Vtec not engaging?

[jonnya_nsx]

A friend if mine who races boosted civics rode in my car with me the other day and when i laid into it he noticed that my vtec never kicked in. I have had the car since April and never really realized until he said something. Any clue what it could be?

 

[bngl3rt]

I've wondered something similar... in my experience, the NSX does not have quite as obvious of a change in character when VTEC kicks in as some other Hondas do. You can find lots of "Integra VTEC kicks in" videos on Youtube that really show a dramatic difference in the last 2k of the rev range. Under most circumstances the NSX does not seem to be like that, and accelerates smoothly up through 8k.

The only time I've noticed a real change in character and a serious, unexpected "kick" is during double-clutch downshift into 2nd gear when going for really hard acceleration from a rolling start. The progression from 5k up through 8k sounds a lot different there than it does just smoothly accelerating through 2nd gear from an upshift leaving 1st. This leads me to believe that the there are a lot more factors besides just pure RPM in the VTEC engagement algorithm.

Just my amateur observations. I'll let the experts chime in now

 

[A.S. Motorsport]

V-Tec can have a error it isn't purely mechanical.
Can you take a video or tape the engine note going trough the rev range

 

[Caroline-NSX]

Another thing you can do is reset your computer and see if that works. I had that problem in the past with my first NSX. It was park for awhile. Took it out one night and I knowest my vtec wasnt kicking in like it suppose too so i reset the computer took it out on the freeway and vtec work fine again. Doesn't hurt to try. Take only 2 mins :wink:. Hope this help :smile:.

 

[bngl3rt]

I always assumed if VTEC (being a function of the ECU) wasn't working properly, you would light up a CEL...

 

[jonnya_nsx]

V-Tec can have a error it isn't purely mechanical.
Can you take a video or tape the engine note going trough the rev range

Here ya go. https://www.youtube.com/watch?v=H9sC26Om62Q&feature=youtube_gdata_player

 

[chudson1549]

Search this site. NSX v-tec is not as noticable as other V-tec engines. If you had a bad V-tec solenoid it should throw a code. They are several threads about this. HTH

 

[A.S. Motorsport]

I can't hear v-tec engaging ether, since it's a dyno pull do you have the sheet?
I'd expect with such a open exhaust to hear it phasing to high lift, although not hearing it doesn't mean it ain't working.

Can be a couple of issues, solenoid or electrical (end of the head there is a V-Tec solenoid)
That being said, B-Series v-tec is a real kicker and more noticeable

 

[jonnya_nsx]

I can't hear v-tec engaging ether, since it's a dyno pull do you have the sheet?
I'd expect with such a open exhaust to hear it phasing to high lift, although not hearing it doesn't mean it ain't working.

Can be a couple of issues, solenoid or electrical (end of the head there is a V-Tec solenoid)
That being said, B-Series v-tec is a real kicker and more noticeable

I attached the picture of the sheet. How can you check the solenoid?

 

[ralph cerbone]

just watch oil presure gauge , at before 6k the pressure will drop

 

[Pchpleno]

Looking at the graph looks like it is working as you can see the torque curve raises a bit around 6000. It shows earlier on the graph but that could be small variances in the rpm ready of the dyno

The nsx doesn't need such hard engagement cause it was designed to have a very linear torque curve and the heads flow really good before 6000

 

[A.S. Motorsport]

Graph looks fine, you can see the secondary curves.

 

[NSX1145]

Looks good to me

 

[JCastro]

VTEC change over in the B series engines are very obvious. The most obvious is that of the B18C1 (USDM GSR) which uses a dual intake runner manifold. Just after VTEC engagement, butterfly valves in the intake manifold open allowing air to enter via secondary intake runners and significantly changing the engine sound. It's also very noticeable in the B16A's (Civic Si) as well as the B18C5 (ITR) when equipped with aftermarket intakes. The dyno sheet you posted does show that VTEC is indeed engaging. No worries.

:smile:

 

[jonnya_nsx]

Thanks for your help everyone. You guys are the best more i need to get those numbers up. First up is injectors and tune

 

[A.S. Motorsport]

VTEC change over in the B series engines are very obvious. The most obvious is that of the B18C1 (USDM GSR) which uses a dual intake runner manifold. Just after VTEC engagement, butterfly valves in the intake manifold open allowing air to enter via secondary intake runners and significantly changing the engine sound. It's also very noticeable in the B16A's (Civic Si) as well as the B18C5 (ITR) when equipped with aftermarket intakes. The dyno sheet you posted does show that VTEC is indeed engaging. No worries.

:smile:

Yes old V-Tec CRX's really kick.
Funny thing is C32A and C35A Legend engines have the aggressive three phase VISS manifolds and it sounds just like V-Tec it fools tons of people

 

[NSXCessive]

I also going to throw this one out there... stung me on my old B16A1 in an Integra I use to have. Be sure the oil level is topped up, otherwise it wouldn't engage VTEC no engine light either. Not sure if the NSX would do the same thing, I've never let the oil level hit the low mark on mine. I do have to agree with others on here as the engagement on the NSX is more subtle and not as harsh and a 4 cyl motor.

 

[A.S. Motorsport]

The NSX ECU indeed checks for oil system status to activate V-Tec it also won't engage on a cold engine.
A decade later BMW M engines started using a system that slowly increased rev limited until the engine is warm.

 

[Briank]

A friend if mine who races boosted civics rode in my car with me the other day and when i laid into it he noticed that my vtec never kicked in. I have had the car since April and never really realized until he said something. Any clue what it could be?

Assuming you don't have a temp sensor issue the vtec operation is confirmed by a 2 pressure switches and you will get a CEL is there is a problem. You should see a dip in the oil pressure when in vtec. I think its working correctly you are just not comparing to a similar car/engine.

 

[ralph cerbone]

sounds about right Brian

 

[docjohn]

from time to time we get new owners saying thier car won't engage vtec or there is a powerloss...what they don't realize is that the engine oil and motor need to be at proper operating temps and at the correct level.