VTCS manifold unpleasantness
#102
He stated no change. A dyno of his setup would be irrelevant to whatever dyo plot of manifold/dyno/car/weather you might have access to.
Just wait for A/B. Same car/dyno/day.
The interesting point is no gains by removing the butterflies. That surprise means the endemic suckiness is strong with the VTCS runner/plenum configuration. POS long before it reaches the butterflies it seems.
Just wait for A/B. Same car/dyno/day.
The interesting point is no gains by removing the butterflies. That surprise means the endemic suckiness is strong with the VTCS runner/plenum configuration. POS long before it reaches the butterflies it seems.
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#103
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<p>
The car and the dyno are both extremely repeatable. I've taken tons of pulls on this one. If a new feature needs to be tested or the dyno needs to be tested, this is the car I use. It makes 114 whp every time, hot, cold, humid, dry, whatever. 01 with standard bolt ons and a MS3. For reference, the car made about 100 stock and a bone stock 1.6 made 78 whp on our dyno.
Indeed. I was expecting to pick up a couple, and was surprised to see my current plots line up exactly on my comparison plots. At least I took a pound or two off the car.</p>
The interesting point is no gains by removing the butterflies.
#105
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Originally Posted by Ben
No change
#106
Yah that points to (maybe) the plenum volume resonance tuning being more important than we thought. I still can't figure out what the inner, short vestigal runners that terminate in the resonance chamber are doing. I can only guess that they are sending the return wave back down the intake tract as if it were a shorter runner manifold. Opening and closing the VICS butterflies changes the pressure differential between that chamber and the pulse coming back through the runners. Dunno, just spit balling but clearly there is some dynamic there that we're all successfully tuning with but don't fully understand. Gah.
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#107
Yah that points to (maybe) the plenum volume resonance tuning being more important than we thought. I still can't figure out what the inner, short vestigal runners that terminate in the resonance chamber are doing. I can only guess that they are sending the return wave back down the intake tract as if it were a shorter runner manifold. Opening and closing the VICS butterflies changes the pressure differential between that chamber and the pulse coming back through the runners. Dunno, just spit balling but clearly there is some dynamic there that we're all successfully tuning with but don't fully understand. Gah.
#109
The dyno results we have all gotten bear that out. VICS without butterflies make a wee bit more above 8000 but die in the midrange on EP engines. VICS with butterflies opening early make the best overall area under the curve on engines with rev limits below about 7800. VTCS die on top no matter what you do.
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#111
It seems you lose just a few hp below torque peak (circa 4800) and gain some above. From what I have seen on our cars, it appears the gains above torque peak are greater than the losses below it.
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#113
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By sound I assume you mean intake resonance tuning, yes of course they are. It occurred to me that the little shorty runners in the VICS (not having measured them), might be generating a 2nd order harmonic. That would just be coming in above 7000 and might explain why the VTCS falls on its face past 6400. Most OEM manifolds, including the B6/BP, use 3rd order harmonics due to space constraints. Opening and closing the butterflies might change the pressure differential in the VICS chamber just enough to neutralize it's effect as a barrier to that pulse. IOW, if that pressure wave rolling up the runner hits a a sharp pressure delta, either positive or negative, it's speed will change and that bounces all or most of that pulse back down towards the valve where it can chirp your tires in 2nd. Perhaps Mazda was able to time things so that when the butterflies open or close they can successfully negate the effect of that chamber on the pulses.
The dyno results we have all gotten bear that out. VICS without butterflies make a wee bit more above 8000 but die in the midrange on EP engines. VICS with butterflies opening early make the best overall area under the curve on engines with rev limits below about 7800. VTCS die on top no matter what you do.
The dyno results we have all gotten bear that out. VICS without butterflies make a wee bit more above 8000 but die in the midrange on EP engines. VICS with butterflies opening early make the best overall area under the curve on engines with rev limits below about 7800. VTCS die on top no matter what you do.
Fun fact: the obnoxious noise you get with the windows down on the freeway is the same effect. The resonance chamber is very large so the resonance frequency is low. WUB WUB WUB.
#115
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I was third owner of my car; I believe it was an Oregon car initially (ie, non-CA) but I am not positive. Don't know if there was any difference in CA vs non-CA cars.
#116
I'm going to be doing the VCTS to VICS swap soon, and wanted to see which fuel rail people were using with their VVT motors. I've read that there could be clearance issues with the stock NB2 fuel rail and VICS manifold that require the NB1 fuel rail to be used, but nothing 100% confirming this. Is this the case with everyone else that has done this swap - is an NB1 fuel rail required to clear the VICS manifold?
I'm hoping to get some dyno pulls in before and after the swap (gotta get my MS3 installed and tuned, first). If nothing else I'll see if I can get some good A/B comparison data from VirtualDyno.
I'm hoping to get some dyno pulls in before and after the swap (gotta get my MS3 installed and tuned, first). If nothing else I'll see if I can get some good A/B comparison data from VirtualDyno.
#117
I'm going to be doing the VCTS to VICS swap soon, and wanted to see which fuel rail people were using with their VVT motors. I've read that there could be clearance issues with the stock NB2 fuel rail and VICS manifold that require the NB1 fuel rail to be used, but nothing 100% confirming this. Is this the case with everyone else that has done this swap - is an NB1 fuel rail required to clear the VICS manifold?
--Ian