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Question for all those with a 16v 2.0 block and 16v 1.8 head
snip
Dave,
I have the article on the TT head as well. You're stating that
the 2.0 head flows better because its exhaust flows 15cfm more while its
intake is 10cfm, leaving it with a net 5cfm advantage. I'm not so sure
that it's so simple.
snip
Sure it is! One head next to another!
sinip
My first guess as to the reason people think that the 1.8 head
flows better is that of the redline of the 2 motors. The 1.8 redlines at
7200; with Motronic, the 2.0 redlines at 6800. There's no sense getting
into a discussion of whether that has any bearing on how well the head
breathes (or whether the redline is in a reasonable place anyway), but that
certainly would give the impression that the head flows better.
snip
You answered the reasoning behind this yourself. CIS-E vs MOTRONIC. The
redline has only to do with the computer/fuel system not the motor.
Granted, the redline is based on the expectations of the motor but since the
2.0L 16v was built for torque and put into significantly larger vehicles
than the 1.8 a redline of 400rpm less is understandable.
snip
Secondly, if you look at the intake ports themselves, the
difference is *enormous*. It certainly looks like there would be more than
a 10cfm flow difference, and that's probably convincing people as
well. The exhaust difference is not as noticeable.
snip
Size does NOT matter under these circumstances, believe me! A friend of
mine races aircooled VWs and has always welded and D ported his heads until
we started messing around with a flow bench (a Gene Burg flow bench!) and
now he has relatively stock heads with stock sized valves and they out flow
anything he's ever messed with. The heads were ported by Brian Steele (a
friend of Gene Burg) for racing in the 70s. Now if you just want to make
raw HP and using Turbos etc. then bigger is obviously better but for N/A
stuff, the how is more important that the size.
snip
Thirdly, the fact of the matter is that the 1.8 head does make
better power at high rpms. I've yet (unfortunately) to see a back-to-back
same-car 1.8 head vs. 2.0 head dyno run. But I did do a stock 1.8 engine
run and a stock 2.0 engine run on my car -- with the same exhaust, fuel
injection system, everything. All I did was take the manifolds off, rip
the 1.8 out and put the 2.0 in. Same tranny, same driveline, same
everything. Therefore, the only difference on the dyno is the motor.
What you see in the dyno runs is that the 2.0 has an enormous
torque advantage over the 1.8 over most of the engine's range. In fact,
the 2.0 made more torque at idle than my 1.8 did at its peak. However (and
this is the reason that the stock 2.0 cars didn't knock any significant
time off the 0-60 numbers vs. the 1.8) at high revs, this advantage begins
to dwindle, and by 7200rpm, the 2.0 head isn't making much (if any) more
than the 1.8 did. Exhaust restriction comes into mind as a factor... but
other than that, the only thing to explain that drop in advantage is that
the 1.8 head is flowing better.
snip
Why would exhaust restriction come to mind? I thought you said everything
was the same but the motor? At the same time you need to realize that the
2.0L has more spinning mass. This doesn't add up to much as far as power
loss is concerned but when comparing the two as closely are you are (a
couple hundred rpm) then you need to take that into consideration. For
example, the small block chevys are known for their high rpm potentials.
Not that the big blocks can't, but it takes a lot more work on all aspects
of the engine to make a big block wind up like a small block. Same thing
with 4 cylinders. What I am saying here is that the head, by itself, is not
what made it fall flat at 7200. Plus, there is a possiblity that the block
had a mechanical problem or that something wasn't working just right in your
fuel system. Usually things start or go bad when you mess with them!
Either way, this isn't enough to prove the point your trying to make. What
we need is for someone with a 2.0L with a 2.0L head and a 2.0L with a 1.8L
head do back to back runs with identical mods and transmissions.
I have had all possible setups in my car. I had a 1.8 with a 1.8 head, then
a 2.0 with a 1.8 head and now a 2.0 with a 2.0 head. The 2.0 is much
quicker than the 1.8 with similar porting and no other mods other than HD
valve springs. If you have a 1.8L head and want to use it, go ahead, port
it, put cams it and use it. I'm not saying that the 1.8 isn't any good, I'm
just saying that the 2.0L flows better than the 1.8L in stock form. Since,
for the most part, most of our cars are NOT in their "stock form", which
head flows better is actually rather irrelevant. I chose the 2.0L head
because of the TT chart AND because it is a lot newer than the 1.8. Since
it came from a 92 GTI with low miles, I didn't have to worry about the
tensioner stud striping on me and having my new valves slam the pistons, I
didn't have to worry about the cam bearings being all used up and littered
with streaks from crap running through the oil or how many times the valve
seats had been ground. It was easy, new valves, touch up the seats a
little, deshroud and port with new guides. Plus, all the exhaust studs were
still there in perfect condition!
snip
Furthermore, 87 octane is not the best gas for the 16V. If
someone made more power using 87 on the dyno than 93, their engine is not
tuned properly. With stock ignition advance and compression ratio, the 16V
will ping non-stop on 87. The knock sensor will retard the iginition to
stop this, but in the process you'll lose power...
It is true that the energy contained in 87 octane gas is
(fractionally) higher than 93... but not nearly enough to make up for the
difference in power lost by the knock sensor. If your car doesn't enter
ignition retard mode on 87, something's up...
snip
Again, just saying all of this doesn't make it so. I run 87 in my 2.0L 16v
with CIS-E and it does fine with no knocking. I can even watch the timing
with a timing light and see it advance correctly. I realize it is different
under a load but this alone disproves your theory. Second, 87 octane has
more energy and creates less heat so a higher octane fuel that would create
more heat would also create a possibility to knock, thus be retarded also.
Whatever you do to your car (suspension, wheels, tires, intake, cams,
adjustable cam sprocket, etc.) to gain something, you will always be losing
something on the other side. Gain more hp, lose torque. Add cams, lose
torque, lose idle, gain more hp on top end, etc. etc. etc.
In order to compare two things everything around those two things need to be
identical. In your comparison everything was identical except for the block.
Give me something I can't disprove then I'll be more likely to believe it.
Especially if your trying to go up against my pals at TT!! :)
Dave
At 05:53 PM 1/10/2003, Rabbit16v wrote:
>The 2.0L head flows better than the 1.8L head in it's stock form. You got
>that backwards. I don't know how many times the link to the TT flow test
>site has been put up here on the list but it shows without a shadow of a
>doubt that the 2.0L head flows better than the 1.8L head. And, with the
>2.0L head being just plain newer than the 1.8L head, the 2.0L head is a
>better choice you don't have to worry as much about the tensioner stud
>pulling out or the cam bearings being worn so much, etc. And this is
>without even mentioning the fact that the 2.0L head has more material for
>porting than the 1.8L head. See, even though the 2.0L head has smaller
>intake ports it depends on how it is ported not necessarily how big but it
>does have larger exhaust ports so overall the 2.0L head flows better. So
if
>you find a 2.0L 16v tallblock somewhere, just slam the whole thing into
your
>car and swap the manifolds.
>
>I wonder how this whole 1.8 is better than 2.0 thing got started? Maybe
>someone who ain't into 16v. Hmmmmmmmm, MEZE?????
>
>HTH!!
>
>Dave
>----- Original Message -----
>From: "Allyn" <amalventano@sc.rr.com>
>To: "Joe Doty" <Joe.Doty@lcnetwork.com>; "Nathan Frechette"
><desertwind16v@attbi.com>; <scirocco-l@scirocco.org>
>Sent: Friday, January 10, 2003 10:36 AM
>Subject: Re: Question for all those with a 16v 2.0 block and 16v 1.8 head
>
>
>i've been wondering about this myself lately. the head chamber volumes of
>1.8 and 2.0 heads are both 45cc. so the head doesnt change c/r.
>the advantage of a 1.8 head on a 2.0 block is that the 1.8 flows better
than
>the 2.0 in their respective stock forms. this could effectively make a
>person think the engine has a higher c/r since it would get slightly higher
>max pressure readings during a compression check.
>Al
>
>
>----- Original Message -----
>From: "Joe Doty" <Joe.Doty@lcnetwork.com>
>To: "Nathan Frechette" <desertwind16v@attbi.com>; <scirocco-l@scirocco.org>
>Sent: Friday, January 10, 2003 3:06 AM
>Subject: RE: Question for all those with a 16v 2.0 block and 16v 1.8 head
>
>
> > Nathan,
> >
> > The combustion chambers on the 1.8 16v and 2.0 16v heads are identical,
so
>the head doesn't change the compression. The Bentley says the 2.0 comp.
>ratio is 10.8:1.
> >
> > Joe
> >
> > -----Original Message-----
> > From: Nathan Frechette [mailto:desertwind16v@attbi.com]
> > Sent: Fri 1/10/2003 12:03 AM
> > To: scirocco-l@scirocco.org
> > Cc:
> > Subject: Question for all those with a 16v 2.0 block and 16v 1.8 head
> >
> >
> > What does the compression ratio come out to be. I have been searching
on
>the tex and haven't been able to find good answers. Thanks
> >
> > Nate
> >
> > IIi zz j)fj b˝? (
>
>
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