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1.8L head on 2.0L block
well I have a stock 1.8L on a 2L block , but its 8v, npw anyone has a stock
2L engine 8v on hand and we can compare..
I need to get a dyno run though.. :)
ATS - Patrick Bureau - txrocco@sbcglobal.net
Http://www.longcoeur.com/scirocco/
============================================
'85 2.0L Prowler Orange Kamei X1 Rocco
'85 1.8L Titian Red Rocco (daily driver)
'98 4.0L Jeep Cherokee
'91 7.3L F250 diesel Super cab,8 Ft box.
=>-----Original Message-----
=>From: scirocco-l-bounces@scirocco.org
=>[mailto:scirocco-l-bounces@scirocco.org]On Behalf Of Dave Ewing
=>Sent: Saturday, June 28, 2003 11:47 AM
=>To: scirocco-l@scirocco.org
=>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
=>> > >
=>> > >
=>> > >
=>> > >_______________________________________________
=>> > >Scirocco-l mailing list
=>> > >Scirocco-l@scirocco.org
=>> > >http://neubayern.net/mailman/listinfo/scirocco-l
=>> >
=>> > _________________________________________________________________
=>> > MSN 8 with e-mail virus protection service: 2 months FREE*
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=>> >
=>> >
=>> > _______________________________________________
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=>> > Scirocco-l@scirocco.org
=>> > http://neubayern.net/mailman/listinfo/scirocco-l
=>>
=>>
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