GregBBRD

Awesome!

BC

Spectacular engineering, forethought and execution.

Todd T

I just want to thank you for all the kind words and interest in these projects.

SwayBar

That boy Todd is just downright incredible!

Dave928S

Wow that's impressive!

jeff spahn

I think to get an awesome on this from Greg is quite an accomplishment. He doesn't hand unwarranted accolades.

Shane

That is truely great Todd! Thanks for sharing!

FredR

How do you manage to get the rear wheels to hook up such that you can get to 60 in 3 seconds- presumably some very sticky rear rubber?

SMTCapeCod

++ mass?

BC

Sticky Rubber. And properly staged car at the strip. And essentially years of tuning on the ECU.

ptuomov

When the trap speed is 150 mph and staying constant, the improvement probably wasn't in the engine or its tune, nor is there any improvement needed there. The ET improvement came from the transmission, and additional further ET improvements will come from the same source in the future.

BC

His 60 foot time is reaction time and some other things. After that, yes, there is some transmission room to grow. But also engine and tune. There is always engine and tune - especially with this fuel.

hacker-pschorr

That's a rather oversimplified explanation.
As Todd puts it, making power is easy, it's everything else that is difficult (driveability, traction, reliability etc...). He never wants to build a car his wife won't ride in when they go to dinner, or one that is broken after every trip to the race track.


I think FredR is simply asking how Todd manages to get the car to launch so well, not what he did different between the time slips.

To answer Fred's question, launching a car is all about traction and weight transfer.
In Todd's case:

• Mickey Thompson DOT drag radials mounted on manhole cover wheels widened to 10" in the rear - 255/50-16
• 220lbs pounds of ballast attached under the rear bumper cover
• Careful planning to move the weight bias as far back as possible by removing as much weight off the front of the car. He's calculated the intake manifold and associated hardware alone shaved 15lbs off the front. ABS removed, cruise control hardware removed, windshield washer tank removed, front bumper brace etc..... He's also looking into a manual headlight system to eliminate the motor and associated hardware.
• Extra items installed as far back as possible, like an extra heavy battery and a 4 gallon stainless steel water tank for the IC sprayer.
• PSD differential using a custom controller to lock up under boost

Todd and I often joke around about him building a 911 in a 928 body because when he put the car on the scales, his 928 now has a weight bias of 43/57. Someday he hopes to have it closer to 40/60.

Gross weight is just over 3,900lbs with Todd in the car and all fluids topped off.

When the chassis was stock, and he surpassed 700+rwhp he felt the car was undriveable and unsafe due to the lack of traction with the drive wheels, this was also with drag radials installed. This is when he started on the weight transfer changes to get the rear tires to stick better, it was either that or sell the car (and buy a Nissan GTR) since he wasn't happy with the results at the time. Sure it made power, but it wasn't very fast since all it wanted to do was spin the tires.
He jokes that it only cost him $44 to make the car fast....that is what the scrap steel cost that is attached to the rear bumper.


As for the differences between the two runs

• He went from a 50 shot to 88 shot of nitrous, which is only used for the launch. It automatically shuts off at 4k RPM and never comes back on. As he puts it, this is necessary to "Launch like a supercharged car and limit the lag"
• Modified the torque converter to increase stall speed. As Todd stated, this is the #1 reason for the difference between the runs and why he's building another torque converter to increase the stall even higher
• Nothing was changed with the engine tune except to add more fuel with the additional nitrous off the line

Torque Converter Information:
US 87/88 - 12.25" stall speed 1750 - 2150rpm
US 83/84 - 11.25" stall speed 2200 - 2600rpm

In the first run above, he was using a stock 16V torque converter and when he measured the stall it was between 2300-2400.
In the second run he was using a modified 83/84 torque converter with a measured stall speed of 2700.

He's now working on a Mercedes 190E torque converter which is about 10", he's going to internally modify to a minimum stall speed of 3200rpm and maybe even as high as 3500rpm. He's hoping with this higher stall speed he can eliminate the nitrous since by 3200-3500rpm the turbo's are fully spooled on their own, or really close to it.

The size of the torque converter is important. All things being equal, the smaller the converter the higher the stall speed.

At this time he's only pushing 15.95psi of boost through the engine in 1st gear
2nd gear limited to 21.75psi @ 8,000rpm
3rd gear he's reaching a maximum boost of 25psi.

He knows this car is capable of reaching the mid 9's as it is today, and with some more work he's targeting a 1/4 mile time in the 8 second area. The main change to reach this goal is the modified torque converter, nothing with the engine.

JWise

Thanks for the additional details, Hacker.

This build has all the makings of another fine Panorama article. Alas, I'm afraid a great many 911 heads would explode.

andy-gts

my head is spinning .....wow !!!! pretty cool stuff...!!!