[xj] Dyno run 1984 XJ6 VdP, 4.2L XK engine {Scanned}

XJ
1

I recently organized and ran a San Diego Jaguar Club event at a local
performance shop that has a dynamometer. We had 11 cars including a 1956
Ford Thunderbird, a 1984 Ferrari and 9 Jaguars including my 1969 E-Type and
1984 XJ6 VdP. Both of my cars are equipped with their original matching
numbers 4.2L XK engines. These cars of course are very different even
though the engines have the same displacement: the compression ratios are
different, the E-Type has dual Zenith Stromberg while the XJ6 VdP is EFI
equipped, the E-Type has a stock manual 4 speed while the VdP has the BW66
automatic transmission and the VdP has a lot of emissions control equipment
(AIR pump, catalytic converters, vacuum systems, etc).

In my opinion both of these cars were running good that day although the
E-Type was running particularly well. Here are the numbers as they were
run on the dyno up to red line (5,000 RPM):

1984 XJ6 VdP, 4.2L EFI,
Max Horsepower STD 100.2
Max Torque STD 152.3 ft-lbs
Speeds shown on the chart (while in 2nd gear, automatic transmission)
57-88.4 MPH
Air/Fuel Ratio held pretty constant from 3,200-5,000 RPM and ranged from
13.2 to 11.5

I removed and replaced this cylinder head a few years ago for a burnt #1
exhaust valve. I recently did a compression check. I thought the engine
was running OK but not great, and this shop agreed. This is a stock engine
with 145K miles on it. The torque was 152.3 ft-lbs at about 3,200 RPMs,
dropped off in a linear fashion all the way to red line where it ended up at
about 80 ft-lbs at red line. The HP was about 95 at 3,200 RPMs and then
increased slightly up until maximum (100.2) at 3,800 RPMs where it decreased
until 80 HP at red line. This verified what I feel in the car as much less
acceleration than the E-Type and a distinct lack of torque/HP approaching
redline. The owner and technicians said this engine was pinging and
recommended that I look at the timing and consider retarding the timing a
bit. I usually use 91 octane during the summer months to minimize pinging
under loads.

Here is the comparison numbers from my E-Type

1969 E-Type
Max Horsepower STD 149.1
Max Torque STD 207.2 ft-lbs
Speeds shown on the chart (while in 4th gear) 40-101.2 MPH
Air/Fuel Ratio held pretty constant from 2,000-5,000 RPM and ranged from
12.6 to 13.5

I recently did a valve clearance check (they were good), compression check
(good strong numbers), replaced the plugs, points, rotor, cap, condenser and
wires. I thought the engine was running very good and this shop agreed.
This is a stock engine with at least 80K miles on it (but probably a lot
more). The torque at the low end jumped right up to 200 ft-lbs at about
2,200 RPMs, peaked at 3,000 RPMs started to drop off at 3,600 RPMs and then
ended up at 150 ft-lbs at red line. The HP was linear starting at 70 HP at
about 2,000 RPMs and increased to just shy of 1150 HP up until about 4,200
RPMs where it held pretty much constant until red line. This verified what
I feel in the car as a lot of low end torque, very smooth and spirited
acceleration to red line in either 2nd, 3rd and 4th gear when I try that.
The owner and technicians said this engine was running really well,
particularly the ZSs and they recommended that I “DON’T TOUCH A THING”.

I am interested in an assessment of these two stock engines and how they
compare to other stock XK engines that have been run on a dyno. I guess I
didn’t expect to see such a big difference in the HP and torque numbers, but
this is the first time I have run any of my cars on a dyno and didn’t know
what to expect. I did this because I have read a wide range of numbers for
HP and torque for these cars in various books and marketing brochures and
wondered what the real numbers were. Now I know. I am still working on the
V-12 in my wife’s 1990 XJ-S and plan to run that on the dyno as soon as I
get it back on the road again later this month.

I can scan the charts and put them on Jag Lovers if anyone is interested in
seeing the plots.

Regards,

Paul M. Novak

1990 XJ-S Classic Collection convertible
1984 XJ6 Vanden Plas
1969 E-Type Fixed Head Coupe
1957 MK VIII Saloon
Ramona, CA
@Paul_M_Novak1===================================================
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2

Interesting results Paul. Does the XJ6 have clear cats? What about the
intake side – is the filter clean, or did you remove the front of the filter
can? It seems to me that there’s just not enough fuel getting in, since the
mixture is similar to the E’s. What’s the compression like (maybe you gave us
that previously)?–
Alex
79xj6L SII (BRG + wires)
86xj6 SIII (Black)
61 Sprite MkII (Red)
Menlo Park, Calif.

“Paul M. Novak” wrote:

I recently organized and ran a San Diego Jaguar Club event at a local
performance shop that has a dynamometer. We had 11 cars including a 1956
Ford Thunderbird, a 1984 Ferrari and 9 Jaguars including my 1969 E-Type and
1984 XJ6 VdP. Both of my cars are equipped with their original matching
numbers 4.2L XK engines. These cars of course are very different even
though the engines have the same displacement: the compression ratios are
different, the E-Type has dual Zenith Stromberg while the XJ6 VdP is EFI
equipped, the E-Type has a stock manual 4 speed while the VdP has the BW66
automatic transmission and the VdP has a lot of emissions control equipment
(AIR pump, catalytic converters, vacuum systems, etc).

In my opinion both of these cars were running good that day although the
E-Type was running particularly well. Here are the numbers as they were
run on the dyno up to red line (5,000 RPM):

1984 XJ6 VdP, 4.2L EFI,
Max Horsepower STD 100.2
Max Torque STD 152.3 ft-lbs
Speeds shown on the chart (while in 2nd gear, automatic transmission)
57-88.4 MPH
Air/Fuel Ratio held pretty constant from 3,200-5,000 RPM and ranged from
13.2 to 11.5
[clip]

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3

To me the sheer numbers indicate two engines well off peak power and
torque, Paul. The 84 is positively a lame duck…:slight_smile:

The reason for this may of course be general wear, but I also suspect
that both engines are running off somewhat wrong mixture. The “ideal”
fuel/air mix, Lambda, is after all 14,7, and even if fatter mixture
theoretically should yield more max power it may be a factor?

While the power/torque curves are reasonbably matching expectations the
actual yields are in my view considerably down, particularely on the 84.
To me that indicates some breathing difficulties, including possibly
exhaust restrictions, but using higher octane for more optimum ignition
settings may be beneficial? But, apart from milage, there may be other
issues…

That engines are running OK doesn’t necessarily indicate that they are
at peak performance. During ordinary driving we use but a fraction of
the HP and torque available. And we compensate loss of power by just
unconsciously pushing more on the pedal. After all; we are aiming to
maintain some specific speed, or whatever, rather than watching the
percentage of available power we use. That the E-type feels livlier is
no wonder, with more power in a lighter car, but there may also be other
factors involved - it is a sports car with different characteristics in
the drive train and engine set-up…

FWIW; I’d reckon the E-type should put up closer to 170 - 180 hp and the
xj should push at least 150 or more given age and emission devices.
Arguably this is what we may expect in power loss as a engines ages -
but I think not…:slight_smile:

Frank
xj6 85 Sov Europe (UK/NZ)

Paul M. Novak wrote:>In my opinion both of these cars were running good that day although the

E-Type was running particularly well. Here are the numbers as they were
run on the dyno up to red line (5,000 RPM):

1984 XJ6 VdP, 4.2L EFI,
Max Horsepower STD 100.2
Max Torque STD 152.3 ft-lbs
Speeds shown on the chart (while in 2nd gear, automatic transmission)
57-88.4 MPH
Air/Fuel Ratio held pretty constant from 3,200-5,000 RPM and ranged from
13.2 to 11.5

I removed and replaced this cylinder head a few years ago for a burnt #1
exhaust valve. I recently did a compression check. I thought the engine
was running OK but not great, and this shop agreed. This is a stock engine
with 145K miles on it. The torque was 152.3 ft-lbs at about 3,200 RPMs,
dropped off in a linear fashion all the way to red line where it ended up at
about 80 ft-lbs at red line. The HP was about 95 at 3,200 RPMs and then
increased slightly up until maximum (100.2) at 3,800 RPMs where it decreased
until 80 HP at red line. This verified what I feel in the car as much less
acceleration than the E-Type and a distinct lack of torque/HP approaching
redline. The owner and technicians said this engine was pinging and
recommended that I look at the timing and consider retarding the timing a
bit. I usually use 91 octane during the summer months to minimize pinging
under loads.

Here is the comparison numbers from my E-Type

1969 E-Type
Max Horsepower STD 149.1
Max Torque STD 207.2 ft-lbs
Speeds shown on the chart (while in 4th gear) 40-101.2 MPH
Air/Fuel Ratio held pretty constant from 2,000-5,000 RPM and ranged from
12.6 to 13.5

I recently did a valve clearance check (they were good), compression check
(good strong numbers), replaced the plugs, points, rotor, cap, condenser and
wires. I thought the engine was running very good and this shop agreed.
This is a stock engine with at least 80K miles on it (but probably a lot
more). The torque at the low end jumped right up to 200 ft-lbs at about
2,200 RPMs, peaked at 3,000 RPMs started to drop off at 3,600 RPMs and then
ended up at 150 ft-lbs at red line. The HP was linear starting at 70 HP at
about 2,000 RPMs and increased to just shy of 1150 HP up until about 4,200
RPMs where it held pretty much constant until red line. This verified what
I feel in the car as a lot of low end torque, very smooth and spirited
acceleration to red line in either 2nd, 3rd and 4th gear when I try that.
The owner and technicians said this engine was running really well,
particularly the ZSs and they recommended that I “DON’T TOUCH A THING”.

I am interested in an assessment of these two stock engines and how they
compare to other stock XK engines that have been run on a dyno. I guess I
didn’t expect to see such a big difference in the HP and torque numbers, but
this is the first time I have run any of my cars on a dyno and didn’t know
what to expect. I did this because I have read a wide range of numbers for
HP and torque for these cars in various books and marketing brochures and
wondered what the real numbers were.

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4

Pauls’ numbers are the result of rear wheel horsepower measurement. We
normally think in terms of flywheel horsepower. Rear wheel horsepower will
never match flywheel horsepower.

As a rule of thumb, the parasitic loss from the drivetrain will sap about
25% -30% of the SAE net flywheel horsepower. The USA Ser III 4.2 was rated
at 170 SAE net horsepower and the Ser II E-type rated at 171 SAE net, if I
recall correctly.

Doing the mathematics I think this illustrates how much power an old BW66
can soak up :-). And, using this formula, FWIW, Paul’s E-type is in fine
fettle !

Doug Dwyer
Longview, Washington USA
1987 Ser III XJ6
1988 XJS V12From: “Frank Andersen” franksue@xtra.co.nz

To me the sheer numbers indicate two engines well off peak power and
torque, Paul. The 84 is positively a lame duck…:slight_smile:

FWIW; I’d reckon the E-type should put up closer to 170 - 180 hp and the
xj should push at least 150 or more given age and emission devices.
Arguably this is what we may expect in power loss as a engines ages -
but I think not…:slight_smile:

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5

In reply to a message from Doug Dwyer sent Thu 7 Jul 2005:

Wow, I knew Jaguar had fudged on the ‘‘official’’ BHP rating
of the XK engines when I saw it online somewhere, but to be
off by almost a HUNDRED HP? When I saw it, it said BHP was
265 or something close to that. And with the gas mileage
that these things get (mine gets 17-18 city, 19-20 hwy
depending on brand of gas) I would have thought they had a
lot more HP. The torque does not surprise me, though. Still,
it is no wonder why people lump, and no big surprise that I
can’t get Kitty to go up a hill at any reasonable speed
without mashing the gas. Well, I suppose that I will be
joining the Lump club when my engine dies, I think Kitty
would be happier with something closer to 300-400 hp at the
rear wheels. It’s my car so I can do it if I want. The
conversion would pay for itself given how much jag vs chevy
parts are.
Chris–
SOLENT BLUE IS PEOPLE! SOLENT BLUE IS PEOPLE!
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
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6

The original claim for the E Type triple carb, 9:1 compression ratio was
265 gross SAE horsepower. That’s very different from the later SAE net
HP, and the standards changed in 1973 I believe. That was when things
like some of the 8.2 litre Cadillacs went from something like a claimed
500 hp to 235 even though the engine didn’t change, just the rating
system did.

An triple carb E type in good condition will produce about 180hp at the
rear wheels. The fuel injected emission 4.2 in the XJ’s was rated at
176hp at the flywheel, not the rear wheels, and it also has a 7.8:1
compression ratio, which reduces power. The European cars were rated at
205 hp, again at the flywheel.

Craig
64 OTS

Chris Diamond wrote:>In reply to a message from Doug Dwyer sent Thu 7 Jul 2005:

Wow, I knew Jaguar had fudged on the ‘‘official’’ BHP rating
of the XK engines when I saw it online somewhere, but to be
off by almost a HUNDRED HP? When I saw it, it said BHP was
265 or something close to that.

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7

Wow, I knew Jaguar had fudged on the ‘‘official’’ BHP rating
of the XK engines when I saw it online somewhere, but to be
off by almost a HUNDRED HP? When I saw it, it said BHP was
265 or something close to that.

The old tri-carb 3.8 and 4.2 engines of the 60’s were rated at 265 SAE
gross horsepower. The old gross measurement system was very
misleading…and virtually all manufacturers took some liberties,
including Jaguar. I’ve heard from people in-the-know that the 265 hp rating
was exaggerated by 25 or so. Remember, too, the XK engine was made in many
configurtions and states of tune.

Later the car builders were compelled (by USA legislation, I think) to use
the SAE net measurement system. Under the method the measurement was taken
with engine accesories (water pump, alternator, air cleaner, emissions
equipment, etc) installed and with the exhaust in place. This is a close
cousin to the “DIN” method used by the Germans and some others for quite a
long time. Anyhow, in round numbers, SAE gross minus 25% would generally get
you close to the SAE net measurement.

Paul’s dyno test measures rear wheel horsepower, a horse of another color
yet. Rear wheel horspower accounts for losses through the transmission,
driveline, and differential. Subtract another 25% or so.

And with the gas mileage
that these things get (mine gets 17-18 city, 19-20 hwy
depending on brand of gas) I would have thought they had a
lot more HP.

Remeber that the USA 4.2 fuel injector engine has 35 fewer horsepower than
the “Euro” variant…

The torque does not surprise me, though. Still,
it is no wonder why people lump, and no big surprise that I
can’t get Kitty to go up a hill at any reasonable speed
without mashing the gas.

Right. The 4000 pound curb weight and 2.88 axle ratio are also a big part of
that sluggishness.

Well, I suppose that I will be
joining the Lump club when my engine dies,

Off with your head !

I think Kitty
would be happier with something closer to 300-400 hp at the
rear wheels.

No doubt true :-). The only way to improve these cars is to add more
power…everything is is nearly perfect as-is.

It’s my car so I can do it if I want. The
conversion would pay for itself given how much jag vs chevy
parts are.

Well, lumping to gain power makes perfectly good sense to me. To lump a XJ6
in hopes of saving money, well, it just doesn’t wash. If your XK engine
dies, replace it with a reman unit for $3500 and you’re good to go. I’ve
have seen many lumped Jags. I’ll wager a week’s pay that the really, really
nicely executed conversions (fuel injection, sanitary installation…not a
hatchet job) cost at least $3500, if not more.

Cheers
Doug DwyerFrom: “Chris Diamond” flak_monkey@comcast.net

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8

Not surprisingly, there were strong opinions on my dyno results and they
varied like night and day. One email included the comment that “The 84 is
positively a lame duck”. Others on and off list, including professionals in
the business indicated my numbers were in the range of what was expected
since this was a power at the rear wheels test.

I took my cars to a shop with a dynamometer to find out the truth on how my
cars perform. I now have that truth. I did not want to just quote a number
some of the erroneous marketing source or shoot from the hip. I set this
up at a local shop, the runs were $50 US each. Surely this is well within
many a listers budget. It was a lot of fun to see those cars all run on the
dyno.

In G*d we trust, everyone else please send the data (from your Jaguar on a
dynamometer). I believe we need some more data points on this matter
before the “lame duck” verdict is read.

BTW, I have an arrangement with several shops where I will be getting a
kickback on every Jaguar that shows up in the next 30 days (just kidding of
course).

Regards,

Paul M. Novak

1990 XJ-S Classic Collection convertible
1984 XJ6 Vanden Plas
1969 E-Type Fixed Head Coupe
1957 MK VIII Saloon
Ramona, CA
@Paul_M_Novak1===================================================
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9

In reply to a message from Paul M. Novak sent Fri 8 Jul 2005:

This is more than depressing. I feel like I have been lied
to. Somebody told me that the xk engine would make the rice
boys cry, and now I think I disagree. Yes, I will lump with
a 300-400 odd hp 350 and appropriate manual transmission. My
dad said he would lump the car for me if I got a full
scholarship (I go to a $27k a year art college) so I think
it is fair. I love this car, but it is so sluggish.
Chris

PS I really think there is something wrong with that dyno
reading, but something inside tells me there isn’t. So sad…–
SOLENT BLUE IS PEOPLE! SOLENT BLUE IS PEOPLE!
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
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10

Hank,

Thank you for your request.  It was right on the mark.  I was hoping my

original email would further the discussion and knowledge about our cars. I
will reply to the list when the dyno charts are posted. Perhaps others will
add to the knowledge and get their cars tested as well.

Regards,

Paul M. Novak

1990 XJ-S Classic Collection convertible
1984 XJ6 Vanden Plas
1969 E-Type Fixed Head Coupe
1957 MK VIII Saloon
Ramona, CA
@Paul_M_Novak1----- Original Message -----
From: Jaghpo@aol.com
To: @Paul_M_Novak1 ; xj@jag-lovers.org
Sent: Thursday, July 07, 2005 7:45 PM
Subject: Re: [xj] Dyno run 1984 XJ6 VdP, 4.2L XK engine {Scanned}

Paul,

Your test results are very interesting food for thought and discussion. I
think that a number of us would really appreciate seeing the dyno charts, if
you would be so kind as to post them and notify us when it happens.

Thanks,
Hank
'84 XJ6 SIII, '84 XJ6 VDP

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11

This is more than depressing. I feel like I have been lied
to. Somebody told me that the xk engine would make the rice
boys cry, and now I think I disagree.

Heh heh. They weren’t quite up to speed. Some of those rice machines will
really move…

Yes, I will lump with
a 300-400 odd hp 350 and appropriate manual transmission. My
dad said he would lump the car for me if I got a full
scholarship (I go to a $27k a year art college) so I think
it is fair.

Hard to pass up that deal…

I love this car, but it is so sluggish.

Stately acceleration, Chris. Stately. Actually, seek out a V12 Ser
III…they move long pretty well :slight_smile:

PS I really think there is something wrong with that dyno
reading, but something inside tells me there isn’t. So sad…

Nothing sad about it, Chris. This is why manufacturers don’t advertise rear
wheel horsepower. Everyone would be so disappointed :slight_smile:

Doug DwyerFrom: “Chris Diamond” flak_monkey@comcast.net

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12

Chris,

This was the one and only time I have had a dyno run on any of my cars,

so I don’t have anything to compare this to. I believe the numbers are
accurate, although not what I expected.

One of the cars tested that day was a LUMP'd 1984 XJ6 with a Chevy 350.

It delivered 182 HP and 275 ft-lbs of torque. If you are looking for
300-400 HP at the rear wheels, I think you have your work cut out for you
fitting two of those under the bonnet (hood). 

 The only car that day that delivered 300+ HP was a supercharged 2003

XKR SE, at 312 HP. The owner told me he went back after some work and got
339 HP and 400 ft-lbs but I was not there to verify those numbers.

Regards,

Paul M. Novak

1990 XJ-S Classic Collection convertible
1984 XJ6 Vanden Plas
1969 E-Type Fixed Head Coupe
1957 MK VIII Saloon
Ramona, CA
@Paul_M_Novak1----- Original Message -----
From: “Chris Diamond” flak_monkey@comcast.net
To: xj@jag-lovers.org
Sent: Thursday, July 07, 2005 8:16 PM
Subject: Re: [xj] Dyno run 1984 XJ6 VdP, 4.2L XK engine {Scanned}

In reply to a message from Paul M. Novak sent Fri 8 Jul 2005:

This is more than depressing. I feel like I have been lied
to. Somebody told me that the xk engine would make the rice
boys cry, and now I think I disagree. Yes, I will lump with
a 300-400 odd hp 350 and appropriate manual transmission. My
dad said he would lump the car for me if I got a full
scholarship (I go to a $27k a year art college) so I think
it is fair. I love this car, but it is so sluggish.
Chris

PS I really think there is something wrong with that dyno
reading, but something inside tells me there isn’t. So sad…

SOLENT BLUE IS PEOPLE! SOLENT BLUE IS PEOPLE!

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13

Chris: you may want to move to the Lumps list then because they can give
you background information and encouragement for this swap. The Jaguar
is a luxury touring saloon, not a stop-light rocket.
Gregory-----Original Message-----
From: owner-xj@jag-lovers.org [mailto:owner-xj@jag-lovers.org] On Behalf
Of Chris Diamond
Sent: July 7, 2005 8:17 PM
To: xj@jag-lovers.org
Subject: Re: [xj] Dyno run 1984 XJ6 VdP, 4.2L XK engine {Scanned}

In reply to a message from Paul M. Novak sent Fri 8 Jul 2005:

This is more than depressing. I feel like I have been lied
to. Somebody told me that the xk engine would make the rice
boys cry, and now I think I disagree. Yes, I will lump with
a 300-400 odd hp 350 and appropriate manual transmission. My
dad said he would lump the car for me if I got a full
scholarship (I go to a $27k a year art college) so I think
it is fair. I love this car, but it is so sluggish.
Chris

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14

As requested, here is the link to the two print outs from the dynamometer
runs on my 1969 E-Type and 1984 XJ6 VdP both with 4.2L XK engines. Comments
are requested.

http://www.jag-lovers.org/v.htm?1120799059

Regards,

Paul M. Novak

1990 XJ-S Classic Collection convertible
1984 XJ6 Vanden Plas
1969 E-Type Fixed Head Coupe
1957 MK VIII Saloon
Ramona, CA
@Paul_M_Novak1----- Original Message -----
From: “Paul M. Novak” <@Paul_M_Novak1>
To: xj@jag-lovers.org
Sent: Wednesday, July 06, 2005 10:37 PM
Subject: [xj] Dyno run 1984 XJ6 VdP, 4.2L XK engine {Scanned}

I recently organized and ran a San Diego Jaguar Club event at a local
performance shop that has a dynamometer. We had 11 cars including a 1956
Ford Thunderbird, a 1984 Ferrari and 9 Jaguars including my 1969 E-Type
and
1984 XJ6 VdP. Both of my cars are equipped with their original matching
numbers 4.2L XK engines. These cars of course are very different even
though the engines have the same displacement: the compression ratios are
different, the E-Type has dual Zenith Stromberg while the XJ6 VdP is EFI
equipped, the E-Type has a stock manual 4 speed while the VdP has the BW66
automatic transmission and the VdP has a lot of emissions control
equipment
(AIR pump, catalytic converters, vacuum systems, etc).

In my opinion both of these cars were running good that day although the
E-Type was running particularly well. Here are the numbers as they were
run on the dyno up to red line (5,000 RPM):

1984 XJ6 VdP, 4.2L EFI,
Max Horsepower STD 100.2
Max Torque STD 152.3 ft-lbs
Speeds shown on the chart (while in 2nd gear, automatic transmission)
57-88.4 MPH
Air/Fuel Ratio held pretty constant from 3,200-5,000 RPM and ranged from
13.2 to 11.5

I removed and replaced this cylinder head a few years ago for a burnt #1
exhaust valve. I recently did a compression check. I thought the engine
was running OK but not great, and this shop agreed. This is a stock
engine
with 145K miles on it. The torque was 152.3 ft-lbs at about 3,200 RPMs,
dropped off in a linear fashion all the way to red line where it ended up
at
about 80 ft-lbs at red line. The HP was about 95 at 3,200 RPMs and then
increased slightly up until maximum (100.2) at 3,800 RPMs where it
decreased
until 80 HP at red line. This verified what I feel in the car as much
less
acceleration than the E-Type and a distinct lack of torque/HP approaching
redline. The owner and technicians said this engine was pinging and
recommended that I look at the timing and consider retarding the timing a
bit. I usually use 91 octane during the summer months to minimize pinging
under loads.

Here is the comparison numbers from my E-Type

1969 E-Type
Max Horsepower STD 149.1
Max Torque STD 207.2 ft-lbs
Speeds shown on the chart (while in 4th gear) 40-101.2 MPH
Air/Fuel Ratio held pretty constant from 2,000-5,000 RPM and ranged from
12.6 to 13.5

I recently did a valve clearance check (they were good), compression
check
(good strong numbers), replaced the plugs, points, rotor, cap, condenser
and
wires. I thought the engine was running very good and this shop agreed.
This is a stock engine with at least 80K miles on it (but probably a lot
more). The torque at the low end jumped right up to 200 ft-lbs at about
2,200 RPMs, peaked at 3,000 RPMs started to drop off at 3,600 RPMs and
then
ended up at 150 ft-lbs at red line. The HP was linear starting at 70 HP
at
about 2,000 RPMs and increased to just shy of 1150 HP up until about 4,200
RPMs where it held pretty much constant until red line. This verified
what
I feel in the car as a lot of low end torque, very smooth and spirited
acceleration to red line in either 2nd, 3rd and 4th gear when I try that.
The owner and technicians said this engine was running really well,
particularly the ZSs and they recommended that I “DON’T TOUCH A THING”.

I am interested in an assessment of these two stock engines and how they
compare to other stock XK engines that have been run on a dyno. I guess I
didn’t expect to see such a big difference in the HP and torque numbers,
but
this is the first time I have run any of my cars on a dyno and didn’t know
what to expect. I did this because I have read a wide range of numbers
for
HP and torque for these cars in various books and marketing brochures and
wondered what the real numbers were. Now I know. I am still working on
the
V-12 in my wife’s 1990 XJ-S and plan to run that on the dyno as soon as I
get it back on the road again later this month.

I can scan the charts and put them on Jag Lovers if anyone is interested
in
seeing the plots.

Regards,

Paul M. Novak

1990 XJ-S Classic Collection convertible
1984 XJ6 Vanden Plas
1969 E-Type Fixed Head Coupe
1957 MK VIII Saloon
Ramona, CA
@Paul_M_Novak1

===================================================
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15

Alex,

Yes, the dyno results for my two 4.2L XK engine equipped Jaguars were

interesting. I am still trying to understand them. I think most people have
been reading the Jaguar marketing brochures and/or thinking in terms of
flywheel horsepower. Of course what really matters is what is delivered to
the rear wheels and that was what I was looking for. It appears that
those numbers are lower than most people expect (even some of the more
seasoned listers). I hope that more listers test their cars and post their
results for comparison.

I believe that the catalytic converters in the XJ6 are doing just fine.

I had to replace the front one a few years ago. It was probably clogged due
to unburnt fuel from the burnt #1 exhaust valve that I discovered shortly
afterwards. I removed the head and had that professionally reworked.
While the head was off I decoked the engine and replaced every inch of
vacuum hose, put new plugs in, etc. The car has passed two subsequent CA
emissions tests with very low HC and CO numbers, but the NOX numbers are
marginal.

The filter was replaced recently (within the past year) a few months

after the San Diego fires. There was a lot of ash in the air for months
afterwards. I did not remove the front of the filter or the snorkel. This
car was completely stock and original when the dyno test was run. It had
145K miles at the time was warmed up, had 91 Octane gas and was in my
opinion running as good as it ever had for me.

I do believe that it is running lean and it can be made to ping if I use

87 fuel and or driving the car with a heavy load up a hill on a hot day.
This day was hot and the car pinged under the acceleration. I may try
retarding the timing a bit and see if that helps the pinging, but I’m not
sure how much that will help (or hurt) the HP numbers.

The compression numbers from January 2005 were:

1 (155), 2 (150), 3 (155), 4 (152), 5 (155), 6 (152)

The average was 153 PSI and the variance of each cylinder from that
was: 1(+1%), 2 (-2%), 3 (+1% ), 4 (-1%), 5 (+1%), 6 (-1% )

Regards,

Paul M. Novak

1990 XJ-S Classic Collection convertible
1984 XJ6 Vanden Plas
1969 E-Type Fixed Head Coupe
1957 MK VIII Saloon
Ramona, CA
@Paul_M_Novak1----- Original Message -----
From: “Cannara” cannara@attglobal.net
To: xj@jag-lovers.org
Sent: Wednesday, July 06, 2005 11:01 PM
Subject: Re: [xj] Dyno run 1984 XJ6 VdP, 4.2L XK engine {Scanned}

Interesting results Paul. Does the XJ6 have clear cats? What about the
intake side – is the filter clean, or did you remove the front of the
filter
can? It seems to me that there’s just not enough fuel getting in, since
the
mixture is similar to the E’s. What’s the compression like (maybe you
gave us
that previously)?

Alex
79xj6L SII (BRG + wires)
86xj6 SIII (Black)
61 Sprite MkII (Red)
Menlo Park, Calif.

“Paul M. Novak” wrote:

I recently organized and ran a San Diego Jaguar Club event at a local
performance shop that has a dynamometer. We had 11 cars including a
1956

Ford Thunderbird, a 1984 Ferrari and 9 Jaguars including my 1969 E-Type
and

1984 XJ6 VdP. Both of my cars are equipped with their original matching
numbers 4.2L XK engines. These cars of course are very different even
though the engines have the same displacement: the compression ratios
are

different, the E-Type has dual Zenith Stromberg while the XJ6 VdP is EFI
equipped, the E-Type has a stock manual 4 speed while the VdP has the
BW66

automatic transmission and the VdP has a lot of emissions control
equipment

(AIR pump, catalytic converters, vacuum systems, etc).

In my opinion both of these cars were running good that day although the
E-Type was running particularly well. Here are the numbers as they
were

run on the dyno up to red line (5,000 RPM):

1984 XJ6 VdP, 4.2L EFI,
Max Horsepower STD 100.2
Max Torque STD 152.3 ft-lbs
Speeds shown on the chart (while in 2nd gear, automatic transmission)
57-88.4 MPH
Air/Fuel Ratio held pretty constant from 3,200-5,000 RPM and ranged from
13.2 to 11.5
[clip]

===================================================
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16

Frank,

I'm not sure what to think yet.   Lots of opinions on this one.  It the

XJ6 a “lame duck” or is this just verification of what the true HP numbers
at the rear wheels are? I just posted the two dyno runs on Jag-Lovers. I
wonder if other listers have similar dyno runs to post (or are possibly
interested in getting their cars tested)?

Here’s the link: http://www.jag-lovers.org/v.htm?1120799059

Both cars were filled with 91 Octane fuel.  I usually use 87 or 89 in

the XJ6. The E-Type won’t run right with anything less than 91. It will
ping and try to keep running when I shut it down (run on?).

I've been wondering about the Air/Fuel ratio plots myself and I may call

the shop owner again to discuss.

Regards,

Paul M. Novak

1990 XJ-S Classic Collection convertible
1984 XJ6 Vanden Plas
1969 E-Type Fixed Head Coupe
1957 MK VIII Saloon
Ramona, CA
@Paul_M_Novak1----- Original Message -----
From: “Frank Andersen” franksue@xtra.co.nz
To: “Paul M. Novak” <@Paul_M_Novak1>
Cc: xj@jag-lovers.org
Sent: Thursday, July 07, 2005 12:13 AM
Subject: Re: [xj] Dyno run 1984 XJ6 VdP, 4.2L XK engine {Scanned}

To me the sheer numbers indicate two engines well off peak power and
torque, Paul. The 84 is positively a lame duck…:slight_smile:

The reason for this may of course be general wear, but I also suspect
that both engines are running off somewhat wrong mixture. The “ideal”
fuel/air mix, Lambda, is after all 14,7, and even if fatter mixture
theoretically should yield more max power it may be a factor?

While the power/torque curves are reasonbably matching expectations the
actual yields are in my view considerably down, particularely on the 84.
To me that indicates some breathing difficulties, including possibly
exhaust restrictions, but using higher octane for more optimum ignition
settings may be beneficial? But, apart from milage, there may be other
issues…

That engines are running OK doesn’t necessarily indicate that they are
at peak performance. During ordinary driving we use but a fraction of
the HP and torque available. And we compensate loss of power by just
unconsciously pushing more on the pedal. After all; we are aiming to
maintain some specific speed, or whatever, rather than watching the
percentage of available power we use. That the E-type feels livlier is
no wonder, with more power in a lighter car, but there may also be other
factors involved - it is a sports car with different characteristics in
the drive train and engine set-up…

FWIW; I’d reckon the E-type should put up closer to 170 - 180 hp and the
xj should push at least 150 or more given age and emission devices.
Arguably this is what we may expect in power loss as a engines ages -
but I think not…:slight_smile:

Frank
xj6 85 Sov Europe (UK/NZ)

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17

Paul M. Novak wrote:

Frank,

I’m not sure what to think yet. Lots of opinions on this one. It the
XJ6 a “lame duck” or is this just verification of what the true HP numbers
at the rear wheels are? I just posted the two dyno runs on Jag-Lovers. I
wonder if other listers have similar dyno runs to post (or are possibly
interested in getting their cars tested)?

Couldn’t bear the disappointment, Paul…:slight_smile:

I do not doubt the readings, but seriously question any satisfaction
with the xj’s power curve! Having studied the curves; the xj is crap,
while the E-type is only somewhat disappointing…:slight_smile:

The reason for the xj’s very poor performance is not immediately
obvious, but you mentioning a possible exhaust problem is not an
unlikely cause. Seemingly it is not getting, or getting rid of, enough
air. But it may be ordinary wear and tear or some bad adjustments…

To exemplify; using “real” horsepowers taking the Jaguar to 100km/hr in
16 seconds from a standing start requires some 130 hp at the rear wheels

  • averaged over the relevant rev range. And with a slush box when new it
    could do better than that. In fact 13 - 14 seconds was quoted and not
    questioned - giving an average hp of some 150 hp - average. In prime
    condition peak figures of some 170 - 180 hp at the rear wheels on either
    one should be gotten, though likely lower on the US market…

I must be added that peak horspower, even in 5-speed manual, is not
readily and continuously available throughout acceleration. And
certainly not in a 3 speed slush. To some extent peak hp reflects max
speed - aquired over time…:slight_smile:

In short; while the E-type is reasonable - the xj is a “lame duck”…

Frank
xj6 85 Sov Europe (UK/NZ)===================================================
The archives and FAQ will answer many queries on the XJ series…
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18

Chris Diamond wrote:

In reply to a message from Paul M. Novak sent Fri 8 Jul 2005:

This is more than depressing. I feel like I have been lied
to. Somebody told me that the xk engine would make the rice
boys cry, and now I think I disagree. Yes, I will lump with
a 300-400 odd hp 350 and appropriate manual transmission. My
dad said he would lump the car for me if I got a full
scholarship (I go to a $27k a year art college) so I think
it is fair. I love this car, but it is so sluggish.

Now, Chris, if you want to put the heat on the new rice-cookers from
green lights - why on earth did you buy a 2 ton, 20 year old saloon, it
never can…??? :slight_smile:

Maybe it is sluggish because you ain’t treating it right? And you can
get an idea of the output on it with a couple of quarter-mile runs or
whatever, and do some computations. And then some adjustments. And quite
frankly; lumping it will not solve your complaint - the 300 - 400 hp
ain’t real either, but the drop in value will likely be…:slight_smile:

Frank
xj6 85 Sov Europe (UK/NZ)===================================================
The archives and FAQ will answer many queries on the XJ series…
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19

In reply to a message from Frank Andersen sent Fri 8 Jul 2005:

I always wonder abput the whole lumped Jag thing. I think
I’d buy a pre lumped car, to save all the hard work, but
don’t think I’d lump one, for the reason above.
I am a bit surprised that a lot of Jaguar owners do not
consider modifying their existing engines, I think a twin
turbo XK engine would be a pretty sraightforward thing to
engineer if you didn’t get silly with power levels, and
aftermarket fuel injection is steadily dropping in price.
Two smaller turbos would allow faster spool up, which would
only enhance the XK’s midrange torque.
However, I’d love to mount a centrfugal blower on my series
3, Just a matter of finding the room. Would probably fit on
the exhaust side, above the aircon compressor, but then,
turbos would fit a lot better there…
You could even emulate the intake mods available for the XK
engine locally fairly chaply, and extractors are around.
$3500 is a LOT of engine work!
I am actually fairly happy with my XK, it is no rocket off
the line(not a slug either, will hold it’s own against other
six cylinder sedans), but once moving, a 3-1 downshift can
be positively exciting! I must add I run a LOT more ignition
timing than the factory recommends, and have a non cat
equipped car.
Give me some time, and I will definitely dyno my car, just
to see where I am going with the engine.

Regards, Andrew.–
84 Daimler Soverign 4.2 - daily driver / Dodge ute in bits!
Newcastle, Australia
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20

In reply to a message from Paul M. Novak sent Thu 7 Jul 2005:

Lumps & Luxo-Barge (!?)
Paul, I’ve read all these comments & they are interesting - I
have a few to make myself.
No one mentioned that debilitating 2.88 differential! that
was done to get some fuel milage-which it did do-But it sure
killedacceleration. Put a 4.56 in & you’ll run with the big
dogs. With a 2.88 ratio if you had 800 real horse power &
500 pounds real torque,the differential would fail before
you could whip one of those rice-burning ‘‘tuner’’ cars when
the light turns green.
Now perhaps it’s true that our 3series cars are meant to be
slow moving ''Lux-o-Barges, but then the question is begged:
why do they look like ‘‘fast?’’& why D O H camshafts &
hemispherical cumbustion chambers? Why that great rear end
that the hot rodders love to install on their
non-Lux-o-Barge HOT RODS ? Maybe I call it a ‘‘luxory car’’ so
I don’t have to explain why any (that’s ANY!)rice burner is
faster?
Lastly, as I’ve been on the forum only a few months, all the
terminologys are not familier to me. Why are the American
motor conversions called ‘‘lumps’’ ?
Lastly again, I really appreciate that dyno information you
provided.
Jimmie–
Tennessee Jimmie Hodges86 VP 87 VP88XJ 92Sov 94XJS conv
Edgerton, WI, United States
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