JimM
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| posted on 19/11/08 at 12:47 PM |
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ST170
Can someone provide details on the difference between a Zetect 2.0 and the ST170 engine. What is the benefit of variable valves and how do you control
them. Could an ST170 be run with R1 Bike carbs and Megajolt system as used on a standard Zetec engine.
Just pondering possible future upgrade paths .... other suggestions welcome and if possible estimated costs.
ta
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UncleFista
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| posted on 19/11/08 at 01:05 PM |
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I'm pretty sure the cam profile shifts using an electrical signal, someone was talking about connecting it to an output on a megajolt, sounds
like it could work ?
I know that Dave Walker was working on a Honda Vtec engine and he said the "more power" profile could've been used exclusively,
apart from low revs uneveness/stalling. Even that could be sorted (according to Dave Walker) using ITB's...
All this is what my fevered brain remembers, so could be true, or could be bollox 
Tony Bond / UncleFista
Love is like a snowmobile, speeding across the frozen tundra.
Which suddenly flips, pinning you underneath.
At night the ice-weasels come...
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dinosaurjuice
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| posted on 19/11/08 at 01:19 PM |
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i think the shift-light function on the megajolt ecu's can be used to activate the 'more power' cam timing.
Not a good idea to have it on all the time, poor fuel economy and rough idling.
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mcerd1
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| posted on 19/11/08 at 02:01 PM |
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I sort of asked before just to get some thoughts about running variable cams with carbs
the big question was how would you tune the carbs to cope with the change ?
obviously if you had bike TB's you'd program the ECU to sort out the fuel
but asside from that I thought the ST head / block have a few other changes like better port shapes etc ??
(please correct me if I'm wrong)
[Edited on 19/11/08 by mcerd1]
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coozer
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| posted on 19/11/08 at 02:11 PM |
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Right up my street here, I have an ST170 currently prepped to go in my car in place of the 1.8 zetec. Check my blog below.
ST170 has bigger ports, sodium filled waisted stem valves and higher comp ratio. Higher lift cams with VVT. Forged pistons and generally stronger
bottom end. Rev limit is raised to 7500rpm or there abouts.
My plan is to use the ZX9R carbs I have on the 1.8 along with the Megajolt I'm using. May go back to Bogg Brothers for another set up and RR
session.
VVT is activated by a solenoid valve on top of the cam cover that allows oil pressure into the inlet cam. The VVT is controlled by the oil pressure
that constantly changes depending on throttle position, load etc which continually varies the cam overlap. Full power runs with high oil pressure give
the maximum power.
I intend to use the shift light function on the Megajolt to open the vavle at about 4K.
I have some Honda CBR1000's TB's in the wings for future development but my immediate concern is the ignition timing needing to change to
adapt to the cam timing. I'm not sure if a static table is OK. Still working on it.
A bigger diameter exhaust may be in order too, the standard ST downpipe is fatter than mine.
Anyway, its going in as is, the only other mod I intend is a JAW or similar to monitor the mixture during VVT activation.
Keep an eye on my blog as I intend to have it in and running this weekend
Steve
1972 V8 Jago
1980 Z750
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MikeRJ
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| posted on 19/11/08 at 04:02 PM |
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quote:
Originally posted by coozer
The VVT is controlled by the oil pressure that constantly changes depending on throttle position, load etc which continually varies the cam overlap.
Full power runs with high oil pressure give the maximum power.
I don't think this is the case for the ST170, like the Fiat and Alfa system it simply advances or retards the cam to a fixed position (using oil
pressure to do so). It would be completely unpredictable if the timing changed according to oil pressure as this changes not only as the oil warms
up, but also as the oil and the engine ages.
[Edited on 19/11/08 by MikeRJ]
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Dave Bailey
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| posted on 26/11/08 at 07:21 PM |
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Steve,
I will be interested in how this goes because I am doing a similar install however I have dry sumped the motor and plan to fit throttle
bodies from a 2.0 litre Micra rally car. I plan to fit a 2.5" exhaust and sports CAT. I will run the VVC using an S60 pro DTA ecu.
Dave B
[Edited on 26/11/08 by Dave Bailey]
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