Need help with pro tree reaction time
#1
Senior Member
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Thread Starter
Join Date: Aug 2005
Location: Rifle Colorado
Posts: 585
Need help with pro tree reaction time
I've posted about this issue before, but still haven't found the answer. I have a 63 Vette SG roadster and can't go red on a pro tree. Every other Supergas car pulls the front out of the beams and mine just won't. What 4-link or other chassis adjustment will make a car wheelstand?
Car specs:
107"wheelbase
522 bbc 840hp
pg with 1.80 low
4.30 gear
33x16 D1 Goodyears
4-link/swingarm
strut front
23" front tires
Car runs strong & straight, 8.40's @ 160, 1.20 60's, but will barely lift the front off the ground. Great bracket car, but mid teen lights if I'm really on the tree, just aren't competitive in SG. Any suggestions?
Car specs:
107"wheelbase
522 bbc 840hp
pg with 1.80 low
4.30 gear
33x16 D1 Goodyears
4-link/swingarm
strut front
23" front tires
Car runs strong & straight, 8.40's @ 160, 1.20 60's, but will barely lift the front off the ground. Great bracket car, but mid teen lights if I'm really on the tree, just aren't competitive in SG. Any suggestions?
#2
Senior Member
DYNO OPERATOR
Thread Starter
Join Date: Aug 2005
Location: Rifle Colorado
Posts: 585
forgot this
total weight with me & full of fuel 2175lbs
1115 on the front and 1060 rear
single adj struts and double adj rear shocks
current IC is 51.5" long and 4.6 " high
total weight with me & full of fuel 2175lbs
1115 on the front and 1060 rear
single adj struts and double adj rear shocks
current IC is 51.5" long and 4.6 " high
#3
Lights
Are you using a delay box? If your lights are consistent, just pull a little time out of it. As for pulling the front end up, if the car is running straight and has 1.20 60 foot times, I'd leave it alone. Sounds like you're getting good weight transfer and hooking good. Wheels up launches are showy, but they are a waste of momentum. JMO
#4
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Join Date: Apr 2008
Posts: 504
Here are a few things that will help wheel stand.
Lighter rear springs
Higher instant center
Shorter instant center
Lighter rear shock rebound setting (extension)
Lighter rear shock bump setting
Increase staging RPM
Looser converter (higher rpm stall)
These are just a few variables that you have control of without making drastic changes to the drive train, like using a three speed trans and changing the rear gear ratio. You have a light car and what seems like a good basic scale report and 4 link set up. I will bet your crank is lower than 11.5" at ride height up front. If so, it is set up to have big torque like a pro stock engine may. Your engine is likely to tame in the torque department for that low of a CG and can not drive under it, there for no wheel stand. If you are not on the bars in the first 4' of the run then the crank height issue is one worth looking at.
If the car is dead hooked now, then tightening the rebound on the front struts, this will make the tires pick up out of the lights too. But only if you are dead hooked now. Otherwise you will cause spin.
Lighter rear springs
Higher instant center
Shorter instant center
Lighter rear shock rebound setting (extension)
Lighter rear shock bump setting
Increase staging RPM
Looser converter (higher rpm stall)
These are just a few variables that you have control of without making drastic changes to the drive train, like using a three speed trans and changing the rear gear ratio. You have a light car and what seems like a good basic scale report and 4 link set up. I will bet your crank is lower than 11.5" at ride height up front. If so, it is set up to have big torque like a pro stock engine may. Your engine is likely to tame in the torque department for that low of a CG and can not drive under it, there for no wheel stand. If you are not on the bars in the first 4' of the run then the crank height issue is one worth looking at.
If the car is dead hooked now, then tightening the rebound on the front struts, this will make the tires pick up out of the lights too. But only if you are dead hooked now. Otherwise you will cause spin.
#5
Re: Lights
[quote="fla1976"]Are you using a delay box? If your lights are consistent, just pull a little time out of it. As for pulling the front end up, if the car is running straight and has 1.20 60 foot times, I'd leave it alone. Sounds like you're getting good weight transfer and hooking good. Wheels up launches are showy, but they are a waste of momentum. JMO[/quote]
2X bigtime. SHOW doesn't GO !!
2X bigtime. SHOW doesn't GO !!
#6
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RACING JUNKIE
Join Date: Jun 2003
Location: Hobbs, NM
Posts: 842
Re: Lights
[quote="DrivingMissDD"]
Its a waste of momentum if your trying to go faster. Most cars running on a pro tree will run alot faster than the class index they're in. Whats hard is cutting a red light on a 4 tenths tree from a shallow stage. For that reason its more important to cut a quick reaction time than to run a tenth quicker et.
Originally Posted by fla1976
Are you using a delay box? If your lights are consistent, just pull a little time out of it. As for pulling the front end up, if the car is running straight and has 1.20 60 foot times, I'd leave it alone. Sounds like you're getting good weight transfer and hooking good. Wheels up launches are showy, but they are a waste of momentum. JMO[/quote]
2X bigtime. SHOW doesn't GO !!
2X bigtime. SHOW doesn't GO !!
#7
Senior Member
RACING JUNKIE
Join Date: Jun 2003
Location: Hobbs, NM
Posts: 842
Re: Need help with pro tree reaction time
Originally Posted by johnracer
I've posted about this issue before, but still haven't found the answer. I have a 63 Vette SG roadster and can't go red on a pro tree. Every other Supergas car pulls the front out of the beams and mine just won't. What 4-link or other chassis adjustment will make a car wheelstand?
Car specs:
107"wheelbase
522 bbc 840hp
pg with 1.80 low
4.30 gear
33x16 D1 Goodyears
4-link/swingarm
strut front
23" front tires
Car runs strong & straight, 8.40's @ 160, 1.20 60's, but will barely lift the front off the ground. Great bracket car, but mid teen lights if I'm really on the tree, just aren't competitive in SG. Any suggestions?
Car specs:
107"wheelbase
522 bbc 840hp
pg with 1.80 low
4.30 gear
33x16 D1 Goodyears
4-link/swingarm
strut front
23" front tires
Car runs strong & straight, 8.40's @ 160, 1.20 60's, but will barely lift the front off the ground. Great bracket car, but mid teen lights if I'm really on the tree, just aren't competitive in SG. Any suggestions?
#8
Senior Member
DYNO OPERATOR
Thread Starter
Join Date: Aug 2005
Location: Rifle Colorado
Posts: 585
Thanks for the responses. I definately not trying to put on a show though. Running in Supergas on a 4-tenths pro tree, I have no time in the delay box and can't get anywhere close to red. The car works great running flat out on a full tree where I can have delay in the box. If that's all I wanted to do, I'd leave it alone for sure.
Dparker, I've considered trying a stiffer tire, like maybe a D6. However, I have to run around 4.5-5psi to get it to hook consistently now and figure a D6 would make it worse. That brings me to what Topspeed said.
I run the struts at full soft when running flat out, and tightening them up makes it spin, so traction is obviously an issue.
You're right about the crank height. It's at about 11 1/4" at the current ride height. Do you thing raising the front ride height would help? That would also reduce front travel and may cause spin with the current 4-link setting. You definately got me thinking here......perhaps moving the IC back & up a little would plant the tire hard enough to allow me to run more tire pressure and a stiifer front strut setting without spinning. Might even be able to run a stiffer sidewall........what do you think?
I have 90lb rear springs and 250lb fronts. It had 200 fronts but I changed them to try to help reaction times. It may have made it worse.
Thanks again,
Johnny
Dparker, I've considered trying a stiffer tire, like maybe a D6. However, I have to run around 4.5-5psi to get it to hook consistently now and figure a D6 would make it worse. That brings me to what Topspeed said.
I run the struts at full soft when running flat out, and tightening them up makes it spin, so traction is obviously an issue.
You're right about the crank height. It's at about 11 1/4" at the current ride height. Do you thing raising the front ride height would help? That would also reduce front travel and may cause spin with the current 4-link setting. You definately got me thinking here......perhaps moving the IC back & up a little would plant the tire hard enough to allow me to run more tire pressure and a stiifer front strut setting without spinning. Might even be able to run a stiffer sidewall........what do you think?
I have 90lb rear springs and 250lb fronts. It had 200 fronts but I changed them to try to help reaction times. It may have made it worse.
Thanks again,
Johnny
#10
Senior Member
DYNO OPERATOR
Join Date: Apr 2008
Posts: 504
Getting closer to a good answer
Originally Posted by johnracer
Thanks for the responses. I definately not trying to put on a show though. Running in Supergas on a 4-tenths pro tree, I have no time in the delay box and can't get anywhere close to red. The car works great running flat out on a full tree where I can have delay in the box. If that's all I wanted to do, I'd leave it alone for sure.
Dparker, I've considered trying a stiffer tire, like maybe a D6. However, I have to run around 4.5-5psi to get it to hook consistently now and figure a D6 would make it worse. That brings me to what Topspeed said.
I run the struts at full soft when running flat out, and tightening them up makes it spin, so traction is obviously an issue.
You're right about the crank height. It's at about 11 1/4" at the current ride height. Do you thing raising the front ride height would help? That would also reduce front travel and may cause spin with the current 4-link setting. You definately got me thinking here......perhaps moving the IC back & up a little would plant the tire hard enough to allow me to run more tire pressure and a stiifer front strut setting without spinning. Might even be able to run a stiffer sidewall........what do you think?
I have 90lb rear springs and 250lb fronts. It had 200 fronts but I changed them to try to help reaction times. It may have made it worse.
Thanks again,
Johnny
Dparker, I've considered trying a stiffer tire, like maybe a D6. However, I have to run around 4.5-5psi to get it to hook consistently now and figure a D6 would make it worse. That brings me to what Topspeed said.
I run the struts at full soft when running flat out, and tightening them up makes it spin, so traction is obviously an issue.
You're right about the crank height. It's at about 11 1/4" at the current ride height. Do you thing raising the front ride height would help? That would also reduce front travel and may cause spin with the current 4-link setting. You definately got me thinking here......perhaps moving the IC back & up a little would plant the tire hard enough to allow me to run more tire pressure and a stiifer front strut setting without spinning. Might even be able to run a stiffer sidewall........what do you think?
I have 90lb rear springs and 250lb fronts. It had 200 fronts but I changed them to try to help reaction times. It may have made it worse.
Thanks again,
Johnny
One more thought, do you have and anti roll bar in the rear of this car. This will help directing the vehicle forward quicker as well. just a few more thoughts to ponder.