My e34 swap, mods, experiences and advice

[Brandon J]

Hello everyone. I thought I would share some things about my experience and my e34.

The 1993 525i 5spd:
It started life as a stock M50tu.
Engine: added S50 cams, S52 springs and retainers, 540MAF, larger injectors, 3 custom chips, custom intake and heatshield
Drivetrain: lightweight aluminum (rattling) flywheel, 3.46 40%LS Blanton Diff, short shift kit
Suspension: Green RD springs and custom shocks. Changed those out for Sachs kit. Added Green RD swaybars. Then added Dinan fixed camber plates. After the suspension was completely broken-in, ~a year, I trimmed the stock bumpstops a little at a time until it was right as far as how low I wanted the car to go on the backside of a bump. The stock bumpstops are softer so I could get a more progressive "squish" rather than a harsher one from harder foam.

Extras: I then added M5 brakes, rear headrests b/c the passengers were hurting their necks, and hardwired a V1. I had 17in 7spoke e39 540i BBS wheels and they were the strongest wheels I have used. I had 16in R-compound on e31 wheels and snow tires on another set of e31 wheels.

One time, I was running the streets of Chicago with my R-compunds. I met an M-coupe at a light. I revved my puppy to ~3000rpm and dropped it. I felt the shift knob twist with the drivetrain and without tire squeal I lunged forward. 1-2-3rd gear and he M-coupe could not get passed the front door. I had to work that engine/drivetrain combo a lot to get it to perform and the rattling was annoying.

I overreved the engine one day and.....

I was lucky as I wanted to drop in an S50 or S52. For the same price of an S50 and tranny combo, I had pickings from a rolled over e34 M5.

Now S38B36:
Engine: cam gears to move torque lower in the rpm, 4 different chips I change around,
Drivetrain: I had the M5 driveshaft custom made to mate to my small diff. Now, I don't have to change rear subframes and I have a bigger litter to chose from if I ever need a diff. It can handle the power. I am running 3.91LS, short shift kit.
Suspension is the same. S38 added ~65-70lbs to the car overall.


Okay, so look how I added the suspension in stages and left the door open to add upgrades and even account for the extra weight of the M5 running gear. I would go matched spring/shock combo, then swaybars, then fixed camber plates. In that order exactly. We have long wheelbases and the camber plates make a difference in balancing the car out. Turns are actually more controlled when going over bumps. The little bit of extra height from the plates help accomodate for the S38 extra weight.

I then added staggered T-stars with 245/45-17 and 255/40-17 rear Pilot sports. Why 245/45-17 front? Well, balancing the ride, braking, and suspension, the slightly more shoulder and width rubber cushions small bumps, small imperfections on straights and turns, has more rubber contact, and the larger diameter helps move braking to the rear with the extra 255 rubber. It brakes real smooth and balanced also because the front won't lock-up pre-eminently. I have over 25k of very hard driving miles on the tires with the horrible potholes of chicago. I bet I can go another 5k miles. The front outer shoulder wear is so common on the 5-series and I countered that with camber plates. The front of my tires are worn evenly from driving because the tire is flatter during the motion that wears it out the fastest, the turns. Because of these choices, the tires now balance with the suspension and brakes.

So, overall, I have a very forgiving, sticky, good travel, balanced, keep the tire contact on the road suspension. I can dance the car easily just like Sabine. Really. I am not that good on the track, the car is. I can push the front or break the rear in a very controlled manner while driving over 60mph on a turn. Predictable, controlled, safe. My Sachs kit has over 50k miles on it.

Recommendations:
Think balance and expandability. I did the mods, but recommend to just save and buy better. More dependable, more power, smoother, and less time tinkering. I have been told I have the best combo suspension by every e34 owner who rides in it. It is tuned as a super street car, not a track car. I drove it during the winter, on horrible streets, over 150mph, as a daily driver, on the track, autocrossing, with summer/winter/R-compound/all season tires, 15in, 16in, 17in wheels, etc. If you do this suspension combo, you won't go back.

Make good choices and you will save money overall. Good tires - go Michelin or equivalent, good matched shocks/springs, matched sway bars with adjustment for balancing, good camber plates, good M5 thrust bushings. Save money by doing the work yourself.

Take what ever info you want. Ignore what ever info you don't want. I just hope this helps those of you who want it. I might have more info that I am not willing to share and I may have more mods I am not willing to share about...especially when it comes to making power with the S38. Okay, tired fingers...

Enjoy your e34 to its fullest potential!

Mine is the first white one: (thanks to snopro67 for the pic)

[BigKriss]

nice write up!

[Denton]

Nice!

The Sachs kit, is that RD springs and Sachs shocks? Also, what brand are your bumpstops? Did you do 3mm spring pads?

Thanks,
Denton

[repenttokyo]

thanks brandon - this is kind of what I was asking you in the other thread. I have been trying to decide between and S52 and an S38. I know that the S38 is going to be more expensive in the long run, but I also feel that it is going to be more satisfying. Will the S38 mate with the M50 5 speed transmission? Does anything need to be moved in the engine bay?

I have done a search several times, but I can't find any threads specifically about this swap.

[Jon K]

I very badly want to do an S38 swap also but for other reasons. Brandon I want to race your car! Battle of the freaked out 525i

[Brandon J]

THe only reason I was able to do the S38 swap is because I was at the right time at the right place. If the M5 parts wre not available, then I would have gotten the S52. Now if you have an M50, pre build date Aug/92, then doing an S50 or S52 swap needs more parts. But if you do have an M50, then the manual tranny can handle the power. Same manual tranny as the M3.

If you have a M50tu, then the swap is easier. You simply swap the necessary OBDI parts from your current engine over to the S52. It will bolt on to the tranny and the tranny can handle the power. You just can't add a ton more torque. You can even use your own computer and simply purchase an OBDI performance chip for the M3. I think they also make chips for OBDI conversion S52s.

So, make sure the suspension, brakes, an tires are up to the task before adding a much bigger power jump. Then look for an S52 and it really is as basic as it sounds. Swap the long blocks and the ancilliaries. When the block is out. you can do an M3 clutch and flywheel conversion. I suggest an M3 one because there is already more surface area and clamping force built in. I have driven sport clutches and they do wear out your left leg from all that foot pressure they demand. The M3 will be a little firmer, but not nearly as bad as say a sport clutch for the smaller diameter 525 clutch. Again, starting with better parts that were designed at the factory offers reliability and ease. I think an M3 flywheel and clutch conversion is cheaper than using a 525 aport clutch too.

I don't understand why more people are not doing the S50/S52 swap. Nowadays, you can even find the longblock engines for the price of a pair of camshafts. For adding power, using the extra displacement of the S50/S52 is a great base to start with.

Good Luck!

thanks brandon - this is kind of what I was asking you in the other thread. I have been trying to decide between and S52 and an S38. I know that the S38 is going to be more expensive in the long run, but I also feel that it is going to be more satisfying. Will the S38 mate with the M50 5 speed transmission? Does anything need to be moved in the engine bay?

I have done a search several times, but I can't find any threads specifically about this swap.

[bimmerd00d]

VERY nice writeup. Rarely do we find someone as knowledgeable as you that is willing to post something like this. No speculation, no drama, no armchair mechanic here. This is what we need to see more of! I've got an E34 shell here, now I just need something to throw in it.

EDIT: regarding the M50/M50tu trannies, '93 introduced a weaker transmission i believe, i went through 2 of them somehow. Maybe it was just me shifting like the huge american bastard that I am. I came from a bigass hefty Corvette to the '93 525i.

[Brandon J]

Took out the RD springs with custom shocks.

I installed the Sachs matched spring/shock combo. Ironically, I still use the stock spring pads and stock bumpstops. All original since build date 9/92.

Nice!

The Sachs kit, is that RD springs and Sachs shocks? Also, what brand are your bumpstops? Did you do 3mm spring pads?

Thanks,
Denton

[repenttokyo]

thanks brandon, that's really a lot of help. If I have any specific questions, would I be able to send you a PM?

[bimmerd00d]

thanks brandon, that's really a lot of help. If I have any specific questions, would I be able to send you a PM?

why not make a post so everyone can benefit from it?