Is there a difference in torque conv. for F/I and N/A????

Lmao!^

 

Ok, I couldn't stand the wait so I did some logs of my own...

Here's the brake stand (No wheel spin). We can see that the stock converter is about a 2200 ~ 2400? stall. Somewhere in there -- probably closer to 2200 but I never broke the wheels loose so there could be a bit more there.



Here is the part throttle launch. See the rpms go up much faster than the speed at first? Right about 1400 rpm is where we can feel it start to accelerate the car so it's starting to transfer a measurable amount of torque. In the next one you can see that right around 1800 or 1900 it's transfering a significant amount of the torque and that's about where the speed starts to increases proportional to the rpm.





This is all fluid dynamics at this point. There's no hard mechanical connection. Think about wading through water. No problem. But if a ski boat trys to drag you through the water you can slow down a really big motor.

My torque converter is about a ~2200 stall and is transferring very little torque down around 1400 rpm and not all the torque up at 1800 rpm. You got a 2800 stall converter and I'd expect it to be almost free wheeling at 1400 - 1500 rpm (see wading analogy above, haha).

What we're considering here is that your torque converter has something to do with your engine bogging around 1400 rpm. If it's a 2800 stall TC then that leaves the lockup clutch ... and that's controlled by the TCM right? and I'm not sure if it's supposed to go from unlocked to locked up while you're in WOT mode?

I'm thinking this. You gradually get it wound up on the dyno. Since you're at partial throttle the TC is locking up at the top of third or after you get in 4th. Now it's locked up, you're under 1400 rpm and you WOT for the run. Car bogs because the locked up TC isn't letting it "free wheel" up to 2500 - 2800. I'm guessing you wouldn't see this if you did a WOT run (on the ground) from a standing start or 2nd gear. (come to think of it, that doesn't make sense since you're going to be around 3700 - 4000 at the bottom of the next gear after a shift anyway... doh).

In any event, TC lockup is TCM controlled right? Would a different TC change that?



...and why would you care what it does around 1400 rpm anyway??? When you launch it's going to go right up to the stall. If you're just cruising at steady speed and it's loafing along at 1200-1400 and you want to accelerate you just bump the shifter to the left once or twice. :huh: I don't see what the problem is.:dunno2:

 

Are you running a stock TCM?

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I am. Chris isn't.

 

Sorry..
I meant Chris.

Is it possible the Mopar TCM was accidently screwed by using the Predator?

Chris... have you made any shifting adjustments with the Predator?

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I can't get my car anywhere near 2200 with the stock Converter

 

Nitto NT05s :thumb:

 

No. The Predator does not currently write to the TCM on our cars. All adjustments like shift points and upshift behavior are PCM parameters. I don't know what inputs the TCM uses to decide when to lock up the TC but the predator cannot change the programming.

Went back and checked the log. 2294 was the max rpm and mostly over 2250. So I think you could call it a 2300 stall TC. I'll have to get another log and go till the tires break loose.

 

I don't think so...
I have been told and read on the forums that if you change shift parameters on the Mopar TCM with the Predator, you will wreck it.
I believe Chris (Trojan) and DiablSsport have told me this.
Let me find the thread...

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Read Here....
http://www.diablosport.com/index.php?name=PNphpBB2&file=viewtopic&t=10877

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Well, you don't exactly "wreck" it. What you will do is turn it into a stock TCM that can't be restored to a Mopar TCM (at least with the Predator).

When you do any of the shift related adjustments with the Predator it sends (either directly or indirectly through the PCM -- I think the latter) a variant string to the TCM. This is a set of parameters sent to the TCM via a TCM api. These parameters will put the TCM in one "mode" or another. This is how they increase shift firmness for the R/Ts. They don't have that for the SRT8s because what they're doing is putting the R/T TCM in SRT8 "mode".

So when you change one of those shift parameters with the Predator it will send the variant string to the TCM and ...voila... you have a Mopar TCM operating exactly like a stock TCM. and the Predator can't put it back.

Exactly. Start reading at my post (#4) and the following 3 posts. :grin:

They don't do anything that effects lock up and since they're going through a TCM api they're not going to be able to accidently effect that either.

 

stock at the moment....

mine is still stock dave! lol

i have not installed my mtcm yet. was thinking of tossing it in to see if it made a difference!

yep, you can flash over a mtcm with the pred and not get it back!!!

i love you man!!! lol

 

Try that. I think I read somewhere that they might have changed the lock up behavior in the MTCM? Log the problem with the stock PCM first if you can (I think it's supposed to rain the rest of the week...)

and about this bog thing. Does it only happen when you punch it at the bottom of 4th? If it's only in a specific gear then that would also suggest lock up.

 

i am going to put the mtcm in this weekend when i will have a chance to take it to my "proving grounds" to do the break in proceedure. the bogging happens just about any time i am at low rpms and give it more than part throttle.....

 

Well... just about anytime you're moving and at low rpms you're going to be in 4th gear if not 5th. try that too. lock it in 2nd or 3rd and get it down to 1400 or less and see if it bogs.

Even if it does, you get anything down to a low enough rpm and it's going to bog. If I'm just cruising on a city street and get down around 1200-1300 and give it part throttle (anything up to where it causes it to downshift which is almost full throttle) it just bogs. and it knocks audibly at the same time... So I got a 2300 stall converter and there's still enough torque transfer down around 1250 to put the engine under enough load that it bogs. I'm still trying to figure out why this is a problem in tuning your car.j.. and I'm not sure swapping your torque converter will do anything.

(jees, if you hadn't pissed off all the mechanics, tuners, and transmission guys here we'd probably have an answer already)

 

This is my understanding of TQ converters.

Any given stall converter will 'stall' at a higher rpm when more tq is applied. That's a fact. If you start with a 3000 stall with 500 ft lbs of tq. Then add 200 ft lbs of tq. It will stall higher. How much higher depends on the quality of the converter you start with. Most times it doesn't matter because you still get the benefit of the lower stall speed under light throttle and the benefit of a higher stall when you need it at launch. Also,, by this point WOT from a stop on the street is pointless and you save it for the track.

Can you use a N/A stall with FI. Yes,, provided it still statisfies your requirements. By that I mean your desired stall speed. Also, the N/A stall needs to be of good enough quality to handle the extra FI, HP/TQ. We destroyed a standard tq converter with too much power. It really makes a mess inside the trans.

As for your bog. It's probably the lock-up. That's comanded by the TCM.

 

great feedback..... thanks!! :grin: