custom cam

[CMF_frank2]

being a little disappointed with the piper ultimates, we,ve attempted to better them, twas a mission tho !
it,s got the same opening/closing times as stock (@ zero valve clearance) of 30/75/75/30, but gives 1mm of lift in 10deg instead of the stock one taking 30deg, (which i think gives a duration of 265deg), and we,ve now got 10mm of lift, and it,s been mounted into my 2mm skimmed head

 

[CMF_frank2]

2nd pic

 

[CMF_maat]

keen to see dyno figures of before and after

 

[CMF_frank2]

maat

i will only get an "after" run i,m afraid, but it should give some idea eh.
all of my mods have been to done improve the midrange, ie 1.6 t/b and injectors, almera airbox and ducting, 4kg f/w, this inlet cam and piper ex cam, 11:1 c/r ported head, reworked exhaust manifold and 2nd decat, and hopefully it will have the same grunt (@ 2 to 5000) as a ga 1.6, but the ally 1.3 block and the 1.0 g/box etc is far lighter tho

 

[smidge]

thats impressive... you reground them yourself?

 

[CMF_frank2]

cheers smidge

only the inlet one, and it took me about 15hrs !! of testing the timings in and out of a head to get right
(every other lobe first, so as to match the opening/closing with the uncut lobe)

frank

 

[CMF_SSUK]

I'm not quite sure I fully understand your timings Frank. A 30/75/75/30 cam setup would have a duration of 285deg, on both inlet and exhaust. However you said you have only modified the inlet cam? This would give you a theoretical timing setup of 30/75/62/30?

It would have been very interesting to see a comparison.....but it will also be interesting to see the results with those choice of timings.

 

[CMF_frank2]

ssuk

i believe the industry standard for cam timing is @ 1mm of valve lift.
so i think the stock cam at 222deg is about 45/0/0/45 @ 1mm lift.
my measurements at 0 lift (or 0 valve clearance, tbh, i used a 3 thou feeler) were at about 75/30/30/75 on the stock cam, and the cam takes a further 30deg to open/close the valve 1mm.
and the reworked cam has the same 0 clearance opening/closing times, but opens/closes the valve a lot faster. (10 deg, not 30 deg)
but yeh, with 1 cam done, efectively it,s maybe 65/20/0/45 ?

frank

 

[CMF_frank2]

maat WROTE:

"keen to see dyno figures of before and after

before dyno figures are
99hp @ 5500 and 123lbf @4600 on petrol
90hp @ 4800 and 120lbf @4500 on gas
opinions welcome on the seemingly high torque figures ?
pdf files of the printouts on here
http://www.micra.org.uk/showthread.php?t=25512
i tried the cam in btw, and it was way too peaky, so i,ve had to take a fair bit more off the flanks of the lobe

 

[CMF_frank2]

the self grind cam was,nt much of a success tbh, so i,ve had a custom inlet one done by autosprint
http://www.autosprint.co.uk/
it looks like a better profile than the pipers (and with a "true" duration), and somewhat cheaper too
he,s taken 2.5mm off the base circle, so that i can use stock shim,s above and below the bucket,s (rather than special oversize ones)
and he,s managed to get a decent profile onto a 1.0 cam too (the one on the right)

frank