TD04 hybrid with bell mouth 3" downpipe?
22 July 2013, 12:55 PM
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TD04 hybrid with bell mouth 3" downpipe?
Hi Guys,
after some information.
I have a AF TD04 hybrid going into my 2003 WRX soon, I want it to spool as quickly as possible.
My question is, will having a 3" bell mouthed downpipe reduce the spool?
I was thinking it would aid spool, but read another members post (from 2011) who said he made the mistake of going 3" downpipe and it cost him 200rpm, on his classic.
I know 200rpm isn't much, but I want to be happy in knowing that I've gone the right way to get the best spool.
Experience and opinions welcome :-)
Cheers!
after some information.
I have a AF TD04 hybrid going into my 2003 WRX soon, I want it to spool as quickly as possible.
My question is, will having a 3" bell mouthed downpipe reduce the spool?
I was thinking it would aid spool, but read another members post (from 2011) who said he made the mistake of going 3" downpipe and it cost him 200rpm, on his classic.
I know 200rpm isn't much, but I want to be happy in knowing that I've gone the right way to get the best spool.
Experience and opinions welcome :-)
Cheers!
22 July 2013, 01:47 PM
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I believe it should gain spool. I went from 2.5 bell mouth to 3 inch bell mouth and that made mine feel more responsive but I couldn't tell you precisely how much as I drove it straight for a remap with a bigger turbo being fitted. Sorry I can't give you any specific numbers.
22 July 2013, 01:50 PM
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I believe it should gain spool. I went from 2.5 bell mouth to 3 inch bell mouth and that made mine feel more responsive but I couldn't tell you precisely how much as I drove it straight for a remap with a bigger turbo being fitted. Sorry I can't give you any specific numbers.
Hi, appreciate you sharing your experience.
I would think it would aid spool too, but I'd rather hear what others have found.
Cheers fella
22 July 2013, 04:39 PM
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Is this "as compared to standard exhaust and standard downpipe with cat"? i.e. 2.5 inch?
A nice bell mouth downpipe with no cat will definitely aid spool, however you will probably find that a 2.5 inch exhaust will spool better than a 3inch. You most likely don't need a 3 inch exhaust as a td04h won't be restricted by a 2.5 inch system.
AFAIK Most the downpipes are 3 inch, it is just whether it tapers to 2.5 inch at the end to fit the standard exhaust or stays 3 inch for many aftermarket exhausts.
If you are crazy about fast spool, then look into the work done before turbo entry, i.e. porting headers and a well designed up-pipe.
A nice bell mouth downpipe with no cat will definitely aid spool, however you will probably find that a 2.5 inch exhaust will spool better than a 3inch. You most likely don't need a 3 inch exhaust as a td04h won't be restricted by a 2.5 inch system.
AFAIK Most the downpipes are 3 inch, it is just whether it tapers to 2.5 inch at the end to fit the standard exhaust or stays 3 inch for many aftermarket exhausts.
If you are crazy about fast spool, then look into the work done before turbo entry, i.e. porting headers and a well designed up-pipe.
22 July 2013, 04:46 PM
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Is this "as compared to standard exhaust and standard downpipe with cat"? i.e. 2.5 inch?
A nice bell mouth downpipe with no cat will definitely aid spool, however you will probably find that a 2.5 inch exhaust will spool better than a 3inch. You most likely don't need a 3 inch exhaust as a td04h won't be restricted by a 2.5 inch system.
AFAIK Most the downpipes are 3 inch, it is just whether it tapers to 2.5 inch at the end to fit the standard exhaust or stays 3 inch for many aftermarket exhausts.
If you are crazy about fast spool, then look into the work done before turbo entry, i.e. porting headers and a well designed up-pipe.
A nice bell mouth downpipe with no cat will definitely aid spool, however you will probably find that a 2.5 inch exhaust will spool better than a 3inch. You most likely don't need a 3 inch exhaust as a td04h won't be restricted by a 2.5 inch system.
AFAIK Most the downpipes are 3 inch, it is just whether it tapers to 2.5 inch at the end to fit the standard exhaust or stays 3 inch for many aftermarket exhausts.
If you are crazy about fast spool, then look into the work done before turbo entry, i.e. porting headers and a well designed up-pipe.
The turbo has the hot side ceramic coated, I have a Harvey up pipe going on, with ported headers. The up pipe and the headers are all wrapped.
I have a bell mouthed de cat downpipe that doesn't taper down to 2.5" but my exhaust is 2.5" at the flange, then goes up to 3" straight through. I think I will just stick with what I have, unless I can find someone selling a used bell mouthed downpipe that has a 2.5" bore.
Cheers for the info!
22 July 2013, 06:13 PM
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whats the big deal about the bellmouth? should work just as good with any flange setup be it V band, 2 bolt, 3 bolt, etc.
from my limited but growing knowledge about boost (from a turboed N/A BMW background anyway) the general rule is bigger is better for spool (note i said general rule). also it is better to run a 3 inch DP tapering into a 2.5 inch system than the other way around as the further back the gasses travel the cooler they get so larger exhaust directly after the turbo makes the most difference is the entire system cannot be the same diameter.
furthermore and on the subject of our scoobs, i wonder would there be a benefit in spool having a larger diameter section directly after the turbo. for example if you have a 3 inch DP taper it up to 3.5 or 4 inch right off the back of the turbo for a foot or so (however long is feasible) and then taper it back down to 3 inch. or taper from 2.5 to 3 and back or whatever other combination of system size, larger size then back to system size.
from my limited but growing knowledge about boost (from a turboed N/A BMW background anyway) the general rule is bigger is better for spool (note i said general rule). also it is better to run a 3 inch DP tapering into a 2.5 inch system than the other way around as the further back the gasses travel the cooler they get so larger exhaust directly after the turbo makes the most difference is the entire system cannot be the same diameter.
furthermore and on the subject of our scoobs, i wonder would there be a benefit in spool having a larger diameter section directly after the turbo. for example if you have a 3 inch DP taper it up to 3.5 or 4 inch right off the back of the turbo for a foot or so (however long is feasible) and then taper it back down to 3 inch. or taper from 2.5 to 3 and back or whatever other combination of system size, larger size then back to system size.
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