Hello all! Building a Z3 Race Car

TMC Motorsport

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Hi everyone,

Thought I would sign up and let you all know that we are nearing completion of our Z3 Race Car build.
The intention is to enter the 750 Motor Club Roadsports Series, which is 45 mintue mini endurance races, the first of which is on May 26th at Snetterton.

I have put a pictorial record of the build so far on our website: http://www.tmcmotorsport.co.uk
The other sections on the site will be updated very soon.

I'd be really interested to hear any comments from people on here, as the Z3 is a new car to us so we're learning rapidly as we go along.

I have a feeling that this and any other forums dedicated to the Z's will be an excellent resource for information and research for us, so expect plenty of questions from me in the future!

Cheers all,
Matt
 

swamper

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how do Matt ...I will be watching with interest.
what problems have you come across up to yet?.....apart from the weight lol
 

TMC Motorsport

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The weight has been a major focus so far. We've got it down to about 1100kg without me in the drivers seat, so its going in the right direction. I have a friend who is very good with fibreglass moulds, so the intention is to take even more weight out of the bodywork.
Other than a few mild misdemeanours (such as drilling through the fuel filter when putting the extinguisher system in) its been relatively easy so far, but I'm sure the first time on track will show up some gremlins that need to be ironed out.
 

GazHyde

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Welcome Matt, what a nice little build you have going on!

Can't wait to see more updates and pictures...

I was a little intrigued when you signed up, as your website was clearly under construction the same as your car ;)

Gary
 

Aceman

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Hi Matt

Looks like a great build project on its own. Have you sorted the boot welds out and strengthen them too, also I notice you have the M52TU engine are you allowed to modify it much if so have you considered doing the M54 manifold conversion which should gain you an easy 40bhp with exhaust and remap too.?

Keep us informed of your progress on the car and also the racing. I think maybe a meet at one of the race days to support you would go down well and be a good day out. Are you racing at Cadwell at some point in the year?
 

Mr-P

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Welcome to the forum and I am glad to see someone using the car in anger and it not being a garage queen:):) .
Good luck with the racing.

Can you send me the dates you will be at Combe and I will try and pop over.
 

TMC Motorsport

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I'll be honest, I didn't realise there was a weakness in the boot. What should I be looking for?
The inlet manifold conversion is something I'm keen to get sorted. We've changed the filter and arranged a cold air feed, so the manifold and throttle body is the next step. Does anyone know a decent source of a complete kit?

I don't think Cadwell is on the schedule unfortunately. We might do a few extra races at Combe though. I'll put the calendar up on the website tomorrow evening. It would be great to meet anyone who would like to support so I'll do my best to keep things up to date.
 

Aceman

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There are plenty of tales around the net about the boot welds but basically the entire boot floor was only spot welded by BMW in the factory and not enough spot welds were done to cope with the stresses exhibited through the diff etc. If you have a look in your boot and remove all the carpets etc. which I am sure you have already done for weight saving you will be able to see the spotwelds on the floor. Inspect them all and if any appear to be slightly rusty they have failed, look especially at the ones on the left hand side which are under seam sealer so the angle grinder has to come out and remove this. The solution is to drill out all the spot welds and flood weld them giving a stronger bond but also from underneath the car clean up all the seams with the angle grinder and seam weld it all adding extra strength. Also inspect the diff hanger bracket which is also prone to cracking again seam welding this to the cross member beam and not relying on the sport welds is a good preventative measure. Another tip is to add strength to the arb mounts by seam welding them and also weld a small triangular piece to the wishbone where the arb mounts.

If you want to go to the extreme Randy Forbes in the states does a kit that adds extra strengthning pieces and utilises a modified diff cover using a twin eared mount, this is what is detailed in the link Hardtop has posted above.
 

TMC Motorsport

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Thanks very much for the information.
We have put extra strength into the diff mount, and have got bracing over the boot area as it will take the downforce generated by the not-inconsequential rear wing, however I dont think any extra welding has gone into the existing joints. We have actually cut out the boot floor to re-route the exhaust so the silencer now comes out from the boot lid, and this warranted extra strengthening to make up for it. I will give it another once over as well though.

As for the inlet manifold, is there an off-the-shelf kit available or is it a case of putting something together from parts? We're not afraid of a little fabrication, but obviously I know its a regular mod, so getting the proven method is always preferable. Also, how configurable is the standard ECU? I know some manufacturers dont like you playing around with the factory settings. Is this the case with the Z3 or will we be able to find a bit more from it on a dyno?

We've booked a rolling road session for next Monday, and all being well it will hit the track for the first time on Friday 24th at Snetterton. If that goes well the first race will be the same weekend on the Sunday. Very much looking forward to it!
 

Aceman

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I believe CA Automotive do a package of everything you need to do the manifold conversion but it isn't cheap.

Sounds like you may have the boot welds covered by your description but worth checking all the same.

As with all remapping if you have done mods elsewhere like exhaust and induction then you are only going to get best gains from a RR remap or somebody experienced enough to do it on the fly driving down the road. Have a chat with your RR guy when you take it in I am sure they will be able to offer something.
 

Aceman

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Shame can't make Saturday would have loved to have come along, it has been years since I was last at Mallory funnily enough that was a 750 Motor Club weekend too when I was supporting a mate who was racing at the time.
 

Lewy

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Good thread so far buddy, hope to see some pics soon :)

If you come across a decent m50 manifold conversion kit I'd be interested to know, there's some right shoddy jobs out there!
 

TMC Motorsport

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Update from the weekend and today at the rolling road.

We ran the car for two 15 minute sessions at Mallory, ran the brakes in and checked everything seemed to be ok. After the first session my biggest complaint was the steering wheel being slightly off centre! Pushed a bit harder in the second and it became evident a full setup was needed, but generally no complaints at all.
On Sunday we had it on the corner weight scales and set the camber, castor and toe and then today took it to Circuit Motors at Castle Combe for a rolling road session.

Considering all we have done is given it a cold air feed, change the air filter and exhaust silencer, I'm rather pleased with 198.5bhp @ 6450rpm and 201lb/ft @3400rpm. It showed about 15% losses through the transmission, giving an approximate 170bhp at the rear wheels.
Next up is to remove the cats as pre '99 cars dont need them under MSA regulations, and change the inlet manifold. It will then go for a remap and we are hoping to see around 240bhp at the flywheel.

We're racing this weekend at Snetterton, with a full day testing to get a decent setup sorted on Friday, and a 45 minute race with a pit stop on Sunday. If anyone is in the Norfolk area, let me know, I have a few spare tickets!

I've got some decent photos from the weekend with it on track, which I'll try to get some examples of when my laptop isn't having a crisis!
 

GazHyde

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I may have to borrow one of those for the Facebook page cover if you don't mind. Will put your logo on it for a bit of extra publicity as well!

:rally:
 
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