Pre Silencer bypass pipe
- Thread starter Guest
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Guest
New member
I'm considering doing the same on my SC as the old girl is being treated to a nice shiny new Haywood and Scott back box soon, i thought why not replace the pre-silencer wth a bypass pipe, certainly cheaper than a new pre-silencer. I also suspect the old parts will not be separated that easily.
Any thoughts much appreciated.
Any thoughts much appreciated.
Guest
New member
None, except maybe a small weight saving and noise. The 3.2 "likes" the pre-silencer, which is really just an expansion chamber as there is no baffling to restrict flow. If you take it off, you can see straight through it. Anecdotally anyway, the by-pass pipes are said to hurt mid-range torque.
As I would be the first to admit though, there is nothing wrong with wanting a bit of noise [
]
ClubSport 911
New member
Hi Shirish - good call w.r.t. the exhaust (looks v. tasty)
I'm also thinking of doing "exhausts" for the 3.2 / CS but perhaps if you have time, we could discuss the options I'm considering off-line ?
Always interested to share ideas
Rgds
I'm also thinking of doing "exhausts" for the 3.2 / CS but perhaps if you have time, we could discuss the options I'm considering off-line ?
Always interested to share ideas
Rgds
Guest
New member
I talked to Steve at JAZ about this just last week as I had thought my old crossover was a 2 piece when it turned out to be one piece. The 2 piece can theoretically be fitted with the HEs in situ, but the expert opinion is that this is pretty difficult even with the car on a lift and that you are better just getting the 1 piece and accepting you have to remove the LHS HE to fit it. The expert opinion is also that the 2 piece is more prone to leaks and to corrosion. He basically said they don't bother with the 2 piece anymore.
RB
Guest
New member
I'd go for 2. I can only say what I have heard - the euro pre-muff, ie., 2 is supposed to be optimal for torque. Intuitively, I might have thought that 1 would be good for top-end hp, where linear gas flow would be more important. I can't really see how 1 is much different to 3, can you?
Still, without dyno comparisons, who knows.
When it comes down to it, if you are replacing 2 or 3 pieces of the std exhaust then it isn't so much more to do SSIs and an MB911 muffler. Have you considered that?
Still, without dyno comparisons, who knows.
When it comes down to it, if you are replacing 2 or 3 pieces of the std exhaust then it isn't so much more to do SSIs and an MB911 muffler. Have you considered that?
Jacob
New member
Amo,
I bought the silencer bypass pipe that they sell at design 911 a few months back. It was great fun but was incredibly impractical. If you want to get an idea of what it sounds like, remove the 3 bolts that attach the silencer and pre silencer together and create about a 1" gap between them. Start your engine, have a smile and then look to see if all your neighbours have come out to wonder what on earth is happening.
I'm sure that mid range torque is effected and I would also guess that it would cause too much back pressure. I certainly would not expect huge bhp gains as the website claims.
I currently use the sports pre silencer, the main noticeable difference compared with the OEM silencer IMHO is the sound. It offers a much fuller, deeper and throaty sound.
I bought the silencer bypass pipe that they sell at design 911 a few months back. It was great fun but was incredibly impractical. If you want to get an idea of what it sounds like, remove the 3 bolts that attach the silencer and pre silencer together and create about a 1" gap between them. Start your engine, have a smile and then look to see if all your neighbours have come out to wonder what on earth is happening.
I'm sure that mid range torque is effected and I would also guess that it would cause too much back pressure. I certainly would not expect huge bhp gains as the website claims.
I currently use the sports pre silencer, the main noticeable difference compared with the OEM silencer IMHO is the sound. It offers a much fuller, deeper and throaty sound.
ClubSport 911
New member
Real A:B comparisons are often flawed. Example:- if you put a "sports" pre-silencer, and lose torque, then this is to be expected....(and perhaps more sever than it need be) without a corresponding re-map of the DME.
If you assume that inlet, head breathing, timing, etc and exhuast are all interlinked to power delivery, then it follows that by changing one component will alter the effect it has on the others.
Very often, the torque lost in a single modification will only be present (or worse than it need be) if you do not perform a corresponding re-map.
So...
Change inlet - REMAP
..change pre-silencer - REMAP
....change back box - REMAP
.....change to SSI's - REMAP
I think we're getting the picture here []. If you just change the item, then you are certainly not optimising it's insertion effect because the 3.2 ignition / injection system is dumb (it doesn't know if you have a £2000 exhaust or a plastic toy trumpet connected to the engine).
I think the true test on all these go-faster goodies needs lots of dyno time:-
Base Power logged
Re-map to optimal kw/M
Add the "special part"
Re-map to optimal kw/M
You now have the true A:B comparison of the part. You must optimise the map of the standard car prior to fitting any part really, so that when you add the new part and re-map, you can see the effect of that part alone (and not a re-map) on the performance.
Sorry to be long winded !
Steve
If you assume that inlet, head breathing, timing, etc and exhuast are all interlinked to power delivery, then it follows that by changing one component will alter the effect it has on the others.
Very often, the torque lost in a single modification will only be present (or worse than it need be) if you do not perform a corresponding re-map.
So...
Change inlet - REMAP
..change pre-silencer - REMAP
....change back box - REMAP
.....change to SSI's - REMAP
I think we're getting the picture here [
]. If you just change the item, then you are certainly not optimising it's insertion effect because the 3.2 ignition / injection system is dumb (it doesn't know if you have a £2000 exhaust or a plastic toy trumpet connected to the engine).I think the true test on all these go-faster goodies needs lots of dyno time:-
Base Power logged
Re-map to optimal kw/M
Add the "special part"
Re-map to optimal kw/M
You now have the true A:B comparison of the part. You must optimise the map of the standard car prior to fitting any part really, so that when you add the new part and re-map, you can see the effect of that part alone (and not a re-map) on the performance.
Sorry to be long winded !
Steve
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