More power - 318is

[cheffy]

Any subtle mods I can make to my 318is to get a wee bit more power ? nothing major !

[Speedtouch]

A chip will give typical gains of 8-12bhp. I can supply one.

[DHFiS]

How much power is it producing now?

[cheffy]

How much Speedtouch ?
DHFiS - its totally standard at the mo ! so no doubt over the years it'll have lost some of its horses, I more more thinking about things like performance air filter, performance Ignition leads, and plugs ? and then maybe just an old fashioned tune-up !!
How much extra power would this give ??

[DHFiS]

If your car is totally standard then it already has performance air filter, ignition leads and plugs.

Before you change anything I would service it and get a dyno print out so you know how it performs.

Other than a new chip you can't get cheap increases in BHP from the M42.

[sweep]

Have a word with appletree on here.

[Grrrmachine]

The "performance" air filter will reduce power. The "performance" ignition leads are a scam, like gold-plated HDMI cables.

Get a Speedtouch chip to adjust the map, and pull your injectors out and get them rebuilt with Injectortune (in the Trader's section). Bringing your M42 donk back to the way it left the factory is by far the easiest and cheapest way to increase the horsepower. Beyond that, anything short of increasing the bore/stroke of the engine is just bolt-on bullshit designed to lighten your wallet.

[cheffy]

Thanks all - hopefully getting 320Tourung on here, to have a wee look this w/e - also got a wee oil leek, haven't used the car at all since I got it (a 240 - odd mile drive home) - mainly cos of the oil leek, but also want to sell my E46, so using that with For Sale notice on !
I haven't really driven it "properly" yet - so it may be ok tbh ? just thought Id run it by you peeps for an opinion really.

[Brianmoooore]

IIRC, the cam timing on an M42 can be adjusted (with standard parts) to give a bit more BHP at the top end, at the expense of torque lower down.

[AardHawk]

Weight reduction is the only guaranteed performance increase.

[cheffy]

OK thanks folks, so a chip is really the best way then ? probably just leave it for now, only just got the car about 3 weeks ago and haven't really driven it yet, was only interested to find out IF a power increase was poss / what needed to be done.

[Brianmoooore]

OK thanks folks, so a chip is really the best way then ?

No, getting it running the way it was when it left the factory is the 'best way', and essential before anything else you may choose to do, and as I posted above, the shape of the power curve can be changed by adjusting a cam sprocket in its slotted holes.
After it is running as it should, a correct chip for the software your ECU uses can give very small, but worthwhile, gains by eliminating some of the compromises that BMW had to write into their software to allow the car to operate under much wider climatic and fuel quality conditions that it is ever likely to encounter in the UK.

[SGP]

^^ Word

[Mitchen]

OK thanks folks, so a chip is really the best way then ?

No, getting it running the way it was when it left the factory is the 'best way', and essential before anything else you may choose to do, and as I posted above, the shape of the power curve can be changed by adjusting a cam sprocket in its slotted holes.
After it is running as it should, a correct chip for the software your ECU uses can give very small, but worthwhile, gains by eliminating some of the compromises that BMW had to write into their software to allow the car to operate under much wider climatic and fuel quality conditions that it is ever likely to encounter in the UK.

How can we know it's running the way it was when it left the factory? I've done pretty much everything barring refurbing the injectors, which is on the list, but other than my E30 I've never driven anything other than modern cars.. Like maybe a lot of members I've never driven one of these cars when they were new or fresh.

So how would we know when our cars are operating at factory standard? and thus ready for subtle chip upgrades. Mine drives and feels ok.. for a 25 year old car.

[capnmchl]

Get it dyno'd. See if the power and torque curves look like those in your owners manual.

[DHFiS]

So how would we know when our cars are operating at factory standard? and thus ready for subtle chip upgrades. Mine drives and feels ok.. for a 25 year old car.

Before you change anything I would service it and get a dyno print out so you know how it performs.

[Brianmoooore]

What's the MPG like? Does the car accelerate smoothly with no hesitation? Does it idle smoothly at the correct RPM? What's the gas results from its MOT tests? (Always ask for the results sheet.)Is the AFM bypass pot. undisturbed? All these are simple clues requiring no effort to obtain at all.
What do the spark plug tips look like? Perform a leak down test, or at least a compression test. Check the operation and adjustment of the TPS (not relevant to a M42), and most importantly, get the injectors rebuilt - these are fundamental to mixture control, and you can assume that they are worn and mismatched if they are 50,000 miles old.

[tim_s]

Agree with the above, on most standard ones I've seen repairing air leaks and replacing all the perished hoses on the inlet (esp around ICV etc), fixing cracked exhaust manifolds (every single original m42 manifold I've seen that's not been repaired is cracked around cyl 1), resetting cam timing which invariably has gone off over time/age/chain stretch and the like all contributes to getting the performance back to where it was out of the box and would make more difference than any bolt-ons. After that, chip, removing the viscous fan clutch for an eleccy fan, adding a bigger TB and reground cams made a little difference I found. Then it really does require engine surgery to make it go any faster.

[Brianmoooore]

No gains of any significance to be had from fitting an electric fan, I'm afraid, just a considerable decrease in reliability and increase in the chance of overheating.
An electric fan doesn't run for free - it runs on electricity, which is generated by the engine, using power and petrol to do so, and the conversion of rotational energy to electricity and then back again from electricity to a rotating shaft is very inefficient, losing most of the power as heat in the process.

[Speedtouch]

Why is it that most modern cars have electric fans then? I was under the impression it was because the fan can be switched in at optimum moments in the engine's heat cycle, thus making it more efficient overall.

[Brianmoooore]

The main reason is that the radiator isn't positioned neatly in front of a convenient rotating pulley any more - especially with most cars having transverse engines.

[Grrrmachine]

Modern fans are electric for reasons of space; you don't need a thick clutch right behind it, or a belt and pulley, to make it run - you just run a wire from a convenient place in the loom.

In terms of making air move, there's no difference in efficiency. In terms of accurately triggering the fan, they both rely on a thermo effect to trigger when the fan comes on, neither of which are accurate to fractions of a degree so its not going to make the engine run better - besides, it's the thermostat controlling engine temp, not the fan.

All an electric fan does is put more load on the electric system, and add a lot more failure potential in the sense of snapped looms, corroded earth points, blown fuses and dead relays.

[tim_s]

Er, not when the electric fan's off! But yes, will not run for free in traffic. Makes a difference on a 318is.

[Brianmoooore]

Viscous fan is 'off' is normal driving, and soon turns 'off' when you start moving at speed after being in traffic. If stopped in traffic with a fair bit of other electrical load on, including an effective electric fan, you will probably be draining power from the battery, which the alternator will be replenishing for some time after you speed up, acting as a significant brake on the engine.
BMW fitted an electric fan themselves to versions of the E30 where it was needed, don't forget, so why would they fit a viscous coupled fan as well if there was an advantage with the electric?

[Speedtouch]

IIRC, one reason electric fans were introduced was to deliberately run engines a bit hotter (or at least, to enable them to heat up quicker from a cold start) in an effort to improve fuel economy and reduce emissions, along with lean-burn technology, etc.

[Brianmoooore]

Bypass thermostat allows the engine to heat up quickly. Standard on E30s from the start.
Fan cools the radiator, not the engine (apart from a minimal surface cooling of the block), and if the 'stat is bypassing the radiator there'll be no effect on the engine.

[tim_s]

I'd always assumed the thermo fan clutch meant that the fan had some load on it when the engine was at normal operating temp, hence the advantage of an electric fan. Is that not correct?
I'd also thought there was probably a cost and packaging advantage to a viscous clutch + fan.

[Brianmoooore]

You can stop the fan on a viscous coupling at engine running temp. with a newspaper and easily hold the blade from turning with the tip of your little finger. Whatever power the free wheeling fan absorbs, it's extremely small! When the car's moving at speed, I doubt if the blades are turning any faster than they would be as a result of the airflow if the fan was truly free wheeling.

[appletree]

I'd always assumed the thermo fan clutch meant that the fan had some load on it when the engine was at normal operating temp, hence the advantage of an electric fan. Is that not correct?
I'd also thought there was probably a cost and packaging advantage to a viscous clutch + fan.

Sorry to high Jack

Hi Tim how you doing, blast from the past!

[reggid]

i dont get why people have an obsession for electric fans. the viscous one works fine when in good working order and ive lost count of the number of people who fit too small a electric fan and have issues.
perhaps if you tracked the car and you used an electric fan that turned off at speed you might gain a few watts

[cheffy]

Wow ! thanks for all the info, but all way to technical for me !!Brian with regards to mpg it seems fine, but not driven too much, but on my 240 mile drive home when I bought it, mpg was v good, and yes it does accelerate smoothly and it idles well but I'll have to check at what RPM ? All in all I'd say it goes real good, had it out for a quick drive yesterday and I was quite impressed throughout the gears - excep,t as I've mentioned previously, it judders a bit in 1st gear in slow moving traffic ? could this be a clutch related thing ?
I've just finished detailing it, so hope to get some pics up soon

[NoTurbo]

I would only recommend what has already been said + a lightened M20 flywheel.

The flywheel makes that slow pickup a thing of the past and is probably the best mod you can do to a 'standard' M42

P.S. Do you have an LSD? IF not a high ratio rear diff will also make it accelerate better.

After these mods the best thing you can do is buy a good set of tyres to wrap around those 15" rims. Good tyres will give you the most benefit of all.