Mike Miller, the BMW technical editor for a number of publications including Roundel, Bimmer, and European Car, has graciously provided his summary of E30 M42 performance mods. Although he declined to take part in our ongoing Q+A feature for, uh, scheduling reasons, he is a noted 318is 'alumni' (he drove one for a long time).
take a look, and discuss... note, this was compiled in 2003.
To reply to mike with a specfic issue, try contacting him via:
European Car Magazine WebsiteRoundel Magazine (bmwcca)
Bimmer Magazinethanks again to mike!
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E30 318is Performance ModificationsThe E30 318is, produced in 1990 and 1991 as a 1991 model year car, is a great deal more like the E30 M3 than the 325is. At a svelt 2,602 lbs, it is the lightest "modern" BMW by a substantial margin. And while it's M42 1.8-liter DOHC engine is clearly underpowered with a scant 138 hp @ 6,000 rpm and 129 lb-ft torque @ 4,500 rpm, it will rev up like a prom date on Stoli, easily provide trouble-free six-digit mileage, and get over 30 mpg in the process. The Getrag 240 5-speed overdrive gearbox and small-case 4.10 differential are no-brainers given the occasional synthetic oil change. Even driveshaft parts last longer on the 318is, due to the relatively low torque.
However, the 318is has two areas of deficiency -- low power and the need for suspension improvement.
Engine power can be improved noticeably with the addition of a good chip. High-octane gasoline is required even with the stock chip, owing to the 10.5:1 compression ratio as well as this engines lack of knock sensors. The chip gives the motor a new rev limit of 7,000 rpm, which you probably won't use except on the racetrack. Don't miss a shift, either, because according to Pete McHenry at Precision Performance in Winston-Salem, the vibration damper on the front of an M42 engine will disintegrate at precisely 7,200 rpm.
A high performance chip bumps ignition timing so that high-octane gasoline will become even more critical, and we’re talking 92 to 94 octane – the higher the better. The lack of knock sensors means that some M42s, if they have carbon buildup on the tops of the pistons, may experience detonation with a chip. However, you can get rid of carbon buildup on the tops of the pistons through aggressive use of a good fuel system additive such as Red Line SI-1, BG44K, Chevron Techron, or BMW Gasoline Additive. My regimen for this job is one full bottle of Red Line SI-1 before a full tank of fuel, and 1 ounce of the same product in ever tank full after that -- forever. US gasoline additive packages suck, and when detergency is of paramount importance, such as in a car with 10.5:1 compression, no knock sensors, and aggressive ignition timing, we need to mix our own gasoline additive package -- that is the simple harsh reality.
No, you can't add knock sensors to an old M42. You have to pony up for high-octane gasoline, and, with a chip, mix your own additive package. On the bright side, the 318is doesn't use much fuel. There is no need to do anything with the ignition system, except perhaps a preventative ignition coil replacement in the 120,000-mile range (also a good time for a new E30 fuel pump and new main and fuel pump relays). Wowie-neato ignition wires are, in my opinion, unnecessary on BMWs. The factory parts ARE high performance parts.
Driven in anger, the M42 engine will begin to voice its desire for a new timing chain and associated parts around 120,000 miles or so. The telltale is a rattle from the front of the engine around 2,000 to 4,000 rpm. Ignore it long enough, and the chain will break, causing massive engine failure. Note that many of the timing chain parts – rails, guides, tensioner, etc., have been updated to M44 parts in the BMW parts system.
A good high performance exhaust system such as the Supersprint cat-back system can also net you a few more ponies. While the power increases are slight on this car, they are easy to notice because output is so low to begin with. Another modification that can net you a nice increase in acceleration is a differential swap. The E30 318i convertibles had a 4.27 differential. Naturally, they're hard to find on the used market and limited slip is even harder to find, but they are available rebuilt from BMW if you want to spend the money. A 4.27 diff was the first thing I did to my 318is. Combined with the overdriven fifth gear, I find highway cruising in the standard 80 mph range to be comfortable – but others differ. In my opinion, with a four-cylinder BMW, we need to resign ourselves to the concept of high rpms. Let it rev – I do.
You might also consider a good short shift kit, as the factory parts are rather sloppy and long of throw.
The chief problem with the 318is suspension is the factory springs. For some reason, BMW gave the US-specification 318is great shocks -- BOGE units actually shared with the E30 M3 -- combined with positively horrible coil springs, particularly at the front. The front of an E30 318is looks like it is set up for the Dakar Rally -- it is way too high. Bilstein shocks are highly recommended – either HDs with the stock springs (oh those horrible fronts) or Sports with shorter, stiffer aftermarket performance coil springs.
If you must retain the stock springs, you can lower the front of this car and any E30 except the 325iX by 10mm using ingenious upper spring hats from BMP Design (
http://www.bmpd.com), pn 139009 ($160). These wonderful parts, also available for non-M E36 3 Series cars including the Z3, are total no-brainers. You simply remove the strut assemblies, compress the stock coil springs, remove the factory upper spring hats, fit the BMP Design units, and bolt the assemblies back in. And yes, they can be used with aftermarket springs, too, for an additional 10mm drop, but the hats are not necessary or even a good idea on the street if you have aftermarket springs – the front will be low enough with the stock hats.
While you're working on the front suspension, you need to make one other improvement. Swap out the stock control arm bushings for solid rubber offset units for the E30 M3. In addition to being a great deal stronger, E30 M3 offset control arm bushings provide some extra caster for greatly improved high-speed stability. You can get these from BMW or from almost any BMW parts house for about $100. They're worth every penny!
After either or both these suspension modifications, you will need a front-end alignment.
Larger sway bars are also an easy upgrade for the E30 and other BMW models. And if you're running the stock 14x6" alloys, consider upgrading tires to 205/60-14, and also consider the Yokohama AVS ES100 in this size -- these tires will rock your world.
© Mike Miller 2003
Topic: Mike Miller's take on the E30 M42 (Read 8463 times)