30-70 MPH times

[KennyT]

I should have included tire size, as that definitely matters like you said. With equal tires the speedo numbers can be compared with relative precision. With different tires you can figure out what gauge mph you need to start/finish at.

The real question is how accurate do you want this to be? tenths? hundredths?

[nando]

there's no way to get that accurate by having people posting stuff over the internet.

we're basically talking about the theory of how to measure the car's acceleration at this point. if you really want accuracy, go to a 1/4 mile strip and post a scan of your slip. Nobody can even agree on which 30-70 or 50-80 or whatever to do. I already said 30-70 is pointless to me. I don't even hit peak power until 80-90mph or so.

so to turn this thread around, do whatever you can to get a good long pull, measure it as accurately as you can, post how you measured it, and it is what it is - just for fun.

[Sagaris]

As long as the key factors are mentioned (any modifications, transmission type, differential, tire size (if different from stock) then it should be fine. I compared my auto with chip against my manual with a diff and no chip. If i would have just said auto 325i vs manual 325i it would be very misleading. The details give substance as to how and why differences in performance are present. Id love to see some 30-70 times with M50 swaps, turbos, M42's etc.

[KennyT]

there's no way to get that accurate by having people posting stuff over the internet.

we're basically talking about the theory of how to measure the car's acceleration at this point. if you really want accuracy, go to a 1/4 mile strip and post a scan of your slip. Nobody can even agree on which 30-70 or 50-80 or whatever to do. I already said 30-70 is pointless to me. I don't even hit peak power until 80-90mph or so.

I believe the point of this is to compare various vehicles using a common start and finish, the on-ramp pull. It doesn't matter if your car doesn't hit peak power until 90mph, just means your gearing/powerband isn't useful for this metric.

If you are on stock tires, roll at 30 and nail it. Post the time and specs. If you are on different than stock, figure out your start and end points and roll from that.

This isn't a car review or a magazine article, +/- .25 second is close enough.

[nando]

or maybe it means that this metric isn't useful? :p

[kamotors]

I decided to do a 30-70 w/ my car with 225/50/15 and a 4.27diff, automatic trans., It did it in just about 5.5 seconds. I need a more precise way to time and I'll try it again. My accelerometer doesn't do 30-70 just 0-60 and 1/4 miles.

car has MAF and exhaust as upgrades.


problem is that it shifts twice to get to 70mph

[Sagaris]

I find it convenient to take video of the speedometer then time it when i watch the video so I can time it more accurately. 5.5 is pretty dang good esp. with 2 shifts, You should post up a vid to back it up though :P

[Wh33lhop]

it seems to be 4mph off with stock sized tires no matter how fast I'm going. My theory is the error is in the dial face, the actual speed read from the diff and calculated inside the cluster doesn't curve away from the true speed like many people believe. At least that's what I'm seeing by logging the VSS signal directly.

using gear/RPM/tire diameter should be just as accurate as a GPS, providing that's inputed correctly. It's not rocket science. :p

It's been my experience that it's pretty linear or a second order relationship amongst most (older) cars. My current one has 195/60/14s for as long as I can remember (which obviously gives a linear error) so I can't really compare directly, but my last car was pretty linear having used a few different GPS to test the speedo. My current speed is only 1 or 2 mph shy of the indicated speed from 20-40mph or so though, have you removed your needles to paint them or anything?

problem is that it shifts twice to get to 70mph

Autos don't get to bitch about shifts. :p You have continuous torque delivery.

[Hey_You]

I haven't timed it, but I wouldn't doubt if it was 6.32...minutes! My poor m10 has to work so hard! Thinking m30 swap in the future to help move things a little better

[nando]

It's been my experience that it's pretty linear or a second order relationship amongst most (older) cars. My current one has 195/60/14s for as long as I can remember (which obviously gives a linear error) so I can't really compare directly, but my last car was pretty linear having used a few different GPS to test the speedo. My current speed is only 1 or 2 mph shy of the indicated speed from 20-40mph or so though, have you removed your needles to paint them or anything?



Autos don't get to bitch about shifts. :p You have continuous torque delivery.

no I haven't touched the needles. with 235/50-15's it's dead on though, but then the OBC reads low.

most cars of the E30's vintage still have cable driven speedos out of the transmission. we should be thankful we aren't so unlucky. ;)

[gearheadE30]

I did some tuning pulls with the m42, and 3k to 6k revs in third gear takes between 7.2 and 7.4 seconds. That's basically 40 mph to 80 mph, according to the site e30nub posted

[nando]

if you know what gear you were in and what your tire size is it's not hard to figure out.

[e30nub]

Go to "Rev Calculator"

http://members.dodo.com.au/~wawawa/e30index.htm

[Sagaris]

If you are running stock tire size( 195/65-14 or equivalent circumference), a 4.10 diff and stock Getrag 260/5 ratios then 3k-6k is 40 to 79 mph

Edit: Nevermind, 318is is a G240

[gearheadE30]

Post updated based on that internet calculator