My e34 swap, mods, experiences and advice

[repenttokyo]

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

i just don't want to burden brandon any more than necessary.

[Brandon J]

I do agree. First everyone can benefit, plus others can chime in on real world relevant experience. We can all collaborate the best practices for maintaining and modifying the e34.

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

[Denton]

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.

Thank you!

So when you say that you would go with "matched springs/shocks, swaybars, and then camber plates" in that order, are you suggesting not to do it all at once?

Why wouldn't one do it all at once, or at least the camber plates with the springs/shocks.

Thanks,
Denton

[Brandon J]

You can definitely do it all at once. If people had to do it in stages because of cost, then follow the stage order I suggested.

The camber plates enhance the spring/shock and swaybar combo. The swaybar combo enhance the spring/shock combo. So each latter stage enhances the previous stage. If you do the plates before the swaybars, then it will try to make up work the sways have to do. It will not have the balance.

Thank you!

So when you say that you would go with "matched springs/shocks, swaybars, and then camber plates" in that order, are you suggesting not to do it all at once?

Why wouldn't one do it all at once, or at least the camber plates with the springs/shocks.

Thanks,
Denton

[repenttokyo]

A specific question: One of the things that keeps me from swapping in an S52 is that it's about 3-4k for a 50 hp increase (over my chipped M50). I am somewhat surprised that you would have gone for an S52 had you not been lucky enough to find a good priced S38 - the power difference seems quite large. Am I off base here?

[Sam-Son]

Thanks I've always been wondering about that car. Nice work. I'm thinking about an engine conversion but like repent I'm undecided between the S50 ofr the S38. Theres plenty of power to be made out of the S50 and isnt the S50 alittle more reliable and better on gas mileage?

[Brandon J]

Good question. These M50 based engines have a good 5k usable rpms, meaning you can use between 2,000-7,000rpm on the road. Now peak HP might be around 6800rpm, but that is peak. The gains are with the torque and horsepower within that 5,000 rpm range. The S52 has more torque and HP in the whole range so you can accelerate faster in all rpms and all speeds and the engine spins faster. So, 0-60 is faster, 30-60, 50-70 and so forth.

Here is an example that I hope is clear: Say the e34 needs 200hp and 190lb/ft or torque to pass a car on the highway. Well, that power may lie around 6500rpm in the smaller M50tu at wide open throttle whereas the same power may lie around 3000rpm in the S52 at wide open throttle. That is the difference of needing to shift twice...down then up with the M50tu and not shifting at all in the S52. THis makes a huge difference. Remember I did the mods to the M50tu and know how the power band is.

50hp is a lot! But remember to add all the extra torque, the flatter torque curve, how much more power you get if a chip is added to the S52 OBDI, and so forth. Realistically, the same rule applies as far as engine size with displacement because these 2 engines are based off of the same base.

Engines are dynamic, not static. So only looking at the peak number does not reveal the actual power delivery. We have to look at HP and torque in all rpms, in 25% throttle, 40% throttle, 60% throttle, etc. Also, any gains that an M50tu sees will only be bigger with the extra displacement and the hotter camshafts of the M3 engines.

A stock M50tu with a performance chip achieves around 211 Peak HP. An S52 OBDI conversion with performance chip can reach closer to 270. Then add a 540MAF and you have even more power. And that's only peak power. Torque is even better in all rpms and throttle. Since I started with only a performance chip in my old M50tu I am familiar with the power delivery, think about how the power boost felt if you added a chip. Now times that by 5-10. Remember the power delivery is much much better at peak and throught the rev range and throttle positions.

Lastly, since people were asking, you canNOT mate an S38 to a 525i tranny. I had a donor M5 and used its tranny. You might be able to mate it with the 535i one, but the gearing is different and the M5 tranny is better optimized to balance with the S38 power delivery.

A specific question: One of the things that keeps me from swapping in an S52 is that it's about 3-4k for a 50 hp increase (over my chipped M50). I am somewhat surprised that you would have gone for an S52 had you not been lucky enough to find a good priced S38 - the power difference seems quite large. Am I off base here?

[Sam-Son]

Good question. These M50 based engines have a good 5k usable rpms, meaning you can use between 2,000-7,000rpm on the road. Now peak HP might be around 6800rpm, but that is peak. The gains are with the torque and horsepower within that 5,000 rpm range. The S52 has more torque and HP in the whole range so you can accelerate faster in all rpms and all speeds and the engine spins faster. So, 0-60 is faster, 30-60, 50-70 and so forth.

Here is an example that I hope is clear: Say the e34 needs 200hp and 190lb/ft or torque to pass a car on the highway. Well, that power may lie around 6500rpm in the smaller M50tu at wide open throttle whereas the same power may lie around 3000rpm in the S52 at wide open throttle. That is the difference of needing to shift twice...down then up with the M50tu and not shifting at all in the S52. THis makes a huge difference. Remember I did the mods to the M50tu and know how the power band is.

50hp is a lot! But remember to add all the extra torque, the flatter torque curve, how much more power you get if a chip is added to the S52 OBDI, and so forth. Realistically, the same rule applies as far as engine size with displacement because these 2 engines are based off of the same base.

Engines are dynamic, not static. So only looking at the peak number does not reveal the actual power delivery. We have to look at HP and torque in all rpms, in 25% throttle, 40% throttle, 60% throttle, etc. Also, any gains that an M50tu sees will only be bigger with the extra displacement and the hotter camshafts of the M3 engines.

A stock M50tu with a performance chip achieves around 211 Peak HP. An S52 OBDI conversion with performance chip can reach closer to 270. Then add a 540MAF and you have even more power. And that's only peak power. Torque is even better in all rpms and throttle. Since I started with only a performance chip in my old M50tu I am familiar with the power delivery, think about how the power boost felt if you added a chip. Now times that by 5-10. Remember the power delivery is much much better at peak and throught the rev range and throttle positions.

Lastly, since people were asking, you canNOT mate an S38 to a 525i tranny. I had a donor M5 and used its tranny. You might be able to mate it with the 535i one, but the gearing is different and the M5 tranny is better optimized to balance with the S38 power delivery.

That's really alot of very helpful info. Now another question which seems kinda stupid but which do you think is the better engine? isn't the S52 abit more sophisticated?

[BigKriss]

For a daily driver car, I wouldn't go overboard on the suspension mods though. My setup is too stiff for my liking. I would change the springs to stock or m-tech, nothing aftermarket for the street. I wanted a good handling car, but the tradeoff for bumps is too much for my liking. Of course all this talk is subjective.

[repenttokyo]

Thanks Brandon, I didn't know anything about the details of the S52 powerband, and that makes a lot of sense. I really appreciate the information, I am glad you took the time to post.