The mathematics of the 8Vvs16V problem

[jason at scirocco.org (Jason)]

Heya Patrick,
         Thanks for posting that graph.  Your torque curve illustrates 
exactly what I pointed out in my last mail:

Even though your engine pushes out a very, very healthy peak of around 118 
lb-ft of torque to the wheels, it manages only 98hp.  Exactly as I said, 
the 8V concentrates its torque output down low in the rpm range - yours 
peaks at around 2700rpm.  This is ideal for a daily driver -- around town 
at leisurely rpms, your car is at its happiest.  It'll squirt off the line 
like a beast...

As you can see though, the torque curve peaks early and then falls off 
gradually as you approach redline.  Horsepower is nothing more than torque 
at high rpms.  Since your car is making relatively little torque at high 
rpms, its Horsepower number is so much smaller.  Horsepower isn't my 
favorite number when used to gauge the overall driveability and feel of an 
engine, but it's the only number you need when you're talking about all-out 
acceleration.  At full-tilt, if geared correctly, a 240hp, 3000lb Honda 
with 180 lb-ft of torque will still be even with a 240hp, 3000lb V8 with 
double the torque.

The reason why is simple:  Under full acceleration, you're between, say, 
4000rpm and redline all the time... save for the initial launch, which 
admittedly, if done properly, will be in that range, too.  Ignore what 
happens at low revs on your chart, and you'll see why a stock 1.8 16V with 
the same gearing will outrun your car... it puts more torque down at those 
speeds and can rev 1000rpm more.

Now, with that said:  Driving your car and driving that stock 1.8 16V will 
feel completely different.  Let's say you and the 16V are puttering along 
in 2nd gear at 2500rpm next to each other, and you both realize that your 
two lanes are about to turn into one, and you both gun it.  The 16V will be 
eating your hard-earned 8-Valve dust.

Now, if you both kept your foot in it, the 16V would eventually catch up 
and walk away from you.  But your subjective impression from the short race 
will be of course, that your car is faster than a 16V.

This is why I say quite clearly that the 8V is certainly not without its 
merits.  The 8V versus 16V war is certainly akin to the V8 and big 
displacement versus VTEC and revs debate, albeit on a lesser scale.  Flat 
out at the 1/4 mile, the VTEC Honda can keep up with the V8s.  The reason 
is because the high revving motor will let you take advantage of gearing, 
where the big V8 just pulls and pulls from low revs.  You have to work 
harder to keep up in the Honda, but if you do, you'll be rewarded with the 
same acceleration times as the big boys.

So yes, your car will, without a shred of doubt in my mind, be a whole lot 
more fun around town than a 1.8 16V would.  Low-end torque is what the 
American public wants -- that's why we have Buicks with pushrod 3800 
V6s.  They give fantastic acceleration off idle and feel powerful, smooth, 
and fun -- until it's time to really get moving. When it comes to the 
stoplight race - or racetrack - or 1/4 mile track - or high speed race - or 
Autobahn cruise, all of that advantage is lost, and indeed a stock 16V 
would be faster than your fun-to-drive, torquey and happy built 8V.  It's 
just a matter of physics... not me trying to diss ya!

Jason







At 10:40 AM 10/20/2003, ATS - Patrick Bureau wrote:
>jason how about this 8v (mine) I think my torque curve is quite broad, you
>got 133ft'lbs, I got 118ft'lbs torque and in the same manner of the 16v it
>instersecs the HP curve. stock JH head and 2L bottom end with only a g Grind
>in it.
>
><http://www.longcoeur.com/scirocco/various/dyno/dyno%5Fatsgtx01%2EJPG>
>
>is this what you where looking for ? or perhaps I did not understand the
>question.
>
>
>
>ATS - Patrick Bureau - txrocco@sbcglobal.net
>----------------------------------------------
>MSN:ATSGTX@hotmail.com |YAHOO:ATSGTX@yahoo.com
>ICQ:32918816           |AIM:Texasscirocco
>----------------------------------------------
>
>
>=>-----Original Message-----
>=>Case in point, please see the following curve:
>=>http://www.scirocco16v.org/dyno/16V.jpg
>=>This is a dyno plot from one of our veteran list members.  It's a 2.0 16V
>=>with a slightly P+P and shaved head; Schrick 260/276 cams, and an
>=>exhaust.  That's a relatively stock motor in my book -- the entire bottom
>=>end is completely stock.
>=>
>=>You'll see that not only does it peak out at 144whp and almost 133 lb-ft
>of torque, but the torque curve itself is tremendously broad and
>=>beefy:  This engine puts more than 120 lb-ft of torque to the wheels from
>3000 until 6250rpm.  That is a simply awesome number from a 2-liter
>engine... and
>=>flies directly in the face of any complaints of the 16V being a dog down
>low.   And further, this particular motor puts down about the same torque
>=>at 2000rpm that the 1.8 16V does at its peak -- just under 100 to the
>wheels -- which is, as we know, more torque than any VW 8V motor
>=>(including the ABA) did from the factory.  So there's monumental high-rpm
>power (VR6 territory) with low rev torque besting all other VW 4-cylinders.
>=>You just can't do that in an 8V VW motor.
>=>
>=>http://neubayern.net/mailman/listinfo/scirocco-l