V8 PSRU discussion

klehman · Post by **klehman** » Fri Feb 17, 2012 11:02 pm

Yes there be bubbles !

I do know of one large (several gallon) unvented header tank
successfully flying in a high wing aircraft but even he has admitted
that he must be on the ground to reliably vent the tank manually and
restablish flow if he runs it dry.

Fuel is a mixture of compounds. When it is heated in the pump and fuel
rail all is fine as it is under increased pressure. However the more
volatile components will form vapour bubbles when the pressure drops
back to ambient across the fuel pressure regulator. With a large enough
and cool enough tank, most will recondense if they are returned to the
tank. High altitude, mogas, and warm fuel from lots of recirculation
won't help them recondense. With no fuel return, too many bubbles may
shorten the fuel pump life and has caused loss of prime as the pump
tries to suck vapour. So yes there can certainly be bubbles but most are
fuel vapour. In turbulence, there might be some entrapped air as well.

With a header tank vent, slugs of air from turbulence, side-slipping, or
low fuel also become a non issue as they can vent back to the cross tank
vent on my installation. I'd highly recommend that if a header tank is
used, it be vented. I think of a carbuerator float bowl as a header. It
separates vapour, provides a small fuel reservoir, and is vented one way
or another.

Ken

rickhm@mindspring.com wrote:

I read somewhere on the web that many use UN-vented Header tanks that the return line flows back into. Additionally, they recomended a circulation pump between the header tank and the main tanks.

I guess I have a fundemental question. Is the return fuel full of air bubbles? Ken your comments suggest that this is the case. If true, I guess I find this surprising since the fuel is at 50-60 PSI as it hits the jets.

Rick Muller
SR70

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klehman · Post by **klehman** » Fri Feb 17, 2012 11:02 pm

I agree, there has to be a simpler way than recirculating pumps even if
its an additional one or two quart header tank or a duplexed 6 port
Andair selector valve. It would be difficult to confirm that a
recirculating pump is working. I'd imagine a vent line would be easier
to install than fuel return lines. Let us know what you decide.
Ken

Rickhm at home wrote:

Ken,

Great feedback. I see your point. I'm not sure exactly how I will address
this, but your suggestion is a very viable option. I may put a pump on
each side before the header tank so the gas is constantly recirculating
between the main tanks and the header. I saw this as a recommendation. Bu
doing this the fuel in the header is constantly cycling with that in the
main. Any bubbles will hopefully be caught and sent back to the main tank.
These recirculation pumps are not high pressure pumps like that of the
fuel injection side, but more traditional pumps.... I still need t think
about this a bit. The part I am still pondering is failure analysis and
what if's.....

Thanks again!

RIck
SR70

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Reed, Britt/FSC Salt Lake · Post by **Reed, Britt/FSC Salt Lake** » Fri Feb 17, 2012 11:02 pm

I recently found an interesting (if a little stale) web site talking V8 PSRU
- http://www.epi-eng.com/
These guys seem to have had a firewall forward offering for the Lancair but
things didn't work out so good and they had to regroup - Some good
information though -

E-mailed the address and got these responses -

From Epijk@aol.com

LS6 could be an excellent choice (depending on configuration).
Without more details, I think 1.8 isn't enough (too much prop RPM).
4800 is a good engine limit, but 2700 is too fast for an efficient prop
capable of 300 or more HP on a fast airplane.
Our Mark-9 is available from EngineAir (email dpohl@adelphia.net) in
a 2.19 and 2.37.
Jack Kane
EPI, Inc.

From Doug Pohl [dpohl@adelphia.net]

I've attached the portion of the Engine Power Systems brochure that
briefly
describes the gearbox. All of the parts are now made by aerospace
manufacturers to ISO 9003 standards. This of course increases the
cost of
the gearbox. The current cost is about $15,000. Please be aware
that the
gearbox was specifically designed for the small block chevy
configuration
and I'm not sure of its ability to be used on the engine you
described.

I was looking at the IVO Prop 84", thinking V8 max RPM 4800 and messing with
the prop speed calculator at
http://www.bewersdorff.com/computational/prop.html - The higher, faster and
colder you go, the closer to the speed of sound you get but it seems like
the the full engine output is at the take-off phase of flight and tends to
be at lower elevation and at Vx or Vy. It shows Mike Kimballs choice of
ratio at ~~1.8 to be on target but the above e-mail from Jack Kane
at EPI, Inc. would spin the prop at 2200 with the engine at 4800 (and the
Marko's Prop Tip Speed Calculator says spin it faster)- Am I missing
something here??

Anyway - $15000 seems like its out of my league -

Britt - 194SR

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Wayne G. O'Shea · Post by **Wayne G. O'Shea** » Fri Feb 17, 2012 11:02 pm

The last bit of Britt's message showed the guys Mark-9 available in 2.19 and
2.37 ratios! This is where the 2200RPM came from.

I'm no expert (or even amateur) on propellor/speed selection but can offer
that my UTVA's 340HP GSO-480 engine turns 3400RPM for take off and the
propellor is only turning 2182RPM (77to120 ratio)and the thrust will throw
you back into the seat just like dumping the clutch in my '69 SuperBee! Prop
is a three blade 96" Hartzell.

Cheers,
Wayne

----- Original Message -----
From: "Mike Davis" <mike.davis@dcsol.com>
To: <murphy-rebel@dcsol.com>
Sent: Thursday, May 15, 2003 7:22 PM
Subject: Re: V8 PSRU discussion

My calc shows at 4800 with 1.8 reduction 4800/1.8=2666.67... close to the
2700 mentioned in his message.

Mike

----- Original Message -----
From: "Reed, Britt/FSC Salt Lake" <BReed@slcrail.com>
To: <murphy-rebel@dcsol.com>
Sent: Thursday, May 15, 2003 8:40 AM
Subject: Re: V8 PSRU discussion

I recently found an interesting (if a little stale) web site talking V8
PSRU
- http://www.epi-eng.com/
These guys seem to have had a firewall forward offering for the Lancair
but
things didn't work out so good and they had to regroup - Some good
information though -

E-mailed the address and got these responses -

From Epijk@aol.com

LS6 could be an excellent choice (depending on configuration).
Without more details, I think 1.8 isn't enough (too much prop RPM).
4800 is a good engine limit, but 2700 is too fast for an efficient prop
capable of 300 or more HP on a fast airplane.
Our Mark-9 is available from EngineAir (email dpohl@adelphia.net) in
a 2.19 and 2.37.
Jack Kane
EPI, Inc.

From Doug Pohl [dpohl@adelphia.net]

I've attached the portion of the Engine Power Systems brochure that
briefly
describes the gearbox. All of the parts are now made by aerospace
manufacturers to ISO 9003 standards. This of course increases the
cost of
the gearbox. The current cost is about $15,000. Please be aware
that the
gearbox was specifically designed for the small block chevy
configuration
and I'm not sure of its ability to be used on the engine you
described.

I was looking at the IVO Prop 84", thinking V8 max RPM 4800 and messing
with
the prop speed calculator at
http://www.bewersdorff.com/computational/prop.html - The higher, faster
and
colder you go, the closer to the speed of sound you get but it seems

like

the the full engine output is at the take-off phase of flight and tends

to

be at lower elevation and at Vx or Vy. It shows Mike Kimballs choice of
ratio at ~~1.8 to be on target but the above e-mail from Jack Kane
at EPI, Inc. would spin the prop at 2200 with the engine at 4800 (and

the

Marko's Prop Tip Speed Calculator says spin it faster)- Am I missing
something here??

Anyway - $15000 seems like its out of my league -

Britt - 194SR

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Mike Davis · Post by **Mike Davis** » Fri Feb 17, 2012 11:02 pm

My calc shows at 4800 with 1.8 reduction 4800/1.8=2666.67... close to the
2700 mentioned in his message.

Mike

----- Original Message -----
From: "Reed, Britt/FSC Salt Lake" <BReed@slcrail.com>
To: <murphy-rebel@dcsol.com>
Sent: Thursday, May 15, 2003 8:40 AM
Subject: Re: V8 PSRU discussion

I recently found an interesting (if a little stale) web site talking V8

PSRU

- http://www.epi-eng.com/
These guys seem to have had a firewall forward offering for the Lancair

but

things didn't work out so good and they had to regroup - Some good
information though -

E-mailed the address and got these responses -

From Epijk@aol.com

LS6 could be an excellent choice (depending on configuration).
Without more details, I think 1.8 isn't enough (too much prop RPM).
4800 is a good engine limit, but 2700 is too fast for an efficient prop
capable of 300 or more HP on a fast airplane.
Our Mark-9 is available from EngineAir (email dpohl@adelphia.net) in
a 2.19 and 2.37.
Jack Kane
EPI, Inc.

From Doug Pohl [dpohl@adelphia.net]

I've attached the portion of the Engine Power Systems brochure that
briefly
describes the gearbox. All of the parts are now made by aerospace
manufacturers to ISO 9003 standards. This of course increases the
cost of
the gearbox. The current cost is about $15,000. Please be aware
that the
gearbox was specifically designed for the small block chevy
configuration
and I'm not sure of its ability to be used on the engine you
described.

I was looking at the IVO Prop 84", thinking V8 max RPM 4800 and messing

with

the prop speed calculator at
http://www.bewersdorff.com/computational/prop.html - The higher, faster

and

colder you go, the closer to the speed of sound you get but it seems like
the the full engine output is at the take-off phase of flight and tends to
be at lower elevation and at Vx or Vy. It shows Mike Kimballs choice of
ratio at ~~1.8 to be on target but the above e-mail from Jack Kane
at EPI, Inc. would spin the prop at 2200 with the engine at 4800 (and the
Marko's Prop Tip Speed Calculator says spin it faster)- Am I missing
something here??

Anyway - $15000 seems like its out of my league -

Britt - 194SR

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