Ok. The printer at the place doesn't work, but the guy should be emailing me the files so I can take a closer look at them.
Some of you may recall and there is a link to the chassis dyno sheet at the bottom of my website, the car put out 426rwtq and 460rwhp with a stock 12" converter.
I got my new converter back (I sent it in for inspection ($150..)) after my tranny smoked itself from metal shavings clogging the filter; installed it and went to the track little disappointed but still druging on.
Since it has been raining every wednesday pretty much, I haven't been able to get back to the track on my little ET streets for a real baseline.
At the track though, I ran into the problem of needing 6800 to go through the traps (I pulled my rev limiter chip).
I have a theory that I might be able to get more mph out of my car by shifting it into overdrive (.78) at 6200 where I shift all the other times.
But I wanted to see how much hp/tq I made at 6800 to see if shifting was the right thing to do. I didn't have a 7000rpm chip so I all I brought the engine to was 6600 on a 6800 chip.
But this is what happened, and the dyno operator said he is sure he clicked the button before I mashed the gas on if not the first, definently the 2nd and 3rd pull.
This is what I did:
I put the car in 1st, ran it up to 2500rpm, shifted, ran it up to 2500 rpm, shifted, ran it up to 40mph ~2400rpm and then nailed the gas.
What happened is that the RPMs jumped in probably 1.5 seconds (maybe quicker-- it didn't even feel like a dyno run where I could watch the tach move until like 5000 rpm) to somewhere around 5000 (this is where my sheets would be handy, I will size them and post them to my website tonight) and then it would "grab" and bog the engine down a little bit then accelerate like a totally normal dyno run until 6500.
Now at first I thought the dyno guy wasn't hitting the button before or quick enough to get the dyno in action, because I wanted to start my RPM readings as low as possible.
I had disconnected my tranny kickdown switch, so that couldn't be affecting anything I am pretty sure.
Except the engine just like "free revved" until like 5000..

Was my procedure of starting at 2500 for runs 1 and 2 and 3000 for run 3 what did this?
Or is my torque converter significantly more screwy than I thought?

I know its been posted before, I but I am still unsure of how to I can test for sure the approximate stall rpm of my TC. Is there any way to do it that would not involve a traffic infraction if the police saw you doing it?
What I was figuring was really wacko torque numbers from 2400-3200/3400 (like way above 500) then as soon as the converter grabbed, the torque values would drop like a jumbo jet with its engines turned off.
The graphs are bizarre, I will post them as soon as I get them. The dyno operator assured me that (and this I think I still question) he had clicked the dyno on button or whatever before I mashed the gas.
I don't even care what the numbers were (alot lower than last time), but I do care about what I saw and want to know what it means, if anything.
I have reviewed my video of the dyno runs and it seems like the rpms jump from 2500 to 5000 (or around that, whatever the sheet says when I see them) almost instantly.

????
Matt

What tranny do you have? I can't think of an overdrive trans that will allow you to disconnect the kickdown cable. Every one I've had uses a throttle valve cable (no kickdown) and with it disconnected you would have no increase in pressure and it would kill itself rapidly.

Jody

TH400 with a gear vendors overdrive.. sorry for the confustion.

The GV unit is completelyl stand alone and is essentially bypassed when not in use, and it wasn't on the dyno. I've talked at some good length with a couple gear vendors tech guys on the phone before.

What I did was to just pull out those two clip-wires down near the gas pedal, I thought those were the kickdown connectors and that should take care of it, right?
The thing is I never saw an RPM whip-then-shift on my 5" tach, and thats the only thing I was looking at during the runs.
I will get the video shortened enough to put up on my website tonight.
You have to listen but you can hear it just sort of fly by those RPMs then do a dyno pull.
I know my old pulls at this chassis dyno were about 6 seconds, these don't seem like 6 seconds of pulling.

Matt

sounds as though the converter is "stalling" at 5000rpm. What size is it and whats the stall supposed to be?

9.5" and 3400 stall..

the dyno shop forgot to send me the emails, (friday afternoon, go figure) with the sheets. I will call them tomorrow and get them.
I have a 5.6mb file of two of the runs in .mp4, but my webhost is screwing up uploading them. When I get them up, I want you guys to listen, because if you listen carefully you can hear it skip those 2500ish rpm before it pulls. I'll keep trying..
I'll have more data when i get the sheets.

Matt

The dyno video is up, under "video new" New dyno runs, MP4.

Matt

Matt,

Based on your engine dyno runs and your previous chassis dyno runs, your peak power is at 5800 so your 6200 RPM shift point should be just about right. It looks like you also found a little bit of power between your engine dyno and chassis dyno runs. 461 RWHP is pretty darn good.

I think what you are seeing with your converter is simply a much higher flash stall than what you were anticipating. The best thing to do on the chassis dyno is to bring the RPMs up to the point you think the converter is flashing to prior to starting the pull. That will eliminate some of the converter multiplication. In my case it was 460 RWTQ vs 423 RWTQ (pump gas 383 SBC).

For a high stall converter what you are seeing is completely normal. I think your converter may stall a little high for your combo, but only by a few hundred RPM. If the top end efficiency is OK it should work well on the track.

If you get everything lined out you should be able to run some 11.30's @ 117 MPH or so.

Good Luck!

Thanks DragRacer..

I *think* I calculated the slip of the converter to be somewhere around 7-9%, I forget exactly what data I used to do this but that is the case.
The engine dyno runs were done in very controlled conditions with the exhaust and accessories already on the engine. My math says an 18% loss from the engine to the chassis when you use the data from the "stocker" converter.
My only question is why (and I haven't gotten the graphs yet.. when the place opens I will call and get them) the graphs don't look like a typical mega-stall converter on a chassis dyno.
There are no like super-inflated torque values below the stall rpm, and my hp was off like 30 hp from the prior run with the stocker converter (but this means nothing right? someone chime in here?)
Should I call the converter company back and talk to them?
I was on the phone with the guy, he had my engine dyno sheets in his hand and wanted to make my converter stall at like 4400, and I was like, no, 3400ish is fine, its a mostly street car.
Would I be of any benefit at all to drop to a lower stall rpm converter, say, an actual 4400 or the 3200-3400 I wanted? The cam swap shop suggested a stall of around 3200 for street use. I go to the strip for mph, because the car can't (as in I won't) be caged.
This must explain why I can do like +- 5mph (or a little bit more) at the same rpm below 5000 lol.
Again, when I get the graph I will get them on my site.
Do you guys suspect a possible cause of the much higher than anticipated stall speed (if that is the case here) is that the engine dyno numbers the converter company was working from were less inflated than they could be? A 23% driveline loss puts the motor at 600hp. 18% driveline loss is somewhat less than you would expect with a TH400, even with the "stocker" torque converter right? or wrong? So I am saying the converter guy whas looking at an engine that would make 600 or 605hp on a less strict dyno but saw it as a 565hp engine, and the 40hp in the difference there made the converter stall alot higher than I wanted it to?
From what I understand the more power behind the engine the higher the stall will be. I had this converter built for 2600rpm stall, then sent back last winter to be restalled for 3400 (both those cams were doing 112-113 mph) but I got another dyno sheet after swapping to a solid roller and going 117 at the track that shows the same hp numbers as the dyno sheets from the two 112/113mph cams?
**I called the chassis dyno place and they said they will email the files to me by noon. I'll post them after that..


thanks

Matt

Matt,

I would suspect your converter guy missed the boat because your engine has a very flat torque curve or in your case torque peak. You are essentially at peak TQ from 3500 RPM to about 5000 RPM.

If you mostly just drive on the street and only visit the track a couple of times a year pull your stall speed back to 3600 RPM. With your TQ curve you won't lose much (if any) performance on track and it will be much more driveable on the street.

I would bet your power loss on the chassis dyno is due to the current converter being much less efficient.

Whose converter are you using? I have been very pleased with my ATI converter. It acts very similar to a stock converter driving around but flashed to 4200 when the loud peddle was on the floor.

You may also talk to Steve Oldani, he may be able to help you out on the converter.

It's a precision industries 9.5" converter.

The thing is, when I sent it back to them for inspection after the tranny explosion, I don't think they changed anything. And that was for a "560hp" motor too..

I wouldn't mind bringing it back to 3600. This could also possible be why my engine feels like it "kicks in" at like 3000, and not from the power loss below that (2000-3000) because it was quite a bit less than I expected it to be.

I have the dyno run files now, I need to send them over to my PC (can't use them on my mac) and then I will size and post them.

Matt

On the chassis dyno the load on the converter isn't related at all to the weight of the car, only to the load of the dyno. Since the rollers weigh about 5400#, I would expect your stall speed on the dyno would be much higher than it is at the strip. I wouldn't spend a lot of energy trying to figure out the converter using the dyno as a load.

Then what is the best way to figure it out?
I'll give it a whirl if I can, although it looks like its going to rain. I had always thought a chassis dyno was ok to figure out stall rpm, but I guess maybe not.
I still would like to know why there is no data at all for where I stepped on the gas hard, even though the dyno operator says he pressed the button before I hit the gas on atleast runs number 2&3, and he thinks #1.
Runs 1&2 were done at about 2400-2500rpm gas mash, run 3 was done at 3000rpm gas mash..

jpg of dyno runs is up.

matt

Actually.. I was thinking about this.

If the rollers weigh 5400lbs, it doesn't mean I am moving or lifting 5400lbs. I am spinning it..
Which is different. So I am thinking here its not a direct correlation to 5400lbs, but has alot more to do with the whatever is required to spin the 5400lbs..? sorta like how they figure out how much hp you are making?
That was a little vague but my point is I am not directly moving 5400lbs..
its like pushing a 4000lb car.. I can push my car across the driveway..?
or totally wrong here?

matt

You're not lifting your car, either. You are rolling it on roller bearings down the street. Which car is harder to push across your driveway - the 4000# one or the 5400# one? Which is more resistant to motion?

Which engine will accelerate faster, the one with a 10# flywheel or one with a 50# flywheel? Are you lifting the flywheel or rotating it? Which one presents a greater load on the engine? Does the flywheel make a difference in the horsepower?

Stall speed is relative to the torque applied and the load sensed by the converter. If you put your converter in a 3000# car, it will not flash stall anywhere near what it will in your 4000# car.

Didn't think of it that way.
Ok. It looks like on the dyno graph the engine takes off at like 5200. The HP/TQ values are essentially worthless to me (and I knew that coming in) but I was really trying to shakedown the converter to figure out what its story was.
But that I guess isn't a way to do it.
How can I figure out where this thing is stalling?
There is a load-type chassis (not a mustang) but dynepack dyno within driving distance. Could I figure it out on that type of dyno? Is there a reliable way to do it on the street?

Thanks..
Matt

Matt, The torque converter will seem looser on the Dynojet than at the dragstrip. When we had the 482 engine in my sons car we dynoed it and the engine sounded like it just exploded when he floored it jumped from 3500 to 6000 immediately, the whole run only lasted about 4 seconds and stopped at 7200 RPM, the torque line went almost straight up to 6000 RPM, then the run progressed normally. (This engine has lots of tq.). We have a 8" ATI that is supposed to stall about 4200 but on the dyno was more like 6000 RPM. A transmission builder said that a torque converter will try to increase the stall as it's load increases. This motor has pushed a 4080 lb. truck 11.32 @ 116.9 MPH with the aerodynamics of a barn door and has 3.73 gears.

Harold, thats the exact same thing that happened to me on the dyno, I jammed the gas at 2500 and it "exploded" to 5200 and then did a pretty normal dyno pull until I killed it at 6500.
I guess I will have to figure out another way to deal with this converter..
By the way, your profile doesn't list an email address for you and I wanted to ask you about head porting, could you shoot an email to me?

I'm sorry Matt i had intended to give you that information the other day and just got busy and forgot. It's hsutton@gorilla.net.