VTEC Engagement at will

[JSecrest]

Has anyone ever jumped the spool soleniod valves to cause VTEC to be engaged at other than the usual high RPM. (I may not have the technicals down since my mechanic did this at idle :redface: years ago while trying to diagnose a VTEC problem). It would seem that the higher cam profile might:
-Make idle sound more aggressive.
-Improve the sound of the car at all sub-VTEC RPM ranges, during deceleration, etc.
Obviously, this would reduce ow RPM performance and drivability so one might want to control this full time engagement with a manual switch if it does improve the sound. One of the reasons for my curiousity on this subject is that I'm convinced that a large cam profile good to 8500 rpm is one of the things that makes Ferraris sound so great (and also gives them their pathetic fuel economy ratings).

 

[NSXGMS]

Has anyone ever jumped the spool soleniod valves to cause VTEC to be engaged at other than the usual high RPM. (I may not have the technicals down since my mechanic did this at idle :redface: years ago while trying to diagnose a VTEC problem). It would seem that the higher cam profile might:
-Make idle sound more aggressive.
-Improve the sound of the car at all sub-VTEC RPM ranges, during deceleration, etc.
Obviously, this would reduce ow RPM performance and drivability so one might want to control this full time engagement with a manual switch if it does improve the sound. One of the reasons for my curiousity on this subject is that I'm convinced that a large cam profile good to 8500 rpm is one of the things that makes Ferraris sound so great (and also gives them their pathetic fuel economy ratings).

I'm not sure who would spend any time or money to severely compromise the performance of their car for a better sound but it's not me.

Wouldn't any Ferrari that has an 8500 redline also have their version of VTEC? You shouldn't have a inappropriately low cam profile at a lower RPM in any modern Ferrari (360, 430, 612, 599, Enzo). You should have the same cam characteristics as Honda's VTEC overall, no?

 

[Hugh]

It would seem that the higher cam profile might:

make your engine run like it was being fed a cocktail of diesel fuel and urine.

 

[Shumdit]

Has anyone ever jumped the spool soleniod valves to cause VTEC to be engaged at other than the usual high RPM. (I may not have the technicals down since my mechanic did this at idle :redface: years ago while trying to diagnose a VTEC problem). It would seem that the higher cam profile might:
-Make idle sound more aggressive.
-Improve the sound of the car at all sub-VTEC RPM ranges, during deceleration, etc.
Obviously, this would reduce ow RPM performance and drivability so one might want to control this full time engagement with a manual switch if it does improve the sound. One of the reasons for my curiousity on this subject is that I'm convinced that a large cam profile good to 8500 rpm is one of the things that makes Ferraris sound so great (and also gives them their pathetic fuel economy ratings).

There are a few companies that make VTEC controllers to alter the switchover point, but there is some dispute about their effectiveness.

 

[Hugh]

There are a few companies that make VTEC controllers to alter the switchover point, but there is some dispute about their effectiveness.

The same thing could be said for a few companies that make "controllers" to alter the shine of your paint.

Damn! What a great marketing angle! First we had wax, then paste, then conditioner, then glaze. Ladies and gentlemen, please welcome the newest slogan to describe the same old crap....let's hear it for Mr. Finish Controller!

Am I a genius or what? :biggrin:

 

[Shumdit]

The same thing could be said for a few companies that make "controllers" to alter the shine of your paint.

Damn! What a great marketing angle! First we had wax, then paste, then conditioner, then glaze. Ladies and gentlemen, please welcome the newest slogan to describe the same old crap....let's hear it for Mr. Finish Controller!

Am I a genius or what? :biggrin:

When I got the email notification about this post of yours, I started reading the post in the email without noticing who posted it. I was not through the first sentence before I knew it was you. That scares me a little:biggrin:

 

[02#154]

The same thing could be said for a few companies that make "controllers" to alter the shine of your paint.

LOL... Damn Hugh, just let it go!:biggrin:

J

 

[JSecrest]

I am not talking about full time engagement which would obviously impact performance as I stated. Perhaps, one would find that the sound during deceleration was improved (no performance loss) or perhaps the VTEC could kick in at 3500 rpm vs 5500 with relatively little impact on performance but a much neater sound. Remember, people spend $5,000 for exhausts to make an already great sounding Ferrari even better. When I heard my car idling with the VTEC engaged, I do not recall it running poorly.And I mentioned having the ability to engage the alteration only when desired, either by program or manually. I don't believe it would be that difficult a modification.
I may be mistaken, but I do not recall Ferrari having a variable cam despite its high RPM capability and certainly cars like the current Z06 Vette and Viper do not despite high redlines. With the right exhausts, they sound great and low rpm torque and drivability are great.

 

[95EagleAWD]

.
I may be mistaken, but I do not recall Ferrari having a variable cam despite its high RPM capability and certainly cars like the current Z06 Vette and Viper do not despite high redlines. With the right exhausts, they sound great and low rpm torque and drivability are great.

I don't think Ferrari's do.

With the Vette Z06 and Viper, they make great low rpm torque because they are 7.0 and 8.3 litre engines. Cubic inches = Torque.

 

[nsxsupra]

I am not talking about full time engagement which would obviously impact performance as I stated. Perhaps, one would find that the sound during deceleration was improved (no performance loss) or perhaps the VTEC could kick in at 3500 rpm vs 5500 with relatively little impact on performance but a much neater sound. Remember, people spend $5,000 for exhausts to make an already great sounding Ferrari even better. When I heard my car idling with the VTEC engaged, I do not recall it running poorly.And I mentioned having the ability to engage the alteration only when desired, either by program or manually. I don't believe it would be that difficult a modification.

Why not be the first and give it a try and let us know how it work out. Worst case scenario you can also reverse it and return it to stock engagement point.

 

[Bob Kenney]

An AEM is capable of being programed to engage the V-tech at almost any rpm you desire.
TODA Racing also has very aggressive cams for the NSX that completely eliminate V-tech since they are for race engines that only operate at high RPM and they eliminate the oil pressure fluctuation caused by the engagement of V-tech.
Some after market "Chips" for the ECU will change the engagment rpm for V-tech.
To rig a manuel override to trigger V-tech mechanically can be done; but how the ECU will read these changes and react to them would be my question.

Bob

 

[NSXGMS]

I don't think Ferrari's do.

With the Vette Z06 and Viper, they make great low rpm torque because they are 7.0 and 8.3 litre engines. Cubic inches = Torque.

From Wikipedia:

In 2002, Maserati launched the Coupe and Spyder, based on the 3200 GT, which is not sold in the United States. Both models have a normally aspirated 4.2 L engine producing 390 bhp (291 kW). The top speed is 177 mph (285 km/h), while 0-60 time is 4.9 seconds. The V8 engine was designed by Ferrari but built by Maserati. It has variable valve timing on the intake side only, while a highly developed version of this engine used in the F430 had variable valve timing on both intake and output sides.

 

[95EagleAWD]

Well, there we go.

Question answered.

 

[Hugh]

When I got the email notification about this post of yours, I started reading the post in the email without noticing who posted it. I was not through the first sentence before I knew it was you. That scares me a little:biggrin:

As long as your masculinity isn't threatened you'll be just fine.

 

[Hondatech]

The VTEC system is actuated with engine oil pressure. If it's activated at too low an RPM, the oil pump will not be able to supply the volume necessary to keep up oil pressure, and may result in engine damage. So be careful if you're going to experiment with this :wink:

 

[hondakingDOM]

great way to jump timing or engaging vtec too early breaks timing belt:biggrin:

 

[Bob Kenney]

The VTEC system is actuated with engine oil pressure. If it's activated at too low an RPM, the oil pump will not be able to supply the volume necessary to keep up oil pressure, and may result in engine damage. So be careful if you're going to experiment with this :wink:

VTEC requires 4 conditions be meet before the ECU will send the signal that engages its operation: 1. engine rpm must over 5800, 2. water temperature must be over 140 degrees. 3. the car must be moving in excess of 3 MPH, 4. if the load on the engine is excessive VTEC will not engage.
Do you know off-hand what volume of oil flow is needed by operation of VTEC; I am not sure of the minimum oil pressure required to operate it safely. I am under the impression that oil pressure is allowed to pass to a "Hydraulic Piston" by the actuation of a solenoid which operates a spool valve.
There is 1 piston located at each set of 3 cam followers. That piston then becomes the locking mechanism that links the larger center "high speed cam follower" to the cam followers that ride the low speed cam lobs which actually operate the valves.
I do not believe the oil volume needed to operate these pistons is very great; it only provides the needed hydraulic pressure to actuate the locking mechanism's pistons. The volume of oil required for this actuations is diverted from the flow through oil lubrication system. This diverted oil dose not flow through per-say; it "bleeds" through small orifices providing some lubrication but primarily provides pressure against the locking piston. This is my impression after disassembly of my valve train. If my perception is incorrect please let me know.

Bob

 

[JSecrest]

You know far more about this than I, however the amount of oil diverted must be substantial to result in the two or threee bar decrease in oil pressure which results when VTEC engaged. I believe this oil pressure drop is one of the recommneded way of determining if VTEC has engaged.

 

[Bob Kenney]

You know far more about this than I, however the amount of oil diverted must be substantial to result in the two or threee bar decrease in oil pressure which results when VTEC engaged. I believe this oil pressure drop is one of the recommneded way of determining if VTEC has engaged.

Please don't take my post wrong; I like your idea and believe pursuing it is a worth while venture. I have felt that for a boosted car VTEC comes in on the late side and there may be something to gain having it engage earlier.

I truly want to know if my perception of the oil flow is incorrect. I know I am concerned enough about the oil pressure drop at VTEC inception to be going to a high volume oil pump and adding additional capacity at the pan for the next engine build. I am also considering the addition of an AccuSump oil reserve system to assure that the engine never sees an oil starved condition.

I know that Honda has engineered the system and it should be perfectly fine but it seems to be counter intuitive to have an oil pressure drop as the RPM and stress on the engine is increasing. In a boosted motor this level of stress is dramatically increased. I am just looking to play it safe and prolong the life of the engine; its dependability coupled to increased power output that I am seeking.

The best of luck with your project. If I can be of any assistance don't hesitate to ask; please keep me informed of your progress, I am truly interested.

Bob

 

[NSXDreamer2]

VTEC requires 4 conditions be meet before the ECU will send the signal that engages its operation: 1. engine rpm must over 5800, 2. water temperature must be over 140 degrees. 3. the car must be moving in excess of 3 MPH, 4. if the load on the engine is excessive VTEC will not engage.
Do you know off-hand what volume of oil flow is needed by operation of VTEC; I am not sure of the minimum oil pressure required to operate it safely. I am under the impression that oil pressure is allowed to pass to a "Hydraulic Piston" by the actuation of a solenoid which operates a spool valve.
There is 1 piston located at each set of 3 cam followers. That piston then becomes the locking mechanism that links the larger center "high speed cam follower" to the cam followers that ride the low speed cam lobs which actually operate the valves.
I do not believe the oil volume needed to operate these pistons is very great; it only provides the needed hydraulic pressure to actuate the locking mechanism's pistons. The volume of oil required for this actuations is diverted from the flow through oil lubrication system. This diverted oil dose not flow through per-say; it "bleeds" through small orifices providing some lubrication but primarily provides pressure against the locking piston. This is my impression after disassembly of my valve train. If my perception is incorrect please let me know.

Bob

wow, thanks Bob, I must admit that I don't know VTEC needs all of those 4 conditions to engage...... So is that why there's difference we reving our car to "test" the exhasut note vs the car is in motion??

 

[Elite]

Well we've played with the Vtec points on many cars, NA and FI. Honda has it about right. There isn't too much play with the engagement point that doesn't hurt the power curve. It may however move a couple/few hundred either way. There is generally a sweet spot you can find on the dyno. But really, there aren't any real gains to be had as far as we have seen.

I'll play with it on mine, with a big turbo, and some fairly high boost levels, and let you know if there is any improvement in the power curve.

Also, isn't it true, that the Vtec will disengage if the oil pressure drops too low? I believe this is one of the topics the road racers have talked about. I think it needs 57? I'm not sure on that, because I should be sleeping right now. :tongue:

 

[JSecrest]

Elite, I'm not suggesting a performance improvemnent. I'm wondering of exhaust sound can be improved in lower ranges. With a turbo, I expect you would be less likely to notice.

 

[Bob Kenney]

wow, thanks Bob, I must admit that I don't know VTEC needs all of those 4 conditions to engage...... So is that why there's difference we reving our car to "test" the exhaust note vs the car is in motion??

Any engine under load will sound different than one that is static reving. Listen to the sound of Harley when they static rev and then when they accelerate hard.
The high speed profile of the cams in the NSX motor have more lift and more duration or overlap in the valve timing than the low speed cam profile. The reason for cars with very aggressive cam profiles to run rough at idle is the overlap between the intake and exhaust vales. This means that the the valves are opened at the same time. Without the inertia of high speed air/fuel and exhaust gas flows they don't work very well. On a typical Big Block Detroit engine these cams did not function well below 3 thousand RPM. Above that point is were they really came into there own.
I drove a car that had 328 degrees of duration, 12.7 compression and a 3800 lbs clamping force clutch; driving this beat on the street was not easy in traffic. I am glad for the advance of VTEC which allows the car to be much bettered mannered around town; although I some times miss the rup, rup, rup of that bid block wanting to be let loose. As you well know, VTEC is the solution to this problem for a street driven car, we have a cam profile that idles well then shifts to a more aggressive profile between 5800-6000 RPM.:biggrin: I feel the high speed profile could be even more aggressive but thats a whole different discussion.
As for engaging VTECH at will at any RPM that would be a very interesting experiment. I understand it may have the desired effect sought by JSecrest; engaging the high speed profile to give the engine that lope like a Detroit Big Block; as I said I have soft spot for that sound given my sorted past as a drag racer.:wink:

Bob