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New best 1/4 mile time- 13.10 at 108

Discussion pertaining to positive pressure E28s.
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turbodan
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Joined: Jan 09, 2007 10:19 PM

New best 1/4 mile time- 13.10 at 108

Post by turbodan »

Thats the best I could eek out tonight. My best trap was 109, but I could not get a 60' below 2.2. It was either wheel hop or a bog. The best ET slip reads like this:

60'- 2.216
1/8 mile- 8.557
1/8 mph- 91.428
ET- 13.105
Trap-108.388

Best trap:

60'- 2.31
1/8 mile- 8.730
1/8 mph- 91.742
ET- 13.263
Trap-109.070

The subframe mounts were gone before the first run. They've been gone for at least a week. I might do them this weekend. I hope those and some new dogbones make it a little easier to launch. I think thats what was keeping the car out of the 12's. It needs taller gearing too. A 2.79 would be good. It feels too strung out in the last few seconds of third gear.
Kyle in NO
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Post by Kyle in NO »

Sonofabitch...my car sucks....beat by a M20!

Excellent work Dan!
Mark 88/M5 Houston
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Post by Mark 88/M5 Houston »

New best 1/4 mile time- 13.10 at 108
Great time and speed for an M20t powered E28 Dan.
Sonofabitch...my car sucks....beat by a M20!
You haven't run in S2 trim yet. ;)
skip535i
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Location: Lynchburg, VA

Re: New best 1/4 mile time- 13.10 at 108

Post by skip535i »

turbodan wrote:It needs taller gearing too. A 2.79 would be good. It feels too strung out in the last few seconds of third gear.
First of all...

AMAZING TIMES!! That is VERY impressive for ANY car, not just a 20 yo M20 car. VERY nice.

I think you need to rethink your statement above. Your 60' time is by far the most critical thing about a quarter mile time. If you get a 2.79 diff your car is going to take MUCH longer to spool up in first gear, therefore hurting your 60' time more than helping the rest of your run.

Good luck getting new subframe bushings, I need to do mine but I don't know how ;)
turbodan
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Post by turbodan »

I dont think the taller gearing would hurt. The 2871 spools up instantly. As soon as I load the drivetrain its making boost. I dont know if it would be an improvement off the line, but I would like to be in a meatier part of the powerband for the last 1/8 mile. I might even be hitting the limiter at 6800 before I go through the lights. Its too close to tell. If the car gets any faster, I'm going to need taller gearing to hold third gear all the way.

The first few runs, before the car got hot, were spinning through first and second. The car hooked up in third gear. I know its going to spin through first, but I'd like to have some traction in second gear.
skip535i
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Post by skip535i »

turbodan wrote:The first few runs, before the car got hot, were spinning through first and second. The car hooked up in third gear. I know its going to spin through first, but I'd like to have some traction in second gear.
That has more to do with your driving than your differential gearing.

Stay off the throttle a bit and let your tires grab...spinning in 2nd isn't good.

WRT your turbo, if it spools as fast as you say it does then you should be good to go with more gearing. I have a 2.93 if you decide you need one.
T_C_D
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Post by T_C_D »

[quote="skip535i]
That has more to do with your driving than your differential gearing.

Stay off the throttle a bit and let your tires grab...spinning in 2nd isn't good.

WRT your turbo, if it spools as fast as you say it does then you should be good to go with more gearing. I have a 2.93 if you decide you need one.[/quote]

Skip,

Driving a 300rwhp turbo car is quite a bit different that driving a 160rwhp m30. Wheel spin is inevitable until the car is equipped with a stickier tire.

Todd
Last edited by T_C_D on Sep 22, 2007 3:40 PM, edited 1 time in total.
skip535i
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Post by skip535i »

T_C_D wrote:[quote="skip535i]
That has more to do with your driving than your differential gearing.

Stay off the throttle a bit and let your tires grab...spinning in 2nd isn't good.

WRT your turbo, if it spools as fast as you say it does then you should be good to go with more gearing. I have a 2.93 if you decide you need one.
Skip,

Driving a 300rwhp turbo car is quite a bit different that driving a 160rwhp m30. Wheel spin is inevitable until the car is equipped with a stickier tire.

Todd[/quote][/quote]

Which is exactly why I told him to ease off the throttle a bit.

Tire Spin = Bad

Better Tires = Good

Better Tires = Lots o' $$

A little Less throttle = cheaper than tires

A little less throttle = better times

Until he gets stickier tires he should back off the throttle slightly and reduce tire spin out of 1st gear.

You're right to say that 300 whp is different than 160 (I probably would dyno closer to 190hp but whatever) but still the same applies. Tire spin isn't good.
T_C_D
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Post by T_C_D »

Skip,

Have you driven a big HP car? Do you have any idea how difficult it is to modulate the throttle and reduce wheel spin?

Do you think that Dan doesn't know that spinning the tires is hurting his et?

Stating the obvious isn't helpful.

I have a $100 that says your car make less than 190rwhp SAE on a dynojet.

Todd
Kyle in NO
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Post by Kyle in NO »

Its OK Todd, I don't think Skip is trying to be hard on him. It is a big difference driving a turbo car, Especially a peaky small displacement one. As far as my car goes, if I would back off the throttle it would absolutely kill my times. Back off of WOT and turbo would lose RPM, boost would drop, and when you'd stab it again, they would likely break loose again...I just slip it a bit then stab it at the track. A 300hp NA engine needs to be driven differently than a 300hp turbo engine unfortunately.

Dan, what tire size are you running? In hot, dry, sticky weather, I break mine loose in first, and sometimes second with an S3.25 and 225/50R16s...In colder weather its much worse lol....are you still using 14" rubber?
turbodan
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Post by turbodan »

I'm on a set of 225/60 15 BFG G Force Sport tires. I think it might have something to do with the condition of my rear suspension, but all it was good for off the line was wheel hop or a bogged out launch. Throttling back enough to modulate traction will usually kill the boost, which comes back abruptly when you get back under power, breaking the tires loose again. I have 360 foot pounds of torque at the wheels at 4000 rpm, and a steep climb up to it from lower engine speeds. So I'm going to need a certain amount of wheelspin to get moving effectively. I can deal with just wheelspin, but it was particularly hop-happy on friday. That cant be right. The only way to get it back once they start hopping is to get off the gas entirely. Its either that or you can ride it out, but even then you're not going to have a super great run anyway.

I'll see how it does with new subframe bushings, new dogbones and a new guibo. If I can keep it from wheel hopping I should be alright. It'll do a 12 second 1/4 by the end of the year. Its so close with these shitty launches I dont doubt the car can do it.
M. Holtmeier
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Post by M. Holtmeier »

I started off with a new guibo, subframe bushings and dogbones, and smooth tire spin lasted about a week. I got my engine and trans out now and the motor mounts are gone, the guibo has a bunch of chords coming out of it and you can clearly see where the subframe had been slapping the body. If you go back with stock stuff, you'll never be able to drive hard.

Mine's all apart now, and before it goes back together I'm putting some serious thought on how to setup the suspension to take a little more abuse.
SilverBullet
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Post by SilverBullet »

Did u poly fill the subframe bushes?
I took my brother m535i out to the track once, motor is standard, was just for something to do.
With 235/45R17 i found the car would either hop or bog down. Came back from that nite with 2 completely split engine mounts and 2 split gearbox mounts...
M. Holtmeier
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Post by M. Holtmeier »

Wow, with a N/A engine? I haven't done it yet but I got a pound of 80 shore poly to fill the bushings. I think I'm going to make a set of steel disks and spacers to replace the guibo. Cage the motor mounts maybe. Something
Duke
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Post by Duke »

grsmonkey wrote: I'm putting some serious thought on how to setup the suspension to take a little more abuse.
Poly fill a M535i rear diff mount and sub frame mounts, poly fill a set of US engine mounts (fill the open triangle), install poly trans mounts and use a E34 M5 (3.8L) guibo with bolts. Drive shaft - good luck on that one.

http://www.mye28.com/viewtopic.php?t=28 ... ight=guibo

http://www.teamdfl.com/bmw/e28/bushings/diffmount.html
steel disks and spacers to replace the guibo
You will destroy your drive shaft in no time doing that. Most likely damage the transmission output shaft bearings too.
turbodan
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Post by turbodan »

I went with a set of Meyle heavy duty subframe bushings. They've got more than twice as much rubber in the bushing. They look pretty stout. If they fail again I'll find something better. I wouldnt mind doing them every few months. Not at all.

I saw a late Mustang Cobra up on a lift at the dyno when I went a few weeks ago. The guy had swapped out the stock IRS for some kind of live axle. I thought about how a guy would do that in an e28. Four links, maybe some springs and shocks. Like a coil over design with a live axle. It seemed like a very simple, effective solution.

I cant use a larger guibo without swapping out the output flange on the tranny, and then I'd need a new driveshaft too. I dont know what I'll do about that. Maybe just getting the wheel hop under control will make that little guy last a little longer.
Duke
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Post by Duke »

turbodan wrote: I cant use a larger guibo without swapping out the output flange on the tranny, and then I'd need a new driveshaft too. I dont know what I'll do about that. Maybe just getting the wheel hop under control will make that little guy last a little longer.
It is the same bolt pattern as the 535i guibo. The E34 M5 guibo is thicker not bigger in diameter.
M. Holtmeier
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Post by M. Holtmeier »

I remember reading your post on the m5 guibo, did it really hold up over the test of time? I also got the poly info from you Duke but never applied it. I guess it was a live and learn kinda thing.
You're probably right on the steel disks for a guibo. How far has anyone really got with driveshafts. I read about a single unit letting go, destroying a car and lots of u-joint failures. Has anyone ever replaced the guibo with another u-joint or cv off the trans output flange? I know a driveline shop that does all the work for our frame stretches, they do some pretty crazy work. All the heavy trucks that have multiple carrier bearings always have a u-joint right off the trans. Maybe BMW figured that since it was such a straight shot to the carrier, I simple guibo would be fine.
Duke
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Post by Duke »

grsmonkey wrote:I remember reading your post on the m5 guibo, did it really hold up over the test of time? How far has anyone really got with driveshafts.
Don't know, I sold the car shortly after installing it. Tony has reported that the drive shaft U-joints went bad again. It had an used OEM DS from Jim in SD in the car. Tony has plans for a modified two piece DS he is getting made for the car. He will hopefully have some details.

Ken H also has a hell of a modified two piece DS for Lucifer's Hammer, maybe he can chime in with how it was built.

HTH's
turbodan
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Post by turbodan »

Not mine. Its a smaller diameter, and the bolt holes are closer together. Its an e30 sized guibo, which fits my e30 tranny output flange. It sucks for me.
M. Holtmeier
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Post by M. Holtmeier »

Sorry man, didn't mean to jack the thread.

What about running the front section of an auto driveshaft? You can make a simple adapter to the trans. If the lengths were off, it would be cheap to have the yokes cut and welded.

I know I'm not putting mine back together until it's solid.
SilverBullet
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Post by SilverBullet »

Are e30 m3 guibo's any tougher?
turbodan
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Post by turbodan »

e30 M3's have a larger guibo than I do. They installed a stronger guibo on the gutless 2.3l M3 than they did on the 2.5i e30. So my 2.5i tranny and my 9/83-5/86 528e driveshaft only fit the 78mm sixed guibo. The 535 and e34 M5 3.8 both use 96mm spacing on the guibo bolt holes. Its the same pattern, just larger.

I dont think I'm out of luck yet though. One perk of working in a BMW parts department is being able to open up a drawer full of various guibos and eyeball things up. Sure enough, the e36 328i auto's used a 76mm guibo thats significantly stouter than the e30 guibo. The e30 guibo I recently destroyed is P/N 26-11-1-225-624. The 328i guibo is P/N 26-11-1-227-410. Its a good 4-5mm thicker between the flanges where its loaded on acceleration. The thin areas in between the main load bearing portions are 11mm thicker. The 328 guibo also does not have the little dimples molded into the face of the guibo. I'll take some pictures later if I can. Its a much stouter looking piece. Hopefully its stout enough, because its all I can just bolt in.
Jeremy
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Beamter
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Post by Jeremy »

Stiffer rear suspension (springs/shocks) will help eliminate wheel hop. The hop is destroying your rear rubber pieces, but the bad pieces are not necessarily the primary cause of the hop.

Jeremy
turbodan
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Post by turbodan »

I have a parts car with Bilstein sport suspension. I might be able to swap that out without much trouble.
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