VTEC-HOWS IT WORK THEN

[icepop]

I remember, a while back, looking into how the VTEC system worked on the CTR engine. I was curious as to how Honda managed to achieve such reliability from what is a bit of a screamer.

I remember the buff I found suggested that the cams had two cam followers, and at a certain revs the second follower was locked into position by a metal rod, and activated the more aggresive cam profle. I understood this therefore to be a mechanical, rather than electronic system. If I'm wrong the rest is rubbish and I'll go away and hide.

Just looked at an advert/description of a chappies Elise with CTR convertion, and it suggests that the VTEC cut over has been lowered to xx revs by a re-map. If mechanical, how's that done then, surely the VTEC is fixed ?

Thanks

[hondafanatic]

icepop said:

I remember, a while back, looking into how the VTEC system worked on the CTR engine. I was curious as to how Honda managed to achieve such reliability from what is a bit of a screamer.

I remember the buff I found suggested that the cams had two cam followers, and at a certain revs the second follower was locked into position by a metal rod, and activated the more aggresive cam profle. I understood this therefore to be a mechanical, rather than electronic system. If I'm wrong the rest is rubbish and I'll go away and hide.

Just looked at an advert/description of a chappies Elise with CTR convertion, and it suggests that the VTEC cut over has been lowered to xx revs by a re-map. If mechanical, how's that done then, surely the VTEC is fixed ?

Thanks

You can alter the change over point as it's governed by the ECU.

If you have an iVtec which the EP3 onwards are, there are two change over points depending on throttle position. WOT and the change over is lower than if you are, say, 25% open throttle.

If/when you lower the change over point, you need to have it mapped properly and as a general rule you'll chuck more fuel in. When you start going down this route, you generally lose the 'kick' and it becomes a very smooth crossover. On one of my EP3s, I have WOT set to 4300 and partial throttle set to around 6200 which meant I could cruise in 6th without engaging Vtec.

The older Vtec engines could be altered with an aftermarket bit of kit that could alter the changeover point on the fly...but to be honest, in my experience, it just created more noise if it wasn't mapped properly.

HTH and the above is in my experience only, I'm not talking as a professional

[icepop]

Thanks for the reply, did a bit more digging and found that their is a solenoid that, when activated, supplies oil hydraulic pressure to engage the pins locking the vtec system. This being the case, I see now how the ECU map can be altered to affect the vtec system.

Previous info, (wrong!), had told me the pins were actuatted by centrifugal force.

What a clever system.

When these factory maps are altered, are things like fueling parameters altered at the same time, as happens when turbo'd cars are re-mapped ?

[hondafanatic]

icepop said:

Thanks for the reply, did a bit more digging and found that their is a solenoid that, when activated, supplies oil hydraulic pressure to engage the pins locking the vtec system. This being the case, I see now how the ECU map can be altered to affect the vtec system.

Previous info, (wrong!), had told me the pins were actuatted by centrifugal force.

What a clever system.

When these factory maps are altered, are things like fueling parameters altered at the same time, as happens when turbo'd cars are re-mapped ?

If you take a look at something like a Hondata Kpro, just about any paramater can be altered while on a rolling road or out on the road. Although you need to stop, ignition off, flash the ECU (You get a USB port fitted onto the USB) and start up again with the new updates.

You can download the software for free and have a look at all the options...You have a sudo launch control system, you can alter the rev limiter, and blow the engine up if you don't know what you're doing

Link to software http://www.hondata.com/kmanager.html

Brilliant bit of kit that I had many many hours playing with.

[havoc]

If you really want to see what can be done with this tech, google A-VTEC.

This was to be the next stage from Honda (continuously variable timing AND lift, IIRC), but seems to have quietly died, I suspect because it was quite expensive for not-that-substantial economy gains in a world where diesels and hybrids are suddenly getting all the attention...