MkIndy7
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| posted on 8/7/06 at 02:18 PM |
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Vernier Cam Timeing with standard cams
Not sure if anyone with some cam Timeing info can help on this one.
I've got a Vauxhall XE engine and its previous owner put Vernier Pullies on the standard cam just to make it look prettier.
Somebody tried knicking these so 1 had been loose, being the standard cam we re-set it on 0 advance, 0 retard.
Any idea if this would be right?
I can't find no info for the pullys and the Heynes says to set the timeing using the marks which of cause are on the original pullys 
The car runs fine but seems to be revving a bit high, say 3K rpm + at 70mph and 4K rpm+ at 80 just wondering if that could be why.
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MikeR
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| posted on 8/7/06 at 02:29 PM |
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revs are fixed by the rear wheels / gearbox combination. 1 turn of the rear wheel in a certain gear will always equate to x turns of the engine
irrespective of what nice trick bits you've got on it.
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andyharding
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| posted on 8/7/06 at 02:33 PM |
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Only reason to fit verniers with standard cams is if the head / block has been skimmed. Even then you need the cam timing figures to set it up
properly.
I would get some standard pulleys from the scrap yard and sell the verniers on ebay unless you plan to change the cams.
Are you a Mac user or a retard?
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MkIndy7
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| posted on 8/7/06 at 02:33 PM |
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Surely if the timeings out then you will have to rev it higher to get the same power and thus speed?
The exhaust cam also drives the Dizzy so it could (although shouldn't as it adjusts itself with the knock sencor) cause the wrong ignition
timeing as well.
(The engine is completely standard cams, block, head etc never been apart since new) Just seems a shame to do away wiv em as they do look better.
[Edited on 8/7/06 by MkIndy7]
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DIY Si
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| posted on 8/7/06 at 02:48 PM |
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Keep them and just save up for some nicer cams. A ahynes manual should be able to tell you about the cam timing.
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MikeR
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| posted on 8/7/06 at 08:45 PM |
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crank is solid and connected to flywheel, fly is connected to gearbox (via clutch, lets just assume its not slipping), gearbox is in a gear and thus
connected to prop, prop is connected to diff, diff to drive shaft, drive shaft to wheel.
if 70mph is 4000rpm irrespective of the engine condition / tuning it will always be 4000 rpm as there is a direct connection between the wheels and
the engine.
How quickly it gets to 4000rpm, how economical, how smooth - they are all dependent on things like the cam's etc, but the number of revs at a
speed is fixed by the combination of wheel size, diff ratio, gear and thats it.
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MkIndy7
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| posted on 9/7/06 at 12:15 AM |
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Good explanation thanks, the engine must rev very high then and pull throught 5th gear as there alleged to do 140mph! 
We set up the timeing with the Verniers as best we could to the Heynes and some info from SBD and it seems to have alot more Torque and accelerate
faster and seem 250 rpm lower at 80mph although that might be due to the digi dash's resoloution and the fact that the exhaust cam also drives
the Dizzy.
Although any more info anyone can give would be appreciated further
Cheers, Ian
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SteveH
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| posted on 9/7/06 at 11:29 AM |
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quote:
Originally posted by MikeR
crank is solid and connected to flywheel, fly is connected to gearbox (via clutch, lets just assume its not slipping), gearbox is in a gear and thus
connected to prop, prop is connected to diff, diff to drive shaft, drive shaft to wheel.
if 70mph is 4000rpm irrespective of the engine condition / tuning it will always be 4000 rpm as there is a direct connection between the wheels and
the engine.
The only non fixed point is the clutch & this can slip for a few reasons... Clutch slip effects the higher gears more....
Is your clutch slipping?
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MikeR
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| posted on 9/7/06 at 11:34 AM |
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yeah but 3k revs at 70mph isn't high
lets get the wheel size, diff ratio, gearbox ratio and work out what it should be. then we'll know if the clutch is giving us grief.
mkindy7 - over to you.
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MkIndy7
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| posted on 9/7/06 at 02:53 PM |
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Naah suppose it isin't that high, if 70mph is 3K revs then in theory 140mph would be 6k (or the 6.5k they rev to) so it is theoretically
possible. Just thought being such a big powerful engine it'd only be ideling away at 70.
The car does drive alot better now we've changed the timeing to the best we can guess at much torqueier and better power delivery.
Itshad the Flywheel lightned, the pressure plate skimmed a new clutch plate and release bearing etc so I don't beleive its slipping.
But if somebody knows how to work it hout here's the info:
Tyres are 195 45 R16
5th Gear Ratio = 0.89
Final Drive Ratio = 3.42
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MikeR
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| posted on 9/7/06 at 03:09 PM |
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3.42 final drive, are you sure?
What is fitted?
escort rear axle could be 3.54, sierra 3.62 or 3.92.
(could be 3.14 or 3.3(2?) if its a rare sierra axle)
capri had 3.75 or a 3.02, errrm, i really should check these instead of trying to remember, bound to have got them all wrong now!!!!!! 
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MkIndy7
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| posted on 9/7/06 at 03:33 PM |
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Ah, forgot to explain that one, its in a FWD Opel Corsa
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MikeR
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| posted on 9/7/06 at 03:40 PM |
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i'll just go and hide under a rock!
download gearcalc.zip if you want to play around with different ratio's etc but .....
i calculate that ........
3000rpm = 67mph
4000rpm = 90mph
(don't forget you'll get some speedo inaccuracy)
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MkIndy7
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| posted on 9/7/06 at 03:50 PM |
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Thats the puzzeling bit,
For the extra 1,000 revs it makes about 10mph and i've checked the Speedo with the GPS and its only reads about 2mph over betweeen 70mph upto
about 90mph
Its an Astra Digi dash and the rev-counter is like a bar graph so maybe its rounding up the revs to 3k when i'm doing 70mph and rounding down
when doing 80mph
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MikeR
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| posted on 9/7/06 at 03:56 PM |
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what sender are you using? is it possible that the sending is sending too many signals for teh digidash to read them all or that the signals are
occuring so quickly that they are blending together.
at that speed does it really matter, you're way over the speed limit and therefore would never do them 
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MkIndy7
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| posted on 9/7/06 at 04:07 PM |
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The RPM and the Speedo are both electronic senders although the speedo transducer and the digi dash are not an original pair but should be of the same
type.
The main reason I questioned it all was that it was a bit thirsty and I presumed it was because it was reving high.
After playing with the verniers and setting it the best we can it now drives alot better, before if you floored it at say 40mph in 5th it just coughed
and really hesitated yet was ok if booting and keeping high up in the revs.
Now it drives like i'd have expected, and a Scooby didn't 
Just don't like guessing at things like that and posted hopeing somebody might have some figures to work to in relation to veriners with
standard cams on that engine or any in general.
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