Performance Difference in old vtec and new vtec?

[Green Hornet]

Just wondering why there seems to be a lack of "grunt" in the new vtec engines compared to the last incarnation. I have a 1.8 i-vtec civic and I bought it at the beginning of the year. I'm happy with the performance and the car.

However, I traded a 1.8 vtec Accord (2002 model) for my current car and I just dont notice the same "bite" around 4000 revs with the newer car. On the other hand the Accord did seem more diesel-ish in the lower rev range.

Am I mad or have Honda changed something to "smooth" the performance overall?

We hear people talk on tv about the vtec boost around 4000 revs but I dont see it in the newer engine.

[cylon2007]

You'll probably find that the older engine is actually less powerful and this makes the power step more noticable. As engines evlove they tend to get stronger both in power and torque and this is probably why there is a difference.

[skam]

Consider also the emissions matter and the enviromental friendly character of the civic engine. This may be the answer to your question. Don't forget that the newer engine is more powerful and more economical as well.

[pjr]

To grossly simplify how I believe the 'old' and 'new' Vtec systems differ....

There are two different cam profiles switched over when the conditions are right - perhaps one for economy and one for power.

The older vtec systems ran mostly in the economy profile until you revved them when the vtec switched over to the power profile - giving you the step in performance.

The new vtec, in the 1.8, would alway run in the power profile, until the right conditions are reached - narrow throttle opening, light load, lowish revs, when the vtec switches to the economy profile to give better fuel economy.

This is perhaps why you don't get the kick when reaching a certain rpm, because if you are using a heavy throttle application all the way from low revs up to the redline you will always be in the power vtec profile, and don't get the switchover?

I'm more certain of how the current vtec works, after reading the article linked to in the wiki. Useful links - Civinfo Wiki

As I said at the start, this is a very much simplified example.

Having said that, the 1.8 can still fly if you rev it!!

[Nick7]

As pjr said - VTEC on 1.8 is similar to VTEC-E in older 1.5 engines.
It is meant only to safe fuel, not as 'power mode'.
If applying full throttle, you will be in 'power' mode all way from 1000 - 7000rpm.
Although this 'power mode' should be called 'normal mode', and other mode is just 'saving fuel' mode.

Many people thing that if it's a VTEC, it should open up at higher rpm's for more power, but in case of our 1.8 engine, this is false.

[Green Hornet]

Originally Posted by Nick7

As pjr said - VTEC on 1.8 is similar to VTEC-E in older 1.5 engines.
It is meant only to safe fuel, not as 'power mode'.
If applying full throttle, you will be in 'power' mode all way from 1000 - 7000rpm.
Although this 'power mode' should be called 'normal mode', and other mode is just 'saving fuel' mode.

Many people thing that if it's a VTEC, it should open up at higher rpm's for more power, but in case of our 1.8 engine, this is false.

Oh, I get it. Basically, whereas the older engine was in fuel save mode until hitting a certain revs, the newer engines are in power mode all the time unless you lay off the power?

That makes sense from a driving point of view too. At lower revs (say taking off from traffic lights etc) the older engine felt a bit diesel-ish and only seemed more powerful in the higher range. The newer engine is much perkier in the lower revs and obviously stays that way unless laying off the throttle.

Am I understanding it right? Thanks for the info!

[pjr]

Originally Posted by Green Hornet

Oh, I get it. Basically, whereas the older engine was in fuel save mode until hitting a certain revs, the newer engines are in power mode all the time unless you lay off the power?

That makes sense from a driving point of view too. At lower revs (say taking off from traffic lights etc) the older engine felt a bit diesel-ish and only seemed more powerful in the higher range. The newer engine is much perkier in the lower revs and obviously stays that way unless laying off the throttle.

Am I understanding it right? Thanks for the info!

Yep, that's pretty much it. I remember reading early promotional articles from Honda, about how the 1.8 i-Vtec engine, gave the power of a 2.0 with the economy of a 1.6, and being a bit sceptical.

However, having come from a 2.0 Mazda 3 (with 2.0 fuel economy ), the Civic has the same, if not better performance and far better fuel economy, so I do believe the hype now. Sure it needs revs to deliver its best, but when the engine is as free-revving as it is, then there is no hardship.

I also recall reading about how with the older Vtec engines, and the stereotypically older age profile of Honda owners, that some people would never feel the benefit of the Vtec system because they wouldn't be revving their car hard enough to get into the Vtec (power) zone.

[pcr]

My understanding of it is that the engine will be in Economy mode if :-
The revs are between 1000rpm and 3500rpm AND the throttle is less than half open.
It is in Normal mode at all other times.
So for me, once above 1000rpm, it will always be in Economy mode, since the trottle is rarely depressed past half way, and gear change is around 3000rpm.

[pjr]

Originally Posted by pcr

My understanding of it is that the engine will be in Economy mode if :-
The revs are between 1000rpm and 3500rpm AND the throttle is less than half open.
It is in Normal mode at all other times.
So for me, once above 1000rpm, it will always be in Economy mode, since the trottle is rarely depressed past half way, and gear change is around 3000rpm.

You do also need to consider the load you are putting on the engine though. Going uphill or accelerating (unless very very gently), could be enough to switch the vtec out of economy into normal.

The economy vtec mode is designed to work best at constant speed cruising, under light load.

If you watch the instantaneous fuel economy on the trip computer (the bar graph one), at a steady 70mph on the flat the bar will hover around the 50mpg mark. Go downhill, and it can be anywhere between 75 & 100 mpg. Start to climb a hill and it will drop to 25/30. So, on the flat or downhill, at a constant speed, I would imagine the engine is in economy mode, going uphill, possibly not.

[Nick7]

It's in economy mode when throttle is slight depressed.
While in conventional engine there would be more vacuum (less pressure), in VTEC 'economy mode' on 1.8 there is more pressure which ensures less pumping losses.
This is achieved that intake valves are much longer open, so part of air mixture is pushed again back into intake manifold. This applies to 'economy mode'.

[charlas]

Don't have to worry about 'economy mode' on the Type-R... It's in 'using juice' mode, or 'really using juice and having stoopid fun' mode