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Old April 19th, 2011, 08:04 PM   #1
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VTEC @ 4000rpms possible on stock ECU?

Hey guys i was just browsing through the factory service manual and came across an interesting tid bit of info. i was reading the ECU pinouts and something jumped out at me. to make a long story short I read and remembered that the variable intake manifold actuator valve for the 7th gen 6 speed accord i believe gets activated @4000rpms so in theory could one jump a wire or two to the VTEC solenoid to activate it at 4000RPMs?....I have no idea what the benefits would be as of yet however given the flat powerband our engines have and no sort of dips before or after VTEC engages it seems moving VTEC to a lower RPM could be beneficial with no ill effects??? i can say right now that when i am on the course it would help me becuz i am caught in between gears.. and this may give a slight edge in a straight line race so u reach your powerband quicker. this is a prequel to another thread i will create soon lol

Please discuss any input is appreciated.

Thanks!
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Old April 20th, 2011, 07:42 AM   #2
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Subscribed. This is VERY interesting. I think I read of a J32 swap lowering VTEC and having very good results. Every other Honda that has a lower VTEC has had a much fatter powerband. If this is possible, I'm all over it.

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Old April 20th, 2011, 08:17 AM   #3
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If you use an apxei vafc you can adjust vtec. I think a few ppl on here have done it although the stock ecu resets it often.
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Old April 20th, 2011, 08:30 AM   #4
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yo...

Quote:
Originally Posted by inspire1318 View Post
If you use an apxei vafc you can adjust vtec. I think a few ppl on here have done it although the stock ecu resets it often.
I will try it today on my fic....

I am pretty sure I have mine set at 4500 or 4300 right now....

will post back tonight the results....
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Old April 20th, 2011, 09:36 AM   #5
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i run a vafc2 setup and run vtec at 4300.no issues at all.oil presure is good also.
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Old April 20th, 2011, 10:26 AM   #6
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^Does it yeild the desired results talked about above. If indeed, you can lower it to 4,000rpm and it kicks with no side effect, then why did honda not put it there in the first place? I'm wondering what the cons would be for lowering it.
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Old April 20th, 2011, 11:10 AM   #7
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Well, we know the VTEC point can be changed with VAFC2/FIC, etc. What Paul is trying to figure out is if we can do it on the STOCK ecu. If so, that would be something to try out. It would probably need to be tuned, but you never know. Honda didn't suit up the J series for performance, so maybe this could prove to be worthwhile.

Bdb: Let us know what you find. If you can change it to 4000 (where the butterflies open up), maybe your car would even be quicker ha. Let us know what you find!
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Old April 20th, 2011, 03:50 PM   #8
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sounds interesting. i'm wondering if something similar has been done to my car. its sort of a mystery to me, having just purchased it in january and it being subject to half its life in the garage under warranty with two bent exhaust valves. they said its most likely caused by a vtec controller or tune, and as i've said i have quite the mystery car. somehow, some way, it seems like i have a sort of tsudo i-vtec vtec?

sometimes it engages and 4200 rpms, sometimes 5500 rpms, anyhwere in between, and sometimes not at all. it seems to respond to my driving style. it ranges anywhere from 4200, to 5500, to no vtec if i am gentle on the throttle. my rev limit also happens to be my red line? sorry to thread jack, but if anyone knows what was done to my car, being previously owned by an old banker..? let me in i'm curious.

as for performance; well i've gotten my heads rebuilt by a local machine shop because of valve damage, and i've installed a k&n typhoon. with help of whatever ecu modding has been previously done, i'm estimating some significant power increase. my accord keeps up with E36 M3's and an 06 rsx-s my buddy has. gives my friends 99 si full bolt ons a run for its money, and etc...
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Old April 20th, 2011, 05:31 PM   #9
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My take on this is that Honda provided VTEC as a luxury when they put it on our J30s...with that said such a luxury can't exist all the time during regular driving (at lower engine speeds) where fuel economy is desirable.

Instead, as far as the stock J30 motors go, inexpensive materials that go into its feed assembly, valve seat surfacing and seals... have an expected (tested) life expectancy before an overhaul or part replacement is necessary. In other words, does it make sense to say by advancing the VTEC engagment will cause premature wear just the same as Honda's desired factory settings, but at a much faster rate.

With the variable intake manifold actuator valve design, Honda has provided a 'middle man' to gain momentum right? - kind of like a smooth transision into VTEC engagment so could we expect that the 'middle man' also needs to be advanced prior to VTEC's advancement in order for a smooth operation to remain?
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Old April 21st, 2011, 06:29 AM   #10
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Possibly, sounds very logical. However, what about civics and integras that have VTEC on the intake and exhaust that activate at the same time. And when it does theres usually nothing smooth about it, it just kicks hard.
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Old April 21st, 2011, 07:59 AM   #11
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well i say the best VTEC is one you dont hear or feel becuz u will be complimenting the engines powerband...and the reason it kiks so hard on 4 cylinders is due to lack of torque and usually from the factory ECU it is engaged way late in the powerband....my point here is, is this possible? what happens if you jump a couple wires from the butterfly actuator to your VTEC solenoid but not disconnect anything so you dont throw a CEL? if you are already in VTEC @4000RPMS then the ECU tries to kik VTEC @4800RPMS what will happen? lol...and i am a strong believer that honda could care less about the J30 being a performance engine they jus created a mild performing V6 to suit a consumer majority. Think of it this way why do manufacturers IE: Honda put 3 Catalytic converters an a car? becuz there are certain requirements manufacturers must follow in order to produce a product. does this mean the cats give you the best performance? I think we all know the answer to that is HELL NO!...point being there are lot of reasons why this engine is being held back and possibly lowering VTEC while it may not give substantial gains it may leave you in a desirable powerband and lessen the wear and tear on your motor becuz the engine doesnt have to keep re-engaging
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Old April 21st, 2011, 08:21 AM   #12
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VTEC engages based on throttle position, rpm and oil pressure.

you best bet is to get a set of cams.
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Old April 21st, 2011, 08:31 AM   #13
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Quote:
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VTEC engages based on throttle position, rpm and oil pressure.

you best bet is to get a set of cams.
ok so it could be possible that there would not be enough oil pressure to engage at such a low RPM? becuz others here have posted they have engaged at 4300RPMS which i think is the lowest someone said?
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Old April 21st, 2011, 08:38 AM   #14
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Moving VTEC x-over point back on engines like the F20C and those high-strung K20's in the RSX and Si makes sense because dynos have shown that Honda intentionally held the normal cams 500-1000rpm longer for the pure intention of creating a "kick" when it finally switched over to the VTEC cam, just for fun. If you move the x-over point back you can recover that power but lose the kick.

I don't think this is the case on the J30A4/5 engines, which on dynos have always shown a very smooth almost imperceptible transition point (around 4800?) on dynos, which suggests the x-over point is already optimal. You could try moving the x-over point back to 4000rpm, but you might actually be losing power. You'd have to dyno it before and after to really know.

I don't think the high(er) VTEC x-over point on these engines has anything to do with wear considerations. VTEC was 3500 on the J30A1, and on some of the VTEC-E engines where an intake valve is shut down at low RPMs, the x-over point is down in the 2000rpm range, which you're going back and forth between all the time. I've heard of them before, but it's exceedingly rare to ever have a VTEC system related malfunction or failure on any of Honda's cars, so I really don't think that's an issue. Honda will put the VTEC x-over point where ever they think is best based on the system design and goals, and the specific RPM isn't going to have any real impact on reliability or durability. Honda's SOHC VTEC engines are very elegant and actually relatively simple designs in today's world, and are well-proven and tested designs.
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Old April 21st, 2011, 08:46 AM   #15
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I should look into this on my J35.... both when the butterfly opens at 4k and when vtec engages there's a significant kick.... meaning the engine is starved for air before those engagement points.
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Old April 21st, 2011, 02:26 PM   #16
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I should look into this on my J35.... both when the butterfly opens at 4k and when vtec engages there's a significant kick.... meaning the engine is starved for air before those engagement points.
i agree becuz i know i do feel a kick when VTEC engages...i will look into this as soon as i can however i wanted to get alot of opinions from everyone as to what they think will happen...pros/cons...great info here keep it comin!
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Old April 21st, 2011, 02:28 PM   #17
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Originally Posted by SteVTEC View Post
Moving VTEC x-over point back on engines like the F20C and those high-strung K20's in the RSX and Si makes sense because dynos have shown that Honda intentionally held the normal cams 500-1000rpm longer for the pure intention of creating a "kick" when it finally switched over to the VTEC cam, just for fun. If you move the x-over point back you can recover that power but lose the kick.

I don't think this is the case on the J30A4/5 engines, which on dynos have always shown a very smooth almost imperceptible transition point (around 4800?) on dynos, which suggests the x-over point is already optimal. You could try moving the x-over point back to 4000rpm, but you might actually be losing power. You'd have to dyno it before and after to really know.

I don't think the high(er) VTEC x-over point on these engines has anything to do with wear considerations. VTEC was 3500 on the J30A1, and on some of the VTEC-E engines where an intake valve is shut down at low RPMs, the x-over point is down in the 2000rpm range, which you're going back and forth between all the time. I've heard of them before, but it's exceedingly rare to ever have a VTEC system related malfunction or failure on any of Honda's cars, so I really don't think that's an issue. Honda will put the VTEC x-over point where ever they think is best based on the system design and goals, and the specific RPM isn't going to have any real impact on reliability or durability. Honda's SOHC VTEC engines are very elegant and actually relatively simple designs in today's world, and are well-proven and tested designs.
VTEC also engages or disengages based on Throttle position so i think in those VTEC-E engines when you are above the Vtec point and the throttle position is very low the engine will still only operate on less valves until the throttle is depressed past a certain point?
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Old April 21st, 2011, 02:38 PM   #18
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yo...

car pulls hard .....according to butt dyno (I know everyone prolly says that)
at 4000 to 4200 or 4300rpm you get a slight stumble if you sit at the rpms listed above with barely any throttle....otherwise no problems...i did remember that once you shift pass 1st or 2nd in WOT you never get below 4500rpm...I think that is why I had mine set at 4300rpm....
I can give you a measured response on May 1st....also I am going to try to hook up my oil pressure guage before then so I have a reading of oil pressure throughout the rpm band...
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Old April 21st, 2011, 02:52 PM   #19
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^^ So you switched it to 4000RPM and the butt dyno enjoyed? That's good to know although it's hardly factual evidence lol.

If you shift at redline you will never dip out of VTEC. The only shift you have to be careful with is the 2-3, because you can drop below VTEC. Otherwise, the 1-2 you spin so the revs don't drop that much, and 4th drops to about 5100.
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Old April 21st, 2011, 03:56 PM   #20
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my vtec kicks in at 4950 rpm....sounds and feels good

j35a8.
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Old April 22nd, 2011, 02:33 AM   #21
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Quote:
Originally Posted by SteVTEC View Post
Moving VTEC x-over point back on engines like the F20C and those high-strung K20's in the RSX and Si makes sense because dynos have shown that Honda intentionally held the normal cams 500-1000rpm longer for the pure intention of creating a "kick" when it finally switched over to the VTEC cam, just for fun. If you move the x-over point back you can recover that power but lose the kick.
perfect example of acceleration and jerk in physics terms. and for you non-physics people, im talking about another definition of jerk.

jerk is defined as the change in acceleration and thats what happens when you go from a stop, the change of acceleration from 0 is greatest at that point and you feel like you are being pulled back. for example if you accelerated uniformly, you would have 0 change in acceleration, leading to no jerk at all. acceleration is defined as the change in velocity and that feels different than the change in acceleration, it wont "jerk" you back in your seat as hard.

so back on topic to the vtec crossover point. having a high crossover point allows for a high value of jerk because the change in acceleration is greatest, making it feel like the car is really fast.
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Old July 26th, 2011, 07:03 AM   #22
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Bringing this thread back. Has anyone had any postitive experiences with this? Or has anyone tried it?
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Old July 26th, 2011, 07:08 AM   #23
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yo...

i forgot to write back....

at 4K rpm either enough oil pressure is not there or ecu does not like it...i got some weird codes and car ran very sluggish until 5K....I have it back at 4300rpm...

i have a oil pressure gauge...just not wired in yet....will be working on that this September or October....
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Old July 28th, 2011, 12:01 AM   #24
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I'm no pro, but I think (as stated by some people) the oil pressure would be too low for VTEC and not run sluggish at 4k. But that being said wouldn't having it wired up to kick in a 4k cause your MPG to drop like a fat kid out of a bunk bed?
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