hobbsy
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| posted on 16/7/10 at 08:07 PM |
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Yam R1 (5PW) Kent cams - power/torque changes how?
Gents,
As you may have read I'm thinking of turbo'ing my R1. However the more research I do the more I realise its going to take a while to do.
So in the meantime I'm considering fitting some Kent cams I have in my pile of bits and leave the turbo conversion til the winter or so.
They are YAM11's, so the spec is:
Application Power Band Cam Lift(mm) Valve Lift(mm) Duration Timing Full Lift VC (mm) LTDC Required Parts
Race N/A I 8.07 E 8.63 I 7.87 E 8.38 I 252 Deg E 252 Deg 22/50 50/22 I 104 Deg E 104 Deg I 0.20 E 0.25 I 2.58mm E 2.75mm N/A
Smeg - that didn't paste very well, anyway if you do a search on www.kentcams.com for YAM11 you can see it on a table (I can't put a
direct link to it unfortunately).
Anyway I don't really want to gain 10bhp for the last 2000 rpm if it means loosing 10bhp for from 4000 to 9000rpm say as mid-range is still
important to me for driveability as I use the Fury on road as well as track.
I'm hoping they won't reduce the total "area under the curve" if that makes sense.
I believe a certain amount of where the power comes in can be altered by how you time the cams?
I've heard conflicting reports ranging from "they are the best thing you can fit, even without other modifications you'll see about
15 to 20bhp" (from someone claiming to have been involved in BSB) to "don't bother they'll give you a bit more top end but
kill the mid range".
Anyone got any experience of these?
I've got some adjustable (Fallicon?) cam gears so I can get them timed in how I want (I believe that is already possible with at least the
intake cam but I don't have them in front of me to check).
[Edited on 16/7/10 by hobbsy]
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carpmart
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| posted on 16/7/10 at 08:37 PM |
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I'm no expert on R1's but think logically about cams. In effect what your doing with higher lift/longer duration cams is compromising
performance elsewhere to have them allow more mixture in. This in turn has to mean that they are closed for less time so mid range punch gets
reduced. In my experience you can't avoid this with lumpy cams!
You only live once - make the most of it!
Radical Clubsport, Kwaker motor
'94 MX5 MK1, 1.8
F10 M5 - 600bhp Daily Hack 
Range Rover Sport - Wife's Car
Mercedes A class - Son's Car
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hobbsy
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| posted on 16/7/10 at 08:40 PM |
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Well that's the way I've often thought cams are, they just allow you to move the torque around and if you put it higher up the range that
by definition means more horsepower but the midrange could suffer. Hence my reference to area under the curve etc.
I stand to be corrected though! There must be some changes you can make that don't hurt elsewhere?
Although I guess the usual argument is that Yamaha have already tuned it within an inch of its life etc etc...
Again I stand to be corrected!
[Edited on 16/7/10 by hobbsy]
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matt_gsxr
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| posted on 16/7/10 at 09:14 PM |
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I don't know about R1, but I have some Kent Cams in my gsxr1100.
The idle isn't what it was so it has to be a bit higher (1100 instead of 950) to be happy. But to be fair I changed a whole pile of stuff when
these cams went in (ported head, bigger valves, higher compression, overbore).
Its difficult to say whether it makes more power with these cams, but it definitely uses more fuel!
Matt
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britishtrident
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| posted on 16/7/10 at 09:21 PM |
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With cams that are not too hugely wild the over lap i.e. the period when both inlet and exhaust are open is what has the bigest effect on low-meduim
speed torque.
More over lap more top end power but less medium speed torque.
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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