Pondering about camshafts
Turbo Mini Forums

Lo, basically after some info on turbo cams.

Am I right in thinking turbos prefer longer duration over higher lift? Is that why people don't run 1.5ratio rockers?

I've tried searching etc, vizard doesn't really seem to cover turbo cams that I can see.

Are there any comprehensive books or websites that give info?

Ta

Dave the Cake

Some people do run higher ratio rockers but doesn't that just mean the engine makes its power higher up the rpm?

There is a post with loads of info on cams iirc its by paul s

Most of the cams used seem to be the 274, 266, mg metro, and avonbar ph2 style cams

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Searching is all you need on TurboMinis

Ok, Thanks I'll have a look for that post.

I want to understand why those cams work rather than just knowing what people use.

Dave the Cake

I would suggest first doing some reading about ''normal'' cams, that is quite complicated to start with. A turbo cam could be quite like a normal NA cam(for a very optimised modern design with low back pressure ) or more like the often advocated short(ish) duration & low overlap and wide LCA .

a simple google search for ''camshaft theory'' will keep you reading for a few hours.


As for the rocker ratio's. If you change the ratio you change quite a bit of variables on a cam.

It makes it ''longer'' , at least sort off..not if you define the duration at 0.000000001 micron lift which would be the ''true'' cam duration starting at the first inkling of a opening ramp.

but it will if you measure it at say 2mm or at 0.050'

so you basically stretch the curve upward while keeping the duration including ramps the same .

I made this illustration .. probably more insightful.

It also increases lift on overlap which might be good in some cases , but if you have high back-pressure it could well be rather bad.

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Edited by Sir Yun on 5th Jun, 2013.

That sir, is not rust, it is the progressive mass reduction system

http://aseriesmodifications.wordpress.com/

That's very helpful, thank you Sir Yun!

Dave the Cake

just skimmed this one, but it is readable and not in the 500 word ''all about.. " format so prevalent on the web.

http://www.datsport.com/racer-brown.html

if you are really hell bent on the ''why'' of engines: Prof GP Blair has published a lot of good stuff but it is not light reading.

http://www.profblairandassociates.com/pdfs...k_to_basics.pdf

and yes this is basic compared to the real books..

Edited by Sir Yun on 5th Jun, 2013.

That sir, is not rust, it is the progressive mass reduction system

http://aseriesmodifications.wordpress.com/