N/A Tuning the M42

[Jon_Bmw]

It is not when you are talking about NA tuning though! If you do every aspect of the engine build yourself, you are still in for over £2k in parts to get close to your 200bhp benchmark. £1500 for the labour side of things suddenly doesn't seem so bad. There is so much more to engine building than just stripping it down and putting nice shiney new bits back on. Well at least there should be.

Rally boys are people who need to modify their existing engines(so like you, for some reason) to meet regulations hence the comparison. They will drop big money to get the power they want out of a low'ish CC engine, so you are likely to have to do the same. Simple?

Keeping the capacity the same, there is no way you are going to make the 1800cc be torquey around low rev ranges and get to your target of 200bhp, but I think you know that anyway.

Tuning a NA engine is a mugs game, one I am caught up in.

[Royalratch]

It is! If an engine builder isn't going to get me off a murder rap then it's not worth it.

[Dave_M3]

To be honest... 65bhp extra on an engine that only produced 136bhp from the factory (although a re-map will see 150) is preety decent for 6K and have an engine ready for you to drop in.

An S42 manifold and exhaust system costs more than that kinda money alone!

But... a 6K-10K engine is nothing to rally boys when entry fees can cost a few grand to start with on some occasions so having the proper tools is worth the money!

[Royalratch]

Well this has seriously put the whole thing into perspective. I will still do some tuning, not least a remap, lightened flywheel and skim but even cams are looking less of a hot deal if they only work at the mid-top end and change driving characteristics.

[tim_s]

Ratch you live near me, give me a shout in the new year when i've finished peeing around with my shed and you can see for yourself. It's a completely different beast at lower revs, way way stronger - i make more torque throughout the rev range than a good 325, but also can rev to 7,5k and make more than 190bhp from 5,5k to the limiter.

[Dave_M3]

Its comments like that is why I want to build mine so much

I just need to get some pistons now.
getting my hands on the crank and M44 block this week

[ShepsEvo3]

Ratch you live near me, give me a shout in the new year when i've finished peeing around with my shed and you can see for yourself. It's a completely different beast at lower revs, way way stronger - i make more torque throughout the rev range than a good 325, but also can rev to 7,5k and make more than 190bhp from 5,5k to the limiter.

I agree with Tim here... My 318is feels pretty lame in comparison to Tims 205bhp engine. I have some dyno plots somewhere with Tims graphs overlayed over mine and a standard 318is. When you see the torque difference, you'll know you wanna go 2.1 with a diesel crank. But what suprised me more was how the dips and troughs were still in the exact same places in the rev range on all 3 cars.... freaky!

Paul.

[Barx325i]

could the flatspots (dips & toughs) be the RHD exhaust manifold?

[ShepsEvo3]

could the flatspots (dips & toughs) be the RHD exhaust manifold?

Well, I suppose the intake and exhaust manifold were the same on all cars, unsure about Tim's exhaust system though, but certain the manifold was standard?? So with this is mind, it must be some harmonic/pulsing thing going on within the intake and exhaust systems.

They were not flatspots as such, but as my dyno graphs autoscale, you can really see the peaks and troughs in the torque curves. It may only be 2ftlbs drop, but it is shown like its 10ftlbs lol. On other dyno's where the power and torque are scaled the same, ie from 0 to 150bhp and 0 to 150 ftlbs you won't see such dips. My dyno would scale power from say 30 to 150bhp but the torque maybe from 90 to 120ftlbs, basically minimum and maximum figures seen at and between the run start and finish.

[Barx325i]

It was just my first thought, they're definately constants & the rhd manifold is a compromise.. I do need to build a none standard m42. There's one on the w.shop floor ready for this!

A friend is rallying his iS.. He uses and m44 crank forged GM pistons & stand alone mangement. I'll have to get the details but it's superb. no figures for it yet

[Royalratch]

Ratch you live near me, give me a shout in the new year when i've finished peeing around with my shed and you can see for yourself. It's a completely different beast at lower revs, way way stronger - i make more torque throughout the rev range than a good 325, but also can rev to 7,5k and make more than 190bhp from 5,5k to the limiter.

Will do mate. I don;t need to see it to know it will revelatory.

My turd will be on the road then so I'll get that out and we'll do a drag race from Marble Arch, down Park Lane, round Hyde Park Corner and round back up Park Lane.

At the right time of night, you can clear all the lights!

[flavyphil]

you guys might find this thread interesting
http://www.m42club.com/forums/showthread.php?t=1385

[appletree]

318iS isn't completely standardish though.
circa 150-160bhp with the usual mods like chip, heater plate and all that heat exchanger shite removed, live re-map.
M20 flywheel lightened to 5.9Kg (this makes a good difference even on its own)
6 speed box,
4.1 LSD,

What is the 6speed box from E36 M3 evo?? do you use the same starter motor as if you did the swop on an M42 box? m42 starter motor with early m20 323 spur gear??

[Dave_M3]

Yeah, E36 M3 Evo. Box was is shite though but I already knew this as it was in a friends drift car and I did get it for free.
Was only to see how it fits and drives. Have an E46 M3 box for it now so will be putting that in when I find a M3 flywheel that weighs next to nothing as I'm restricted to a E46 M3 clutch unless I can find a 228mm clutch disc that has the same input shaft splines as the E46 gearbox.

Yeah, same starter motor setup if I used it with the 220 box.
M20 lightened flywheel, 325i clutch and release bearing, M42 starter with the M20 gear swapped onto it.

[tim_s]

6 speed must be mint! Do you use m42 f/w with the evo box? Would be an issue for me to change f/w having the whole bottom end rotating assembly balanced together inc the lightened f/w and the clutch pressure plate etc.

[appletree]

6 speed must be mint!

just what i was thinking Tim! keep it in the power band

what diff are you running with it dave?

whats it do to the crusing speed in 5th? i alway think mine could do with another gear and the ability to take more bhp and torque, haveing a longer top and still enough gears lower down to keep it fun would be great

do you need to change the prop shaft or can you use the standard IS item. your running with a 325 clutch and what release bearing? is the the e21 one they use for the 323 flywheel swop?

what about gear stick linkage?

fancy starting a new thread with pics and details?? please please

realy liking the idea, heard people mention it before but never nown anyone do it.

[rix313]

Which of the heads is better? The M44 or M42?

[appletree]

Think the early E36 M42 heads are the best, although i maybe wrong.

I got one buy accidnt when i bought some M42 heads and blocks off kedge on here, i'am using one on my new build, its got 6mm valve stems which is alittle bit of a pain when it comes to buying valves as there never listed in catolouges.

There slightly more sort after for the higher power N/A builds as apparently with the slimmer valve stems you save around an extra 140g on the valve train althought you do loose the sodium cooling the standard M42 7mm valves have iirc although i'am not certain as ive swopped to some solid valves from supertec anyway:D

[Dave_M3]

You can use the M42 flywheel and clutch Tim. Would make it easier to be honest as you wouldn't have been messing with the starter like I was with the M20 flywheel.

I just changed mine to an M20 one as my M42 clutch was in shite and the fact I wanted to loose some inertia.


6 speed must be mint!
just what i was thinking Tim! keep it in the power band

Its pretty cool alright, 1st, 2nd and 3rd gear is a laugh as acceleration is better obviously and more fun and involving as you have an extra gear to play with before you get to silly speeds.

5th flat out is about 180kph... quite amusing when jap scrap is trying to race you and hit their limiters at 180 while you appear to be flat out too before you grab another cog

The only thing is the gear ratios are slightly wider apart than in the 220 box so you could drop out of the power-band with an standard M42 but with more power right across the rev-range from a stroker or supercharger it would be perfect.

Acceleration is faster with the 6 speed than the 5 speed with the same diff ratio and slightly faster with a 3.91 than a 5 speed with a 4.1. A 5 speed would be faster with a 4.45 alright than a 4.1 with the 6 speed but the reduced economy at motorway speeds and roaring engine isn't what I want.

what diff are you running with it dave?
4.1 188 LSD at the moment until I rebuild a 3.91 with 40% lock.

whats it do to the crusing speed in 5th? i alway think mine could do with another gear and the ability to take more bhp and torque, haveing a longer top and still enough gears lower down to keep it fun would be great

6th is the same ratio as 5th would be with the 220 box but the fact you can drop down a diff ratio while still have gears that are still quicker down low is the advantage.

do you need to change the prop shaft or can you use the standard IS item. your running with a 325 clutch and what release bearing? is the the e21 one they use for the 323 flywheel swop?

Had to shorten the prop shaft about 4 inches or so and I used the front end of the M3 Evo prop so I could use the stronger rubber coupling

what about gear stick linkage?

Angle grinder and tig welder to shorten them

fancy starting a new thread with pics and details?? please please

realy liking the idea, heard people mention it before but never nown anyone do it.

I don't really have any pics to be honest but will take some when I'm putting in the E46 box as they are physically the same so are the same in terms of fitting apart from the clutch.

[jaistanley]

A friend fitted an E46 6 speed to his E36 325i.. Clutch issues meant we ended up getting an E46 clutch plate and had it machined down to the same diameter as the E36 one and fitted it with the E36 flywheel/pressure plate.

Worked OK but as he had E36 diff, the ratios were too long and he lost all the advantage of having the 6 gears! Before he got round to changing the diff he saw sense and bought an E36 M3GT...

Jai

[Dave_M3]

Yeah, was thinking of that but not too happy about it to be honest... I'd much prefer a proper lightweight flywheel that weighs next to nothing and then the decent sized clutch.

For a 325i, I would have liked the idea of the bigger clutch to be honest... only reason I'm slow to use the E46 one at the moment as I aready have a M20 flywheel thats lighter than 6kg...