hey. i was in autos class and of course the smart *** autos teacher always makes fun of the imports. so then we had a conversation about hp and torque and he was saying that hp was just a way to advertise cars and a reading from torque and torque is the main thing which is the force of power. so i did some research on torque and some sites i was on were saying that torque is better when its max peak is on higher rpm's. so on the prelude, max torque is at 5300rpm and then the torque starts going lower and lower. so i was thinking that right at the torque peak at 5300, wouldnt you get the best performance gains if you made the vtec crosspoint right at 5300rpm right when torque reaches max peak so you get a good powerspread? i dunno i was just thinking about it

 

On an H22, VTEC does kick in around 5300. Anyway, there's no all around best place for peak torque. It all depends on what you're doing. If you're towing a big load, peak torque at around 2500 is good. Peak torque in the midrange is great for autocross. And the power band leading up to the peak is also very important

 

Saying a certain car has 500hp is telling you something about its performance. It will perform similarly to other cars that get 500hp in different ways (ie, have different amounts of torque)

Saying a car has 500tq, on the other hand, tells you little about its performace. Equipping it with another, different 500tq engine could yield much different results.

"force" and "power" are two different things.

VTEC engages in the 4900-5000rpm range stock.


Modified by A Blue Lude at 2:47 PM 9/9/2007

 

^^ well said

Horsepower is work over time, emphasis on the TIME, this is what is important. Shoot, you could stand on the end of a 2x4 and generate 500 lb/ft of torque, does this mean it's fast?

 

Take diesels for example, sure they can pull a lot of weight around but until you add the turbo they really don't go anywhere too quickly.

 

The best way to understand this is to look at what horsepower really signifies.

The force that moves your car is torque. The more torque, the better. Duh. Now, that torque is created every time a cylinder fires. The number you see on a dyno graph is the average torque being produced at a given time.

This is what torque output really looks like on a 4cyl. There are 4 peaks when the cylinders fire and a little dip right before, meaning negative torque, which is used to compress the mixture just before combustion.



So, the number you get on the dyno is the average torque output sampled at a given frequency.

But, in order to move the car faster, you want as many of those instantaneous torque pulses as you can get, right? So that would imply that the highest rpm you can rev to would produce the most acceleration.

This is where the kind of "torque" your teacher is talking about comes into play. (btw he seems like an ignorant ***) Making torque at high rpm is much more difficult than making torque at low rpm. Horsepower is simply a measure of an engine's ability to carry torque into the high rpm range. HP= Torque*rpm/5252. It is a direct function of the physical quality torque, and just to be clear, HP is simply a calculation, not a physical quantity at all.

An engine that makes 300lbs of torque in a powerband from 3-6000 rpm (has about 350hp max) will be much slower than one that makes 250lbs of torque from 5-8000rpm (would have about 380hp max).

Anyways, horsepower is usually a way better determinant of how fast a car is, torque is the meat in the sandwich though, so to speak.

 

Now for this vtec stuff you're talking about.

VTEC is there so you can utilize a cam lobe that is optimized for low end while you're in the low end, then switch to a different one for the top end. Honda has it set very well for the stock cams right out of the factory.

 

lol alright. thanks mgags. im a show my teacher that tomorow lol. and ya he is an *** but hes jus always tryin to give me a hard time for owning a honda lol

 

Your teacher's an idiot. /thread.

 

on the h22... i think honda put the vtec crossover a bit too high....
this is to get the vtec "kick" that the customer wants...

if you push it forward a bit you'll free up some horsepower... but you wont feel it kick in...

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by InvaderTrax &raquo;</TD></TR><TR><TD CLASS="quote">On an H22, VTEC does kick in around 5300. Anyway, there's no all around best place for peak torque. It all depends on what you're doing. If you're towing a big load, peak torque at around 2500 is good. Peak torque in the midrange is great for autocross. And the power band leading up to the peak is also very important</TD></TR></TABLE>

The VTEC crossover on a stock 5th gen (USDM) is actually between 5500-5600.
The JDM H22A's crossover is at 5200

 

USDM is 5200, you think its 5500 because the stock tach is off.

i dont know about the JDM p13

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 98vtec &raquo;</TD></TR><TR><TD CLASS="quote">USDM is 5200, you think its 5500 because the stock tach is off.

i dont know about the JDM p13</TD></TR></TABLE>

yeah I found out when I set it to 5500(which I THOUGH was stock) in hondata and it come on at like 6K got a nice big kick though.

oh my USDM my vtec window is set at 4700-4900rpms I get a kick if I floor it from holding back, but not if I am going down the track(WOT all the time)

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 98vtec &raquo;</TD></TR><TR><TD CLASS="quote">USDM is 5200, you think its 5500 because the stock tach is off.

i dont know about the JDM p13</TD></TR></TABLE>

lmao ya i always thought it was 5200 because on the aftermarket it said 5200 but i thought it was just my imagination and the aftermarket one was off. thats good to know though

 

Torque is what engines do...they twist, but HP is the RATE that torque is applied.

Having torque happen later on (higher rpm) is never a good thing BUT it allows for a faster rate of torque being applied (HP) as the engine is spinning faster AND allows for shorter gearing to gain mechanical advantage.


As they always say, Torque sells cars, HP moves cars. This will never change

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by TraKtioN &raquo;</TD></TR><TR><TD CLASS="quote">Having torque happen later on (higher rpm) is never a good thing ?</TD></TR></TABLE>

wtf dude? Ever heard of formula1? Yes a low end lack of torque on a street car sucks, but top end torque is the name of the game. It is like the best of both worlds.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by TraKtioN &raquo;</TD></TR><TR><TD CLASS="quote">As they always say, Torque sells cars, HP moves cars. This will never change </TD></TR></TABLE>

Though I agree, I have to point out to you that your saying is backwards. The ignorant public wants a horsepower number. The billy-bobs around here (NC) want a torque number for their pickup and a hp number for their camaro LOL

 

i just had a new exhaust and new springs put into my '01 h22, and now vtec feels like its engaging 300-500 rpms higher than it did before. can anyone help me out with this?

 

an exhaust wont change your vtec engagement.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by mgags7 &raquo;</TD></TR><TR><TD CLASS="quote">
Though I agree, I have to point out to you that your saying is backwards. The ignorant public wants a horsepower number. The billy-bobs around here (NC) want a torque number for their pickup and a hp number for their camaro LOL</TD></TR></TABLE>

exact reason i LOVE seing turbo B series dyno graphs......like 300 HP with only 200 lbs of TQ


<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by mgags7 &raquo;</TD></TR><TR><TD CLASS="quote">
This is what torque output really looks like on a 4cyl. There are 4 peaks when the cylinders fire and a little dip right before, meaning negative torque, which is used to compress the mixture just before combustion.



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

wouldnt that be 2 peaks because 1-4 fire together and 2-3 fire together?


p.s. just food for fact if no one caught it earlier......on a dyno HP and TQ will always meet at 5252rpm

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 95greenlude &raquo;</TD></TR><TR><TD CLASS="quote">

p.s. just food for fact if no one caught it earlier......on a dyno HP and TQ will always meet at 5252rpm</TD></TR></TABLE>

depending on the view....yes

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 95greenlude &raquo;</TD></TR><TR><TD CLASS="quote">wouldnt that be 2 peaks because 1-4 fire together and 2-3 fire together?</TD></TR></TABLE>

They don't fire together do they...? One is on the Intake Stroke while the other is one the Exhaust Stroke.. One Cylinder is bringing Fuel/Air in and Compressing and then Combustion while the other Cylinder is letting the Combusted Air out after Combustion..

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by MLBZ521 &raquo;</TD></TR><TR><TD CLASS="quote">

They don't fire together do they...? One is on the Intake Stroke while the other is one the Exhaust Stroke.. One Cylinder is bringing Fuel/Air in and Compressing and then Combustion while the other Cylinder is letting the Combusted Air out after Combustion..</TD></TR></TABLE>

err....yea i got confused

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by TraKtioN &raquo;</TD></TR><TR><TD CLASS="quote">Torque is what engines do...they twist, but HP is the RATE that torque is applied.

Having torque happen later on (higher rpm) is never a good thing BUT it allows for a faster rate of torque being applied (HP) as the engine is spinning faster AND allows for shorter gearing to gain mechanical advantage.


As they always say, Torque sells cars, HP moves cars. This will never change </TD></TR></TABLE>

i think thats the exact opposite lol. i thought it was HP sells cars but torque wins races.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 95greenlude &raquo;</TD></TR><TR><TD CLASS="quote">
wouldnt that be 2 peaks because 1-4 fire together and 2-3 fire together?</TD></TR></TABLE>

Nah Jared, that is only 360 degrees of crank rotation. It takes 720 to fire all 4 cylinders. Firing order is 1-3-4-2 all separated by 180 degrees of rotation (BDC to TDC).

The reason hp and torque always meet at 5252 is because hp is calculated from torque. It is not measured by the dyno, it is simply a formula, hp=tq*rpm/5252.

 

Skimming this thread I'll add a few pieces of information.

Power is the rate at which the engine does work(makes torque); they are related by the following formula stolen from wiki:


The 1-4/2-3 cylinders do not fire at the same time, they fire 360 crank angle degrees from each other. One fires right before the other transitions from the exhaust to intake cycle.

When comparing engines the area under the torque/power curve is generally more important than the peak/peak location. The greater the area, the greater the average available power/torque.

The VTEC mechanism allows the use of a higher lift/duration cam lobe that would perform poorly at low engine speeds usually caused by greater valve overlaps and throttling losses.