8 second OEM 4 link drag race chassis setup
- Thread starter Alky V6
- Start date
Welcome!
By registering with us, you'll be able to discuss, share and private message with other members of our community.
The RPM and MAP at the moment of launching in the second datalog was 6,217 and 210 kPa. Over 15 psi boost at the launch. It's impressive that I didn't have more tire spin than I did. On a cold night, and track, too.
Can't wait to get in there and do more testing.
Can't wait to get in there and do more testing.
On that first test of having the nitrous turn on again during the launch, imagine if I had picked to have the nitrous activate for one second during the launch instead of .6 sec. Where would the boost have spiked to? 40? 45 psi?
Sometimes you just have to sit back and count your lucky stars.
Sometimes you just have to sit back and count your lucky stars.
Changes to the car for the next time out.
3 clicks softer on the front shocks rebound setting.
I was incorrect on the rebound setting of the rear shocks. I thought they were at full soft. They were actually at 3 clicks from full soft this last time out. I'm going to keep them there for now.
Nitrous timer for the launch set to .400 sec. Down .100 sec. from the last testing.
BOV launch control setting lowered .6 psi. I'm hoping this will put me at 190-200 kPa MAP at the start of the launch. I'm working the power down at the hit of the launch. I think the tires are not up to it. A much deeper wave pattern on the slicks is showing after this last time out. A sure sign of the launch being on the violent side for the tires. The tires will also be rotated.
The other boost control settings will be left unchanged. Target max boost will still be 265 kPa MAP. I may lower it to 260 during the next testing.
Rear tire pressure is still at 9.5 psi. This is giving a good even pattern across the rear tires, except for about 1/2" of the edges.
The suspension preload and the roll bar settings seem to be perfect. The car is handling the best it ever has at both ends of the track.
3 clicks softer on the front shocks rebound setting.
I was incorrect on the rebound setting of the rear shocks. I thought they were at full soft. They were actually at 3 clicks from full soft this last time out. I'm going to keep them there for now.
Nitrous timer for the launch set to .400 sec. Down .100 sec. from the last testing.
BOV launch control setting lowered .6 psi. I'm hoping this will put me at 190-200 kPa MAP at the start of the launch. I'm working the power down at the hit of the launch. I think the tires are not up to it. A much deeper wave pattern on the slicks is showing after this last time out. A sure sign of the launch being on the violent side for the tires. The tires will also be rotated.
The other boost control settings will be left unchanged. Target max boost will still be 265 kPa MAP. I may lower it to 260 during the next testing.
Rear tire pressure is still at 9.5 psi. This is giving a good even pattern across the rear tires, except for about 1/2" of the edges.
The suspension preload and the roll bar settings seem to be perfect. The car is handling the best it ever has at both ends of the track.
You obviously know your car much better than I do but don't forget that if the rear tires are getting planted too hard, stiffen the rebound on the rear shocks to control the hit. This should keep the tires from being planted so hard then unloading when the suspension starts to settle and the power starts coming on. A lot of people tend to de-tune the power to get it to hook instead of change the suspension settings to accomodate the power so don't get caught up doing this unless you feel it's the right move.
Three clicks on the rebound can be really soft on rebound so don't be affraid to crank them stiffer as long as your only adjusting the rebound.
ks
Thanks, Kevin. I'm going to get some video of the launch this next time out before I do any adjusting of the rear shocks. I will keep your good advice in mind.You obviously know your car much better than I do but don't forget that if the rear tires are getting planted too hard, stiffen the rebound on the rear shocks to control the hit. This should keep the tires from being planted so hard then unloading when the suspension starts to settle and the power starts coming on. A lot of people tend to de-tune the power to get it to hook instead of change the suspension settings to accomodate the power so don't get caught up doing this unless you feel it's the right move.
Three clicks on the rebound can be really soft on rebound so don't be affraid to crank them stiffer as long as your only adjusting the rebound.
ks
I've moved the rear axle assembly 1/8" forward. This shortened the IC lengths a little bit. I had moved the rear axle back awhile ago to keep the tires from rubbing the front lip of the fender well. I think I went too far back and it's been rubbing at the upper back lip section of the fender well.
This put the IC length for the right side at 43.7", 136.5 AS%. For the left side 42", 126.5 AS%
Kevin, looking at the datalogs I recently posted, you can see the amount of tire spin relative to time at the launch. Does that give you any kind of clue as to what adjustment I might want to make to the rear shocks?You obviously know your car much better than I do but don't forget that if the rear tires are getting planted too hard, stiffen the rebound on the rear shocks to control the hit. This should keep the tires from being planted so hard then unloading when the suspension starts to settle and the power starts coming on. A lot of people tend to de-tune the power to get it to hook instead of change the suspension settings to accomodate the power so don't get caught up doing this unless you feel it's the right move.
Three clicks on the rebound can be really soft on rebound so don't be affraid to crank them stiffer as long as your only adjusting the rebound.
ks
I personally don't see the tires unloading causing an increase in tire speed after the initial plant. I'm new to reading driveshaft speed so maybe I'm missing something. Please advise. Thanks.
Not without mapping the graph with a video of the run so we can see what the front and rear suspension is actually doing at those points along the graph.
The only reason I mention the rebound setting is b/c I looked at the vid in your sig and noticed the rear tires getting planted pretty good and IMO, that looks way too violent for a car with that much power. I know it's not the same run as your last outing but I was thinking that if the rear suspension acts similarly then I wanted to let you know that shocks may be a good thing to adjust to eliminate that much hit and could help keep the tires loaded. With that much power the tires don't need much/any "hit" if it can be controlled.
Usually what I tell people is to stiffen the rebound up as much as possible to eliminate any "hit" then add some "hit" if needed to get them to bite. Sometimes the frontend needs to be adjusted to keep the tires loaded better by keeping th enose up or more/less travel , etc.
Remember, if the rear of the car goes up, at some point it has to come down. If the rear of the car is coming down then this is trying to unload the tires. This is why it's "best" to try and minimize the rearend from being planted if possible.
ks
I understand. I'll try tightening the rebound in the rear another 5 clicks. That will be a total of 8 clicks from full soft.
Does anyone know what the total adjustment range is for AFCO double adjustable shocks? I have not been able to find any material that explains how many clicks of range I have with the compression and rebound with these shocks. I tried to call them, and no call back.
That many clicks may be extreme considering how well you plan the tuning of the motor but you at least know what I'm saying so you can play with the settings as you feel.
Sorry, I don't know how many clicks and I did a real quick search with no answers either.
ks
Dusty Bradford
Well-Known Member
- Joined
- May 24, 2001
- Messages
- 5,802
A lot of people tend to de-tune the power to get it to hook instead of change the suspension settings to accomodate the power so don't get caught up doing this unless you feel it's the right move.
ks
Just because it needs repeating
If a similar car is running 1.25 60's and 5.20's on the same track and you struggle to go 1.30 and 5.60's......the issue is suspension. Not the power management.
My AFCO shocks have sweeps on the rebound rather than clicks. They are always set over 50% stiff. The compression is 50% or less depending on track conditions.
The rear shock settings are presently 16 comp, 8 rebound. I'm going to check, but I think 16 clicks is max.
I'm going to move the comp to 12 with the rebound at 8.
For the record, Afco's recommendations for a heavy door car performing better than 9.90s are 12-16 comp, 6-8 rebound. Very similar to Dusty's recommendation.
I'm going to move the comp to 12 with the rebound at 8.
For the record, Afco's recommendations for a heavy door car performing better than 9.90s are 12-16 comp, 6-8 rebound. Very similar to Dusty's recommendation.
Let's discuss the track that I frequent for my testing.
I get a lot of grief from a few that think I should have my car in the low 5s and blame my suspension in particular for not having the car performing to that level. Let me first inject my prediction of what the car will do when all is figured out. I think 5.50s is going to be it. These small heads will not take this project any further than that. That being said, the car has already gone 5.57 at high boost (30+) on the suspension before this latest attempt to really dial it in.
With the latest chassis setup, the car is going the fastest it ever has with the level of boost I'm now using. 5.80s using 24-25 psi boost late at night on a cold, dewey track on old tires that are questionable. I find that remarkable.
What's even more remarkable is that many may not be considering the condition of the track that I'm testing on. Dusty has mentioned engine power and chassis setup as important variables for getting the best out of this car, but I don't feel he's stressing the importance of the track condition enough. I feel the track is just as important a factor as the engine performance and the suspension setup.
After Dusty's last post, it made me think about my home track more. He mentioned that if others are doing 'this', then you should be able to do it too. The question popped into my head, "Is the track even capable of doing what these others are expecting out of my car?" This is a very important question.
I started to look back and try to recall who at the track is faster than me on a 10.5" tire. I can recall only one that was pushing over 1400 rwhp on a drag radial. Hmmm. I don't think I need to try to compare my car to his. BTW, he did end up losing control of his car and rolling it awhile back.
The few others that I can think of are turning big tires. And most others that I've watched come from out of town and attempt a 10.5 tire on our track were lucky enough to call it quits before they hit a wall. Some of the others did just that.
Bottom line, our track is not the best for a national record pass. It does have a fantastic launch pad, and they do prep the launch pad well, but after the transition, which is where I generally shift the car into 2nd, it does go downhill from there for high powered cars. I've heard this same report from individuals who are very experienced at reading tracks discussing the track condition with their driver. At the transition, be on your toes. This assessment has been proven over and over again whenever the track has a special event where very high horsepowered cars are running. Basically, the event turns into a pedal fest. Very rare to see a clean pass from those types of cars. Nostalgia class Funnys and Altereds.
Being one of the very few 10.5" tire cars at our track, I feel extremely proud of my performance, so far. All things considered, including the track.
I get a lot of grief from a few that think I should have my car in the low 5s and blame my suspension in particular for not having the car performing to that level. Let me first inject my prediction of what the car will do when all is figured out. I think 5.50s is going to be it. These small heads will not take this project any further than that. That being said, the car has already gone 5.57 at high boost (30+) on the suspension before this latest attempt to really dial it in.
With the latest chassis setup, the car is going the fastest it ever has with the level of boost I'm now using. 5.80s using 24-25 psi boost late at night on a cold, dewey track on old tires that are questionable. I find that remarkable.
What's even more remarkable is that many may not be considering the condition of the track that I'm testing on. Dusty has mentioned engine power and chassis setup as important variables for getting the best out of this car, but I don't feel he's stressing the importance of the track condition enough. I feel the track is just as important a factor as the engine performance and the suspension setup.
After Dusty's last post, it made me think about my home track more. He mentioned that if others are doing 'this', then you should be able to do it too. The question popped into my head, "Is the track even capable of doing what these others are expecting out of my car?" This is a very important question.
I started to look back and try to recall who at the track is faster than me on a 10.5" tire. I can recall only one that was pushing over 1400 rwhp on a drag radial. Hmmm. I don't think I need to try to compare my car to his. BTW, he did end up losing control of his car and rolling it awhile back.
The few others that I can think of are turning big tires. And most others that I've watched come from out of town and attempt a 10.5 tire on our track were lucky enough to call it quits before they hit a wall. Some of the others did just that.
Bottom line, our track is not the best for a national record pass. It does have a fantastic launch pad, and they do prep the launch pad well, but after the transition, which is where I generally shift the car into 2nd, it does go downhill from there for high powered cars. I've heard this same report from individuals who are very experienced at reading tracks discussing the track condition with their driver. At the transition, be on your toes. This assessment has been proven over and over again whenever the track has a special event where very high horsepowered cars are running. Basically, the event turns into a pedal fest. Very rare to see a clean pass from those types of cars. Nostalgia class Funnys and Altereds.
Being one of the very few 10.5" tire cars at our track, I feel extremely proud of my performance, so far. All things considered, including the track.
You are 100% correct. All of my suggestions are based off of a well prepped tracked through the finish line.
A buddy of mine was running 8.6's with his 4200lb truck and our local track would prep the track to the 1000' mark which is exactly where he would spin the tires.
We eventually started talking to the crew of the track and told them our delima and asked if they could spray the entire 1/4. They were MORE THAN HAPPY to do this for us in our favorite lane and that solved our problems. They even made special trips with the sprayer just for us when we pulled to the line. The reason they did this was b/c we were by far the fastest vehicle on that track so they wanted good runs for us too. Doing this even made them more confortable about talking to us and asking if they could do anything else to help us out. Fast cars are great advertising for tacks that only have slower cars.
Ask the same thing from your track guys even if to suggest a few test runs to help you diagnose a traction problem.
KS
A buddy of mine was running 8.6's with his 4200lb truck and our local track would prep the track to the 1000' mark which is exactly where he would spin the tires.
We eventually started talking to the crew of the track and told them our delima and asked if they could spray the entire 1/4. They were MORE THAN HAPPY to do this for us in our favorite lane and that solved our problems. They even made special trips with the sprayer just for us when we pulled to the line. The reason they did this was b/c we were by far the fastest vehicle on that track so they wanted good runs for us too. Doing this even made them more confortable about talking to us and asking if they could do anything else to help us out. Fast cars are great advertising for tacks that only have slower cars.
Ask the same thing from your track guys even if to suggest a few test runs to help you diagnose a traction problem.
KS
They do spray the entire track at certain events. Particularly when the Nostalgias show up. If there is a difference for my car, it's very slight. It's more of a problem with the basic track surface, from what I understand, listening to others who know more than me about track surfaces.
If you go back and study the datalogs I posted, you will notice that I drop the boost level down quite a bit at the point where I shift into 2nd gear. This is as the car is passing the transition point. I then have to ramp the boost in for the remainder of the run. I know many may want to blame my suspension for my having to do this, and some of it may still be my suspension. But, I am aware that much of it is the track.
An interesting thing I've noticed when I've taken the car to other tracks. 1/4 mile tracks. I would of course be using the same tuneup that I setup the car with for my home track. There have been a few times now where at the point of shifting into 2nd, I was put back into my seat more than usual. I think I was just sensing the track holding the shift better than what I was used to with my home track. Unfortunately, I never had enough test and tune time when visiting these tracks to experiment with putting more boost into 2nd gear and beyond. The first track that I experienced this with was a Pinks event at Bakerfield. On this one paricular run, I was not pre-spooling the turbo before the launch. I was still in early stages of tuning in the 91mm. Anyway, when the turbo spooled up at a point before I hit 3rd gear, I was very surprised at how the car held the track and pulled so much harder than I had ever felt before. I'm sure it had to do with the differences in the tracks.
An interesting thing I've noticed when I've taken the car to other tracks. 1/4 mile tracks. I would of course be using the same tuneup that I setup the car with for my home track. There have been a few times now where at the point of shifting into 2nd, I was put back into my seat more than usual. I think I was just sensing the track holding the shift better than what I was used to with my home track. Unfortunately, I never had enough test and tune time when visiting these tracks to experiment with putting more boost into 2nd gear and beyond. The first track that I experienced this with was a Pinks event at Bakerfield. On this one paricular run, I was not pre-spooling the turbo before the launch. I was still in early stages of tuning in the 91mm. Anyway, when the turbo spooled up at a point before I hit 3rd gear, I was very surprised at how the car held the track and pulled so much harder than I had ever felt before. I'm sure it had to do with the differences in the tracks.
Dusty Bradford
Well-Known Member
- Joined
- May 24, 2001
- Messages
- 5,802
This is why I asked about the track condition you race on several months ago. At your power level you should not be experiencing the issues you are at the gear change unless you have serious suspension issues or the track has a bump or something at the same point. Considering the car was 60' low 1.3 or high 1.2, that's why I asked about the condition down track.
I use others performance at the track I race at as a gauge of what the track can handle. Low 5 second mustangs are a dime a dozen here so if I'm sorting out a chassis, I use those cars as a clue as to what the car should be capable of. If I put enough power in a car to run 5.50 and it spins yet there are other cars running 5.20.....the issue is with the suspension. There is no magic power management to make a car go down a greasy track...it's always the suspension IF there are other similar cars there that are faster.
Once you cross the 5.70 range the track condition is a major player. There are at least 3 tracks within an hr of me that I can't test on. It's just a waste of time. 5.50 cars are OK but there's no way to run 5.0's on them so I have to travel farther to get good data.
You also may look at the transition to see if it's better or worse in certain spots of the groove. One track we have to race on has a bad dip at the transition. It's much better towards the right side of the groove. After launch I have to drive the car to the right side of the groove to cross the dip where it's more manageable. I only found this after walking the track. I had never succesfully made it down the track with a 5.0 tune-up in the car until I saw what the issue was.
I use others performance at the track I race at as a gauge of what the track can handle. Low 5 second mustangs are a dime a dozen here so if I'm sorting out a chassis, I use those cars as a clue as to what the car should be capable of. If I put enough power in a car to run 5.50 and it spins yet there are other cars running 5.20.....the issue is with the suspension. There is no magic power management to make a car go down a greasy track...it's always the suspension IF there are other similar cars there that are faster.
Once you cross the 5.70 range the track condition is a major player. There are at least 3 tracks within an hr of me that I can't test on. It's just a waste of time. 5.50 cars are OK but there's no way to run 5.0's on them so I have to travel farther to get good data.
You also may look at the transition to see if it's better or worse in certain spots of the groove. One track we have to race on has a bad dip at the transition. It's much better towards the right side of the groove. After launch I have to drive the car to the right side of the groove to cross the dip where it's more manageable. I only found this after walking the track. I had never succesfully made it down the track with a 5.0 tune-up in the car until I saw what the issue was.
I was sure you had to understand the track factor. Now that you understand a little more about my track issue, maybe you can stop trying to compare my car to a 1.25 60 footer that clocks 5.20s.
There are no conceivable bumps that I am aware of. I've walked the track a few times, and as far as bumps, it's very good. The actual suface is what I'm not crazy about. I'm not a track surface expert, but is just seems too coarse grained to me. I don't know of how else to put it. The concrete launch pad is great, but it transitions to a coarse grained asphalt surface that can't retain enough rubber to create a smooth surface.
