Date: Fri, 6 Sep 2002 00:24:08 -0700
Reply-To: Mark Keller <kelphoto@HIGHSPEEDPLUS.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Mark Keller <kelphoto@HIGHSPEEDPLUS.COM>
Subject: Re: Turbo question Water Jacket Seal failure
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Damon,
I may be telling you more than I know about this issue of exhaust pulse
on a boxer engine vs a inline 4 cycl. but, according to the Subaru
articles on turboing their boxer engine with cylinders on either side of
the box, the firing order of the engine means that some cylinder exhaust
pulse have further to travel before reaching the turbo, in fact I think
one cylinder exhaust tube was lengthened a bit and then it showed up at
the turbo after next in sequence cylinder's pulse that closer to the
turbo.
Obviously this is fine tuning, but the information is out there; this
is why I was referring to the location of the turbo unit, so that the
pulse impact on the impeller is at consistent intervals.. It appeared
that the issue was that the length of pipe to travel from the cylinder
to the turbo, and firing order were variables to locating the turbo.
Probably because greater distance of the boxer engines exhaust that the
Inline engines. Whatever, the issue, research some on turbo subaru 2.5
WRX tricks, I've lost the URL, but an English chap, did a article on the
motor and dyno work needed to raise output and efficiency of the 2.5
liter Subaru. I'm just suggesting your peruse this information to
factor into you location of the unit.
I think the use of an automatic transmission would be the optimum for
several reasons: built in stall convertor to 2800 RPMs; allow engine to
rev/spool up the turbo faster, durability on a high output engine,
easier to hurry the car along in traffic and such, and less shock
loading on the system.
The other issue of knock control. I researched a few of the after
market fuel injection systems and feel the one made by TEC II is a
pretty good aftermaket fuel injection application for the waterboxer.
The sell it modular, and offer a knock sensor and variable ignition
timing module. I had considered it as a replacement for my system at
one time, and would recommend you consider it. On the other hand, David
Marshall on the vanagon list reported being able to offer a variable
timing unit using a modified Rabbit control and some other pieces, but
hedged a bit on if would work without some additional debugging. So I'd
look at those two possibilities.
On the heat issue, the ceramic coating does resist heat transfer , and
by keeping the energy in the gas stream instead of sending it into the
cooling loop via the piston and cylinder head. If it stays out of the
piston, then the piston can not transfer it to the cylinder wall and
thus the cooling system. To the degree this works I can not give a
specific reduction in percent, but it is the route to go. In particular
you can pick up several other good thermal strategies from the Subaru
sites, since they face the same issues.
Have you located pistons to lower the compression ration? ? Also the
use of Pauter rocker with a modified lift ratio would be another
consideration for better gas flow, in fact it might be necessary. Just
search the archives under Pauter or Ratio Rockers.
Out of curiosity have you look at supercharging as well?
Sincerely,
Mark Keller
Damon Campbell wrote:
>
> However, your point about exhaust pulse is an interesting one. I
> thought it a non-issue because the books on turbo charging i've read
> have talked about 4cyl engines as being the low limit of acceptability
> in this regard. I suppose some sort of volume in the exhaust manifold
> before the turbo would even out the pulses. This issue with this
> being keeping the exhaust gas velocity up.
>
> "For certain the issue is keeping your heat transfer down, moderate
> boost, ceramic coatings etc."
>
> How would you recommend keeping the heat transfer down? My current
> plan is to simply install an intercooler, an auxilury oil cooler, and
> try to somehow aggressively pass air through them. Would you think
> this sufficient?
>
> Also, do you happen to know if there is an after-market anti-knock
> sensor that can modify the ignition signal and retard the spark
> timing? I'm not sure if i'll need that, but i think that would be a
> good something to be able to get.
>
> Finally, and this is my ignorance asking here, what is the ceramic
> coating you mentioned for? Is it a coating on the inside of the heads
> to reflect heat away from the aluminum? That's my only real guess...
>
> Again, thank you for your input,
>
> -Damon
>
>
>
> Mark Keller wrote:
>
> Hi Damon,
>
> Welcome to the list. My name is Mark Keller. I've thought
> some about
> the type of responses you might get from other listmember
> regarding your
> question.. MY general feeling is that you'll be told to swap
> motors or
> get a lot of flack for wanting to turbo the water boxer
> engine. Let me
> share my views as well.
>
>
> First I did an internet search on Google for the Subaru
> waterboxer that
> is turbocharged. There is nothing wrong with the basic
> layout being
> turbo charged. I could not find any issues with respect to
> the
> compression seal issue with the VW block. It seems the real
> issue was
> the exhaust pipe routing for proper pulse according to
> firing order of
> the engine to achieve a efficient spool up design. In other
> words, a lot
> of plumbing for the right setup. Drag engines I've seen,
> SPENCER's or
> SMITH VW in Tampa, Fl , had a World Record 1/8 mile
> dragster, 600 hp or
> so, that used twin turbos, but I believer the high rpm range
> overcame
> the need for pulse effect. Also this not a VW cast block,
> but a custom
> block and air-cooled, but it held together.
>
> The other item was I saw an image from a listmember in
> Japan's website
> of a turbocharger on a Vanagon engine at one of their camp
> outs. The
> listmember goes by the name of "Yoshi". If you search the
> Vanagon list
> archives for the years 1999-2001, under his name you should
> be able to
> locate is website.
>
> My general feeling of the effect on durability of the engine
> isn't
> negative, but there is a design issue that the waterboxer
> differs in
> than the Subaru. The VW cylinders are removable. This
> necessitates a
> thick rubber gasket only around the cooling jacket s to
> compensate for
> dissimilar metal expansion-- VW's use very long steel studs
> which clamp
> the aluminum cylinders and head assembly to the block.
>
> This thick rubber gasket is susceptible to hardening, much
> like rubber
> tires that are overheated during racing conditions . I've
> read a blurb
> on the Michelin site that excesive heat in the rubber causes
> a
> molecular change which resulting in the desirable short
> molecule chain
> being converted to longer molecule chains and hence a effect
> of making
> the compound of a harder rubber. I forget if this was for
> street tires,
> long term high milage tire compounds and stablile
> compostions or racing
> conditions. Either way tire rubber componds are prone to
> harding.
>
> Applying this molecular hardening to the rubber seal due to
> heat may
> offer some explanation to the waterboxer's high failure rate
> of this
> item. It would appear that high heat short term ,
> overheating, or just
> long term normal operating temperatures would affect
> adversely the
> critical pliability of the cooling jacket seal . In my
> opinion other
> driving behavior can exacerbate the failure of this seal . I
> believe
> the VW brand coolant for this engine includes some time of
> additive to
> keep attempt to keep the exposed edge of the seal pliable or
> swollen.
> This is where coolant is forced beneath the seal and
> corrosion of the
> heads surface begins. Obviously , I don't believe anything
> can
> completely compensate for the natural hardening due to
> molecular change
> of the compound, and thus the seal expansion would degrade.
>
> Another possibility are engines which have had several bouts
> of
> overheating for whatever reason. And possibly a general
> driver habit of
> driving for the first few minutes each day . During Cold
> weather or
> below water freezing first start and then operating the
> engine at 2000
> RPM s or more before the temperature needle has as least
> begun to move
> and thus subjecting the thick rubber seal to the high
> hydraulic pressure
> generated by the cooling pump and a closed thermostat, and
> thus forcing
> coolant beneath and otherwise intact seal.
>
> Therefore I believe it best to give the cylinder liners a
> chance to
> expand and have adequate clamping force on the rubber
> cooling jacket
> seal, before higher than 2000 RPMs operating, after the Temp
> needle
> moves. ON my van I wait until the needle has just begun to
> clear the
> big white mark at the bottom of the temperature gauge. But I
> only do
> this religiously on cold freezing days. Other times I just
> wait until
> the needle moves.
>
> Back now to you turbo-ing the motor. I'd consider the
> effects of higher
> heat on the hardening of this cooling jacket seal. You could
> have a
> shorter time before needing to replace the gasket, kind of
> like racing
> tires, before it hardened up. For certain the issue is
> keeping your
> heat transfer down, moderate boost, ceramic coatings etc.
>
>
> Sincerely,
>
> Mark Keller
> 91 Vanagon Carat
> Cowichan Bay, BC
>
> '84 Westy
>
>
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