Hello everyone,

Just curious as to how much horsepower you can possibly achieve with modifications for a 1998 Jaguar XJR?

I would like to have around 500rwhp if that's even possible.

If that is possible, how much would it cost to get it done?

Thanks.

 

I believe that achieving 500 on one of those should not be a problem. Port the head, port the inlet, bore out the throttle body, smaller pulley for supercharger and that should give you relatively positive results already. Speak to Andy about remap, upgrade the exhaust... Others might chip in here what else could be done.

 

Theoretical, power on such engines is proportional (and "anti"-proportional to the strokes, you can not change...) to:


number of cylinders, you can not change
engine's volume, you can increase,


fuel's thermal efficiency, you can try
compression ratio, you can increase
revolutions per minute, you can increase
air's (you burn "fluid", air) density, you can increase

fluid, you can add to air other "fluids"


and a coefficient who includes:
valves timing, you can change camshafts
fluid's flow, you can improve
ignition's timing, you can improve and some more I don't remember right now,



main mechanical loses:
pistons friction,
main bearings friction,
valves springs,
generator,
water pump,


since your engine is super charged you don't have "pumping" loses,
.






Thermal loses:
cooling,
exhaust,
again, since your engine is super charged you don't have cylinder's fulfilling loses,
rest thermal loses, heat (and noise ) all around,


so you can pick up and increase (or decrease) what ever you want from the above,
success !!!
the most "powerful" engines (highest efficiency, you spend fuel to gain "work") are two stroke, with exhaust valve, supercharged, diesel, 72rpm, ship engines ~56% efficiency, "our" engines are from 30% to 40+%

 

Thanks for the reply. I've been getting some great information both from posts and pm's! So.. a 500 horsepower engine is possible?

 

Just to be sure - are we talking straight 6 or v8?

 

Lavaman, 500HP is possible. For sure. The engine has the volume to do it.

The easiest and cheapest is to machine the cylinder's head, thus increase the compression ratio. No need of reprogramming anything. Cost, only the machining is less than 50 euros in my location, the rest of the job is yours or some mechanic (disassembly-reassembly) the cylinder's head.

Further actions require reprogramming, (or carburettor(s), cancel the ECU......),you "push" more stuff in (air or nitro or whatever) you need more fuel to keep the air/fuel ratio. Theoretically the MAF has to inform ECU for more stuff in, so you can polish you intake-exhaust manifolds, the cylinder head ports, bigger valves, change the cams, increase compressor's (is your engine supercharged or is atmospheric intake?) rpm etc., but practically I don't know if the ECU is limited to MAF's output range. Grate role on this issue have the injectors also. It's not only their duration of injection, but the quantity of injected material also.



Increasing the compression ratio will give you more power, throttle response (sharpness) but depending how much you increase it, you lose engine's durability.


All the rest methods to increase the power (check FireCrow's post) you need reprogramming.

Whatever additional you do, you will get the more power in a narrow range or rpm, outside this range you will "loose" your car.
The car's design is such that you have power and fuel economy in a wide range of applications (customers), if you want pure power, try something else designed to give pure power.
(something is wrong with my enter key and paragraphs, sorry)

 

4L V8 - supercharged.

 

This is X300 I6 forum

 

500rwhp can (and has) been done. As stated above porting the heads and regringing cams is a good place to start. You will also need one of these:

https://www.jaguarforums.com/forum/p...xtra-hp-42059/

The Eaton is already near is maximum efficiency, and while you can make some minor gains by spinning it faster, the kind of improvement you are looking for need a larger displacement blower and a fundamentally more efficient design.

Not cheap, but very achievable.

 

There are two answers to that question... what is possible and what is practical. Then the question becomes what you mean by "modifications"... New crank? new block? New heads? Then you have a new engine!

 

What is possible. This will be my second XJR, so I can afford to blow it up if that ever were to occur, lol..

I am basically wanting to "experiment" and see how fast I can get it to go.

 

I suspected as much... you're in the X300 section, which covers the straight six XJR rather than the X308 V8, so some of the answers above may well be assuming you've got a different car!

You may get better results here: XJ ( X308 ) XJ8 / XJR - Jaguar Forums - Jaguar Enthusiasts Forum

 

These engines (piston/crankshaft) are on the same principal of work, doesn't matter at all the fuel they burn, their cylinders quantity, their orientation, etc., etc., etc., etc.,
they all follow a thermodynamic cycle, you spend fuel (heat Q1) and gain mechanical work (heat Q2) (i'll try to include the graph of the cycle, Otto, Diesel, Sabatier).
The more Q2 the best for us, this depends on some, many, factors:
fulfilling (and emptying) the cylinder, spark or ignition timing, rpm, compression ratio, fluid you use to burn your fuel, your fuel also, mechanical loses, pistons friction, main bearings friction, and so on and so on
Designers aim the hot spot on an engine, but engines run all the same way.
Such engines are working round the clock for months at their full power on ships and on electrical power generators, our engines on full power can not survive three months running round the clock.....
So, power you get from your engine, doesn't matter if is line 6 or V8 or what ever, just find your way to increase the Q2..
Do the machining on the cylinder head is the easiest method, take care on valves-piston closer relation ship and chain tensioner.

in the diagram,
the more area at the blue spayer, the most power
the less area at the red sprayer, the most power
the diagram is for atmospheric intake, thus in a super charged the Patom line lays bellow the diagram.

 

As you have been told, you need to go to the X-308 or the XKR forums. When you get there, for how to make HP cheap, look for WaterDragon's posts. For how to get the most reliable and highest HP, look for Avos.

 

an engine....

 

another engine...

 

an other one, check the catwalks..

 

Well, the following "XJR Evolution" webpage says that "These cars (X300 XJR) can be modified very easily to produce in excess of 400hp and still be very reliable."

XJR Evolution of the species

Not sure how easily attainable that is with the AJ16, but like all things there is certainly bound to be different stages based on investment required.

Other than the first and probably most cost effective..... 'bang for buck' steps of a "Stage 1" "andybracket" and high flow air filter which is a ~$150 expense, it would be interesting to hear of the next verified "Stage 2" (and beyond) level and cost/benefit. ...short of engine life shortening and huge expense.

For example, maybe a Magnum Power $375 M90 supercharger port job, etc?



.

 

Just please, don't involve the 'stages' here... Every time I hear someone mention them, I want to shove a pineapple up their mouth just to prevent them from talking about performance mods...

 

Someone go to the bathroom in your cereal this morning? Stages, steps, increments choose your word to describe increasing levels of "tune" does not matter, and to say it does shows a childish attitude commonly found in a video game forum not a jaguar forum.