Random Data Plots - M42 Engine Parameters Stock vs 2.1L Stroker

[Karolis]

Someone with a genuine M42 e30 can give me the distance from top of dipstick to maximum level please? Like in picture.

Thanks in advance!

[cncmastr]

This is a great thread, thanks for your efforts!


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[Victell]

Great thread. Enjoying reading your continued adventures with the M42.

[bmwman91]

I just finished setting up the next stage in my logging adventures. These will be used simultaneously with the wide-band O2 sensor system to get my tune dialed in. Some remote tuning is planned for the near future, and then some live dyno tuning to get things perfected later in December.

Yes, quad EGT probes is overkill, but given the work I have put in so far, I want to see how well balanced the cylinders are. Some things I have seen in the MAF signal suggest that certain cylinders are slightly starved at some RPM's. Now it's time to see.

For reference, the threads in the stock header are M8x1.0, and as long as the threaded portion of the fitting is 11mm or less it will not protrude into the runner. The ID of the runners is ~32mm, and I adjusted the probe tips to protrude ~12mm into the exhaust stream. M8x1.0 EGT probe fittings are reasonably common, and I am thankful that BMW put standard bungs in the stock manifold. They are a bit closer to the head than is usually recommended, but since I am not planning long-term use of these, it should be fine.

[Karolis]

Hello!

Could please someone tell me if it's possible to use M50 pistons and rods (135mm) on a m42 with m47 crank and what happens to the compression ratio without shaving the block and decking the pistons? Is it a good solution for having a strong top end and lower CR without boring the block and doing other "harder" operations?

[digger]

as well as the inlet length reduction, removing the horn makes the inlet a sharp edge and gives vena contracta that reduces the effective inlet area alot

[bmwman91]

Wow, 4whp from removing the little air guide horn? Was the loss at peak power, or in the mid-range somewhere? I wonder if the loss was due to air having to suddenly turn a sharp corner into the AFM, or if the horn was actually functioning as part of the intake resonance system and enhancing volumetric efficiency at some RPM. I am currently running an E34 M30 air box and MAF, with a 7" straight tube in front of the MAF as an air guide...maybe I should bring my stock air box to the dyno to do a comparison.

[ForcedFirebird]

Wow, so that is like 8% loss in the drivetrain for stock 325i cars. Not bad! I guess I will find out soon enough.

They are low on parasidic loss, for sure, but 8% is very hopeful. I have yet to do a Spec e30 style build on a totally stock car with all stock exhaust and all accy's functioning (result can sway based on age of cat/muffler). The power steering is worth about 3whp, stock fan showed less than 1whp (less than .5 even, IIRC), never tested an A/C clutch. Funny thing is that little horn in the stock air box showed a 4whp loss when removed - can only imagine what a cone filter would do to it, specially since it becomes "hot air intake". I would put the g260/3.73 final drive closer to 10-12% on a guesstimate.

[digger]

They are not the exact injectors that were used for the original tune (the chip was developed for the MM 2.1L engine design, not custom burned for this specific engine). I guess that there was some sort of issue with the 24# EV6 injectors that were originally selected (pintles getting stuck open) so MM had me order some 24# EV1 ones. There is more to an injector than the static flow rate, but it's what the option was at the time. The chip was not re-tuned for the different 24# injectors.

I don't have the exact specs for the centerlines. But, based on the timing map for the grind and assuming that the lobes are symmetric about the centerline, the intake CL is 117deg ATDC and the exhaust centerline is 120deg BTDC. The combined cam CL is then 152deg BTDC (92deg separation between intake and exhaust CL's).

If someone local could tune Motronic 1.7, I would have gotten on a dyno and had a custom tune made LONG ago. Sadly, nobody in the region works with it and going stand-alone isn't something I have time for now (or in the foreseeable future).

if inlet is 117 and exh 120 then its 118.5 centres. both those are far too wide for best allround performance. something close to 110 would likely work better subject to what emissions you have to meet.

my money is on 150-155whp if you dynojet it

[bmwman91]

Wow, so that is like 8% loss in the drivetrain for stock 325i cars. Not bad! I guess I will find out soon enough.

[ForcedFirebird]

Not 20% IMO. Fresh non-bored m20's were rated at 167, we typically see ~155 with cat/muffler and accy belts removed (stock engine), closer to 160 with .5mm over bore.

[bmwman91]

160whp is probably an absolute minimum I am hoping for. If the 205bhp figure is to believed, then 164whp would be the case with 20% drivetrain losses, and that seems a bit high since everything is fresh, I have a nice new Wavetrac diff and a very light flywheel. Any idea what the typical E30 drivetrain losses are?

[2mAn]

lol

Yeah I need a good detailing (again) before photos...construction in the area has covered my car in dirt, and parking outside of my garage because of some woodworking projects has it looking a bit faded.

Dyno action will be next month when SSSquid is in the area.

You need to buy that car you asked me about. M42 FTW.

I know how it is. I dont drive the E30 much because its not the daily anymore and so I wash it, drive it for a day then it gets parked for (usually) 2 weeks until I drive it again. Its always dirty when I take it out again. Too dusty where it gets parked.

Im really curious what yours puts down, 160whp or bust?

As far mine and the one I linked you, unless someone will fork over money for my M52 car than its not going to happen. If someone does, than thats at the top of the list.

[bmwman91]

lol

Yeah I need a good detailing (again) before photos...construction in the area has covered my car in dirt, and parking outside of my garage because of some woodworking projects has it looking a bit faded.

Dyno action will be next month when SSSquid is in the area.



You need to buy that car you asked me about. M42 FTW.

[2mAn]

Will you just put this on a dyno already?!?! Take some pictures while you're at it :razz: