Omega Owners Forum
Chat Area => General Car Chat => Topic started by: ngrainqey on 16 February 2012, 12:54:56
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hello, i just thought id ask this as i dont know if its ever been asked but... How come nobody asks/says about advancing the timing slightly on the cams at such as timing belt time? Obviously i know the valves operate in interference with the piston crowns but surely setting the marks 1-2mm at a guess infront shouldn't mash valves should it? And advancing the timing would mean more power? Just thought id ask. Alex
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I dont think v6 engine will permit custom valve timings.. even if so ,you may loose high end or low end..
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Why wouldnt the correct marks give the correct timing?
If your talking about dialling in each individual cam to take out manufacturing tolerances for each individual engine and cam, then your into slotted cam wheels for adjustment and shed loads of dyno time to find the optimum. So adding performance cams makes sense and doing the whole top end.
It's not just a case of advancing both cam wheels per bank and pronouncing the car "faster" because of it. ???
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I think you must use specially designed cams having different size lobes and different uplift.. for best values , ignition timing must be arranged etc etc.. not a simple job .. you will need expensive equipment.. :-\
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i thought it was more a case of, adjust the cam timing manually which way you want to go within safe limits for the engine (without mashing valvs basically) use 97ron or above then let the car adapt and make the most of the timing advance, you'd save fuel at lighter throttle inputs then gain at higher rpm-turbo cars only start pulling timing at higher rpm because of the lack of cooling of the intake air (too small of an intercooler/too restrictive) but if the air wasnt too hot they'd maintain the timing advance which isnt an issue with an N/A car as you dont have a turbo to heat the air up
alot of turbo remapping is shit because they advance the timing at WOT but dont map for part throttle so no improvement in mpg when your not hammering it - as an example, a car has been mapped by somebody else (an 850 T5) and runs more power with less boost from the turbo by just advancing the timing to make more of the octane rating
alex
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I think - and apologies if I've misunderstood you - that you've got cam timing and ignition timing confused?
Ignition timing would be what you typically advance & retard based on the RON of the fuel or boost pressure, cam timing is more about optimising exhaust scavenging, cam overlap and so on for better cylinder fill..
AFAIK it's not possible to 'tweak' the ignition timing on the Omega as you can't 'clock' a cam or crank sensor to advance or retard it as you can with some other cars; short of remapping the ECU anyway.
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I think your best bet is a nissan skyline , so you can find adjustable cam gears.. lots of turbo choices and ecus (also custom ecu maps) and too many parts.. its a highly tuneable car.. but omega v6 has very limited tuning options..
I remember someone from asia installed either rb25 or 2jz into omega.. which would be cheaper and easier (although I'm not sure its easy :-\ )
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...i did mean cam timing lol rather than ignition timing lol
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cam timing probably won't have any beneficial effects if pulled forward with no other mods.
actually, will probably reduce power. IVC advanced will lead to less mixture captured. Ergo less power.
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how does variable cam timing work on a turbo engine then ???
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how does variable cam timing work on a turbo engine then ???
Because its variable so adjusts itself for optimum performance :y
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how does variable cam timing work on a turbo engine then ???
variable valve timing systems have a very different design
http://www.youtube.com/watch?v=ry2nP7I315M (http://www.youtube.com/watch?v=ry2nP7I315M)
http://autospeed.com.au/cms/title_Variable-Valve-Timing/A_110859/article.html (http://autospeed.com.au/cms/title_Variable-Valve-Timing/A_110859/article.html)
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with variable cam timing, you're trying to do a few things...not really to increase outright power.
firstly, maximise the overlap when cold and at low revs so you needn't have EGR ( emissions gain )
secondly, retard the inlet timing a bit when in the midrange to increase the amount of mixture trapped at IVC.
and thirdly, maximise overlap again at higher revs to regain the power you've lost from the first two.
Of course, the better systems like the Rover one and Honda's VTEC are variable duration, which you wouldn't get by moving the cams. This can and will improve power markedly.
The engine in your Omega was initially going to have variable cam timing until Opel decided it was cheaper to fit EGR. You can still see the bulges in the cam belt cover to clear the variators. I have some pre-launch info which states that the engine's got variable cams.
Actually, I can't think of a variable cam-timing turbo engine off hand - I suspect the use of the variation reduces considerably with a turbo car.
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Actually, I can't think of a variable cam-timing turbo engine off hand - I suspect the use of the variation reduces considerably with a turbo car.
Nissan VG30DETT :y N-VCT so it's a single-step intake cam advance/retard by way of a solenoid actuated oil passageway used to force a helical gear forwards & backwards in the cam sprocket to rotate it with regard to the cam itself.
Used, IIRC (having just sold mine :'( ) to reduce valve overlap once on boost - so there's more overlap for scavenge at low & mid range RPM and less overlap so you're not wasting mixture back out of the exhaust at high RPM. It's not used for EGR as the VG30DETT has a ye-olde EGR vacuum solenoid EGR valve ported into the plenum.
N-VCT was dropped in 1994 in US markets and peak power dropped ~20hp.
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Volvo 2.4 T5 and 2.5 R engines have intake and exhaust vvt ;)
all the S60's had exhaust vvt but the later 2.4 and 2.5 engines with the KKK turbo had it on both cams
thats what i had before,sold the engine from it yesterday but could easily get 350bhp with just a map.... used oil operating solenoids to control them, when logging though- stationary 3 degrees advance then 27-30 at wot then over 5500ish it'd pull it back slightly because i had a standard intercooler
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Actually, I can't think of a variable cam-timing turbo engine off hand - I suspect the use of the variation reduces considerably with a turbo car.
Nissan VG30DETT :y N-VCT so it's a single-step intake cam advance/retard by way of a solenoid actuated oil passageway used to force a helical gear forwards & backwards in the cam sprocket to rotate it with regard to the cam itself.
Used, IIRC (having just sold mine :'( ) to reduce valve overlap once on boost - so there's more overlap for scavenge at low & mid range RPM and less overlap so you're not wasting mixture back out of the exhaust at high RPM. It's not used for EGR as the VG30DETT has a ye-olde EGR vacuum solenoid EGR valve ported into the plenum.
N-VCT was dropped in 1994 in US markets and peak power dropped ~20hp.
probably used to reduce overlap at low and mid revs to avoid exhaust manifold pressure pushing exhaust back into the inlet - allowing higher boost. As a guess i'd say the boost would have been reduced on the later car ?
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Volvo 2.4 T5 and 2.5 R engines have intake and exhaust vvt ;)
all the S60's had exhaust vvt but the later 2.4 and 2.5 engines with the KKK turbo had it on both cams
thats what i had before,sold the engine from it yesterday but could easily get 350bhp with just a map.... used oil operating solenoids to control them, when logging though- stationary 3 degrees advance then 27-30 at wot then over 5500ish it'd pull it back slightly because i had a standard intercooler
that's a shame - i've got two T5's and neither have got variable cams.
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probably used to reduce overlap at low and mid revs to avoid exhaust manifold pressure pushing exhaust back into the inlet - allowing higher boost. As a guess i'd say the boost would have been reduced on the later car ?
Boost pressure (at least on paper ;)) is the same on all years at 8psi (6psi until warm and/or if the knock threshold is reached), and from memory the part number for the cams themselves is the same - sprockets are different on the intake, of course. I've never put a set of cams side by side to check, though .. having one VG30DETT in bits was quite enough ;D
(This is not helping me get over the loss of having sold it last week, at all :( )
Whether it sheds any light on things, but the official reason for dropping the N-VCT was US (Cali) emissions regulations - so the 20hp drop could easily be down to a difference in the tune rather than the engine, I suppose :)
Great powerplant, just a shame mine urinated oil at a fairly constant rate.
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I promise not to mention the car again :(
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I promise not to mention the car again :(
:y :)
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Volvo 2.4 T5 and 2.5 R engines have intake and exhaust vvt ;)
all the S60's had exhaust vvt but the later 2.4 and 2.5 engines with the KKK turbo had it on both cams
thats what i had before,sold the engine from it yesterday but could easily get 350bhp with just a map.... used oil operating solenoids to control them, when logging though- stationary 3 degrees advance then 27-30 at wot then over 5500ish it'd pull it back slightly because i had a standard intercooler
that's a shame - i've got two T5's and neither have got variable cams.
what are they? v70's? 850's? the me7's all have atleast exhaust vvt so 2000ish onwards
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found some stuff which i might be trying:
Tighter lobe centers:
more peak power,
higher fuel consumption
rougher idle
more torque at low RPMS,
peak power occurs at LOWER RPM,
higher emissions,
power RPM band gets narrower and moves DOWN
Wider lobe centers opposite of above
and
Advancing the cam
slightly improved low rpm torque,
slightly reduced peak power
imperceptible change in emissions, idle & fuel consumption
Retarding the cam
opposite of the above
so im fancying less overlap and retard the timing or more overlap and advance the timing :P
im not sure which way round yet as i like the rougher idle sound lol but dont want to mash the valves lol
will keep people updated anyway, might dyno it after and compare it to standard timing at a later date when i can be arsed to alter it bak basically lol
alex
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I dont think v6 engine will permit custom valve timings.. even if so ,you may loose high end or low end..
::)