Welcome to our BMW E30 based Marlin Sportster Build Site,
we hope you will find this documentation interesting and helpful.
The site has grown massively since its inception in 2005, I hope to one day soon improve the navigation as it's a bit overwhelming to start with. The main areas of interest to builders will be:
The rolling chassis build
Bodywork Fitting
SVA Issues
Final Assembly
If you would like read about the build in date order then have a look at his page.
It took 2.5 years to build the car and pass SVA and a lot longer to get to where it is now! To see the Sportster out on the road have a look at one of the videos here.
During 2008 we rebuilt the BMW engine from 2.5 to a 2.8 creating an M20B28 stroker engine. It uses the crankshaft from the later BMW M52B28 and the conrods from the M20B20. Not much more work is needed other than a clean up, slotting those bits together and a crank spacer. To read about the engine build click here (very picture heavy!)
Finally in March 2009 it was painted, a full set of images is here.
To read the whole build from the start click here.
21/01/2007
Exhaust Wrap, Idle Issues and db plugs
Forgot the camera today - oops! Nothing that interesting to see really. Started wrapping the manifold - what horrible task. Fibreglass everywhere and not that easy getting it round all the pipes! Then we ran out of wrap with one pipe to go, will have order some more!
Second issue of the day more idle problem hunting. Took the TPS (throttle position sensor) off the throttle body today. It was quite badly gunked up with oil so that got a good clean out and a check with the multimeter - everything looks good but the engine is still idling between 1000 and 1100 rpm. Bummer! Not sure what to try next as we're try replacing all the main components that will normally cause idle problems on an M20.
Finally found a use for the DB plugs that works! They can just about be squeezed into the openings for the tail pipes in the Magnaflow boxes! This works quite well in reducing the noise and can be pulled out again. I should think we'll be OK for SVA with a the boxes bunged up.
Second issue of the day more idle problem hunting. Took the TPS (throttle position sensor) off the throttle body today. It was quite badly gunked up with oil so that got a good clean out and a check with the multimeter - everything looks good but the engine is still idling between 1000 and 1100 rpm. Bummer! Not sure what to try next as we're try replacing all the main components that will normally cause idle problems on an M20.
Finally found a use for the DB plugs that works! They can just about be squeezed into the openings for the tail pipes in the Magnaflow boxes! This works quite well in reducing the noise and can be pulled out again. I should think we'll be OK for SVA with a the boxes bunged up.
14/01/2007
Noise Test
Done more testing outside and its a lot better out there. If you stand
back on idle its not bad at all. Were not going to add any extra
mufflers, but possibly do the brillo pad trick for SVA and block two of
the exits. Might see if we can do something to quieten the intake as
well.
Forgot the db meter though so another excuse to run the engine next weekend :)
Forgot the db meter though so another excuse to run the engine next weekend :)
13/01/2007
Brakes and noise
Possible solution for reduced brake travel due to fitting the BMW master cylinder with adapter plate:
Seems ok from a dry run without fluid or servo. Full test will have to wait until I've put fluid back in the system. Going to need to glue this in place some how, probably with silicone sealer. Given the shroud (?) is so big on the BMW master cylinder I can see this ever falling out, but it could reposition depending on the speed at white the piston retracts when you lift your foot off the brake.
Refitted the tank today with rubber strips and added two additional exhaust hangers just behind the seats. That makes 4 hangers at the back and the one on the gearbox which should be enough fail safes if any of them go.
There should be more than enough room between the tank and the mufflers now. Just need to add a head shield above each one and the exhaust will be done.. or maybe not....
....spent a bit of time experimenting with noise levels - admittedly inside the garage as the weather was pants!
Seems the carbon box is very, very loud! I put the stock air box on the end in addition to the carbon one and the volume when down considerably! May have to re-think that for SVA - or even add the stock airbox for the test if I can fit it in!
The exhaust is pretty loud, and I think I may buy two extra mufflers, this time from Jetex and I can't seem to get the magnaflow models I'm after in the UK. The Jetex ones are also a straight through design so I should think it wouldn't have too adverse an effect on the performance of the engine, I think my head will thank me after a longer trip.
If I do want to take it on any track day I think I would get black flagged pretty quickly with the current set-up - wish I could take it for a real world test drive on the road but that is a bit of an issue - as you would expect!
More noise testing tomorrow if the weather is better.
Seems ok from a dry run without fluid or servo. Full test will have to wait until I've put fluid back in the system. Going to need to glue this in place some how, probably with silicone sealer. Given the shroud (?) is so big on the BMW master cylinder I can see this ever falling out, but it could reposition depending on the speed at white the piston retracts when you lift your foot off the brake.
Refitted the tank today with rubber strips and added two additional exhaust hangers just behind the seats. That makes 4 hangers at the back and the one on the gearbox which should be enough fail safes if any of them go.
There should be more than enough room between the tank and the mufflers now. Just need to add a head shield above each one and the exhaust will be done.. or maybe not....
....spent a bit of time experimenting with noise levels - admittedly inside the garage as the weather was pants!
Seems the carbon box is very, very loud! I put the stock air box on the end in addition to the carbon one and the volume when down considerably! May have to re-think that for SVA - or even add the stock airbox for the test if I can fit it in!
The exhaust is pretty loud, and I think I may buy two extra mufflers, this time from Jetex and I can't seem to get the magnaflow models I'm after in the UK. The Jetex ones are also a straight through design so I should think it wouldn't have too adverse an effect on the performance of the engine, I think my head will thank me after a longer trip.
If I do want to take it on any track day I think I would get black flagged pretty quickly with the current set-up - wish I could take it for a real world test drive on the road but that is a bit of an issue - as you would expect!
More noise testing tomorrow if the weather is better.
11/01/2007
Website Improvements
08/01/2007
Video Section
We've added a video section to the menu at the top as there are a number of Sportster related clips now, click here
07/01/2007
Noise!
We were playing with a db meter today and on the A weight setting it's idling around 80db 40cm back at a slight angle. On
the way up to 4000rpm it peaks over 100db and at 4000 it is in the high
90's. Will really need to keep a close eye on that and do some research
on exact testing conditions for SVA. I think it's pretty boarder line
right now. I did find blocking one of each of the pipes on either side
with my hand made it significantly quieter (by ear anyway) So I may
just need to block those off for the test
06/01/2007
Exhuast installed
The exhaust is installed, and it sounds great! Possibly a bit loud for SVA. Will test it with DB plugs from Jetex, or possibly install some extra mufflers. But first we'll dig out an SPL meter and see what it reads!
Here is the video: Exhaust Video 12Mb Xvid / MP3
Here is the video: Exhaust Video 12Mb Xvid / MP3
01/01/2007
Exhaust Mock Up
The exhaust mock is finally finished! After a complete disaster last year with a shop in Southampton that didn't do their job we've changed plans and created our own exhaust with a BTB 6 branch manifold and two Magnaflow glass packs. The rest of the piping is made of Jetex stainless universal parts.
This week we finished the mock up on the exhaust! Due to Richard's Compact project we've got a MIG welder now! This meant that we could tack weld the bits together! It needed the 35 degree angle replacing with a 45 as the back box on the Y pipe ended up sitting far too far back and there wasn't enough straight parts to move it far enough in. With the 45 everything now fits with just enough adjustment room to get the back boxes aligned.
At some point soon we'll take the parts than need the welding finished off to Black-Cat (a talkaudio regular) who will finish it off properly - not quite read to make nice stainless welds yet after about an hours practice!
We've also re-done the brake pipes at the front and fitted the BMW master cylinder with adapter plate
This week we finished the mock up on the exhaust! Due to Richard's Compact project we've got a MIG welder now! This meant that we could tack weld the bits together! It needed the 35 degree angle replacing with a 45 as the back box on the Y pipe ended up sitting far too far back and there wasn't enough straight parts to move it far enough in. With the 45 everything now fits with just enough adjustment room to get the back boxes aligned.
At some point soon we'll take the parts than need the welding finished off to Black-Cat (a talkaudio regular) who will finish it off properly - not quite read to make nice stainless welds yet after about an hours practice!
We've also re-done the brake pipes at the front and fitted the BMW master cylinder with adapter plate
25/12/2006
The Sportster is back out of the garage!
After a good clean up in there to clear out the back log of Compact parts its looking good again. Took the metro master cylinder off today and test fitted the BMW one. There is a gap the size of the adapter plate between the servo pin and the master cylinder - should be quite easy to add something in there to fill the gap due to the design of the BMW master cylinder. With a gasket there will now be a good seal here. There's nothing worse than a vacuum leak on an M20 to upset its idle! Slow start but a start at last! :)
10/12/2006
We'll be back soon
..hopefully! Richard's Compact is going well. The engine is running as can be seen in this video (Xvid - 8Mb) - not much left to do on this 'side project' now. We'll be working on the Sportster again before the end of the year!
And some piccys for the hell of it :)
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And some piccys for the hell of it :)
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