as.racing Britcar Production Cup - BMW Z3 1.9L Build

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as-racing
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as.racing Britcar Production Cup - BMW Z3 1.9L Build

Post by as-racing » Wed 06 Feb, 2013 21:02

Evening all,

Thought I'd post the project I'm currently working on, I'm about a year in now and finally have some decent progress worth sharing.

I'm building a car to compete in the 2013/14 UK Britcar Production Cup and try to keep the project updated fairly regularly here: http://www.asracingblog.com

I won't have time to keep this thread regularly updated, so please check out the blog for the latest developments, videos and topics covered in much more detail.

Oh yeah, just had the second weigh in: the car was 1,190kg now 868kg. Over 300kg lost and more to go- I haven't even started with the composites yet!

Cheers,

Andy

Some highlights of the build so far.....

Car at the start of the build:
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Standard 1.9L engine before any changes:
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The big strip!
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Roll Cage going in:
Great job by http://www.tylahmotorsport.co.uk/home
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CAD model finished:
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CFD analysis of standard car:

Open Top vs. Hard Top Analysis (Open Top adds 20% more drag!!)

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Rear wing design:
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FEA of aero loads on rear wing pylons:
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Standard car suspension analysis on a 4-post shaker rig:
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Can't seem to link the youtube videos here? There's more on the blog though...
Follow the Britcar Production Cup BMW Z3 build blog at http://www.asracingblog.com

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Ian_C
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Re: as.racing Britcar Production Cup - BMW Z3 1.9L Build

Post by Ian_C » Wed 06 Feb, 2013 21:47

Great post, I'm subscribed. Looking forward to updates and seeing the zed on circuit in 2013 :thumb:
Current...1998 ///M Coupe
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Previously...1997 Z3 2.8
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as-racing
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Re: as.racing Britcar Production Cup - BMW Z3 1.9L Build

Post by as-racing » Wed 06 Feb, 2013 22:21

Yeah, have decided to stay with the 4 pot, as dictated by the different classes and my budget.

Fortunately the Britcar rules state a maximum power to weight ratio, and as the car will be pretty light I don't need to get much more power out of the engine. I'll definitely be making the following mods though:

Bike carbs (not sure which ones yet)
Homemade carbon trumpets & intake manifold
Some light head work - skim, polish, maybe larger valves, not sure
Megajolt electronic ignition
reprofiled cams

I'm fairly confident the above should get me the power I need. Don't need loads of power, just enough to hit the ratio with the budget I have.

Am also considering M42 forged internals for reliability, but undecided whether or not I'll actually need it.

Any other suggestions? Any BMW OEM parts that would be a good swap with the M44 parts such as lighter flywheels etc???
Follow the Britcar Production Cup BMW Z3 build blog at http://www.asracingblog.com

gookah
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Re: as.racing Britcar Production Cup - BMW Z3 1.9L Build

Post by gookah » Thu 07 Feb, 2013 12:44

as-racing wrote:
Any other suggestions?
I know you are trying to cut down on weight but I would keep the steering wheel ......

Image

Plus remove the door panels and offset them with a seat, unless that is the bucket one you have fitted.. :lol:
Image

Z3 2.8 Progress Journal (Mine)
Z3 1.9 Sport Progress Journal (Wifey's)

I have an element of 'M-styling' on my car, If that's a good enough reason for the manufacturers to adorn a 320 with the M badge, then its certainly a good enough reason for me..

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pingu
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Re: as.racing Britcar Production Cup - BMW Z3 1.9L Build

Post by pingu » Thu 07 Feb, 2013 15:39

Excellent work thus far. All very interesting and as an engineer I understand it. The most relevant thing I saw for us was the location of the brake ducts. I assume BMW have put them where they have for aesthetic purposes and the ease of ducting.

Moving the duct intake from the current position to the centre would also produce a more even pressure profile across the front of the car.

I observe (confirmed by your model) that the Z3 has a very slippy shape. I look at dirty cars and note where the dirtiest patches are - these are where there is turbulence and low speed air flow. The dirtiest patch is in front of the rear wheels behind the door. It really would be scraping the bottom of the barrel, but it is an area for possible improvement.

Lightening internal engine components doesn't significantly affect BHP or torque, but does significantly affect acceleration to the detriment of reliability. I would also balance the engine internals more precisely. For example, BMW balance their pistons +/- 5g, I would aim for +/-1g.

Good luck.
Pingu

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as-racing
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Re: as.racing Britcar Production Cup - BMW Z3 1.9L Build

Post by as-racing » Thu 07 Feb, 2013 20:21

Thanks for the comments so far guys! It's good to get some feedback.

Interesting points Pingu, and yeah I guess their position is primarily for aesthetics. That's not to say though that they're inefficient in this location, but could be even more effective. Is this an area you just have an interest in or do you work in this field?

Again, you're right I know a lightened flywheel won't increase power as such, but it's more for increased throttle response exiting corners. As it is, the car doesn't produce peak power until it's literally bouncing off the limiter! Anything I can do to speed this up will be beneficial, but as you say at the expense of reliability and increased wear. Do you know of any better OEM parts that I should consider for this engine? A bit of machining can be done too at work if necessary. Also, the rods and pistons will be balanced as well when I get around to it, but this will probably be closer to the end of the year.

Cheers,

Andy
Follow the Britcar Production Cup BMW Z3 build blog at http://www.asracingblog.com

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pingu
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Re: as.racing Britcar Production Cup - BMW Z3 1.9L Build

Post by pingu » Thu 07 Feb, 2013 21:45

It's an interest thing nowadays, but once an engineer, always an engineer :D .

I'm not familiar with the 1.9 engine, so can't help there, but there are some good books on how to improve engine efficiency. My favorite was David Vizard's book about the A-Series - the principles apply to all engines.

I'm sure there is plenty of weight to be saved from the suspension and transmission as I think this has been over-designed. The current weakness in this area is the spot welds in the boot floor.

A front strut brace is a common upgrade that you should have as the torsional strength of the car as standard is only around 15-20,000N per degree. Have you measured this? It can be improved at minimal cost, but will require expert analysis to work out the most efficient use of strengthening material.

I will be interested how you decide on the Caster / Camber / Toe measurements as I think that anything other than double wishbone is inherently inefficient.
Pingu

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as-racing
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Re: as.racing Britcar Production Cup - BMW Z3 1.9L Build

Post by as-racing » Thu 07 Feb, 2013 22:25

Haha, yes I got that book a while ago when I used to have my Mini. It's still relevant now, especially all the carb stuff as I'll be designing and making my own carbon inlet manifold and trumpets! What weight saving did you have in mind with the transmission?

Didn't measure the torsional stiffness of the standard car and now the cage is in, so the moment's lost. It's not completely finished though and I want to add more bars especially to pick up the front turrets and link them into the cage. This will be essential for proportioning front/rear lateral weight transfer with the anti-roll bars when it comes to adjusting the under/oversteer balance.

As for kinematics, I won't be allowed to do too much radical to the pick up points, but am planning on doing something similar to the old Group A DTM E30s at the front and have a daft custom rocker idea for the rear!

Am working on bodywork at the moment, but will hopefully really get into the suspension design within the next few months.

Andy
Follow the Britcar Production Cup BMW Z3 build blog at http://www.asracingblog.com

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markrnorton
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Re: as.racing Britcar Production Cup - BMW Z3 1.9L Build

Post by markrnorton » Fri 08 Feb, 2013 14:12

I changed the flywheel when i ran my 1.9. i used a lightened chromolly flywheel from a 3.0 M3 and clutch (fits fine with 1.9 gearbox and actuator arm), plus also fitted the M3 clutch slave cylinder with braided hose.

engine pick up was certainly better, so a reduction in parasitic loss there. also removed the viscous fan and replaced with electric.

strut brace and adjustable roller top mounts made a big difference to steering feel and turn in (with a bit of neg camber)
Still modifying

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as-racing
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Re: as.racing Britcar Production Cup - BMW Z3 1.9L Build

Post by as-racing » Fri 08 Feb, 2013 19:45

Brilliant, cheers. That's exactly the kind of swaps I'm looking for. Will hunt those parts down. Any other ideas?
Follow the Britcar Production Cup BMW Z3 build blog at http://www.asracingblog.com

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pingu
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Re: as.racing Britcar Production Cup - BMW Z3 1.9L Build

Post by pingu » Sat 09 Feb, 2013 03:10

as-racing wrote:What weight saving did you have in mind with the transmission?
Nothing in particular, but like the whole car, I just believe it to be over-designed.

How much weight do you need to remove now, because I would consider cutting holes in the body if you are desperate. When I bought my car it had a 12" woofer in the boot, and there was a 12" hole in the front of the boot...

Image

... so the car can lose serious amounts of metal and still be structurally sound.
Pingu

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markrnorton
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Re: as.racing Britcar Production Cup - BMW Z3 1.9L Build

Post by markrnorton » Sat 09 Feb, 2013 10:57

Other ideas

Try a complete flush and fresh oil in the gearbox and rear diff, plus a friction reducer, like Activ8

internals are good for 300-350hp (turbo's or supercharged)

exhaust manifold and pipe etc I made from scratch, had parts laser cut and tried different exhaust boxes and a race cat. not sure if you need to run a cat ?

big bore throttle body (re-bored) adds a little. but it sounds like you are looking for every gain, like I do. I am building a Ginetta at present just for track use.

good to see an excellent thread like yours

I have pm'd you
Still modifying

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as-racing
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Re: as.racing Britcar Production Cup - BMW Z3 1.9L Build

Post by as-racing » Sat 09 Feb, 2013 12:17

Cheers Mark,

Ginetta build sounds interesting! What are your plans? Have you got a thread running?
Follow the Britcar Production Cup BMW Z3 build blog at http://www.asracingblog.com

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markrnorton
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Re: as.racing Britcar Production Cup - BMW Z3 1.9L Build

Post by markrnorton » Sat 09 Feb, 2013 16:16

Not yet, but I was going to gauge opinion !

big plans ! I have loads to tell already if peeps are interested.

m
Still modifying

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pingu
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Re: as.racing Britcar Production Cup - BMW Z3 1.9L Build

Post by pingu » Sat 09 Feb, 2013 22:56

markrnorton wrote:Not yet, but I was going to gauge opinion !

big plans ! I have loads to tell already if peeps are interested.

m
This peep is interested :) .
Pingu

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markrnorton
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Re: as.racing Britcar Production Cup - BMW Z3 1.9L Build

Post by markrnorton » Mon 11 Feb, 2013 18:25

Can you use Perspex/acrylic windows for the side and rear ?
these make a massive weight saving o have found previously
Still modifying

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as-racing
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Re: as.racing Britcar Production Cup - BMW Z3 1.9L Build

Post by as-racing » Wed 13 Feb, 2013 18:01

markrnorton wrote:Can you use Perspex/acrylic windows for the side and rear ?
these make a massive weight saving o have found previously
Sure can and have already made the templates. Go on then, what's the Ginetta Plan??
Follow the Britcar Production Cup BMW Z3 build blog at http://www.asracingblog.com

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markrnorton
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Re: as.racing Britcar Production Cup - BMW Z3 1.9L Build

Post by markrnorton » Thu 14 Feb, 2013 15:21

as-racing wrote:
markrnorton wrote:Can you use Perspex/acrylic windows for the side and rear ?
these make a massive weight saving o have found previously
Sure can and have already made the templates. Go on then, what's the Ginetta Plan??
Please feel free to read my thread in the performance section
Still modifying

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