Had a chance to record some new footage of the exhaust. XForce Varex VMK51-250 variable volume exhaust – it’s pretty much straight through when it is open. Here’s a few runs with the back boxes set to closed and open for comparison. The engine is a BMW M20B25 with a crank from an M52B28 making it an M20B28. It has a dbilas 282°/272° camshaft. It’s running the original 80’s motronic from Bosch with a chip map design for the stroker conversion. It does pop a bit when the exhaust is warm and you change down. Would benefit from a more modern ECU and tuning (someday!)
Another week, another new fluid all over the floor! Coolant this time from the rear port on the cylinder head. That’s the pipe that goes to the interior heater core:
Took it off and cleaned everything up on the head
New coolant flange gasket fresh from eBay!
Eveything fitted back together (after dropping the bolts…). It’s a little bit fiddly getting this back on with the battery tray in the way. The bolt seen in the follow photo on the left of the image is much higher up than you’d think.
The nice thing about the Sporters, more room to get behind the engine is just 4 bolts away!
Car pee’d on the floor…
It’s a bit drippy here at the back, but also at the front on to the start motor – not overly safe and smelled pretty strongly of fuel.
The main leak is here at the back between the hardline and the hose. The hoses have gone quite hard with age. There is a flare on the copper pipe.
All the fuel hose is 12-14 years old, this was visually the worst – the main picked pipe which is most exposed to the elements. The rest hard gone hard but were not cracked yet.
Emptied 25ltrs of fuel out the car using the Power Probe – all power disconnected on the car, hooked the probe up to the battery and switched 12v on the the positive side of the pump. Drained the tank very quickly into fuel cans.
Brand new hose up front for both the feed and return. Although these pipes all looked OK it was worth changing everything while the fuel system was drained.
New pipe from the tank to the first filter, to the pump, the next filter and then down the copper pipe where it was leaking. Also replaced the return rubber line.
Here are the rest of the old pipes that when in the bin, these had gone pretty stiff especially when compared to the new pipes.
All back together again! Used the power probe to prime the whole fuel system and check for leaks before starting the engine – fired up instantly, no waiting for the fuel pressure to build up when you prime the systems.
If you’re going to do any work on rubber hose, this tool from Sealey is invaluable, cuts nice straight ends every time!
This drain plug has been leaking forever, the drain part is reverse thread and normal thread into the radiator. The thread into the radiator needed more PTFE.
Due to topping up with water over the last couple years the coolant was starting to get hotter than normal when the engine was pushed. With the new coolant G48 with suitable BMW specification the needle stays steady on 80ºC when pushed hard. When testing on idle at a standstill the fan kits in at 88ºC and comes down again nicely to the low 80’s.
Video (obligatory no exhaust clip right at the end when everthing was off):
Built the other side of the exhaust today. Welding is ‘better’ than when I started but still pretty uneven. I can’t weld too far consistently around the curve yet. Did punch a few holes in the metal in places which results in having to ‘glob’ in filler rod to build it back up again. This part was back gassed as on the others before as it was a butt joint.
The 45º and straight pieces are sleeve fit, have welded these too so less clamps are needed. It also cuts down on potential exhaust leaks.
Once the two back boxes were hung I used some boxes and various peices of wood to hold the tips in place at the right height, this is with the car on the ground. Nothing on the Sportster is straight so this was done visually.
I used a piece of angle metal to line the tops and ends of the tips up. This helped make sure the tips were aligned straight with the ground, with each other and spaced from the back of the car.
Welding the tips on was a bit tricky, blew a few holes in the metal especially where the gaps were bigger. The left box alignment is slighly off, but it’s not visible once mounted and the tips are in the right place visually.
Both exhaust pipes mounted, the v-bands are visible in this shot. I used a tiny bit of exhaust paste on the mating surface, shouldn’t be needed with v-bands but I’d rather not have to take them off again! Also visible the zip tie exhaust hanger, nothing like attaching your exhaust to your suspension ;o) Kinds tempted to make some straight pipes that can be put in place of the back boxes, but that’s a whole new level of noise (did try running it with just the header and you need to wear ear protection…)
The more permanent hanger, this is a part is from pypes a US manfuacturer of exahust pipes. Had that left over from building an exhaust for the Mustang (http://www.mustang67.co.uk/exhaust-upgrade/) last year. Available at https://www.summitracing.com/
View from the otherside, wiring is hanging down. These cables need plumbing in properly and the metal shields putting back on the mufflers.
Car down on the ground from a low angle, the exahust tips are closer together than before (due to the input on the backbox being offset rather than in the middle).
The tips stick out a little further than the old ones, the wall thickness and slash cut work quite nicely.
Temporarily wired up the control box, and now for the noise test:
Closed it’s quieter than the jetex micro bullet muffers + the magnaflow boxes. Open it’s a bit of a beast, louder than before so that should be fun 😉 It’s pretty much were I wanted it to be, will see what it’s like on the road once the wiring is done.
Step 14: Cut down the output pipes, otherwise the tips would stick out too far.
Step 15: Tip test fit, could move these back further by cutting the tip input down a little which would make the hole bigger.
Step 16: Test fit on car, it’s just push fit to at this point
Opened up the cover that’s over the mechanisum which actuates the volume flap
View from the top, position seems quite good here
View of the inside of the back box, the perforated metal is the bypass output
The other side, the hole show is the bypass, the perforated tube up to the flap works much like the straight though magnaflow back boxes I took off when it is open.
Progress on building the new exhaust. The welds a’it purdy but they’re solid and not tea bag considering I’ve never used a TIG before and have learned how to use it with YouTube tutorials…
Step 1: Remove the old exhaust:
Step 2: Test fit some pipes, ordered the wrong bend, so either need to modify or get another one
Step 3: CAD (Card board aided design) to get the angles for the 2″ to 2.5″ transition. The height difference is 80mm, the input and output are parallel.
Step 4: Transition parts tacked together with v-bands clamps at one end. The v-band connects the backbox to the rest of the pipes, will allow for some angle adjustment later if needed.
Step 5: Back gas feed, v band clamp in place to reduce chance of warping when welding that part.
Step 6: The two height / size transitions welded up (don’t look too closely). Back gas worked well, clean weld through no sugaring / oxidisation on the backs.
Step 7: Cut down the inputs on the back boxes, they input at a slight angle so needed cutting flush for the v-band to be welded on.
Step 8: V-bands welded on – these were both back gassed
Step 9: Cut out hangers for from stainless tock and cut holes in each.
Step 10: Hangers bent 90º – welded these on, bit of a tough one to get the amps right, melted away a bit much of the original metal but I think I made it longer than it needs to be to compensate.
Step 11: Finishing up welding the first piece – this goes from the exsiting output all the way to the back box
Step 12: Pipe in place, it will be clamped were the colour changes from stainless, to stainless covered in dirt
Step 13: Back box in place on the hanger (into the existing E36 style exhaust hanger).
Step 14: May need to move the head shield a bit as the back boxes are closer to the centre of the car due to the offset inlet.
The bullet mufflers are now no longer part of the exhaust system, in theory the closed setting should be quieter than before and open should be the same or louder!