Quickest E30 318is.. how to do it?

Here is Brian Purcells Article :

The Greatest E30 ever? by Brendan Purcell

 

Okay, okay, I won’t try to make

out that anything other than the

M3 was the pinnacle of all the

many E30 models. So maybe I

should start by coming clean

and calling the article ‘the

Second Greatest E30 ever!’

Although the M3 was the icon in most people’s eye, it had a couple of drawbacks which made it impractical for many, not least of which were the increased maintenance, insurance, security and purchase costs. Then add in the left-hand drive stipulation. So the runner up was the 325i Sport then. Well, not so fast. BMW, in 1989, had another 4 cylinder 16 valve car with characteristics similar to the M3’s S14. The engine used technology derived from Formula 1 and touring car successes, with cylinder head and inlet manifold design akin to previous M cars. This engine had a forged crankshaft,

pent roofed chilled cast aluminium alloy cylinder head, Motronic controlled coil-percylinder ignition with semi-sequential fuel injection, specially designed 3-electrode spark plugs, finite-element lightened pistons and con-rods, hollow camshafts, hydraulic lash adjusters, a duplex timing chain, twopiece inlet manifold and 10:1 compression ratio.

 

The engine was of 1796cc, designated M42, and generated 136bhp minimum, therefore yielding 75.5 bhp/litre. Many run-in engines produced around 140bhp yet could return 47.9 mpg @ 56mpg, 37.2 mpg @ 70mph and 26.9 mpg Urban. It weighed 13kg more than the existing M40 engine while being just 30mm taller. BMW briefly introduced this engine in the

E30, although it was much more extensively used in the follow-up E36 model. It was their first non Motorsport production 16 valve engine. Solid rear and ventilated front discs from the 325i were fitted. BMW adapted the Mtech suspension for the lighter engine, giving, in Europe, a 20mm front anti-roll bar, 14.5mm rear anti-roll bar, uprated gas dampers (in 51mm struts up front), -15mm front and –17mm rear uprated springs. A 4.10 differential was fitted with a limited-slip version being optional. The result was a reasonably quick car which was broadly comparable to the Gti brigade at the time.

 

However only now, when comparative focus is turned inside the BMW range, is it clear how its character was very much akin to the M3. The engine had a pronounced power jump at about 3750rpm. Although lacking low down oomph, it really flew above 4000rpm. In many ways the M3 also had a similar high end biased delivery. But if the revs were kept up, its power disadvantage on the road to the 325i was not so great (other than in top speed). 325i’s usually had greater specification, were higher geared and, given the M20 engine, ended up being sometimes over 100kg heavier!

 

Anyway, E30’s were not so much about drag racing... Its weight distribution was very close to the M3 too, with comparable spring/damper settings, although not quite as stiff (especially in roll). Cornering balance was almost identical though, even though the M3 had the greater outright grip. The car was shadowlined (dechromed) as standard, sat lower due to the M-Tech springs, had an extended front spoiler and generally sat on 205/55/15 or 195/65/14 basketweaves.

So, here was an E30 which handled and delivered power in a manner similar to the M3, yet cost less than £15,000 new. Its maintenance and running costs were low; fuel efficiency and emissions excellent. It used state-of-the-art technology in its engine while taking the best of established engineering in terms of braking and suspension.

 

It easily outperformed the 316i, 318i and 320i while out-handling the 325i. Although being down on power against the 2.5 litre engine, it could still give a decent turn of speed when kept on the boil, yet could return an overall fuel efficiency in the thirties. It was relatively rare car, with just 41,234 being made in less than three years. You can get a clean example nowadays for as little as £3000 - less if your standards drop.

 

Oh yes, the second greatest E30 was called the 318is. Written by Brendan Purcell, BMWCCGB Ireland Region, see his web site for more details of the E30 318is at:

 

www.esatclear.ie/~bpurcell/index.html.

 

38 BMW Car Club Magazine

 

Why not just get and E30 M3. There are still loads of people out there that dont know what they are. Even a 325 driver didnt seem to know what it was when I was behind him and hinted that he should pull over. Took a sneaky look at his face as I roared by him and his face was a picture. "WTF"

You should be able to get good money for your 318is and you can get a good 325i sport for around £3-£3500. Ive had two and they are ace.

Got to agree about 1st gear both mine were like that, I usually set off in second.

In terms of the top speed my clock said I was doing 152 MPH. Obviousley clocks arent 100% correct but I think 140 is a bit on the low side.

Chris 

Madrab, unsprung weight has nothing to do with acceleration. For a wheel, it has to be accelered in two dimensions - straight (like the rest of the car) and rotationally (around its axle). The rotational interia is based on a radiused squared formula - so the further out the weight is on the wheel then the more inertia it has - the flywheel effect (even if the overall weight can be kept the same).

Unless you spend silly money, modern alloys are not a lot lighter than wheels from a few years ago - actually some designs are extraordinarily heavy.

Unsprung weight affects how quickly the wheel moves in relation to changes in the road surfaces.

Edited by b318isp

Yep beema it sure does.

From the info I gathered the 318is was modelled on the 325is chassis with the better tuned chassis and slightly different suspension set up but was all M-Tech qualified spec.

The quoted figures I've got for a stock 325i is 136mph whereas the Tourer is 133mph. Mine isn't standard though and have had some fun with same type of 325i owners that I think you are talking about. I've had the speedo just over the 140mph mark though but haven't managed to get an accurate 1/4 mile yet to confirm what the top speed is. 0-60 time is approx 7sec.

Oh yes mini's with that sort of power are stupid! But are a giggle! You could get one as a second car..325? No problem!

So really a 318is has a better suspension setup to a standard 325i?

Madrab I'm going to take your advice on some of the engine mods... ie.  free flow panel air filter/induction kit, free flow exhaust manifold and system and an ECU swap. And see how we go... Has anyone else already got a similar setup on a 318is?

And the tourer 325i probably is better balanced than a saloon.. for obvious reasons... but is it quicker than a saloon in a straight line?

Hi sir,

is that what you call a moderator?

Don't really want to try to split hairs but with regards to the extra rotational inertia for bigger wheels, I thought that would be reliant on total unsprung weight? If the new, larger wheel and tyre weight is the same as stock, due to newer, lighter wheel materials used, and the same rolling diameters, then would the unsprung weight's inertia not balance out? i.e. would require the same energy input to move? There are variables though?

Well the 325i gives up 70kg to the 318is so that's a start and they do say that the 4pot e30 is more balanced than the heavier 6 pot lump though I wouldn't necessarily agree with that where the touring is concerned as the weight distribution is better than the saloon (being a tourer owner I would say that eh? hmmm)  and they do have the heavier duty Mish suspension set up.

With 17"/18" wheels, their car would be slower accelerating if they don't use the correct profile tire to keep the rolling diameter of the wheel the same as stock and it ended up larger. They may have better handling than standard though (in dry anyway) with their larger wheels and rubber.

Only the 325iS had the full M-tech setup, I believe, though your 318is should have the stiffer M-tech springs and shocks 2, minus the thicker roll bars.

Thanks for all the feedback... i know the 325 has about 35-40 bhp extra... but than it also weighs a bit more .. so its true if i lightened the car and do some mods on the engine it should be possible... I also read somewhere that the 4 pot E30 handle little easier/better than the 6 pots due to a lighter engine and better weight distrbution... so around twists and turns a 325(unmodified) should have quiet a challange against a 318is... do all 325's have m-tec suspension??  and sports seats etc.. ? o yeah and if someone has like 17/18's on a standard 325 that should drop there performance a little shouldnt it.. ?

personally i think the iS is perfectly balanced.. not talkin about performance but it is the best car ive ever driven...

have a look at our own B318isP's website
www.esatclear.ie/~bpurcell
This guy has done a number of mods to uprate the car (chip, panel filter, suspension, etc.)
(still slower than my e30 320i SE - but then again that was on an economy run )