Which is best vtec controller
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Originally posted by Epoch
Though... this raises a question that I wondered about... does the VTEC system _only_ allow an increase in the cam lift and duration, or can it offer a decrease? Kinda curious if you can set up the VTEC cams in a turbo'd system to reduce the overlap when in the upper RPMs, allowing the turbo system to effectively pressurize the cylinders better with less blowby? Yet, in the lower RPMs, allow the right amount of overlap to purge the exhaust gas and (maybe?) speed up the spooling or the turbo? *fantasy*
Though... this raises a question that I wondered about... does the VTEC system _only_ allow an increase in the cam lift and duration, or can it offer a decrease? Kinda curious if you can set up the VTEC cams in a turbo'd system to reduce the overlap when in the upper RPMs, allowing the turbo system to effectively pressurize the cylinders better with less blowby? Yet, in the lower RPMs, allow the right amount of overlap to purge the exhaust gas and (maybe?) speed up the spooling or the turbo? *fantasy*
Originally posted by 99DCtwo
there will balways be a power drop when you engage vtec, take a look at your dynos always see a slight power drop and then it raises no matter when you turn on the pay check, your car doesn't say right at 4000 rpms exactly like the the very microsecond that the 1st cyl. hits v tec starts its lags the entire drive train down a bit to start moving the secondaries!!!!!!!!!
there will balways be a power drop when you engage vtec, take a look at your dynos always see a slight power drop and then it raises no matter when you turn on the pay check, your car doesn't say right at 4000 rpms exactly like the the very microsecond that the 1st cyl. hits v tec starts its lags the entire drive train down a bit to start moving the secondaries!!!!!!!!!
I see no drop in power....
That dip is due to poor timing of VTEC engagement combined with cams that are too aggressive for the RPM range they are being used in. Proper tuning will eliminate it.
CHRISTMASTIME IN IRAQ
Joined: Apr 2003
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From: Bay Area
Originally posted by qtiger
You can have it do anything you want. It's a whole new cam lobe.
You can have it do anything you want. It's a whole new cam lobe.
And that's one strong running and well kept B16b!
Wannabe yuppie
Joined: Dec 2000
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From: Madison, WI
VTEC is actually very simple in its concept. Instead of one cam profile you have two, and you can switch between them. Any cam profile has a range of rpms where it is at peak efficiency. The ideal point for the VTEC switch is determined by the point at which the primary cam profile will make the same amount of power as the secondary cam profile. At this point, you engage the secondary cam profile and it picks up where the primary profile left off with no dip in power. The way you determine where your primary cam profile falls off and your secondary picks up is to do a dyno run with the VTEC point set very high so as to get enough data for the primary profile, then with the VTEC point set very low to get enough data for the secondary profile. Compare the charts, see where the lines meet, and there's your VTEC point. Deciding to arbitrarily lower the VTEC point by 1000 rpm or so will not really do anything for you. You do not need to change your VTEC point nor will you gain much power from doing so unless you have changed your cams and they need to be tuned.
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Originally posted by Epoch
Ah... so the secondary lobe can be an entirely different profile from the primary one? eeenteresting...
Ah... so the secondary lobe can be an entirely different profile from the primary one? eeenteresting...
Originally posted by 99DCtwo
All good stuff, Hey can you let me know where the vtec engagement point is exactly on those dyno runs????
All good stuff, Hey can you let me know where the vtec engagement point is exactly on those dyno runs????
Originally posted by kfar09
im looking at my dyno plot right now and my hp and torque drop right at 4000 rpm. and then they start to go back up a little at 4300. so wouldn't i want to change my vtec engagement to 4000 rpm so my powerband doesn't drop
im looking at my dyno plot right now and my hp and torque drop right at 4000 rpm. and then they start to go back up a little at 4300. so wouldn't i want to change my vtec engagement to 4000 rpm so my powerband doesn't drop
You could fiddle with it a bit on the dyno, but what you're seeing could be a hole in your tune as well. Are you using the nitrous maps for your VTEC fuel and ignition or is it all on the main map?
un-Touch'd krew
Joined: May 2001
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From: My own level of hell
Even with massive upgrades a VAFC is pretty much useless.
On the setup you describe I would waste my money on some real engine upgrades instead of this bolt on performance crap.
On the setup you describe I would waste my money on some real engine upgrades instead of this bolt on performance crap.
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"I'll keep my money, guns and freedom. You can keep the "Change."
"I'll keep my money, guns and freedom. You can keep the "Change."
CHRISTMASTIME IN IRAQ
Joined: Apr 2003
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From: Bay Area
Originally posted by qtiger
I think the only limitation would be that you couldn't have the VTEC lobe be a lower lift than the primaries, because the rocker arms would still be riding on the primaries instead of the VTEC lobe.
I think the only limitation would be that you couldn't have the VTEC lobe be a lower lift than the primaries, because the rocker arms would still be riding on the primaries instead of the VTEC lobe.
It would be crazy if the VTEC could shorten as well as increase, but that would take some weird-ass servo-articulated system or such... or something like the BMW Double Vanos system...