I was doing a little reading on VTEC and how it works and came across this paragraph that explains why most of you guys have trouble getting off the line quickly in races.

"There is some significance to the shape of the crank torque curve, however. When drag racing a car, it is desired to have a bit of initial wheel spin, and then have the tire hook up with the ground. A torque curve with a peak early in the RPM range and then tapers off as RPMs rise is well suited to this purpose. This is why big displacement American muscle cars are so good at drag racing. VTEC engines, on the other hand, have very smooth gradually rising torque curves. The initial wheel spin, therefore, is harder to achive[sic]. And after the initial wheel spin gets going, the level torque curve means that very precise clutch and gas pedal control is needed to allow the drive wheels to regain traction while maintaining maximum acceleration. This is why VTEC engines are more difficult to launch off the line than large displacement muscle car engines."

If you want to read the rest of the article, go here: http://www.leecao.com/honda/vtec/commonmiss.html

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2001 SAAB 9-3SE HOT

The UNBIASED voice of reason

 

Bravo

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Nick
01' Cl-S Silver/ Black W/ Navi and Spoiler
V-1 Radar Hard Wired, Limo Tint all around
Comptech Headers, Sways, Springs, and AEM CAI
I've got one of the CLS's from the fast batch.
Lead Foot!

 

Good info

Patrick

 

i am enlightened.

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Acura 3.2CL Type-S w/ Navigation
Black/Ebony

- Pirelli P7000 Supersport 235/40ZR17
- Custom CAI
- Cleared Headlights
- Tint all around
- Mesh Grill
- Dual 12'' Alpine Type-S Subs
- Kenwood KAC-728S Amp

 

yeah, but most importantly make sure the cops arent around......almost raced an IS300....until I saw the cop around the corner.....close call!!!!

I have found rolling starts work OK with my stockers

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'01 silver/black
NAVI
eibach springs
35% tint all around
some lighting upgrades!

more to come slowly

 

Yeah.. She wasn't designed to be a drag racer.. Maybe a road course car

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2001 Silver 3.2CLS
Muds, Spoiler, Hardwire 8500, Polarg M-6 lamps, K&N filter #33-2178,
Comptech Headers, Sways, mufflers
Planning: SSR 17X7.5 GT1 Wheels, Brembo Brakes.

 

Glad you enjoyed the info. Whatever I can do for my acura-honda buddies.

More good info @ http://www.leecao.com/honda/index2.html

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2001 SAAB 9-3SE HOT

The UNBIASED voice of reason

 

I read the original post, but in my opinion, this is true of any small displacement, high revving engine. It really doesn't have anything to do with VTEC engines, except for the fact that they're usually making more power up top in the rpms.....

If you think about it, VTEC has nothing to do with launching off the line.

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99 M3
dead CL-S

Tom2: The Voice Of Reason

 

But the level torque curve created by the VTEC does. Besides, your comment seems contradictory when you say:

I think that's the whole point. More HP at higher RPM's means a more level torque curve which means less wheel spin which means more difficulty launching off the line.


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2001 SAAB 9-3SE HOT

The UNBIASED voice of reason

[This message has been edited by saabman4ever (edited 05-21-2001).]

 

What I was trying to explain is that small displacement engines usually make more power higher in the rev band, whether they have variable valve timing or not.

In other words, since the variable valve timing does not play a role in launching a car, it really does nothing to promote or inhibit a proper drag strip launch.

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99 M3
dead CL-S

Tom2: The Voice Of Reason

 

I was trying to find an e-mail address for the person who wrote that article so I could tell them how ignorant they are but none was listed. Maybe you can if you get the chance, Tom.

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2001 SAAB 9-3SE HOT

The UNBIASED voice of reason

 

Don't get sarcastic with me. If you continue to think that variable valve timing affects launching a car, then so be it.

Don't get upset with me because you can't understand the basics, bud.

By the way, don't believe everything little thing you hear/read. Chances are that its just someone's opinion, not fact. I'm sure they guy who originally wrote that meant well, but was just a little misguided in terms of variable valve timing.


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99 M3
dead CL-S

Tom2: The Voice Of Reason

 

I actually have to agree with Tom on this one. Small displacement motors tend to be high revving which usually translates to high rpms before peak torque, unless the car is more biased towards torque which usually results in lower overall rpms.

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2001 Cl-S Black on Black with Navigation
Black Tint all around (15%~45%)
Weapon-R Dragon Filter
Weapon-R Coil-Overs
Koni Adjustable Struts
Comptech Sway Bars
Comptech Headers (hehehe...I got something for you drchang!!)
14.698 @95.977mph....Sears Point Raceway.
I think I need a Level 10 Torque Converter!!

 

Changed my sig....

I am now the self appointed Captain of the Bullshit Police Force

I will personally stamp out any bullshit that I read in this forum

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99 M3
dead CL-S

Tom2: The Voice Of Reason and Captain of the Bullshit Police.

 

#1.Sarcasm is a gift. I can't help it. Deal with it.

#2. I don't want to continue to believe anything. Frankly, I could care less. I thought it was an interesting explanation on VTEC and why drag racing with one is more difficult. If the article is wrong, so be it. There was no way for me to know otherwise. I'm no automotive genius, unlike some.

Let's be friends. You drive a German car, me a Swedish one. The same Anglo-Saxon blood runs through both. mmmkay?




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2001 SAAB 9-3SE HOT

The UNBIASED voice of reason

 

Hey, Saab of course we can be friends. I have no beef w/you.....

But at the same time, if I read something that I believe to be wrong, I'm gonna speak up about it. That's just me, okay?

Nothing personal against you.....

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99 M3
dead CL-S

Tom2: The Voice Of Reason and Captain of the Bullshit Police.

 

I too, changed me sig.

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2001 SAAB 9-3SE HOT

The UNBIASED voice of reason & innocent poster of BS but thank god for Tom2; he'll stamp it right out and the world will once again be safe!

 

Damn!!! The invasion of Cl.com by the Euros!! What has this world come too!?!

------------------
2001 Cl-S Black on Black with Navigation
Black Tint all around (15%~45%)
Weapon-R Dragon Filter
Weapon-R Coil-Overs
Koni Adjustable Struts
Comptech Sway Bars
Comptech Headers (hehehe...I got something for you drchang!!)
14.698 @95.977mph....Sears Point Raceway.
I think I need a Level 10 Torque Converter!!

 

Isn't it great to see two grown up men making out on line... just beautiful!

Now please hold hands and exit the forum together.

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2001 Silver CL-S

 

I can chirp first gear whenever I want to.

What's the problem?

-J

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2001 CL-S Aegean Blue/black interior spoiler, wheel locks, no-navi
Stock for now.

 

At the risk of being seared by scathing sarcasm and being busted by the bullshit police, here's my 2-cents.

Difficult launch characteristics are a function of of the torque curve. Like the original article said, an early torque peak is conducive to easy launching since the torque output tapers off past the peak to allow the tires to hook up once the car is in motion w/o necessitating much operator talent and/or finangling.

But the flat torque curve isn't really a function of small displacement or VTEC (although both are somewhat involved in real-life applications): it has everything to do with not losing torque output as rpm rises. That is a function of breathing efficiency and mechanical resistance (reciprocating masses & mechanical drag) of the 1st and 2nd orders. (In theory any resistance of any order matters, but I guess real-life engines don't rev high enough for anything over 2nd order to matter.)

I've heard that like motorbikes and Civics, supercars can be also be hard to launch. Something like the McLaren F1 probably has a wonderous amount of torque available at very low rpm's from its high-displacement V12. Even with its gargantuan drive tires, it has no problems breaking them loose w/o revving to the moon. But it's also efficient at high rpms (that's why it's a supercar and not a musclecar) and has a relatively flat torque curve. It too is extremely difficult to launch w/the proper amount (not too little or too much) of wheelspin.

Small displacement engines are generally gifted with low reciprocating mass & mechanical drag. This contributes to a flatter torque curve, but it isn't as flat as an entire VTEC torque curve for the simple reason that small-displacement street engines can't be tuned to idle smoothly and perform acceptably at very low rpms w/o reducing the kind of valve lift and overlap that would really aid the engine's breathing efficiency at high rpms.

Of course as all you Honda fans know (or rather, should know), that's where VTEC comes in. VTEC switches between two cam profiles to basically allow an engine tuned (almost hard-tuned) for efficient-breathing to perform acceptably on the street at low rpms by reducing valve lift and overlap.

A VTEC torque curve is really the smoothed-out amalgam (do you see why the alternate induction path in your CL-S and the GS-R doens't exactly open at the same rpm as VTEC switchover?) of two already fairly flat torque curves. That makes the overall curve even flatter than any single curve.

So IMO, that's how you should really think of VTEC. Thinking about it as a horsepower improver will get you laughed at in true racing circles, since non-vtec engines are just as easily tuned to produce high specific output. What VTEC does do over these engines is allow that high specific output to be streetable, w/o being a bitch in traffic or coming down your driveway.

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051/LP/SR/LD/HH
Potenza S-02 Pole Position

The Reasonable Voice of Bias

 

I cant believe I missed this thread.

I agree with Tom. The article proves nothing. I would say that Vtec cars are harder to launch/race because of FWD rather Vtec. And let's not forget, Vtec is there no matter where you are in the rpm range. Just because the longer duration/lift cam is set at 4800 rpm, that does not mean that THAT is VTEC. The "smaller" lobes are also doing their job and are the best choice when used.

Also, I believe from the dynos I saw that our engine makes more torque at 2000 rpm than 3500 rpm. I know that this is contradictory to what Acura is posting about the engine but many dynos I saw prove that (unless if I am missing something).

Also, Vtec is not about making torque at high rpm although that is the case almost always. Vtec is about making power always. No matter if it is high or low rpm.

In the case of our engine there are 2 things that help us make toruque at low rpm other than Vtec. One is the "large" displacement which is Tom's point and the other is the fact that our engine is SOHC which theoritically makes good low rpm torque.

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Gabriel
CL Type S
Mag Racer #1