Well the day has finally come that I got to take the car to the track.

Best time of 10.83 ET @ 127.5 MPH shifting at 6000 RPM with a 1.59 60 foot

With my setup I want to shift it at 5500 RPM and not 6000 RPM

It ran 11.1 ET @125 MPH shifting at 5500RPM

The shift light was also coming on in third gear approx 3/4 track, now when I shifted to car at 6000 RPM it

ran a better time and the shift light was coming on at 6000 RPM at the end of the track.

This tells me that the torque converter is slipping to much .

Here is my data logs of what happened during launch and all the way down the track

1st gear

2700 RPM 4" Vacum , Launching on foot brake
3000 RPM 2 psi
3000 RPM 4 psi
4300 RPM 7 psi
4800 RPM 9 psi
4900 RPM 9 psi
5300 RPM 10 psi
5500 RPM 11 psi
5800 RPM 11 psi
6100 RPM 12 psi

2nd gear

5200 rpm 11 psi
5400 11 psi
5500 11 psi
5800 11.5 psi
5900 12 psi
6200 13 psi

3rd gear

5300 12 psi
5500 13 psi
5800 13 psi
6000 13.5 psi


As you can see in first gear it hits 4 psi at 3000 rpm and then slips right up to 4300 at 7 psi and does not hit full boost

until 5300 RPM.

It is a precsion industries 9.5" stallion non lock up convertor with a special turbo stator, I have contacted them and told them all

this and they want me to ship it back to them and they will do a free restall on it.

According to precision it should achieve full boost by 3200 Rpm and then flash up to approx 3800 RPM and hold the engines power

from that point, rather than slipping up to 5300 RPM.

They want to tighten it up one step which would be 400-500 rpm tighter. He says that two steps would tighten it up

800 - 1000 RPM which would be to much on my setup.


It makes sense to tighten in up 500 RPM because that would make it so that I could shift at 5500 RPM and also cross the line

at 5500 RPM.

Here is my real concern, its obvious from my data logs that the converter slips right up to 5300 before full boost is acheived.

according to precision it should slip up to no more than 3800 rpm while under full boost.

So by these numbers im slipping appox 1500 RPM higher than I should be.

So how will tighting the converter up 500 RPM over all fix the 1500 rpm slippage that I have on my launch?????

Just looking for some opinions from all you guys, does all of this sound correct????

By the way the transmission is NOT slipping.

Thanks guys

Also once I get the convertor tightened how much gain should I see in MPH as well as how much drop in ET ????


All my car Info should be in the signiture down below

 

I don't think you have a problem with your converter. Looks like about a 2800-3000 stall (this is where you hit zero vac) and the rpm drops between shifts seem about right. Too loose of a converter would show hardly any rpm drop between shifts. If you want to lower the shift points and not rpm the motor as much, I'd look into a lower gear in the rear. If you are looking to build boost faster along the rpm range, I'd play with the tune/boost control/exhaust housing AR. BTW, how can the converter manufacturer tell you at what point you will see "full boost"? There are alot of variables in that equation.

Rob

 

Looking at your logs, it seems as if you've got a 900rpm drop on the shifts. Tightening it up one step would put it at a pretty optimal 1400rpm drop on the shifts. What they're talking about at 3800 is the hydraulic lock up point.....the point that the pump and turbine are spinning as close to the same speed as possible. The motor is still going to accelerate to 5500 or whatever. You can't think of the ultimate stall speed, how much it slips, and the lock up point as one thing. You can vary your slip percentage one amount and change the lock up point by another using different methods in the converter. For example, you can change the distance the turbine is from the pump and you can also change the fin angle. Together that might change the slip % by 5% which might lower stall speed by 500rpm, but it might lower the lockup point by 700rpm.

 

Sorry guys, that was the data log with the shifting at 6000 rpm

when I shifted at 5500 rpm it dropped 800 rpm from 1st to 2nd gear,

then from 2nd to 3rd it only dropped 300 - 400 RPM, and almost immediatly the shift light came on in 3rd gear.

It seemed to work the best when shifted at 6000 rpm and not the 5500 rpm it is intended for.

I have talked to other people who have run a similar setup with the twin t-3s and they go from 0 boost to full boost within 300 rpm

So I could safely assume if I start building boost at 2900 rpm , I should be fully spooled by 32-3300 RPM.

If the convertor had the lock up point set to 3800 RPM I should see full boost before or at the lockup point, correct???

The 3.27 gears are in the car rather than a 3.55 gear, because of the intention to only spin it to 5500 RPM

The reason for this is because of the stock short block that is already living on the edge and would live a bit longer with

reduced RPM's

When leaving the line and smashing on it , at what point should I see full Boost if it is going to slip on the converter???


With the turbo car it would be nice to see the lockup point at 3600 to 3800 rpm and not 5300 rpm., but at the same time

only drop the overall stall speed at the top end by 500 rpm , so that the shift light comes on at 5500 rpm at the

end of the track.

Im assuming the guys at precsision industries would know exactly what to do going by the data logs to make it slip

to the proper RPM and then grab.

I just want to make sure that its done right so that I dont have to take it out the 3rd time

Would anyone agree that one step tighter on the converter would be just right, and that two steps would be a little to far????

 

I've got news for you......... you might have to pull the converter 5 times to get it correct. It's trial and error. Knowing what I do about converters and turbo combos, it would be naive to think you can hit it dead on in the first two trys. I'm not trying to burst your bubble. Just trying to be realistic.

 

i have had my converter out 6 times now.

 

Exactly. I've swapped converters three times in one day. LOL

 

What convertor company are you guys using???

The guy at precision told me I only had one option, and that is to go one step tighter,

He claims 2 steps tighter would be way to much.

Thats a far cry off of 5 times.

Im no expert on converters, but one would think its a little ridiculous to take 5 shots at is to get it right, unless

other changes were made with the particular combination.

 

I use PTC now. I've used Precision, TCT, Transking, Neil Chance, and now PTC. Precision deals mainly with GM LS1 and Buick Turbo6 guys who are perfectly happy with simple. I say get it tightened one step and see how you like it. But remember what I said. You don't necessarily have to settle for one step or two steps being the end all. You may find that you want it that tight up top, but need it to flash a little higher to get the engine in it's power band quicker. That can be done. It might take trial and error though. Will Precision do something like that? Probably not. They seem to have certain combos that they stay with. For example, they say that one step is 400rpm. Well.......... ptc doesn't work like that. I tell em, I want it to flash 200rpm higher but stay locked up where it is. And they do it by varying fin angle, stators, pumps, clearances, etc. Precision just wants to be able to change the pump because it's very simple and quick. That may be fine for you. But you can't find little things like that out without trial and error. You make it sound like we're a bunch of quacks for having a converter in and out so many times. Hell, you should see the stack of $1000 converters I have for the race car. Do I need 3 spare? No, but I have them so we can play with different combinations of converters to see how they change the way the car reacts. If we were talking about nitrous cars, you could expect to hit it pretty much dead on the first or 2nd try. But we're talking about turbo cars here. And they're entirely different animals.

 

i use PTC. the first two converters(pulled 3 times) he thought would be enough for my little v6. well i had more then they could handle.

soo i steped up to a 9'' race converter. and now have gotten a bigger turbo. well at the same psi as before the 9'' race converter has be maxed out. and its not tight enough. oh and i have pulled it 3 times.

well now i just got in my brand new 9.5'' converter. time to see what that one will take. lol. i have gotten 80more CFM on the intake side of my heads and i am turning up the boost 5-8 more PSI.

 

shane you saying that it would be optimum if your converter dropped 1400 rpms during shifts? Or is it different for every car?

 

Different combos are different. On a low rpm app, I'd say 13-1400 would be good. It'll put you back into the meat of the powerband. On a system that can turn a lot of rpm, you don't necessarily need the rpm drop. That's because a converter will become more efficient the more rpm you can turn.

 

Actually, that's typically the normal scenario for a turbo car, as well as many other drag-race oriented applications. A friend of mine finally just got his converter right for his turbo application, and that was after NINE removals. It's just the nature of the beast. Just about the only way you're ever going to get the converter spot-on the first time for a turbo car is by pure luck.

 

I was only going on my 4th converter change to get it right in my old car. Bet I was still behind the curve lol.

 

I've pulled mine already 3 times and the 4th new convertor is on it's way

 

OK OK I get the point

Anyways, I took another run down the track again and actually got it to shift at 5500 through out all the gears, It was

tough being the converter wanted to flash right up to 5000 rpm, Shifting at 5500 rpm from 1-2 dropped the rpms down

to 5000 and shifting from 2-3 at 5500 rpm it only dropped to 5200 rpm with the shift light set at 5500 rpm turning on shortly

after half track.

So im only showing an RPM drop of 300 -500 rpm between shifts which is a far cry from the optimal 1300- 1400 rpm.

Going by this the guy at precision said I should stall it 2 steps down which is 800 - 1000 rpm.

The car is now stalling(hydraulicly locking) at 4700 -4900 RPM. Full boost is not being built until this point either, due to the lack

of load against the engine , required to spool up the turbos.

I spoke to another fellow who had almost the exact same setup and his turbos started spooling at 2700 rpm and were fully

spooled at 3000 rpm, now his converter stalled to 3200 rpm, which explains why he could build the boost so fast.

I guess what I need is for the converter to stall (lock up) right when full boost comes in, or slightly before.

Now here is what im wondering, If I drop the overall stall speed 1000 rpm, that should be seen as a 1000 rpm drop in stall in third

gear which has the most load on the engine.

Now if the transmission is in first gear the load is reduced as compared to 3rd gear so it should have more than 1000 rpm drop

in stall which will hopefully drop it from about the 4700 rpm that it is at to around the 3200 rpm that I need leaving the line.


Just wondering if all this sounds correct, and wondering what you all think out there. Am I doing the right thing here????

Also wondering on the horsepower, the car ran 127.5 MPH in the quarter through a non lock up converter.

This should equate to 131 - 132 MPH with a stick car which in a 3200 - 3400 lb car with me in it equates to

around 600 FW horsepower.

Thanks Again guys

 

No one else knows anything about torque converters????

Or do we just have a post here on how many times it takes to restall them???

 

You want the converter to flash to the point you go from zero boost to positive boost. From that point, let the motor stall against the converter where it wants to based on the amount of boost you run.

 

That's about how mine is setup, but mine could be a bit looser I think. Mine flashes to about 3000 on the transbrake, then starts to boost and will max out at 6 psi and 4400 rpm with no boost control hooked up.

Shane, how much slip are you seeing with a properly set up converter at the 1/8th mile?

 

Yeah , but mine with the two twins starts spooling at 26-2700 RPM and are fully spooled my 3000-3200 rpm.

I know mine is flash stalling approx 4700 rpm in first gear, which is 1600 RPM higher than it should be, but overall on the

top end in third gear it seems to be out 1000 rpm.

I just want some opinions to see if my caculations are correct.