That converter making issues for your car Colorado,it has a hurt sprag be my guess. It's 600-700 too tight but at least you got some progress 4.40's. That car would thunder with this converter. 9" Cortina core converter spragless.

when i look at the last graph posted i see a decent leave that just goes to shyt.in my opinion all due to chassis.leave at 5000,launch fair,chassis starts to porpoise unloads the tires,hits 8100,grabs and pulls down to a time shift at roughly 1.85.drop back on shift about 6400.convertor could be a little tight 6800 or more in cool air.but the real deal is te load and unload of chassis.lower air to 4.2,lowe launch to 4500.put on thinking cap to limit rear slip.tune up is not a real player hear at this time.and you are going to get quicker for sure

One thing I'm gonna do is turn off the launch limiter and see what it stalls at. The dips on the graph are me pedaling the car. Second run it spun hard. Still thinking it wants more fuel though.

quote:

Originally posted by Mike Rietow:
That converter making issues for your car Colorado,it has a hurt sprag be my guess. It's 600-700 too tight but at least you got some progress 4.40's. That car would thunder with this converter. 9" Cortina core converter spragless.

I think the sprag is ok. It's the track that went to ****, unless you are talking about it not pulling on the top end, then I can see where that might be the issue.

So you're shifting on time not rpm correct? The arrow is the shift?

The arrow is where the problem starts. Converter is too tight decelerates the engine and unloads the chassis.



This is what it should look like 6600 - 6800 stall

No, shifting on rpm. 7300. It shifted as soon as the tires broke loose. My converter was set up for gas/300 hit of nitrous on this engine at denver. It was flashing to 6200ish there. The first arrow you drew was long after it shifted. The second one is right before the shift. The first hump after your first arrow is the shift I think

quote:

Originally posted by Coloradoracer:
No, shifting on rpm. 7300. It shifted as soon as the tires broke loose. My converter was set up for gas/300 hit of nitrous on this engine at denver. It was flashing to 6200ish there. The first arrow you drew was long after it shifted. The second one is right before the shift. The first hump after your first arrow is the shift I think

The arrow is the shift 7300. Holy cow the track was bad then. Big improvement early in the run. Good deal.

you cant fix or learn anything on a track like that.i believe what you are saying but looking at the graph it is confusing

Get the engine happy with proper fuel/timing for the power your making at the altitude your at. Order a converter for what kind of power its making also at that altitude. Gear should be fine. I have a friend running mid 4.30s with a sr20 he has a 4.29 gear, 1.80 first and big bubbas.

IMO you have something wrong in the engine/tune-up. The engine RPM should almost instantly go to stall (which based on your shift drop is about 6700). And then sit there for .7 or so while converter "catches up" then go smoothly to shift. Here's a typical 7.50 1/4 mile dragster.

Red is engine RPM, Green is DS.

This message has been edited. Last edited by: Greg Kelley,

That's an excellent point. The arrow on the left the engine is making less power. I'd imagine (guess) it has timing out there but can timing kill that much power? Doubtful, even if we give the arrow on the left "6300ish" as Colorado has said, and the arrow on the right 6500-6600. That would be 75 to 100 hp difference. Can timing kill 75 to 100 hp or does the converter have an issue?I've never seen a sprag converter last very long. IMO you really gotta pay attention to how you do everything to make a sprag converter last a reasonable amount of time. The way this car is acting, is the worst environment for a sprag converter.

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

I'm not saying it's not an issue, but I'm running the same sprag in my converter that another racer from denver is running, and he's never hurt his in several seasons. He runs a blown alky deal, runs 6.0x's on in Denver without much effort.....easily a 5 second car there.. I'd tend to think as well if the sprag is gone or going that it wouldn't respond to tuning changes....

I do agree on the tuneup, I'm still working on it. Gotta order new nozzle jets and main pills. The car wants more fuel still. As I said before, the plugs are saying it's fat and wants more timing, but every time I add fuel or pull timing it goes faster......Here's a video of the first pass, the 7.07 run.....mph was way down, approx 15 mph from what it should have been, which tells me fuel...(This is also the run I didn't get a run graph from. The graph is from the second run)at least that's how I'm looking at it.

Once again, I do appreciate all the input. It's gonna take some more effort to sort this thing out, but at least you guys are giving me good direction to go and have me thinking about things I wouldn't have without you....thanks!!!

FYI, on this run, they sprayed the starting line before we ran. The second run that was basically crap they didn't....

Gonna keep working on it before any new parts, as I don't want to spend it twice....if I can swing it, and it proves I need a new converter, I'm thinking of going big and getting a bolt together. Need to see where things are at first though.

Here's the link, enjoy!:

This message has been edited. Last edited by: Alaskaracer,

Greg Kell*y is thinking of tune in terms of boost I'm guessing, only because converter stall is relative to boost the same as converter stall is relative to nitrous percentage (power) using a progressor.

We have a difference of 600-700 rpm of observed stall from the flash stall leave to the drop back at shift.

Did you turn 150 hp nitrous on down track before the shift? If not, I'd have the converter looked at if it were mine. I could see a difference of 200rpm of observed stall but not 700 rpm.

Looking at the graph, it's 6000 stall at the leave and 6600-6700 drop back observed stall at the shift. I can't think of anything in an N/A tune that could account for a difference of 700 rpms of observed stall. But I'm all ears.

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

The more I look at it the more it appears to be rear tire bouncing. Mine was doing that and it can be hard to resolve on a hardtail. Stiffer sidewall tires.

Holy tire wad batman. Had bounce and went to a
stiff sidewall here. Zoom in...

quote:

Originally posted by TD3550:
Holy tire wad batman. Had bounce and went to a
stiff sidewall here. Zoom in...

Tires were at 5 lbs on that run. Have been running 5.5 psi. Car was hopping much worse before. Do you think more pressure would help? All ears. I'm running 3195's.

In my experience after talking to certain GY engineer at one of the divisionals at RT66. I was running the GY 2533 of which is a high growth tire. His questions were what does the cup or crown look like during the burn out and at the hit?. Well i found out. My problem was running them @5.5 and ruining the sidewalls. Beside he stating I'm running the wrong tire.Cupping a tire will look like dark on the edges and light in the middle. Crowning a tire will be light on the edges dark in the middle. He stated most HT cars run a stiff sidewall.I did some testing with and without the rear bar. If you look at the edge of the tire after the run, bar VS no bar, you will see big difference.

The narrower on the edge the less scuff. The wider on the edge indicates more scuff which you don't want. Less contact.When you were done for the day, did you look closely at the tires and see any diagonal line cris crossing the tires?
That is another indicator of low pressure. Just putting out some ideas. I thought i knew a little about slicks after 35 plus years of racing>> Nope. when we were Kart racing, different ball game totally with tires.

That wasn't an older cable car at one time was it with the slips. Cable cars are where they use 2 cables L&R for load and preload with the chassis? Just curious.

Yes i tried 5000 and 5200, too darn violent for me. Went back to 4800.

This message has been edited. Last edited by: TD3550,

quote:

Originally posted by TD3550:
In my experience after talking to certain GY engineer at one of the divisionals at RT66. I was running the GY 2533 of which is a high growth tire. His questions were what does the cup or crown look like during the burn out and at the hit?. Well i found out. My problem was running them @5.5 and ruining the sidewalls. Beside he stating I'm running the wrong tire.Cupping a tire will look like dark on the edges and light in the middle. Crowning a tire will be light on the edges dark in the middle. He stated most HT cars run a stiff sidewall.I did some testing with and without the rear bar. If you look at the edge of the tire after the run, bar VS no bar, you will see big difference.

The narrower on the edge the less scuff. The wider on the edge indicates more scuff which you don't want. Less contact.When you were done for the day, did you look closely at the tires and see any diagonal line cris crossing the tires?
That is another indicator of low pressure. Just putting out some ideas. I thought i knew a little about slicks after 35 plus years of racing>> Nope. when we were Kart racing, different ball game totally with tires.

That wasn't an older cable car at one time was it with the slips. Cable cars are where they use 2 cables L&R for load and preload with the chassis? Just curious.

Yes i tried 5000 and 5200, too darn violent for me. Went back to 4800.

No, I didn't look at the tires, but I'll check them this weekend. Not running, been too lazy to unload until this weekend...gotta do a few things before I'm headed out again.

No tethers on the slip joints. This car has been ran with the slips functional since it was built.

I think I'm going to drop the launch rpm down some more, and give it more fuel. Not gonna mess with the timing right now. When I pull the car out of the trailer to put it in the shop I'll do a stall test to see where it goes to. I think knowing that will help too.

I've been thinking about everything you guys have been telling me and I've come to a few decisions, not sure if they are right or not. One, it still wants more fuel. So gonna give it more fuel.
Second, my launch rpms are still too high, going to lower them more.
Tire pressure is too low at 5. I'm actually going to try 6-6.5 to see what it does. I know you're directing me to go lower, but after watching the vid really close, it did wad the tire at the hit. It's been suggested a stiffer sidewall would help, but I'm not going to drop coin on a new set of slicks right now. I think the higher air pressure will sort of bandaid that. I have another racing buddy that runs the same tires but is at 6.7 psi...6.50-6.60 car in Denver....
I'm also going to get more temp in the engine. I get it to about 160 but it's generally about 140 when I run. I'll take the time to get more heat in it before the run.

It's getting there, and it's getting more fun to drive. I'm excited about getting it worked out..

Thanks everybody for all the input and help. If I'm going a different direction from what you may be suggesting, it's not that I'm disregarding what you tell me, I'm trying to verify that it's the right direction. I know where the middle is now, so it's about trying things on each side to see what it responds to the best and continuing that direction. I've got a lot to think about, and I need to get more data, but at least I know what to look at now.....


Thats why I like this board....you guys rock!!