[Fatzook]

hooki wrote:

MacBear wrote:

hooki wrote:

whats the ideal exhaust size for a 1L (f10a) with extractors?

I would say... 1.75in !

Yeah? i geuss as long as it provides enough backpressure for the 1L so it doesn't loose all it's low down

I'd say 1.5". Or stock size. 1.75" is more likely to make it drone.

[dunewalker]

leave the cat on - just hollow it out!

[jmd-247]

dunewalker wrote:

leave the cat on - just hollow it out!

this is what i have done.

[TASSIETOYUKI]

jmd-247 wrote:

dunewalker wrote:

leave the cat on - just hollow it out!

this is what i have done.

Um.. gutted cat has worse flow rate than than one with the internals due to exhuast gas expansion

[MacDaddy]

Gwagensteve wrote:

MacBear wrote:

Its about maintaining enough restriction... right pipe Diameter, and right length, while still having a higher flow exhaust

After a few inches downstream of the extractors collector, there's no such thing as "maintaining enough restriction"

Extractors are designed to match the exhaust pulses from each cylinder so that each pulse arrives at the collector separately. After that point, any scavenge effect from pulse timing ceases to exist, and the point is about getting the gas out as fast as possible.

The "required restriction" or "backpressure" exists between the head and the collector. after that point, backpressure is lost power.

This is not necessarily the case with log manifolds that aren't equal length, where removing backpressure might reduce scavenging.

I'll just reiterate - downstream of a turbo or the extractors collector, backpressure or restriction is not "required"

Steve.

If this is true, then why have such a long exhaust pipe ?
Dragsters have a very short pipe bcause they work mostly in the very high RPM, but would be gutless at low RPM... so even though, if you have a better higher flow exhaust put on, you still need to have a longer pipe, to try and maintain the power at lower RPM, while increasing power at High RPM, so the length of the pipe, and the bends in it, add restriction !

[Proxy]

Gwagensteve wrote:

MacBear wrote:

Its about maintaining enough restriction... right pipe Diameter, and right length, while still having a higher flow exhaust

After a few inches downstream of the extractors collector, there's no such thing as "maintaining enough restriction"

Extractors are designed to match the exhaust pulses from each cylinder so that each pulse arrives at the collector separately. After that point, any scavenge effect from pulse timing ceases to exist, and the point is about getting the gas out as fast as possible.

The "required restriction" or "backpressure" exists between the head and the collector. after that point, backpressure is lost power.

This is not necessarily the case with log manifolds that aren't equal length, where removing backpressure might reduce scavenging.

I'll just reiterate - downstream of a turbo or the extractors collector, back-pressure or restriction is not "required"

Steve.

i'm not saying anyone's wrong, but i had sporty muffler on my Astra, extractors no resi and just the muffler, i put a hole in it, put a stock one on and it went better, had more low down torque first take off i span the wheels outta the exhaust shop,

i assumed and was subsequently told it was because i had better back pressure

[Rockhopper]

Asked for a 2" from the cat back on the Jimny, but I'm sure it's actually bigger than that. It looks more like 2.5". Car goes great, and when engine and exhaust is cold it sounds good too, but once things get hot (like going on a long drive) Holy Shit!! you go deaf. Am gonna have to take this back to get it sorted next week.