8 second OEM 4 link drag race chassis setup
- Thread starter Alky V6
- Start date
Dusty Bradford
Well-Known Member
- Joined
- May 24, 2001
Not sure what you mean by comparing your car to a 5.20 car. I'm not saying you should run 5.20's but if there is a 10" tire car there running that fast and your having issues running 5.50's without tire spin...your suspension and or shock settings are off.
Asphalt tracks will not hook like concrete. They aren't terrible when the sun is down but when the heat is on and the track temp gets up, they get slick.
Now that I've found out what the adjustment ranges are with these shocks, I think I'm going to try stiffening them up more than I had planned for the next time out.
39 clicks on the rebound. As I was counting the clicks I was thinking to myself, "Dang! I hope I'm not disassembling the innards on this shock."
39 clicks on the rebound. As I was counting the clicks I was thinking to myself, "Dang! I hope I'm not disassembling the innards on this shock."
I'm going with 14 clicks on the comp and 20 clicks on the rebound. That will put me a tad bit over 50% on the comp valving and at 50% on the rebound valving. Ain't going to find out until you try it.
When I went to adjust the shocks, I found that the compression settings on the rears were at 0 clicks (full soft). This is how the shocks were set during the last testing session. I must have gotten side tracked the last time I was adjusting the shocks. I have never meant to ever have the compression settings at full soft.
When I went to adjust the shocks, I found that the compression settings on the rears were at 0 clicks (full soft). This is how the shocks were set during the last testing session. I must have gotten side tracked the last time I was adjusting the shocks. I have never meant to ever have the compression settings at full soft.
Dusty Bradford
Well-Known Member
- Joined
- May 24, 2001
That's pretty close to what I had in mind. If the track isn't that great I was thinking 10 comp and 24 rebound
Dusty. On a difficult track, I can understand the lighter setting with the comp, but what is your reasoning for going tighter on the rebound? I would have thought that one would want to go lighter on the rebound, too.
Dusty Bradford
Well-Known Member
- Joined
- May 24, 2001
No explanation other than that's my experience after 5 years of racing on a 10" tire. On a greasy track the comp has more effect on the hook than the rebound.
Keep in mind my shocks have sweeps, not clicks. On rebound I have maybe 7 sweeps so an adjustment of 1 sweep is a pretty large change. I have never ran them under 50%. If the track goes away taking the comp under 50% has better results for me while leaving the rebound 4 out of 7.
Keep in mind my shocks have sweeps, not clicks. On rebound I have maybe 7 sweeps so an adjustment of 1 sweep is a pretty large change. I have never ran them under 50%. If the track goes away taking the comp under 50% has better results for me while leaving the rebound 4 out of 7.
I was talking to a fella who knows some of the other fast, big tire racers at my home track about the thought that I was coming to the conclusion that the track was much more responsible for my traction issues than my chassis.
His responce was very interesting. He replied, "Well of course the track is the problem".
The other racers this fella has close contact with are big tire cars and he says that when these guys take their cars to another track, for instance Vegas, that they are typically 2 to 3 tenths of a second faster. He told me the driveshaft speed datalog traces are remarkably different between the tracks, which gives me some relief. I always wondered why my DS datalog trace was so rough appearing.
A drag sim that I use has shown me that on a well prepped track and well set up chassis, the car should be performing high 5.30s - 5.40s. If I'm truly losing 2 to 3 tenths due to the track, then the car is now performing at its peak potential, according to the sim.
More testing this weekend.
His responce was very interesting. He replied, "Well of course the track is the problem".
The other racers this fella has close contact with are big tire cars and he says that when these guys take their cars to another track, for instance Vegas, that they are typically 2 to 3 tenths of a second faster. He told me the driveshaft speed datalog traces are remarkably different between the tracks, which gives me some relief. I always wondered why my DS datalog trace was so rough appearing.
A drag sim that I use has shown me that on a well prepped track and well set up chassis, the car should be performing high 5.30s - 5.40s. If I'm truly losing 2 to 3 tenths due to the track, then the car is now performing at its peak potential, according to the sim.
More testing this weekend.
This last time out with the car, the rear shock settings were 16 comp, 10 rebound. The boost controller decided to give up the ghost so I wasn't able to give the suspension a fair testing. I had to switch to manual boost control in a hurry for a bracket event I had entered that day. Ended up with a max boost of 11 psi the whole day. Even so, the car managed a 6.66 1/8 mile ET. 
I moved the rear axle forward another 1/8".
The new IC and AS numbers are;
IC lenght; IC ht.; AS%
Left side: 41.2"; 10.6"; 128.8%
w/.4" rise: 50.3"; 11.4"; 112.8%
w/.4" rise and 5" front end extension: 51.4"; 13.9"; 119.1%
Right side: 43"; 11.9"; 138.2%
w/.4" drop: 36.9"; 10.9"; 149.0%
w/.4" drop and 5" front end extension: 37.5"; 12.7"; 151.3%
The .4" rise and drop simulating normal body roll on takeoff.
The new IC and AS numbers are;
IC lenght; IC ht.; AS%
Left side: 41.2"; 10.6"; 128.8%
w/.4" rise: 50.3"; 11.4"; 112.8%
w/.4" rise and 5" front end extension: 51.4"; 13.9"; 119.1%
Right side: 43"; 11.9"; 138.2%
w/.4" drop: 36.9"; 10.9"; 149.0%
w/.4" drop and 5" front end extension: 37.5"; 12.7"; 151.3%
The .4" rise and drop simulating normal body roll on takeoff.
Static clearance from the rear tire to the front lower edge of the fenderwell lip is now 1 1/4" with a 29.5 tire.
No touching was occurring at that area with the clearance set at 1 3/8" during the last testing where the 1/8 mile mph was limited due to the boost controller malfunction.
I'll be doing a complete suspension settings update in the next post.
No touching was occurring at that area with the clearance set at 1 3/8" during the last testing where the 1/8 mile mph was limited due to the boost controller malfunction.
I'll be doing a complete suspension settings update in the next post.
Summary of Changes to Date
The last summary of changes was post #211.
Total vehicle weight: 3290.5 lbs. with suited driver and full fuel cell load (15 gallons).
Percentage of weight on the rear axle: 45.75%
Percentage of weight on the left side: 51.57%
CG height = 21.7"
Present weight distribution, including 1/2 turn ARB preload;
LF 978.2, RF 806.6
LR 718.5, RR 786.7
Ride heights equal in the front, 1/8" higher at the RR than the LR, with driver, helmet and fuel.
I moved the rear axle forward another 1/8". Static clearance from the rear tire to the front lower edge of the fenderwell lip is 1.25" on both sides with a 29.5" tire.
The new IC and AS numbers are;
IC lenght; IC ht.; AS%
Left side: 41.2"; 10.6"; 128.8%
Right side: 43"; 11.9"; 138.2%
Lt w/.4" rise: 50.3"; 11.4"; 112.8%
Rt w/.4" drop: 36.9"; 10.9"; 149.0%
Lt w/.4" rise and 5" front end extension: 51.4"; 13.9"; 119.1%
Rt w/.4" drop and 5" front end extension: 37.5"; 12.7"; 151.3%
The .4" rise and drop simulating normal body roll on takeoff.
Pinion angle is set at 1.5 degrees upward angle from horizontal in anticipation of a 1-1.5 degree axle wrap up.
Front shocks (QA1 SA) are being worked from max stiff towards loose. Right now, the adjustment is at 14 clicks from full soft. Both front shocks using the same settings.
Rear shocks (Afco DA) set the same at 16 clicks comp, 10 rebound.
Both front and rear shocks adjust firmer by turning CW from full CCW position.
Range of the front shocks is 0-24 clicks.
Range of the rear shocks is 0-24 clicks comp, 0-39 rebound. Top knob for comp adjust, bottom for rebound.
Front extension travel limiters set at approximately 2" including bumper compression. On an even rise left to right, the RF leaves the ground (3/4") before the LF.
RB preload is 1/2 turn. Static weight on the RR is 786 lbs.
Rear tire pressure at 9.5 psi. Front at 35 psi. 9.5 psi in the rear has been confirmed to be the best pressure to use.
The last summary of changes was post #211.
Total vehicle weight: 3290.5 lbs. with suited driver and full fuel cell load (15 gallons).
Percentage of weight on the rear axle: 45.75%
Percentage of weight on the left side: 51.57%
CG height = 21.7"
Present weight distribution, including 1/2 turn ARB preload;
LF 978.2, RF 806.6
LR 718.5, RR 786.7
Ride heights equal in the front, 1/8" higher at the RR than the LR, with driver, helmet and fuel.
I moved the rear axle forward another 1/8". Static clearance from the rear tire to the front lower edge of the fenderwell lip is 1.25" on both sides with a 29.5" tire.
The new IC and AS numbers are;
IC lenght; IC ht.; AS%
Left side: 41.2"; 10.6"; 128.8%
Right side: 43"; 11.9"; 138.2%
Lt w/.4" rise: 50.3"; 11.4"; 112.8%
Rt w/.4" drop: 36.9"; 10.9"; 149.0%
Lt w/.4" rise and 5" front end extension: 51.4"; 13.9"; 119.1%
Rt w/.4" drop and 5" front end extension: 37.5"; 12.7"; 151.3%
The .4" rise and drop simulating normal body roll on takeoff.
Pinion angle is set at 1.5 degrees upward angle from horizontal in anticipation of a 1-1.5 degree axle wrap up.
Front shocks (QA1 SA) are being worked from max stiff towards loose. Right now, the adjustment is at 14 clicks from full soft. Both front shocks using the same settings.
Rear shocks (Afco DA) set the same at 16 clicks comp, 10 rebound.
Both front and rear shocks adjust firmer by turning CW from full CCW position.
Range of the front shocks is 0-24 clicks.
Range of the rear shocks is 0-24 clicks comp, 0-39 rebound. Top knob for comp adjust, bottom for rebound.
Front extension travel limiters set at approximately 2" including bumper compression. On an even rise left to right, the RF leaves the ground (3/4") before the LF.
RB preload is 1/2 turn. Static weight on the RR is 786 lbs.
Rear tire pressure at 9.5 psi. Front at 35 psi. 9.5 psi in the rear has been confirmed to be the best pressure to use.
More testing coming up tomorrow night.
This is an example of how much I have to pull back on the engine at the 1-2 shift with my home track. On this run, the 91mm and the boost controller were just put on and I didn't have any clue what the boost controller settings were going to do for me. Obviously, I had initially set the controller to give me too much boost. Pegged a 35 psi boost gauge. I have since never used this boost level again. That will have to wait for a better track.
The launch isn't much because this was before I started seriously working on the nitrous tune to spool this monster.
http://youtu.be/fzLAePWQmRA
It's a long video. Go to time frame 7:02.
This is an example of how much I have to pull back on the engine at the 1-2 shift with my home track. On this run, the 91mm and the boost controller were just put on and I didn't have any clue what the boost controller settings were going to do for me. Obviously, I had initially set the controller to give me too much boost. Pegged a 35 psi boost gauge. I have since never used this boost level again. That will have to wait for a better track.
The launch isn't much because this was before I started seriously working on the nitrous tune to spool this monster.
http://youtu.be/fzLAePWQmRA
It's a long video. Go to time frame 7:02.
The boost controller started working at the shop after the previous outing 2 weeks ago, so I took the chance and tried it for last nights testing. Well, the dang thing must have gotten stage fright or something. It wouldn't work last night. The controller is definitely being sent back for repair, now. I wasn't going to be content with 11 psi boost again, so I went manual boost control again, but this time I switched out the springs in the wastegate so I could throw some real boost at it.
It was a little tricky picking a boost level to use since without E boost control during staging and the launch it would be easy to overboost. Yep,... I actually said it would be easy to overboost during staging and the launch with a 224 cid and a 91mm turbo. :biggrin: I thought I would never say such a silly thing. Well, it's true. In fact, on one run that very thing happened. Luckily my emergency blow off valve that I had built into my intake manifold saved me again.
This is what happened on that pass. I had just switched over the wastegate springs and set the adjuster. It's been so long since I did a manual boost control that the adjuster was a big guess. I still had the nitrous system set to come back on at transbrake release for .4 second.
For future reference Donnie, DO NOT bother activating the nitrous at transbrake release with this setup!
Imagine having 250+ kPa MAP, PLUS a 360 shot of nitrous at the same time! Just a bit too much.
Interesting datalog coming up next. Blew the tires away at the launch. That has historically been very hard for me to do with this car, no matter what turbo was on the car. I would think that the rebound on the front and rear would need to be moved looser to get weight on the rear tires quicker with this sort of tuneup. Not to say that this is the sort of tuneup I want to stick with. Yipes!
It was a little tricky picking a boost level to use since without E boost control during staging and the launch it would be easy to overboost. Yep,... I actually said it would be easy to overboost during staging and the launch with a 224 cid and a 91mm turbo. :biggrin: I thought I would never say such a silly thing. Well, it's true. In fact, on one run that very thing happened. Luckily my emergency blow off valve that I had built into my intake manifold saved me again.
This is what happened on that pass. I had just switched over the wastegate springs and set the adjuster. It's been so long since I did a manual boost control that the adjuster was a big guess. I still had the nitrous system set to come back on at transbrake release for .4 second.
For future reference Donnie, DO NOT bother activating the nitrous at transbrake release with this setup!
Imagine having 250+ kPa MAP, PLUS a 360 shot of nitrous at the same time! Just a bit too much.
Interesting datalog coming up next. Blew the tires away at the launch. That has historically been very hard for me to do with this car, no matter what turbo was on the car. I would think that the rebound on the front and rear would need to be moved looser to get weight on the rear tires quicker with this sort of tuneup. Not to say that this is the sort of tuneup I want to stick with. Yipes!
This latest testing session has taught me a few things.
Do not allow the nitrous to be energized with a boost level above 240 kPa.
The best target rpm and boost level for the launch appears to be 5,800-6,000 rpm with 180-195 kPa MAP. Anything higher seems to overpower the tires and results in a slower 60 foot. Using the transbrake creep, we were able to get a 1.31 60' last night leaving the line using the above target rpm and map. The amount of front end rise and carry out felt good.
Loosen the front shocks 2 clicks for the next T&T.
During intial spoolup, the boost rises quicker under manual boost control. With manual boost control, keep the amount of nitrous on time after transbrake release to .100 second, or none at all.
Target 240 kPa through the initial part of the launch.
Do not allow the nitrous to be energized with a boost level above 240 kPa.
The best target rpm and boost level for the launch appears to be 5,800-6,000 rpm with 180-195 kPa MAP. Anything higher seems to overpower the tires and results in a slower 60 foot. Using the transbrake creep, we were able to get a 1.31 60' last night leaving the line using the above target rpm and map. The amount of front end rise and carry out felt good.
Loosen the front shocks 2 clicks for the next T&T.
During intial spoolup, the boost rises quicker under manual boost control. With manual boost control, keep the amount of nitrous on time after transbrake release to .100 second, or none at all.
Target 240 kPa through the initial part of the launch.
This is an interesting datalog. This was the best run of the night. I was still feeling out the manual boost control adjustment and on this run just happened to hit the MAP level where the aux fueling system is triggered to activate. You can see the aux fueling fluctuating on and off throughout most of the run. The interesting thing is how steady the rpm and boost is while the fueling is doing this.
The amount of nitrous on time after transbrake release on this pass was .200 second.
Notice how clean the driveshaft sensor trace is at the beginning of this pass.
The amount of nitrous on time after transbrake release on this pass was .200 second.
Notice how clean the driveshaft sensor trace is at the beginning of this pass.
