jay.jay
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Registered: 28th Dec 10
Location: Gloucestershire
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I have recently swapped my sportex race tube for the original middle silencer section, and the car feels faster with more power lower down in the rev range. Can some one tell me why this has happened? The exhaust system consists of a lexmaul 4-2-1 manifold, decat, standard middle silencer and sportex back box
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Phillips_91
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Registered: 20th Jan 10
Location: Blackpool. Drives: Sapphire Black Mk4 Astra 1.8
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Possibly because theres more back pressure, the valves may be seating better, but this is more of an engine thing opposed to exhaust, im an exhaust fitter but wouldnt be expecting these sort of questions from a customer  usually why has my cat failed etc
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GteRedtop
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Registered: 13th Jun 07
Location: Your mother's Otter's pocket
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Yep, Back pressure is needed alot more so on a N/A rather than Turbo charged
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jay.jay
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Registered: 28th Dec 10
Location: Gloucestershire
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Ah right that would explain it, anyone recommend some decent stuff to seal the joints with? That gun gum is crap its blowing like a whore 
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Phillips_91
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Registered: 20th Jan 10
Location: Blackpool. Drives: Sapphire Black Mk4 Astra 1.8
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We use engineering silicone, much better than exhaust paste because it doesnt dry and become brittle, a little on the dear side but if you can get hold of it it's brilliant stuff 
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Phillips_91
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Registered: 20th Jan 10
Location: Blackpool. Drives: Sapphire Black Mk4 Astra 1.8
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not entirely sure but this looks very similar to the stuff we use http://www.ebay.co.uk/itm/44NC-Neutral-Cure-Automotive-Silicone-Sealant-/250721937110?pt=Motors_Car_Truck_Parts_Accessories&hash=item3a603126d6
Edit: the product in the picture (aslong as it doesnt change and is still a white tube with clampco silicone sealant on the bottle) is the exact stuff we use http://www.clampcouk.co.uk/products/chemicals/sealants/
[Edited on 21-07-2011 by Phillips_91]
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jay.jay
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Registered: 28th Dec 10
Location: Gloucestershire
User status: Offline
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I was thinkin about usin silicone but then i thought it might just burn off with the heat, does it really work that good? May consider buyin some 
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Phillips_91
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Registered: 20th Jan 10
Location: Blackpool. Drives: Sapphire Black Mk4 Astra 1.8
User status: Offline
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as long as it's automotive grade then yes it's good, normal bathroom silicone big no no! but this stuff is good upto something like 300 degrees, but if it's infront of the cat dont use that stuff you need the black RTV silicone otherwise it damages the cat converter
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jay.jay
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Registered: 28th Dec 10
Location: Gloucestershire
User status: Offline
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Well its decat anyways so no problems there cheers for the advice pal
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Phillips_91
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Registered: 20th Jan 10
Location: Blackpool. Drives: Sapphire Black Mk4 Astra 1.8
User status: Offline
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not a problem if you need anythin else just drop me a u2u
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harrisp
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Registered: 15th Dec 07
Location: Derbyshire
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quote:
Originally posted by Phillips_91
as long as it's automotive grade then yes it's good, normal bathroom silicone big no no! but this stuff is good upto something like 300 degrees, but if it's infront of the cat dont use that stuff you need the black RTV silicone otherwise it damages the cat converter
You sure?
Normal bathroom silicone is fine, its heat proof and I have used it on loads of cars.
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Phillips_91
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Registered: 20th Jan 10
Location: Blackpool. Drives: Sapphire Black Mk4 Astra 1.8
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it MIGHT do if your engines running absolutely spot on and the exhaust isnt getting too hot, but the number of cars that i see where even with heat proof gloves we can't touch the exhaust because it's getting that hot i wouldnt want to trust bathroom sealant to stay in one piece, this is specifically designed to never set and stay flexible
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jay.jay
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Registered: 28th Dec 10
Location: Gloucestershire
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Dont think id trust it either, exhaust on my car managed to burn all the copper slip off the clamp bolts, wouldnt dare risk normal silicone me 
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antnee
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Registered: 30th Dec 07
Location: Cov Drives: Clio 197
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Turbo's tend to like a little bit of back pressure to help the oil seals
NA's, its all about exhaust gas velocity not back pressure (although it does come into it), if the exhaust is too big, gas slows down, too small its restrictive therefore slows down.
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harrisp
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Registered: 15th Dec 07
Location: Derbyshire
User status: Offline
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quote:
Originally posted by Phillips_91
it MIGHT do if your engines running absolutely spot on and the exhaust isnt getting too hot, but the number of cars that i see where even with heat proof gloves we can't touch the exhaust because it's getting that hot i wouldnt want to trust bathroom sealant to stay in one piece, this is specifically designed to never set and stay flexible
It is fine Ive used it many a time.
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