Upon reading about the horsepower wars of the 60s it got me thinking

A lot of manufactures would either blatantly lie about their output or simply quote the max power at a ridiculously low rpm (4500rpm)

This brings me to the modern day I will quote a few outputs from the same era as our aj33/34 with similar capacity and comp.

AM - 385hp 7000rpm 11.3 comp
S4 - 340hp 7000rpm 11 comp
Mas - 385hp 7000rpm 11.1 comp
Jag - 300hp 6000rpm 11 comp

As you can see the jag engine is considerable down on hp and rpm but does have a very respectable amount of torque only bettered by the maserati.

Now surely our heads can't be that restrictive ? Surely these could have had a a higher max rpm in order to develop more power .

300hp seems a bit low when in fact we essentially have all the ingredients to develop past the 350hp quite safely.

 

There is a LOT more to the equation than HP, RPM, and compression ratio.

Emissions, fuel economy, driveability, reliability, and cost/complexity are important considerations.

I don't know anything about the S4. The 2007 Maseratti you are citing has the Ferrari F136 dry sump, direct injection motor which I am sure is more costly than the Jag AJ33 motor.

The AM AJ37 is a dry sump variant of the Jag AJ33 with a custom block, heads, intake and exhaust manifolds, crank, cams, pistons, and engine management. With a LOT of extra cost AM was able to squeeze 85 more HP from the AJ33 they started with.

I don't think Jaguar is "detuning" their motors. They are squeezing as much as they can while meeting, fuel economy, emissions, driveability, reliability, and COST. If you are not happy with 300 HP, then for a few more $$ they blow the Aston and Maseratti specs away with the 420 HP SC AJ34 motor, in the XKR with a lower MSRP than either of these competitors.

 

I always understood the advertising HP wars of the 60's relating to 'A' trim HP claims (no load) vs. 'C' trim (full accessories and water pump) claims. In the 80's I remmeber reading in some mags about a bone stock fresh built HiPo 289 barely managing 135 hp to the rear wheels.

Per late model claims, apples to oranges to fairy farts. Electronics and variable cam timing can do wonders to HP claims since most tune to an SAE standard. Then again, maybe the intended use / duty of the Jag motor caused the engineers to tune it more for a flat torque curve vs. being peaky up in the RPM's so it didn't feel like a complete dog in comparison to the XKR. I know my sons 3.9l NA jag based Lincoln LS feels like a total dog compared to my XKR.

 

Oranges to Oranges then .. lets leave out

Direct injection engines (maserati)..
Engines with larger valves/more lift/higher duration (aston)

Now lets explain how an engine with two fewer cylinders, a lower compression rate of 10.5 and is designed for a saloon able to outperform an engine designed for GT.

AJ30 - 240hp redline 6800rpm (80.8hp per 1000cc) 2 fewer cylinders
AJ34 - 300hp redline 6000rpm (71.5hp per 1000cc)

Going off these stats its safe to say that at 300hp the engine is very lazy .

I'm questioning the fact that whether more power could be in fact gained at a higher rpm and whether for some reason the engineers purposely imposed such a low rpm cut off

 

I would still say they built each engine for their intended use and duty along with the limits of technology and understanding of what it takes to make today's fuel turn the wheel.

I think this is an exciting time as engineers understand fluid dynamic and cam dynamics much more than they did ten years ago. Both of those engines are much hotter vs. the 45hp/l venerable 5.0 mustangs then hot 225 hp back in 1988.

 

The reality is that most modern cars would easily get by with an engine that produces 200-300 HP, as most of these cars weight between 3000 and 5000 lbs. (This is a quite sufficient HP to weigh ratio to move the car along.)

If you are old enough, you may recall the early pre-WWII cars weighed 5000+ lbs. and most engines produced <100-125 HP! The cars served their purpose just fine and fuel economy was of no concern at all.
From WWII thru to the early 1960's the cars weighed a little less, but most still tipped the scale at 3500-4000+ lbs., and HP increased gradually to around 250-300. Fuel economy was still an unknown term.
Then in the mid to late 1960's speed and HP became all the rage! Young adults wanted to modify and race their cars for fun.
At this time even the grand touring European cars from Ferrari, Maserati, Lamborghini, Jaguar, etc. were still only just breaking the 300-320 HP mark.
So as the 1960's ended we had this tremendous "HP War" world-wide. Then came the Oil Crisis of the early 1970's. Japanese car makers responded by producing smaller, lighter, and more fuel efficient cars. North America responded with still very heavy, yet pathetically under-powered cars such as the Corvette, Mustang II, AMC Pacer, K-car, et al.
In the 1980's,1990's and 2000's, manufacturers spent more R&D time and money on new technologies, and thus gained more power and increased fuel efficiencies.
In the early 2000's the German manufacturers began another "HP War", but due to increased safety and luxury items, the cars weight's continued to go higher.
Today the very latest technology and the readily available and wanton wealthy upper class, has created a market for cars with ridiculous HP ratings, simply as a status symbol.

I would ask these question of almost any driver of any car: 1.) How many times have you driven your car at the maximum REV's in any gear in order to fully utilize the maximum available rated HP of your car? 2.) What percentage of your car's engines running time has been spent at maximum HP output?

The answer in 99.9% of those asked would be far less than most people would imagine. The truth is, fuel economy, long-term reliability, and current traffic realities, prevent most people from ever getting close to using the fully rated ability of their car on anything more than the occasional rip.

Manufacturers will make anything which people will buy and they can sell for a profit. The fact is most cars, and the people that drive them, do not need more than 300 HP.

 

[QUOTE=JagRag;
The fact is most cars, and the people that drive them, do need more than 300 HP.[/QUOTE]

Surely you meant to write that people "do NOT need more than 300 HP".
And that is so true. The 4.2 naturally aspirated XK provides far more power, acceleration and speed than anyone can legally use - and this 300 HP engined car can get you into trouble very, very quickly. While having the supercharged version of either of the XK engines is without question a feel-good, ego-boosting factor (if one's ego needs boosting), the naturally aspirated engine in the XK provides a beautifully balanced, very fast, more economical and arguably more reliable driving and ownership experience.

 

Power has got me out of probably just as many close shaves than good brakes have.

 

I really think it came down to carefully designed longevity, Ford/Jaguar didn't want the risk of going for the power war. They wanted to turn around the reputation they had.

Purely from a sound perspective, I would love to have 7,200RPM instead of 6,500RPM.

The difference in forces involved in that change is far from linear. :\

 

Pretty good explanation over in Wikipedia about how pre-70's cars in the US were using BHP as their unit of measurement. Very little regulations were in place to enforce accuracy in those days.
The US eventually adopted new SAE rules and ratings similar to those used in European countries, making pre-70's difficult to compare to modern ratings.

Another point I have studied in the past was block castings, and its progression through its life.
Alas, my papers are buried somewhere in storage, but it showed how US auto makers would take a single casting, and make light alterations to accommodate more output through the years. It was interesting to see a small block from the 60's progress from the 200+ Cubic Inch to 350 Cubic Inch displacement with very little alterations to an old block casting other than bore, stroke, and added reinforcement.

You can follow a casting through 10 years of use, and maybe 12 to 13 different outputs (in those days the marquee got altered versions of the same block, to distinguish the performance line form the family sedan)

Even my old Mitsubishi Starion used a 2.6l truck motor, but when turbocharged, they just added internal webbing to the casting to handle the extra 100HP.

7500RPM is relatively simple to achieve. It's called 'Balancing and Blueprinting' your engine. Very common here in the US amongst racers, but an expensive venture as you move to forged and shot-peened components.

 

Yes, balancing is essential for higher RPMs. "Blueprinting" is merely paperwork, writing down all the measurements and clearances and such.
I took a long time assembling a Ford 557 cid, and it happily spins to 7600 RPM and still wants to keep going. Since that's a LOT of metal flying around so fast with a huge stroke, I put a Rev Limiter at 7200. I only get that high under 'special circumstances' though.