So aren't the heads the limiting factor? It doesn't seem possible that throttle body changes of any sort would have much affect on that >5500 rpm ve curve when they're only at +/- 30% of their max cfm.

I'm all for radiusing the TBs, low restriction filters, 2.5" filter housing inlets with cold air and even that .176 psi boost at 100 mph from ram air setups, but I'm guessing all those combined wouldn't move that top end ve 10%. Gotta be the heads. That's where the horses live.

 

Increasing VE at higher RPM requires more than just head mods. AS RPM increase there is less time to fill the cylinders, so intake and exhaust tuning in conjunction with Cam and head mods is what is required.

The lift in the V12 is quite moderate. Valve lift is 9.5mm so about 23% of the Intake valve diameter, where as an LS1 will lift the valve 25% of the intake valve diameter. This additional peak lift will help higher RPM VE.

BTW Jaguar/TWR managed 450hp from a 6.0L HE V12 in the XJR15. So it can be done. I believe what is more important in a road car is power in the 2500-4500rpm band as most road engines don't see much past 4500rpm except maybe 1st gear.

 

Horsepower/Torque Curve for 1992 Jaguar XJS V12 Coupe cat (model for Europe Germany). Detailed engine characteristics.


they are calculation I derived using the data posted on the Euro/Germany cat version... in the above link


I will do one for the us version that will look even worse as we have less HP


the VE depends on pipe resonance length and width... the system in place was tuned for about 3000 rpm...
79.00 VE and is off by 10 percent when you get to 5000 rpm raising the VE back up
to 79.00 (percent) at 5200 rpm will give you 301 lbs/foot of torque and 301 HP


retuning the intake or flowing it or a cam change or even a timing change could do the trick

 

just read this thread, pistons for the preHE are XJ V12, are different for US ,at 7.8-1, vs UK at 9.1 , i bought new pistons from Welch back 1994,new/old stock.

side by side view was a different shallow bowl in piston,combustion chamber!

i did the usual engine mods ,larger valves, blending bowl/pockets, smoothing ports, Extrude porting inlet manifolds,plenums and runners, had CRANE race cams custom grind, more duration and overlap, slight increase in lift, Nitrided.

over size TBs 1/4" larger, radius inlet side, some thermal coating on cylinder heads, ports /deck surface ,valves,etc.

full open exhaust system , NO cats or resonators, just two 2.5" glas packs, 5" outlet,yup LOUD.

many small mods internal engine, oiling system, cooling system, many i cant remember, 22 years now,(yes ahead of the curve).

BUT times have changed , dont kid yourself you are never gonna be serious competion for these NEW factory HOT RODS, 650/700hp cars, STOCK.

trans. mods, rear gear mods ,and more!

dyno results, i never was satisfied, one time best 325 WHP, average most runs around 315/320 rear wheel horse power, make your own crank HP guess!

my torque peak occured around 4200/4500(cant remember exactly, time marches on), and HP rolled over just around 6500/6700.

engine will rev to 7000+rpm but it aint pulling and a waste of time.

but i go along with the street theory of MAKE TORQUE AND LET HP be what ever it is, i have won more races with early torque, and V12 engines naturally have a long flat torque curve by there very nature.

even if it dont make the torque of a normal V8, it carries it longer in gears before shifts!

 

Nerve beats HP every time.

 

Well said Ron,

My mate had a Commodore with a 380hp LS1 manual, and my 5.3L with stock intakes and 2.5" exhaust was quicker to 100km/h, just. From 100km/h he would pull away

So it depends if your goal is quick out of the blocks or topend speed.

 

We did measure the power of DDS my friend. The car has a fully stock, the German specification, catalysts. The measurements were stopped at 4500 rpm due to the lean of the mixture. Fuel pump needs to be replaced. Cylinder head and intake manifold modified. Fully rounded off from the valve seat to plenium. The outlet port is aligned, flattened.

 

I had a 92 Series III V12 sedan and replaced the downpipes with the European pipes with no catalyst after mine were damaged. I didn't run any numbers, but the "seat of the pants" meter could tell no difference between cats and no cats.

There was no difference in fuel economy either between cats in good shape and no cats.

 

Or take a look at AJ6 Engineering's "plus torque" conversion. I'm a firm believer that low end torque is what matters in everyday driving to make a car quicker. Headline HP is for 1/4 miles runs only.
THE JAGUAR V12 ENGINE / AJ6 Engineering

 

Is the HP at the wheels or corrected for engine? As the torque looks like its corrected for engine.

 

those are right on with the numbers I posted...
so I would think corrected for the engine.....

if not the engine would be about 302hp which would be 15% over the stock at that rpm

 

The graph said 262HP not kW and 382Nm which is why I questioned it

 

.

that torque curve shows an almost flat V12 curve,nice!

very typical for V12 engines, HP is somewhat disappointing tho.

no humps and bumps like many V8s.

sorry i lost my dyno sheets many years ago(along with much Jag V12 info),darn it. moving around to much.

 

yeah I know it is confusing until you go convert the Nm to Ft/lbs
then HP = (RPM * T(ft/lbs) )/5252
so always at 5252 rpm the lbs-feet of torque = the HP
also below 5252 the HP will be less and above it will be greater that the tourque
it's just math...
flat torque... the you get a nice rising HP through the RPM range
on the linear formula of y = xRPM/5252
y intercept of 0 at x =0 and
x at 5252RPM
this is SICK How To: Build Your Own Sheetmetal Engine - Hot Rod Network
a "sheet metal engine" could be applied to a 12 or what ever
I will read through it for the head development...

 

I was wondering why they used SAE and Metric on one graph.

But more importantly 388Nm is 30Nm less than my car had stock.

 

he did state that one of the fuel pumps was bad... and the air/fuel ratio went out of range so they shut down...