[xk-engine] Re: XK-engine-digest V1 #132

Paul,

Are you asking about power or torque outputs? The figure of 90ft/lbs per
litre is a torque (equivalent to a 90lb weight hanging off a 1 foot stick).
Power will be in bhp (brake horse power) or kW(kilo Watts). Where 1 bhp =
about 0.76 kW.

The “magic” number has always been 100 bhp/litre displacement and a number
of engines have achieved this figure, although why the units are a mixture
of imperial and metric measurements is beyond me. It’s probably an easy way
of relating power to capacity as 100:1.

From memory the Honda S2000 has an output in excess of 100bhp/litre but the
bloody thing does it at 9000rpm.

Cheers

Shane

Does

anyone know why the normally aspirated engine seems to have a limit of 90
ft/lbs per liter ? All the effort is then taking the 90 and multiplying it
by
higher and higher rpms. I’ve heard this several times and can’t find a
reason. Anyone know of a NA engine with a higher output ?

Paul Saltwick


Date: Fri, 02 Mar 2001 21:37:43 +0100
From: Thomas Herb thomas.wagstyl@speedkom.net
Subject: [xk-engine] cams

Does anybody know to which car these cams belong? Do they have the same
timing dates as XK120/140/150?
C14985 and C13081

Best regards
Thomas


Date: Fri, 2 Mar 2001 15:51:36 -0800
From: jagmkix@cwo.com (Larry Martz)
Subject: [xk-engine] cams - reply

3/2/01

Hi Thomas Herb & all – Thomas, your C14985 is the inlet camshaft for a Mk
IX with the electric rev counter, eng. #s NC3909 to NC9999, NE 1001 and
subs. Your C13081 is the exhaust camshaft for any Mk IX. The Mk IX, all
with 3.8 litre engines, was built from 10/58 through 9/61, so I suspect
the
3.8 litre XK150 (built in the same time period) is the same. Not as sure
about the XK140 and XK120, because these were earlier periods, and with
3.4
litre engines. I hope this helps – Larry Martz


Does anybody know to which car these cams belong? Do they have the same
timing dates as XK120/140/150?
C14985 and C13081

Best regards
Thomas


Date: Sat, 3 Mar 2001 10:46:06 -0700
From: “Bob Grossman” tgman@ix.netcom.com
Subject: Re: [xk-engine] piston clearance

Great point Paul. To my knowledge, the only real improvement in
torque/displacement has come from improved burn characteristics in the
combustion chamber; i.e., turbulence, plug placement, friction losses. I
must expose my ignorance of modern torque/displacement specs and you’ve
once
again piqued my curiosity! BTW, who in the world could remember when Honda
went to the exorbitant expense of producing and sealing an oval cylinder!
Oh, well, more technology for the dusty archives of recip motors.
Bob Grossman

Rick wrote:

Many pistons are actually designed to grow at different rates
themselves.

That is they expand into ovals instead if cylinders.

Hello Rick,

I think you'll find that most pistons are cam ground in an oval

shape

and

expand at the pin axis into a circle, unless you are talking about Honda
Grand Prix motorcycle engines. This is caused by a heat differential.
Pistons should be measured across the thrust face because of this
difference.
True oval pistons in oval cylinders are banned from racing because they
are
very expensive and allow more valve area. If 106 mm is long today, what
do

you think the bore clearance was on a 1911 Fiat with a 200 mm stroke ?
Does
anyone know why the normally aspirated engine seems to have a limit of
90

ft/lbs per liter ? All the effort is then taking the 90 and multiplying
it
by

higher and higher rpms. I’ve heard this several times and can’t find a
reason. Anyone know of a NA engine with a higher output ?

Paul Saltwick


Date: Sat, 3 Mar 2001 10:57:34 -0700
From: “Bob Grossman” tgman@ix.netcom.com
Subject: Re: [xk-engine] cams

C14985 is a late 3.8L inlet cam, i.e., E-Type. C17138 would be the
matching
exhaust cam. I think the C13081 cam will be found in the 3.4/3.8/2.4L
parts
lists. Unfortunately, mine are out on loan at the moment. In the year
ranges
of 120 (3/8" lift)/140/150, the 3/8" lift cams all have the same lobe and
timing characteristics unless they come from the factory or aftermarket
racing applications.
Bob Grossman

Does anybody know to which car these cams belong? Do they have the same
timing dates as XK120/140/150?
C14985 and C13081

Best regards
Thomas


Date: Sat, 3 Mar 2001 13:37:37 EST
From: Tlsalt@aol.com
Subject: [xk-engine] SU carb flow rates

Stephan Kassner wrote:

Hi listers!

Does anyone have, or know where I can get, reliable CFM
flow rate figures for the range of SU carbs H, HD, HS, HIF.

Hello Stephan,

Did you ever get an answer ? I would also like these figures if you

found

them. I looked around and couldn’t find much. I don’t think SU’s were
ever
rated using the American standard of CFM @ 1.5" Hg. What are you trying
to
figure out ? I can offer some observations and a few figures. According
to
Holley, a 4.2 liter engine with a 100% volumetric efficiency (VE) can
inhale
around 425 CFM @ 6000 rpm using their standards. A Jaguar road engine
would
have a lower VE. The factory output chart of the Series III XJ-6 implies
a
peak VE of 78% at peak torque and a 71% VE @ 5000 rpm. That would
translate
to a flow requirement of around 350 CFM. Remember this engine had the
largest valves and the longest duration cams, although it’s peak power was
400 rpm lower than the “E”. A 200 hp Jaguar engine at 80% VE would be
using
1400 lbs/hr of air and around 105 lbs/hr of fuel, so the numbers aren’t
far
off. Jaguar also published flow rates of the “C” Type head in 1953 which
had
a maximum flow of 85 CFM per port (510 CFM).

Terry once posted that the E Type triple HD8's flowed about 900 CFM, a

lot more than most Jaguar engines need. He also said that the HD8’s never
fully open up on the dyno and there was no power loss from fitting 3
HD6’s,
which, based on area, should flow 23% less or 690 CFM (using 900 est.).
If
900 CFM is a good number, 2 HD8’s should flow around 600 CFM, but the
manifold will come into play. Even if you consider the highest output
engine
I’ve found reliable figures on (GTJ’s level 6) 370 hp @ 5300, 372 ft/lbs @
5200, the triple HD8’s have more than enough flow. This engine has an
implied VE of 124% (much higher than even a D Type engine ?) which
translates
into a flow requirement around 500 CFM. Even if you use Holleys +30% CFM
recommendation for sizing carburators, this engine would run a 650 CFM
Holley.
I think you’ll find that most Jaguars, unlike many other engines, were
over-carburated. The head runs out of flow before the carbs, which is why
the highest output racing engines can use the stock set up with different
needles. The sales literature from the sixties indicates an 8% increase
in
peak power from adding a third HD8 to the same engine, but the numbers
don’t
prove out. Most people will tell you that adding a third carburator will
double your power, so the marketing must have done it’s job. Jaguar also
doubled the effect of raising the compression on the same engine. People
that have swapped the HD6’s on a Mark II with HD8’s (me included) will
tell
you there is little gained but higher fuel costs. If you take a good look
at
the acceleration figures published for a Coombs Mark II, they are pure
fantasy. The decrease in 0-100 mph time would require a 60% increase in
hp,
which is beyond silly for a balance, port and polish, and bigger carbs.
But
the truth never sold any cars, perhaps they took the numbers on the moon.

Paul Saltwick


Date: Sat, 3 Mar 2001 13:53:25 EST
From: Tlsalt@aol.com
Subject: [xk-engine] Torque limits

Bob Grossman wrote:

To my knowledge, the only real improvement in
torque/displacement has come from improved burn characteristics in the
combustion chamber; i.e., turbulence, plug placement, friction losses. I
must expose my ignorance of modern torque/displacement specs and you’ve
once
again piqued my curiosity!

Hello Bob,

I was beginning to worry that the 37 foot trailer caught you out in

turn

  1. If you look at it closely, it is puzzling. Even the 800 hp, 3 liter
    F1
    engines can only muster around 90 ft/lbs liter and the new BMW M3 road car
    can manage 84 ft/lbs liter. Are you interested in the F 1 race tomorrow?
    I
    think the Jaguar qualified 11th and Niki Lauda is already out looking for
    new
    drivers. I still don’t know if I can get it on TV, I sure would like a
    look
    at “Bernie-vision”. Montoya is a 25:1 bet, probably worth taking, and the
    Jordan Honda outqualified the Mclaren. I found out the source of the
    “Crankshaft-less” motor rumor…it was a misprint in a European
    magazine
    in an article about the 111 degree Renault motor and it should have read
    “camshaft-less”. They are planning for electromagnetic valves with no
    throttles, but so far all they have done is blow up motors.

Paul Saltwick


Date: Sat, 3 Mar 2001 21:52:22 -0000
From: “Stephan Kassner” kassner@myisp.co.uk
Subject: Re: [xk-engine] SU carb flow rates

Paul

No answer - not yet. . . .

Excellent information - Thanks!
More information for the equation. Your figures on VE are
most welcome.

I’m trying to work out if dual HIF6 or HIF44 carbs (listed in increasing
ease of obtainabilty) would provide me with the flow rates required for
my 4.2 engine. I’m sure that both types would be adequate with a
bit of modification.

I have gathered a few figures for S.U. carbs, the reliability of which I
would very much like to confirm from those more knowledgeable.

These are the figures I have for standard unmodified S.U. carbs:

H1 ?
H2 ?
H4 130 CFM
HD4 ?
HD6 231 CFM ( based on your area math)?
HD8 300 CFM (Terry’s figures)
HS2 ?
HS4 142 CFM
HS6 210 CFM
HS8 ?
HIF4 ?
HIF6 240 CFM
HIF7 ?
HIF38 ?
HIF44 150 CFM

Anyone like to add corrections/ fill in the gaps?

I have assumed that the HIF 4, 6, 8, flow more than the equivalent
H, HD & HS carbs of same size. Newer metric sized HIF44 etc carbs
don’t appear to flow as high as the older HIF6 etc, Whether they can
be made to flow equivalent? The main difference between the HIF6
and the HIF44 is that the throttle body bore is smaller in the
HIF44 (1.73") than in the HIF6 (1.75") also the main jet bridge
is much higher in the HIF44, restricting air flow.

In modified form all SU carbs can be made to increase flow rates > 30%

Here are some more figures I gleaned from various sources:

Based on the Theoretical Air Consumption - 4.2 liter engine
(approx) 74 CFM per 1000 rpm @100% Volumetric Efficiency.

369 CFM @ 5000
406 CFM @ 5500
442 CFM @ 6000 ( not dissimilar to your Holley figures)

Now working from HP figures I understand that 1hp requires between
1.4 & 1.8 CFM. So assume 200hp output from the jag engine = 280
and 360 CFM respectively.

Again these figures would agree with your reduced approx VE 71% / 78%

Keep up the good work Paul. I look forward to your posts.

Regards

Stephan K.


Date: Sat, 3 Mar 2001 17:29:19 -0500
From: holland-rick@juno.com
Subject: Re: [xk-engine] piston clearance

Whoops!

Paul is right! they start cold as an oval and go round at temp. I wrote
it bassackwards!!

Paul I wasn’t referring to the oval pistons in Hondas but the slight
oval"ity" you can measure on modern pistons. There isn’t anyone that I
know that could effectively “bore an oval” in a block nor would they have
the tools to do it anyway!!

Don’t know about the 1911 Fiat but the way your text read it seems a step
“up” from steam, perhaps Fiat was using cylinders from that schooling.
Didn’t quite understand your question on pressure and stroke in reference
to natural aspiration, unless you are asking at what time (in RPM) a
cylinder cannot be filled with air (even if the top were completely open)
because the air cannot “travel” fast enough to fill the lower confines of
the cylinder and remain at its normal density. There are formulas for
this bore stroke to ingestion maximums but I don’t know them. The
“topless cylinder” of course would have a Max opening but there are
various combinations of valving and intake designs that tend to restrict
flows in “normal” engines. There are methods that will slightly enhance
the input speeds. This type of “tuned input” enhancement is usually high
band conscious and not well suited for road car engines requiring a wide
range of RPM. There are velocity stacks and manifold designs that have
been avail for this purpose. But each time you get something at one end
you are apt to loose something at another…

I will read it over again if I can find it. I know there are many guys
out there that can answer this stuff “off the top”…

Thanks and regards,
Rick,
677342-DHC
673190-Roadster
Somerville NJ, USofA


Date: Sat, 3 Mar 2001 21:43:55 EST
From: Tlsalt@aol.com
Subject: Re: [xk-engine] piston clearance

Rick wrote:

There isn’t anyone that I know that could effectively “bore an oval” in a
block nor would they have the tools to do it anyway!!

Hello Rick,

Honda can and did, until it was banned. I don’t know what the tools look
like, but nothing is out of bounds for those guys.

Don’t know about the 1911 Fiat but the way your text read it seems a step
“up” from steam, perhaps Fiat was using cylinders from that schooling.

Bore size was restricted, so go for the longest stroke you can get.

Didn’t quite understand your question on pressure and stroke in reference
to natural aspiration, unless you are asking at what time (in RPM) a
cylinder cannot be filled with air (even if the top were completely open)
because the air cannot “travel” fast enough to fill the lower confines of
the cylinder and remain at its normal density. There are formulas for
this bore stroke to ingestion maximums but I don’t know them. The
“topless cylinder” of course would have a Max opening but there are
various combinations of valving and intake designs that tend to restrict
flows in “normal” engines.

This is apparently the problem with current F1 engine at 18,000 rpm.
There
just isn’t enough time to fill the cylinder to rev any higher. Something
to
do with the speed of sound (where’s my Beemans ?). They all want to lift
the limit of ten cylinders to go to 12s, 14s or 16s to get smaller
cylinder
displacement. Apparently the ideal cylinder size is somewhere below 300
cc.
Honda was running 24,000 rpm with 25 cc cylinders in the early sixties.
Where does that leave the XK with up to 700cc ?

There are methods that will slightly enhance
the input speeds. This type of “tuned input” enhancement is usually high
band conscious and not well suited for road car engines requiring a wide
range of RPM. There are velocity stacks and manifold designs that have
been avail for this purpose. But each time you get something at one end
you are apt to loose something at another…

Porsche and others (Mercedes in 1955) have used variable length velocity
stacks
to get around a fixed limitation. The longer the tract, the lower the VE
peak
and the sharper the slope falling off at high speed. Jaguar worked this
out
on the D Type out to 32 inch pipes on the Lucas FI in late 50’s. Most
new> versions involve several sets of throttle plates but my favorite is the
rotating drum intake.

Paul Saltwick


End of XK-engine-digest V1 #132