A4 1/4 mile question.
09-27-2009, 10:58 AM
#1
A4 1/4 mile question. I also posted this in the 10 sec section, but perhaps it should have been here.
In the 10 sec 1/4 section, I found lots of A4 combinations listed, in general it looks like the following is typical:
3500-3800# cars
450-550 hp
27-28" tall tires
125-130 trap speed
Most are geared with 3.73 or 4.10, but a few are running 3.42
Assuming 27.5" tires & 125 mph trap speed:
3.42 rear = 5200 rpm in Drive, 3650 in OD
3.73 rear = 5700 rpm in Drive, 4000 in OD
4.10 rear = 6250 rpm in Drive, 4400 in OD
So, I assume that every combination I looked at is just running the car out in 3rd gear? Am I wrong on this?
Any A4 cars running a 4.8x rear gear and running out in 4th? With a 4L60E that would be around 5200 rpm @ 125 mph
I had a 1980 malibu with a 700R4, 468 BBC, 4.88 Dana 60, 31" Tires. It ran mid 11's, but I couldn't get it to stay in 4th gear at full throttle, so I only ran about 115 mph trap speeds.
In the 10 sec 1/4 section, I found lots of A4 combinations listed, in general it looks like the following is typical:
3500-3800# cars
450-550 hp
27-28" tall tires
125-130 trap speed
Most are geared with 3.73 or 4.10, but a few are running 3.42
Assuming 27.5" tires & 125 mph trap speed:
3.42 rear = 5200 rpm in Drive, 3650 in OD
3.73 rear = 5700 rpm in Drive, 4000 in OD
4.10 rear = 6250 rpm in Drive, 4400 in OD
So, I assume that every combination I looked at is just running the car out in 3rd gear? Am I wrong on this?
Any A4 cars running a 4.8x rear gear and running out in 4th? With a 4L60E that would be around 5200 rpm @ 125 mph
I had a 1980 malibu with a 700R4, 468 BBC, 4.88 Dana 60, 31" Tires. It ran mid 11's, but I couldn't get it to stay in 4th gear at full throttle, so I only ran about 115 mph trap speeds.
09-27-2009, 11:24 AM
#3
I have been thinking about the 3.06 first gear in the 700R4 & 4L60, perhaps the typical street driven F body doesn't have enough tire to hold a 3.06 first gear x 4.88 x high stall x 450 hp.
My malibu had a stock iron head big block, & a really cheap converter, but still managed 1.51 60 ft. It probably would have been faster with 4.10 or 4.30 gears since I couldn't use 4th gear.
My hot rod has a 496, 4L80E, 28x11.50 et drags, and a 3.50 rear gear. The converter sucks, but I am going to put in a set of 4.84 gears and see what happens.
My malibu had a stock iron head big block, & a really cheap converter, but still managed 1.51 60 ft. It probably would have been faster with 4.10 or 4.30 gears since I couldn't use 4th gear.
My hot rod has a 496, 4L80E, 28x11.50 et drags, and a 3.50 rear gear. The converter sucks, but I am going to put in a set of 4.84 gears and see what happens.
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09-29-2009, 02:38 PM
#10
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like others have said you want to go through the traps in third.i have hit od in 4l85e going through the traps but yes it slows you down.just optimize your gear/wheel tire combo to go thru in 3rd gear.
09-30-2009, 03:16 PM
#11
I question the quest to be in OD thru the traps, (I'm thinking MPH?). OD is good for 2 things-gas mileage and top speed, (well beyond the 1320' mark). The trans has to be modified to hold in OD with the HP and Torque you are making as it was not designed to hold high HP and Torque. The advantage of the 60-65E is the 3.06 first gear. Tune for the end of the 1/4 approx 50-100RPM before your HP Peak in high gear-(3rd).
09-30-2009, 09:44 PM
#12
My hot rod has a 4l80e. It only has a 2.48 first gear, and a .75 OD, but on the good side it has a bigger OD setup, and probably can handle more power than the typical OD of a 60e
Just to match the launch gear reduction of a 4l60E with 3.73 gears, my car needs to have 4.60 gears in back, but my motor doesn't like going past 7000 rpm, so if I stay in third I can only run about 125 (the same mph as I have now with 3.50 gears in back running out in third @ 5200).
My car runs 11.05 as is, and I would really like to get into the 10's
Just to match the launch gear reduction of a 4l60E with 3.73 gears, my car needs to have 4.60 gears in back, but my motor doesn't like going past 7000 rpm, so if I stay in third I can only run about 125 (the same mph as I have now with 3.50 gears in back running out in third @ 5200).
My car runs 11.05 as is, and I would really like to get into the 10's
09-30-2009, 10:00 PM
#13
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It shifts about 100' or so before the 1/4 mile stripe.
I have about 65-70 1/4 mile Runs on it. Left in 3rd only, lowered et's about .05 and 1 MPH.
10-02-2009, 01:06 PM
#15
My hot rod has a 4l80e. It only has a 2.48 first gear, and a .75 OD, but on the good side it has a bigger OD setup, and probably can handle more power than the typical OD of a 60e
Just to match the launch gear reduction of a 4l60E with 3.73 gears, my car needs to have 4.60 gears in back, but my motor doesn't like going past 7000 rpm, so if I stay in third I can only run about 125 (the same mph as I have now with 3.50 gears in back running out in third @ 5200).
My car runs 11.05 as is, and I would really like to get into the 10's
Just to match the launch gear reduction of a 4l60E with 3.73 gears, my car needs to have 4.60 gears in back, but my motor doesn't like going past 7000 rpm, so if I stay in third I can only run about 125 (the same mph as I have now with 3.50 gears in back running out in third @ 5200).
My car runs 11.05 as is, and I would really like to get into the 10's
Can you remove weight? 100lbs is a tenth-10.95.
10-03-2009, 12:16 PM
#16
Last night ran 10.62 @ 127 in third, then 2 runs 10.80 @ 123 in OD, converter not locked.
More specs: 496 bbc, .620 roller, 8-71 (12 psi), solid roller, 4L80E, hacked stock converter (stalls around 4000), used slicks 28x10.5 @ 12 psi, 9" with 3.50 ratio & spool.
Chopped 46 ford coupe, 3800# with driver.
I am not a very good driver, my launch isn't really sorted out, I just let it idle (900 rpm) until the last yellow is on then let off the brake an smash the gas. The car spins off the line, and then spins again (more) when I go into second gear.
I only put it on a chassis dyno one time,
510 hp@5800,
580 torque@3800
The Air/Fuel on the dyno was 10:1 above 5000 rpm, since then I have made some changes to the carbs (two 750 AFB's)
Car #845F, but don't look if you are going to make fun of my R/T
More specs: 496 bbc, .620 roller, 8-71 (12 psi), solid roller, 4L80E, hacked stock converter (stalls around 4000), used slicks 28x10.5 @ 12 psi, 9" with 3.50 ratio & spool.
Chopped 46 ford coupe, 3800# with driver.
I am not a very good driver, my launch isn't really sorted out, I just let it idle (900 rpm) until the last yellow is on then let off the brake an smash the gas. The car spins off the line, and then spins again (more) when I go into second gear.
I only put it on a chassis dyno one time,
510 hp@5800,
580 torque@3800
The Air/Fuel on the dyno was 10:1 above 5000 rpm, since then I have made some changes to the carbs (two 750 AFB's)
Car #845F, but don't look if you are going to make fun of my R/T
10-03-2009, 05:28 PM
#17
Was 5800RPM your HP peak or was that the best the dyno operator got that day? You can lean down the A/F above 5000RPM. Do you have an A/F gauge like Innovate or Autometer? You can do the jet changes yourself at the track to attain the correct A/F ratio. This should add a fair amount of HP and Torque alone, according to the rich A/F ratio. You will also have some suspension work to leave better: firmer rear suspension and dual adjustable front shocks, if not equipped. I assume you have a cage. When you get maximum traction, the motor will be "loaded" correctly to get your true A/F ratio. You will also be able to attain the best timing. You may be in the 9's from what I can see. Basically, you have a 400 w/OD. Forget about the OD. Tune to the first 3 gears, 2.48, 1.48, 1-1. Maybe add a 3.89-4.10 gear to reach your HP peak thru the traps. You have alot left in her. This tuning, (lots of passes), will also make you a much better driver before you know it. Down the road, get a purpose built converter-less rotating mass on the back of the crank. Try leaving at 1800-2200RPM as not to puddle fuel on top of the pistons-no hesitation or hic-ups. Your best air is here (Canadian). Good Luck.
10-03-2009, 06:08 PM
#18
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Was 5800RPM your HP peak or was that the best the dyno operator got that day? You can lean down the A/F above 5000RPM. Do you have an A/F gauge like Innovate or Autometer? You can do the jet changes yourself at the track to attain the correct A/F ratio. This should add a fair amount of HP and Torque alone, according to the rich A/F ratio. You will also have some suspension work to leave better: firmer rear suspension and dual adjustable front shocks, if not equipped. I assume you have a cage. When you get maximum traction, the motor will be "loaded" correctly to get your true A/F ratio. You will also be able to attain the best timing. You may be in the 9's from what I can see. Basically, you have a 400 w/OD. Forget about the OD. Tune to the first 3 gears, 2.48, 1.48, 1-1. Maybe add a 3.89-4.10 gear to reach your HP peak thru the traps. You have alot left in her. This tuning, (lots of passes), will also make you a much better driver before you know it. Down the road, get a purpose built converter-less rotating mass on the back of the crank. Try leaving at 1800-2200RPM as not to puddle fuel on top of the pistons-no hesitation or hic-ups. Your best air is here (Canadian). Good Luck.
10-05-2009, 09:42 AM
#19
Garden City. Unfortunately, I sold the car, and others, to relocate. I am currently looking at another right now for a "street" turbo project. I will design it for long term street and track use, without the huge $$ parts. But, with good quality parts that will survive going to work, weekend or occasional pounding, and serious track use, with out gasket problems, parts breakage, and petty crap. The technology is here and getting better. The convertible was WAY TOO HEAVY!! 4231lbs with me in it. This will hopefully be in the 3300-3500lb range, and somewhere in the upper 9's. Maybe we can get together and BS a bit.
10-05-2009, 04:02 PM
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Garden City. Unfortunately, I sold the car, and others, to relocate. I am currently looking at another right now for a "street" turbo project. I will design it for long term street and track use, without the huge $$ parts. But, with good quality parts that will survive going to work, weekend or occasional pounding, and serious track use, with out gasket problems, parts breakage, and petty crap. The technology is here and getting better. The convertible was WAY TOO HEAVY!! 4231lbs with me in it. This will hopefully be in the 3300-3500lb range, and somewhere in the upper 9's. Maybe we can get together and BS a bit.