Sunday, 30 September 2012


I finally got round to replacing the tatty old BMW wheels with some shiny forged magnesium wheels. They weigh less than 5 kg per wheel and look super. Unfortunately, they're not BMW fitment, so I have to use an adaptor which pushes the wheel out by an additional 35 mm and adds about 1 kg / corner back on - but the weight saving is still around 3 kg per corner which is well worth having. New brackets for the cycle wings will be needed at the front to keep the cycle wings central over the wheels - at the moment the wheels stick out quite a bit which looks a bit silly.

Last Saturday I managed another track outing, happily with no engine or other failures, bringing the failure-rate down to one engine per track day. Hopefully I can take that as a sign that engine #3 is a good 'un.

Waiting for the green light. Note appropriate race number.

The track outing took the form of a sprint - a very tight twisty track, doing timed runs against the clock, one car at a time.

Engine not exploding. Result.
Note cycle wings not centred over front wheels.

The car performed very well, although it became clear that the springs were a bit on the soft side. The extra track width doesn't help as this means the wheels have more leverage to compress the springs. So after a bit of educated guesswork, I had a guess at a new spring rate for the front and stuck some stiffer springs on, which has greatly improved things. The dampers can be wound back a bit as they're no longer needed to try and stiffen the ride, so they are able to control the springs better which gives a less chattery ride. Having stiffer springs at the front has also improved the front-back grip balance so the car can now be made to understeer, rather than going straight to oversteer when feeding in the power. Less entertaining but probably faster. Turn-in feels a bit sharper which is an improvement.

However, this has highlighted the fact that the rears are now more than a bit soft... so they are next on the list. Turn-in at the moment is a bit of a two-stage process - the front turns in quite neatly, and then shortly afterwards the back settles itself into position with a general lack of urgency. As a starting point I may try putting the old front springs on the back and see how that feels.

I suspect an ARB at the front will improve matters further, perhaps a winter project for after the rear spring rates are sorted.

Simon having a go. Despite being used to very forgiving 4wd rally cars, he very kindly neither crashed nor humiliated me on time (he was slower in the morning, quicker in the afternoon).
Note excessive body roll on the old springs.

Now that my major concerns with the car are worrying about suspension setup and adjusting spring rates, it seems that mechanical reliability and basic build stuff is more or less there. Not that there isn't lots I want to do still (front anti-roll bar, make a nicer looking dash, redo some untidy bits of vinyl wrap, data logger, etc, etc), but this is all nice-to-have stuff.

So this is probably a good point to put the build blog to bed. It's been a good experience. Lots of things I'd do differently next time, but that's to be expected really. Looking forward to lots more track days in it, and fewer exploding engines.

Saturday, 14 July 2012

Spinning at Blyton

On further inspection the first main bearing from engine #2 that I looked at (adjacent to the failed big end if I remember rightly) turned out to be ruined. This means that it would be crank out to fix, which would make a regrind a no-brainer, plus big-end and main shells, full strip and engine flush, etc. Doing the sums suggested that I could very easily spend £1k or more fixing a £1500 engine, or replace it and sell some of the bits to make up the difference. The latter seemed like an easier, more reliable and more cost effective option, so that's the route I took.

Main bearing from engine #2.

Eventually I found an engine via Ebay, and the seller offered to knock £150 off if I bought it without going through Ebay to avoid fees... and Ebay buyer protection. Obviously I said yes and took the risk, on the grounds that I have no faith at all in Ebay's buyer protection scheme. The engine showed up promptly, although it was pretty clear that the seller's claims of driving the engine for a few months were lies - since several of the intake hoses were completely perished, I doubt it would have run at all. It was also covered in oil from various leaks. This was a bit more lying than I had anticipated from the seller (I'd expected a bit), but still, none of this is very serious, so I got it on a stand and cracked it open.

"Yeah mate, it runs really smoothly"

"No oil leaks, breaks my heart to sell it, really does"

Happily, I found more or less what I expected when I looked at the big ends - a considerable amount of normal wear on the bearings, but no sign of serious problems and (almost) no crank marks. Similarly, the mains were basically perfect (they take much less load so this is to be expected).

The only exception was big-end #1 which had a slight scratch on the crank. I umed and ahed for a while on this one but eventually decided that since the scratch was barely detectable with a fingernail, and ran straight down the centre of the bearing, there was no path for the oil to escape without building pressure and floating the crank as it's supposed to, and that it ought to really be harmless. Time will tell I suppose, but certainly there was no evidence of knocking or anything like that - the oil that came out was black but free of debris, and the corresponding bearing was worn but not excessively, and not more than any of the others. So my reading is that this has been there for a while without causing a problem.

I plastigauged a few bearings and found them to be bang in the middle of spec, which was reassuring. So I put it back together with new big-end bearings (I'd have to remove the crank to do the mains and I didn't really see the point as these looked fine and never go wrong anyway) and stronger-than-standard ARP big-end bolts (most expensive bolts I've ever bought at £8 a bolt with a total of 12 bolts).

Slightly scratched big-end.

Mains look fine.

Big end cap - no serious wear. Fractured rods, very fancy. Grass needs a cut though.

Engine on stand and crane, just in case. Good thing actually as I didn't put the stand together properly - it didn't fail but it easily could have.

Engine on stand.

Another big end bearing looking fine.

So without further ado I put it back together with new big-end bearings and main and big-end bolts and stuck it in the car, although not without replacing the flywheel with a lightened single-mass flywheel (more on this in a bit), on the grounds that if I'm going to all the effort of replacing the engine, I should at least try to improve it in some way (in addition to making it work). The flywheel was a pain in itself - I was told that standard bolts would be fine, but they turned out to be much too long for the thinner flywheel. E30 bolts didn't work as they were too short (they engaged about three threads, which I felt was a bit marginal). So in the end I bought some new E36 bolts and got them cut down by the difference in thickness, which I'm sure will do the job.

On first start I was greeted by... an awful clanking noise. I considered phoning a scrap dealer and getting them to take the car away forever but after a couple of hours of investigation and research, finally identified the cause: the engine was sat slightly differently and was touching the chassis. I got the hacksaw out and removed the offending part, and all was well. It built oil pressure without much issue, thanks to packing the pump with vaseline (there was a slight issue as the pickup pipe is held by a bracket on one of the main cap screws - when I put the main cap back the bracket moved slightly, which meant that I struggled to get the pipe right. Next time I'll put the caps on with the pump in place).

Over the next few weeks I gave it some test runs, gently building up to max revs and changing the oil a few times. Each time nothing very bad came out, and no nasty surprises occurred. However, I do regret not changing the clutch - the standard M3 clutch is unsprung, because the dual-mass flywheel absorbs vibrations. My single-mass lightened flywheel doesn't do this, so using it with a standard clutch is, I think, a mistake. At some point I need to take the engine out and replace the clutch with a sprung clutch from an M5. It's quite a lot of effort though so I'm ignoring it for now; perhaps a job for the winter.

Last weekend it got it's second track outing, this time at Blyton Park. It performed well up until lunchtime, when the heavens opened and didn't stop until the evening. I took it out anyway in the afternoon, but I can't honestly say it was particularly enjoyable, especially when the front brakes stopped working. I've since replaced the front master cylinder and will see how that goes tomorrow. Despite the missing front brakes, however, I only managed one spin in the wet, narrowly avoiding a haybale and emerging unscathed.

For once, the breakdown on the way home wasn't me (Ben's rear brake calliper fell off the Atom). A relatively painless track outing then, if spoiled a bit by the rain. Current tally: 1.5 engines per track day.

Tuesday, 24 April 2012

Spinning at Bedford

A few weeks ago I took the 7 out to Bedford to see how it performed on the track. Preparation consisted of borrowing Ben's garage (thanks Ben) to try and get the suspension set up reasonably accurately - I think I did an OK job, but regret not corner-weighting it - maybe a job for the future, or maybe for a professional. I'm not sure how accurately I'd be able to do that at home.

I'm happy to say that performance was excellent. Cornering grip, even on cheapish T1Rs, was very good - I was surprised at how much better it was through the corners than many of the other cars there. Straight line speed was no real surprise - it was excellent, obviously, and even on the main straight (and through the corners, when I got the lines right) it proved able to stay with a Porsche GT3 RS, which isn't bad for something I bodged together in my garage. Top marks to the GKD design there. Braking was strong, but under very heavy braking it seemed to lock the front left much sooner than the front right (and then veer quite hard to the right) which I'm attributing to the lack of corner-weighting. Steering was on the heavy side; I suppose the weight of the big engine doesn't help here. I guess it'll be an on going task to try and figure out a way to improve that, maybe using rose joints instead of ball joints up front, perhaps a change of steering rack? I think less rear toe might improve turn in, but there's a balance to be struck there with cornering stability. Overall I'm really impressed with how it performed and look forward to seeing how performance improves with a corner-weighting, and perhaps better tyres.

Unfortunately there were two spins. The first was harmless, due to an ill-judged mid-corner gear change that unsettled the car and left me looking backwards down the track at a Boxster bearing down on me at 70 mph; the second wasn't so good.

The second spin looks more expensive. The first sign was a knocking noise...

Expensive noise.

Unfortunately at the time I attributed this to a loose exhaust silencer and carried on, but realised at the end of the day that it was coming from the engine. Further investigation and sump removal revealed that it had spun a big-end shell:
The spun bearing (number 6).

The spun bearing dissolved itself in the oil.

And left some parts of itself attached to the crank.

 The hope is that the crank will clean up in-situ, and then a fresh set of big-end bearings and a few oil changes should get it back to full health fairly quickly and cheaply. If the crank damage proves more extensive then it's engine out to remove the crank for a regrind, at which point the time and money cost will start to stack up...

Whilst investigating I also discovered that the idiot who previously worked on the engine has shimmed the intake valves to the same spec as the exhaust valves, so this will need fixing too. Not a massive or expensive job, but irritating nonetheless.

Hopefully the car will be back on the road soon - it really depends on what I find as I inspect the crank.

I would recommend other builders using the BMW straight 6 to refresh their big-end bearings and use upgraded (ARP) bolts. Apparently the big-end bearings are a known weakness in these engines, especially when driven hard as they will be in these cars. If done preventatively it should only be a few hours and around £150... if done after spinning a shell it could be a lot more if a crank regrind is required.

Sunday, 18 March 2012

Tidying up the dash a bit

While browsing Ebay recently, I managed to score a cheap oil pressure gauge. This is something I've felt I should fit for a while, as it would be nice to have early warning of low oil pressure, should something go wrong. Unfortunately, there was no space on my dash for it. I wasn't particularly happy with the way the traction control just sort of hung awkwardly off the bottom of the scuttle so figured I'd make a little centre console bit.
Traction control hanging a bit shoddily off the bottom of the scuttle.

After a lot of fiddling around, I ended up with this. It's not perfect (slightly too wide at the bottom) but it's a big improvement.

Oil pressure gauge mounted.

When the sender adapter arrives I'll plumb it into the engine.

Meanwhile, I've also been dismantling the VANOS. The idle is a little bit rough, and I can't find any intake or exhaust leaks to explain this. So I tried unplugging the VANOS while it was idling, and noticed no change in the engine note at all (the VANOS should be adjusting the timing at idle, so normally unplugging it would make the idle get quite a bit rougher), which suggests that it's not doing anything.

Vanos solenoid.

The VANOS seals look OK-ish, and the solenoids all have about the right resistance, and click when I apply 12v to them, so it's not totally clear if they're working or not. I've ordered a replacement set of seals anyway and will see if that makes a difference.

Sunday, 11 March 2012

MOT... passed?

After the MOT failure I took the car to a garage and asked them to take a look at the emissions, on the grounds that they have tools for analysing the exhaust gas so they'll be better able to tell what affects emissions. This sort of worked. They found that by unplugging the MAF, the car will run on a more basic fuelling map that's good enough to get through MOT. So I now have an MOT but still don't really know what's wrong with the car (although it does at least rule out things like excess fuel pressure, or poorly seating valves, etc, and point towards a problem with running closed loop). Given that they haven't actually done anything to the car or identified the issue, this feels very close to a bribe, but an MOT pass is a pass, so I'm not complaining.

More fiddling about on the intake side this time revealed a perished hose leading to the EGR valve (which I'm not using), so I removed this and blocked it off properly in case it was causing an intake leak. I'm not sure this has helped, though I may go back and get them to check the emissions again.

They also pointed out that the wheel alignment was very poor, no big surprise as I haven't done the front end since replacing the wishbones. Perhaps a job for this afternoon.

Wednesday, 29 February 2012


I took the car for an MOT on Friday, but it failed due to emissions (not a total shock, but still disappointing), and headlight position. Apparently one headlight is a few mm lower than the other, which is No Good, despite passing IVA and the last MOT. Easily fixed with a spacer though. Emissions are more tricky.

Emissions are all good, except for lambda (air/fuel ratio) which was 1.2, i.e. pretty far off (20% too much oxygen present, though I suspect 1.2 was the limit of the analyser they were using and in fact it was even worse than this). In a perfect world the oxygen and fuel would balance in exactly the right ratio and all the oxygen would be used up burning the fuel to produce CO2.

In my world, however, the prime suspect is an exhaust leak upstream of the lambda sensors, which would explain (a) the excess oxygen as the exhaust flow draws in more air and (b) the rubbish fuel economy as the lambdas detect the oxygen and compensate with extra fuel. Presumably the cat is then using the excess oxygen to burn the excess fuel and hence I'm seeing normal HC (unburned fuel) levels at the tailpipe, which will be rapidly destroying the cat.

After looking for an exhaust leak and not finding one, I took the exhaust apart in search of more evidence, and eventually found this where the primaries join the block:

Exhaust gaskets. Note scorch marks at top left.

Which looks like pretty solid evidence of a leak. I've ordered new gaskets (these are off the old 328 engine and are slightly different to the M3 gaskets, which can't help), and booked a retest. They said they'd "make sure it passes" next time, which is nice of them, but I'd quite like to actually fix the problem.

Saturday, 18 February 2012

Lack of progress

Not a lot to say this time round: the front suspension is, finally, all back together, tightened, etc and ready to go. Thanks to Ben for coming round to help me bleed the brakes.

Unfortunately the car's due an MOT so no road testing until that's done... and given the weather at the moment, that hasn't happened this weekend. It will have to wait for a dry day. In the mean time, the windscreen is off (it would fail due to the lack of wipers), and the centre mirror and front numberplate are on in readiness for the MOT. Given that I always tend to drive in a helmet anyway, I'm debating leaving the windscreen off. Might see how that one goes.

In the meantime I got on with some garage upgrades: the garage now features 1700 W of lighting, which also contributes significantly to making it warmer, and may help stop me hitting my fingers with a hammer so often.

And the search for decent wheels continues. The main problem seems to be that BMW owners tend to go for big (heavy) wheels - even on race cars, no one uses 15" because they're all running big brake kits. So finding some lightweight 15" wheels is proving difficult. Team Dynamics seem to be about the only option at the moment, which is not very exciting (or especially lightweight). Keeping my eyes open for some Dymags but not holding my breath as these seem kind of rare.