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Just finished my exhaust system.....but all is not well!I have 2 standard 3:1 manifolds joined by a y section into a universal cat(ihave e36 2.5).After cat, y section runs 2 pipes down to tr6 back box.All was good,with a lovely note until everything after the cat got red hot...really red hot....melting the rubber mounts with back box hitting floor!I am wondering if this is due to the system not having a straight thru pattern,or if my manifold outlets which are bmw are wider than the remaining system giving build up of hot gases>Any ideas?
Hmm - that's strange. Did the silencer literally get red hot? What sort of exhaust mounts are/were you using?
I wouldn't have thought it was a problem with the TR6 box. The TR6 produced about 150hp from a 2.5 engine and so I guess would have produced similar amounts of exhaust fumes - that was the reason I have used one. It's not like you are using an exhaust that was made for a much smaller engine.
Did you have the engine revving high while the car was stationary? That would generate more heat and you wouldn't have an airstream cooling the exhaust as you would if the car was moving.
It's not unusual for Cat's to run red hot - that's how they produce the catalytic action - perhaps that is what is causing it.
Anyone else got any idea's
I am close to starting my car now (just got some decorating to finish at the moment - groan) it will be interesting to see if I have the same problem as I am using an E30 without a cat and the same TR6 rear sliencer.
I purchased the back box from rimmers, the same one I think you have.I suspect that there is a delay of gas escape due to the tail pipes coming out the opposite side to the entry pipes.I am going to open the blanked exits on the box as well thus having 2 twin exits, and will see if this helps the problem.
I purchased the back box from rimmers, the same one I think you have.I suspect that there is a delay of gas escape due to the tail pipes coming out the opposite side to the entry pipes.I am going to open the blanked exits on the box as well thus having 2 twin exits, and will see if this helps the problem.
As I remember the box is baffled which would slow down the exhaust gases but also produces a quieter exhaust.
What I don't understand is why its OK for a TR6 but not a BMW. Perhaps its something to do with unleaded vs leaded fuel - but by now all TR6's must be running unleaded fuel anyway.
That's strange??
Maybe the silencer is actually blocked or not assembled correctly?
I have only had my engine running a few times but the silencers (also TR6 ) barely got warm. I have the original BMW front section and the middle box, but I can't see this making much difference.
the car was at high revs, but started from cold, thus not overheating.As all the heat and lovely glow of red was after the cat section, I assume that the horizontal back box is the problem>I have mounted this on the large cross member behind the seats,not below the the tank;trial tomorrow with extra outlets.My middle section is short, and houses a single universal cat,manifolds and downpipes are bmw e36 standard.If this fails may try individual straight back boxes, also seen on tr6, or as a last resort,cook breakfast on the back box!
I should think a baffled exhaust would not create a reaction like that, most mufflers are not straight through and do indeed run through several baffles - bit of an odd one!
I do know cats can get very hot, may it just needs a longer run between it and the muffler ?
Have you got a muffler off the original car you can try - that way you could try and eliminate potential problems.
I've got a E30 325 back box spare if you want it for testing.
After that you could try running without the cat and see if that makes a difference.
Thanks Patrick,hope tomorrow 2 start eliminations,may now try longer middle section also.Will keep all posted of progress.....there will be no medium rare steaks on this system...all well done!
I think this may be at least a contributory factor. Normally if the engine is running at anything other than idle you are moving forwards and there will be a considerable cooling effect from the airstream. The calorific value (heating capability) of the exhaust gass will certainly depend on how fast the engine is revving. How long did it take to get this hot - was it several minutes?
jeremy wrote:
I have mounted this on the large cross member behind the seats
Would be interested to see some pictures! Where does the exhaust exit then?
Look forward to seeing the results of your tests as i guess I may have the same problem then.
Robin,it was running for 5-8 mins, static.I can take some pictures b4 the weekend;If I email them to you can you host them on the forum?I was talking to an exhaust fabricator today and he thought I should run a single large core pipe after the cat, and thinks their is too much resistance in the back box, and may need to get one made 4 the job.the 2 pipes going into the back box are narrower than the down pipes.
Robin,it was running for 5-8 mins, static.I can take some pictures b4 the weekend;If I email them to you can you host them on the forum?
Not sure how you get pictures on the forum but I can put them on my web site and provide a link. I'm sure Patrick knows how to put pictures on the forum - Patrick?
Test for displaying pictures
Hmm - seems to work. So yes, Jeremy, please send me your pictures and I will put them on the forum.
