[voodoogsr]

i was wondering if i set my vtec too low with my vafc, can i hurt my car, or does it make me lose horsepower, becaseu some one told me that? its set @ 4500 rpm now is that good? it seems to boost performance.

 

[toolowintegra]

you WILL lose hp with a lower vtec engagment point...... better idea would be to raise the vtec engagement by about 500 RPM....

 

[SurferX]

Stock GS-R VTEC engagement is 4400 RPM. If you set your VTEC higher without needing to you'll "feel" a stronger engagement as you begin to lose power on the low end lobes so there's a slightly higher jump in power when VTEC does engage. Of course with this you are actually going slower not faster as you spend more time losing power just to feel a stronger boost later on, another case of where the butt dyno lies to you.

This device is almost useless unless tuned on a dyno. For sure you can't go from what your ass tells you, unless you can crap out a dyno chart of course.

 

[ati2ude]

Best way to decide where your vtec engagment should be and where you get the optimal performance would be on a Dyno.

 

[ati2ude]

SurferX get out of my head! we posted that at the same exact time!!

 

[Brian_Hanspard]

For sure you can't go from what your ass tells you, unless you can crap out a dyno chart of course.

Hmmmmm, where can I get one of the dyno chart butt crappers??? Should I go see my doctor? HAHA, just messing. But yes, surfer is right, unless you go to a dyno or have some performance enhancing engine add ons, this is pretty useless.

 

[MichaelDelaney]

air flow increases as rpm increases. So air delivery increases as the rpm rise. move the VTEC earlier and the big lobe of the cam comes on earlier. A bigger lobe dumps in more fuel.

So you have more fuel at a lower rpm when the air flow is not built up enough.

What's the result? YOU RUN TOO RICH.

too rich = slow and you wash your cylinder walls with fuel...does a nice lousy number on your piston ring sealing (lose compression too).

the time you get a vafc is when you upgrade cams and need to move the VTEC UP so the huge lobe is activated when there is enough air delivery.....

AIR:FUEL RATIO....learn that concept first.

 

[voodoogsr]

i am going to get it dynoed i just havent gotten around to it yet!!!!!

 

[MichaelDelaney]

the dyno should have an exhaust wideband O2 sensor and you can get the air fuel ratios to tune the VAFC fuel settings. I tell you how to find the best VTEC point for YOUR particular engine in the dyno tuning basics article.

 

[gurasek]

question about VAFC. I'm getting told that it is for the most part useless for my car (01 gsr) cause of the OBDII ecu. i have a guy telling me that the ecu just fights with the VAFC and kind of ignores it and just changes back to normal A/F. Is this true? any thoughts would be helpful.

p.s. sorry if this is a tad off the topic.

 

[IntegraBad18c]

you WILL lose hp with a lower vtec engagment point...... better idea would be to raise the vtec engagement by about 500 RPM....

Wrong. I would engage the secondary lobes about 200 rpm before the primary lobes start losing power. You could try moving the secondary lobe engagement earlier, just to see if that medium of intake flow velocity/capacity is there. Ten bucks says it won't be though.

 

[SurferX]

It all depends on the setup really. Some setups see gains with a higher VTEC point while others like it lower.

OBD-II won't conflict with the V-AFC. It was in fact pretty much made to work with OBD-II since people couldn't reprogram their chips anymore.

 

[gurasek]

okay I figured i was getting fed a line, but just figured I'd check with you guys. this same guy said not to hook up the VTM wire from the VAFC so I figure thats false too.
anything special I should know about setting it up. seems pretty straight forward except for performing the throttle sensor type setting and voltage check. am i supposed to hold the accelerator down and then let off or something while in this mode.

sorry I'm really ignorant when it comes to technical gadgets. i usually stick to nuts and bolts.

 

[MichaelDelaney]

when you do this operation you are calibrating the throttle position from the TPS (throttle position sensor). You have to let the computer know when the throttle is closed and when it is wide open all the way. The voltage going to the ECU should be zero when the throttle is closed and the voltage recommended in the manual for when the throttle is pushed in all the way or wide open.

you don't have the engine running when you do this. just the ignition.

The computer needs to know this because it switches to open loop and runs off the ECU programs (fuel map, ignition map) instead of basing the amount of fuel to add upon the stock (low resolution or narrowband) O2 sensor at a certain partial open throttle position (that you also enter...% throttle).

throttle position calibration, open loop, closed loop...gettin kinda complicated, eh? naw..it's just like setting up the VCR before you use it....

 

[MichaelDelaney]

if you guys think this is complicated, wait until you have to work with a standalone program and enter the fuel values for each rpm/MAP combination (not just the 16 point settings like in the VAFC) and the ignition advance/retard change for each rpm/MAP combination for idle, partial throttle steady state driving, partial throttle acceleration, and full throttle acceleration for different ambient temperatures.

Thank goodness for base programs from the manufacturer out of the box or you would go bonkers starting from scratch like we used to with the old Accel DFI program or Electromotive Tec2....

 

[gurasek]

I can't imagine trying to build a standalone system and creating fuel maps from scratch, the thought alone could keep me up for nights. okay well thanks for the reassurance. as usual i'm just overthinking things again. hey i can set the clock on my VCR so with a little luck (and cursing) i'll set this thing up. lol! and thanks again for paying attention to my paranoid chatter.

 

[MichaelDelaney]

all the new standalones come with base programs now...no more starting from scratch...just tuning.

no problems...good luck with the vafc tuning....