High vs low mount ex manifold: performance advantage?

[180bfj20det]

Please support for "for and against" high and low mount" ex manifolds with respects to performance advantages.

From what I gather, I do NOT see "flow" benefits from either manifold type as flow is determined by inlet diameter, smoothness and diameter of bends in manifold runners (many other things including pressure but for the sake of the argument lets ket it relatively simple). I know of an associate who claims that low mounts flow better and I do not agree. I have built many ex manifolds and personally I have seen no advantage in either low or high in my designs.

This is not a thread of personal preferences but for performance-only cons and pros of the low and high mount manifolds. So please no "I think", just "it has been proven" or theory to support your opinions.

Cheers

[Sydneykid]

High/front mount is not as good as rear/low mount for weight distribution and centre of gravity.

[Roy]

Well a few observations of my high mount setup. Oil lines are easy to suss, i suspect a low mount to be more awkward to run lines to/from turbo.

Also the dump pipe on my high mount is almost 2x90deg bends to clear the firewall then track the underside of the car....do i increase back pressure with 2 large 90 deg mandrel bends???? Id say bees d1ck difference, but a low mount does have a straighter shot to the backside of the car.

Also with alow mount i dont feel there is as much a need for heat shielding, sure you still got the steering rack etc down there you have to look out for, but my high mount sits lots wiring/bits & pieces next to glowing red steel:( It has taken me a while to get the temp / insulation to a point where im happy..

As for pure performance, id say maybe high mount as it gives you a bit more flexibility with pipe runs/layout...but again i think it comes down to a case by case basis as other factors are likely to influence performance more

[Sumo]

How are you supposed to show off to all your friends with a low mounted turbo??

Sumo

[Cillham]

point to the turbo for them...

[R31Nismoid]

lol, thats what i do... point... the big thing... down there

In all honestly i wish i had high mounted it now.

Everytime something dump/gate/turbo related has to be fiddled with its a 3 day adventure to get it apart.

Where a highmount would cost me no more than around 20mins if i scratch my ass a few times

[Sumo]

ahhhh..... so a high mount is not just for show? its for practicality..

[180bfj20det]

ahhhh..... so a high mount is not just for show? its for practicality..

Yep thats right. It takes me less than 5mins to remove my gt30 (no joke).

[Sydneykid]

Personally I would much rather have the superior performance of a low mount and use reliable turbos and high quality installation so that i don't have to work on them all the time. A well engineered low mount doesn't present much more of an access problem, don't get trapped into comparing a aftermarket high mount with the factory low mount. You really need to compare it to an aftemarket low mount.

The superior performance is there all the time when I am driving it, any miniscule maintenance advantages is only there when I am not driving it.

[otto]

Dont know if this is relevant but i got told a turbo turns heat energy into mech energy. i would have thaught a manifold that kept the turbo as close to the action (exaust valves) as possible (without affecting flow to much) would be better/more efficient, the highmounts i have seen seem to keep the turbo alot further away than the lowmount.

[Sumo]

A turbo works on a flow energy afaik. Heat alone with not spin a turbine.... my understanding is very simple, but the spinning motion caused by the exhaust gases spins the common shaft that has a compressor at the other end.

Cheers

Sumo

[otto]

flow energy?? never heard of it... could you explain how it works!

maybe you should concider whats creating the "flow"

[lwells]

A well engineered low mount doesn't present much more of an access problem, don't get trapped into comparing a aftermarket high mount with the factory low mount.  You really need to compare it to an aftemarket low mount.

Any tips on improving upon the stock lowmount setup for those of us who don't want to go for a highmount? Is it just a question of trying to smooth out the airflow through the manifolds, or should they be replaced entirely, etc etc etc?

Lucien.

[R31Nismoid]

the thing is you cant have a BIG turbo low mounted easily.

Depending on what car etc etc.

But i have all of 3-5mm, yes MM clearance in some areas, there is no "better" way to have designed it as low-mount/stealth is gonna be tight when you gotta fit a turbo and a big eXT gate in there somewhere, combine that with a exhaust dump pipe...

If it was something smaller than a GT30 then yeah, easily.

[Roy]

I havent see too many aftermarket low mounts..the only one that i woudl like to use is the factory GTS-R or the cast HKS jobs.

[lwells]

I havent see too many aftermarket low mounts..the only one that i woudl like to use is the factory GTS-R or the cast HKS jobs.

The Silk Road ones seem to be on Yahoo JP all the time, but I haven't heard any reports of people using them...?

LW.

[Sydneykid]

the thing is you cant have a BIG turbo low mounted easily.

Depending on what car etc etc.

But i have all of 3-5mm, yes MM clearance in some areas, there is no "better" way to have designed it as low-mount/stealth is gonna be tight when you gotta fit a turbo and a big eXT gate in there somewhere, combine that with a exhaust dump pipe...

If it was something smaller than a GT30 then yeah, easily.

We tried a GT30 on the R34GTT mounted to the standard manifold using an adaptor. It fitted in easily. If I remember rightly, Steve on here also had the same on an R33GTST making 300+rwkw. The HPI R34GTT had a GT3040 low mounted on a Croydon's custom exhaust manifold, around 310 rwkw if I recall correctly.

[E_Lu-SHuN]

my turbo is on the stock exh manifold, plenty of room to play with. btw its a gt30 using an adapter to which to ext wategate is connected to.

[R31Nismoid]

but where is the wastegate on them?

I'd be interesting to see

[E_Lu-SHuN]