Mark,

You are totally right. Your enemy here is gearing. 996 turbos are not geared for the quarter mile at all well. You want to be at redline in 5th at the stripe. That's going to require a lot more total gearing and much better spacing.Let's say you sort out the launch with a 50 shot, then you want to keep your turbos in the meat at the 1-2, 2-3, 3-4 and 4-5 shifts. So your RPM drop for the total gearing must be optimised to those turbos. That's going to mean custom gearing in your tranny. You also want much more gearing in 1st to get the ***** off the line.

Of course once you've got gearing you need traction. Once you've got traction you'll break driveline. Once you bulletproof driveline you'll want more power. Once you've got more power you'll need traction. Once you get traction you'll need more gearing ...

:-D

 

I recently spoke to a Porsche race car builder about a sequential tranny (he has installed a couple on 996TTs). He said it would be terrible on the street -- loud, rough and generally unpleasant. I have no personal experience with sequential trannies, but I was dissuaded.

Again, it comes down to street cars vs. track cars.

Craig

 

Yes Craig,but that Viper would be as much fun as lesbian twins!You really don't need em both but they sure are nice to have.

 

Craig I have a sequential straight cut tranny in my BMW M Coupe. It is loud (louder than my 5 fuel pumps and twin 4" titanium exhaust without mufflers), it is rough (hard to select gears at low RPMs) and unpleasnant (very difficult to select reverse from neutral).

It also obliterates all other streetable trannies by a margin that makes me laugh. the tranny shifts so hard and so fast that it's honestly worth a good second in ET over an OEM 6 speed.

Your call :-)

 

Not really .. a car set up to make 1200 rwhp is going to be dog**** running 600 rwhp for example. You should engineer the car and it's delivery to match what you're going to use it for. for ultimate street racing status, set it up for street rubber and street traction.

My BMW makes more power than a pro stock racecar. But with street rubber under it there are many street cars that can clean my clock on the street. Because I blaze my tyres in 6th gear while they are off down the road.

 

Wow. Thats amazing. I smell 9's in the near future.

 

Mark,

I don't think you are disagreeing with what I said. I did not mention gearing which of course needs to be stretched to get to your maximum potential trap speed before changing one more gear obviously.

To achieve the highest trap speed, you shift at redline , to achieve best ET you shift at optimum shift point (highest torque a the wheels), in between , you get the best of both worlds. I have the optimum shift points for your car and shared them with Todd a while back.

As far as sequential gearbox, no doubt it is the ultimate thing for this. Here is a graph of my run at 1.1Bar (black line), notice the shifts vs. another very fast 2 shift 60-130mph run... I was not even flat out between shifts as I am not drag racing.

 

Joe you are DA MAN!!

 

Although I disagree...............I have had my *** handed to me too many times by one of these bad boys that supposedly don't put the power down on the street.Most of them have progressive boost controllers for the street and are able to dial down the boost for the lower gears and run lower horsepower but the boost will ramp back up for the higher gears and pull away from me like I am standing still.As a matter of fact there were 2 Vipers at the SECC drag day that Joe (RennTechV12)held last week that were on street tires,not dr's, and pulled like mad on the big end.They black one ran around 10.20's and at 148-152mph.With dr's these are 8sec cars..............I get your overall point!

Sorry Mark,didn't mean to get off topic.....now back to Mark's thread.

 

Very well said Jean... What I was referring is that Im in my 4th only for a 18 mph gain whereas my 3rd was 37 mph and my second was 42 mph gain.
I think that we will do better soon.
those are some nice shifts... wow.

 

Had to put my 2 cents This plus some big DR's is hte key to havinga ton of fun on the street

Great pass MARSKI, best of luck on getting some axles to hold. It's likely the problem is elsewhere in the driveline and the axles are taking the abuse, like anythign though it's always tough to find the missing link, but when you do I'm sure a 9 will be waiting.

 

This is just MHO (as I have no idea where your axel broke) but we had a horrible problem with shafts snapping at the spline/shaft junction when we were building blown fuel motors for drag boats, no matter what alloy we had the shaft made out of they still broke. The final answer was to machine the shaft/coupler with a much bigger radius in the root of the splines as well as a larger radius in the spline/shaft joint. Then this was micro polished and went to heat treat. Bingo....never broke one again....

 

Thats fast...Grats Mark.

What ever happened to all the talk from another member on here about there TT doing single digits in the 1/4?

 

Both shafts at the inboard spline broke.

 

i think the drag radials might be too hard on your drivetrain.. did you try switching out tires to ET streets?