Roadgoing Sprint/Hillclimb Engine Choice

[e301988325i]

Little update guys.....

I picked up my new m20B25 yesterday and stripped it before transporting it back.

It was in great condition and had come from a 100k mile car but the shells and mains were almost good as new!

Cant believe how heavy it is even the bare block is difficult to heave around on your own.

Ive had some intersting email correspondance from Fritz Bitz with regard to tuning this 6 pot beauty. They have told me not to worry about enlarging the inlet ports as the inlet charge speed will drop and looking at the standard port sizes im inclined to agree with them. They did however say using 1mm bigger inlet valves is a good idea and working the area around the valve seat
/guide area is worth 7% better flow

With regard to the bottom end i will be renew the shells and mains for good measure but i dont have any experience with crank lightening/balancing etc. As far as im aware reducing reciprocating mass as much as possible is very much worth it so the engine will love to rev. Looking at the crank the counterweights are huge and it looks in theory that a lot of material could come off them. Do any of you guys know much about bottom end tuning or anyone in the southwest who is renound for that kind of work?

I will also be trying to find the lightest flywhel i can and wondered if its worth shelling out for a nice aluminium one or just machining the current one as much as is safe?

Cheers

I'm not surprised the bearings aren't worn, I wouldn't have bothered taking it apart.

Being a tri-plane crank it is inherently better balanced and really doesn't need extra work (if you've unlimited budget then go for it). The rockers are only safe for 7,000rpm which are your limiting factor rpm wise. The stock flywheel is 10Kg, reports of going down to 6Kg which will make a large difference.

I strongly reccomend fitting the close ratio gearbox out of a 325i sport, the difference is quite surprising.

If you've got money to spend on the engine then the first place to spend it is on a btb3 sixbranch manifold, their exhaust is great but a 2.5" single pipe can be fabricated for much less, this will give an extra 10bhp+ straight away.

Ps) there is a group buy for the BTB3 at reduced rates currently running in the group buy forum, the deadline is very fast approaching.

[Hoobs]

Just my two cents as I have spent the past 9 months doing sprint events & track-days with an M42 powered e21. My car is pretty light although there is still more lightness to add. I tried to make the most of the limited power by using a close ratio gearbox and a pretty low ratio diff. (4:1) It's pretty much perfectly geared for Brands as I max out just as I brake for Paddock.

Next year I need more power in order to be competitive though and have been considering an m20 or s14 myself. I have an M3 so know what a cracking engine the s14 is but my budget would be all but wiped out. The m20 is a much cheaper alternative obviously and keeps me within the regs. It's a shame that there not more power easily & cheaply found in the m42 though as it's been bullet proof all season. Don't bother trying to chip an m42 either. I tried 2 different ECU and it just wouldn't work.

[DoctorDrift]

Interesting thoughts guys and its nice to see interest in this thread developing again

i still find it hard to understand why the m42 isnt tunable. surely 100bhp/litre should be achievable for most engines and why is the m42 different?

Decent headwork, the right cam, throttle bodies, good exhaust manifold and omex.... surely 200bhp is achievable? i know thats a lot of money but the results would be awesome surely. Basically a cheaper s14? I know gearbox and diff choice are equally as important but because of the regs i would have to use the 318is box unless i use the m20 in which case i can use the close ratio sport box.

on the other hand i just cant resist the thought of an m20 on triple webers or bodies. The torque would be awesome too. The 2.7 stroker sounds great too but that would put me in the class with the imprezas so im limited to a capacity up to 2600cc.

People who have gone from m42 to m20 what have you noticed in terms of the difference in handling? does it tend to become a lot more understeery or not?

[DoctorDrift]

Also steering rack will most certainly be changed because even though i have renewed everthing up front i still dont feel connected to the wheels when im driving with the standard rack.

Is the e36 rack really a straight fit? Also just as a thought has anyone tried using an escort quick rack before on an e30? just because they really arent that expensive

[Hoobs]

i still find it hard to understand why the m42 isnt tunable. surely 100bhp/litre should be achievable for most engines and why is the m42 different?

My understanding was it's because the M42 is close to the limit of tuning to start with? It certainly doesn't appear that there is much to be gained from flow work on the head.
Whenever I have spoken to anyone about wanting more power the usual response has been to supercharge it. Maybe it just comes down to costs? I bet there can't be much change from £3.5k for ITB's. cams, Omex and mapping? Much as I like the M42 I just can't justify spending that much when I could get an s14 instead.

With regard to steering feel, what geometry are you running and how hard have you gone on spring rates?

[DanThe]

There is a thread in e30 chat gone up about selling a 2 litre M42 bottom end, all proper parts, just needs putting together and its a steal at £500.

You dont need omex to tune an M42, just somebody that knows what they are doing

[e301988325i]

Also steering rack will most certainly be changed because even though i have renewed everthing up front i still dont feel connected to the wheels when im driving with the standard rack.

Is the e36 rack really a straight fit? Also just as a thought has anyone tried using an escort quick rack before on an e30? just because they really arent that expensive

You'll be wanting the E46 rack part number ending 67, yes they are a fantastic improvement and apart from the hydraulic hose routings are a direct fit. The second hand racks are so cheap there is little point considering an escort rack.

Use M3 (not very expensive) front offset bushes (at the rear of the wishbones) to increase the castor angle which will increase the 'self' centreing effect of the steering and give a better feel.

[DoctorDrift]

Ok so if the m42 has a great flowing head as standard then why is 180bhp not easily achievable? Something doesnt add up, surely with a good exhaust manifold and induction it should piss 100bhp/litre.

I dont want to chuck a load of money at it though and not get anywhere. Plus even with a useable 180bhp i dont think its enough to be very competative in my current class.

The m20 does seem like the best option all things considered especially as its sitting there waiting to be used.

What do you guys know about Griffin Motorsport? a friend of mine said they used to be the guys who knew how to tune the m20 but a quick search didnt generate anything and i dont think they are trading anymore. Do suppose you guys know what sort of spec their engines were?


It terms of steering etc, ive got the m3 bushes and yes they make a great difference but the stadard rack really is utter gash and doesnt inspire any confidence. Sounds like a bit of a pain having to faff around routing the pipe around the e46 rack. Do the standard pipe e30 pipe fittings go into the e46 rack though?

[Hoobs]

Griffin / Dave Isles used to build some quick m20's back in the day and were among the first to offer ECU chips for 2.7's. I can't recall where he is nowadays though.

[rix313]

Griffin / Dave Isles

This is serious, he didn't wear a wig and have a lisp did he?

[buzz6353]

I am sure David Isles has retired
i think his son took over and was tuning vauxhalls for a while

there is not a lot of information around on what they did with the M20s

but they did go well

Les Stannard was another one around at the same time and there is some of his conversions still on the go but just as rare try searching Stannard motors

[Hoobs]

Griffin / Dave Isles

This is serious, he didn't wear a wig and have a lisp did he?

I don't know mate.

[DanThe]

Sounds like a bit of a pain having to faff around routing the pipe around the e46 rack. Do the standard pipe e30 pipe fittings go into the e46 rack though?

I have one set of these custom pipes left if your after 'faff free fitting' -

[rix313]

Griffin / Dave Isles

This is serious, he didn't wear a wig and have a lisp did he?

I don't know mate.

Fair enough, I know it seems random but my motorsport college course leader was called Dave Isles and pretty sure he had an engine company and built BMW engines.

You'll be wanting the E46 rack part number ending 67,.

Are the E46 racks better than the E36 ones?

[e301988325i]

You'll be wanting the E46 rack part number ending 67,.

Are the E46 racks better than the E36 ones?

Plus: Faster ratio, better (more) weighting, they're newer, the E30 coupling fits the splines of the E46 rack. Minus: PAS oil cooler needs to be fitted although some people are ok without.

[DoctorDrift]

The e46 rack sounds great appart from the PAS oil cooler part when you say some people get away without are we talking for road use or race use?

Dan how much are your "no faff pipes?" and, are they designed to go into the m20 PAS pump?

Cheers

[e301988325i]

The e46 rack sounds great appart from the PAS oil cooler part when you say some people get away without are we talking for road use or race use?

Dan how much are your "no faff pipes?" and, are they designed to go into the m20 PAS pump?

Cheers

I get the feeling that you are not very comfortable with modifying your car. This quick rack conversion is literally childs play compared with your target of 220-230bhp from an M20 b25. Do you know what you're getting yourself into?

Linked is a PAS oil cooler, anyone can run the return hose from their steering rack to one end of the cooler, and from the other end of the cooler to the PAS oil bottle?

http://www.ebay.co.uk/itm/BMW-5-SERIES- ... 5ae3551a08

[DanThe]

As above its very easy to link in a cooler, ive yet to check the temp of my PAS fluid when on track even though I keep meaning to

The pipe kit is £100 posted you get both pipes, alloy rack spacers and new sealing washers
M20 spec is the only one I have left!

[HairyScreech]

rec /gs valves do a 43.5mm valve, if your considering head work then a flat 85.5mm piston and heavily worked 731 head may be of benefit. rather than a 2.5 with 885.

an 85.5mm bore will net you a hair under 2.6

[DoctorDrift]

[quote]I get the feeling that you are not very comfortable with modifying your car. This quick rack conversion is literally childs play compared with your target of 220-230bhp from an M20 b25. Do you know what you're getting yourself into? [quote]

To say im not comfortable modifying my car is a bit unfair but i will say im not comfortable with certain things. I dont mind engine work and using parts which are designed to fit but i have no fabrication skills and cant weld etc so making things up is very difficult hence why i would like to get off the shelf bits where if i can. I also have messed around with very custom things in the past and it always leads to ball ache.

As for the m20 is 220-230bhp unrealistic with good induction, 6 branch exhaust manifold, bit of headwork and suitable cam? I know i am an optimist but does that not seem achievable. Thats what the kumho cup guys run roughly isnt it?

[Hoobs]

I did a 2.7, 6 branch, Schrick etc but I never got close to 220. The M52 I have now would have annihilated my old M20. Omex or something would have been the next step but it was all just getting too expensive. I do like the old m20 but I like the m52 better. Just my opinion is all.

[e301988325i]

I get the feeling that you are not very comfortable with modifying your car. This quick rack conversion is literally childs play compared with your target of 220-230bhp from an M20 b25. Do you know what you're getting yourself into?

To say im not comfortable modifying my car is a bit unfair but i will say im not comfortable with certain things. I dont mind engine work and using parts which are designed to fit but i have no fabrication skills and cant weld etc so making things up is very difficult hence why i would like to get off the shelf bits where if i can. I also have messed around with very custom things in the past and it always leads to ball ache.

As for the m20 is 220-230bhp unrealistic with good induction, 6 branch exhaust manifold, bit of headwork and suitable cam? I know i am an optimist but does that not seem achievable. Thats what the kumho cup guys run roughly isnt it?

That's not a dig, just an observation. You kind of appear to contradict yourself. The steering racks need some pipe bending, a bit of patience and anyone is there, or buy a £100 hose kit from DanThe for a direct fit. Fair enough your mechanical experience is what it is, but if you've got the budget to target 200bhp+ with a 2.5L M20 which will definitely require a two thousand pound exhaust system, before you touch the internals can surely not be shocked or worried about a £250-300 inc labour steering rack upgrade?

HTH Alex

Ps) What is your budget?
Pps) I read you have to leave the bottom end stock in another thread, is this correct? otherwise 220-230bhp is not off the cards but still a five grand engine package (inlet, engine, exhaust, management + mapping)

[DoctorDrift]

opinions are all welcome, thanks hoobs. I wouldnt even think twice about going down the m52 route if it wasnt for the class regulations. If i run anything other than an e30 engine i would have to go into the sports libre or rally car class which im not absolutley against but would mean a massive budget and i could never really be competative. so it leaves me with only e30 3 series engines to choose from. s14 is just too much money.

That seems a shame with the mods on your m20 you couldnt get close to 220bhp. What was your torque figure though because that is equally as important isnt it. 2.7 conversion would put me up a class with the roadgoing scoobies so thats a no no really anyway.

but that was with a mapped standard ecu i presume? im thinking webbers possibly?

e3019883250, glad it wasnt a dig it just read a little harsh thats all. Yes i am known to contradict myself but its just my way of working through al the options realy surely you dont need a 2k exhaust system, a good manifold yes but surely the correct diameter straight through would be fine?

In terms of a budget its dificult to say really, obviously i want the best bang for buck as we all do but cant put an exact figure on it. i would say 2-2.5k for the engine really no more at this stage.

Thanks again

[Hoobs]

I've had the same class problem this year with my old M42 powered e21. I was up against much quicker cars in the modified saloons class. It was great fun, just not competitive.

Anyway, having sold the e21, I picked this up yesterday. I'm pretty chuffed as the seats alone cost £1100

http://www.ebay.co.uk/itm/230705492152? ... 868wt_1273

I'm in 2 minds. I either run it as it is or rob it for parts to track prep an M88 powered e30 I'm in the process of securing?

[MrBenn]

Anyway, having sold the e21, I picked this up yesterday. I'm pretty chuffed as the seats alone cost £1100

http://www.ebay.co.uk/itm/230705492152? ... 868wt_1273

Haven't seen that for a while Mark! That's my mates old E30, he built it here at my place while I was building mine. Last time I saw it, it only had one seat and no cage.


Track day at Castle Combe.

[Hoobs]

PM'd

[e301988325i]

im thinking webbers possibly?

e3019883250, glad it wasnt a dig it just read a little harsh thats all. Yes i am known to contradict myself but its just my way of working through al the options realy surely you dont need a 2k exhaust system, a good manifold yes but surely the correct diameter straight through would be fine?

In terms of a budget its dificult to say really, obviously i want the best bang for buck as we all do but cant put an exact figure on it. i would say 2-2.5k for the engine really no more at this stage.

Thanks again

Best bang for buck when tuning an engine to regulations is irrelevant, best bang for buck is a btb manifold and then a stroker crank from an M52.

Honestly with your power target, your budget will cover the head. Billet rockers, cam, uprated springs, new triple angle valves + seats, plus the labour.

Tuning engines is ££££££££££££££££

[DoctorDrift]

best bang for buck when building an engine to regulations isnt irrelevant you are limited in terms of what you can do by the regulations. Thus for me i cant really do anything to the bottom end because then i will be in a class with scoobies. So it seems that without going to a 2.7 bottom end and spending thousands 230ish bhp isnt realistic, thats what i wanted to clarify.

[DanThe]

rec /gs valves do a 43.5mm valve, if your considering head work then a flat 85.5mm piston and heavily worked 731 head may be of benefit. rather than a 2.5 with 885.

an 85.5mm bore will net you a hair under 2.6

This is the way you should be going IMO, get it mapped by somebody that knows what they are doing and you will be getting on for 220bhp easy

[Hoobs]

Paul Sheppard down near Castle Coombe is about as good as you can get.

[e301988325i]

rec /gs valves do a 43.5mm valve, if your considering head work then a flat 85.5mm piston and heavily worked 731 head may be of benefit. rather than a 2.5 with 885.

an 85.5mm bore will net you a hair under 2.6

This is the way you should be going IMO, get it mapped by somebody that knows what they are doing and you will be getting on for 220bhp easy

But he has to keep the bottom end stock @ 2.5L for the intended class, otherwise he'll need 300bhp to compete!

What sort of RPM is an M20 b25 going to need to make 220+bhp? Max power at over 7K revving to 8?

[DanThe]

I read he has to be under 2600cc to stay in class?

[e301988325i]

I read he has to be under 2600cc to stay in class?

On the first post/first page, but. . .

Wow screech what a tread and what diligent work on the flowbench. Respect!

Im very interested to say the least. Due to class regs i will have to stay with my standard bottom end plus some lightening/balancing and a refresh so cant stroke my engine.

A lot of this threads content is pretty complicated to say the least but from what i understand the 885 ports are fine to flow enough for 230ish bhp? but it needs bigger inlet vavles eg 42/43mm as well as a bit of work on the valve seat/guide area?

I have been emailing Rich from fritz bits and he said to not worry about the actual ports but like you have discovered increase the valve size and work the valve seat/guide. Which aslo seems reasonably straightforward for the DIY enthusiast always fancied a go at porting! he also seems to think its the induction which makes or brakes m20 race engine. He reckons with the above mods and webers or throttle bodies i should easily see 230bhp and about 220ish ft/lbs torque!

Does that sound reasonable?

If anything i would like to retain the standard inlet manifold though with standalone management. Earlier you said it should be good enough to flow 250bhp didnt you based on your flow work? If thats the case surely i dont need expensive throttle bodies.

This is very exciting and i hope my excitement isnt clouding my judgment but from my various research/your research.... with not a lot of money for some head mods, a decent cam and standalone management we could see 230bhp/220ish ft/lbs torque?!

So Dr.Drift, which is it stock 2.5 or is bored to just under 2.6L on the cards?

Ps) A smallish capacity 220+bhp M20 would be awesome.

[Hoobs]

What do your regs allow you to do to add lightness? Obviously poly windows would be quite a saving but depends whether they're allowed?

[pistonbroke]

Yes - the Series Production Class A3 regs. dictate any capacity 1800cc > 2600cc; same block & head as production cars, internals incl. valve sizes are free as is normally aspirated induction. So - head work, high comp. pistons, cam & carbs/ TBs are all there to be made the most of, plus remap. IMHO attend to all of these plus an exhaust & lightweight flywheel/ clutch - job done! Simplification in itself.....