M42 on R1 bike carbs - now running

[Brian28]

Edit - Thread title changed to what I've decided to do. Everything else below as originally posted.

Has anybody done it? I have an M42 that isn't giving anything like enough power to be competitive (153 flywheel). Has had a bottom end refresh and balance, head skim and 3 angle valve job, flywheel lightened max possible, ECU chipped with a remap done on the dyno. Full service etc including recon injectors, so nothing more to come without spending more.

The next step would be different cams and gas flowed head. Somebody mentioned earlier on today that something like twin 40 webbers and stand alone engine management may give better results for the money. Anybody had a go at this, or come across any useful links etc? Will liely run with what I have for the rest of this season, but would like to get something done for next season.

Cheers
Brian

[rix313]

Some one on here was selling some ITB's if that's of interest? Pzero I think it is.

Good luck

[Brian28]

Thanks, regs allow carbs but not throttle bodies. They are also pretty much free for top end (expensive) tuning but don't allow the M44 block which would be a cheap and easy way to a bit more power, so despite running in a 2 litre class I'm stuck with 1800cc .

Have tried google etc, but can't find out much info.

[e21Jason]

Carbs with mappable spark would not be better than stand alone with a custom inlet plenum with a single big throttle if you can run that

m42 webber manifold is about £150

Jason

[GeoffBob]

The next step would be different cams and gas flowed head. Somebody mentioned earlier on today that something like twin 40 webbers and stand alone engine management may give better results for the money. Anybody had a go at this, or come across any useful links etc? Will liely run with what I have for the rest of this season, but would like to get something done for next season.

Brian,

Without increasing the mass of air inducted into your engine per stroke, changing your method of fueling your engine will have little or no effect. TB's for example, improve power by virtue of the fact that they replace your inlet manifold, and hence improve the engines ability to breath (improve the engines volumetric efficiency, VE) and thus allow the engine to induct a greater mass of air, per stroke, at certain RPM.

Improving the VE is the chief mechanism to improve the power output of a normally aspirated engine. Changes to the exhaust , inlet, valves, cams etc. relate to improving the VE. Improving the ability of the engine to induct air by improving VE means that more fuel can be burned with that air, thus producing more power. It is highly unlikely that fitting a carburettor to an existing (or similar) inlet manifold will do anything to improve your engines power output since it will not improve your engines VE (if anything it will worsen it). If your regulations permit, you would do better to look at flowing the head and improving the cams. Likewise, as Jason said, a custom inlet manifold (single throttle, plenum chamber and header tubes) will, due to improved VE, do more for you than fitting a carburettor.

[Brian28]

Thanks chaps. Has anybody got any links or info specific to the M42 for ideas? Having looked at the price of Webers, I'm thinking of perhaps bike carbs instead as they are relatively cheap and plentiful. Geoff the idea would be custom/aftermarket manifold rather than try and stick a carb on the original manifold. I'm sure somebody must have done something with the M42 and have power outputs, but an hour with google hasn't really turned up anything useful. I'll only have something like £500 to £1000 which isn't going to go far, also means I can only afford to do it once so has to be the right call first time. It also has to be worthwhile doing, ie if I'm spending a grand for an extra ten brake or so then to me it probably isn't worth doing as I'd still be getting my ar*e kicked.
Cheers
Brian

[e21Jason]

With your budget I would go with cams, change the trottle body to larger single type and a live remap

look on the metric mechanic web site or m42club.com

Jason

[Brian28]

Thanks Jason

[DHFiS]

You have an M42 producing 153 bhp and you want more than 10 bhp more for less than £1000?

[Brian28]

I want to know if its possible, yes. At the RR day a few months back (albeit a different RR) two fairly standard 318is' made similar power with an off the shelf chip so 153 isn't that impressive. So in your experience how much does/did the various M42 top end upgrades cost relative to any power increase?

Most stuff that I've found from people that have tuned an M42 relates to bore/stroke increases or forced induction, so doesn't really help.

[DHFiS]

Have you thought about Schrick cams? £580 from CA Automotive.

[Brian28]

Good link thanks, and looks like they are just up the road. I think I used "carbs" in the google searches, as neither CA nor Metric Mechanic turned up on google which was odd. Useful stuff on both sites, I fancy a go at the MM pulsed manifold with a scrap one if I can find some better photos. Looks like all four are the same length rather than tuned length, so should be simple enough to knock something up.

[DHFiS]

Good link thanks, and looks like they are just up the road. I think I used "carbs" in the google searches, as neither CA nor Metric Mechanic turned up on google which was odd. Useful stuff on both sites, I fancy a go at the MM pulsed manifold with a scrap one if I can find some better photos. Looks like all four are the same length rather than tuned length, so should be simple enough to knock something up.

I would be interested to know how you get on.

[Brian28]

I'm planning to have a gas with a few people at Thruxton in a couple of weeks. Two guys who have swapped from injection to carbs (2.7 E30 and a 16v Golf) plus a guy who used to tune the 318is back in the day. (He is seventy-odd and still races, really nice chap)

Will just be comparing options and racing the car as it is this season, then engine work over winter for next season.

[tez180]

Fritz bitz have a pretty snazzy new manifold and full exhaust combo that get a you a few more BHP. Might be worth checking that out

[ade36]

I was contemplating going down the carb route so let me know if you find out anything...

[theduck]

Am I right in thinking that this would be simpler on an M40? This is something I am considering and my car runs an M40 engine. Cars actually an E34 518 but was pointed in the direction of this thread by rix313 as I was looking at twin 45s/bike carbs as a simpler alternative to ITBs.

[Brian28]

Hi, some photos of an M40 with carbs fitted on this link I got on google searching for M42 info, still haven't come across an M42 on carbs but I'm sure it must have been done by somebody somewhere.

http://retrorides.proboards.com/index.c ... read=24996

Cheers
Brian

[Brian28]

Five months on and I've not uncovered a single M42 on carbs (or anything else really on top end only tuning), so pretty sure nobody has done one. I have a scrapper available this week so mocked up a set of R1 bike carbs on it with bits from a couple of old stat housings and water pipes. They wouldn't work as a single bank of carbs as the manifold bends would be too extreme and different lengths, if seperated into two pairs of carbs by about 3cm they should work. I've given a mate in engineering an old inlet gasket as a pattern for a manifold flange, hopefully he can knock something up in stainless. Then its a case of forming stainless pipe from circular at the carb end to oval shape at the inlet port end. This will be combined with cams and then see what the rolling road says after a set up.

[kingludba]

Looking good Brian, cant wait to convert my touring.

[rix313]

Looks good, what sort of gains are you hoping for?

[Brian28]

Gains are just guesswork at the moment to be honest. After speaking to Ant at A Tech I need to organise something for ignition timing advance, as the ECU usually used the AFM inputs. I've emailed Paul to see if he can use the R1 carb TPS as a dummy engine load input to a Unichip piggy back ECU to advance the ignition timing under load. Ant is speccing/pricing cams. I'd hope for somewhere around 15 brake more. I fitted a pipercross sealed cone filter type affair, other than that the car was the same, but when I tried it on the rollers a couple of months ago it had lost six brake, so hoping that was just air flow. Would like to get it to 170ish with everything done.

[Brian28]

Arse. I got the manifold runners made up in stainless, quite a few hours fettling to get them pretty close ready for tig welding to the flange. Mate dropped the flange off last night, did a lovely job but it's in alloy not stainless. So now need to find some alloy tubing in the right size and start over again with the runners

[Brian28]

It's now running on the bike carbs. Everything just rigged up temporarily to check that it will work, will be taken apart and rebuilt properly in the next week or two, throttle and choke cables sorted, then after that Unichip added for timing advance and RR session. Has reground 272 degree cams and will have a custom exhaust manifold fitted, otherwise all standard spec as above.

Fuel feed is a bike petrol pump attached to the original fuel return line as the end of the steel return pipe sits more or less at the bottom of the petrol tank. Original E30 high pressure injection fuel pump disconnected. Small inline filter. Yamaha R1 bike carbs, 185 main jets fitted as a near enough guess for now.

[DHFiS]

Dyno print will be very interesting.

[richlyons]

185 main jets? i ran 170's on my 1.8 16v corrado on keihen carbs. didnt know that r1 carbs would need that size jet, whats the choke size? 45mm?

what engine management are you using? im wanting to do this soon

[Brian28]

40mm chokes. Work has been mad the last couple of months so I've not had a chance to get this finished off yet. The jet size is a guesstimate, its for a race car so will be on full chat for longer than a road car. The issue with the conversion is ignition timing advance. The engine load sensors that the ECU uses are done away with, so you will only have the same ignition advance as the car has at tickover. I'll be using a UnichipQ (piggy back tunable ECU) with the standard engine management. The R1 TPS will be spliced in to act as a dummy engine load feed to advance the timing. The chap who is getting this organised (Paul Sheperd @ Circuit Motors) has an electronics problem with his dyno at present (or at least did last month), so won't know for sure how everything will work until it goes on the dyno. Entered for Brands next BH weekend so I'll need to get a wriggle on with it now.

Why are you thinking of carbs and not bike TBs? ITBs are very similar work to fit, cheaper to buy (a lot of bikes from the last 5-10 years use TBs), and a much more accurate tuning package when you are finished so pretty much better all round.

[Gunni]

more accurate tuning package?

With ITB´s you could have used the stock fuel system and tuned that to work with a piggyback.

[Brian28]

I know, but race regs allow carbs, not ITBs.

[Brian28]

Didn't make Brands (family), dyno booked for early next week so will know the scores on the doors then.

[Hoobs]

Any news on this?

[Brian28]

Another project done, but not quite done, and gets the bullet. Chap at the RR had a shoulder injury at the time, so wasn't able to fit the UnichipQ piggyback. Rejetted to 195 main jets as it was running lean, power 155 to 160. Tried a few things to see if it made a difference (closing some of the loom open loops from AFM, TPS, ICV, crossing various wires over, sending 5v/12v down different returns to the ECU to try and imitate what the ECU would be seeing as full engine load etc) but didn't have a timing light to look at ignition timing so it was mostly guesswork and trial and error (try the grey wire, how about the red one etc etc). The chap with the laptop and software to do a live chip remap was away on holiday, so we couldn't look at and/or adjust the ignition timing via a laptop. Even with the piggyback it's unlikely that it would achieve 5/10 brake more, so has got to the stage of throwing good money after bad. I'm jumping on the bandwagon and going six pot. The car drives quite well as is, good throttle response etc, so as a road/track car it'd be really good. Just not competitive in the class I race in though, so a reluctant swap to a six pot for next season.

[Tonyy93]

overall how much has the project cost and are the gains worth it? thinking about doing this to my i.s
cheers tony

[Brian28]

Somewhere over 3k overall, but that includes a lot on standard engine rebuild parts and machining that you wouldn't be doing if you were just doing the upgrades without an engine build. I was really compromised because of building to race series regs, you could put together a much better package if you didn't have to stick to those. I'll be stripping the engine down and selling the parts in a month or two when I can clear a bit of garage space to get the car in.

If you really want to notice a difference, then put a second engine together in spare time and change everything at the same time when it is ready. If you change all of the bits incrementally you won't notice such a big difference, as it's only 20 brake or so altogether with everything contributing a bit of that.