Exhaust Manifolds

[Bronx]

hello, was doing some searching about exhaust manifolds on here, but got nothing i wanted to find.

my question is, im looking at replacing my original rb25det turbo manifold fomr the NEO engine,

since i want to keep original dump pipe etc, what manifold do i need??? my guess is low mount manifold, but will it all sit back the way it was????

im just looking at a bit better spool up and ive seen a couple of different manifolds which im interested in, just waiting to hear on the length of each cylinder pipe.

i will calculate what manifold is better for low down rpm.

so is the low manifold designed to keep stock stuff on???

i just dont want to sell my new downpipe to get one that fits the new manifold.

thanks

Jean

[.WILKO.]

i heard there is minimal to no gains to be made on the neo from aftermarket low mount manifold, if you was going highmount yes,

i have r34 gtt built motor, 3076, all supporting mods and stock manifold last dyno was 311rwkw with wheel spin (with amount of camber i have we couldnt eliminate the wheel spin) on 19psi

[zebra]

Leave it stock, nothing wrong with them. ZERO gain to be had by going to a tubular manifold unless you want to spend 2K on a genuine HPI one.

[Bronx]

ah, well thats cool then, i wont worry about a new manifold untill after my rebuild. so i guess ill get to buy something else first.

[Bronx]

actually, just a quick question, this has been bugging me for a loong time.

the so called turbo manifolds and extractors, which would be more efficient at quick spooling????

the manifold or the extractor???

if you think of it theoretically, the spool time depends on how fast your exhaust gases can get to your turbo.

say the stock manifold is set up like this:

cylinder 1 is a 20cm pipe to turbo, cylinder 2 is a 6cm to turbo, cylinder 3 is also 6cm to turbo and cylinder 4 is 20cm to turbo.

that means the shortest exhaust gases will come from cylinder 2 and 3. to travel the 6cm, means short turbo spool or turbo lag.

while with a mandrel bent extractor, cylinder 1 will be 25cm, cylinder 2 is 15cm, cylinder 3 is 15cm and cylinder 4 is 25cm. it means it will be able to get the engine to run more freely, but it does not guarantee a faster travel of the gases to the turbo, so higher up you should see a bigger increase in engine power, 15-30hp on a basic extractor. but therefore a bit longer turbo lag from the longer gas flow. gas travels 6cm in the manifold and 15cm in the extractors.

while this is not the case for NA cars since they dont need to run a turbo, they would benefit from it alot better.

so is this really the case when buying extractors???

would the turbo lag be increased but the overall power gain in the higher rpm???

[TiTAN]

turbo engines dont have extractors, they are for NA and supercharged cars.

tuned length manifolds are more wank than result.

lag does not differ much from a log style stock manifold and a nice tube one, especially on a small turbo.

[Bronx]

well extractors is anything non original manifold basically, it extracts your gases, tuned length, manifold is just the basic crap you get on your stock car, NA or turbo. well from my view at least.

but say you popped a t45 or t66 on there, a top mount, that should kick your lag in to well over 4k rpm.

[R31Nismoid]

gas travels 6cm in the manifold and 15cm in the extractors.

You have one manifold - It's being forced out, not extracted.

There is a difference.

A stock RB25 manifold seems to be good for around 300rwkw.

I remember back when Joel (Cubes) and others were playing around with a 25/30, 300rwkw of flow seemed to be about the limit airflow wise with some gains had by changing.

So that said, anything 300rwkw or less - spend the money elsewhere.

That pretty much covers off 99/100 set-ups nicely. And the cost of a good manifold is basically a full car of pad/rotor/fluid/lines in terms of a brake upgrade... Something you will notice a lot more

[Bronx]

yeah, will be opting for a nice k-sport racing front brake kit. i prefer being able to get the car to a stop than to high speed

[tridentt150v]

There was a table of test results for manifolds kicking around. I think it was bench flowed results, it would be a bit dated now, but it was good because it had back to back tests in it.

The HKS cast low mount came out best overall, but I'm sure some of the well built ones like 6boost etc would be just as good these days [not sure if they were around when the tests were done?]

If you searched you could probably still find it, think it was on a UK site but may have been an NZ test?

[rad100]

are stempipe merge collector tune length manifolds the ways to go?

i have a built 25 with 3076r, 50mm gate.

[zebra]

No such thing as tuned length exhaust manifolds for turbo cars.

the name is a gimmick used by Egay vendors to make it sound like they know what they are talking about.

[rad100]

so a 6boost unit would be one of the best to go for?

[ClutchBurndout-:(]

HPI manifolds can handle 2 of the big ones, so its not wasted money.

[tridentt150v]

so a 6boost unit would be one of the best to go for?

Their adds used to say lifetime warranty ??I think?? Look one up in HPI/PI magazine etc so i guess they are a good thing