Thorney Island Drag Racing...UK 928 RECORD TAKEN :)
07-14-2010, 11:31 PM
#47
Rennlist Member
MK You are making the power, the problem is getting these to launch. With a good set of slicks you should see low 12's and high 11's all day but your gearing isn't set for a good 60ft time. Your final drive is 2.20 or 2.7 somewhere around there, guy's that are only concerned w/ going straight for a 1/4 mile have a minimum of 4.10's.
I still feel that the 1/4 mile track is a great way to gauge your performance. For me it helps to see what gains I get with each mod I do. I really don't think it is so hard on the car. I pretty much roll off the line and then gun it, then I bring her through the gears. Think about what you put your car through. These cars are really tough and do not mind a beating, they were designed well.
I still feel that the 1/4 mile track is a great way to gauge your performance. For me it helps to see what gains I get with each mod I do. I really don't think it is so hard on the car. I pretty much roll off the line and then gun it, then I bring her through the gears. Think about what you put your car through. These cars are really tough and do not mind a beating, they were designed well.
07-15-2010, 11:03 AM
#49
Three Wheelin'
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07-15-2010, 01:57 PM
#50
Burning Brakes
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Example
for auto trans car.
fixed number is 355
(1st gear in old 70's performace cars trans varied maybe 2.45 to 2.55
example will be with rear ratio of 3.73 rear ratio and 2.45 1st gear )
example of 928 auto is with 2.20 rear ratio and 3.67 1st gear
Gear ratio was from:
http://members.rennlist.com/pirtle/s4atrans.htm
rpm*tire height/355*rear gear ratio*transmission gear ratio=mph
Can use this for each gear and any tire size at specified rpm
There are probably spreedsheets to do it but this is from what I used back in the 70's
when racing and changing gears etc.
Its about the same as an older cars from 70's with 3.73 rear end ratio with 28" tall tire.
3spd auto trans was 2.45 1st gear
example older 3spd with 3.73 rear end gears and 28 inch tall tire with 2.45 1st gear in transmission
6000rpm*28" tire / 355*3.73 gear ratio * 2.45 1st gear in auto trans=
168000/3244.2=51.78 mph for 1st gear
1987s4 with 2.20 rear ratio and 25" tall tire with 3.67 1st gear in transmission
6000rpm*25" tire/355*2.20*3.67
150000/2866.27=52.33mph in 1st gear
Its close to the same as old performace cars from the 70's with 3.55 to 3.73 rear end gears being an auto trans also with around 2.45 1st gear running the 28" tall tires.
Most cars back then had 27 or 28 inch tall tires.
07-15-2010, 02:15 PM
#51
Rennlist Member
4:10 vs 2.2 is not any indiction of anything. its all about the traction and the overall resultant gearing. a better way to look at it, is redline speed in each gear. my 1st is 55mph redline speed. Its kind of tall, but if you have the power and compliance, it does work. there are many top dragster production vehicles that have 55mph as a redliine in their 1st gears. the key thing, almost as imporant to launch would be the HP-Seconds you can apply. so, if you have a fixed gear spacing, you basically want your final gear to be at redline as you hit the finish because most of the time is spent in that last gear.
118mph in 3rd gear works out to a pretty fast quarter, I would imagine. just add hp to match.
yes, I am making the power and have the weight for a sub 12 quarter. I have some pretty decent launches that I did in WCGT races. (6 of them) but besides practicing for that, and doing some stoplight to stoplight racing in my day, I dont think Im an expert, BUT, i dont get runnaway wheels and i dont bog the engine, so im sure, the car would do pretty well. remember, 2950lbs with me in the car and 335slicks. Ive gone toe to toe with many of the cars that have done low 12s or even high 11s and my car is right there. aside from the launch, many of these cars dont pull on me that much,if at all out of the slow 2nd gear corners. Since the car does 4.7 60-100mph, I would think that 0-60 would be in the same range as well. thats 10seconds to 100mph (0-100mph) 2 more seconds to 110mph and thats 12 to 110mph. You guys are getting me interested in doing a drag test sometime!
118mph in 3rd gear works out to a pretty fast quarter, I would imagine. just add hp to match.
yes, I am making the power and have the weight for a sub 12 quarter. I have some pretty decent launches that I did in WCGT races. (6 of them) but besides practicing for that, and doing some stoplight to stoplight racing in my day, I dont think Im an expert, BUT, i dont get runnaway wheels and i dont bog the engine, so im sure, the car would do pretty well. remember, 2950lbs with me in the car and 335slicks. Ive gone toe to toe with many of the cars that have done low 12s or even high 11s and my car is right there. aside from the launch, many of these cars dont pull on me that much,if at all out of the slow 2nd gear corners. Since the car does 4.7 60-100mph, I would think that 0-60 would be in the same range as well. thats 10seconds to 100mph (0-100mph) 2 more seconds to 110mph and thats 12 to 110mph. You guys are getting me interested in doing a drag test sometime!
MK You are making the power, the problem is getting these to launch. With a good set of slicks you should see low 12's and high 11's all day but your gearing isn't set for a good 60ft time. Your final drive is 2.20 or 2.7 somewhere around there, guy's that are only concerned w/ going straight for a 1/4 mile have a minimum of 4.10's.
I still feel that the 1/4 mile track is a great way to gauge your performance. For me it helps to see what gains I get with each mod I do. I really don't think it is so hard on the car. I pretty much roll off the line and then gun it, then I bring her through the gears. Think about what you put your car through. These cars are really tough and do not mind a beating, they were designed well.
I still feel that the 1/4 mile track is a great way to gauge your performance. For me it helps to see what gains I get with each mod I do. I really don't think it is so hard on the car. I pretty much roll off the line and then gun it, then I bring her through the gears. Think about what you put your car through. These cars are really tough and do not mind a beating, they were designed well.
Last edited by mark kibort; 07-15-2010 at 03:07 PM.
07-15-2010, 02:28 PM
#52
Rennlist Member
So a 2.2:1 928 has a 55mph 1st gear speed with 26" tires. If you wanted to match this proposed, theoretical, optimum ratio (which is really nonsense) then put on a set of 24" tires on the 928 and get the 51mph speed in 1st. Gear spacing is near the same as the old buggers and some of the new. So, then, the 2.2 doesnt seem so bad now does it?
in actuality, you rev the engine up to 5k, dump the clutch and the rpms drop to 4000rpm or so and you count on the slip of the tire for traction as you accelerate forward. all the gearing BS in the world doesnt remove the skill factor and adheasion factor that reallly dictates the acceleration potential.
in actuality, you rev the engine up to 5k, dump the clutch and the rpms drop to 4000rpm or so and you count on the slip of the tire for traction as you accelerate forward. all the gearing BS in the world doesnt remove the skill factor and adheasion factor that reallly dictates the acceleration potential.
You right its over ratio in each gear which include the trans gear.
Example
for auto trans car.
fixed number is 355
(1st gear in old 70's performace cars trans varied maybe 2.45 to 2.55
example will be with rear ratio of 3.73 rear ratio and 2.45 1st gear )
example of 928 auto is with 2.20 rear ratio and 3.67 1st gear
Gear ratio was from:
http://members.rennlist.com/pirtle/s4atrans.htm
rpm*tire height/355*rear gear ratio*transmission gear ratio=mph
Can use this for each gear and any tire size at specified rpm
There are probably spreedsheets to do it but this is from what I used back in the 70's
when racing and changing gears etc.
Its about the same as an older cars from 70's with 3.73 rear end ratio with 28" tall tire.
3spd auto trans was 2.45 1st gear
example older 3spd with 3.73 rear end gears and 28 inch tall tire with 2.45 1st gear in transmission
6000rpm*28" tire / 355*3.73 gear ratio * 2.45 1st gear in auto trans=
168000/3244.2=51.78 mph for 1st gear
1987s4 with 2.20 rear ratio and 25" tall tire with 3.67 1st gear in transmission
6000rpm*25" tire/355*2.20*3.67
150000/2866.27=52.33mph in 1st gear
Its close to the same as old performace cars from the 70's with 3.55 to 3.73 rear end gears being an auto trans also with around 2.45 1st gear running the 28" tall tires.
Most cars back then had 27 or 28 inch tall tires.
Example
for auto trans car.
fixed number is 355
(1st gear in old 70's performace cars trans varied maybe 2.45 to 2.55
example will be with rear ratio of 3.73 rear ratio and 2.45 1st gear )
example of 928 auto is with 2.20 rear ratio and 3.67 1st gear
Gear ratio was from:
http://members.rennlist.com/pirtle/s4atrans.htm
rpm*tire height/355*rear gear ratio*transmission gear ratio=mph
Can use this for each gear and any tire size at specified rpm
There are probably spreedsheets to do it but this is from what I used back in the 70's
when racing and changing gears etc.
Its about the same as an older cars from 70's with 3.73 rear end ratio with 28" tall tire.
3spd auto trans was 2.45 1st gear
example older 3spd with 3.73 rear end gears and 28 inch tall tire with 2.45 1st gear in transmission
6000rpm*28" tire / 355*3.73 gear ratio * 2.45 1st gear in auto trans=
168000/3244.2=51.78 mph for 1st gear
1987s4 with 2.20 rear ratio and 25" tall tire with 3.67 1st gear in transmission
6000rpm*25" tire/355*2.20*3.67
150000/2866.27=52.33mph in 1st gear
Its close to the same as old performace cars from the 70's with 3.55 to 3.73 rear end gears being an auto trans also with around 2.45 1st gear running the 28" tall tires.
Most cars back then had 27 or 28 inch tall tires.
07-15-2010, 02:42 PM
#53
Rennlist Member
SQLGUY You are right, I had the wrong weight. They are 3600lbs, I was thinking of my Lincoln Mark V111 that is based on the same platform. They are a heavy car but still move pretty good. Most of the Thunderbird SC guys are running stock interiors. The ones trying to get to go really fast start to gut them out. The majority are street cars in street trim.
I agree w/ the relationship in regards to final drive and tranny, but in the end 3.73 gears would not be my choice for a STRICTLY 1/4 racer. Also the suspension has everything to do with a good launch when drag racing.
I agree w/ the relationship in regards to final drive and tranny, but in the end 3.73 gears would not be my choice for a STRICTLY 1/4 racer. Also the suspension has everything to do with a good launch when drag racing.
07-15-2010, 02:53 PM
#54
Rennlist Member
Again, the 3.73, or the 4.10 means absolutely nothing without the overall ratio for 1st.
if its 55mph in 1st, its almost identical to the 928 2.2 ratios. (im sure that is near the same for many 4.10 cars and could be for some 3.73s as well)
if its 55mph in 1st, its almost identical to the 928 2.2 ratios.
(im sure that is near the same for many 4.10 cars and could be for some 3.73s as well)
07-15-2010, 04:45 PM
#56
Rennlist Member
If you had a 5.0 mustang and had 2.73 gears in the rear, if you switched to 3.27, 3.73 or 4.10's it would have a big effect on the way the car drives.
Robb my friend has a twin turbo mustang that he races professionally. He does the 1/4 in 6 sec. I don't think he has 3.73 in the rear do you?
1/4 mile gearing and let say top speed bonneville gearing are at the different ends of the spectrum!
Robb my friend has a twin turbo mustang that he races professionally. He does the 1/4 in 6 sec. I don't think he has 3.73 in the rear do you?
1/4 mile gearing and let say top speed bonneville gearing are at the different ends of the spectrum!
07-15-2010, 06:47 PM
#57
Burning Brakes
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So a 2.2:1 928 has a 55mph 1st gear speed with 26" tires. If you wanted to match this proposed, theoretical, optimum ratio (which is really nonsense) then put on a set of 24" tires on the 928 and get the 51mph speed in 1st. Gear spacing is near the same as the old buggers and some of the new. So, then, the 2.2 doesnt seem so bad now does it?
in actuality, you rev the engine up to 5k, dump the clutch and the rpms drop to 4000rpm or so and you count on the slip of the tire for traction as you accelerate forward. all the gearing BS in the world doesnt remove the skill factor and adheasion factor that reallly dictates the acceleration potential.
in actuality, you rev the engine up to 5k, dump the clutch and the rpms drop to 4000rpm or so and you count on the slip of the tire for traction as you accelerate forward. all the gearing BS in the world doesnt remove the skill factor and adheasion factor that reallly dictates the acceleration potential.
You know a stock 928 motor with an auto trans with 2.20 gear ratio doesn't have enough torque to pull the skin off a grape on the launch off the line so traction isn't the problem.
2" tire height is equal to about .34 over gear ratio
07-16-2010, 11:25 AM
#58
Drifting
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Congratulations on the record, Brett. A two-finger salute to your critics!
Good job and looking fotward to hearing about your quest for top speed.
Crank it up!
Good job and looking fotward to hearing about your quest for top speed.
Crank it up!
