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-   -   Ohc 1.5 Vs Ohc Vtec (https://www.team-bhp.com/forum/technical-stuff/20132-ohc-1-5-vs-ohc-vtec.html)

i own a 2001 ohc 1.5.
on every forum, auto mags, i come across rave views on the OHC VTEC. but somehow the 1.5 is not discussed in the same vein. in paper there is a 6 bhp diff. ive NEVER driven a VTEC. can some one say what exactly is the practical diff betn the 1.5 AND THE VTEC in terms of

1) acceleration times - 0-60 and 0-100
2) ride, handling - if any bcos of the diff in the shoes they wear
3) any other diff in mechanicals ? - like springs, exhaust etc ?

im really depressed by the fact that the 1.5 is always the underdog when compared to the VTEC for just that 6 BHP shortfall :mad: ( even considering putting a VTEC logo on the bumper :confused:

As a Vtec owner and fan, the performance difference between a 1.5 and the Vtec is not that much.

But theres somethings in life that you just cant explain. And the Vtec just makes you feel more special.

VTECH Stands for "Variable valve Timing and lift Electronic Control", It's not just the logo on the bumper, It means a cutting edge technology powering your engines valves.
Here is the Anlology, You have a bucket of water, an empty bucket and small cup to transfer water from the filled one to the empty one.
To Increase the efficiency of water transfer you can use the following methods
1. Increase the size of the small cup thus by increasing the amount of water transferred.
2. You can move the cup faster between the buckets so that the work done is more.
Honda choose the later method, rotate the engine faster to produce more power, But there is a problem with this method at lower RPM's the engine guzzles up more fuel to produce the required costant power which is completely against HONDS's design, so they came up with VTECH.

If high speed operation is all we have to worry about, Honda wouldn't need to implement VTEC. Indeed, race engines that operate mostly at high rpms do not utilize any mechanism like VTEC. But street cars used for daily driving spend most of their time with the engine at low RPMs. Valves that open wide for high RPM operation contributes to rough operation and poor fuel economy at low RPMs. These undesirable traits are directly against Honda's design goals.
The solution that Honda came up with is the VTEC mechanism: open the valves nice and wide at high RPMs, but open them not as much at low RPMs. So now you have a engine with smooth operation at low RPMs, and high power output at high RPMs.
Hope you got the difference, in VTECH the camshaft is moved during operation as the RPM of the engine increases, this is done by using the oil presure inside the engine. So in VTECH the engine RPM desides how much the inlet and exhaust valves open.
Regards,
Mega
--Inspired By HONDA VTECH technology...

The difference is more power, more torque, higher redline etc. The performance difference is 1.5 - 0-100 in 11.5 or so seconds and VTEC in 10.01 seconds (I'm pretty sure but could be wrong considering I read the test 5-6 years back)

Power difference may not seem much but the character of the cars are very different. Ishan has mentioned why in above post

Superb explanation mega5918 !!! I loved it !!

does the 6bhp make such a big diff in 0-100 ?!! ( im depressed !)
are there any other differences ? like mechanicals, handling etc..VTEC owners - pls add in

It was always VTEC. Everyday I see new spelling! Ah!

does this make the VTEC more smooth and fuel effcient than the 1.5 ? IF SO how much is the diff in FE..

also is this the reason why the normal 1.5 is very jerky in city driving..( the lack of VTEC in an engine that typically makes most of its power higher up the rev range - i mean any shift below 2500 rpm and the gear change is def not smooth unless u play the clutch )

You gotta drive it to understand the diff.

Stock vs stock, the Vtec is much more superior than the 6bhp diff you see on papar.

What you're seeing is the power output at one particular rpm, performance doesn't depend solely on that, the torque and power curve is what gives the car it's acceleration.

Generally, to achieve performance with FE, manufacturers use a cam profile that gives you good performance with good FE. What Vtec does is, use a sedate cam profile at low revvs, which uses less air than what a normal engine would take in (improving FE) and activates an aggressive cam profile at higher revvs, which maximises the engines air intake (increasing torque and power).

If the Vtec system is deactivated, the performance would drop drastically as the engine would run with the sedate cam profile.

Shan2nu

I think the NHC iDSI model would be a good example of that.

There is little difference between the FE of the VTEC and iDSI models of the NHC, since most of the times the sedate cam profile gets used. But the wild cam profile of the VTEC gives it much better top-end power.

MEGA 5918, that was superb. You put that down in a simpler/easier way.

I really admire your post.

BUT... the 'H' was not needed.
:OT

The cam does not move, there is a different lobe for every stage.

BMW's valvetronic technology moves the cam.

Since most of the people have explained you mechanical difference between 1.5 Non Vtec & 1.5Vtec engines it actually doesnt ends there, Honda has two different Fuel/Ignitions Maps stored in ECU one for low speed CAM designed for fuel economy & one aggresive map for High speed CAm desgined for Power so when your Vtec Engages it reads from a different set of Ignition/Fuel Curve which is optimized for High Speed High duration Cam lobes. So you get best of both worlds fuel economy & power up at high RPM.