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Who the Hell has dynos of 1.8 vs 2.0 stock heads! was Re: 1.8L headon 2.0L block
Or better yet, who has a stock 2.0 head on a 1.8! I'm hearing some voices
saying the 2.0 is the hot head. Why not on a 1.8?
Seriously, I would imagine most people have stock heads. Just because a 2.0
short block is installed doesn't mean the money to pay somebody or the
talent to do it yourself is available to port the head.
But, the original question was which head (presumeably stock) is better (I
believe from a performance point of view1!). I'm still holding out for some
dyno graphs.
A word about butt dynos!(from one of Allyn's posts) First, they are
impossible to calibrate! ;^) Second they respond to change rate of change
of acceleration, not acceleration. Didn't I already relate the story about
the Audi R8 driver's (Professionals!) thinking the direct injection engine
was slower despite it producing gobs more torque!
Dan
----- Original Message -----
From: Dave Ewing <MK1Scirocco16v@attbi.com>
To: <scirocco-l@scirocco.org>
Sent: Saturday, June 28, 2003 12:47 PM
Subject: Re: 1.8L head on 2.0L block
> But who in the world has a stock 1.8L head on a stock 2.0L block and a
stock
> 2.0L head on a stock 2.0L block?? Anyone??
>
> Dave
> ----- Original Message -----
> From: "Dan Bubb" <jdbubb@ix.netcom.com>
> To: <scirocco-l@scirocco.org>
> Sent: Saturday, June 28, 2003 6:44 AM
> Subject: Re: 1.8L head on 2.0L block
>
>
> > I've been thinking about this alittle more. We all know what that means!
> > I was thinking about the conditions in the cylinder during the intake
and
> > exhaust and how that is related to flow.
> > The power an engine produces is largely related to how much air it
burns.
> > >From that is subtracted the various inefficiencies. Pumping losses,
> > inefficient combustion, heat losses.....
> > If your intake is restrictive then you get less air and proportionally
> less
> > power. So, 7% less air pretty much starts you at 7% less power. The
> probable
> > most important secondary effect on the intake side is intake velocity.
The
> > same amount of air at a lower velocity will generally produce less
> > turbulence in the combustion chamber, slower burn and less power.
> > Flow thru the exhaust is not a power producer. It's a power loss. The
> > exhaust valve starts to open well before the piston reaches BDC on the
> power
> > stroke while the cylinder pressure is still very high. So, alot of the
> > exhaust gets a huge boost out the port due to the really high pressures
> > (compared to intake pressures or the average pressure level in the
exhaust
> > system).
> > Once this slug of exhaust is out the piston still has to do work to
force
> > the rest of the exhaust into the pipe, but the general exhaust system
> > pressure isn't that high (on the order of a couple psi even for an
> > inefficient system) so the power lost pushing the remaining exhaust out
is
> > not huge. Now, obviously, the lower the exhaust port flow the more power
> is
> > lost pushing the exhaust out and you also will get more charge dilution
> with
> > high exhaust back pressures that will have an effect on the amount of
> power
> > produced by the incoming charge.
> > The main point is; power is directly related to intake flow, it is
> > secondarily related to exhaust flow. i.e. the cylinder pressures
producing
> > power (in the area of 1000 psi) are directly related to intake flow and
> the
> > cylinder pressures loosing power (<10psi) are directly related to
exhaust
> > flow.
> > Having said all that it seems like intake flow is the most important
(and
> as
> > Dave points out, it's not just the port. it's the entire intake tract)
and
> > exhaust flow of secondary, although not insignificant, importance.
> > On the topic of intake velocity; I'm not sure the 2.0 head necessarily
has
> > better velocity despite the lower flow. I haven't seen an actual 2.0
head,
> > only pictures, so I could be wrong, but it seems the primary restriction
> to
> > flow is the center divider between ports is a big chunky lump on the 2.0
> and
> > is more streamlined on the 1.8. So, it could be lower flow without the
> > benefit of higher velocity.
> > Anyway, having now shot my mouth off again in favor of the 1.8 head, I
> still
> > would like to see dynos comparing the two heads.
> > Dan
> >
> > ----- Original Message -----
> > From: L F <rocco16v@netzero.net>
> > To: Dave Ewing <MK1Scirocco16v@attbi.com>; <scirocco-l@scirocco.org>
> > Sent: Saturday, June 28, 2003 7:34 AM
> > Subject: Re: 1.8L head on 2.0L block
> >
> >
> > Dave,
> > You are right; the exhaust is positively expelled, whereas the intake
> only
> > relies on vacuum to fill the cylinder (NA engines).
> > However, the intake isn't more "restrictive" per se, it just doesn't
have
> > the irresistable force in action that the exhaust has. This is why the
> > intake valve(s) is almost always larger than the exhaust valve(s)....the
> > intake needs all the help it can get.
> > You stopped short on one sentence; the exhaust has to exit the
tailpipe
> > into the atmosphere....not just into a pipe. (that's why low restriction
> > mufflers/cats, mandrel-bent large diameter tubing, etc. are important)
> > It's one reason to try to put the end of the tailpipe in a low-pressure
> area
> > of the vehicle rather than a high-pressure area; helps scavenging.
> > Good disscussion.
> >
> > Larry
> > sandiego16v
> >
> > ----- Original Message -----
> > From: Dave Ewing
> > To: scirocco-l@scirocco.org
> > Sent: Saturday, June 28, 2003 1:10 AM
> > Subject: Re: 1.8L head on 2.0L block
> >
> >
> > Along with Chris's statement, wouldn't you think that the pressure
that
> > the
> > piston creates when forcing the exhaust out of the cylinder is greater
> > than
> > the vacuum that is created via the throttle body? As far as exhaust
is
> > concerned (atleast the type of exhaust that most of us are running,
> fairly
> > free flowing) I would have to say that the intake is more restrictive
> than
> > exhaust. I realize you can increase intake flow by adding a cam or
> bigger
> > TB or whatever but it is limited to some extent or another, the
exhaust
> on
> > the other hand only has to exit the head into a pipe. It doesn't have
> to
> > pass through the air filter, intake boot, TB, intake, etc. I don't
know
> > if
> > this is relevant but something that makes sense to me.
> >
> > One other point to consider is that I would rather have the exhaust
flow
> a
> > little better than the intake (whether the intake ports are hogged out
> or
> > not, either way) so that the heat is leaving the motor more
efficiently.
> > 16v motors run hotter due to their increased compression and the
higher
> > rpms
> > needed to make useable torque.
> >
> > I understand the importance of velocity, speed, etc. but when you
> consider
> > that you could make a smaller port flow better than a larger port then
> > this
> > would be an argument against the 1.8 head considering that the 2.0
heads
> > are
> > newer and more technology has gone into the port design. I don't know
> the
> > specifics but wouldn't you agree that VW wants to consistantly improve
> > their
> > motors especially with tighter emmissions standards?
> >
> > Actually, all of this is rather irrelevant as most power hungry
listers
> > have
> > already ported and polished their 1.8 or 2.0 heads so stock standards
> > don't
> > really apply but I, again, would much rather have a newer head on my
car
> > that hasn't seen as many miles or as many kids beating it to death.
> Since
> > the 1.8 heads came on the scirocco/jetta/golf and the 2.0 heads only
> came
> > on
> > the jetta/golf/passat, I'd think that the 1.8 heads on the sciroccos
> have
> > taken the most beating.
> >
> > Dave
> > ----- Original Message -----
> > From: "Chris DeLong" <green536@hotmail.com>
> > To: <amalventano@sc.rr.com>; <jdbubb@ix.netcom.com>;
> > <scirocco-l@scirocco.org>
> > Sent: Friday, June 27, 2003 3:52 PM
> > Subject: Re: 1.8L head on 2.0L block
> >
> >
> > > Ok so then you are saying that increased air velocity due to port
size
> > and
> > > shape DOES NOT flow more air? Hmm, I would think that INCREASED air
> > velocity
> > > would yeild more flow due to the forced induction characteristics
that
> > you
> > > mentioned below.
> > >
> > >
> > >
> > > Chris DeLong
> > > Fine Tuning
> > > 206.367.5503
> > > www.finetuningperformance.com
> > > Seattle, WA USA
> > >
> > >
> > >
> > >
> > >
> > > >From: "Allyn" <amalventano@sc.rr.com>
> > > >To: "Chris DeLong" <green536@hotmail.com>,
> > > ><jdbubb@ix.netcom.com>,<scirocco-l@scirocco.org>
> > > >Subject: Re: 1.8L head on 2.0L block
> > > >Date: Fri, 27 Jun 2003 14:05:54 -0400
> > > >
> > > > > More airflow=better efficiency=more power.
> > > >
> > > >umm
> > > >depends on runner diameter/taper / rpm
> > > >rpm change = different intake air pulse size/speed, therefore some
> > > >configurations make more power at low rpm, where some others make
> more
> > > >power
> > > >at higher rpm.
> > > >just boring the crap out of intake doesnt give you more airflow in
> all
> > > >situations. narrower intake passages cause faster air velocity
while
> > > >filling
> > > >the cylinder, and that very momentum can actually cause a forced
> > induction
> > > >effect, as it squeezes that much more air in the cylinder just
before
>
> > the
> > > >intake valve closes. this is how some engines can have a volumetric
> > > >efficiency approaching (and possibly exceeding) a value of 1. the
> > narrower
> > > >intake is not perfect though, as it begins to restrict airflow at
> > higher
> > > >rpm.
> > > >
> > > >so... from an intake perspective, a stock 1.8 head is meant to flow
> > most
> > > >efficiently at a higher rpm than a stock 2.0 head is meant to.
> > > >Al
> > > >
> > > >
> > > >
> > > >_______________________________________________
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> > > >Scirocco-l@scirocco.org
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> > >
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