Wouldnt you get better throttle resonse by changing gears. A set of 3:55 or 3:91 gears would give you what you want in torque. Not much for to end but our speed limits only 120 km or 73 mph.
If fact an underdrive unit could give you the best or both worlds. $2500 at gear venders

 

A Diesel cant make the same BHP figures a petrol can and die to their design, they make loads of torque. But what good is a torque curve, which is high at the beginning and flattens off quickly?

Just a comparisson:
My daily drive has 145 HP and 185 nm. If I took the same size Diesel in the same car, the car would have 136 HP and 320 nm. What are 9 hp? Enough to outrun the Diesel where all torque comes at 2000 rpm and lets off after that.

Torque and BHP figures say nothing at all by their own. You need a few more figures. Like peak torque at XXX rpm, BHP at XXX rpm and co.

 

SS
Max stock would be more like 320 and that from a 6 litre. Very hard to get 450 from any HE without major mods. The HE head has an inlet valve that is just about level with the head surface, and a special channel to the exhaust valve pocket. (Think of the pocket as a short wide tube with the valve in the closed end and a spark plug poking into the side of the tube.) The flat topped piston forces the mixture down the channel to the exhaust valve pocket, in which is the plug also. This produces squish and a vortex in the pocket and enables an overall very weak mixture, because it is concentrated in the small volume of the pocket, to ignite.

This works brilliantly until about 5 to 5,500 rpm when the exhaust valve cannot flow any more. This is because the width of the pocket with a valve in the end means flow cannot improve as it has to go down the tube and round the valve. If you make the pocket wider you lose the road-speed efficiency and the ability to ignite overall weak mixtures.

The AJ6 stuff transforms the car, it is easily the best bolt on way to improve an HE. It greatly improves both mid range torque, and top end response in the 4,000 to 5,500 range. Transformed my car with only the first two mods, not the manifold trumpets. Mind you the UK spec cars are significantly more lively than the USA ones, anyway.
Greg

 

The way it is here she would have to go to a driving school $$$ since her license doesnt allow her to drive stick even to practice...
I like your intake mod though. Simple and easy way to get a little growl.

 

Diam whachutalkinbout Diesels?

you should rethink modern diesel cars,especially German cars, like BMW D3 Alpina, U Tube tests Vs petrol, and a list of Audi diesel Q7 V12(not so much the 3L diesel).

utube Audi R-10 ,R15,R18 cars.

modern diesel engines have no problem turning 4500-5000RPMs, just like a Jag V12 HE.

i have been to the race tracks, and in USA DIESELs have been banned,against petrol cars, diesel are to fast, use far less fuel and quieter sound!

you have to see, in person, an Audi diesel car blow past a real Porsche race car, porsche screaming at 10,000rpm and the audi only turning 4500rpm using its torque to pass all cars.

your concept of HP vs torque, for instance,

what gets a car from 0-to 60mph faster? torque or HP.

also when driving on the street ,what lets you pass another vehicle quicker, torque or HP?

"HP sells cars,,Torque wins races" Carroll Shelby1965

and an XJS would not stand a chance against a modern diesel car.

Hp has its place on the Autobahn or Bonneville or a hi-speed type track.

but for most street driving a modern diesel car is smooth and quiet,plus better MPG.

 

enough of this for now,

i'm off to the F1 races, its only 15 miles from my house!

drivers think its one of the best tracks for racing there type cars, plus exciting crowds, Austin TX, COTA track.

 

In my comparisson the Diesel version with loads more torque... Nearly twice as much, still only accelerates the same as the equal size nonturbo petrol... Hondas have no torque but still ein races

 

I hesitate to disagree with Ronbros as he has so much knowledge and experience, but I think you are correct, Daim, about the very brief useable torque curve on diesel engines. That is the reason, I had always assumed, for the 7 or 8 speed autos etc etc that are on all the modern diesel engined saloons.

But AFA endurance circuit racing is concerned, the lower fuel consumption of diesels makes them unbeatable by petrol engined cars unless the rules are tweaked to favour petrol engined cars. Le Mans has been won by diesels for ages now.

Super lightweight formula cars are something else though, more akin to motorbikes, with not much need for much torque to get them moving. Thus diesels not required or useful, any more than they would be on a motorbike! A great deal also depends on the circuit layout too; in principle a diesel would be good at Indianapolis, just as in the 1960s gas turbine powered cars cleaned up until they were banned for being too boring to watch because the 'hoovered' round the track almost noiselessly. The lack of throttle response on a turbine was not a problem at Indianapolis because the drivers just pressed the loud pedal a bit earlier as the circuit layout made it predictable.

Greg

 

Greg, I have loads of experience with Volvo (yes, the old people's brand ) and can talk for the brand with the Iron Ore symbol...

The 2.0l diesel and the 2.0l petrol have the same displacement (except 1cm³)and have about the same power (136 hp vs. 145 hp). The diesel has 6 speeds, the petrol 5 speeds. The diesel has LOADS more torque at exactly 320 nm (at 2000 rpm) and the petrol has 185 nm (at 4500 rpm). 0-100 km/h (0-62 mph) is achieved with in 9.4 seconds - no matter if diesel or petrol.

Exceeding 100 km/h, the 2.0l petrol pulls away to achieve a greater top speed (exceeding by 15-20 km/h - depending on what year).

The diesel has, as said, peak torque at 2000 rpm and flatens off after that. The petrol has a very steady incline in torque.

Yes, fuel economy is of course the diesel bonus side (but only since around 15 years since diesels have become hightech lumps with more electronics around it than mechanicals) but compare that to the amount of sh*te that comes out of the exhausts... Coal lumps instead of soot (if you remove all filters, EGR and co). Not mine... Not for me.

That is why I dislike the idea of comparing a V12 Jag with a V12 Audi Q7 Diesel... Refined sports car vs. Communist diesel tank!

Oh, and an EDIT:

What many people forget is, that an equal sized diesel with the same technical details as a petrol, is less powerful and less fuel efficient. Lets say you take a 3.0l V6 petrol engine and a 3.0l V6 diesel engine, chuck two turbos (same size) on each engine and then spec them, you'll still be getting more power (torque and hp) out of the petrol, than the diesel. On top of that, the diesel engine will weigh more (the engine block needs to be thicker, the crank more robust, bigger bearings etc. due to the higher internal forces like pressure and co) and won't be as refined as the petrol. And the power in a turbo petrol can be held longer up high where as it won't do so in a diesel without some kind of help... The petrol will burn cleaner (with two simple 3-way cats) and be cheaper to produce...

 

diam many modern diesels rev to over 5000rpm!

VW TDI maybe more!

my Opel-Isuzu diesel 1.8L turbo doesnt start torque curve till 2250rpm and carries to 4000 no problem, peak torque around 3500. gets 45-50mpg US gallon. NO its not fast,but its novelty, i run it on used vegetable oil(form local Chinese resturant). smells like fried chicken!hehe for free no cost.

i still say you should look at some of German diesel cars BMW as well as AUDI. with an unbiased thinking.

fact M/B built the 1st diesel car to go 200MPH.

most modern diesels are govenor limited to 155mph.

and like greg mentioned LE_MANS HAS been won by diesels for many years, all the time they are limited(each yr) to allow less fuel and more weight penalties, compared to petrol or alcohol(E85) cars, not fair.

a shame we are so far apart in distance ,id like to race your XJS against my XJS(mine is older also). we could then compare a torque race, and top speed(we got some great fast hiways in Texas).

maybe put this airplane engine in the XJS ,only 3000hp , might have traction problems tho! more hehe.

beside make great topic for J/Forums.

 

TO self, make note, full moon is on the rise, conversations will change the attitudes

 

Not disputing Ron's obvious wealth of knowledge, but I think a large factor in diesels mpg advantage is that diesel fuel contains more energy per volume? Diesel being closer to an oil than solvent like gasoline probably doesn't hurt the engines efficiency either.

It seems to me that (in the past anyhow) diesels were engineered more as utilitarian than performance machines, that doesn't mean performance can't be achieved, just that it hasn't been the goal. More ancient history: Cummins, if I remember correctly, ran a diesel car at Indy for several years, I think in the 40's, not saying it was a front runner but it was in the race.

Regarding torque vs hp, I'm not an engineer but as I understand it torque is a rotational force, where hp is a rate of applied force? I may not have worded it accurately but what i'm saying is that they don't measure the same thing. Both are going to vary with rpm, and both will affect performance in different ways.

 

Don't know if you watch the BBCs Top Gear series, but I do recall seeing an episode featuring an automobile with a WWII vintage aircraft engine. Maybe more than one. Not necessarily very practical but very entertaining!

 

This threads really gone of track, but I am so happy to find a fellow bio-man on this forum of all forums, I was called an idiot back in 04 when I statred but now its "can we have some fuel please", god only knows how many litres has passed by these fingers since then.

Back to the old torque vs Hp , they work hand in hand, this is maths gentlemen one is dependant on the other, lets say the more you have of both the better you are. Also the higher you can get both at that magic 5300rpm cross over the quicker you will be! Now how you do that I would really like to know
I will throw this into the ring as well, a lot has being said about how the 6.0litre motor with its longer stroke is so much better then the 5.3 with its more off square or short stroke, I will add studies and tests have been done showing shorter stroked motors produce more torque and HP per volume then their counterparts, maybe just maybe going to max bore with the standard stroke is a better way to go on these motors.

 

Habe you driven any modern Merc, VW, Audi, BMW, Ford, Fiat, Mazda diesel lately? Yes, some redline at 5500 rpm due to the principles of slow burning diesel (diesel cannot burn as fast and the combustion pressure required to ignite diesel is bigh - both stop high reving diesels). But a diesel is well out of its purpose around those rpm.

A 40t truck with 700 hp and 1200 nm can't outaccelerate a 50 hp petrol car. The gear changes - even without trailer - take too long, as the torque is only there for around 500 rpm and then drops off...

Wankels won Le Mans and co too - and they have no torque... But loads of hp/liter of displacement.

Fact is, no diesel will beat an equally equipped petrol. Neither in torque nor hp. Only fuel economy is the diesels winning attribute!

And yes, I have driven around 15-20 different diesels - of all ages and power ratios. The onky one that impresses me is Subarus boxer diesel and the Mazda Skyactive diesel.

 

Ferdinand Piech head of AUDI,quote.

"people think they are buying horsepower,
what they are really buying is torque"

and utube,BBC top gear, BMW M cars get a tri-turbo DIESEL.


diam are really comparing a 40T truck to a car??

 

at the race tracks,here, the Mazda Skyactive D , has been dynod at 450hp, 2.2L 4 cylinder, race version!

Suby Diesel we dont get in USA.

 

eaa thanks for mention of Cummins diesel race cars, 1st one was 1931,didnt win but went complete race on 1 tank of fuel.


nowadays , u-tube BMW Alpina D3 biturbo.

2nd race was 1952, held pole position, and was leading when car slowed because of tire rubber dust choked the turbo inlet. (i have a 1/2 hr video of 1952 race, transferred from 16mm film to video).

today its a shame that in proto type sports car racing diesels are banned, they have to run in there own class(more or less by themselves).

but they do win overall, i have been to some tracks and its amazing to watch them pull out of corners and pass on the straights, all petrol cars!

 

Diesel ca be quick

check out the 5.3sec 0-100km/h for the Audi

BMW 535d v Audi A6 3.0TDI bi-turbo head to head

 

Katoh

Have you seen Ian's site His XJS has around 400hp at the engine. Engine built by Brett Thomas

XJ-SC Modifications