E30 318i: Noisy exhaust gets a bung / silencer

My E30 has a 4" straight-through Japanese tuner style exhaust back-box fitted, which to the say least is LOUD. In fact, it's one of the loudest I've heard on any car, including a Subaru turbo I had with a de-cat pipe. I figured the centre-box had also been removed from the E30, given the noise level, but find it is still there under the car and looks to have been replaced not too long ago, so I guess the only reason for the volume from this 1.8 litre 4-banger is because it never had a catalytic converter from the factory and is subject to no emission controls that bind (and quieten) modern cars. This E30 is 1988, so must have been right at the end of this phenomena.

While the loud pipe might be fun on a jaunt, working on the engine at home I find myself needing to start and idle the car constantly for testing and this is where the noise causes a problem, mainly with my neighbours and passers-by. They tolerated it for a couple of weeks, but with a few running problems that are still being ironed out and the car unable to move to another location I decided to try and mute it a bit. 

I had two options. Buy a more sociable back-box or get a silencing 'bung' for the current one. I'm not best pleased with look of the Jap-style straight-cut end pipe, I mean I like them but don't feel it suits the boxy E30 and though I'm down with car style juxtapositions all DAY, this isn't the one I would have chosen, so first looked for a replacement. New stock items are not expensive, but too much for this project, so second hand was the way, with twin 'sports' style spurious back boxes and used OEM items going for between £50 and £100. I was tempted by a nice twin square pipe from a German tuner, but the seller had no idea how loud it was and at £55, I still deemed it too pricey at this uncertain stage in the project. People at work fit ‘bungs’ to their motorbikes so I thought this was budget way to reduce the burble by a few dB.

DOES IT WORK?

Yes and no. It certainly takes the edge off the noise level, that ‘crack’ has gone, but it’s still one loud exhaust. The info says it reduces sound levels by up to 15 decibels and I have adjusted to the quietest, most restrictive setting, but without a dB meter I can’t really say if it is that much. In my opinion it’s not to that great an extent but it is somewhat quieter. 

Don’t expect the exhaust to sound as quiet as a stock back box with baffle plates. I suppose you’re never going to get a quiet exhaust tone and still enjoy the slight increase in power a straight-through pipe gives, so as ever there is a compromise, but it has certainly done the trick for me of making the car less anti-social when tuning it in my driveway! Who knows, when I get the E30 out and about over the summer the bung may well be coming back out.

Late '90s BMW Crossover Concepts...

 A couple of interesting concepts here from the 1990s that you might not expect from BMW, but showing once again that they were well abreast of current trends and design cues that would become prevalent towards the end of that decade. 

The first, below, is this strange high-roofline runabout / city-car that seems to be a mix of Fiat's controversial Multipla and the bubble Nissan Micra that both came along soon after. This concept also pre-dates the BMW MINI (and the 1-Series) that arrived at the turn of the millennium and was perhaps the fore-concept of BMW's small car range after becoming aware of buyers desires for high-end hatch-backs following Audi's A3. Either way, it shows BMW were having a go at that small-car big-interior vibe that has now become the basic staple of small car design.

The next, below, is a compact, convertible, sports-car, SUV. Yes, BMW are covering a lot of bases with their concepts around this time and maybe, with this beast, trying to wrap too many trendy cars into one package. The high-clearance quasi-off-road look makes sense with the success of the then recently released X5, but in my opinion giving a taste of what would come along many years later, with a plethora of smaller, sportier SUVs like the X1, X3 and of course the X4 and X6 grand lifted coupes. Interestingly, this concept has integrated 'wrap-around' wheel-arches like the odd Chrysler PT Prowler retro sports-car from the late 90s, though without the open-wheel stance. Was this to pass certain road-laws but still give the high-clearance look of a 4x4? Perhaps these were removable if you were throwing knobbly-tyres on and going off-road?? I guess we will never know.

E21/E30: Crude Rear Seat Repair.

When the seats arrived the rear one had a noticeably big tear on the top of the back-rest. By the time I'd finished cleaning them however, there were now 3 tears along the same strip. I was being super-careful with the scrubbing brush, but after 25 years under the back-window the glue is coming away and the strands of twill fabric separate very easily indeed. An attempt to repair one of the splits only made it worse as the material is stretched by the glue and can't wait to rip.

I considered throwing the stock beige seats back in, but then had a moment of er, inspiration, and found a strip of spare material wedged into the frame behind. I cut it into patches and stuck them down with fabric spray-adhesive, £7.99 but it's strong stuff.

It's not the prettiest of repairs, despite matching the lines up, but looks better than threadbare, won't get any worse now and the interior of the car looks a lot fresher with them in I must say. If they're going to stay though, a permanent cover-up will be needed - probably in the form of a parcel-shelf re-trim. The beige carpet could do with a refresh, so I may extend the fabric past the shelf and have it cascade over the back-rest slightly. We will see.

E21 316: Fitting E30 rear sport-seats - or having a go anyway.

Stock fit works, but leaves big gaps.

As with the front seats I used HSVTurbos build [here] as a rough guide. His rear bench-seat is the all-sponge kind, whereas mine have the sponge base, but a sprung back-rest, possibly due to the folding arm-rest or model year difference. This means I have a metal frame to work with on the back-rest, so it can be pressed flat to greatly reduce the proud fit at either corner, but also means more needs to be cut away than just blobs of sponge. The E30 coupe's rear seat-pan, the body-tub and front doors are almost identical dimensions to the E21, so the rear seat-base just slots in. There are no brackets along the bottom-edge to clamp the squab down, but with it seated flat and wedged under the back-rest these may not be necessary, although fabbing some up might be worthwhile to stop the carpet sagging down in the footwells.

The general shape of the back-rest is more or less the same as the E21 and the hooks fit into the existing brackets, though the E30's parcel-shelf is curvier, causing the back-rest to stick out slightly at the top corners. The back-rest also sits slightly higher, leaving an inch gap at the bottom between it and the squab. If these gaps don't bother you then the seat works fine like this and will only need a little chopping off each upper corner to achieve a pretty good looking fit. If they do, then a little more work is required to seat the back-rest flush and minimise the corner gaps.

The main problem here are the seat-belt reels, which protrude from the bulkhead and fill up where the upper corners of the back-rest want to be. The back-rest bolsters are also slightly too broad, though the centre of the rear frame is more or less a perfect fit to the E21 bulkhead.

Modifying the Back-rest:

1. Bend up the small hooks holding the cover material in place over each side edge of the back-rest and pull the fabric clear of the metal frame.

2. Cut away the side-support on each side of the frame, leaving just the edge of the 'mattress' frame that holds the springs, as in the photo below. The brackets at each bottom corner should come away here too.

3. Cut in half the metal bar that runs between the centre and bolsters, the one attached to the top spring in each corner, and trim away the top spring as close to the frame as possible.

4. Cut the metal bar running along the top of the frame about 4" in from either top corner

5. Cut away the boar-hair matting along each side of the back-rest to reduce its depth by about half.

6. Cut a 2" square from each top corner of the boar-hair matting to give a recess where the seat-belt can run freely back into its reel.

7. Replace the fabric cover, hooking it to points on the mattress-frame and tucking it under the springs. At each top corner, I pierced a hole and ran a cable-tie through to hold the folded fabric clear of the seat-belt reel.

Fitting to the E21:

To get the back-rest sitting flush to the seat-base the original mounting-brackets may have to be abandoned in favour of slotting the hooks on the bulkhead directly into the top of the back-rest frame. The original lower brackets are attached to the frame here and may need cutting off for a tight fit.

1. Hook the top lip of the back-rest frame over the metal hooks on the bulkhead. Press hard to make sure the metal bar gets over the hooks and not just the boar-hair and fabric. Give each side a good knock down onto the hooks. The top of the back-rest should be about 5mm lower than the parcel shelf.

2. Fit the centre arm-rest and lock the clips into place. The back-rest should sit a bit proud of the bulkhead and need pushing flat. Drill two holes through the back plate of the arm-rest and bulkhead. Fasten it together with two bolts or pop-rivets. Not only will this hold the seat in place, it will also stop it moving when the arm-rest is lowered.