My M42 Fuel Economy and Maintenance Logs

[bmwman91]

I finally got around to entering all of the scribbling from the notebook in my glove box onto my site. It has been over a year since the last update lol. Maybe I should spend the next 3-6 months putting all of the pictures and articles up on my site, rather than starting more real projects. That sounds more relaxing, and a LOT less expensive!

http://bmw.e30tuner.com/my318is_econlog.php

Fuel economy plot:


Gas price history in my area:


And the maintenance history. It now includes the new M42. I do need to add in some details about the sound system, though.

http://bmw.e30tuner.com/my318is_maintlog.php

[eur04lif3]

So your 2.1 is getting at best 24MPG? That's not bad at all IMO, keeping in mind that you gained 70HP.

[bmwman91]

Hopefully better than that. I was driving it pretty hard on the first few tanks, and mostly around town. I think I can probably hit 28+ on the highway if I behave.

[eur04lif3]

Hopefully better than that. I was driving it pretty hard on the first few tanks, and mostly around town. I think I can probably hit 28+ on the highway if I behave.

Then the build is very very appealing. Hope i'm not thread jacking here, and you don't have another thread regarding the 2.1 build.
But what made you decide to go with 2.1 NA vs. 1900 FI M42 Engine? Seems like the prices are relatively similar. (+$500 gets you 30-80 extra HP).

http://www.metricmechanic.com/product-prices/engines/m42-m44/

[bmwman91]

I wanted NA because I wanted maximum reliability. This damn car has made me tear into it waaaaay too many times in the last 3 years, primarily because of timing chain problems. A turbo would be fun, but it would hurt mileage and add a big, expensive part to the engine that requires maintenance and replacement on some interval. Truthfully, I am just a big fan of NA engines.

[Dj Buttchug]

what rear end ratio?

[bmwman91]

4.10 small case LSD

I am planning to convert to a 1999 318ti driveline next year. The G250 is a beefier, lighter tranny and the guys at MM recommend it. Apparently the tranny/dshaft/diff are a direct swap.

[Dj Buttchug]

wow thats damn good mileage for a 4.10. Did not know about the g250... gets me thinking my car needs one ha

[bmwman91]

Yeah, I need to double-confirm with MM about that. I don't know if it can use the same shifter linkage. According to them, the 318ti was a frankencar built from warehouses full of left over E30 production parts. It's basically an E30 chassis with an E36 body & interior.

[gearheadE30]

The G250 is not an overdrive trans, iirc. Something to check on before you dive in.

Also, why do you say a turbo would hurt mileage? I get typically between 30 and 32 mpg on highway trips, cruising at 75 mph, 3.73 rear end. Around town, I have yet to see below 26. Before the turbo, stock EMS was around 25 mpg city, 27 highway with a 4.10, and about the same city, consistently about 29 mpg highway NA with MS2e.

Though to be honest, I do like natural aspiration better as well, if I could have done it at a similar cost.

[bmwman91]

I usually assume that turbo engines have lower compression, which generally hurts fuel economy. I know that some folks run turbos with the stock compression, so I can see the mileage remaining about the same on the highway.

Yeah, the G250 is geared different. I think that I was going to hunt down the E36 3.91 LSD or something like that which would make the final ratio in 5th gear about the same as stock.

[Boltspeedman]

OP could you shine some light on your 2.1 build, @ 290k my m42 might be getting close to a total rebuild. I apologies for the rabbit trail question.

[irish44j]

I usually assume that turbo engines have lower compression, which generally hurts fuel economy. I know that some folks run turbos with the stock compression, so I can see the mileage remaining about the same on the highway.

Yeah, the G250 is geared different. I think that I was going to hunt down the E36 3.91 LSD or something like that which would make the final ratio in 5th gear about the same as stock.

you could hunt down an e30 3.91....which is what is in my car (stock diff, as I have an early M10 car with an M42 about to go it). Granted, it's a small case so maybe you don't want that. But the gearing is there.

[bmwman91]

OP could you shine some light on your 2.1 build, @ 290k my m42 might be getting close to a total rebuild. I apologies for the rabbit trail question.

It is a Metric Mechanic Rally 2100 M42 with every single option that they offer. I could type a big long post about it, but their brochure is far more interesting!

http://www.metricmechanic.com/pdf/M42-Engine-Booklet.pdf

NOT inexpensive though. It does not win any dollars-per-horsepower awards lol. You gotta really, REALLY love the M42 because you could drop in an S52 and tune the shit out of it, and still have enough money left for a spare E30 for the price of this. The prices in the booklet are...outdated.

[Boltspeedman]

It is a Metric Mechanic Rally 2100 M42 with every single option that they offer. I could type a big long post about it, but their brochure is far more interesting!

http://www.metricmechanic.com/pdf/M42-Engine-Booklet.pdf

NOT inexpensive though. It does not win any dollars-per-horsepower awards lol. You gotta really, REALLY love the M42 because you could drop in an S52 and tune the shit out of it, and still have enough money left for a spare E30 for the price of this. The prices in the booklet are...outdated.

Sorry didn't realize it was an mm engine. Thanks though. It isn't a cheap option, however my m42 is growing on me. I've owned an s52 M3 and it's a great engine. However I like my 318is with a 4 cyl, maybe some day.. maybe an s14.