This is a debate between my friend at work.

He says that two identical motors with the same displacement, stroke, and head with the same flow pattern, but only difference is one has some form of variable valve time (aka vtec) and the other doesn't will make the same peak power. He said this will take place under any circumstance, all motor, turbo, or supercharged/procharged.

I disagree... please give your opinion and state valid proof or reasoning for your choice.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by kirby &raquo;</TD></TR><TR><TD CLASS="quote">This is a debate between my friend at work.

He says that two identical motors with the same displacement, stroke, and head with the same flow pattern, but only difference is one has some form of variable valve time (aka vtec) and the other doesn't will make the same peak power. He said this will take place under any circumstance, all motor, turbo, or supercharged/procharged.

I disagree... please give your opinion and state valid proof or reasoning for your choice.</TD></TR></TABLE>

Im with you, I disagree! The nonvtec will make power before the vtec engine would, but they should top off about the same peak wise!

 

actually that means you are agreeing with him.

 

I'll agree with him.

Same engine, same head, but one is locked in VTEC all the time would yeild the same peak HP IMHO.

The dyno charts would be completely different, but I think the peak number will be the same.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by kirby &raquo;</TD></TR><TR><TD CLASS="quote">actually that means you are agreeing with him. </TD></TR></TABLE>

Yes I am agreeing with him by disagreeing with his buddy. I guess I worded it wrong!

 

Well if took a b16 and disabled vtec and another b16 with vtec working of course the second would make more power. But if you took the same engines and only allowed one to stay in vtec all the time and the other had all lobes in play then they would peak the same, so it depends. I will say though regardless of peak performance the variable valve timing engine will have a infinitely better powerband, as if you couldn't infer that yourself.


Modified by rjay8604 at 10:57 PM 2/17/2005

 

I don't see how you could get a 12.8mm lift camshaft to idle. The purpose of vtec is to be able to have a high lift camshaft, and to engage at a certain rpm while the car is already moving. Tell me how you're gonna get a, for example, a BC4 to idle on the vtec lobe.........is this seriously a thread?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by clean rice &raquo;</TD></TR><TR><TD CLASS="quote">I don't see how you could get a 12.8mm lift camshaft to idle. The purpose of vtec is to be able to have a high lift camshaft, and to engage at a certain rpm while the car is already moving. Tell me how you're gonna get a, for example, a BC4 to idle on the vtec lobe.........is this seriously a thread? </TD></TR></TABLE>

It's a perfectly legitimate thread, and your question depends on your definition of "idle". Toda's "VTEC killer" cams have 12.0 mm of lift on the intake side, and although they're recommend for racing use only, they'll still allow the motor to "idle" with the proper setup/tuning.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by clean rice &raquo;</TD></TR><TR><TD CLASS="quote">I don't see how you could get a 12.8mm lift camshaft to idle. </TD></TR></TABLE>

lol, you my friend have never seen a built american V8, half an inch of lift isn't that uncommon.

I agree with the buddy, vtec doesn't allow you to make more power than older non vtec technology, it just allows you to have that same power with a more gas/emmisions friendly low rev range.

 

Yes I have seen a v8 run with that, but we my friend have half the cylinders, just an all around smaller motor. You can't compare the two. I do know about the vtec killers, whats the duration on them?

 

Toda VTEC Killer Camshafts

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by clean rice &raquo;</TD></TR><TR><TD CLASS="quote">Yes I have seen a v8 run with that, </TD></TR></TABLE>

Either way, you're wrong and idle has absolutely nothing to do with the original question.

 

Ever seen Crower 405a's for the LS/B20? They have .502" lift!

 

This is only my opinion, but I have seen evidence to suggest
this behavior is true:

if you had a B16 motor one with stock cams
and another B16 motor exactly the same with VTEC killer
lobes exactly like stock b16 Mid lobes...

motor #1 IMHO would not only accelerate across the band faster
but would make a bit more power on the big end. I think a correctly
sized primary lobe helps a motor transition to high cam under load
and will effect the amount of power a VTEC engine makes. Not to say that
this behavior couldnt be reduced/minimized with directed tuning. Im guessing
that the motor with VTEC would make 3-5pkwhp more, accelerating from 3K rpm. Just my guess.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by "StyleTEG" &raquo;</TD></TR><TR><TD CLASS="quote">B18B 404's, 3" SRI, DC 4-2-1, 2.25" exhaust - tuned with e-manage



165whp / 134lbs-ft torque

(dyno is compaired to an ITR with simmilar modifications / cam profile)

9.6:1 B20, Stock cams, 3" SRI, DC 4-2-1, 2.25" exhaust - tuned with e-manage



155whp / 130lbs-ft torque

(dyno is compaired to my previous B18B 404 setup)</TD></TR></TABLE>

Here is a comparison of an LS and ITR with similiar cam profiles, but the ITR has more compression and the LS has 2mm more stroke.

ITR CR: 10.8:1 to 11.0:1
B18a(in the graph) CR: 9.8:1


I know this isnt a perfect comparison but it gives you an idea!

 

yes, non vtec can make the power. I certainly will not say that, sometimes
VTEC can get in the way. however, I maintain that if all things were left
the same, both motors same, stock, having the same baseline within 1-2%
margin of error, I believe the low cam-high cam transition would allow the
VTEC motor to experience slightly more efficiency on the top end having
the low end response increased, transitioning under load into the big cam.

the big cam in itself would have a hard time generating the momentum necessary
to accelerate itself to its limit from low rpm. if the same profile was in the motor
and was tuned, a stock motor should idle on say B16 VTEC LOBES if timing was advanced in the map, etc. even still, tuned and what have you I would argue
that it would still have a boggyness on a stock motor and have to work harder
to get to redline.

hope this doesnt muddy the waters too much. if anyone wanted to try this on a dyno, you can turn your VTEC on at idle supplying 12v from the battery to the
grey wire on the VTEC pressure switch. give it a whirl!

personally, I think alot of tuners neglect low cam tuning on the VTEC cam. I remember one of them saying that he sets a high VTEC point so that he can test the low cam to 6K and make the most power with tuning down low first. Then goes back, sets VTEC at 5500 ish or when the power starts falling off and then tunes the high cam, and then gears, etc, microtuning from there. must be some truth to making power right from the word GO imho. agree or disagree, a car that accelerates hard outta the gate that has good response is way more fun to drive, VTEC or not.

mike

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by MikeSarr_GSR &raquo;</TD></TR><TR><TD CLASS="quote">yes, non vtec can make the power. I certainly will not say that, sometimes
VTEC can get in the way. however, I maintain that if all things were left
the same, both motors same, stock, having the same baseline within 1-2%
margin of error, I believe the low cam-high cam transition would allow the
VTEC motor to experience slightly more efficiency on the top end having
the low end response increased, transitioning under load into the big cam.

the big cam in itself would have a hard time generating the momentum necessary
to accelerate itself to its limit from low rpm. if the same profile was in the motor
and was tuned, a stock motor should idle on say B16 VTEC LOBES if timing was advanced in the map, etc. even still, tuned and what have you I would argue
that it would still have a boggyness on a stock motor and have to work harder
to get to redline.

hope this doesnt muddy the waters too much. if anyone wanted to try this on a dyno, you can turn your VTEC on at idle supplying 12v from the battery to the
grey wire on the VTEC pressure switch. give it a whirl!

mike </TD></TR></TABLE>

Im not disagreeing with you there, b/c that is the belief that we have all come to know of from word of mouth since the beginning of time!

In some aspects I could find that fact and in some a myth! Vtec is awesome for when you are going to run a cam that is so BIG that it will affect lowend so you have to have 2 different profiles, but at the same time I am running a big cam, crower 404 in my LS and I have a gain through out the entire powerband! Same goes for the Toda Vtec Killers. Also Crower makes another cam for the LS, the crower 405 that has a .502" lift and a 280/274 duration @ .050". Thats a big cam!

I guess it all depends on the build of the engine! The parts in your setup have to coincide with the rest or you may end up with poor performance. So in that, Im sure you could take a B16 for example and build a special cam for it that would allow it to run exactly the same without Vtec.

 

my response to you is simply this, yes you run a big cam. I say, you will have a few more ponies up top if you didnt have to have that big profile do all that work down low to move air. yes, you would have to match your parts to make use of this larger cam at an earlier rpm which it seems like you have the time honored debate is the purpose of VTEC in the first place. it is to simply add drivablility to a large camshaft, period. my point comes in simply from momentum.
all things the same the motor that revs up quicker will carry on the top end better and make a bit more power, VTEC or not

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by MikeSarr_GSR &raquo;</TD></TR><TR><TD CLASS="quote">my response to you is simply this, yes you run a big cam. I say, you will have a few more ponies up top if you didnt have to have that big profile do all that work down low to move air. yes, you would have to match your parts to make use of this larger cam at an earlier rpm which it seems like you have the time honored debate is the purpose of VTEC in the first place. it is to simply add drivablility to a large camshaft, period. my point comes in simply from momentum.
all things the same the motor that revs up quicker will carry on the top end better and make a bit more power, VTEC or not </TD></TR></TABLE>



Cant argue there! With Vtec drivability is a hell of a lot of better and is much easier on gas. You get the best of both worlds: a daily driver and a race car!

 

I think one of the big reasons for the vtec killers is the non-vtec valvetrain is smaller, rockers and such which allows for greater RPM.

 

I think the rocker arms are bigger in the nonvtecs. B18a/b and B20b/z have a rocker ratio of 1.75, compared to a B16's 1.45

I honestly think that the vtec valvetrain is setup better since the rockers are locked in place

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by kirby &raquo;</TD></TR><TR><TD CLASS="quote">This is a debate between my friend at work.

He says that two identical motors with the same displacement, stroke, and head with the same flow pattern, but only difference is one has some form of variable valve time (aka vtec) and the other doesn't will make the same peak power. He said this will take place under any circumstance, all motor, turbo, or supercharged/procharged.

I disagree... please give your opinion and state valid proof or reasoning for your choice.</TD></TR></TABLE>

I have to agree with your friend. VTEC really offers nothing more than two different cam profiles. And you can use the 'high' cam profile that makes maximum power on the VTEC motor to make the exact same amount of power on the non-VTEC motor. Rather what VTEC offers over non-VTEC is more consistent power output throughout the rev range. After all, that lobe that makes good peak power won't make good power in the lower revs.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by StorminMatt &raquo;</TD></TR><TR><TD CLASS="quote">

I have to agree with your friend. VTEC really offers nothing more than two different cam profiles. And you can use the 'high' cam profile that makes maximum power on the VTEC motor to make the exact same amount of power on the non-VTEC motor. Rather what VTEC offers over non-VTEC is more consistent power output throughout the rev range. After all, that lobe that makes good peak power won't make good power in the lower revs.</TD></TR></TABLE>

Not always true as covered earlier. And there are many things that can affect the vtec to it becomes inconsistent(oil pressure, bad ECU signal, dirt in the system, faulty sensors). Even at optimal performance, how is vtec more consistent?

The big cam small cam thing has alredy been covered. Nonvtecs can run big cams with no loss in the low end, except for the lopey idle(0-1000 rpm). However Vtec does take preference when you run a cam with a long enough duration that there is no way it could idle. Now here is Vtec is helpful b/c you can run a smaller profile so it may idle, and then switch over to the longer duration. But someone running a cam that big is unlikely, b/c cams like this can not just be dropped in; they require modification to the head to make them work.

 

the same motor with the same cams, just one with vtec engaged all the time and the other set up normally, would theoretically make the same peak horsepower... as long as each motor was tuned to make the best peak horsepower.

on the other hand, while tuning my motor changing the position of vtec does effect peak power... so i would say no they wouldn't make the same power.

So i guess i really didn't say anything that would help but... but over all, i would guess if both motors had the same lobe profile and were both tuned separately for peak power only they would make the same power... not looking at any mid range or torque numbers.

however this wouldn't make a good motor for driving... it would be hard to make idle and their would be no mid range making it a horrible motor for anything besides drag racing where your staying only in high rpms... like VTEC killer cams

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 92WhiteEG &raquo;</TD></TR><TR><TD CLASS="quote">the same motor with the same cams, just one with vtec engaged all the time and the other set up normally, would theoretically make the same peak horsepower... as long as each motor was tuned to make the best peak horsepower.

</TD></TR></TABLE>

Yes I agree


<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 92WhiteEG &raquo;</TD></TR><TR><TD CLASS="quote">

on the other hand, while tuning my motor changing the position of vtec does effect peak power... so i would say no they wouldn't make the same power.

</TD></TR></TABLE>

I havent seen this(I think)before, but changing the Vtec point just helps pull out the dip in the powerband at vtec cross-over. So I say peak numbers wont change, b/c you are changing anything with the cams and fuel. However degreeing cams will increase peak numbers and will change peak power rpm to either later or sooner. For example, your peak power is at 8600rpms; changing the cam gears now your peak may be higher hp wise but you may make peak power at 8500 rpms or 8700 rpms.


<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 92WhiteEG &raquo;</TD></TR><TR><TD CLASS="quote">

So i guess i really didn't say anything that would help but... but over all, i would guess if both motors had the same lobe profile and were both tuned separately for peak power only they would make the same power... not looking at any mid range or torque numbers.

</TD></TR></TABLE>

Very true. The powerbands would be very different due to motor configuration; which would give you different torque and midrange numbers.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 92WhiteEG &raquo;</TD></TR><TR><TD CLASS="quote">
however this wouldn't make a good motor for driving... it would be hard to make idle and their would be no mid range making it a horrible motor for anything besides drag racing where your staying only in high rpms... like VTEC killer cams
</TD></TR></TABLE>

The motor would be harder to drive and make idle but would not or should not sacrifice low end and midrange if the engine is designed right. You cant just go and put big cams in any motor, whether its vtec or nonvtec. You must build the motor where the parts used compliment each other and help out. Raiding compression would be a must, but higher than what the cam needs would not help. Run bolts that compliment the flow that the engine can produce with these cams and pistons, b/c to big of bolt ons is going to cause a loss in low end b/c of volumetric efficiency.

This is where I think you will have low end and mid range loss: the bolt ons!