A while back everyone recommended 4.30 gears in the FD. I used them and it helped my 60ft which helped my quarter mile time.

Now that a lot of FDs are pushing an easy 550HP I see the trend changing to 4.10 gears again. I am around the 550-600HP range (depending on boost) and would like to know what gears to use and why.

A few are doubtful about the 4.30 gears in high HP Fds and I wanted to clear this up.

Thanks,

Anthony

 

i think the logic is something that the lower gearing helps to make more engine exhaust energy which leads to better spooling. how much of that is true and to what extent it makes a difference i dont know.

 

Usually up to 500hp in about anything other than Honda's you want the higher number so you can get the car off the line better. If you were to lighten the car extensively then it would be almost the same thing as gearing it. You're just trying to get the weight moving as quickly as possible. Once you've reached a certain hp level.....500hp+/-.....you don't need the gearing as much now cause the hp is taking over. With the extra power the gear ratio just becomes too damn quick which ends up slowing you down. You almost have to be out of 1st by the 60' which is a slight exaggeration but you get the point.

But there are so many factors involved in this discussion. I think the general thinking is because everyone runs the same size tire. If someone were to switch to a 28" or larger (like myself ) then you could stick with the same 4.30 gears and go from there. Once you've overpowered them and can't or don't want to go with a larger tire then drop down a couple gears.

Dropping down a couple gears in a turbo car helps put more load on the engine which helps the car get under boost quicker. Just be ready to retune your whole suspension setup when you do.....it's a handful.

 

Anthony,

look at your rpm at the end of the quarter. If you have more left change your gears.
You want to be at redline or just under by the end of the quarter.

Or keep your gears and make more HP... lol..

 

thats the best way to do it right there.....

 

Well in simplistic terms you have to basically make sure that you're using the engine's powerband as you go down the track in every gear. You want to be in the engine's powerband as much as possible, and ending the 1/4 mile at the end of the powerband of your engine while going through the speed traps. In a street ported rotary turbo engine you should be ending the 1/4 mile traps at about 7-7.5k rpms with YOUR specific setup. Note: THIS IS NOT THE SAME FOR EVERYONE!!! Factors such as porting, how much HP you're making and also turbo size dictate this.

 

NOTE: I forgot to say that tire size will also effect this.

 

That's the really neat thing about high boost drag cars, they work backwards and you can need taller gearing to go quicker. Silly load-dependent whirly thingies.

Of course, my gut feeling is, make the turbo more responsive and sacrifice HP for acceleration... but there are too many factors for it to be that simple.