Torque converters and rpm

[Quickstop [UK]]

I have been looking at my logs and am a little anxious that I have the wrong TC in my truck.

If I apply throttle with no brakes, I can reach 2400 rpm before the truck starts to move. This is the flash stall I believe.

If I apply brakes, I have seen up to 3700 rpm and 13psi (on DM) but I have also had the truck brake boosted up to 25 psi (the wastegate needs dialling in - above 15 psi the turbo spools incredibly fast). I'm guessing that's around 4200rpm. I would have thought that I would reach the brake stall before then or the wheels would turn and beat the brakes.

Some people say that they spin tyres at 5psi and a 25psi launch would be uncontrollable.

The fact that mine appears to leave without spinning and that I can make so much boost before a launch makes me think the TC is way too loose. Basically, I think I am losing a lot of power to the high rpm that the engine makes pushing the loose converter. Instead of locking up (hydraulically, not the lockup clutch), the engine is spinning up and the truck isn't going anywhere. (It still seems fast but I think I am losing a lot of tq).

The TC was a billet one from Waller back in 2007. I paid $875 and requested a 2800 stall at the time. I know nothing else about it - there were no markings on it.

So, my question(s) is: when you boost launch, what rpm do you lose traction at?

I'm going to log it today and see what I get. Any ideas what I should be looking for?

What have people asked for and found - ie did you get what you wanted or did you get something better worse than requested? Circle D seem to keep cropping up as a vendor but I'll have to wait a while before I am flush again.

Cheers!

 

[dgoodhue]

Re: Torque converters and rpm

The 9/11 converter seems like they are on the loose side from my experience and what i have read. I had a 2800 rpm 9/11 stall and it ran like your 9/11 does. IIRC you have a gt35r turbo with Vortecs and cam. You probably would benefit from a tighter converter but you could run it as is. Some trucks with stock heads & cam will run into an issue where after them shift points, the converter is slipping at the next shift. You should have enough rpm range where this isn't an issue for you.

I ended up changing my 9/11 to a slightly tighter converter.

 

[bigmileage]

Re: Torque converters and rpm

You should try testing flash stall with it moving. I usually like 2nd or 3rd gear best (OBDII tuning software makes this really easy), manually command a gear and then throttle in hard, where the RPM flashes and trucks moves is where the actual design converter stall is. Sometimes it will flash where it should from a dead stop, but not all the time. Best performance rule of thumb on converter stall is peak torque minus 200 RPM - typically.

 

[TYTILIDIE]

Re: Torque converters and rpm

How does the truck feel? I'd say that is the most important thing. If you feel like you're losing out then maybe switch it. That is how my wife's 9/11 acted but I liked it as I felt like it pulled hard for the set up we had on it. My truck with the 80e also acted the same way as it has a 9/11 and I had no complaints. FWIW, I drove around on a stock80e converter while I was waiting for my 9/11 and after installing the 9/11 with 3700 stall I really thought the top end felt better with the new converter. So you might not get what you think by tightening it up regardless of what some people try to stuff down your throat. If your truck doesn't move at 2000 RPM literally and waits to see 2400 then I would say maybe it's too loose but all my high stall converters move when you hit the gas but will flash up to the 2000 + area.

Of course this is only my experience. I would bet most people simply wouldn't know the difference.

Just noticed you're blue name, congrats buddy!

 

[Quickstop [UK]]

Re: Torque converters and rpm

Thanks guys, good info.

It basically doesn't feel as fast as I think it should be. There's no massive push into the seat and when I give it gas on the freeway, it feels mushy.

I was following a pretty standard car up a steep incline and I gave it some gas - I expected to catch up quickly but I just made a lot of noise. It's definitely powerful but the connection to the trans seems weak.

The other option is that my 80e got rebuilt wrong and it's on it's way out :rotf:

Once it spools above 15psi, the GT35R wakes right up - almost too much, but below that, it seems real laggy.

Maybe I am used to the manuals in the UK.

I just want that feeling of being pressed into my seat, you know?

 

[TYTILIDIE]

Re: Torque converters and rpm

Thanks guys, good info.

It basically doesn't feel as fast as I think it should be. There's no massive push into the seat an when I give it gas on the freeway, it feels mushy.

I following a pretty standard car up a steep incline and I gave it some gas - I'd expect to catch up quickly but I just made a lot of noise. It's definitely powerful but the connection to the trans seems weak.

The other option is thar my 80e got rebuilt wrong and it's on it's way out :rotf:

Once it spools above 15psi, the GT35R wakes right up - almost too much, but below that, it seems real laggy.

Maybe I am used to the manuals in the UK.

I just want that feeling of being pressed into my seat, you know?

Personally, it sounds normal to me for that size turbo.

 

[BMFB]

Re: Torque converters and rpm

eh I dont know. I run a T76 on a 3800 and its pretty peppy....

Flash is where the converter stops slipping. So, to test flash you wan to be in second gear or something going 35 and floor it. its not when the truck starts moving, its where the engine and trans become 'attached'.

stall is simular, but while your parked. For instance, when you try to boost launch, where your RPM's end up. You will find that the more power you put against it the higher it will stall. it might initially stall at 2600, but when you look back at your logs you could see that it started at 2600 and climed to 3400 before you started to actually have any mph.

 

[Quickstop [UK]]

Re: Torque converters and rpm

It would be interesting to compare G forces/acceleration between trucks. I have been in Rene's truck and that thing pins you to the seat and leaves you breathless - possibly the fastest truck I've ever been in - I dunno.

:dunno:

I guess I need to dyno it and see what I've got. Or log the 80e with the PCS software and see rpm vs shaft output and measure slip in the TC... 10% is acceptable in a good TC allegedly.

 

[BMFB]

Re: Torque converters and rpm

Just lock the converter at 35 mph, problem solved

 

[Don W.]

Re: Torque converters and rpm

Here is a little video that explains it well and quickly.

https://www.youtube.com/watch?v=WSmdDX3T1l8

:2cents:It's my belief that all our trucks are different. (Except the unmolested ones I guess.) I had a custom converter built a few years ago. Using the footbrake method it stalled 3200. I had ordered a 2800. I had to have it re-stalled. The builder didn't realize how much power we make. Different HP and torque will give a different stall as I understand it. Apparently the flash stall method is more accurate but nailing the RPM would take some trial/practice runs.:2cents:

 

[Quickstop [UK]]

Re: Torque converters and rpm

Thanks Don - I have a feeling I'll be doing something similar.

Cheers!

 

[Quickstop [UK]]

Re: Torque converters and rpm

Just lock the converter at 35 mph, problem solved

I'm thinking this might be a solution or at least part of one. Any ideas how to calibrate it?

My PCS controller calibration has the lockup starting at 53mp at 0% TPS and heads steadily up to 140mph at 67%.

All the other TPS values are greyed out above 67%/ above 255 mph so it'll never lock up above 67%.

What I would prefer is TCC lockup based on RPM, not speed...

How do you think it would behave if I had it set to lockup at low speed/low tps then had it unlock at higher tps and then lock again at high tps/high speed?

How should I set this up - I want to benefit from spool up in all gears but also have the tq transmitted at a lower rpm than my stall perhaps allows. I guess I need to think about it.

 

[bezerk]

Re: Torque converters and rpm

your truck is just slower than mine

 

[BMFB]

Re: Torque converters and rpm

well unfortunetly I dont have any experiance with that controller and what it can do.

For what ive done with my stuff...

the 700R4 is a solinoid, and I chose to lock it at 47 mph under wot (I think, thats close). The idea is to lock it in the middle of second gear, and it basically gives me another gear when it locks, and being a direct link from otor to trans I can feel a gain in power, and pick up a few mph at the end of the track.

for normal throttle (35% and under I believe) I set it closer to 35mph for the lock/unlock threshhold. Those speeds and tps settings have treated me pretty well thus far.

For what your doing its tricky because I dont know what your stuff can take. If your converter is strong enough to go full lock under wot conditions I say go for it (you paid 900 bucks for it, so it might have a good lockup clutch in it).

I would say for normal cruising set it up alot like mine, have it lock around 35 mph under light throttle. Go with a higher duty cycle, closer to 85%, and have it ramp fast. Since you have a bigger turbo, maybe dont have it unlock until higher throttle %'s, like 50% throttle.

That senario would be like if you were cruising at 55 and wanted to pass someone. you get into the throttle and if the converter unlocks your going to feel that truck kinda fall on its face. You want to keep that converter locked during that whole thing so that your not having your big turbo higher stall converter turning all that low end torque into heat instead of forward motion.

For WOT, if you can lock it early like I do at 50ish, do it. Ramp pretty fast, like, within 8 mph to a higher duty cycle (at least that 85%) and hold it out.

Hopefully that helps, if you need any other things let me know. Sorry for the slow response

 

[Vaders Sy]

Big Turbos and TC

Big Turbos and TC

You want to keep that converter locked during that whole thing so that your not having your big turbo higher stall converter turning all that low end torque into heat instead of forward motion.

For WOT, if you can lock it early like I do at 50ish, do it. Ramp pretty fast, like, within 8 mph to a higher duty cycle (at least that 85%) and hold it out.

Hopefully that helps, if you need any other things let me know. Sorry for the slow response

I just got my Sy together and I noticed my transmission temps are about 20-25 degrees warmer than in the past. Your comment got me thinking. For bigger turbo's you want it to lock sooner (mph) to reduce transmission temps? Another drag racing fellow suggested to have my TC lock at 70 or not at all to increase mph. I was always under the impression that sooner the TC locked MPH went up by 1-2 MPH in the 1/4. I guess some explanation would help on this TC business.

Admittedly, my radiator does not cool the transmission fluid anymore, it is routed to a transmission cooler instead. Could that be the cause for the higher temps?

I have a 71 billet wheel BB turbo, 4L60 transmission, the EZ-TCU for my transmission is currently set at 50 mph for lock up.

 

[Quickstop [UK]]

Re: Torque converters and rpm

BMFB - Thanks for the input - that makes a lot of sense. It sounds like your TC control is actually more flexible than mine.

I need to log it and have some thoughts. I think a dyno will tell me some interesting things as well. Just need to get it onto one!

 

[Quickstop [UK]]

Re: Torque converters and rpm

So I decided to log my transmission tonight and it doesn't make for good viewing

:tdown:

I took the truck out for a spin and used the PCS software to datalog the 4l80e that I have in the truck. Everything works well but the TC and stall are way off what I was hoping for.

First pic: Truck is stationary

I have 5 criteria selected in the datalog. RPM, turbine speed, TCC slip, MPH and MAP

The red vertical line at the left of the pic is what I am referring to. Note the truck is at idle - 0mph (green), idling at about 900 rpm (white). 0% slip (yellow) because the trans isn't turning and nor is the turbine. MAP is normal.

Second: Accelerating from rest

Vertical line moved to the right. Note how the RPM climbs rapidly (the white line) but the turbine in the TC climbs a lot more slowly. This says to me that it is loose, certainly at this RPM. Speed also climbs in accordance with the TCC. If you follow the white line up, you see the yellow line (slip) descend and they cross at about 2800 rpm. This is the RPM that I desired the TC to stall at. Note the PSI at that point. It's 4.5. The slip when they cross? 47%

Third: Finished accelerating,

As we move up the white RPM line, the purple turbine speed line follows it up, gradually closing in... the yellow (slip) line decreases until I let off the gas at about 34 MPH and the RPMs drop. This is because the truck changed to second gear and I let off the gas. The TC gets within 18% of the truck RPM.

I am not even at WOT. The TPS line (I didn't include it here because there are already too many curves) shows that I barely reach 55% TPS. *I do manage to get to 22 psi but the slip is still around 20-30% at that point. *This is at 4400 RPM.

Basically, my TC is loose as hell. A good TC should have no more than about 10% slip when it is stalled or so I have read. That should have happened way before 4400 RPM. Hell, my shift point is 5200 in 1st gear! That's only 800 rpm of power being applied.

So it looks like I am in the market for a new TC. I guess I need to put some HYGARD in it first but that stuff is expensive here. $140 for 5 gallons :tdown:

I feel I may be better investing the money in the TC.

:rant:



Can you guys have a look and tell me what you think? Sorry the pics aren't huge. I couldn't get them bigger on my screen.

Kufingc truck.

:rant:

 

[e95 Ty]

Re: Torque converters and rpm

What kind of tc is that again Mark?

 

[Quickstop [UK]]

Re: Torque converters and rpm

Unfortunately, I don't know :dunno:

I paid Waller $900 ish back in 2007. I asked him recently and he said he has no record of the details or the company that he paid to do it. So I have no idea. I have a picture of it ... it was a beautiful piece. I asked for a 2800 stall TC and gave him all the details on my build - vortecs, GT35R. I guessed around 600hp and 600ftlbs tq...Supposedly a triple disc billet brazed anti balloon hub but I am probably guessing now...

Tell me I am not making this up - it looks wrong - am I right?

 

[dgoodhue]

Re: Torque converters and rpm

It's probably a billet 9/11. You can have it restalled to a tighter rpm.