___ Does V-Tec get better mileage at ALL speeds ? ?

When comparing a '96 Odyssey to a '98 Odyssey (which has V-Tec in
Canada), would you say that the '98 will get better mileage at all
engine speeds, or just when revving it up to the point where the V-tec
cuts in?

I.E.: Is this statement true?
Mileage is mediocre in both of the first generation Odysseys, but you'll
waste less gas when passing (or speeding or climbing hills) with the
V-Tec model....

Reply to group, thanks.

'Curly'

 

There is a difference, but you can't measure it. bob

 

There is a difference, but you can't measure it. bob

 

I disagree. The difference is huge.

It applies to all speeds and all vehicles -- even gigantic, gas-sucking
minivans.

V-Tec gives an engine two cam shafts - a high speed and low speed cam shaft.
Each cam shaft is optimized for its own speed range.

 

I disagree. The difference is huge.

It applies to all speeds and all vehicles -- even gigantic, gas-sucking
minivans.

V-Tec gives an engine two cam shafts - a high speed and low speed cam shaft.
Each cam shaft is optimized for its own speed range.

 

No, it gives the engine additional cam *lobes* for high engine speeds.
There are both SOHC and DOHC varieties of VTEC, and on the DOHC variety,
there's one shaft for the intake valves, and one for the exhaust valves,
like a normal DOHC engine. There are low-speed and high-speed lobes on
each camshaft.

 

No, it gives the engine additional cam *lobes* for high engine speeds.
There are both SOHC and DOHC varieties of VTEC, and on the DOHC variety,
there's one shaft for the intake valves, and one for the exhaust valves,
like a normal DOHC engine. There are low-speed and high-speed lobes on
each camshaft.

 

My view is that at certain times, the engine can take in more fuel and
air. More power, yes. Better fuel mileage, I don't think so. bob

 

My view is that at certain times, the engine can take in more fuel and
air. More power, yes. Better fuel mileage, I don't think so. bob

 

One could argue that the biggest benefit of V-TEC (compared with a
standard 3 or 4 valve / cylinder engine) is when it is NOT engaged. At
low RPM / light load (where you spend the most time) a single intake
valve is better than two. With V-TEC both ends of the range can be
optimized.

 

One could argue that the biggest benefit of V-TEC (compared with a
standard 3 or 4 valve / cylinder engine) is when it is NOT engaged. At
low RPM / light load (where you spend the most time) a single intake
valve is better than two. With V-TEC both ends of the range can be
optimized.

 

Excuse me.

You are correct.

 

Excuse me.

You are correct.

 

First of all (not for Mr Hunt) - it's VTEC. All caps - no dash.

Second - it's a pretty interesting configuration. For the DOHC
configuration, there are 6 lobes (3 intake and 3 exhaust) per
cylinder. The 3 intake lobes are divided into two small low
RPM lobes, and a single high RPM lobe between the two low RPM
lobes. At lower RPMs, each valve is actuated by its own rocker
arm riding off the two outer lobes. The high-RPM lobe is used
by locking a hydraulically-actuate flap (apparently called the
"follower" by some) that both, rides off the high RPM lobe, and
locks both rocker arms together so that the valves are operated
with the more aggressive cam. The VTEC lobe is a few mm wider
at the fully open end, but the same width at the fully closed end.

The following has a decent diagram:

<http://www.quickhonda.net/howVtecWorks.htm>

 

First of all (not for Mr Hunt) - it's VTEC. All caps - no dash.

Second - it's a pretty interesting configuration. For the DOHC
configuration, there are 6 lobes (3 intake and 3 exhaust) per
cylinder. The 3 intake lobes are divided into two small low
RPM lobes, and a single high RPM lobe between the two low RPM
lobes. At lower RPMs, each valve is actuated by its own rocker
arm riding off the two outer lobes. The high-RPM lobe is used
by locking a hydraulically-actuate flap (apparently called the
"follower" by some) that both, rides off the high RPM lobe, and
locks both rocker arms together so that the valves are operated
with the more aggressive cam. The VTEC lobe is a few mm wider
at the fully open end, but the same width at the fully closed end.

The following has a decent diagram:

<http://www.quickhonda.net/howVtecWorks.htm>

 

There are now so many variations on Honda's VTEC, it's getting difficult to
give a single characterization - everything from the economy-minded VTEC-E
to performance oriented and everything in between. Until the K-Series
engines, AFAIK the DOHCs did have variable lift on both inlet and exhaust
but now we have variations where, e.g. the RSX engine (K20A ?) has variable
lift on only the intake and the RSX-S(K20C or is it K20A2?) has it on both
cams.

Rgds, George Macdonald

"Just because they're paranoid doesn't mean you're not psychotic" - Who, me??

 

There are now so many variations on Honda's VTEC, it's getting difficult to
give a single characterization - everything from the economy-minded VTEC-E
to performance oriented and everything in between. Until the K-Series
engines, AFAIK the DOHCs did have variable lift on both inlet and exhaust
but now we have variations where, e.g. the RSX engine (K20A ?) has variable
lift on only the intake and the RSX-S(K20C or is it K20A2?) has it on both
cams.

Rgds, George Macdonald

"Just because they're paranoid doesn't mean you're not psychotic" - Who, me??

 

My 2003 civic Hybrid has VTEC for the "cylinder idling system". As far as
I know, it has nothing to do with performance. It just shuts down three
sets of valves during coasting.

 

My 2003 civic Hybrid has VTEC for the "cylinder idling system". As far as
I know, it has nothing to do with performance. It just shuts down three
sets of valves during coasting.