i need your input to understand!

26th July 2006, 16:46

Ok guys, as you may know i am the kinda guy who loves technical info, the reason i like this is so i can understand how to best mod my engine! Recent discussions on SSC has led me to simply go down the CAM & remap original ECU, with a gearbox that suits (probly a GTI box) route, but along the way strengthening everything i can afford to, to keep it reliable. I have thought about strocker kit - turbo - supercharger - throttle bodies, the reason i want to simple add a cam is that she needs to be reliable all the time & at a reasonable price.

My question to you is what the hell does all teh info about cams mean.... ie lift? duration? inlet? exhaust?... 270 degrees? 285 degrees? how is this relivant to performance of teh engine!? can you please put up info so i can make a good choice of cam for me, be it custom ground or off the shelf i want the rigt one for me. waht do i cant from it? mid range torque....

can you help!??

26th July 2006, 16:50

mate i can't help you here but im intregued to know too! o but i can help you with your spelling, its THE not TEH ok!

:Y:

26th July 2006, 16:57

please try & just put up relitive info i want to keep this thred to "the" point. LmBo...:Y:

26th July 2006, 17:18

Ok, the standard cams are designed to be everything (but fail at almost all). They have been optimised to work most effective at a certain rpm (usually around the peak torque of the engine), this means they are usually pants at high rpm. This is because the cam usually closes the inlet valve too early when more air could in theory be sucked into the cylinder and opening of the fuel inlet is not optimised for high rpm (thats a basic example).

With the aftermarket cams they usually prolong the opening duration of the valves in order to provide a longer flow rate of air into the cylinder. Another way (although potentially damaging to the valves) is to open them further allowing less of a block at the entry into the cylinder. this also means that the valve comes out beyond the engine manufacturers tolerance which could result in the cylinder bashing into them (unlikely but its when a numpty has made a home made cam or something - joke)

The other thing is the timing of the opening and closing of valves (and this is where i forget which way round it is), either...
and at high engine rpm you want the opening and closing of valves to be retarded/delayed against standard timing (i think

)
this provides better burn for the fuel and prevents under and over fuelling.

what out for your emissions though

26th July 2006, 18:25

right ok u understand that so wot is this 270 & 285 degrees about then!? the degree figure goes up & that indicates wot!?

270 degree cam does wot over standard one?
285 degree cam does wot over standard one?

can i get the best of both with a custom ground cam!?

26th July 2006, 18:36

I'm starting to venture out of my knowledge boundary but the 285deg sounds like it offers a LOT of valve overlap (between the inlet and exhaust valve)

from what i know 'sport' or 'fast-road' cams adjust the valve to create a valve overlap that basically gives you much improve air induction at higher speeds.

remember that with an improvement in top end your bottom end will suffer quite a bit. so slowish driving in high gears will be crap.

the 270deg sounds more like a Fast-road cam but with less valve overlap, bit better allrounder than the 285 but less power in the top end

hope that helps

26th July 2006, 18:37

so to simplify:

270deg is a 'fast-road' cam - aimed at improving the top end without messing low end too much
285deg is a 'sports' cam - aimed at top end (oh and you'll probably get bummed at MOT time)

26th July 2006, 18:39

Quote:

Originally Posted by WestyVTR

can i get the best of both with a custom ground cam!?

You gotta be bloody careful messing around the timings and such - i doubt (unless you have BIG money) a custom cams would be viable.

26th July 2006, 18:57

Quote:

Originally Posted by adsayer

so to simplify:

270deg is a 'fast-road' cam - aimed at improving the top end without messing low end too much
285deg is a 'sports' cam - aimed at top end (oh and you'll probably get bummed at MOT time)

MOT will be ok im sure of that

you must be able to get mid range torque cams!? One sthat improve performance say at 2k up to about 4.5kish or along those lines Hmmmm..... or am i wrong?

26th July 2006, 19:00

Quote:

Originally Posted by WestyVTR

MOT will be ok im sure of that

if you say so.

with the 285 valve overlap you get part of your unburnt fuel passed into the exhaust which then burns along the way increasing the emissions badly.

Plus you wont be getting loads of benefit in just having that whacked in, everything else will need to be modified to suit the cam. I'd go 270 personally.

26th July 2006, 19:02

Quote:

Originally Posted by WestyVTR

you must be able to get mid range torque cams!? One sthat improve performance say at 2k up to about 4.5kish or along those lines Hmmmm..... or am i wrong?

yeah they're called 'standard cams' dude lol.

Not sure really, i've heard of mild cams that pretty much have the same timing as a standard cam but have more lift (hence more fuelling) - which would provide the extra torque in the mid range

26th July 2006, 19:32

as adsayer has said. cam spins round in lobe, more lift as the valves go in= more air and longer duration the valves are open longer=more air. as the degree goes up the opening times extra are longer so more air is entered and your idling gets worse. as for mots i woundnt worry unless there 300 degree

26th July 2006, 19:39

so could you in theory add in a 270 degre can and get the ecu mapped to siut it but make more power in teh mid rev range ot not!?

ive emailed kent cams for advise also

26th July 2006, 19:54

dont think so. the map is gonna change your ecu to run with the new mods, the cam is gonna say wherever the power is. you wanna check kent, piper and catcams on the same cam and see where there peakpowers are. i dont know what the cam profiles are for vtrs but on vts's you peak gonna be 4-7+ revs. i take it you will have your rev limiter higher?

26th July 2006, 19:54

every cam has a power range, you cant have power and torque throughout the rev range you have to compromise, only where you get both is turbo with lary cam and throttle bodies.

so mild cam, 270degree and not much lift will give good pull from low down, good midrange but not fantastic up top, 280 with higher lift will lose low down, and pull from midrange to top, then you can go furter and have nothing before 5k and a screamer afterwards, but its not that simple as a less duration cam with more lift can give more mid than a one without, but you have to decide what you want then go from their, then design the exhaust and airfilter system so that you get what you want out of your cam (not the other away around)

26th July 2006, 21:20

Ah ok i see, i have a 4 branch & straight through exhaust, with a BMC filter, so a 270 cam would suit i know it should be the other way around but its done now... my bad! & with a closer ratio box, that would work well if the 270degree cam? as it pulls well from low down & midrange.

i will contact piper & catcams to see what is best for what i want waiting for kent to get back to me already.

27th July 2006, 16:27

spoke to john (GMC) earlier today, the idea will be to save up for a new engine an early silver top (say £400 max) then add the cam into that as well as strengthen bits & bobs while its out before pluming it in with stand alone managment advised so then it is flexible depending on where i go with it....

the cam choice will be finalixzedwhan i have the low milage engine....

its strange you seem to have adea of where your going but after listening to ppl who know there stuff your route changes... its all good tho...

27th July 2006, 16:35

what other bits and bobs are we taliking about aswell, you dont wanna get talked into a new engine., unless yours is fucked. its all money, engine in and out is not cheap.
if you do, dont you dont fancy chucking a vts engine instead.