Stock Torque Converter and AWD launch

[MuscleJunkie]

So, was having some thoughts about the best way to launch my 2000 Ford Explorer with V8/Borg Warner AWD/Powerdyne XB-1a Supercharger and the 4R70W transmission that had some upgrades when the blower was installed.

As I posted in my last video (in another thread here), the truck takes quickly without any drama when at a standstill and just pressing down fully on the pedal (with O/D button turned off)

With the upgrades I made a couple years ago, the transmission shifts much more crisp than it was when stock. I know I still have the stock converter, so I imagine I am losing about a second or more in time while the truck spools up the revs to 2500/3000 rpm before it starts moving. I'm assuming this is because of the stock converter.

If anyone can explain this more and what would be the best way for me to launch to obtain the best possible 0-60 and 1/4 mile times when I eventually take this thing to the track.

I know I did a crude 0-60 clocking (video below) of the truck before the last pulley upgrade that I measured the time to 60 from the moment the truck started moving (speedo). Did this both with the XB-1a supercharger as well as the BD-11a supercharger. One difference between the pulls was the shift point with the BD-11a was about 5200 and 5400 to 5600 with the XB-1a. With the XB-1a it was in the 5 second range 0-60 (measure by the actual time on the video) and 6 second range with the BD-11a.

I am thinking with the extra boost from the increased crank pulley size (more boost) and 6-rib to 8-rib upgrade (less belt slip) that my 0-60 times should be slightly improved.

 

[97Sandbox]

Back when I was an invincible teenager had an automatic Explorer in which I did a lot of "spirited driving," I would hold my left foot on the brake at the stop light and use my right foot on the accelerator to build rpms up to the point where I could just feel the torque trying to overcome the brakes. Light goes green, left foot off the brake, right foot to the floor, and the lag I think you're referring to was virtually eliminated. This allowed me to get a solid jump on many inexperienced drivers who had much faster cars.

 

[CDW6212R]

I would first try what Grant suggested, that's the easiest method to getting the best jump you can with the existing torque converter. You can't gain a second with a different TC, skip that thought. You might be able to gain 2-3 tenths reasonably, at very high stall speeds you would hate it on the street. So dropping the trans to swap to a $800+ converter might get you some gained time, but I'd put that off until the very end of the project. I plan to use one too, but I aim to do that with the final new engine install(after paint job).

You transmission is shifting higher due to the quicker rpm acceleration, the different power curve. You might want to retune the trans to locate the best shift rpm. The quickest time will be at a higher rpm than the power peak, but the cam is likely costing some power at the upper rpm's too. I plan to test various shift points to locate the one that is quick but not adding excessive extra rpm. I hope for 6k shifting, but if 6300 is quicker with a .10 second better time, I'll drop the shift point from that(reliability is king for me).

 

[410Fortune]

Consider ditching the awd?
Launch in true 4wd instead!!!

Factory converter is weak sauce (or so my trans builder tells me)

 

[MuscleJunkie]

Consider ditching the awd?
Launch in true 4wd instead!!!

Factory converter is weak sauce (or so my trans builder tells me)

I really want to keep the AWD and for the “what if” story of my project, I think Ford would have kept it too.

So far, the folks at Borg Warner say it’s the same type used in the GMC Syclone. Also read here there was a guy (Turdle or???) who was running it and it withstood 500+hp

 

[Turdle]

For street only machine, I like the Awd .

4406 is not as " smooth" sounding, also weighs more.
Honestly, it was fun chirping all 4 tires.

I switched for low range capability for slow climbing Colorado mountain roads. No low range will cook the transmission in that scenario.

I believe the stock converter flashes at 1800-2000 rpms. 2500-2800 might help,


In 2wd, with added power, wheelspin goes from heh- heh to annoyance very quickly.

 

[410Fortune]

Troll was pushing 400hp (crank) and launching with the awd t case
The cyclone/typhoon uses a similar 70/30
Split awd yes
Where awd is good 4wd is better imo
A lot of wasted energy with a viscous clutch and it’s generated as heat

 

[CDW6212R]

Consider ditching the awd?
Launch in true 4wd instead!!!

Factory converter is weak sauce (or so my trans builder tells me)

The factory converter is great for the stock or mild power, I'm sure your trans guy is talking about the lock up clutches. Stock converters wont be good for serious power, the lock up is weaker than nice aftermarket stuff. That's rarely tested because few people run WOT and command the lock up at the same time.

I haven't heard of an official stall speed, I would guess it's over 2000 easily, it launches way better than a stock AOD converter.

The AWD is a resistance device, it does not resist equal drive shaft speeds. So unless a tire is spinning, the viscous clutch should not develop any extra heat. That being true, it does make heat when the front wheels are turned a lot, so low speed turns create heat for sure.

I was told the GM NP 149 AWD case is used regularly for 500+ hp, in early 2000's GM trucks built for power. I got that from a transfer case builder by phone, Zobota I think it's spelled. I may try to fab a trans extension to make use of one of those, if the input shaft can be made with a 31 spline count. They make it now in 27 spline(stock), and 32 spline for those modified GM trucks(using a popular trans instead).

 

[MuscleJunkie]

Put together a new in truck video of some crude initial 0-60 testing on my 2000 Ford Explorer V8 with a Powerdyne XB-1a Supercharger. These are the new results after the custom crank pulley upgrade (a 1st on a 2nd Generation Ford Explorer)

Had some belt slip in the upper rpms ( - 1psi of boost) due to coolant contamination and the tune has not yet been finalized (still running rich)



You can see previous 0-60 tests that I did on the same private roads using the same methods and conditions here:

 

[97Sandbox]

Nearly half a second is a pretty big improvement! Another half a second and you'd be in Syclone territory -- which isn't really a fair comparison because those weigh so much less.

 

[MuscleJunkie]

One of my original objectives with the performance enhancements on my Explorer was to match the performance of a 2006 Jeep Grand Cherokee SRT8

I had the privilege of driving one of these at VIR during the SRT experience several years ago.

To see how I am doing I put together this crude video as a comparison of 0 to 60

 

[410Fortune]

Isn’t the Chevy awd passenger side drop?
06 srt8 is no slouch that’s for sure!!!

 

[Josh P]

Isn’t the Chevy awd passenger side drop?
06 srt8 is no slouch that’s for sure!!!

There was a few years of drivers side drop. It has the same bolt pattern as the ford, Mopar.

 

[MuscleJunkie]

There was a few years of drivers side drop. It has the same bolt pattern as the ford, Mopar.

What does it mean "drop"??? Thanks!

 

[Josh P]

What does it mean "drop"??? Thanks!

The front driveshaft being drivers side or passenger side.

 

[MuscleJunkie]

The front driveshaft being drivers side or passenger side.

Thank You....

 

[Josh P]

How much power will the stock converter handle locked up?

 

[MuscleJunkie]

How much power will the stock converter handle locked up?

To be honest, I have no idea. Last dyno I am putting out mid 400's at the motor. Stock Converter still but trans was built up.

 

[CDW6212R]

How much power will the stock converter handle locked up?

In normal use the converter doesn't lock up, but WOT is different. High performance vehicles typically do lock up in the upper gears. I don't know if these Explorer 4R70W's are programmed to lock up in 2nd or 3rd gear, I doubt it. 4th gear is no issue since that's the OD band and cannot handle WOT ever.

So for racing it only has three gears, you have to reach 1320 feet before you run out of 3rd gear. Jim has stock 3.73 gears so he might be getting close now to its limit.

 

[MuscleJunkie]

In normal use the converter doesn't lock up, but WOT is different. High performance vehicles typically do lock up in the upper gears. I don't know if these Explorer 4R70W's are programmed to lock up in 2nd or 3rd gear, I doubt it. 4th gear is no issue since that's the OD band and cannot handle WOT ever.

So for racing it only has three gears, you have to reach 1320 feet before you run out of 3rd gear. Jim has stock 3.73 gears so he might be getting close now to its limit.

So what happens when you reach the top of 3rd WOT (with O/D button switched off) and the trans shifts to 4th when it hits some programmed RPM (I think mine has been 5200 or 5500? I've done this many many times for some high top end testing and it all seems to have stayed together..... It continues to pull to a higher speed in 4th.