Couple questions here. I just reinstalled my air bag after a little haitus because I switched back to my old stock GM rear springs (the lower, softer springs were too bouncy for the street).
I intend (weather permitting) on hitting NED this wed. with my 26" ET streets on. Today I went to get the wheels aligned, but when I showed the guy my global west alignment specs he said he didn't know how to do it "non stock," and wanted me to come back tomorrow when the experienced wheel alignment guy was on. Anyway, to make one of my longer stories shorter, the airbag was back in, and for a double whammy I got caught in the rain on the way home (don't drive the car in the rain).
I figured this would be an easy way to test which way the car would slide (it almost always without perhaps one exception prefers to swing the rear to the passenger side, air bag in or not). I had just filled the airbag (22psi, just some random number, if deflated itself yesterday and I just pumped it back up again after reconnecting the lines. I had run 15psi in them at the track last year, but the one run at LVD I broke traction by getting on it too hard it still swung to the passenger side).
So I slowed down to about 15, maybe 10 not sure, and just got on it, and there was a very controlled (for the rain) slide to the right.
Here are my questions: Is testing in the rain invalidating what would happen on dry pavement?
Is testing on my 30psi street tires invalidating what will happen on the 16-18lbs (cold) I will run at NED in my 26*10.5 ET streets? (I am still finding the right tire PSI, its just hard to log enough runs to play with things and get home at a reasonable hour, I have just heard a heavier car needs a higher PSI so I have not ever tried like 14psi cold, and I also do not run tubes or rim screws).
Since my car sending its rear to the passenger side, I need to add more air to the bag? Say another 5psi and test again? Since I have to drive the car in the rain again tomorrow to get the wheel alignment, I can do another no drama, no attention getting test..
It should be interesting to try this new cam with my little mini DOT slicks. Despite the fact I didn't lose any low end torque below my converters stall speed, you can feel it driving around town (and its sort of annoying, its like an extra cylinder turns on at 2800rpm). I hope I can get a sub 2.0 out of it, but NED doesn't even allow real slicks on wed/fri racing and I have never gotten a sub 2.0 there, and I have less experience launching this car with this cam.. That and I am also leaving the sway bar connected this time, despite having better luck at LVD with them disconnected, I had the same bad luck at NED with them disconnected as well. I don't think I'm at the point where it matters yet.

Since I tow the car (my gas mileage is beyond terrible, its a perfectly driveable (and fun cruiser) car, but, I'd spend maybe $100 on gas going back and forth, vs. $25 towing it), I want to get as much as possible out of this trip. My dad is even coming to video tape (another chance to persuade him to run it!) so I should have some footage of my attempted launches.. NED likes to hustle cars through there but I am gonna take my time...

Matt

Since you have an automatic, this is a snap (as I understand it). You'll need 2 people, a tape measure and an air pump, of course.

Please do this carefully. smile.gif

With the car in drive, brake torque the car to just before your stall speed or just before the tires start slipping. Have person #2 measure the difference in height from the ground to your back bumper, on the drivers side and the pass side.

Start with both bags at minimum, which I think is 5psi. Increase the pressure in the drivers or passenger (Sorry, edited later-good luck!!) bag until the bumper becomes level while doing the brake torque step above.

Interesting,not knowing any procedure, I just 'smoked 'em', tweaked the air bag and smoked 'em again until it didn't move either left or right. I use only one. With hard street tires you could smoke 'em at 40+ mph and the thing would track straight as an arrow. Now after all the suspension pieces I replaced, it just sits there in the right (pass) spring with no air in it. The Hotckis solid uppers did something to equalize it, not requiring any psi in the bag. Believe it or not, when I removed it, it started slipping right again. So I leave the deflated bag in.
It seems to equate to slicks as well, but not with the line loc on. My car gets all twisted up with the front brakes locked.

I use only one, in the passenger side. I figure I'll have to use the "tweak and smoke" method since I don't have two bags if I read the first response right.
Plus for whatever reason without playing with my brake prop valve, I can only hold this thing with the brakes at like 1800 before it starts to push forward, when I could do 2500 with the old cams that had more low end.. I am not touching the prop valve since I did a 90-0 stop and turn into someones driveway that had peoples jaws dropped, so I figure its one of those "if it ain't broke don't fix it" things.
I'll up the psi by 5 and take it for a ride tomorrow. I'd love to be able to be more aggressive with the throttle knowing that if it does break into a spin, its not going whip sideways. That is fun, but not when you have the sole intention of going straight.. Then I can either drive around like that or drop the psi back down to 5 so my ride height doesn't look goofy. I got instructions for the cam swap guy to try not to drive the vehicle unless I drive it for 15-20 minutes after full water temp so I can help keep my oil cleaner, I have serious hydrocarbon contamination issues..

Matt

MadMarv If you have an air tank or pump. I think I would start with o air in left rear bag and 7lbs in the right. 5 to 7 lbs difference from side to side seams to work for me. Good luck with it;
Ron

I run zero on the left and 12-14 on the right.

I run 5 on the left and 12-14 on the right. graemlins/thumbsup.gif

If you guys are spinning straight with 12-14 PSI and I cut it sideways on the middle of the fattest road here (to minimize whatever effect the crown on the road may have) do you think something is wrong with my suspension or how I tested it? Do I need to try it from a stop (don't see why?) I was doing about 10 or 15 and just pushed on the gas (no flooring action, electric kickdown is disconnected anyway) until it broke loose. It cut sideways to the passenger side, not even the slightest indication it would run for the other side, with 22 psi. No one else here seems to indicate they would need anywhere near 25 or 27 psi to make it go straight. Are you still running stock GM rear springs or softer/shorter rear springs? I just put my GM stockers back in (new from detroit eaton spring like 9 or 10 years ago, few miles, so they are not "tired" stockers..)
I don't know if its just me but I find passenger side slides easier to manuever anyway.
It's hard to find an area to "test" these sort of things out in the burbs because any other car gives you a dirty look and I'm always wondering if they are on the cell phone with the cops, never mind houses or the odd pedestrian getting their mail who catches a glimpse.. Sometimes I end up circling my two "test" streets 3 or 4 times before I do it just so there is no one else around, its a true pain. Makes me wish I was in like Arizona or something..

sorry for the long winded posts, I just write this way, I even go back and cut out sentences...just trying to make the best use of my track runs. Someone should pounce on it and stick a strip in central mass.. There are a few closed capped non-ash landfills in industrial zones off highways where you might be able to get it to fly..

matt

I ran 0 Left and 8 right until with some more tuning The car started twisting again (video and spotters in the stands) so then I tried 14 pounds in the right, car went straight off the line and .03 quicker in 60 ft.

5lbs on the driver's side and 17 lbs on the passenger side. If you have adjustable uppers make SURE that the length of the control arms is equal unless you're intentionally trying to preload the rear.

I am running hotchkis adjustable uppers, global west lowers, 7/8 sway bar, koni red "adjustable" shocks that have never been adjusted (rides nice, need to remove shock to adjust).
The thing is the adjustable uppers I only bought to try to compensate for pinion angle when I installed my gear vendors. I don't recall what the angle is but its nowhere near desireable for drag racing, and its just enough to be ok for street use. I had to sell as "used" my jegster upper adjustables and buy hotchkis ones because the jegster ones wouldn't extend out far enough safely. I'll recheck their lengths again tomorrow when I jack the car up to see why my airbag is leaking slowly.
The gear vendors was a real hassle for me.. fit it in but then couldn't get the driveline lined up, so I brought the car over to a local drivetrain guy who ended up correcting the problem by "making space" by "releiving (spelled wrong..) the floor pan" (his words on the phone). That actually meant cutting a like 1'*8" hole in the floor and putting it back in with sheet metal screws.. if I was ever angry it was then (for less than 1/4" clearance..).
I will check the lengths of the upper arms again even looked square when I did my "safety checkup on stuff you never see " at the start of the spring.
Then I'll give the car a rip with 27psi and see, maybe I'm just an oddball here?

Thanks for the help everyone, I know I get windy and ramped up with posts right before a track run or engine part change..

Matt

Matt,

If you think the pinion angle is correct as it sits today, then measure the bushings center to center on each of the control arms and compare measurements to see if there is a noticeable difference between control arms. When I set the pinion angle on my car I did it with the passenger side bar disconnected. Once I had the pinion angle where I wanted it I backed off the rear part of the control arm counting the number of turns and then reconnected it (checked angle again). I then installed the passenger side bar the same number of turns. Worked for me. My car launches straight as an arrow. Good luck racing!

Matt, also, smoke 'em from a dead stop. That way it's safer, as you can tell right away, within seconds, which way the rear is sliding without swinging 4000lbs around the roadway.

Don't be upset at the driveline guy, sometimes a 1/4 is all it takes. My setup is not at the optimal angle because I whacked the floorbopards a few times with a 2 lbs sledge, and it didn't budge. Should have 'relieved' it and got a few more degrees out of it.

I got the 1/4" out of it, and I still have a "very odd" pinion angle (as described by the cam swap guy). Its safe to use and stuff, but like I said, not optimal for drag racing.
When someone told me they could repair the floor pan and make it look like it was never cut, I wasn't as steamed. I didn't actually get angry with the guy, I just was like "ahhh!!"
But there is definently something "up" with my rear suspension. I pumped the bag up to 35psi (max rec. psi) and stopped the car on the big flat road (too bad its short) near my house and bent into the throttle too hard to get it to spin, and poof, swings to the passenger side.
I'll have to look around again at all those things Ken said to look at when I am under there changing the tires. Maybe my pinion angle is just too odd for a straight launch? Or I think maybe more possible one of the upper arms is a different length than the other, which I'd rather have be the case, even if I don't have time to fix it before tomorrow.
Another bonus is that I have been told by two wheel alignment shops they won't work on my car because the rear sway bar is to low to drive onto their racks, and I can see I am thrashing the front tires on the inside because I am driving the car alot more this summer than I usually do. They said I need to find an open pit type wheel alignment place, which sounds like a challenge to find..

Matt

try pumping the right , passenger side air bag to 17 psi and take the left or drivers side air bag and put it at "Static pressure" to put it at static pressure simply (while car is sitting on ground with driver in it or comparable weight in place of driver on driver side) reach up and take the plug out of the stem of the air bag count to 10 and put the plug back in the stem. you have now solved the problem of your car wanting to kick out to the right. you may have to adjust the psi in the right side depending on the temp at the track usualy no more than 3 psi either way up or down.
hope this helps you out. graemlins/thumbsup.gif

Also it sounds like they have pre loaded your suspension too much you might want to back it down a bit, pre loading it to much might help a wheel hop situation but will deffinetly not help launch or ride aspects of you car.

I'm only running 1 bag, which seems to pop up as a problem in alot of posts.
I thought you only needed one bag for racing, on the street I just keep it down to safe for the bag PSI. I just wanted to iron it out to a PSI I could set it to for the track so if/when I break traction on my little DOT slicks, it will stay straight.

I guess when I change the tires tonight I'll take a look around under there for things that aren't adding up.

Matt

Matt, don't over think this man. Put 10 in your one bag. Do a massive burn out. See if the car still drifts right, if so add more psi to the bag. Your done when it sits there and smokes them in a straight line. This isn't rocket science or options adjusted spread generation, just simple stuff man. Go put 10 in and do some burnouts.

427L88 Hit the nail on the head. Add air till it goes fairly straight. If it does not go straight. You have another problem.
Ron

Hey guys little update if you can help out. I'm loading up the trailer now, so I won't be able to test it more tonight, but:
With 26psi in the air bag, and my ET Streets at 30psi (for driving around town on them), I did a from stop burnout, just enough throttle to spin them, to 5500rpm.
It left about 30' of strip and sent the car a little bit to the right, but not as much as before. What I DID notice is that the strip on the passenger side is much darker than the one on the right.
Does this say anything to you?
And can I overshoot my "go-straight" psi by starting too high? I thought it starts to slide the other direction when you get too much air in the bag though? or is that where I have been making my mistake?
As far as anything else goes, all the bushings look good and are tight, and the adjustable uppers are set to the same length. The pinion angle is screwy, but thats out of necessity.
I might just have to play around with it more. But the darker strip on the pass side means that tire is getting more power or spinning faster? Is that due to the airbag? You can't really notice these things since my BFG KD's leave really light strips unless you are doing a brakestand, but when I did a burnout with the ET streets on, it was night and day. I can take a picture tomorrow if they are still dark enough I suppose, or just make a new picture :D

matt