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.

E21 316: Update + MOT Pass

After my disastrous few weeks I managed to get hold of a Bilstein strut-insert and get it onto the car along with the longer springs, meaning it was finally back on the road and in an state worthy of the MOT test. I cautiously rolled down to the test-station on Saturday and am glad to say the E21 passed with flying colours!

Bilstein damper is strong, but will be a pain with the short springs.

This was a relief considering the slightly dodgy seat-frames I made bolted through the floor-pan, which stuck out like a sore thumb when it was up on the ramps, along with the scuff marks where I've grounded the underside, but with the car at a more standard height off the ground this didn't see to bother them and there was no problem with the chassis at all.

Oddly, the guy told me that the split-pins were missing from the castle-nuts on my steering track-rod ends and this would actually be a fail under normal circumstances, but they could see I'd been working on it and decided to give me the benefit of the doubt. This was true, I'd had them off swapping the springs and hadn't bothered to replace the split-pins as they would be coming straight off again to put the short springs back. That was decent of them to let it go, as it would have been beyond frustrating to lose another week to something so trivial and shows just what a pain the UK MOT test is.

Folded up and with a 1/4 inch thick layer of
pallet-wrap to send as a parcel.

Spending on the E21 has been a bit out of control since buying the E30 seats and it is still in desperate need of the wheel-arches finishing off. By this point, I'm past what I can recoup if I sell the car. I'm still using my E39 as my daily, the E21 has had no use for nearly a month with no MOT and finally, due to a planned move, it's looking like I will have to let her go anyway, unless I can find somewhere cheap enough to store it. I had hoped to have the arches skimmed off and painted by the guy who did the respray, but money is tight so I will be buying a rattle-can and doing the best I can with them.

Thankfully, I've managed to generate a bit of extra cash to pay for the strut-debacle [this post], by selling some bits on eBay, like a battered old set of alloys, an E36 nose-cone and other bits I had lying around, as well as the original beige passenger seat from the E21 - I think I have enough seats for the car now. I hope the seat arrives to the buyer OK, as I had to practically shrink-wrap it to be able to send it Parcelforce [£27], pictured, as the original method of courier was just over £60!

My spare set of E21 ash-trays is not selling on the other hand and is still on the site here - http://www.ebay.co.uk/itm/181235987123.

E21 316: Burst shock-absorber woes...

SPAX adjustable - like hen's teeth.

Well, I've had a bit of a nightmare week. As I was replacing the front n/s shock-absorber with the new spring, ready for the MOT on Saturday, the strut-insert burst in my face. To get an extra couple of inches clearance at the top and get it under the wing I'd been pushing the damper down into the insert. I figured they sit quite far down with the short-springs anyway, but eventually, probably after doing it several times, I must have plunged it further than its full operating depth and it popped, sinking the insert completely into the strut.

You wouldn't think pushing it down would pop it, considering the forces on it under load, but once its down far enough the top seal just fails under the pressure of the oil. You can have SPAX, as with most adjustable-inserts, re-filled and the seal replaced if you can be bothered to send it back to the manufacturer and pay the cost, but with time of the essence I just bought a new one.

Larkspeed in Leeds were the cheapest, though the price had gone up from £90 to £112 [and £118 now for the shortened!] for a single insert, but they claimed to have the part in stock and would have it to me by Tuesday the latest. Today I rang them to say it'd been a full week since they rang to confirm the order and still no insert. After half an hour they rang me back to say the insert had been specially ordered from SPAX, who were now lacking correct parts and can't build them until the end of October. I wish they had told me that last week as I'm now waiting on a refund...

Bilstein - fixed damping-rate and pricey,
nothing but good reviews.

I rang DC Performance.co.uk, who also claimed to have the part in stock and it would take 2 or 3 days. Before parting with any money this time I asked if they could check the insert is definitely in stock, which they are not, so it's not looking hopeful for any existing stock anywhere. I will be contacting SPAX directly from now on.

Monroe Gas-Matic - strong, but ride too soft.

So what are the short-term options? There are no ride-adjustable inserts in stock and available now, so it looks like i'm now bound to non-adjustable inserts. Stiffened Bilstein inserts are £62 each, where OEM-replacement ones can be had for as little as £20. With the springs this low, I have no idea what would work best. The sportier, better-brand damper might last longer under the stress and be a better match for the adjustable SPAX on the other side. Alternatively, the cheap, softer damper might compress better under the load and a pair will only cost £40 should the o/s one need swapping too. Another option is to replace both with Monroe gas-filled dampers for £123. The blurb says they are a heavy-duty design for trucks and vans, but according to this thread they are just too soft and will cause me to bottom out. So, £60 for one Bilstein it is, or take a chance on a cheap KYB. Hmmm, stress.