Does Vtec really kick in?

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Zenmervolt

Elite member
Oct 22, 2000
24,512
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D16A8

<snip>

Similar bore and stroke of B16A2, same displacement, even two overhead cams..but only 125 horsepower.

Similar cam grind? What do the heads flow?

And the rest of it's not even close. The B16A2 is oversquare (larger bore than stroke), the D16A8 is undersquare. The difference in stroke between the two engines is nearly a half-inch, huge in engine terms, which means that the mean piston velocity for a given RPM in the D16 will be higher, limiting redline much more than on the B16...

Really, it's not the VTEC that's helping the B16. The B16 is clearly designed for higher RPM operation and more power while the D16 is designed as a mid-level workhorse engine. There are a myriad of other engineering factors that are determining why the B16 produces more power.

ZV
 

reallyscrued

Platinum Member
Jul 28, 2004
2,618
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How about head design? Throttle Body sizes? Cam profiles? etc. Are you really going to give VTEC all the credit of that power difference?

I don't see why not... the DOHC VTEC is exactly what gives it a power boost after 5900 rpm on those dyno charts; with VTEC disabled, after 5900, the graph levels out. (Friend has done dyno runs with VTEC enabled/disabledin EM1). And please, exactly how much head tuning can a econobox company add to their 1.6 liter engines to raise it 40 horsepower? Throttle body size? There's no way a bigger TB will give it that much of an advtange. Bolt-on type upgrades are BS anyway in such small engines unless you're boosting.

If so, I guess other auto makers have no chance.

...What the hell are you talking about? I don't know how to reply to this.
 

speedy2

Golden Member
Nov 30, 2008
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It means, if VTEC is this godsend from Honda, other automakers have no chance of competing. Sarcasm as well.

Also, read ZV's post above yours.
 

Demon-Xanth

Lifer
Feb 15, 2000
20,551
2
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Head, cam, and intake can make a pair of engines that are otherwise very similar perform extremely different. Case in point, GM's LS2 is a 6 liter V8 that made 400HP, the LQ4 which is also a 6 liter V8, based on the same design made 300HP. These engines don't even differ as much as the D16 and B16 do.
 

reallyscrued

Platinum Member
Jul 28, 2004
2,618
5
81
Ok well maybe I'll eat my hat then... I guess I was very misinformed in the way VTEC aids engines. Thank you all for educating me.

VTAK, yo.
 

Zenmervolt

Elite member
Oct 22, 2000
24,512
21
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I don't see why not... the DOHC VTEC is exactly what gives it a power boost after 5900 rpm on those dyno charts; with VTEC disabled, after 5900, the graph levels out. (Friend has done dyno runs with VTEC enabled/disabledin EM1).

No shit Sherlock. Disabling VTEC keeps the low-RPM cams in play and never switches to the higher lift and longer duration cams. Dyno the car with the high-RPM cam profile in play the entire time and it will go right back to the higher numbers all without VTEC acting on anything.

All the VTEC does is swap cam profiles. The actual power is produced by the different cam profile. If you can't understand that the VTEC mechanism is independent of the cam grind, we really can't go any further.

And please, exactly how much head tuning can a econobox company add to their 1.6 liter engines to raise it 40 horsepower?

I covered this in my post. Head design plays a huge role because if you optimise the head for low- or mid-RPM, you give up a lot of potential power near redline. If the heads can't flow at 7,000 RPM, then it doesn't matter if the rest of the engine can reach that speed, you still won't make much power there.

ZV
 

DivideBYZero

Lifer
May 18, 2001
24,117
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Similar cam grind? What do the heads flow?

And the rest of it's not even close. The B16A2 is oversquare (larger bore than stroke), the D16A8 is undersquare. The difference in stroke between the two engines is nearly a half-inch, huge in engine terms, which means that the mean piston velocity for a given RPM in the D16 will be higher, limiting redline much more than on the B16...

Really, it's not the VTEC that's helping the B16. The B16 is clearly designed for higher RPM operation and more power while the D16 is designed as a mid-level workhorse engine. There are a myriad of other engineering factors that are determining why the B16 produces more power.

ZV

Hey, hang on a minute, I know you're having fun in your special snooty way, but you are barking up the wrong tree if you are saying that the new cam profiles do not have a major impact on the power produced by this engine when the VTEC system engages. Why it feels that way is of no consequence, i.e., everyone knows the main purpose is to give you a wild and mild mix so that it's not a pain to live with.

Of course there are other factors, but the VTEC system in these motors is the largest contributing factor between similar motors. The matter of 750 rpm alone is not enough to account for the 30-40hp increase in output.

Please consider posting in a manner that is more educational, rather than the haughty manner you do in most cases. People will respect you more for that.
 

speedy2

Golden Member
Nov 30, 2008
1,294
0
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And please, exactly how much head tuning can a econobox company add to their 1.6 liter engines to raise it 40 horsepower? Throttle body size? There's no way a bigger TB will give it that much of an advtange. Bolt-on type upgrades are BS anyway in such small engines unless you're boosting.

Forgot about this part.


But, you really think they are going to implement something like VTEC and try to make it flow through the same head and exhaust?

VTEC increases duration. Honda would be pretty retarded NOT to make the head flow better.
 

Zenmervolt

Elite member
Oct 22, 2000
24,512
21
81
Hey, hang on a minute, I know you're having fun in your special snooty way, but you are barking up the wrong tree if you are saying that the new cam profiles do not have a major impact on the power produced by this engine when the VTEC system engages. Why it feels that way is of no consequence, i.e., everyone knows the main purpose is to give you a wild and mild mix so that it's not a pain to live with.

Of course there are other factors, but the VTEC system in these motors is the largest contributing factor between similar motors. The matter of 750 rpm alone is not enough to account for the 30-40hp increase in output.

I've already stated that VTEC allows the cam profiles to shift and create a more livable low-RPM state. I didn't think I needed to repeat that in every post I made.

The difference in output is indeed largely due to cam profiles, I never denied that. I simply pointed out that VTEC, which is a mechanism for shifting the profiles is not directly related to which profiles are chosen. You could theoretically implement VTEC with two identical cam profiles and then see no benefit from it. VTEC would still be "kicking in", but it wouldn't matter.

The point here is that there's a need for the ability to abstract a little and realise that it's the cam profile, not VTEC that makes the difference. VTEC enables the use of a wild cam without the drawbacks down low, but it's doesn't add any actual peak power beyond what the aggressive cams would make without VTEC.

Please consider posting in a manner that is more educational, rather than the haughty manner you do in most cases. People will respect you more for that.

Please consider that I have the respect of those whose respect matters to me.

ZV
 

DivideBYZero

Lifer
May 18, 2001
24,117
2
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I've already stated that VTEC allows the cam profiles to shift and create a more livable low-RPM state. I didn't think I needed to repeat that in every post I made.

The difference in output is indeed largely due to cam profiles, I never denied that. I simply pointed out that VTEC, which is a mechanism for shifting the profiles is not directly related to which profiles are chosen. You could theoretically implement VTEC with two identical cam profiles and then see no benefit from it. VTEC would still be "kicking in", but it wouldn't matter.

The point here is that there's a need for the ability to abstract a little and realise that it's the cam profile, not VTEC that makes the difference. VTEC enables the use of a wild cam without the drawbacks down low, but it's doesn't add any actual peak power beyond what the aggressive cams would make without VTEC.


All you need to advise those who are not aware is that there are two or more cam profiles and how this effects power output. You did that in the last paragraph, it would have helped those whom you are arguing with needlessly to post that first.
Please consider that I have the respect of those whose respect matters to me.

ZV

Hmm, if you're setting up an 'old boys club' in The Garage maybe you should post up who's in and who's out, so we know if your going to be nice or rude. Treat all with an even hand or not at all. This is MHO.
 
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Zenmervolt

Elite member
Oct 22, 2000
24,512
21
81
All you need to advise those who are not aware is that there are two or more cam profiles and how this effects power output. You did that in the last paragraph, it would have helped those whom you are arguing with needlessly to post that first.

I also did it in my first post in this thread:

VTEC does not increase power per-se. VTEC allows two separate cam profiles.

If only the high-lift, high-duration cam were used without VTEC, the engine would still make 100 hp/liter. It would idle like crap and would be gutless at low RPM, but it would still scream just as much at high RPM as the VTEC engine and it would still make the same power at high RPM.

What VTEC does is allow the engine to run a tamer, low-RPM cam for more pleasant low-RPM operation and then switch to the more aggressive cam at high RPM. VTEC doesn't add power in and of itself, all VTEC does is swap cam profiles.

Hmm, if you're setting up an 'old boys club' in The Garage maybe you should post up who's in and who's out, so we know if your going to be nice or rude. Treat all with an even hand or not at all. This is MHO.

Here's an easy way to figure it out, if someone is clearly making an effort to read through the actual thread, I'm going to give them leeway.

If someone can't be bothered to read what I've already posted and makes borderline call out posts, I'm probably going to be a wee bit cranky.

ZV
 

Demon-Xanth

Lifer
Feb 15, 2000
20,551
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Who needs VTEC when you got a turbocharged I-6? :)
engine_truck.gif



...there's no replacement for displacement!
 

overst33r

Diamond Member
Oct 3, 2004
5,761
12
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Who needs VTEC when you got a turbocharged I-6? :)
engine_truck.gif



...there's no replacement for displacement!

Pretty sure that's a supercharger as well in that pic, feeding the turbo I think.

There's a replacement, more revs! :D
 
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exdeath

Lifer
Jan 29, 2004
13,679
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Pretty sure that's a supercharger as well in that pic, feeding the turbo I think.

There's a replacement, more revs! :D

Nope. Just build the bigger displacement engine out of unobtanium and it can rev high too and make even more.
 

overst33r

Diamond Member
Oct 3, 2004
5,761
12
81
Nope. Just build the bigger displacement engine out of unobtanium and it can rev high too and make even more.

Two ways to make power, you've said it yourself before...

-displacement
-RPM

Theoretically you can add more of either.

Practically, displacement is much cheaper.

Just kinda peevs me when people say that without giving credit to the other possibility.
 

punjabiplaya

Diamond Member
Nov 12, 2006
3,495
1
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Two ways to make power, you've said it yourself before...

-displacement
-RPM

Theoretically you can add more of either.

Practically, displacement is much cheaper.

Just kinda peevs me when people say that without giving credit to the other possibility.

or forced induction. or lower elevation. or meth. or racegas or blah blah blah
 

thomsbrain

Lifer
Dec 4, 2001
18,148
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And please, exactly how much head tuning can a econobox company add to their 1.6 liter engines to raise it 40 horsepower?

Granted it isn't a 1.6, but Honda extracted 40 more HP out of the 3.0 V6 between 6th and 7th gen Accords by doing little more than improving breathing.
 

TraumaRN

Diamond Member
Jun 5, 2005
6,893
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I'm just waiting for a, Ti-VCT just kicked in yo!, Thread. Especially since Ford is basically advertising it on everything from the Mustang to the Edge to the new Explorer.

But maybe not just it's not cool like VTEC
 

mwmorph

Diamond Member
Dec 27, 2004
8,877
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My pushrods just kicked in, yo!

OHV engines can make use of true, independent variable valve timing (though I don't think lift has been invented yet, and when it does, it'll really be a masterpiece of engineering, probably requiring a phaser and actuator along with finely honed, extremely strong cams that can slide lengthwise in an engine, similar to DSM crankwalk without the whole killing the motor thing)

http://www.sae.org/automag/technewsletter/070402Powertrain/04.htm

Dodge used it in the Viper and I fully expect GM to get a system like it sooner or later (Ford also has a system that would work, but it links advancement and retardation to each other in a less effective master/slave configuration) when the additional cost is required (along with Direct Injection) to make more power and lower fuel consumption.

Variable valve timing and lift does not increase power per se as previously mentioned, rather it maintains power while maintaining drivability and fuel consumption. Fuel mixing, intake, fuel and exhaust improvements (valve angles, intake and exhaust pressure, intake and exhaust resonance tuning, combustion chamber layout, spark plug placement, compression etc.) increase power at a given rpm, variable valve timing a used in engines today gives an engine different personalities, do not mix capability with function. A engine can run at 20+* advanced intake opening/; -20* exhaust retardation at low and high rpm, VVT just allows the engine to run at a different profile (anywhere from tpically 2-8* at lower rpms) so it is smoother and more efficient without a rough bouncing idle/low rpm operation, or inefficient lower fuel economy. You could always feel free to drop in a super aggressive cam in an engine tuned for 6000+ rpm duty(like a B18C previously mentioned), but it'll lose a lot of smoothness and driviability at lower rpms, which is why manufacturers don't tend to do it except in extreme cases, that would "gain" power, but in my view, it's really just unlocking what's already there and shifting the chokepoint to somewhere else, you already have that air and fuel available, just waiting there.

Then again, you can argue it's just semantics, I consider current uses of techs like VTEC to be "building down"power, taking an available power peak and tuning it out at lower rpms for streetability and NVH while say a turbocharger is "building up" since it takes what's already available and adding to what is physically impossible otherwise to the peak. There are always exceptions like the S2000's infinitely variable system building up a higher peak at low, mid and high, but in the vast majority of cases like the K20, it is used to improve EPA estimates and the like not related to power.
 
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DivideBYZero

Lifer
May 18, 2001
24,117
2
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Granted it isn't a 1.6, but Honda extracted 40 more HP out of the 3.0 V6 between 6th and 7th gen Accords by doing little more than improving breathing.

Seeing as all an engine does is breathe, you are correct. As in all power improvements are based upon how well an engine 'breathes'*.




*I'm just going to mention friction has an impact on power too, down here, before anyone posts it.