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.
07/03/2009
Loured Up
After not having much success with the bead roller I went to go see http://www.coollouvres.com/ today, here are the results, I'm really happy with these:
01/03/2009
Bodywork final stages of prep for paint
Rough fill in of the holes in the tub with 8 layers of glass to give it plenty of strength.
Tub hole cover from the back
New side repeaters fitted - these need the hole enlarging a bit.
New scuttle side panels sitting snugly with the new repeater above.
Vent hole cut and cover fitted
Mirror holes filled in (the ones nearer the front they were in the wrong place!) and vent holes.
Back of tub sprayed black - hides all the modifications.
Bonnet cleaned up ready for louvres and the hinge holes sunk slightly further to allow the screws to sit more flush.
Fibreglassing experiment - this will form an attachment for any future rear diffuser.
Fibreglassing experiment - this will form an attachment for any future rear diffuser.
26/02/2009
Wiper video
I took some video with my phone so its pretty cruddy quality but shows the wiper motion:
24/02/2009
Bodywork update
A few more things checked off the list:
- Finished the scuttle side panels
- Opened up the indicator holes on the scuttle to fit the new ones
- Rear end break down
- Step one of filling the seat belt holes in the tub
I recommend everyone take their tub off after a year and check for rust issues, we've got a few area's that need to be cleaned up and protected.
23/02/2009
Scuttle side panels
New scuttle side panel without louvres compared to the original with louvres. The new one also now has folded back edges which gives a much better edge.
New scuttle side panel on the passenger side with folded back edges.
22/02/2009
Wiper Installation
After spending a lot of time eyeing up the location for the wipers I came to the conclusion that 90 degrees would work best for us. After looking inside the gearbox I found that we have a 110 degree drive gear (which matches the sweep measurement I took a while ago). So I ordered a 90 degree drive gear.
Wiper wheel boxes installed. I had to thin down the fibreglass on one of them as it was too thick to mount the wheel box.
The boxes are fairly in-line.
Motor mounted on a metal plate. I plan to move the hoop for the motor a little hight so the motor is held a little better. Its seem to hold fine as it is however I would feel better with it moved.
Tubes cut to length and flared, good that we had all of the tools from installing the brake pipes as they came in perfectly for this job.
All the parts ready for install. We bought some chrome tops for the wheel boxes as Marlin supplied rubber ones. I am using the rubber ones for fitting to avoid damaging the the chrome ones.
Wipers installed, still need to cut the arms to the correct length.
Tubes Installed.
Wipers in motion.
Washer jets installed.
21/02/2009
Louvre Project
The ITB projects a bit quiet right now as we're trying to get the car ready for paint. Part of the this is a set of louvres.
I've probably spent 16+ hours on the lathe with these, the curves were right headache!
Test results so far are OK, but not perfect. The thing I'm have the biggest problem with is getting a nice start and finish. I think I'm going to have to make up a wooden die I can use to hammer a nice finish to the start and ends.
They are for this machine:
10/01/2009
ITB's continue
A bit more progress today in preparation so the manifold can be completed. I couldn't quite run the pipes at the same angle as the holes in the head due to using the stock manifold. I've opted for a shallower angle that will result in a relatively smooth transition between the pipes, manifold and head. I could always completely custom make a manifold at some point in the future.
The other big step was to get the throttle bodies properly spaced. I cut 10 spacers on the lathe exactly 11mm wide. There still a lot to including the minor issue of welding the pipes on - not sure how this will work but I suspect it will involve doing a lot of grinding to clean it up!
Ali tubes cut
Quick test fit
"just" needs to be welded!
And from the other side (yeah the throttles are the wrong way round ;o) )
Spacers cut on the lathe to space each throttle 11mm wider than they are on the GSXR
06/01/2009
ITB Idle Control
I've been research idle control on these. The GSXR has a manual fast idle lever on the bar. Some people have experimented with a stepper motor to control this, but I think I'll probably employ the solution that BMW themselves use on the M3's - a common vac pipe connecting all 6 cylinders and a standard ICV bolted up to it. I can use the second set of injector holes that are directly on the throttle body.
04/01/2009
ITB's continue
Two sets of ITB's give you 4 bolts to screw them together - not long enough for 6 throttles. The solution is to chop the thread off two of them and the head off the other two. Then the 4 bits are welded together to create one long bolt.
After welding the join is ground down to make it round and smooth.
Which means with temporary spacers its all one piece now