mcerd1
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| posted on 2/10/08 at 03:43 PM |
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my crazy though for the day.....
I'm I right in thinking that the variable valve timing on the ST170 zetec and alike just switch in at a given engine speed ?
if so then I assume you could run this from one of the programmable outputs on a megajolt with a set of carbs
has anyone actually tried this?
would it work?
would you actually gain anything by doing it ?
[Edited on 2/10/08 by mcerd1]
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whitestu
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| posted on 2/10/08 at 03:45 PM |
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I think you could. AFAIK you could run it from a switch on the dash.
Stu
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coozer
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| posted on 2/10/08 at 04:33 PM |
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I have the same thoughts and I'm going to use one of the change lights on the jolt to switch it.
Advantage is increased valve overlap, aka hairy cams but only at peak revs making the idle and lower revs granny friendly.
Thats my take on the VVT anyway.
Steve
1972 V8 Jago
1980 Z750
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matt_claydon
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| posted on 2/10/08 at 05:06 PM |
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Just wire it to be on permanently, then you'll get a nice lumpy idle too 
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novacaine
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| posted on 2/10/08 at 05:49 PM |
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nowt wrong with a lumpy idle,
sod the VVT and just get a good hot cam and get that lovely vrum vrum vrum noise on tick over
And you run and you run to catch up with the sun but its sinking, Racing around to come up behind you again, the sun is the same in a relative way but
your older, shorter of breath and one day closer to death
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Mark G
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| posted on 2/10/08 at 06:50 PM |
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Most VVT systems use a magnet on the front of the head to advance / retard one of or both of the cams. I'm sure you'd be able to sort
something out with it as I can only recall ever seeing 2 wires going into them.
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MikeRJ
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| posted on 2/10/08 at 07:13 PM |
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The problem with VVT and carbs is there is no easy way of optimising the fueling for both cam positions.
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hillbillyracer
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| posted on 2/10/08 at 07:55 PM |
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I have a recolection of Dave Walker in CCC finding that if a Honda Vtec he had in was locked in the "high rev" mode it made more power
pretty much everywhere that mattered but was too lumpy at idle. But that was only due to it having a plenum chamber & single throttle body &
if it was put on single throttle bodies (individual carbs like you have would do the same but the carbs would still be lumpier than EFI) the lumpy
idle was cured.
There are loads of different Honda Vtec specs & not all are aimed at performance, but the Ford ST170 definately is.
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prawnabie
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| posted on 2/10/08 at 08:48 PM |
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Be careful as some VVT dephaser pulleys run on oil pressure to phase the cam. I know renaults F4R engine does and so does peugeots 1.4 16v VVT
Shaun
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Mark G
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| posted on 2/10/08 at 09:14 PM |
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Vtec also runs on oil pressure but is totally different to VVT.
VVT advances and retards the cam/s accordingly to vary open and close angles. This is a progressive change and is variable hence the name.
Vtec effectively uses a second more aggressive set of lobes on the cam. This is an on cam / off cam change hence the sudden kick when the vtec comes
on.
[Edited on 2/10/08 by Mark G]
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mad4x4
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| posted on 3/10/08 at 06:03 AM |
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quote:
Originally posted by MikeRJ
The problem with VVT and carbs is there is no easy way of optimising the fueling for both cam positions.
IIR I THink Megajolt can swap between two maps in the latest software
Scot's do it better in Kilts.
MK INDY's Don't Self Centre Regardless of MK Setting !
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MikeRJ
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| posted on 3/10/08 at 08:20 AM |
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quote:
Originally posted by mad4x4
quote:
Originally posted by MikeRJ
The problem with VVT and carbs is there is no easy way of optimising the fueling for both cam positions.
IIR I THink Megajolt can swap between two maps in the latest software
That's ok for the ignition, but it doesn't fix the fueling.
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