quote:

Originally posted by 369dragster:

quote:

Originally posted by diceman1530:


What rpm do you run in 1/4 ?

Ray I have 4:30's in my car and go thru at 7850 in good air going 7.0's

Exactly what I was looking for, Thanks Ken

quote:

Originally posted by Lenny5160:

Well thanks for doing 3.14 x 33.5 and 34.5, Mr Wizard! Not quite the same as putting a tape around a mounted and pressurized tire.

Seem familiar? LOL

quote:

Originally posted by TOP38:
Here's the magic formula

MPH = (RPM x TD)/GR x 336 Or TD = (MPH x GR x 336)/RPM

where:
MPH = Car's speed at finish line - See time slip! LOL
RPM = driveshaft speed at finish line
TD = Tire Diameter (inches)@ finish line
GR - Gear Ratio
336 = constant to converter units

So you need a data logger to get DS RPM or if you don't have one then you would have to guess at converter slip at the finish line and use engine RPM instead.
So 7000 RPM (engine speed at stripe w/8% slip)
7000/1.08 = 6481.5 DS RPM's

You can measure the tire at the stripe with observed converter slip through the data acquisition, the same as you estimate the converter slip through a converter slip equation,,, gear x mph x 336/Tire diameter. All ya do is adjust the diameter to achieve the observed slip % in the data.

The accuracy is determined by the accuracy of the observed slip %, in the data.

I have a question that somewhat relates here s I hope I'm not completely derailing this. Have any of you guys gone to the 1.58 gear set and stayed with the lower final drive? I'm wanting to do this with my car and although it's much slower than all your dragsters ( 5.60s-5.70s ) I would be interested in results. Did it keep the MPH?

I'm wanting to calm the front half and launch for in the heat but keep the final drive ratio for finish line rpm and not have to run high gear only because of the trans heat. I'm low 1.20s in 60' off the foot. I rarely do any trans brake racing. Thoughts?

quote:

Originally posted by CURTIS REED:
I have a question that somewhat relates here s I hope I'm not completely derailing this. Have any of you guys gone to the 1.58 gear set and stayed with the lower final drive? I'm wanting to do this with my car and although it's much slower than all your dragsters ( 5.60s-5.70s ) I would be interested in results. Did it keep the MPH?

I'm wanting to calm the front half and launch for in the heat but keep the final drive ratio for finish line rpm and not have to run high gear only because of the trans heat. I'm low 1.20s in 60' off the foot. I rarely do any trans brake racing. Thoughts?

That would do exactly what your idea tells you. Highway gear in low, it'll still hustle in high gear. Might lose a 1/2 mph. Just depends on stator in the converter. Below stall the stator is inactive directing oil onto the pump multiplying torque. It'll be below stall longer, depending on converter multiplication vs what your giving up in gear (mechanical)
torque multiplication, it could be it doesnt lose any mph because the drop back at the shift will be less. Might pickup mph. I bet it'll kill 5-8 hundredths in the 60 depending on the same trade of as aforementioned.

quote:

Originally posted by diceman1530:

quote:

Originally posted by TORQIN:
All 3 of my dragsters have 4.30 gears...

What rpm do you run in 1/4 ?

Run very little 1/4 mile...around 7700 to 7900 depending on air conditions.

quote:

Originally posted by Mike Rietow:

quote:

Originally posted by CURTIS REED:
I have a question that somewhat relates here s I hope I'm not completely derailing this. Have any of you guys gone to the 1.58 gear set and stayed with the lower final drive? I'm wanting to do this with my car and although it's much slower than all your dragsters ( 5.60s-5.70s ) I would be interested in results. Did it keep the MPH?

I'm wanting to calm the front half and launch for in the heat but keep the final drive ratio for finish line rpm and not have to run high gear only because of the trans heat. I'm low 1.20s in 60' off the foot. I rarely do any trans brake racing. Thoughts?

That would do exactly what your idea tells you. Highway gear in low, it'll still hustle in high gear. Might lose a 1/2 mph. Just depends on stator in the converter. Below stall the stator is inactive directing oil onto the pump multiplying torque. It'll be below stall longer, depending on converter multiplication vs what your giving up in gear (mechanical)
torque multiplication, it could be it doesnt lose any mph because the drop back at the shift will be less. Might pickup mph. I bet it'll kill 5-8 hundredths in the 60 depending on the same trade of as aforementioned.

I agree with Mikes reply. I have a 3 speed with 2.10 /1.40 planetary and 1+2 brake. Launching in 2nd will have the engine on the convertor stall of 6350 for 2.8 seconds, shift at 7000 and the 1/8 mph almost exactly the same from 1st gear launch. 4.40 diff gear w/ 32x14.

Thanks Mark,

I appreciate your input. He is on ignore so I wouldn't have seen it if you didn't quote it but thanks for your feedback. I'm looking into what exactly I have to buy to do this.

Curtis

quote:

Originally posted by CURTIS REED:
Thanks Mark,

I appreciate your input. He is on ignore so I wouldn't have seen it if you didn't quote it but thanks for your feedback. I'm looking into what exactly I have to buy to do this.

Curtis

That's ok too, because the same performance fundamental apply's across the board for anyone who reads it. Someone WILL pick the ball up and run with it. That's OK too.

I still say according to the fundamentals of automotive performance, Super Pro is King. I made that claim, figuring everyone already knew it as a objective Truth and not a subjective Truth - opinion. We're all conservatives here right? Guess again, eh?

This message has been edited. Last edited by: Mike Rietow,

quote:

Originally posted by diceman1530:
With the M/T tires being so tall is anyone switching to a 4.30 gear. I know they don’t grow like a Hoosier. Most races are 1/8 mile now and I don’t think it would be that much more rpm in a 1/4 mile race. Thanks

What are you hoping to gain from this? If it’s ET or MPH you’ll see very little change if any. 4.11:1 is the sweet spot for 4.60 to 4.80 long cars

Hope you are right.^^^^
After some research (lot harder with FED) I settled on 4.11 with 1.69 low set up. I have three sets of used gears to try later if don't work out. Figure test with used stuff cheap(if not over used) and new when know what works.

quote:

Originally posted by adv ET 266:
4.11:1 is the sweet spot for 4.60 to 4.80 long cars.

Can that really be a blanket statement, Paul?

A 4.11 with a 33.5" tire is essentially the same rolling distance per driveshaft rotation as a 4.30 with a 34.5 - 35" tire that are becoming more popular by the day.

4.30 gear here with 4.50 car.

Tony, If by blanket, you imply it is the only solution, no that’s not what I meant. Of course what I said was to a pretty specific ET range. I have tried 4.56 to 3.90 gears and huge to small roll out slicks and tuned for these changes. All combinations have the good with the not so good, but from my experience the 4.11:1 was the best overall for bracket racing on good to dog **** track surfaces. Do doubt examples of others success exist. My motto was to try changes myself and see what happens. That old adage, paralysis by analysis is often true. If I listened to much of what I read or hear, my cars combination would of yielded far less.

quote:

Originally posted by adv ET 266:

quote:

Originally posted by diceman1530:
With the M/T tires being so tall is anyone switching to a 4.30 gear. I know they don’t grow like a Hoosier. Most races are 1/8 mile now and I don’t think it would be that much more rpm in a 1/4 mile race. Thanks

What are you hoping to gain from this? If it’s ET or MPH you’ll see very little change if any. 4.11:1 is the sweet spot for 4.60 to 4.80 long cars

I am trying to pick up a little,want to keep the motor rpm up a little more. I know I will not get a lot of et but just trying to get the most of what I have.
I like to hear everybody's thoughts.
Thanks for all the replies

quote:

Originally posted by TORQIN:
All 3 of my dragsters have 4.30 gears...

have you ever tried a different first gear?

quote:

Originally posted by adv ET 266:
Tony, If by blanket, you imply it is the only solution, no that’s not what I meant.

I meant, can you state what the sweet spot for gear is without considering tire size?

I recall you running 33.5" tires for the most part. With the Bubba tires being all the rage today, those tires with a 4.10 gear would be roughly the equivalent of you running a 3.90 gear. In that case, is 4.10 still the optimal gear?

I cannot find it, but FTI has a long explanation on different first gear and rear gear ratio’s in a dragster a long time ago.

i used a 4.4 with a little bubba for a while,it was fast for sure ,or should say quick

my preference for the common dragster is 4.3