Car Reaction Time Problems
Thread Starter
Drifting
Joined: Aug 2000
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From: Chapin SC
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Cruise-In III Veteran
Car Reaction Time Problems
I’m looking for some credible input in helping to fix my cars reaction time problem. Yes, I do mean the car. I have a quality practice tree and know that the problem is not me. In the recent Cartek Pro 10 the car averaged .237 on a 500 pro-tree over 7 runs. The quickest reaction time was a .166, the slowest a miserable .318. I’m an experienced racer guys, I know how to stage the car consistently. The car has an FJO data logging system that records 10-12 data points per second.
RPM data shows that on every launch (foot-braking) the engine will drop in rpm, sometimes as much as 125 rpm (from a base of 2400) at the application of wide-open-throttle (WOT). Upon the application of WOT it’s always between .15 - .2 before the engine starts to accelerate. I don’t think it’s an engine problem, the car did the exact same thing when it was a 382. The 427 is a completely new engine package. I suspect a converter problem - I’m running a Vigilante 3900 lock-up type.
For some of you guys that can’t seem to cut a good light on a pro tree, it may not be your fault. Any thoughts?
RPM data shows that on every launch (foot-braking) the engine will drop in rpm, sometimes as much as 125 rpm (from a base of 2400) at the application of wide-open-throttle (WOT). Upon the application of WOT it’s always between .15 - .2 before the engine starts to accelerate. I don’t think it’s an engine problem, the car did the exact same thing when it was a 382. The 427 is a completely new engine package. I suspect a converter problem - I’m running a Vigilante 3900 lock-up type.
For some of you guys that can’t seem to cut a good light on a pro tree, it may not be your fault. Any thoughts?
Le Mans Master
Joined: Feb 1999
Posts: 6,172
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From: somers, ny
Jerry, if it means anything to you, my car does the same thing. There's about .15 sec from the time i hit the throttle to when the engine starts to rev. However, there no drop like you're having. I can usually go .100-.120 on a 5oh protree. 237 sounds like something aint right, unless you've been drinking or something 
What is your R/T on a foot pedal with the roll out on the practice tree set to zero? What are your converter specs and what size front tire? What kinda slicks, size and rear gear?
You might need to think about using the transbrake to get out on a protree.
Edit: just read your post on the transbrake troubles......i can't help there
What is your R/T on a foot pedal with the roll out on the practice tree set to zero? What are your converter specs and what size front tire? What kinda slicks, size and rear gear?
You might need to think about using the transbrake to get out on a protree.
Edit: just read your post on the transbrake troubles......i can't help there
Last edited by ralph; Apr 15, 2007 at 09:17 PM.
Drifting
Joined: Jan 2005
Posts: 1,864
Likes: 6
Jerry,
You are an experienced racer which makes diagnosing your problems twice as hard. (you already know a lot)
I would have to type too much to get my thoughts and the details across.
PM me if you would like my opinion/assistance.
You are an experienced racer which makes diagnosing your problems twice as hard. (you already know a lot)
I would have to type too much to get my thoughts and the details across.
PM me if you would like my opinion/assistance.
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Race Director
Joined: Oct 2001
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From: Melbourne Florida
Cruise-In IV Veteran
I have the same problems with my car, always have...it has a terrible reaction time...it did with the stock converter, the TCI 2400 and now with the Vigilante 3200...two different folks have taken my car down the track and could not believe I could cut anything better than .150...lol...I am leaning toward a throttle body problem since I've had a BBK on mine since I got it...I have had the TB tweaked to within an inch of it's life but nothing more can be done...it is just a poor piece of equipment...
If I leave dead on time (third yellow) it is a gauranteed .135 light...I have to leave between the second and third to cut a light...no fun at all...
If I leave dead on time (third yellow) it is a gauranteed .135 light...I have to leave between the second and third to cut a light...no fun at all...
Thread Starter
Drifting
Joined: Aug 2000
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From: Chapin SC
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Fuzzy Dice,
I'll talk with Cartek about the throttle body, it's one of only a few parts we used from the old engine (a TPIS 90MM). Unfortunately working off a pro tree there is no way to compensate for a slow reacting car like you can on a full tree.
Ralph,
My R/T using foot pedals on the practice tree with the roll out set to zero averages in the .200 range with a less than a pefect pedal arrangement. I'm not sure on the converter specs other than a Vigilante 3900 that Cartek recommended. Front tires are the typical CCW drag pack skinny 16" I run 26X11.50-16LT ET Streets, the gears are 3:42. Running a healthy shot of nitrous with no overdrive I'm crossing the line around 6700 rpm so can't use more gear with the current tires.
I'll talk with Cartek about the throttle body, it's one of only a few parts we used from the old engine (a TPIS 90MM). Unfortunately working off a pro tree there is no way to compensate for a slow reacting car like you can on a full tree.
Ralph,
My R/T using foot pedals on the practice tree with the roll out set to zero averages in the .200 range with a less than a pefect pedal arrangement. I'm not sure on the converter specs other than a Vigilante 3900 that Cartek recommended. Front tires are the typical CCW drag pack skinny 16" I run 26X11.50-16LT ET Streets, the gears are 3:42. Running a healthy shot of nitrous with no overdrive I'm crossing the line around 6700 rpm so can't use more gear with the current tires.
Thread Starter
Drifting
Joined: Aug 2000
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From: Chapin SC
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Cruise-In III Veteran
Team Owner
Joined: Dec 2000
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From: SE NY
Cruise-In II Veteran
Once it's moving it accelerates fine.
Do you preload the suspension or launch off idle?
Thread Starter
Drifting
Joined: Aug 2000
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From: Chapin SC
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I'm not hearing a lag, the lag is confirmed with data logging. As per my original post, I'm foot braking but there's also a delay on a flash run.
Le Mans Master
Joined: Feb 1999
Posts: 6,172
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From: somers, ny
Fuzzy Dice,
I'll talk with Cartek about the throttle body, it's one of only a few parts we used from the old engine (a TPIS 90MM). Unfortunately working off a pro tree there is no way to compensate for a slow reacting car like you can on a full tree.
Ralph,
My R/T using foot pedals on the practice tree with the roll out set to zero averages in the .200 range with a less than a pefect pedal arrangement. I'm not sure on the converter specs other than a Vigilante 3900 that Cartek recommended. Front tires are the typical CCW drag pack skinny 16" I run 26X11.50-16LT ET Streets, the gears are 3:42. Running a healthy shot of nitrous with no overdrive I'm crossing the line around 6700 rpm so can't use more gear with the current tires.
I'll talk with Cartek about the throttle body, it's one of only a few parts we used from the old engine (a TPIS 90MM). Unfortunately working off a pro tree there is no way to compensate for a slow reacting car like you can on a full tree.
Ralph,
My R/T using foot pedals on the practice tree with the roll out set to zero averages in the .200 range with a less than a pefect pedal arrangement. I'm not sure on the converter specs other than a Vigilante 3900 that Cartek recommended. Front tires are the typical CCW drag pack skinny 16" I run 26X11.50-16LT ET Streets, the gears are 3:42. Running a healthy shot of nitrous with no overdrive I'm crossing the line around 6700 rpm so can't use more gear with the current tires.
Thread Starter
Drifting
Joined: Aug 2000
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From: Chapin SC
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Cruise-In III Veteran
Ralph, please reread the original post. Data logging shows a delay of up to .15 seconds in engine acceleration, often accompanied by a drop of 100 or more rpm upon application of WOT. This is not a traction issue.
Le Mans Master
Joined: Feb 1999
Posts: 6,172
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From: somers, ny
I was just throwing out alternative ideas. Based on your personal r/ts and the vehicle specs and an avg of 237 overall r/t.....something aint right. It sounds like your engine is bogging for some reason.
Thread Starter
Drifting
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From: Chapin SC
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Ralph, thanks for the input. I just spoke to Rodney at RPM Transmissions. He'll get the car in early May to modify the trans-brake for a quicker release time, install a 2 step and probably install a looser converter.
Team Owner
Joined: Dec 2000
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From: SE NY
Cruise-In II Veteran
Jerry, from what Ralph said it sounds like an engine issue.
Have you tried data logging with just the key on while you slowly press the accelerator and observing the TPS readings, looking for a flat spot?
Have you tried data logging with just the key on while you slowly press the accelerator and observing the TPS readings, looking for a flat spot?
Safety Car
Joined: Aug 2003
Posts: 4,988
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From: Hooterville, NJ
Boy, I do not like what I'm hearing in this thread. I'm about to convert the car to an Level 5 automatic and I don't like what I'm hearing about the reaction times going south. It sounds like the trans brake for the 4L60E is a waste of time.
Thread Starter
Drifting
Joined: Aug 2000
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From: Chapin SC
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Tom,
Don't give up on the trans-brake. There are bound to be problems with a new application and someone had to do the testing in the real world. Rodney (RPM Transmissions) is in touch with Carl Rossler, the designer of the brake. They're confident that they have a fix. My car will go back to RPM on May 1st for trans-brake mods plus we're going to install a newly designed 2 step that's adjustable in 100 rpm increments. Everything will be ready for the next Cartek Pro 10 (May 12th).
Don't give up on the trans-brake. There are bound to be problems with a new application and someone had to do the testing in the real world. Rodney (RPM Transmissions) is in touch with Carl Rossler, the designer of the brake. They're confident that they have a fix. My car will go back to RPM on May 1st for trans-brake mods plus we're going to install a newly designed 2 step that's adjustable in 100 rpm increments. Everything will be ready for the next Cartek Pro 10 (May 12th).