| Author |  Topic  |
Derek
V4 Mad
United Kingdom
815 Posts |  Posted - 29 Jul 2010 : 11:21:25  
| Thanks Alex. It's an "interesting" problem and curing it would make cruising a lot more relaxing. So often it turns out that the traffic flow speed coincides with the resonance (100km/h your motorway limit?), but 60 is often too slow and getting past it means pushing 70 and you might not want to go that fast anyway. Economy drops away as well. It could well be a "tuned" pipe, and like a trombone the note changes with length. There can't be many cars, I can't think of one, with such a long uninterrupted length of pipe. Being small bore just makes it worse. The long Simons silencer should help but it's a straight through type so probably doesn't make much difference. Umfortunately, the flat floor limits your options. Perhaps adding another 1m+ length of pipe onto the silencer and out to the other side would tune it to a different frequency?  |  |
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Borstlap
V4 Fan
Norway
139 Posts | Posted - 30 Jul 2010 : 16:51:32
| quote:
[i]Perhaps adding another 1m+ length of pipe onto the silencer and out to the other side would tune it to a different frequency?
It sure would make an interesting contraption  . it is that connection midway that causes the trouble. I remember that I had an exhaust change once (standard type) and the pipe was connected to the floor; it hadn't been before. I got back on the motorway, sped up and out of the blue it felt and sounded as if the whole car would disintegrate, what a horrible noise!! It was somewhere between 100 and 110km/h (another good reason to do 120 ). If I remember well the noise got less after the change to the Simons/Jetex.
When I made the extra clamps the first attempt was the clamp attached right behind the bulkhead, into the floorboard where it was only one layer thick: no good, noisy as hell. I redrilled in the thick part where the bulhead and the floorboards meet and form up to a three-layered thickness. That got rid of the vibration. The trick is to drill where there are no large single layer surfaces, then you win already half of the battle.
Alex | |
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Smokey six
V4 Beginner
United Kingdom
56 Posts | Posted - 31 Jul 2010 : 10:53:43
| Thanks Derek,
If no work comes from Mondays MOT, I will have ago at Making a pair of clamps.
Your description is adequate.
Lenquote:
Originally posted by Derek
I'll see what I can do but it's just made from 1"(?) wide flat steel which wraps round the pipe and then is bent off at right angles, with a couple of holes to allow it to go under the nut on the engine mount and bracket. When I fitted mine it didn't clamp up very well and I stuck a couple of adapted bolts in the junctions to allow it to be tightened properly. Neat but a bit of a bodge. It was as if the clamps were made for a slightly bigger downpipe but I don't think they ever changed that.
Saab should have brought out a revised Sport/Monte Carlo version of the 96 in the early 70's. That would likely have had a much better exhaust which could have also been fitted to all models. The standard front box can only be described as "functional".
Broke it? Me? it came orf in me 'and
Len W | |
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Derek
V4 Mad
United Kingdom
815 Posts | Posted - 31 Jul 2010 : 18:15:17
| Forgot that I'd taken a couple of pics when I brought mine back from its MOT on Wednesday. Passed with no adviseries . Expensive week as I took my Primera estate in the day before. That passed too without adviseries. Passing is much cheaper than failing. 
Does this help? Note my bolt/wedge. Although it doesn't look like it. the thicker part that the clamp bolt goes through is actually part of the main bracket. It twists and bends. I found it difficult to get the clamp round the pipe very tight but it's the lateral movement that you're trying to stop so it probably isn't that critical. Don't be surprised if the exhaust sound in the engine bay has a bit of a ring to it. I seem to remember thinking that but I was replacing an old leaky one with a new one with no carbon in it. I think they are completely empty with no baffling at all?
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blue95V4
V4 Fan
United Kingdom
195 Posts | Posted - 05 Aug 2010 : 15:38:29
| Just read this, and was also chatting about exhaust pipe mountings to a few folks at the National. I haven't fitted my new Jetex yet, so hope that I don't get the same problems!
in Oct '77, Saab announced a campaign on '76 and '77 models (95/96) to add an additional suspension kit (72 85 182) to the [standard] exhaust pipe, 60mm aft of the rear edge of the engine compartment floor, as per the '78 cars. I've never seen this fitted to any car that I've looked under, though! The campaign was introduced by SI 252-26085 and was stamped IMPORTANT. I have the SI and will be very happy to scan it and email it to anyone who wants a copy. Not sure if the pm facility works on this site ..... so try davidnlowe@btinternet.com
David (95 V4, 260-2 Saabo and a 96 2T, plus a modern Saab - enough for the time being!) | |
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Derek
V4 Mad
United Kingdom
815 Posts | Posted - 05 Aug 2010 : 18:34:42
| My car (above) reg 10/11/76. Maybe the clamps were part of the kit but the additional floor mount is long gone. Didn't notice anything when I changed the front box and pipe. I'll check underneath to see if there's any sign of it/them on the floor pan.
Does the SI give any details? I'll mail for a copy, please. | |
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| Topic | |
Jetex; "The Noise"
