Go Back   Team-BHP > Under the Hood > Technical Stuff


Reply
 
Thread Tools Search this Thread
Old 3rd January 2007, 13:11   #1
Senior - BHPian
 
narayan's Avatar
 
Join Date: Aug 2006
Location: Singapore
Posts: 2,770
Thanked: 1,163 Times
Question Ohc 1.5 Vs Ohc Vtec

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 ( even considering putting a VTEC logo on the bumper
narayan is online now   Reply With Quote
Old 3rd January 2007, 14:54   #2
GTO
Team-BHP Support
 
GTO's Avatar
 
Join Date: Feb 2004
Location: Bombay
Posts: 47,716
Thanked: 89,180 Times
Default

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.
GTO is offline   Reply With Quote
Old 3rd January 2007, 14:55   #3
BHPian
 
Join Date: Dec 2006
Location: Bangalore
Posts: 95
Thanked: 4 Times
Default

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...
mega5918 is offline   (3) Thanks Reply With Quote
Old 3rd January 2007, 15:11   #4
Senior - BHPian
 
iraghava's Avatar
 
Join Date: Oct 2005
Location: Bhaiyyaland
Posts: 8,028
Thanked: 153 Times
Default

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)
iraghava is offline   Reply With Quote
Old 3rd January 2007, 15:40   #5
Team-BHP Support
 
Join Date: Feb 2004
Location: Bangalore
Posts: 11,888
Thanked: 9,715 Times
Default

Power difference may not seem much but the character of the cars are very different. Ishan has mentioned why in above post
ajmat is offline   Reply With Quote
Old 3rd January 2007, 15:47   #6
Distinguished - BHPian
 
Nikhilb2008's Avatar
 
Join Date: Jul 2006
Location: Bangalore
Posts: 4,825
Thanked: 4,799 Times
Default

Superb explanation mega5918 !!! I loved it !!
Nikhilb2008 is offline   Reply With Quote
Old 3rd January 2007, 16:51   #7
Senior - BHPian
 
narayan's Avatar
 
Join Date: Aug 2006
Location: Singapore
Posts: 2,770
Thanked: 1,163 Times
Default

Quote:
Originally Posted by iraghava View Post
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)

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
narayan is online now   Reply With Quote
Old 3rd January 2007, 16:59   #8
BHPian
 
Pankaj401's Avatar
 
Join Date: Mar 2006
Location: Bangalore, India
Posts: 216
Thanked: 4 Times
Default

Quote:
VTECH Stands for ...
Quote:
--Inspired By HONDA VTECH technology...
It was always VTEC. Everyday I see new spelling! Ah!
Pankaj401 is offline   Reply With Quote
Old 3rd January 2007, 17:12   #9
Senior - BHPian
 
narayan's Avatar
 
Join Date: Aug 2006
Location: Singapore
Posts: 2,770
Thanked: 1,163 Times
Default

Quote:
Originally Posted by mega5918 View Post
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...
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 )
narayan is online now   Reply With Quote
Old 3rd January 2007, 18:06   #10
Senior - BHPian
 
Shan2nu's Avatar
 
Join Date: Feb 2004
Location: Hubli - Karnata
Posts: 5,525
Thanked: 87 Times
Default

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

Last edited by Shan2nu : 3rd January 2007 at 18:18.
Shan2nu is offline   Reply With Quote
Old 3rd January 2007, 18:24   #11
BHPian
 
goldie_malhotra's Avatar
 
Join Date: Nov 2005
Location: New Delhi
Posts: 757
Thanked: 10 Times
Default

Quote:
Originally Posted by Shan2nu View Post
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.
goldie_malhotra is offline   Reply With Quote
Old 3rd January 2007, 18:39   #12
Senior - BHPian
 
Surprise's Avatar
 
Join Date: Feb 2005
Location: Chennai
Posts: 2,299
Thanked: 129 Times
Default

MEGA 5918, that was superb. You put that down in a simpler/easier way.
Surprise is offline   Reply With Quote
Old 3rd January 2007, 19:41   #13
Senior - BHPian
 
DCEite's Avatar
 
Join Date: Sep 2004
Location: NCR
Posts: 3,044
Thanked: 475 Times
Default

Quote:
Originally Posted by mega5918 View Post
VTECH Stands for "Variable valve Timing and lift Electronic Control"
I really admire your post.

BUT... the 'H' was not needed.
DCEite is offline   Reply With Quote
Old 3rd January 2007, 20:17   #14
Distinguished - BHPian
 
Mpower's Avatar
 
Join Date: Mar 2005
Location: Bangalore
Posts: 10,432
Thanked: 1,682 Times
Default

Quote:
Originally Posted by mega5918 View Post
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...
The cam does not move, there is a different lobe for every stage.

BMW's valvetronic technology moves the cam.
Mpower is offline   Reply With Quote
Old 3rd January 2007, 21:42   #15
BHPian
 
Ford Rocam's Avatar
 
Join Date: Feb 2005
Location: Mumbai-India
Posts: 880
Thanked: 16 Times
Default

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.
Ford Rocam is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Wanted: OHC VTEC or OHC 1.5 adit1329 Shifting gears 5 22nd June 2012 17:00
Why is the OHC Vtec exhaust muffler different? jigarmuni Technical Stuff 28 28th May 2009 18:17
NHC-Vtec or OHC Vtec..which is a better buy? sunith Sedans 4 2nd May 2006 21:25
Indian vtec 106 bhp  Thai Vtec 120 bhp ajmat The Indian Car Scene 7 7th March 2006 18:21
OHC 1.5L VTEC for 'Urgent' sale Xsailor Shifting gears 14 28th July 2005 18:41


All times are GMT +5.5. The time now is 12:09.

Copyright 2000 - 2017, Team-BHP.com
Proudly powered by E2E Networks