Please note: If you wreck your ride doing this, don't even think of blaming me or fitfreak. You perform this at your own peril. Honestly, don't mess around with it if you aren't ready to accept the possibility of buying a new engine. The same advice I'd give for anything engine mechanical related.

I was driving around late Monday night thinking about all sorts of odd things. Soft music in the background. Not a car on the road. Of course, the vehicle I'm driving creeps into my thoughts. As always I think to the future. I dream of turbo kits, cams, intake manifolds and all the other go fast goodies. I even think about how easy it would be to get a supercharger up and running if I only had 2000 dollars for a rotrex c15-60. But then I ask myself: why? The answer I come to is 'the dead zone'. That area between 4000 and 5400 rpms that is just too slow to wind up. It's such a dead zone that I frequently cruse on the highway at 70 mph instead of 80mph so that if I ever have to pass somebody I will end up in the nether regions of the rpm band in 3rd gear all the way to 95 mph (thanks to the 3rd gear AT magic rpm drop trick (seen here: ImageShack: Host and Share your Photos and Videos - file5942.mp4 If you haven't witnessed it)), rather than bogging in 4th at 4500 rpms. So, as I think about this, another thought enters my mind. VTEC. (it just kicked in yo) I recall that one member, through a series of tragic events, had a defective vtec solenoid which caused him to never enter the magical world of vtec. This got me thinking even harder. In other words the only thing controling the swtch to vtec cam lobes is a single switch, probably controlled by the ecu. Reflecting on the members who have tapped a light into the vtec circuit I realized I may be able to override that circuit and force vtec even earlier than intended. I asked myself if it would be worth it and I soon realized I could do this for free. I already have an RPM switch that was used to ensure I was spraying nitrous in the correct rpm window, and I could use it because I had taken out the nitrous for the winter already. I had plenty of wire and relays in my electronics locker. I was pumped and headed home. Ready to do battle regardless of if it would improve anything. Call it a proof of concept.

I fought long and hard with the ecu to let me into the sweet embrace of vtec. She is an angry bitch. Easily upset. Always forcing limp home mode at the slightest provocation. She has to see a solenoid. Absolutely must trip a solenoid when she is ready. She even checks to see if the vtec solenoid is working as soon as you start the car up. But luckly she can not tell a vtec solenoid from the solenoid inside of a common electronics relay. So I used this against her and after much trial and error I found the solution.


As you can see the ecu believes it is in control because whenever it tries to turn on vtec, relay 1 is tripped, and power is supplied to the vtec solenoid just as if she was doing it herself. Little does she know relay 2 was just engaging vtec prior to her arrival. There is a milisecond between relay 2 getting cut off and relay 1 engaging as the relay solenoid must travel for a tiny fraction of a second between the 2 circuits. This leads her to believe that vtec was never on before her arrival. Because if she finds out that vtec was already on when she tries to turn it on, she will become very cross with you and shut everything down to 3700 rpms and lower until you turn her off and on again. This is why you can't just eliminate relay 1 and splice relay 2 directly into the vtec solenoid circuit.

(isn't amazing how personifying an engine control module makes everything easier to understand?)

Wait! What? you call this a DIY? All it is, is a circuit diagram. Thats right. This is all I'm giving you. You can figure out the rest so you can have some semblance of the satisfaction of completing a DIY you thought through yourself. Maybe that feeling of accomplishment will inspire you to make a DIY of your own for some other project.



By the time I was done I had made one hell of a mess out of my engine bay



luckily wire loom makes everything look more organized than it really is...




There will be no DIY for the oil catch can. There's already a million of them indexed on google. Seriously

But how does she motor, you ask? Well, the rpm switch gives me alot of flexibility. I am still road testing it. I can tell you as of now that 4500 rpms and 4800 rpms is too low. However, I am having great success with 4950 rpms as the crossover point. I am yet to trip 'limp home mode' at this activation point. Even at 100 mph with full aero loading. Also my 0-60s are improving by 0.1 to 0.2 seconds. I have a feeling that this short lean burst is causing the ecu to richen up my long term fuel trims. This project as a whole is little more than a proof of concept. It did give me faith in my car as platform again. A cry for help if you will. A cry to Hondata to save me from myself before I end up slapping on a blow through carb and a rich/lean mixture adjustment lever ala Cessna. GIVE ME FLASHPRO @#*%$^&!

Thank You.

Edit: and for the love of all that is not rice, please, please solder your conections into the wiring harness. Don't let that $&%# rot out on you.

You may find the following helpful
https://www.fitfreak.net/forums/2nd-...ow-switch.html - to wire up the rpm switch

https://www.fitfreak.net/forums/2nd-...threshold.html - my trials and tribulations it getting her up and running.

 

Well, this is interesting. I have it set now at 5000 rpms. No check engine. No angry ecu. All was well. Ecu was even starting to get used to it and I started consistently putting down 0-60s in 10.3-10.5 range per stopwatch and 'light em up' (the free or $5 version of dynolicious but with all the same features except lots of Bosch advertisements) but today I filled up on 87 octane and suddenly I'm putting down 0-60 in 11.2-11.4 maybe a coincidence but I've never had the octane rating affect my 0-60 before. Maybe it has something to do with the vtec point :/ can't say for sure. Here's to A/T + brake torque for consistency in testing.

 

a true pioneer. doing all the homework and experiments so we dont have to. lol

 

Hello,

I found this thread from you about VTEC activation mode while I was searcing for solutions to my problem...

I just install my boomslang wiring harness today and connect it with my brand new AEM F/IC-6 where I put a base map and use the 12Volt SWITCHED DC output to control the VTEC on and off at 14psi and 5,000 rpm.

Boomslang custom modified the harness for this vtec activation purpose.
Problem is I got this OBD error code P2649 with VSA light turn on.
I ask boomslang and he said because he reroute the VTEC solenoid wiring from stock ECU to F/IC but since the F/IC do not have output back to ecu, the ECU see that it no longer have connection to the VTEC solenoid thus issuing an error code P2649.
I have not drive my car yet, but my question is,
will this error code make the car goes into limp mode?

If I purchase an extra VTEC solenoid to fool the ECU will this work?
or how about if I make a jumper cable and reconnect the ECU to the VTEC solenoid while at the same time
the F/IC also connect to the solenoid... will this work to eliminate the OBD error code while at the same time activate the VTEC at lower RPM from the F/IC?
How did you successfully do your modification?

Thanks

 

Today I just plug back the factory ECU and everything work fine again.
turn out if you get this VTEC error code, the VSA light will stay on also...

so I have this pictures of the Honda Fit ECU Pin Out:



It show that the Pin 35 on ECU connector B is the one who send signal to the Rocker Arm Oil Control Solenoid.

My question is, do this signal from ECU is the one that also really drive the solenoid, or is it just a signal to a relay on the solenoid?
The reason because I plan to use AEM F/IC Switched 12 volts out to drive this VTEC but the AEM F/IC only can produce maximum of 1 ampere,
I worry this might overload the AEM F/IC.

I wish the pictures of the circuit diagram that Lyon make for his VTEC activation is still available so I can review and learn...

I also don't get it on what Lyon means by relay 1 and relay 2 and relay 2 must be turn off when relay 1 is activated by the ecu... because the ecu don't want to see the VTEC already activated...
couldn't we just use DIODE?

here is what I think,
let the ECU wiring pin 35 still connect to solenoid but use DIODE inline on this wire.
then after this first diode, tap the same wire and connect it to the AEM F/IC or to a relay that control by the AEM F/IC but between this wire and the relay/AEM F/IC put another diode.
This way when the AEM sginal the solenoid to open at lower RPM, the
ECU can't see the signal but when the ECU finally catch up at higher RPM and sent the signal, it would not goes to the AEM (eventhough AEM will not be effected anyway, I just like the fact that there is 2 diode to limit the current only going 1 direction)...

or another solution...
perhaps if I buy a second VTEC solenoid and let the ECU get connected to the second VTEC solenoid thinking it operate a working solenoid although in fact it is just a dummy to trick the ECU... this will be a bit more expensive,
but I think this will give less problem...

Lyon, if you read this someday, please give me your advise.
Thanks

 

I manage to find the solution using the AEM F/IC-6 and Boomslang wiring harness,
NOTE:
Ups, after real world testing I now understand that 2 relay will be needed after all...
will post more once I bought a few fuse for this relay (have the relay but not the fuse needed)...
I will post it soon :-)

 

For anybody interested in doing this modification, (and since this thread by Lyon do not have any pictures anymore), I have the DIY and the wiring diagram posted here:
https://www.fitfreak.net/forums/2nd-...ml#post1348611