...E30 Freshening (Redux)
I didn't realize we needed to get quite so intimate. I don't have answers to many of the questions you pose. I am looking in the first instance to get a plan together for the project. Perhaps it is best to begin with basics and then try to formulate my vision.
I am the cars third owner and it is in excellent shape. It has 240,000km. on the clock--it is a Canadian Car and I am in Canada. It has been serviced at bmw always except for approximately 40,000 km. when in the care of the second owner. It has never been driven in the winter. I use it in the summer as a daily driver with qualifications. That is, it competes with my motorcycle and it is the only drop top in the fleet so often gets scooped by my wife or one of my children.
That said I envision a sleeper. No modifications that do not enhance performance and as few as possible that are visible. The car has lovely lines and, at least where I am from, is much more exclusive than an E36 or 46 rag. I like to do my own work and can do most of it. I can not, however, shoehorn an M50 into it. My difficulty is that I get busy with work/family, etc., and my projects get delayed/abandoned first. I am desirous, therefore, of having a plan I can implement in stages and I can do individual stages myself or farm them out.
The question that needs to be answered first is how much horsepower? That of course effects brakes, suspension and body work. I do not want to do brake and exhaust/intake upgrades now and find out later they are insufficient for the horsepower I end up with. I am happy to spend money but not keen to waste it. The manual says it puts out 175 ponies with 169 lb-ft of torque. It is by no means slow but can you ever have enough?. I am convinced I can get another 25 horses with intake/exhaust and chip but is that enough?
How much can be messaged out of that engine before it looses driveability? I don't mind a lumpy idle but I still need to be able to let my daughter drive it. If we imagine more significant work like a turbo/supercharger what are my options? I did actually read in your publication about a shop that stuffs M50s in. How much can the horsepower be increased before we need to make driveline modifications? Am I limited buy the chassis' inherent lack of rigidity?
Once I figure out how much horsepower I need, I then have some questions about the rest of the project. How much stiffer can/should the car be? Does it do any good to brace the strut towers given the lack of a roof? I don't think I want a rollcage in my car. I would like to upgrade the suspension even though the stock stuff shows no signs of wearing out. The stock wheels are in excellent shape but do look a bit dated. I am not convinced I like the look of 17-in. wheels if it will leave only wafer thin tires given the cars current configuration. I still prefer the look of some rubber, so maybe 15- or 16-in. wheels, unless of course we decide on enough horses to require bigger rubber overall. I don't think I want to start flaring fender wells at this point.
This has been rather therapeutic. If I stick just to upgrades in the suspension, brakes and wheels and message as much as I can out of the mill what will I end up with. I am all for more fun but not at the price of additional headaches nor do I want to have to sort out a story about the car failing as the reason for my daughter being several hours late coming home.
Thanks,
Steve
Initially, with 249,000 Km (149,000+ miles), we need to take into account the condition of this engine. After all, if you take your grandfather and make him run sprints he may be able to do it, but whether he'll survive it is another question. I'd recommend you do cylinder compression and leakdown testing to gauge the condition of the bottom end. If this engine has never had a valve job, I can almost guarantee it needs one now unless it has been driven very sedately. Also, basic issues like air and fuel filters, spark plugs, cap and rotor, valve adjustment, fuel injectors, water pump, timing belt, cooling system service need to be verified or addressed before any thought of increasing power on a mature engine. At this mileage, catalytic converter and oxygen sensor condition are also in question.
The standard bolt-on modifications for the M20 engine include a chip, cone-type intake, and a performance exhaust system. I would say you're looking at bolting on a good 25 hp with these items assuming you can get fuel good enough to satisfy the chip and assuming the engine is in good condition. That's about all you're going to get without removing the engine for a complete rebuild using high-compression pistons and a Schrick camshaft, along with lightening and balancing of the reciprocating mass. There are no superchargers or turbochargers available for the M20 engine, and even when turbos were available, they requried low-compression "turbo" pistons due to this engines lack of knock sensors.
Bear in mind the maintenance requirements of an oiled cotton gauze air filter.
These bolt-ons will not affect driveability as long as the engine is maintained in good tune and good high-octane gasoline is used. Engine longevity depends far more on maintenance and severity of service than what performance modifications are bolted employed. Make sure you use good motor oil, BMW filters, and bear in mind that today's ultra-low-viscosity 5W-30 has no place in an E30 except during Canadian winters. The rest of the time, you should be running 20W-50.
Yes, the M50-into-E30 is a popular conversion, but as with all conversions one should not enter into it expecting to save money over a performance engine rebuild--it'll probably cost more.
The best speed secret for an E30 six-cylinder with a five-speed overdrive manual gearbox is a 4.10 limited-slip differential from an E30 M3. While not exactly falling off trees, especially in Canada, these components can be found on the used parts market, and it will greatly increase acceleration and top speed (due to the increased pulling power against wind resistance), at the cost of a bit more rpm at any given road speed. It is a direct bolt-in.
As always, Red Line MTL and 75W-90 are recommended for the gearbox and differential.
The robust E30 drivetrain and chassis is capable of handling a great deal of power, upwards of 300 hp in my opinion. There are E30s running around with M6 engines and even M60 V8s, although this makes them very nose-heavy. Nothing you can bolt-on to an M20 is going to overtax your brakes, but again at this mileage I would be concerned with the basics--condition of the hydraulics if the brake fluid was never changed, rotor and pad condition, swelled rubber brake hoses, etc. A standard rehab of these parts, good brake fluid change, and use of new rotors and performance brake pads will be all you need.
As with any BMW, the fun quotient is best increased with suspension improvements. The E30 can be made to handle like a slot car if you are willing to put up with lower ride height and firmer ride quality. Again, we want to make sure the basics are sound--steering parts, ball joints, rear suspension carrier bushings, trailing arm bushings, etc. The hot setup is Bilstein Sport shocks, the performance coil springs of your choice--Eibach, H&R, and Racing Dynamics are popular--E30 M3 offset front control arm bushings, and a set of large sway bars with mounting reinforcements from
www.turnermotorsport.com. You can also run E30 M3 aluminum front control arms for a 4.4-lb. weight savings at each side--nice especially when fitting heavier wheels and tires. A plethora of factory and aftermarket 15-inch wheels are available, on which you will want to mount 205/55-15 tires. The 225/50-15 size is also correct, but added clearance may have to be worked into the fenders and quarter panels. For your purposes with this car, 205/55-15 ultra-high performance tires such as my new favorites, the Yokohama AVS ES100, will be more tire than the car will know what to do with.
Normally, I would say that a strut brace isn't going to function except under extremely hard cornering forces, however on a convertible I think there may be other benefits. Bear in mind that the more you firm up any convertible, the more cowl shake you will get over rough road surfaces. Unless you want to add a roll bar, that's just the way it is.
None of these mods are going to affect reliability. If the car breaks, it's unlikely to be because of anything you did to it. Here's a tip: Replace the main relay, fuel pump relay, and the fuel pump preventatively. Just bite the bullet. I was once stranded in at the base of the Dempster Highway outside Dawson City, Yukon Territory, in an 120,000-mile E30 rally car with a dead fuel pump. Trust me on this.
If your daughter comes home late, it probably won't be due to the car. One other bit of advice: In my humble and decidedly non-sexist experience, the average life of a front air dam on a lowered BMW with a female driver is approximately one week. They are not wired to think of this kind of thing, just as men are not wired to remember dates and anniversaries. School your daughter in the perils of speed bumps, inhospitable driveways, and especially parking curbs. A label maker sticker on the instrument cluster that says, "Remember: 5 Inches of Ground Clearance," may help, too.
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