Just a random question that will make me sound stupid.

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khaos

khaos

New Member
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Sheffield, South Yorkshire.
I was once told that if your engine cuts out with the exhaust under water, the exhaust will suck in water. I don't see how this is possible unless the engine is also below water but I have never let it stall under water because I was told this would happen. Is this at all true?:confused:
 
back pressure is key to the smooth running of most injuns.Makes ya laff wen ya see chavy types with big bore exhuasts that probbaly rob 5 or ten horse power
 
goonarmy said:
back pressure is key to the smooth running of most injuns.Makes ya laff wen ya see chavy types with big bore exhuasts that probbaly rob 5 or ten horse power
Click to expand...

I know, it's hilarious. Theres an optimum size unique to each engine model. Like the headers and manifolds. It's amazing how much of a compromise manufacturers make when you look at these parts compared to how they would work best.
I feel like an idiot now because I know all this stuff so if I had just used my brain I could work out why it happened. :rolleyes:
 
nathan5346 said:
Fact? :D
Click to expand...
The FACT is no engine likes back preasure, thats a fact, the quicker the gas can leave the engine the quicker the air and fuel can get in, giving better higher rev range performance, what is important is the size/length of the ptimary and secondary exhaust pipes (headers and down pipes) and how they are configard to stop pulsing back to other cylinders.
 
Resonance in two stroke engine exaust =more power.

induction and exhaust design can have great effect on performance.

As lightening ,balancing and porting.

Raised compression ratio's and as much advance as possible without pinking
 
fanatic said:
Resonance in two stroke engine exaust =more power.
Isnt that why they fit read valves to high performance 2 stroke engines?

induction and exhaust design can have great effect on performance.
Very true

As lightening ,balancing and porting.
Very true

Raised compression ratio's and as much advance as possible without pinking
Click to expand...
To much spark advance can decrease reformance even without it deting (pinking) but yes i get your point.
 
Reed valves on a two stroke engine are in the intake for a start, and they're there to stop any mixture being pushed back to the carb. The expansion chamber on a two stroke exhaust is designed to create a reverse pulse back to the engine in order to keep as much of the mixture in the cylinder until the piston rises far enough to close the exhast port.
 
oldskool said:
The FACT is no engine likes back preasure, thats a fact, the quicker the gas can leave the engine the quicker the air and fuel can get in, giving better higher rev range performance, what is important is the size/length of the ptimary and secondary exhaust pipes (headers and down pipes) and how they are configard to stop pulsing back to other cylinders.
Click to expand...
I didnt know thats why i put the ? but now i do know... summat else ive learnt on ere :D
 
On a four stroke you want to provide the opening valve with as much a pressure differential as possible to increase exhaust scavenging. Open headers will provide the best power possible, although good merge collector design can offset some of the drawbacks of merging exhausts by using the flow of gas to pull the exhaust gases from the open cylinder
 
altering the size and length of the primary and secondary pipes will alter the range in which the engine produces it's most useable power, for example F1 teams regularly change manifolds to suit different circuits.
 
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