Engine Analyzer Pro Jaguar v12 5.3 HE Engine

(Brendan McNamara) #1

Been trying to model the V12 engine in Engine Analyzer Pro software. A lot of fun when trying “what if” scenarios. The best results I could get from a normally aspirated 5.3 HE engine is attached. This is theoretical of course and uses intake flow figures from Mark Eaton’s published research on the forum and valve sizes that have been also published here. One of the fun features of the software is that it give you an analysis that gives you some idea of where you are going wrong and then makes suggestions. I used the some intake cam duration numbers from Roger Bywater and the program kept asking for less intake duration and the results improved.

A couple of red flags in the analysis report - knock index very high at 11:1 compression, VE over 100 percent above 5000 rpm. Mechanical Efficiency very low but i dont know how that can be improved with this design. Also mentions possible improvements which are easy to try.

I don’t have very accurate figures for valve weights and valve spring pressures which I will keep trying to find. Anyway thought this might be of interest if not entirely realistic.

(Brendan McNamara) #2

Analysis Report for Mild Street Engine with Desired HP Peak at 6500 RPM

Maximum Exhaust System Backpressure ‘Exh Pres’ is 0 PSI.
This is low for a street vehicle with a full exhaust
system. This is simulating either an extremely free flowing exhaust
system or open headers or open exhaust manifolds. This may be
illegally loud for street operation.

Typical ranges of Exhaust System Backpressure are listed on page
32 in the User's Manual.  You can lower the Back pressure by
increasing CFM Rating in the Exhaust Specs menu or specifying 
Open Headers.  Lowering the CFM Rating will simulate a quieter,
more restrictive exhaust system.  Most dyno tests are done with
Open Headers, which are simulated by selecting Open Headers.

Maximum Fuel Flow ‘Fuel Flow’ is 226.65 lbs/hr GAS.
This is equal to 38.8 gallons per hour of fuel flow.
For an injected engine with one injector per cylinder, you will require
at least 19 lbs/hr injectors.

Fuel Flow will only change if air flow changes or you select a
different type of fuel.  The Engine Analyzer Pro assumes 12.5:1
A/F for gasoline and 5:1 for alcohol (methanol) for all
conditions.  You can not richen or lean out the fuel mixture.

Mechanical Efficiency ‘Mech Eff’ is 76.3 %
at the current Peak HP RPM of 6500 RPM.
This is Very low and represents a real power loss in this
engine’s current operating range. This can be improved by paying
close attention to details in the Short Block Specs menu.

Mechanical Efficiency can be improved by:
 - Reducing piston skirt size or piston ring tension
 - Minimizing 'power robbing' accessories
 - Reducing crankcase windage
 - Reducing stroke
 - Reducing valve spring loads
 - Reducing the engine's operating RPM range

The Intake Valve Mach # ‘MACH #’ is .304
at your DESIRED HP PEAK RPM of 6500 RPM.
This is low and indicates perhaps too much intake cam duration.

MACH # is the BEST INDICATOR of the usable RPM range of this
engine with the current cam & head specs.  Air flow and performance
drop rapidly (the engine 'runs out of breath') when the MACH # goes
over approximately .55 for low RPM engines or .45 for high RPM

MACH # is explained on page 53 in the User's Manual.  You can
lower the MACH # by specifying larger VALVE DIAMETER, VALVE FLOW
COEF, or higher CFMs in the Intake Flow Table in the Head Specs menu,
or larger Intake Duration .050'' and MAX LOBE LIFT in the Cam/Valve
Train menu.  MACH # is also affected by Runner Diameter and Runner Flow
FLOW COEF in the Intake Specs menu, but to a lesser extent.

The Average Piston Speed ‘PSN SP’ is 2990 ft/min
at your DESIRED HP PEAK RPM of 6500 RPM.
This is somewhat high, requiring strong, light reciprocating parts.

The Maximum Average Piston Speed ‘PSN SP’ is 2990 ft/min
at the Performance Calculations Maximum RPM of 6500 RPM.
This is somewhat high (if you want to run this entire speed range),
requiring light, high strength reciprocating components.

A mild street engine should limit PSN SP to a range of 2500-3000 ft/min
with production quality rods. To run at 2750 ft/min or higher, you will
need ‘better than production’ reciprocating components (connecting rods
& bolts, pistons, etc.).

PSN SP (average piston speed in ft/min) and PSN GS (peak piston Gs)
are indicators of how severely you are stressing the engine's
rotating components.  To lower PSN SP and PSN GS, you must shorten
the piston STROKE or design the engine for a lower RPM range.
See pages 53, 54 and 160 in the manual.

Maintaining low PSN SP and PSN GS are critical for ‘keeping the engine

Based on ‘Simple Rules of Thumb’, good Inertia tuning should occur at 5300 RPM,
which is somewhat lower than your Desired HP Peak RPM of 6500 RPM.
This RPM is about where the torque peak should occur and should pro-
duce good peak torque. You may want to try shorter and/or larger diameter
intake runners to gain Peak HP, but likely losing some Peak Torque.

Maximum Knock Index is 2.9 which indicates detonation
(spark knock, ping, etc.) is Very likely to occur.
You should try a higher Octane fuel, lower Compression Ratio, to
reduce the possibility of detonation. You can also try specifying
a spark curve with less advance which will likely hurt performance, but
allow this engine to safely operate with a Knock Index less than 2.

You can reduce the likelihood of detonation, by increasing FUEL
OCTANE or DEW POINT (humidity), or reducing INTAKE AIR TEMP or
reducing COMPRESSION RATIO in the BASE ENGINE menu.  Also, anything
which reduces performance, or shifts the performance curve to a
higher RPM range will also reduce the likelihood of detonation.  You
can also specify a spark curve with less spark retard than what the
engine is currently running.  See Spark Advnc in the results.

Retarding Spark Advnc is not necessarily a 'bad thing'.  The best
performance for a particular RPM range and FUEL OCTANE may come with
retarded spark.  Just be sure to retard spark in the actual engine
to avoid detonation which will cause engine damage.

Also, retarding the spark curve usually increases exhaust temperatures,
which can damage exhaust valves, turbo turbines, etc.

The % Exhaust to Intake Flow Capacity ‘VALVE EXH/INT %’ is 64.8 %.
This is somewhat low, and indicates you could improve performance
by improving exhaust valve flow and exhaust cam profile. The most
common ‘rule of thumb’ is to design for around 75% EXH/INT flow

To increase VALVE EXH/INT %:
   - Increase the EXHAUST VALVE DIAMETER and/or VALVE FLOW COEF and/or
     CFM in the Exhaust Flow Table in the Head Specs menu.
   - Increase the Exhaust Duration .050'', Max Lobe Lift and/or ROCKER
     ARM RATIO in the CAM/VALVE TRAIN menu
You can reduce VALVE EXH/INT % by changing other specs, but that may
also reduce performance.

End of Analysis Report

Yes it was modelled with open headers.

(Brendan McNamara) #3

(ronbros) #4

interesting information, how much would translate into an exceptable street performance car,Donno!

but most of the PreHE V12 Jag experienced engine builders , was increase stroke as much as your money would allow! my engine done 25yrs ago is a 5.3L, at the time i realized stroke was almost a JOKE,to short,), cost of parts back then was to much for me.

seems the factory rods are very robust, just need cleaning up ,standard performance engine practices.

over size valves are done per standard procedures, (my valves are inlet 3mm OS, exhaust 2mm OS. port/polish pretty much standard procedure.

that seems to be different than your results,BUT runs great with custom cams by CRANE cams co.
valves lightened to my preference , and springs NEW factory stock shimmed .080 thou, i’m not looking for extreme RPM, but mid range torque is great,(street car). it will run out to 6500, before HP drop off, peak torque around 4100/4200rpm.

plus other mods.


(Kyle Kelly) #5

What I am taking from this is that the H.E. Heads would benefit most from increased air velocity and runners tuned shorter. Though I’m unsure if this is decidedly by a specified 6500rpm peak. Also, if the engine was run on higher octane, say race fuel or methanol, that the ignition could be significantly advanced. 466hp at 6500rpm seems really good for the H.E. Heads and I would certainly be happy with another 166hp.

Perhaps I should ask I have correctly interpreted the information: shorter duration intake cams, zero exhaust back pressure, stock heads at 11:1 ends up with 466hp at 6500rpm with room to improve with shorter intake runners, tuned header lengths, and more compression for us with non-US cars

I would be curious to see it modelled with correct exhaust back pressure and the 12.5:1 compression. I wonder if it would change things significantly, I can hardly imagine an exhaust setup to rob 160+hp.

(Matt Furness) #6

A mild street engine should limit PSN SP to a range of 2500-3000 ft/min
with production quality rods. To run at 2750 ft/min or higher, you will
need ‘better than production’ reciprocating components (connecting rods
& bolts, pistons, etc.).
Interesting that the Jaguar Engineers thought that a piston speed of 3820ft/min was an acceptable limiting speed based on their experiences with the XK engine. On this basis the design max speed of the V12 was 8330rpm…so obviously the rotating components were of good/superior quality!!

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(ronbros) #7

if you can make an HE head Jag V12 make 466HP you would be unbeliveble !!

many people have tried and most are lucky to get 350 flywheel HP, but a 6.7/7.0L would be possible, but go for it ,would make interesting read with some pix!

(ronbros) #8

Matt, its not the internal rotating components that limit V12 , the heads are just not designed for hi rpm, the HE head was developed for fuel MPG and emission control, never for performance.

most HEs run out of useable power at around 4500rpm, the Pre engines up around 6000/6500rpm!
both have to do with cylinder head air flow, both are different tho!

NOW for anyone in todays engineering , the BEST way would be to use forced induction system , and pressurize the inlet manifold , quick thought, if you could have 15PSI/ or 1 bar manifold pressure , HorsePower would go up 100%, like 600+, (OK in the real world it dont quite make it) but driving would be fun!!
also 7000+ 8000rpm very few people drive around at!

the engines that bring a smile make a lot of torque at a usable RPM, like passing or away from a stop light!

(ronbros) #9

Dark world ,again its not so much air velocity, ITS AIR VOLUME, and that is where turbocharging would come in, LOTS OF AIR, with the correct volume fuel.
also any forced induction may OR MAY NOT requier lower compression, that would be where a standalone ECU doing the tuning , and the best fuel you could buy!

by the way bring money lots of it!

(ronbros) #10

and you could always run NitroMethane fuel , for an additional 1000+HP.

(Kirbert - author of the Book, former owner of an '83 XJ-S H.E.) #11

A naturally aspirated engine is fundamentally limited by airflow through the valves. If you enlarge the displacement without addressing the valves, you’ll typically produce about the same HP but at a lower RPM.

IMHO, you really need more than 3/8" valve lift. Neither duration nor valve size is as important as getting that thing a long ways open. But on the H.E. there’s a special problem in that opening the exhaust valve more wouldn’t help any because of the way the valve is pocketed. I would think you’d have to get the valve to open a half inch or more and modify the combustion chamber a bit to improve flow through that exhaust valve.

(ronbros) #12

kirby what you say close to what i said !

torque is what is enjoyable and fun to drive , displacement increase gives more torque, and great for street driving!

i have driven many cars that are overcammed ,and true at some very hi rpm they finally start to go!

BUT by then i’m gone and so fast you have to slow for everyone to catch up!
simply race cars are for racing ,and hi torque is for street, ENTER! forced induction!!!


Did the Jaguar XKR-15 make 450hp with HE heads?

(ronbros) #14

longJohn you talking XKR or XJR-15??

i dont really believe the V12 in XJR15 at only 6L would make 450hp with the heads that pix have!

beautiful car tho!!, i’m still privy to the XJ220 car (not the engine sadly).

(Robin O'Connor) #15

XJR8 produced this;


Ron yes XKR-15 450hp.

(ronbros) #17

john , jag XKR use a 4.2L V8, no 6.0L V12 ! and NO V8s had HE type heads!

specs say 400HP at the flywheel, be around 350hp at wheels!


Ron sorry XJR-15 not XKR-15. Check it out.

1 Like
(ronbros) #19

OK got it now, thats what i thought !

never less a great car , when spending that kind of money it better be great!!

i’m quite sure if i had unlimited money i could make a 6.0L Jag V12 make 450hp, bottom end of 6.0 is more than up to it ,even 500HP , as always its the top end that is the limiting factor!

as you know me by now, i’d just force FEED the sucker and be done with it, lookin at 750/800 easy!
but i would design the piston& rods & heads to my preference!

(Robin O'Connor) #20

Going back a few years there was an XJS in Aus that was twin turbo and reputedly putting out <>1000hp.
One of the Aussie listers might have more details?