what?! does this mean VAFCs vtec engagement control is useless caus of OB2?? read>>>
ok, i just noticed this today. i made my VAFC display the VTi and VTo during the monitor mode and this is what i noticed. i set my vtec crss over at 4700 by the way...
when i hit 4700 VTo says its on, meaning its in vtec. ok, but then the VTi doesn say its on till about 5200! and im sure alot of u notice this: when vtec is set earlier like 4700, YES u can hear it engage, but u dont really feel most of that power till 5200 rpm right? I checked back in the manual of the VAFC and according to pg 22, VTi means the "ECU VTEC solenoid output" and VTo means "V-AFC Vtec Solenoid output".
so im starting to think that even though the vtec engagement is set earlier successfully according to VTo, the "power" of the vtec doesn't fully come till 5200 according to VTi BECAUSE OF THE ECU??? is this true? does that mean we can set vtec to come earlier but the truth is the power still doenst fully come till stock rpm setting of 5200?
I think you may have a point. On the rolling road we couldn't get any torque or hp improvement by changing the actual engagement point and just left it at 5200.
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Re: what?! does this mean VAFCs vtec engagement control is useless caus of OB2?? read>>>
Quote:
Originally posted by Ng Luder when i hit 4700 VTo says its on, meaning its in vtec. ok, but then the VTi doesn say its on till about 5200! and im sure alot of u notice this: when vtec is set earlier like 4700, YES u can hear it engage, but u dont really feel most of that power till 5200 rpm right? I checked back in the manual of the VAFC and according to pg 22, VTi means the "ECU VTEC solenoid output" and VTo means "V-AFC Vtec Solenoid output".
You don't feel it because you are engaging the high cam at a lower RPM. You won't get that huge jump in power at the switch over, if you lower the switch over point. If you really want to feel it, set it at 6k RPMs or something.
The VAFC cannot alter when the ECU turns the VTEC solenoid on/off, it just modifies the signal. So, no matter where you put the VTEC crossover point, the VTi will always be when the ECU is turning the VTEC solenoid on.
You're making something simple way to complicated. OBD2 has nothing to do with it.
Yeah, if you look at a dyno sheet of one, you lower the xover before the power spike. This is what you will feel on a stock engine. If you lower the xover before the power spike, you are smoothing out the curve, taking away the sudden surge in power, and you will therefore not "feel" it as much. Its still good as if you look a a dyno, you will see that the curve has been smoothed out and you have more power and torque before the spike than before.
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If you only knew the power of the Lude...
'94 Porsche 968 - National PCA HPDE Instructor
'98 Red Base Prelude - 02 & 03 DSP Champion - Sold
"Straights are for fast cars. Turns are for fast drivers." - SCCA Solo2
If you have a street where there is a long straightaway you may want to feel the difference and set the V-AFC to a range about 6000-6500 rpms. You will feel it in the back of your seat. I did when I was in second gear playing around with it. Keep in mind you may not feel it like in a GSR because the Lude is heavier. I also suggest that you dont set it below 4000 rpms. It puts alot of stress on your engine.
Originally posted by 71dsp I meant as long as you have enough oil pressure for VTEC. Sorry!
I would agree with the "don't set it below 4k" simply b/c I wouldn't trust the AFC. It's a good product, but I would be leery about pushing that lower limit. You won't see much (if any) gain by setting it lower than 4400, anyhow. I'm not sure what the ramifications would be by trying to engage VTEC when you don't have the pressure, but if the AFC were to screw up, I wouldn't want to find out. I guess it's no more a risk than any other function of the AFC, but w/o the power gain there's no reason to even try.
What exactly do you mean? Lowering the VTEC point won't hurt the engine at all, unless you are running enough oil pressure for the VTEC solinoid.
Never mind.
Since I cannot answer you in the H/A board I thought I would answer you here.
First off I'd like to give you some props for being very knowledgable on Preludes.
But the answer to you question is (In a way you and I are right in a way.) If you set the controller below 4000 chances are you wont hurt the engine but you may put strain on the engine causing it to be sluggish at times. Plus I belive the Fuel and the Timing (depending on settings and mods) will not be there when the VTEC crossover point hits. Opinion not fact!
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Originally posted by OOHLAH
- snip -
But the answer to you question is (In a way you and I are right in a way.) If you set the controller below 4000 chances are you wont hurt the engine but you may put strain on the engine causing it to be sluggish at times.
No strain by causing it to be "sluggish." I would expect that if there isn't enough oil pressure to engage VTEC that it simply wouldn't engage; what I'd worry about is not properly or completely engaging the pins that lock the rockers and cause some sort of valvetrain damage.
Assuming the V-AFC never "fails" it should simply not work.
Quote:
Plus I belive the Fuel and the Timing (depending on settings and mods) will not be there when the VTEC crossover point hits. Opinion not fact!
There are settings on the V-AFC for all this- provided you tune it right, it won't matter where you set it.
No strain by causing it to be "sluggish." I would expect that if there isn't enough oil pressure to engage VTEC that it simply wouldn't engage; what I'd worry about is not properly or completely engaging the pins that lock the rockers and cause some sort of valvetrain damage.
Assuming the V-AFC never "fails" it should simply not work.
There are settings on the V-AFC for all this- provided you tune it right, it won't matter where you set it.
Originally posted by OOHLAH But the answer to you question is (In a way you and I are right in a way.) If you set the controller below 4000 chances are you wont hurt the engine but you may put strain on the engine causing it to be sluggish at times. Plus I belive the Fuel and the Timing (depending on settings and mods) will not be there when the VTEC crossover point hits. Opinion not fact!
Could you post my reply? I didn't save it, and I don't even remember everything that I typed!
Who really cares about below 4000? Who would really do that??? Some poor guy, lets call him rice...who doesnt know what he is doing thinking he is going to get tons of power by setting it lower... Its all good dudes, no worries. Dont beat up poor Billy over this crap...
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If you only knew the power of the Lude...
'94 Porsche 968 - National PCA HPDE Instructor
'98 Red Base Prelude - 02 & 03 DSP Champion - Sold
"Straights are for fast cars. Turns are for fast drivers." - SCCA Solo2
It's okay. A lot of them don't understand that setting the VTEC cam change over so low is actually easier on the engine because there is so much overlap on the VTEC lobes that you lose a lot of intake charge because it flows right on out the damn exhaust.
Ever wonder why hot racing cams idle so damn bad? It's the overlap (well, the lift too, but that's another story). There is so much overlap that the intake charge goes right out the exhaust, and there's hardly enough air and fuel to keep the engine running, so it lopes.
Could you post my reply? I didn't save it, and I don't even remember everything that I typed!
Thanks!
I understand what you're saying, but think of it this way; anytime you add mods to increase power, you are increasing the stress on the engine. That's a fact. The engine can handle additional stress, no problem. The main thing about running VTEC that low is oil pressure. The engine uses oil to activate VTEC. If you don't have enough pressure, there could be some issues with the pins not fully engaging, or perhaps even some oil starvation issues. This aside, when you alter the VTEC crossover points, you should also change the fuel settings as well (that's why the VTEC controllers have fuel adjustments). Spark isn't as critical, as it's set quite conservatively as is. If you plan to run the engine at nine tenths, then yes, you would need to alter spark as well.
It's really not practical to run VTEC that low. There is a tremendous amount of overlap on the high lobe cams, so you will actually lose power down in the lower RPM range.
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North Texas Prelude Owners Group www.ntpog.org
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