

Thanks that will make a lot less confusing.

[TAQuickness]

Helps to tweak one table at a time too.

[jfpilla]

mitchell. I thought that too at first. But they work exact opposite of how they sound. I found that doing some reading.


Follower is when pressing on the gas from a stop
Cracker is when you let off the gas and slowing down with "motor brakes"

Dale,
The follower also controls the rate at which the TBlade closes. Too fast and you get overshot of idle and/or hunting and too slow you get cruise and/or hunting. All the airflow tables exhibit the same charateristics but enable us to control different functions, such as by temperature, TP%, RPM, speed...
The settings used for all the airflow tables depend on the cars setup and in particular, with automatics, the size and characteristics of the stall converter. An A4 can make you crazy. I find it very helpful to log RPMs and VSS and linking to the cracker table. You can see the bumps in the RPM graph and reduce the cracker at those speeds. I'm sure you will decide based on personal preference the amount of braking you like. Attached is my cracker table it works really well for my car. It's based off of a stock 2003 Corvette file with small changes down low. It and DAF are the only aiflow tables I changed. The rest are stock 2003 Corvette A4.
Joe

[Dale]

wow, thats not alot of gps in the chart. But then thats an LS motor and automatic.

My throttle blade isnt controlled via the pcm. Maybe it does on one with drive-by-wire? Or unless your refuring to the IAC opening when the blade snaps shut.

[jfpilla]

wow, thats not alot of gps in the chart. But then thats an LS motor and automatic.

My throttle blade isnt controlled via the pcm. Maybe it does on one with drive-by-wire? Or unless your refuring to the IAC opening when the blade snaps shut.

Aren't the GPS overall pretty much the same for a stock Camaro? The reason for the low numbers before coming to a stop is the 3600 stall. It confuses the PCM because it sometimes acts like a manual with the clutch in and sometimes offers resistance like an automatic.
It seems to work best when I let it almost come to idle as I slow down.
My comments are for Corvettes but it's my understanding that throttle follower affect is the same for F-bodies. Just substitute IAC for TBlade.

[Dale]

Im not running an LS motor though. I'm running a truck/TPI combo.

Have been working on the bodywork lately so no driving. Hopefully I can get to drive it this coming weekend.

[southern]

to revive this, how do you go about scanning and setting up the throttle cracker? Cause mine will slowly get faster till around 30 and I would love to get this worked out? So do you make a map and past the data or how exactly do you go about this?

[Dale]

I figured up where the car was getting stuck on "fast idle". Remembered the information, then just started modifying that area.

Mine will not be right because the car is a manual transmission but thinks its an auto. I got it as close as I could.