That's precisely what I intend to do.
All I've done before is unplug the wires to the VCT solenoid on an S14 once to "see if it really makes any difference" on the dyno. It sure does! It pains me to remove the VCT when bigger cams are fitted cos I know that I'm missing out on low/midrange torque.
From what I've heard these VCT mechanisms are decidedly unreliable once they have a few k's under their belt too...
PL
VCT Control points for S14/S15 found
Moderator: Matt
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chris2712au
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common that the oil is not changed on a regular basis.... this blocks the galleries to the VCT control valve... only makes noise on startup but this wears the springs out and the gears inside... the units can deteriorate quickly if this happens... but should last if the oils is always changed regularly with good oil not the cheap crap... I know mine is stuffed but frequent flushes to the oil has brought it back to life a little.. s15 ones are not serviceable either... and its just not a matter of springs as far as I am aware..PL wrote:That's precisely what I intend to do.
All I've done before is unplug the wires to the VCT solenoid on an S14 once to "see if it really makes any difference" on the dyno. It sure does! It pains me to remove the VCT when bigger cams are fitted cos I know that I'm missing out on low/midrange torque.
From what I've heard these VCT mechanisms are decidedly unreliable once they have a few k's under their belt too...
PL
with the noticeable kick in of the VCT on the Dyno graph you showed you can level it out by vct on 5K... I have been told but would like to see it on the dyno... maybe we can do it on my car..
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Legionnaire
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Well, the torque curve overlay approach might be not too good because you have to optimise your fuel and ignition mapping for each cam position (which is not a simple job itself) and after finding the "crossover" rpm point on torque curves you have to work out acceptable hybrid of two mappings.
On s14a's/15's and r34's you have to play with two switch points, dont know if z32's switches its intake cams once or twice per rpm band.
By the way, do you guys know by how much degrees VTC moves intake cam? AFAIK, on Z32's it advances intake by 20 degrees when activated, does this hold true on SR20's and RB25's, TB48's, VH45's, etc?
Cheers, Petros
PS. I wonder if it will be good to have VTC active zone highlighting by a setting in checkbox on ignition map. Like this (I used knock feedback highlighting just for example, but you've got the idea):
On s14a's/15's and r34's you have to play with two switch points, dont know if z32's switches its intake cams once or twice per rpm band.
By the way, do you guys know by how much degrees VTC moves intake cam? AFAIK, on Z32's it advances intake by 20 degrees when activated, does this hold true on SR20's and RB25's, TB48's, VH45's, etc?
Cheers, Petros
PS. I wonder if it will be good to have VTC active zone highlighting by a setting in checkbox on ignition map. Like this (I used knock feedback highlighting just for example, but you've got the idea):
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Cheers,
Petros Katunian
Petros Katunian
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J30_VG33ET
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Tuning RPM based features
This might be interesting to you guys:
viewtopic.php?p=4719#4719
viewtopic.php?p=4719#4719
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JasonKemmerer
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skylinegtrhr
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Re:
(waking up a dead thread here)
What strikes me as a bit odd, is that VTC is basically on 90% of the usable rpm range.
Why would you (as a manufacturer) employ VTC then?
On the RB25 VTC is engaged till 4600rpm or so.
All in all I still think the whole concept of opening the intake valves earlier at low RPM is kinda bullocks.
Have a read here:
http://en.wikipedia.org/wiki/VANOS
BMW did it as well, but the right way round
Read for yourself:
VANOS operates on the intake camshaft in accordance with engine speed and accelerator pedal position. At the lower end of the engine-speed scale, the intake valves are opened later, which improves idling quality and smoothness. At moderate engine speeds, the intake valves open much earlier, which boosts torque and permits exhaust gas re-circulation inside the combustion chambers, reducing fuel consumption and exhaust emissions. Finally, at high engine speeds, intake valve opening is once again delayed, so that full power can be developed. VANOS significantly enhances emission management, increases output and torque, and offers better idling quality and fuel economy.
What strikes me as a bit odd, is that VTC is basically on 90% of the usable rpm range.
Why would you (as a manufacturer) employ VTC then?
On the RB25 VTC is engaged till 4600rpm or so.
All in all I still think the whole concept of opening the intake valves earlier at low RPM is kinda bullocks.
Have a read here:
http://en.wikipedia.org/wiki/VANOS
BMW did it as well, but the right way round
Read for yourself:
VANOS operates on the intake camshaft in accordance with engine speed and accelerator pedal position. At the lower end of the engine-speed scale, the intake valves are opened later, which improves idling quality and smoothness. At moderate engine speeds, the intake valves open much earlier, which boosts torque and permits exhaust gas re-circulation inside the combustion chambers, reducing fuel consumption and exhaust emissions. Finally, at high engine speeds, intake valve opening is once again delayed, so that full power can be developed. VANOS significantly enhances emission management, increases output and torque, and offers better idling quality and fuel economy.
PL wrote:Sweet!
So looking at S15 the temperature range is -50 to 120, so effectively active all the time. And Max speed cut is at 0, so I assume that means it's also active at any speed.
RPM window is 1050 - 5700 so it looks like inlet cam is advanced once you're above idle and it stays that way until 5700. I just went through the manual and it mentions those figures.
Looking at the power curves we recently got for std S15 you can clearly see the switchover point:
http://www.plmsdevelopments.com/custome ... i_edit.jpg
Good stuff. I love it when things add up!
PL
Re: VCT Control points for S14/S15 found
Not bollocks at all. Works brilliantly. I've tried disabling it on the dyno numerous times and the difference is amazing. S13 SR20's really miss out by not having VCT. S14/15 come on boost about 500rpm earlier and maintain power 500rpm longer up top.
I did some playing with adjustable cam gears on my S13 DE years ago and after much experimentation I finished up with the inlet cam advanced 1 tooth. This gave a measurable mid range increase and just happens to e the same amount that the inlet cam is advanced on the S14/15!
Note that the info from BMW was saying that they don't advance it down low (idle) - it's in the midrange.
The main downside to VCT seems to be that the mechanism itself is a bit weak and cannot handle bigger cams/harder springs.
PL
I did some playing with adjustable cam gears on my S13 DE years ago and after much experimentation I finished up with the inlet cam advanced 1 tooth. This gave a measurable mid range increase and just happens to e the same amount that the inlet cam is advanced on the S14/15!
Note that the info from BMW was saying that they don't advance it down low (idle) - it's in the midrange.
The main downside to VCT seems to be that the mechanism itself is a bit weak and cannot handle bigger cams/harder springs.
PL
Re: VCT Control points for S14/S15 found
Hi Pete,
BMW turned VANOS on at about 3500 and off at around 5000.
Of course I believe you, but till today nobody could deliver an explanation why more overlap at low
rpm yields more torque.
I will run a test on the dyno ...
VTC on, and VTC off.
BMW turned VANOS on at about 3500 and off at around 5000.
Of course I believe you, but till today nobody could deliver an explanation why more overlap at low
rpm yields more torque.
I will run a test on the dyno ...
VTC on, and VTC off.
Re: VCT Control points for S14/S15 found
I think you need to make the distinction between low RPM and midrange torque. Low rpm they tend to leave the cams alone, midrange they advance them and then up top they're retarded again.
Cam timing is an extremely complex subject and I only have a very basic knowledge. That's why I tend to rely on actual results to draw a conclusion.
I'm currently driving a friend's N14 Pulsar with SR20DE. This thing has the poorest midrange I've ever experienced from an SR. Then it wakes up about 5500 and screams away to 7000+. It's been messed with by previous owners and I'm guessing they've installed the inlet cam retarded by a tooth. Time will tell!
PL
Cam timing is an extremely complex subject and I only have a very basic knowledge. That's why I tend to rely on actual results to draw a conclusion.
I'm currently driving a friend's N14 Pulsar with SR20DE. This thing has the poorest midrange I've ever experienced from an SR. Then it wakes up about 5500 and screams away to 7000+. It's been messed with by previous owners and I'm guessing they've installed the inlet cam retarded by a tooth. Time will tell!
PL