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Discussion Starter · #1 ·
At long last my adjstable cam gears are on their way from Swedeland
I will be setting them up on a rolling road but does anybody have any good links into the theory so I could point them in the right direction...?
 

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Only don't got too far and bounce the valves into any other fast moving objecets...

A few hand turns on the engine for clearance and a good ear on accel and overrun...

A
 

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Please don't tell me you are going to be guessing on which way to position them

You need a accurate dial gauge and crankshaft degree disc and someway of getting the dial gauge tip to locate onto the top of the hydraulic follower to measure lift in relation to crankshaft angle. The cam specification can then be accurately checked in conjunction with crank angle.
Although not to much of a problem with low compression engines, high lift cams need the piston to valve clearance checked also to ensure adequate clearance.
Good luck!!!
 

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Discussion Starter · #4 ·
I do not intend to do this myself !!
My question was when it comes to extract the final 50 hp out of the engine I need to look at overlap,cam duration and timing
I have done some surfing but all I can find is for n/a engines good stuff but I think the rules are different for forced induction
 

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Originally posted by ylee coyote:
[qb]I do not intend to do this myself !!
My question was when it comes to extract the final 50 hp out of the engine I need to look at overlap,cam duration and timing
I have done some surfing but all I can find is for n/a engines good stuff but I think the rules are different for forced induction [/qb][/b]
The thing that I think should be understood about tuning turbo cams compared to N/A cams is that if your cams are a little restrictive you can usually raise the boost to compensate. The problem comes when more boost generates too much heat and the engine reaches the detonation limit. Better cams reduce the heat in a number of ways.

As I understood it, the difference in the ratio between exhaust pressure and intake pressure is the primary change between N/A and turbo in regards to cam tuning. The secondary difference is generally a lack of exhaust tuning due to a much higher EGT and thus higher pulse-speed. The intake runners are still tuned about the same as a N/A car because the temperature is not so drastically different.

Usually the purpose of cam gears is to change the overlap to match the exhaust/intake pressure ratio; too much overlap and exhaust gasses reverse back into the cyllinder and even into the intake system. Too little valve overlap and you're not evacuating as much exhaust gas as is possible. The knock limit goes up a great deal as heat is removed.

Every uniquely tuned turbo engine will have a slightly different exhaust/intake pressure ratio during valve overlap.

Adrian W~

p.s. When playing with cam-gears the pulse-tuning has no, or very little, effect as the pulse-tuning depends on duration and not cam-angle.
 
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