How much RPM drop when locking convertor?

[c&cgn]

Just as the subject says. Just curious if I have what would be considered an efficient convertor before lock-up or not.

I made a few blasts last night and my chip locks the convertor around 80mph which was roughly 4600 rpm last night. The rpm dropped down to 4200 according to Directscan.

So is a 400rpm drop good or bad or ???

Thanks.

 

[c&cgn]

TTT

 

[TurboBob]

Here's the deal, all data applies to third gear.

1, make sure that the preferences in DS are set to 26.1" tire and 3.42 gears.

2, if the converter is locked 100% then MPH x 47.33 = RPM (1% error is typical of DS)

3, so take MPH, multiply by 47.33 and then divide by engine RPM and you will get numbers like .81 (81%) etc.

4, Make 2+ runs unlocked, 40 - AFAP (as fast as possible) then 2+ runs locked. Make several runs locked because sometimes the lockup characteristics change with trans fluid heat. Lock the converter at the same MPH each time. 75 mph is good.

5, make the efficiency calcs at 5 mph intervals for each run. You will notice that the converter tightens as the mph goes up.

Send me the DS files and your results. And post them here.

9.5" converters aren't usually efficient at less than 6000 rpm. Make your runs to 100 mph or more if possible.

Have fun, and drive safe........
(the track is a great place for this testing)
TurboBob

 

[WSLN 6]

Hey Clayton! My converter drops 400rpm as well when locked up. The converter is a D5, but it's loosened up, so it probably is worse than a normal D5. The thing stalls at 2300 or so, pretty sad.
I figure with a 9" converter, 400 rpm drop isn't too shabby. Mind you I'm no converter expert........
My buddies car drops quite a bit more than that with his 9/11 type converter.

 

[c&cgn]

Originally posted by TurboBob
Here's the deal, all data applies to third gear.

1, make sure that the preferences in DS are set to 26.1" tire and 3.42 gears.

2, if the converter is locked 100% then MPH x 47.33 = RPM (1% error is typical of DS)

3, so take MPH, multiply by 47.33 and then divide by engine RPM and you will get numbers like .81 (81%) etc.

4, Make 2+ runs unlocked, 40 - AFAP (as fast as possible) then 2+ runs locked. Make several runs locked because sometimes the lockup characteristics change with trans fluid heat. Lock the converter at the same MPH each time. 75 mph is good.

5, make the efficiency calcs at 5 mph intervals for each run. You will notice that the converter tightens as the mph goes up.

Send me the DS files and your results. And post them here.

9.5" converters aren't usually efficient at less than 6000 rpm. Make your runs to 100 mph or more if possible.

Have fun, and drive safe........
(the track is a great place for this testing)
TurboBob

Ugh. That looks like alot of work

Car ran really strong and we had one of our patented "good air nights" last night. Ended up with 11.38 @ 116.77 mph and 1.55 60'

At that level, with 28" slicks it looked like I dropped about 500rpm when the TCC locked up @ 82 mph. With the TCC lockup programmed into the chip there is no real way for me to test it unlocked, is there?

I'll send you the file later today.

Clayton

 

[TurboBob]

There is a switch on the brake pedal that will stop the TCC from locking, it's separate from the brake light switch so you can prevent TCC and still have brake lights.

I have to look which one it is, but that would be the easy way....

I look forward to the file.

What RPM will your converter stall to at Zero psi, 5 psi and 10 psi?

Who built it??

Thanks!

Bob
Double check the preferences in DS for tire size and gear ratio, let me know what they are.

 

[TurboDave]

For what it's worth my vigilante drops 1400 rpm at it's lock point about 70 mph at WOT.

With that and the 26" tires, I cross the line at about 5200 rpm on a typical 117 mph run.

My shifts are also a consistent drop, each being 800 rpm.

My tranny is still perfect, but still the rpm drop when the TCC locks is much steeper and quicker than the tranny shifts.

Your rpm drop when TCC lock occurs depends entirely on the quality of the clutch(s) and clamping force applied.

 

[TurboBob]

Well,

Assuming both Dave's clutch locks completely and Clayton's does too then the RPM drop ammount will be dependent on converter coupling efficiency at the lock point. The later you lock it the more efficient the converter is at the lock point.

Both of you try it......

And send me the DS files both locked and unlocked runs. To 100+ if possible. The DS will tell the tale.

Bob

 

[TurboBob]

BTW 80 mph at WOT with my Yank converter is 4800 rpm or so. 78% coupling which is typical for 9.5" converters at that RPM.

Locked it is 3800. so it drops about 1000 RPM.

So, Clayton, either your converter is extremely efficient, or it's not locking completely.

(Or your data is wrong)

BTW the converter gets into the 90's efficiency above 100 mph or so....


Bob

 

[TurboDave]

I can't find a single file that I save where the converter was left unlocked for the entire run

Since I'm a lock up freek all my runs are made locked at either 70 or 80

I checked all of them at 100 mph and they're all pretty consistent with the vigilante, and show about 4700 rpm at that speed
Probably can't gather much from a file with the clutch locked since the coupling efficiency should be at 100%

I did find one run on my old D5 (remanufactured to be a little looser than stock) with it unlocked, and it showed 5,050 rpm at 100 mph

BTW, I even found a run that I had recorded off Neal Stewards 650HP stage II motor. He also runs a vigilante. At 100 mph his rpm was also 4700, or at least pretty close because he locks his at about 99 mph

 

[UNGN]

117.5 on 26" tires and a stock longblock? That's a poster child for 28" tires. You'll pick up 3 mph minimum.

 

[TurboDave]

Originally posted by UNGN
117.5 on 26" tires and a stock longblock? That's a poster child for 28" tires. You'll pick up 3 mph minimum.

Don't I know it !!! It's just that my racing budget didn't have any room for a set of wheels and tires. I was racing on 16x8" GNX replica wheels and 16" M/T ET Streets 26x11.50
The wheels were old one's I had laying around, so the tires are all that set me back.

 

[Iceman]

I just checked 4 DS runs with my conv.locked and at 100mph 4900 to 4950.

 

[Iceman]

Also I am running BFG DR's 275/50/15

 

[c&cgn]

Originally posted by TurboDave



Don't I know it !!! It's just that my racing budget didn't have any room for a set of wheels and tires. I was racing on 16x8" GNX replica wheels and 16" M/T ET Streets 26x11.50
The wheels were old one's I had laying around, so the tires are all that set me back.

Dave,

I just went to the new Hoosier 28x10x16 slicks that came out recently. This was my first time running them at the track this past weekend. They were good enough for a 1.55 60' and that was the only timea really tested them. The other runs were really soft launches because I was trying to stay out of the 11's since I don't have a bar yet.

 

[c&cgn]

I just checked my 11.38 run and @ 100 mph I was at 4925 rpm. The drop on that run was 550 rpm and that was with the chip locking the TCC @ 81 mph and 4925 rpm. I wonder if locking it a couple mph later would be better?

BTW Bob, I sent you the DS file. I look forward to your feedback.