quote:

Originally posted by Kenneth:
You're car is sticking the tire too hard which leads to an unhappy chassis and pulling gear out or pulling timing will only make it worse. Assuming this is a hard-tail, a wheelie bar would really help along with less tire pressure. Sometimes more is less, sometimes less is more.

I agree with ya it's over working the chassis/tire at the hit. The chassis looks like a fishing pole with a fish on, which is good relatively speaking. Most likely what we're looking at here is a sprag torque converter built for racing in Denver, with an active stator which is multiplying torque on the high side of the 1.8 to 2.4 scale below stall in conjunction with the addition of methanol on the car which is making more torque than taken into account when the current converter was designed for the car. Taking everything in here into account he's probably already run through a gambit of different tire pressures in the few laps he has on the car in Florida. I'd change low gear 1.64 - 1.69 and make the converter spragless. A spragless will multiply torque less initially below stall but flash stall higher for wheel speed as you're speaking. Then when Colorado makes a tire pressure adjustment, the car will respond to it one way or the other positively or negatively. The way it's hooking, spinning and hooking at the hit now is the last thing you wanna do to an active stator, it'll hurt it the same as driving into the tire hooking on the burnout with a sprag converter. I definitely wouldn't do a 3.90 gear going 4.50's with a big tire though. Probably be a 1.69 low.

This message has been edited. Last edited by: Mike Rietow,

I'm sure you have tried lowering the two step and adding to the tire pressure? I can't recall what tire...Pressure?
I would be reluctant to reduce your leverage with less gear. I suspect your converter setup it a big player here too.

Colorado, this car has a Ripper Powerglide and a Transmission Specialties spragless converter. Out of the box, off the trailer new engine it went 4.62 in middle 80 degree Florida air. It has conventional BBC Brodix 355 cylinder heads, 565 tall deck engine 4.30 gear. It'll run in the 50's on a lil bubba tire. This guy likes to haul ass and doesn't follow the crowd so to speak approach wise. I've been talking to him about a 4.56 and a 1.69 low.

i think we all see some of the same things here,i just think there is a chassis setup issue,it can be resolved for sure.

Ok, more details on the car. Wasn't able to get any download from the grid, but that's another issue. Car is a 257" hardtail, double slip joint. One joint is right behind the cage, the other is up behind the nose. 30# weight bar in the nose, total weight with my fat ass in the seat is around 1965ish... Tires are new 3195's, run them at 5.5 psi. I can't tell you what the converter flashes to, so hopefully tomorrow I'll get that info. My launch rpm was set at 5400, and final timing was at 29, although that slowed the car. I backed it up to 28 which is where it was when it made it's best pass, the 4.51. I am going to try 27* and see what happens.

Here's the plan for tomorrow:

First hit: 28* timing, lowered launch rpm to 5000. Trying to decide if I want to run 6lbs in the tires or not...

Second hit: 27* timing, to see what it does, same launch rpm.

Third hit: Timing change depending on what it did previous run, either more retard or back to 28*, lower leave rpm depending on what it does...

After that, it all depends on time and how long it takes to get those runs done...

Thoughts and input? Higher tire pressure? Weight out of the nose? Less tire pressure?(not sure that's the way to go, I'm thinking higher would be better)

After tomorrow I'm hoping to have better data on tune and the car itself, so I'll know what steps to take next. It does want more fuel, but I'm out of pills to richen it more for now. Gonna get new larger nozzle jets (as per James), but those will get ordered after this weekend. I do know the fuel is close though, but not 100% right.....

Keep the suggestions coming....I'm taking notes.....

quote:

Originally posted by Kenneth:
You're car is sticking the tire too hard which leads to an unhappy chassis and pulling gear out or pulling timing will only make it worse. Assuming this is a hard-tail, a wheelie bar would really help along with less tire pressure. Sometimes more is less, sometimes less is more.

I do have a wheelie bar for it, but it's not adjustable enough to put the wheel on the ground until the front is up about a foot or so...I'll run it on the bottle, but don't think it will do me much good right now other than add weight...

I'm at 5.5 psi on the tires, but that's just what I ran with the last set, which were 3186 mickeys. These are definitely different, but I don't think lower air pressure is the way to go....I could be wrong though....


Biggest issue is testing time....I'll be able to get in about 3-4 runs before the day is done, so chasing tire pressure is something I'll do more of when I can get it to stop hitting them so hard for now, as that is my biggest issue.

Sending private message hope it helps.

a quick thought the slip behind the seat is the issue that i saw right off.limit it or block it off,the tires combined with all the slips is another issue.way too much bite not enough power.the weight in the nose should be ok and will help keep tires planted down track.drop the air to 4.2 and leave launch in area where you are.again the rear slip is a big factor .after you get it to settle down you could start inching back up on air,but may find even lower would be better

quote:

Originally posted by rusty:
a quick thought the slip behind the seat is the issue that i saw right off.limit it or block it off,the tires combined with all the slips is another issue.way too much bite not enough power.the weight in the nose should be ok and will help keep tires planted down track.drop the air to 4.2 and leave launch in area where you are.again the rear slip is a big factor .after you get it to settle down you could start inching back up on air,but may find even lower would be better

Agreed for a while I struggled with too much nose weight and too much tire pressure in my hardtail.

I'll try lowering the tire pressure, but can't do much about the joint behind the cage. No way to lock it out. It only moves about an inch though....I guess I could drill it out and put a bolt through it....

quote:

I'll try lowering the tire pressure, but can't do much about the joint behind the cage. No way to lock it out. It only moves about an inch though....I guess I could drill it out and put a bolt through it...

is there a way to use clamps or tethers,when it launches there is an obvious lift in that area.

i dont suggest a bolt, it would need to be built for it initialy

quote:

Originally posted by rusty:
is there a way to use clamps or tethers,when it launches there is an obvious lift in that area.

No, I don't have any tethers to try and tubing isn't split to use clamps. I can pull the weight bar out of the nose, that will help some there, but I don't know how it will affect weight transfer to the rear. The first time I had it out on alky, it blew the tires off at the hit, but that was mostly the track and not so much my car. It did want to hike the nose a bit then though, but it seemed to unload the chassis pretty quick. I didn't have the weight bar in it then....

I appreciate all the input, it gives me things to think about and try....I know I'll get it figured out, just need to find what it likes....

i know you will get it figured out.dont be afraid to try all things,but remember sometimes a change that may be what you need could cause you to need another change some where else. tethers can be built the sam as collector tethers.check with chassis mfg about a way to restrict that slip.it also may be good for him to see that vid.good luck

Too much bite (traction) you lower the tire pressure.

The driveshaft graph of the lap I looked at the video of, would be flat at TB release, then a huge spike to flat again.

Take some tire pressure off until the driveshaft graph produces a rounded hump starting at TB release to flat to the shift. I wouldn't touch the ignition timing. I might raise or lower the leave chip. It's high now, try lowering it to 4600- 4800

Tight track you lower pressure, loose track you raise tire pressure.

This message has been edited. Last edited by: Mike Rietow,

quote:

Originally posted by rusty:
a quick thought the slip behind the seat is the issue that i saw right off.limit it or block it off,the tires combined with all the slips is another issue.way too much bite not enough power.the weight in the nose should be ok and will help keep tires planted down track.drop the air to 4.2 and leave launch in area where you are.again the rear slip is a big factor .after you get it to settle down you could start inching back up on air,but may find even lower would be better

This is a good one IMO. Set the timing where it has made the most power. Lower the leave rpm, maybe it'll tone the chassis arch a little to get some speed in the tire at TB release. Keep the tire round with speed at tb release. Good luck I'll bet with posts like the one I quoted here, you'll get some good runs/progress tomorrow.

We'll see what's gonna happen soon, headed to the track in about an hour or so

Passes in the 4.40's be my prediction. If you post an image of the driveshaft graph rusty will get you rolling down through there nice and smooth, quicker. Be my prediction.

Good luck. I would try lower tire pressure also.

Well, we got in two hits. First hit here was my setup:

Put timing back at 28
Tire pressure at 5 psi
launch rpm down to 5000

Track got sprayed right in front of me so good bite off the line.

reaction time we won't talk about...
1.046 - 60'
330 - 2.888
1/8 - 4.467
1/8 mph - 154.83
1000 - 5.857
1/4 - 7.070
1/4 mph - 179.11

Car launched fine, little bit of a hop at the hit, and basically fell flat on it's face around 900' or so....just stopped accelerating...No graph, was having issues with the grid again. Peak rpm on delay box showed 7800.

Second run, decided to pull one degree of timing to see what would happen. Not the best run. Basically blew the tires off at the hit, spun, pedaled, then hooked. seemed to run better up top, still didn't feel as strong as it should, but didn't nose over like before.

actually got a decent reaction, pro tree, .026
60' - 1.267
330 - 3.331
1/8 - 4.962
1/8 mph - 151.46
1000 - 6.374
1/4 - 7.587
1/4 mph - 184.42

mph was better, but et was killed by spinning at the hit. I DID get data this run though, (thanks markemark!!), and I'll post the graph in a few min....just need to get the pic uploaded of it. I think I need a new converter.....

Other thing is car is acting like it wants less timing and more fuel. Plugs show it wants less fuel and more timing. Buddy here thinks the converter is too loose, not loading the engine like it needs to be, and would explain why it doesn't want timing but wants fuel. He thinks once I get a load on it, it's still gonna want fuel but may want more timing too.

So I'm still going to get the larger nozzle jets and smaller main pills from James to richen it more. I also need to look at a new converter.

Once I post the graph from the crappy run, let me know your thoughts, we're making progress! First hit was much better and second sucked due to spinning....As soon as I can get the video posted I will as well. Only have video from first run, not second. Technical difficulties with the camera....

Thanks for all the help though guys, it's getting closer!!