3vzfe exhaust design

[thomp1983]

Morning, looking at redoing the exhaust system on my 3vzfe to try and gain some improvements, there's alot of info about regards downpipe design so I have an idea of what to do for that, my main question is regards the manifolds there's alot about saying there a poor design but not much information on how much is to be gained from redoing them to an equal length design. To have a set of manifolds and downpipes made will be around £800-1k with a figure of 20bhp gain being thrown around online, how much of this gain will be from properly designed downpipes as opposed to the manifolds as decent downpipes can be had for less than £500 so im trying to work out if the manifolds alone are worth the extra money vs gains

chris

[sketchy]

your better off running 2 front manifolds(as they are reversible) fine if running an s54 box, as the axle carrier gets in the way otherwise.

and just make up a y/balance pipe to suit, or get 2 smaller back boxes or straight pipe even if you don't like your neighbours...

[cdwood2010]

Lo My plan for a 3vz mid section was to bring the two pipes down, over the crossmember and into individual back boxes, then add a balance pipe between the two.

I've still got flanges, pipe etc, just haven't got around to it yet.

We originally made this for japscrap.......



Originally named 'frankensteins downpipe' for obvious reasons, it was made using a variety of bits, including some booty from a Kwikfit skip diving session.

Still on there 3 years later.

:)

C.

[thomp1983]

I want to have 2 2" dia equal length downpipes merging into a y with 2.5" dia from there to the backbox, if I keep the stock manifolds then it shouldn't be too expensive I just can't find enough info on if there's much gain from redesigned manifolds

[snowtigger]

There has been a few attempts at v6 manifolds, the gains are probably in 10bhp range the only way is go on the rollers as stock then go back on with a custom setup.

[sketchy]

other than the stupid rear bank manifold, most of the damage to performance is done with inlet design...

going on the rollers will just tell you how much you wasted for a 10HP gain...its nice to know the number don't get me wrong

[thomp1983]

Sketchy are you saying I could gain 10hp from new manifolds and 10hp from better downpipe design or just 10hp overall? £800 for a 20hp gain is quite good value as far as n/a tuning goes

[sketchy]

you could spend a whole lot of money. and still come out with 10 HP.. when you could get a new front bank exhaust manifold and bodge a y pipe, and a low end/cheap ecu, and some dyno time to tune it properly, for a much better gain.

unless your unloading a big bunch of cash, pick things that will return the most improvement for the lowest expense, a billet flywheel for like 300 or so in your money is far better at releasing Hp, then doing the headers...at least it will feel more "alive", front manifolds while not great, at least flow better than the rears, are cheap and just need a modified pipe, little else expense wise.

unless you want a 6 throttle body, fire breathing N/A monster..you wont get all the HP though the exhaust unless you fix other bits too

[cdwood2010]

I still think my 'list' of mods makes for some cheap gains.

K&N air filter (shoved right into the vent)
EGR delete
Hot air breather delete (catch can)
TB heater bypass
Y section replace
Decat

There's no dark art here, all these are well known, but these must add up to +10 bhp, and they're mostly free, or cheap to attain.

C.

[snowtigger]

By the time you've spent all this money it would have been cheaper to just buy a 2gr or swop the 3vz for a 1mz vvti at 220bhp