for those of you that like low end torque... (long reply)

[jason@scirocco.org (16V Jason)]

At 01:29 AM 4/13/2002, Allyn wrote:
>but that is assuming that i plan on reving the 2.0 to the same rpm as i 
>would with the 1.8... would
>you consider taking a somewhat stock 2.0 block to 8000 rpm (with boost)?

It would be no more likely to explode than a 1.8, so why not?

>quote from the article:
>"It is better to make torque at high rpm than at low rpm, because you can 
>take advantage of
>*gearing*."

Right.  Allyn, please don't get me wrong, I'm not trying to be 
condescending or insulting, but your understanding here is pretty far 
off.  What you're doing is taking a few pieces of information and 
extrapolating that to a much larger conclusion.  For maximum acceleration, 
yes, it's better to make torque at high revs.  Why?  Since we have 
transmissions that gear the engine down, we are generally in the upper 2/3 
of the rev range at all times under full acceleration (except for the 
initial launch if it's not a drop-clutch).

What that article says is that higher horsepower (i.e. more torque at high 
revs) will make your car faster when run flat out.  That is completely 
correct.

Also, if you understand that gearing not only slows the engine's output 
speed down, it also multiplies the engine's torque, then you can also see 
that (given the same gearing) an engine that can rev an extra 1000rpm will 
be faster than its adversary.  Of course, that's assuming it doesn't fall 
on its face during that last 1000rpm.

For example, let's assume you have a 2-speed transmission.  Low and 
High.  Low has an overall gear ratio of 10:1.  High has 2:1.  That means 
that when you're in Low, your engine is turning 10 times as fast as the 
wheels.  In High, it's turning 2x as much.  It also means that the engine's 
torque is multiplied by 10x in Low, and 2x in High.  If you think about it, 
now you can clearly see the benefit of making an engine rev higher -- since 
the engine's torque is multiplied by so much more in Low, for maximum 
acceleration, you'd want to be able to stay in that gear for as long as 
possible.


>     I plan on making torque high (~6000 rpm peak) with p+p and boost. 
> Optimum shift points for this
>setup with an FF tranny (how i got to that decision is a totally seperate 
>issue), is beyond 8000
>rpm. This basically means that quarter mile time is directly related to 
>how high i'm willing to let
>the engine rev.

Well, yeah, kind of.  Power output also has a lot to do with that 1/4 mile 
time. :)


>     Using an 8000 rpm redline for a 1.8 block and a 7500 rpm redline for 
> the 2.0 block, i ran dyno
>simulations using dyno 2000 and plugged the results into cartest 2000, 
>getting simulated drag
>numbers. both simulation programs arent necessarily perfect as far as 
>comparing to the actual
>physical end result you will get, but they are very very good for finding 
>out which direction
>parameters go when changing variables. The result?

Why would you think the 1.8 is any more capable of revving to 8000rpm than 
the 2.0 is?  Talk to Riley McDowall about how 2.0s rev.


>     Regardless of the 2.0 having 25 more ft-lbs of torque at 6000 rpm and 
> 40 more hp at a 8000 rpm
>peak, at 7500 rpm, the 2.0 was making the same HP as the 1.8 was at 8000. 
>This is exactly how the
>'gearing' comes into play. This alone (combined with the last couple of 
>paragraphs from that torque
>article) should show the faster car.

Depends on the gear ratios in the two cars.  But honestly if you think you 
can plug a few numbers into a hypothetical program and get real-world 
values, I think we can stop this discussion here.  There is no way (read: 
no way) you will get a 1.8 16V to rev to 8000rpm and make any real 
power.  The head is not capable of that kind of flow; the ignition system 
can't deal with it, and the FI system and intake can't deal with it.  You 
might be able to get the motor to rev to that speed, but it's not going to 
be making any real power.


>     With the numbers plugged into cartest, the 1.8 was .06 faster in the 
> quarter. Now granted that
>isnt a huge gain or anything, but the mere fact that it is at least equal 
>is enough for me to bypass
>the thought of blowing $$$ on a couple of 2.0 blocks.

         But again -- your logic is flawed!  The 2.0 will make more power 
at ANY RPM than the 1.8 does!  It's a simple matter of physics -- if the 
motors are attached to the same intake and exhaust systems, and have the 
capability to flow enough fuel/air mixture internally (i.e. through the 
valves), then the 2.0 will always, always make more power.  At the very 
least, if the head is *so* restrictive that both motors peak out because of 
it, the 2.0 will make exactly the same power as the 1.8 at that point -- 
but a whole lot more during the rest of the rev range.


>I am forced to make this somewhat of a budget
>project, since the $$ is going so many directions at once it isnt funny. 
>If i can do some more
>porting and keeping the flow path clear to save the $600 in blocks, i'm 
>gonna stick witht he
>porting

If you want to stay on a budget, that's fine -- but don't kid yourself into 
thinking a 1.8 is going to make more power than a 2.0.


>Keep in mind that if you are going n/a, 2.0 is the way to go. throwing 
>boost at the engine changes
>alot of crap, shifts torque curves, and makes everything 300 times more 
>complex.

Right.  So why would you even begin to oversimplify things by making 
assumptions?  Unfortunately, your basic assumption is incorrect:  the 2.0 
and 1.8 are intricately similar designs -- they're essentially the same 
engine and head.  The laws of physics wouldn't suddenly reverse -- the fact 
of the matter is that the 2.0 will make more power at any given RPM.

I think the source of your misunderstanding is that the Motronic 2.0s have 
a lower redline than the 7200rpm in the CIS-E 1.8 16V.  That has nothing to 
do with the engine's ability to breathe; it was a function of where VW put 
the rev limiter.  None of us will probably ever know why VW put the limiter 
where they did.  In all reality, there's no reason to rev a VW 16V past 
6500 -- the ideal shift points on a stock motor are all below that point.

If you want to see a good illustration of the true differences between a 
1.8 and a 2.0, check out the link below.  That is my 1.8 16V and my 2.0 
16V.  During the swap, nothing at all was changed on the intake or the fuel 
injection system -- same intake runners, FI, everything.  Therefore, the 
result is a meaningful comparison.

What you will see is that the 2.0's advantage in torque (and thus hp) 
decreases at high revs.  This is because the 2.0 head does not flow as well 
as the 1.8's.  Once the 1.8 head goes back on (in the next few weeks), the 
difference at high revs should be the same as they are in the 
mid-range.  But even with the "sucky" 2.0 head on there, the 2.0 makes more 
torque at idle than the 1.8 does at its peak -- and continues to do so 
until redline.

Both curves are from just off-idle until the rev limiter kicked in at 
7200.  See for yourself:

http://www.scirocco16v.org/temp/curves.jpg


Not trying to prove you wrong for the sake of proving you wrong -- trying 
to help -- going with the 1.8 cause it's cheaper is fine; doing it because 
you think you will get more power is unfortunately not the case.

Jason




>ok, enough babbling outta me...
>
>Allyn Malventano, ETC(SS), USN
>87 Rieger GTO Scirocco 16v (daily driver, 170k, rocco #6)
>86 Kamei Twin 16V Turbo Scirocco GTX ('it has begun', rocco #7)
>87 Jetta 8v Wolfsburg 2dr (daily driver, 260k, 0 rattles, original clutch, 
>driveshafts, wheels :)
>
>
>----- Original Message -----
>From: "16V Jason" <jason@scirocco.org>
>To: "Allyn" <amalventano1@comcast.net>; "scirocco list" 
><scirocco-l@scirocco.org>
>Sent: Saturday, April 13, 2002 12:04 AM
>Subject: Re: for those of you that like low end torque...
>
>
> > At 09:03 PM 4/12/2002, Allyn wrote:
> > >this is a must read:
> > >http://g-speed.com/pbh/torque-and-hp.html
> > >puts things in very good perspective. i'm definitely sticking with 1.8's
> > >in the twin now.
> >
> > Hang on Allyn -- you mean to say that you're going to stick with 1.8s
> > instead of going to 2.0s?!  If that's the case, you might wanna re-read
> > that article.  The 2.0 has a tremendous amount more low-end torque, but it
> > also has significantly higher high-rpm torque; and therefore also more
> > horsepower.  And therefore it's much faster.
> >
> > Jason
> >
> >
> >
> >
> > >Allyn Malventano, ETC(SS), USN
> > >87 Rieger GTO Scirocco 16v (daily driver, 170k, rocco #6)
> > >86 Kamei Twin 16V Turbo Scirocco GTX ('it has begun', rocco #7)
> > >87 Jetta 8v Wolfsburg 2dr (daily driver, 260k, 0 rattles, original clutch,
> > >driveshafts, wheels :)
> > >
> > >
> > >_______________________________________________
> > >Scirocco-l mailing list
> > >Scirocco-l@scirocco.org
> > >http://neubayern.net/mailman/listinfo/scirocco-l
> >
>
>
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