View Full Version : Cam question
vts_saxo
05-06-2006, 13:56
Would 280degree cams require solid lifters or double valve springs?
the f7s have double valve springs anyway mate...280s would be about the limit for the hydros i would imagine. quite possibly be better off with solid lifters .
Think it's lift & rpm more than duration that gives the lifters a hard time. Up to about 10.5mm should be ok, any further than that and you need Mechanical.
nah, if your not going to above 7500-8000 rpm i wouldnt even bother thinking about solid lifters. They wont pump up below that.
all very interesting!
not to hi-jack col BUT... :wink:
what deg of cams is best suited for f7r's which are mildly tuned. i.e for fast road and track use. most people seem to say 265deg or so...
(BenR recommended me 262deg ones, but also said that the quoted figures aint always right. i.e 276deg cams may not have a duration of 276deg! nick @ hillpower swears by pipers 265deg for fast road use, but piper also do a 276deg etc etc)
so what is optimum....
obviously you can go too wild, but also too tame...is 280deg not a bit excessive for running std bottom end? will it not be reaching peak power just at or after the 6.5k limiter?? ideally do you not want the "main" power band to be between say 4k and 7krpm? no point fitting excessively wild cams if you cant utalise (sp) them properly?!!
also are stiffer valve springs required/recomended to stop valve bounce with aftermarket cams?
i find all this stuff very interesting but there is soo much bullshit, lies and cans of worms when people start speaking about aftermarket cams, their respective durations, lift and lobe sizes! :roll:
Righto, in a brief summary.
What you are trying to achieve with cams is simply to lift the valves off their seat.
Where it becomes confusing is when you read cam specs, as that gives VERY little info in reality as to what the exact graphed profile of a cam is.
For example, these two cam graphs are for EXACTLY the same advertised specs, but what you get as a result is very different.
http://i13.photobucket.com/albums/a300/BenRAWT/camdemo1.jpg
http://i13.photobucket.com/albums/a300/BenRAWT/camdemo2.jpg
What cam specs dont tell you, especially UK ones, is how they measure the 'timing'. In the states its set at 50 thou lift points, so this eliminates the ramp of the cam as it takes up cleanrace over a long period and gently bring the lifter onto the flank, where it wips it open.
What your trying to achieve is maximum time off the valve seat at as high an average lift as possible. So peak lift numbers mean little aswell, its only a rough indicaiton as to how long it spends around those lift levels. Which is why 2 cams can have the same 'specs' but the amount of time that the valve will effectively spend off the seat are totally different, and so is the position of the valve at relative crank positions, due to one profile being able to accelerate the valve quicker.
And this is where new cams vs's reground cams comes in. To regrind and alter a profile they take material off the bottom of the cam, the only circular part, called the BCD (base circle diamter). When this is reduced it reduces the amount of control you can have over the acceleration and decelleration phase of the lift curves. A larger BCD can control the valves opening smoother, and accelerate faster whilst keeping control. And because of this, you can reduce valvetrain harmonics, and especially spring harmonics. If you setup a natural frequency of a spring it will cease to operate as a spring, but rather vibrate in its own right.
Dual springs are used to counter the harmonics by having 2 springs with differing natural resonant frequencies, effectively absorbing the energy from one another. Good dual springs are also interference fit so the inner and ourter springs are always touching, acting as a dampener.
The whole science behind cam design is very intense.
Some companies quote stupid figures using the geometrical data, or when the profile 'technically' approaches the lifting phase, although no actual change in valve posision can be measured. It makes them sound alot wilder than they actually are, and misleading.
Shrick are a good example for non UK companies........where thye advertise 286 or somethins for the clio 172/182......idles on a stock management setup....i couldnt get a bastard 275/268 mix to idle on the stock ecu. Take what you want from that, but the engine only 'sees' what the valves are doing, it doesnt care what the cams are doing or supposed to 'measure' upto.
Optimum for the willy engine isnt a wild one where it upsets the MAP signals to the ECU so that the slow responding ISCV doesn have a hard time. This can be dialed out with cam timing to an effect, but its not the way you should be dealing with cams, they should work from their advertised install timing positions. I'd say power comming in from 3000rpm was ideal, to 7000-7200rpm for a stock engine. If you peak power too late, then your just loosing out on torque and the rpm the cam comes 'on', because people still carry on driving past peak power until the ratio of loss exceeds the ratio of gain.
Very informative Ben - cheers!
So around a "true" 265deg profile cam is more than enough for a f7r. is there advantages of running.....
e.g
piper - inlet 276deg, exh 276deg, 10.87mm lift for both inlet and exh
over
piper - inlet 264deg, exh 256deg, 10.34mm inlet lift, 9.90mm exh lift
thats the problem, you'll never know a 'true' unless you see a graph lift vs degrees.
Your first combination sounds too wild to retain any idle quality.
My valver has some 275 *supposedly* pipers in, and it idles rough....you have to leave it for a few mins until a certain idle pattern occurs, or it'll stall even when hot. weird
ahhh!
is yours running std management with a modded map ben?
cheers for all the info. col you have hav the thread back now.... :wink:
how did you generate them graphs ben ?
Dont supose you can done one for a stock F7R and a Kentcam powered RN2002 F7R ?
you would only get one graph mate....
the std f7r one!
the kent cams graph would just say "BANG!" :wink: :wink:
heeheee, true.
Im going to prove them all wrong though :wink:
Saxo, what are you doing with the engine first, because if it's just cams and remap and not TB's or some form of forced induction, then 280 duration is just far too high. 265 should be about the limit imo, 270+ has never performed well on the F7R engine due to the power coming in as you change gear... or worse, not at all lol. If your building some sort of forged bottom end you'll be okay I'd imagine, but for standard road use around 260 you should be looking at and they are fine for OE lifters.
vts_saxo
07-06-2006, 13:39
Was only thinking about them, would do induction/exhuast first. I ran catcams 708's (about 270degree)in my vts with full exhaust and induction and it ran ok(slightly rough) on the standard ecu when they were just fitted.
Was only wondering if you needed solid lifter and up rated springs for 280's.
Not modding the willy now, getting new project.
Can any one tell me if i'm right here, I'm just quoteing a conversation I had just today.
F7R - Williams 262 deg. (true) duration Inlet 9.2mm lift
F7R - Megane 258 deg. (true) duration Inlet 8.9mm lift
Any one confurm
Can any one tell me if i'm right here, I'm just quoteing a conversation I had just today.
F7R - Williams 262 deg. (true) duration Inlet 9.2mm lift
F7R - Megane 258 deg. (true) duration Inlet 8.9mm lift
Any one confurm
looks about right mate from wot i remember from measuring....actual figures are in my workshop.
1.8 16v are somehwere in the middle.
Williams cam durations are 256 and valver even lower iirc... they used 260+ on the F4 series
i that sounds rite jesus.
no way a std willy cam duration is 262deg, as there would be sod all point buying aftermarket 265deg ones then! :wink:
hmmm i was just looking at lift values! :oops:
you would only get one graph mate....
the std f7r one!
the kent cams graph would just say "BANG!" :wink: :wink:
lol will look like my std cam graph then!
Stew_punk,
Was refering to measured duration, not true valve duration :wink:
As with the map trouble when running greater overlap. Any one try'd restricting the aperture to offer a slight damping effect (little rude I know) If you kept the effected volume as small as possible it might not effect the resoloution too much?... Just a thought
I have thought about it...never tried it.
or a reservoir/chamber to act as a damper...but my thoughts were the increased vcolume would lead to slower response.
**** it and get an after-market ecu was the end solution for mine!!
lol the whole measured duration versus actual duration is already casuing problems!!
What cams would you get then instead of kent?
Catcams?
Kent cams really that bad then? I've heard alot of people have had trouble with their pulley's....
The cams rubbish too?
do catcams do everything needed to do a cam upgrade?
and more mate, and more..... :D
vts_saxo
07-06-2006, 22:24
do catcams do everything needed to do a cam upgrade?
Fairly sure catcams do the lot, very cheap compared with kent/piper
I have a full price list in my workshop if u want specific prices.
springs/collets etc do work out to be cheaper than piper/kent, and they are better quality.
my conrods are from Catcams also, if u were wanting bottom end components.
I have a full price list in my workshop if u want specific prices.
springs/collets etc do work out to be cheaper than piper/kent, and they are better quality.
my conrods are from Catcams also, if u were wanting bottom end components.
If you could price up whats needed for cam in a f7r that would be great...
I saw there stand at FCS but the lass needed a piss and wouldn't let me look lol
Gemma? was she fit...?i speak 2 her everyday just about...she sounds luuuvvvvly...but never met her :cry: so please...tell me...is she fit??!
as for wots needed...wot spec are you thinking of?
Gemma? was she fit...?i speak 2 her everyday just about...she sounds luuuvvvvly...but never met her :cry: so please...tell me...is she fit??!
as for wots needed...wot spec are you thinking of?
he means "his" lass i think! :wink: :wink:
is she fit?? :P
i was on about HIS lass........ :?
:lol: :lol: :lol:
not very clear there eh!!
I took em both in the end those portaloo's are suprisingly roomy :wink:
Clio_GTT
21-03-2007, 19:50
which catcams would be best for a std meggy bottom end on a 16v head ?
5502225 ? or a custom profile ?
Stan, BenR ??
Clio_GTT
21-03-2007, 20:29
yes
any ideas on the cost of them craig and a price on their pullies
Cams retail at £384+vat, and pullies £170+vat.
Thats for all grinds up to the ones which require solids, then they are £434+vat.
Whats your fitted price for a catcams set up? I'd be off for a chipwizards remap then :wink:
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