What the hell?

[avgas]

That's how it works. By super heating the exhaust gases, it's expands and rushes out the exit quicker, hence better scavenging etc. Were you running the std exhaust? Maybe it was like it had a cork up it's ass hence the over heating?

Nah found that with the wrap all heat was contained in the front near where the headers exited. There is f-all air flow through there so it really needed shiny chrome pipes so that the air passes through there quick and around the block.
Problem was not the exhaust gasses themselves, but more the contained heat in the block and oil. You never have this issue with water-cooled motors, which is why wrapping them probably isn't such a bad idea. But on air-cooled motors its best to leave it to the aerodynamic guys that have a clue.

Also wouldn't you want more back-pressure to increase scavenging? Less back pressure from the exhaust would mean that all your precious scavenged go juice would shoot out asap. Like that time you farted when your boyfriend had blown his load.

[Crasherfromwayback]

. Like that time you farted when your boyfriend had blown his load.

Nah. I made him use a connie. No bare back for me!!!

[steve_t]

Also wouldn't you want more back-pressure to increase scavenging? Less back pressure from the exhaust would mean that all your precious scavenged go juice would shoot out asap. Like that time you farted when your boyfriend had blown his load.

The whole back pressure thing is a misconception. Scavenging is achieved with gas flow velocity. When the ID of the headers is too large, the flow velocity slows and performance drops. Smaller headers can increase flow velocity an enhance scavenging, however too small and you will have a problem with increased back pressure. So, back pressure is NOT desirable. You probably already know this but I thought I'd make sure others aren't getting confused

[bogan]

The whole back pressure thing is a misconception. Scavenging is achieved with gas flow velocity. When the ID of the headers is too large, the flow velocity slows and performance drops. Smaller headers can increase flow velocity an enhance scavenging, however too small and you will have a problem with increased back pressure. So, back pressure is NOT desirable. You probably already know this but I thought I'd make sure others aren't getting confused

Here is a good article which explains wave scavenging as well. Technical stuff on scavenging starts about pg4, but the rest is good background too.

[huff3r]

How cold is that air going to be after its passed through a roasting hot engine bay?? Your still of the opinion that a hotter engine bay is better than a cool one?

Yes. Otherwise a good proportion of the energy from combustion is being used to keep the engine warm. Hence why engines have "running temperatures" and water-cooled engines have "thermostats" to prevent "super-cooling".

As long as the efficiency of the cooling system is maintained, then yes a hot engine bay is very very good.

[bogan]

As long as the efficiency of the cooling system is maintained, then yes a hot engine bay is very very good.

You got it backwards, as long as the cooling system is keeping the cylinders hot enough for good efficiency, it doesn't matter what the engine bay temperature is. All a hot engine bay will do is heat the intake charge and cause detonation.

[nzspokes]

Original tm ad says it added 25kph to top speed.

im gunna do it on Sat.

[Sable]

Don't be stupid. The header wrap wouldn't have done shit. It would have been a combination of straight pipe/pod/weight loss/a tune up and or gearing. IF he's telling the truth. None of these things being worth doing on a CBX250.

[nzspokes]

Don't be stupid. The header wrap wouldn't have done shit. It would have been a combination of straight pipe/pod/weight loss/a tune up and or gearing. IF he's telling the truth. None of these things being worth doing on a CBX250.

Bollocks. There is speed to be had.

[ktm]

Bollocks. There is speed to be had.

You're absolutely right, there is speed to be had. Stick with downhill slopes and tail winds and your bike WILL go faster, gearing permitting.

[Sable]

You're absolutely right, there is speed to be had. Stick with downhill slopes and tail winds and your bike WILL go faster, gearing permitting.

Fit a spinnaker

[nzspokes]

Fit a spinnaker

Your gunna look real silly if my top speed improves.

[sidecar bob]

You got it backwards, as long as the cooling system is keeping the cylinders hot enough for good efficiency, it doesn't matter what the engine bay temperature is. All a hot engine bay will do is heat the intake charge and cause detonation.

Thats a brand new concept, so the cooling system keeps the cylnders hot?? & what keeps the cooling system hot?

[steve_t]

Thats a brand new concept, so the cooling system keeps the cylnders hot?? & what keeps the cooling system hot?

For turbo'd vehicles, it's called an interheater. NA vehicles have an irradiator

Of course he means "so long as the cooling system allows the cylinders to remain at an efficient temperature..."

[jonbuoy]

Yes. Otherwise a good proportion of the energy from combustion is being used to keep the engine warm. Hence why engines have "running temperatures" and water-cooled engines have "thermostats" to prevent "super-cooling".

As long as the efficiency of the cooling system is maintained, then yes a hot engine bay is very very good.

Where are you getting this from?? Are we talking about diesels in Arctic temperatures, a petrol engined aircraft engine at high altitude or high performance/tuned petrol engined bike/car in normal ambient temperaturesl?? Not normally a problem to keep an engine hot enough for combustion. A "hot" engine bay is never a very very good thing for high performance.