Bike Carbs on pinto and cvh

[davidimurray]

Ok, just been playing in Excel and got some interesting answers! I will upload the spreadsheet this evening, but in the meantime have a look at the figures below, based around a VE of 0.8

1.8l engine 6000 RPM 18l/s
2l engine 6000 RPM 20l/s
600cc bike 16000RPM 16l/s
750cc bike 13000RPM 16.3l/s
1000cc bike 12000RPM 20l/s

So by my guess - the carb from a 1000cc bike should be ideal, but loads of people use 600cc ones without problems. I guess it probably gives them a very sharp throttle response as opposed to pure top end. The 600 carb should still be able to flow 20l/s but at higher velocities and with a little top end loss.

Cheers

Dave

[Bonzo]

Wow, now that is a lot of science for an old brain to soak up

I assume this is why the Supercharger is the ulimate upgrade.

Nice work guys.

[davidimurray]

uh, oh - now we are gonna get into the age old supercharger v turbocharger debate! The thing with either of these methods is that you normally get a VE value greater than 1, i.e. forcing more air into the engine than it can suck in.

Remember though, that I am just using this as an approximate set of numbers to keep the carbs around their original operating range. You can flow as much air as the engine will pull, but with increased velocities and losses. To really show off I got some pretty graphs for later

[Bonzo]

Originally Posted by davidimurray

uh, oh - now we are gonna get into the age old supercharger v turbocharger debate! The thing with either of these methods is that you normally get a VE value greater than 1, i.e. forcing more air into the engine than it can suck in.

Noooo, we don't even want to go there !!??

It's just the science of all things engine, blows my mind. ( Well what little of it that is left )

After almost 2 years of boring other forum members over engine choice. I have only recently decided to go the Zetec route.

Lots & lots of reading since then.

I can honestly say that as far as modern engines go, I know hell of a lot more now than I did a couple of months ago.

I can still fit it on a piece of A5 paper though.

[davidimurray]

The big thing I find with engine related work is that it is all about care and attention. You need to consider the whole system, no point fitting a ported head with a stuffy air filter! Yes there is a lot of skill and experienced invovled, but if you can build a whole car then engine tweaking should be childsplay.

If you haven't come across it yet look for organ pipe or helmholtz tuning for runner lengths - that confused the hell out of me for a while until I got the chance to actually do some tuning myself.

On that note has anyone played with tuning inltake/exhaust tuned lengths?

Cheers

Dave