Organized Drag Racing and AutocrossDrag racing and autocross discussions and questions. Techniques, tips, suggestions, and "what will I run?" questions.
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First time trial run. was uneventful. Ran roughly the same as it did last time out. 9.504@141.13 mph with a 1.363 60' time. For the second time trial I change the pill to make the fuel fatter and was rewarded with a 9.411@143.01 and a 1.348 60' time in worse air. The car I was beside thought I blew an engine there was so much smoke coming out from behind the car. Turns out I blew the rear intake seal bad. I tried to patch it up with grey silicone and sat out the third time trial run to let it set up. They had an oil down so it gave me even longer. Actually we had lots of oil downs today. Me twice, a pickup truck that blew a tranny on the start line and at least a couple of others.
Dialed in 9.42 for the first round and the smoke started coming out the back of the car by the 330 mark. At the 1000' cones, I lifted because I had my opponent beat. I won the round but knew I couldn't make another pass until the oil leak is fixed properly so I loaded the car up and went home. I still managed a 1.374 60' time and coasted across the finish for a win with 9.555@127.22 with a MOV of .1126. If I work into the night, I may have it fixed for tomorrow but it depends how I feel after supper. It's hot out and I'm really tired.
That personal best still only gives me a best corrected of 9.018@149.72
I've got some great videos but it's going to take time to edit and post them.
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87 IROC-Z
All engine, no power adders! Bests: 9.260@146.31 (at altitude)
Last edited by AlkyIROC; 07-20-2008 at 01:37 AM.
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Well there was no way I could pull the intake and save the gaskets so I guess I won't be racing on Sunday. One of the racers at the track said to use Vaseline on the gasket so it can be easily removed and reused. I guess that's what I'll have to start doing.
Got a couple of videos ready
Here's the nice burnout. The noise is from the car in the near lane. My mufflers are very quiet.
A different kind of in car shot of my second time trial run. I had the camera mount back more and up near the roof. I'll probably insert an overlay of the tach on this run later this week.
I need to go in to work today so it's a good thing I couldn't go racing. Oh the joys of being a manager. Have to go in to work whenever there's an issue. I've noticed that on just about every day I go racing or could go racing, the phone rings with a problem.
I'm still waiting for Streetfire to process my last video. It's taking forever for some reason.
Does your car alway go right when leaving? Or is it just seem that way? It does look like you're ready to correct it with the wheel, to me. It ought to go strait as a string, with out correcting. If it always leaves right, something isn't right. Do you leave it in low gear for the burn out? I never seen you change gears during the burnout.
That in camera shot did show me going to the right. Normally it launches very straight. The burnout is in high gear. I want wheel speed and it's easier on the clutch disks. I have enough torque that I don't have to start in first gear and 6000 rpm in high gear gives me enough wheel speed to heat up the tires.
OK. Here's a slow motion capture of the launch in the first round. Youtube's compression really sucks and Streetfire has spent a day converting it and it's still not available. Click the "watch in high quality" on Youtube if you get the option. A link to a high quality MPG file is available on request but this one should do for most people.
In the slo mo, it looks like it leaves pretty good. I wasn't picking at your car, just asking a question. Must be nice to have the power to start in high gear for the burn out. I've never tried it, nor will I.
Engine is all back together and I took it out of the garage to clean up the oil spills on the floor. I need to take it to a car wash that has good degreaser. The underside of my car isn't going to rust for 10 years with the amount of oil everywhere. Worst thing is, I also have Lucas oil stabilizer in the engine and that makes the oil stick to everything.
A waterbox burnout isn't hard in high gear. It's those dry pavement burnouts that street cars always want to do that's really hard on tires. Last year I was doing first gear burnouts and couldn't get enough wheel speed. Because my line lock switch is on the dash, I have to let it go to shift gears. This year I decided to just do high gear burnouts and it works much better. Less chance of hurting something in the transmission shifting in the waterbox. Doing a low gear burnout in a powerglide means the low gear band is applied. In high gear, the band is released. It's that simple.
To the average person, the slow motion launch looks good but to a racer, it's not really very good. The car goes right into a squat but it's hard to see. My 4-link setting had an anti-squat of 55%. The higher the percentage, the more force is pushing up on the car. I've readjusted the bars again and need track time to see what the change will do. The IC is back a couple of inches and up a couple of inches but I now have an anti-squat of 100.1" so it's just slightly higher than the neutral line. If the position doesn't work out, I have one more position I want to try before going back to the slow motion setting which has worked the best so far.
Tire pressure was at 8 psi. Watching the wrinkle, I can see that it's too low. The wrinkle should be more forward along the sidewall. I can see it right on the bottom.
One external video shop and I can see things that need to be changed. I need more shots like that now. I was trying to get into the right lane but lost the draw. That's why the camera shot was on the right side of the track but the launch shot still worked out.
Streetfire has finally processed the slow motion video. Only took 2 days. The youtube clip works well because it offers the clip in high quality also.
Someone replied asking what the frames per second was. Normal is 30 fps and that was slowed down to 7.5 fps (1/4 speed). I now took that 1/4 speed video and slowed it down another 1/4 speed which puts the fps at 1.875 fps plus took out a bunch of wasted time at the start of the video so it doesn't take forever until the cars launch. Amazing how much more you can see happening in super slow motion.
The raw file uploaded was an AVI file and it doesn't give the option to view in high quality. I guess I'll have to convert the AVI files to MPG to get that high quality option for future videos.
Even top fuel cars get some wheel spin. Those front wheels are in the air for less than a second. I figure they're carrying for about 20 feet (2 car lengths) and I 60' in 1.348 seconds. The video in normal speed isn't very impressive. Front end comes up, comes down and is over very quickly.
I've readjusted the 4-link to get more chassis lift. That should drive the tires harder into the pavement and reduce wheel spin however it may get tire shake. In the super slo-mo, it's easier to see the tire wrinkle is in the wrong location also suggesting more tire pressure is required.
Don't forget, I'm also launching at 6000 rpm so the driveline gets shocked instantly when the transbrake releases.
6000 rpm divided by 1.76 first gear divided by 4.86 diff gears = 701 rpm divided by 60 seconds = 11.7 rotations per second. From a dead stop, something has to give to get that wheel speed and some of it will be wheel spin. I never counted to see if the tire rotates 12-15 times before the 60' mark since I'm on the wrong side of the track but it would be interesting to know. I count about 5 revolutions by the time the front wheels come down.
hmm, lets see, I leave at 5k..not too much lower, with stock style suspension, a heavier car, by almost 200 lbs and probably similar horse power, on a 10.5 tire thats only 28 inch dia. and lo and behold it doesnt spin like that even at a track that is all asphalt, and it will 60 foot in the mid 1.2's , so why should a superior 4 link car not hook?
And yes top fuel cars do spin on launch, but how does a comparison with an unsprung chassis that uses 6500 hp or so (they have more) and no transmission (only a reverser) really relate to a doorslammer?
now, if you had said pro stock cars spin the tires some off the line, I would agree, but they usually spin less than one revolution before the car reacts, where yours spins alot more before anything happens, perhaps the guy in the other lane could help you, looked like his car left ok...
So, I really would like to know where you got this magic converter that doesnt slip when you let off the transbrake, seems like that would bog the engine a bit....even pro stock clutches have some slip in them when released and even when shifting.
Math and computer programs havent sorted this out since last year?
His looks like it hooks pretty good in regular speed. I'll bet everyone would be surprised if they could do what Stephen has done. Took the time to do and study their car leaving. He's going to learn alot with those videos. Wish I knew how to do it. I go agree that you need more tire pressure after seeing the video. Do you run a stiff sidewall tire? I started running a stiff wall tire last year and won't go back. The car doesn't move around near as much on the top end and it seems I get a better pattern on them. I've studdied the videos of my car leaving, but can't slow them down that much. I have to figure out how to do it now. Good job.
I have frame by frame videos of mine, cant get much slower than that. You should be able to use whatever video editing software you have(if you do have ) to slow it down, although some will not do it. I was using nero but the demo expired lol, so try looking around in the menus and stuff.
Do you run a stiff sidewall tire? I started running a stiff wall tire last year and won't go back. The car doesn't move around near as much on the top end and it seems I get a better pattern on them. I've studdied the videos of my car leaving, but can't slow them down that much. I have to figure out how to do it now. Good job.
Stiff sidewall tires. I've found at 7 psi, the car is a bit unstable at the top end of the track and so far 8 psi has provided the best 60' times.
I have a handful of different video editing programs. Some things are easier to do in different programs. To slow the video down, I use Sony Vegas Pro 8.0 but it can only slow it down to 1/4 speed. I then saved the file and reopened it to slow it down a 1/4 speed again so technically the original has been slowed down to 1/8 speed.
Trust me, I've been trying to find comparable video to watch and there's nothing on youtube or streetfire anywhere near like that in regular or slow motion speed. If there is, it's not easy to find. Always long shots from the stands or shots from behind the car where you can't see anything. I don't want to watch some 6-8 second car launch. I want to see a more normal 9-12 second car launch.
60' time in that shot was 1.369
I shift at 7400 rpm. I never did get around to inserting the tach display into that video.
That other car also dialed in a 9.68 so I was the faster car. He was slow off the tree with a .183 to my .042 so that's why he's moving first. He had a 1.374 60' time but only ran 9.786@143.15. By the 1000' mark I knew I had him beat. I slowed before the finish with a MOV of .1126 at 9.555@127.22. Based on the performance from the previous run, I would have run 9.51 on a 9.42 dial if I stayed in it.
One more thing I want to try is to launch from an idle. When the transbrake releases, have the throttle stop go to WOT at the same time. Right now the throttle stop goes to WOT 0.8 seconds before the transbrake releases. I just want to see what it does like that.
ok so it isnt close up, but it is a 1.35 60 foot, and 9.29 second pass...off a foot brake, with a heavier car and less engine and stock suspension, and a 10.5 tire (so it is a w). I dont see any excessive wheel spin, doesnt even rotate that much chassis wise.....maybe you should try foot brakeing?
I'd still think a lot of guys would have a lot to learn if they'd slow their videos down that much. You are hitting the tire pretty hard, but if you lighten it up it'll probably spin more. With a 1.36 60 fter and the weight you've got, it's doing pretty good. Guys that have a aluminum headed small block shooting the juice, don't know what you're up against. If they'd put a bb in then they'd know. Looks like I may be down a few weeks. My machinist don't know if he can save the block or not, and he has 3 others in front of me for the 383. Keep the videos comming, and good luck.
It's not that I have to lighten the car but get the chassis to transfer more weight to the wheels quicker and drive them into the pavement to increase traction. As for the speed or ET compared to others, I'm handicapped racing at altitude. I'm down roughly 100hp just because of the thinner air to burn. I'd be even slower racing in Denver but would probably be knocking on the door of an 8 second pass if at sea level.
OK, you've seen the slow motion or the super slow motion to see what happens when the car launches. Here's what it looks like in normal speed at 30 frames per second. Most people will say this looks like a good launch when seeing it at this speed. It's only when you slow it down that you can really see what's happening.
It looks very similar to other passes I have watched of it, mediocre. softer springs in the rear wont fix it either. I wasnt saying that you needed to lighten the car, I was making a comparison (we could all use 2000 lb cars lol, but they have their problems too). I usually run at 3500 to 4000 ft da too, and I bet the bugs dont add alot of power (one track has walls of gnats...).
It clearly looks good to guys that dont go as fast as you do, however there isnt a car in this world that cant be improved on any given day. Most people will not make those changes overnight. When talking about a car that has been heavily modified to make it more adjustable, and better (hopefully)than stock more problems arise, sometimes causing one to chase ones tail on whats wrong. Having a car that is nose heavy does not help things, but that can be worked with. It is merely a simple exercise in complex physics.
I forgot to ask this, have you found out why it is blowing the intake gasket end seals? I would definitely fix that before anything else, the last thing I want to hear about is oil on tires at 100+. Dont you have a pan-e-vac or some thing on there, it really should not build enough pressure to blow that out several times, is it possible it broke a ring or something when the head started leaking?
87 GTA 355/700r4
