Short duration cams generally make a turbo car more responsive, thats deffo correct as Karl said so a few weeks back on a thread.

But does it move the powerband compared to identical cams that had much longer duration (and hence overlap)?

Say there was an engine running a T4, one car had high lift and duration cams, one had high lift but low duration cams in, the low duration one would have better responce, but what about the rest of the cars characteristics?

Would there be a difference in peak power revs?

And so on...

 

its also about where full lift is timed (therefor how much overlap)

duration and lift dont tell you everything

 

Stop making things complicated you bastard, i hoped for an answer to help me not confuse me more than ever

Lets say theres very little if any overlap on the high lift low duration ones, but plenty on the high lift and duration ones then...

On identical "RS500 spec" engines.

Has one got a higher peak power revs than another?
The low duration/overlap one has better throttle repsonce, but whats the differences in power/torque throughout the revs compared to the high duration/overlap one?

 

 

Good man rene

BTTT!

 

you owe me one

let me have a go on your missus

 

she jus come back from family holiday actually, foooook me she looks mint, im at work now but shes waiting round mine, soon as me niece comes back from the seaside im gonna rob her digital camera again and do some more pics

she was naturaly really tanned before, even better now, sorta 'beyonce' brown, jus about right, me like, lots



ANYHOW, the cam question, anybody?
Does everybody have aftermarket cams in their car and honestly not know how cams alter the cars characteristics???

 

its stil a hard queston for me to answer and im sure ill be shot down

advancing the cam timing will increase low and mid range torque at the expence of top end power! and a longer duration cam will give you a smaller powerband

 

BTT for Stu/Karl, someone, then

 

not having much luck ey steve ?

 

I "think" I know what you're trying to get at, and yes, the cams just move the power band around. Don't forget it is turbo dependant as well...

For example, my normal (ish ) RS500 Sapphire spec, the power band was 4000 - 8000 (with no significant drop off in power - 1.5bhp from 7000 compared to 7500 ).

My new engine is specced completely differently, as I wanted response over outright power (a sacrafice I am glad I made after driving my old car recently ) and the short duration cams in it now give a power band of 3150 to 7000 (whereafter the power does tail off by 7500 by 25bhp and 40lb ft). And there is absolutely no point in revving it beyond this, as power is dropping like a stone from 7500 onwards (in fact it is rev limited to 7750 soft cut).

 

The idea of long duration is to an extent overcome exhaust back pressure - they work well with restrictive turbo's - allow them to rev more as u are keeping the exhaust valve open for longer allowing the gases to do one. Problem is, at low rpm. the gas is moving slowly - it's coming in through the inlet valve and going straight out the still open exhaust valve without getting combusted. Thats why u get lumpy idles and poor low down torque. Would be really nice to implement a VTEC system on a binliner/YB

 

just ignore me then steve

 

Gareth- you didnt really answer my question did you, lol.

Mike just blithered on like a feature on his car with no help at all tho

Rick helped a bit tho...

Say long duration isnt particularly important due to big big turbo, the shorter duration will help low down, but i take it providing the ex housing isnt causing tons of backpressure, there would be no significant sacrifice in peak power by using short duration rather than long with lots of overlap?

I guess the longer duration would bring the powerband higher too.

 

Anybody else? (Apart from Karl as he obv dont like me as seems to ignore any of my questions, pmsl )

Compared to shoter duration (if all else is the same, and the turbo isnt the restriction) long duration/overlap will give less responce and low down power, but would there be a significant increase in peak power if theres no bad amount of backpressure even with low duration/overlap? (Id guess NO)

Same situation above, will peak power revs be any different in the 2 cam setups?

 

I give up, lol

This at least shown people dont know as much as they seem to think they do (wheras ive never had a fookin clue bout cams really, and using this thread to try and learn...)

 

Lairy cam timing = massive penis....

 

Up for steve as this is obviously a matter or life or death

 

I still read this site but chose not to post due to all the hassle I've had in the past.

 

Karl you little bugger, I saw your name and thought, aah, can see what Yoda thinks - don't disappoint us please .

 

"karl you little bugger"

POT, KETTLE, BLACK

 

Okay, Karl you littler bugger - go on, share, share, share .

 

it would be a real big shame if pf lost your input karl.

 

Cheers paul, err, cheers, karl

Not life and death, jus want to learn about cams, as ive no clue, and from what been gathering, a lot of "experts" (not on here) who give cam advice dont understand em either...