Did you solve your boost breakup issue?
93 325is: obd2 M52, 22rpd tuned, 6266, RSI manifold, 555whp on 18psi
Im not sure. I went over the car checking connections and all but i have not taken it out since that video was shot.
Bump
Hows the car holding up so far?
Car is running real strong. No oil or water leaks! No compression issues. I went through the entire harness and cleaned up all of the ground contacts, then increased the timing and fueling so the car is dumping alot of fuel. But the breakup issue is gone. Once i retune, I will be able to narrow that down to know if it is a fueling issue or not. The car is running real strong tho.
How much boost are you running? Stock internals (I forgot)?
lughed, did you make your exhaust manifold head flanges, cut them off of some stock manis, or did you find a place to buy them/have them made?
How's everything going? Good I hope!
I cut off the stock flanges then cut out what was left of the inner core
Geeez, I didnt realize I havent updated this in two years. Anyway, the car is still dishing out that punishment. For those that inquired, the issue I had, had been resolved since my last post in this thread. It turned out to be a few bumb coils in the set that I bought when the car was first built. I ended up buying a new set rather than filter out the bad ones.
I have been driving the car alot, almost every weekend. I noticed my chassy has flexed out of shape and it left about a quarter inch gap in my door despite having a roll bar. So the latest upgrade being done to the car is an under carriage cradle being built to be light weight and eliminate flex while keeping a low center of gravity.
I came across some old vids I have. Here is a light 4-6 gear pull I did last summer. Yes the car is still alive and kicking.
https://youtu.be/ptSpC4MvE1Q
Have loved this project since I followed the thread years back. My only qualm with this is the 3.73 gears, those are really short for a 6 speed. This car would be so much more fun with a 3.25 or a 2.93!
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I love the 3.73. At 65 mph it cruise at 2750 ish which is actually better than my stock ti which would be at 3000 rpm. The problem is it a larger engine and a small fuel tank. I have a 3.25 at home and contemplated putting it in but ill save it as a backup. I do believe the 3.25 would be a better comprise between economy and performance. The 3.73 is raw performance with just enough economy to live with being I rarely drove the car. The small fuel tank has me filling up alot but I never calculated how long I can go on a tank in one drive. Imo, the 3.73 is definately the funner gear ratio.
I personally don't agree with there being a compromise. You have a light car, with a much bigger motor, making plenty of torque NA and a turbo. In all my swap cars, including a 500whp s50 swapped e30, I preferred long gears that make use of the powerband and also help with traction. Longer gears on a turbo car will load the turbo and get it to spool a little earlier. Also turbo cars run through the gear quicker when in boost.
Roughly your current gearing top speed in each gear should be as follows with a 225/45/17 tire:
1st: 33
2nd: 55
3rd: 83
4th: 113
5th: 139
6th: 168
With a 3.25 you would get this:
1st: 38
2nd: 64
3rd: 96
4th: 130
5th: 160
6th: 193
You would have a much more usable 1st-4th gear, with less traction issues and much less shifting. A long 2nd and 3rd are always great in street cars with wide powerbands. Just my 2 cents.
Last edited by e30polak; 06-16-2017 at 04:43 PM.
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Helping with traction and loading the turbo I absolutely agree with but any gearing that goes above ~160 is useless to me. I would only go with lower gearing for the cruising rpm
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And as a note I have 285/30/19
M62 turbo E30 is still ticking. I worked over the winter to recover what seemed like some lost power from really safe tuning. I didnt touch the timing but i eventually did raise the spark dwell back up after being afraid of this from the bad coil mishap that i had.
I dialed in the accel enrichment and raised my rev limit up to 6800 after going down to 6500 from 7200. Only running 7.5 lbs i leaned out my peak boost afr from 11.6 to 12.1 ish.
I havent run the car since the weather broke but here is a run with a straight piped Lamb. Lp560. late last summer before the tuning changes were made. I spun 3rd, part throttle in 4th and and most of 5th and i banged off the limit on my slow shifts forgeting i had it down to 6500 rpm. Thought i would post a m62 turbo that wasnt drifting or doing burnouts..... Enjoy!
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https://youtu.be/qdNn2cXfNcY
It just seems to be one of the BMW combos that is never seen in a straight line.
Its at 3.2 now and pulling off from a dead cold start at below 30° is not longer a problem. I would have had to let the car warm up for awhile before i could drive off without heavy stumbling. This is without an iac and 42 lb injectors. It took me awhile to turn the dwell back up even though this stumbling was not a problem in the early tuning stages when my dwell was 3.5.
Ayyyy. What's up folks? The ole e30 is still turning. I don't drive it much since the pandemic (hope everyone is doing well) but i do take it out once in a while to stretch its legs and get the juices flowing.
Before the shut down i had a run with a c7 z06. It was mid 80's and sunny that day. I was in 4th each time it pressed and i gave chase. I drove through a spin and was still on its a** but then upshifted and blew the tires off. The z06 then pulled away. One run the z06 was behind and gave chase so i was able to modulate the power needed a little better. I eased down on 4th and into fifth. I believe the top of fifth i was able floor it after some easy foot control. My lil ole e30 was screamin through the revs but that z06 stayed on my a**. At that speed, revs, and wide open throttle the car felt flat like it had run out of breath.
So lately i been thinking about doing a rear end swap. I remembered the post in this thread by e30polak (knod my head to you sir) advising me to go to a taller gear. At the time i was about fun, rowing gears and such. This run with the z06 was the first time i had to go balls out to a point where i couldnt afford to pull back. Being traction limited and running out of breath up top for what i was up against left me sad and wondering till this day... what if i had taller gears?
I have had a 3.25 and 2.93 diff sitting here since before the build of this car. I also have a 3.46 rear end but it doesn't seem to be an open diff. While i do still feel like the 3.73 is fun to drive, my frame of mind has been toggling from fun to max performance, comfort, and economy. Strange enough that a taller rear would give me all three. I would like to start taking the car on longer trips to attend some events without some of the obvious downsides of a shorter gear. Besides, i hate the feeling of falling off on the top end.
The car as it sits still has the 3.73. It rides on 285-30-19 (about 25.5") and weighs ~2500 lbs maybe. I still dont have dyno numbers but for what its worth i have spun 6 gear at 30 mph and also did so over 100 mph, in summer heat.
Im not really into dig racing. Im more of a role race and twisties guy. What rear end do you guys and/or gals feel would be the best for me? The 3.25 or 2.93?
Go with the 2.93. Turbos love tall gears and LOAD. You also should have PLENTY of low end torque to pull that on the highway and bump your gas mileage way up.
2.93 IMO is the perfect diff for a turbo S/M5x powered car with a 1:1 trans ratio box
Thank you guys for your insight. Could guys give any insight as to the reason to go 2.93 over the 3.25? I know the loading the turbo and mileage and such. I dont know specifics to these ratios. I guess what im asking is at what point does tall gears become detrimental? Im not second guessing you guys opinion. I would just like to know about your experiences.
It's different points on a continuum. There is no "breakover point". And really, the stopwatch or timing lights tell you when a change slows you down.
You're soooooo far down the path toward "overgeared" that getting back to something sensible seems like a huge step. You have sooooo much axle torque and so little weight over your drive wheels that you could drop the gear WAY down, spin much less and have a much faster car. FFS, read your own story... you talk about spinning tires through 4th and into 5th.
Also, if you slow down the rate at which RPM changes at a given vehicle speed, you can put peak power to work for a longer period of time during a roll.
Also, the BMW community tends to have crazy ideas about gearing. I guess there are enough toy cars here that guys don't mind their tachs sitting at 4k driving down the highway because they drive on the highway for extended periods of time once a year.
Last edited by DarkSideofWill; 08-11-2021 at 05:50 PM.
Like i said in my story, i know the car is over geared and i know the benefits of going taller. The car is fun as hell driving through spins, working the throttle and rowing gears and not to mention the instant hit.
My dilemma is i never drove a 2.93 rear end car. Im not doubting you guys but its kind of vague to simply say a 2.93 is perfect for turbo m50 based car or turbos love load. Believe me, im leaning towards the 2.93 simply because you guys recommended it. I agree there is no breaking point but im sure there is a point where gears can have the car lugging around. The same way i am at the point of over gearing now. I wasnt sure if the 2.93 is near that point compared to the 3.25 and I dont have time to be testing rear ends which is why im here typing.
As far as the top end pull im not really sure if its a gearing thing or if power falls off. Being that i dont have a dyno or even a datalog at that level, i would think i still have enough to sustain a good pull so i contributed the feeling of not pulling up top to the gears. I dont know if i was holding that vette off or if it was just sitting there following. If not the former i think my top end is pretty good as is.
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