Member
Hey guys, I've got a '95 M3 I'm bringing back to life. Currently in the process of doing all of the body work and taking care of any rust issues, then doing suspension upgrades afterwards. I'm in search of help with the tuning of the S50 engine. From what I've read on the forum, these engines can handle a lot more and are very de-tuned from the factory. My plan is to do an OEM rebuild on the engine (gaskets, bearings, seals, VANOS rebuild, maybe some machine work to deck the head, etc.), and I would like to tune it out as much as possible with a quality tune. If that means upgrading injectors or other things as well to accompany it, I'm fine with that. Not really looking to do upgraded cams or any serious engine internals. All advice and tips are much appreciated. Thanks.
Member
There really is minimal gains to be had with engine tuning until you start modifications to the heads (valves, camshaft, etc). Any OTS chip tune should be fine and cheap.
Member
^This.Originally Posted by olemiss540
With an OTS or custom tune (most of these are kinda rich from the factory), and an OBDII mid-pipe, you might get ~10 extra HP.
Balogne Cajones
Turner got like 20 and some torques with just switching to 91 octane and a tune. https://www.turnermotorsport.com/BMW...86-1995-models
Member
Owning an S50, I simply don't believe that one will see 19hp gain from an OTS tune (and 91 Oct) installed in a stock car.
Turner also says this tune provides a new rev limit of 7,000 rpm. That's a hint about the accuracy of their claims right there.
Member
I ran a pretty stock s50 for years in my racecar - GTS2 (restricted) and in ST4 (unrestricted). Unrestricted, on 91, with stock cams, stock OBD1 headers, stock head with upgraded springs and retainers, 3.5 MAF, 24lb injectors I made 237 rwhp 225 tq on a Dynojet with an off the shelf Turner chip. Did about the same with a TRM off the shelf chip. Later I put on some mystery 'custom' VAC chip that a friend had and I made a whole 3 HP more. The Turner/TRM/etc chips for those mods do work and are generally pretty safe. Totally stock, when the car was a streetcar and took much less abuse, it made 212 rwhp. For compliance, we dyno cars very often on different dynos, and my HP and TQ was always around the same unless there was something wrong, so 237-240 wasn't a fluke. Most important is that the bottom end is in decent shape, has good leakdown/compression numbers, and everything else is well maintained. That is probably the most you'll get without porting, cams, higher compression, and I would generally agree that it's not worth going down that road for multiple reasons. Cost increases and longevity decreases the farther you get from stock and you'll come to find that BMW engineers really did know what they were doing. I think the s50 is a great little motor and you should just take care of it and enjoy it.
Member
This is all great information, and very much appreciated from every user. Every cylinder has compression at around 180, but cylinder 5 varies between 150 and 160. I tested the compression multiple times both hot and cold too. Ultimately, I'd like to rebuild and refresh what needs to be for this engine then. I can do heavy collision/body work all day and suspension overhauls (which I'm doing on this car already with upgrades), but engine work is where I fall a bit short. I can do all of the labor because I have the tools and resources in my shop, but how do I know if main/rod bearings are no good no more, or piston rings, or valves, or springs, and so on. That is where I am stuck...
On a side note is anybody selling an OBD II midpipe?
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