My tuner is trying to lower my vtec engagement point, but he is consistently running into an check engine light (code 1259). He says it has something to do with a problem with the vtec solenoid and the vtec oil pressure switch. My car is 200 miles away in his shop, so unfortunately I can't trouble-shoot it myself. Has anyone run into these problems while lowering vtec? I could use some ideas to throw his way so he can try to solve the problem.

 

Why in hells name would you lower your VTEC engagement?

 

I've seen a couple sgT tunings with some ridiculously low crossovers

 

any villages report a missing idiot?

 

Two towns over, they've been looking for him for DAYS!

 

mine is at 5k

nothing wrong with lowering vtec, as long as it makes more power, who cares where vtec gets set at

 

I did it long time ago with a Field Vtec Controller and my R is stock.
Did no HP gain, just noise maker at lower vtec crossover.

 

My VTEC is at 5250

 

sounds like the vtm wire isnt hooked up on your vtec controller

 

smooths out powerband

 

mines at 5300 any lower that that my car doesn't feel good

 

I appreciate the input so far. By lowering my vtec point to 4100rpm (it actually engages at 4400rpm), I picked up another 8-10whp in the midrange. I'm not using a vtec controller, but a piggyback computer called the unichip. The unichip controls my fuel mapping, based on boost, air temp and throttle position.

Steve, I wish I had the wiring schematic for the "vtec node" that my tuner installed to give me control over the vtec point, but I'll definitely pass your suggestion on to him.

 

not all the time.

 

4100? WHAT? hahaha DAMN that **** is O.C. man. Id bump it to at LEAST 5000 if you have an R. Do you have a GSR or somethin? Check the VTM. Other than that bump that Activation up. Sometimes i have see it throw a code for simply being too low. Friend has a b16 in EK and cant go under 5300 without the car throwing a check engine lamp.

4100...

 

I should explain, I have a jrsc'd type r, running stock 5.5psi. There may be a vtec point below which the factory ecu freaks out. If I've reached that point by going too low, I'd like to try and figure out exactly what parameters in the ecu I've exceeded.

 

Here is an email from my tuner describing his analysis of the problem:

"After studying the circuits and observing engine operation, this is how I
concluded the operation of the factory ECM/Vtec. When the ECM sends 12V
signal to actuate the Vtec solenoid, it then monitors the Vtec oil pressure
switch to confirm that the Vtec actually did actuate, like an answer back
circuit. If no answer back, it will set the service engine light and store a

1259 Vtec code. Or if the factory ECM ever detects Vtec oil pressure without

giving a signal to the Vtec solenoid, this would also set the code and
light.

The Unichip only sends a signal to the Vtec solenoid at the programmed
on/off
RPM setting. By setting the Unichip to a lower RPM Vtec on, it is possible
that the factory ECM was seeing a Vtec oil pressure signal when it was not
programmed to operate in the Vtec mode thus setting a code.

I installed a relay using the now unused factory ECM's Vtec solenoid signal
to activate a relay that used its normally closed contacts to send a false
Vtec oil pressure signal (answer back) back to the factory ECM to fool the
ECM into thinking that everything was operating correctly. This seems to
work fine when in the cruising mode but when at wide open throttle and at
the
factory Vtec 5600RPM, it sets the service light and code. Obviously I am
missing something here.

According to my circuit diagrams the Vtec oil pressure switch is normally
closed and only opens with oil pressure after the Vtec is activated, thus I
wired the relay this way.

Let me know if you find out that my theory of operation here is flawed."

Anyone have thoughts?

 

This may sound mean, but here goes...You all are idiots who think a lower vtec point is a bad idea. With boost it is better...In fact with my car the lowest I have set it and made tq and hp inprovements is 2000. I can't go any lower with the Hondata and I dont' think there will be enough oil pressure then to keep the main bearings oiled. Currently I have it set to 3000 rpm. Jim I'm about to call you.

 

Spunkster, thanks for calling me with the tech advice. I hope my vtec problem is just bad installation or faulty wiring, I'm going to take my car back tomorrow whether or not my tuner can figure out the problem. I'll let you know if it gets resolved, and more importantly whether I've outgrown my current engine management setup and need something else.

 

i'm also running a jackson supercharger... my vtec is set at 4750 wot.

lowering the engagement point seems to smooth out the powerband. i generally keep it between 4750 and 5250 depending on how much gas i feel like wasteing, but there is definately a difference when i lower the engagement point.

i don't have any problems with throwing engine codes.


[Modified by stormywaters, 8:47 PM 3/21/2003]

 

My vtec can hit at 1000 rpm, throttle dependiant

 

my vtec kicks in at 5000. gotta love v-afc

 

well i was against it becuase when we were street tuning it felt like **** once we got everything squared away on the dyno i gained hp by lowering it to 4800 and straightened out the TQ curve alot more .

 

<----- 4800 N/A gained 8-9ftlbs in the mid range with a smoother plot

With tuning lowering the VTEC cross-over can make some nice mid range gains, I reccomend I/H/E and a VAFC. Turns the R motor into a different animal....baselined 163....hoping for 185-187 with I/H/E/cam gears and VAFC I could probably squeeze out more with a better header but the JDM DC works okay..129ftlbs...cant complain

 

As your tuner has already confirmed it is indeed the VTM = Oilpressure switch

 

Just before I arrived at his shop, he did fix the vtec problem, and admitted that it was faulty wiring on his part. Anybody want to guess which wire he failed to tap into? The winner gets a "told ya so" from sgT.