What are the most efficient ways to increase hp? I have a k&n filter installed and I know having smaller tires will also increase traction and thus hp, but are there any other ways that show obvious results?

 

Sell your car and buy an XJR.

bob gauff

 

LOL Bob.

OBX- in all seriousness, Bob is right. If you start with an XJ8, your upside for power is limited. With an XJR there is much more headroom and power to be had. I have had both, and without a doubt, the R has the "punch" and the NA is "sorta" fast. See if you can test drive an R, or convince an owner to let you. It will open your eyes.

 

I have both, love them both, but there is no comparison between the two. If you want raw power, sell the xj8 and get a R. The engineers basically have maxed out the xj8, there is nothing left for you to do to gain more power.

The xj8 is what we take on long drives as it is a bit more comfortable. Lovely car.

The XJR on the other hand....mine did 0-100 in 10.5 seconds @ 18psi with the eaton supercharger. How much faster do you want to go?

The XJ8 has a weaker trans than the XJR, so say you were to use Nitrous on the XJ8, you could very well be in the market for a new tranny.

 

I dunno, I was determined to make my 8 as powerful as an R and did it

 

Care to tell the O/P HOW?

Don't think you'd pass MOT though...

 

Not much point really he could buy 3 very good XJRs for what it cost, but the pics in my signature and avatar are of my 8 engine

 

Did it go a bit like this ? Somebody/ persons..... You bought the wrong one there. You will never get X amount of horse power out of that old boat anchor !!! Retire to the pub, a few pints later have a plan all scribbled out on the back of a beer mat, after a scotch or two to celebrate how easy it will be, tell anyone who will listen.
In the morning, sober, off to the man cave ....... that's when all the head scratching wallet emptying etc begins. LOL ...... Then more good ideas, like build your own ECU off the interweb.... etc .....LOL ,

 

Wellllll not exactly..... And TBH the 8 I am referring to is an XK8 but the principal is the same, same engine.....

I bought the car originally as a crash repair with intention of doing one of my conversions on it, never got around to it, started using it as a project car, it was the first XK with XF lights fitted to the rear and various other things.

Decided at that point to see what could be done with the engine, I did not want to cheat with forced induction and the guy next door kept whispering throttle bodies to me in a subliminal kind of way and what do yer know..... Its also manual running with a Emerald K3 ECU, no cats, side exit exhaust and has gone on an extreme weight loss diet (something I could do with myself )

Doing what I do I get asked a lot "what can be done to improve an N/A V8" in either an XJ or XK and unfortunately as has been said above, not a lot..... Yes you could make it breathe more easily, fit an induction kit, exhaust, 200 cell cats, blah, blah, blah. But the sort of money you spend on that lot to gain what, maybe 20 bhp, you could trade the 8 with the money for an R and get an extra so called 80 bhp out of the bottle and a plethora or tuning goodies as much as your pocket will take.....

Face facts 8s are for cruising Rs are for cruising quickly

 

See what you mean, a manual conversion alone costs about an R. Mine was cheaper, it was a rubber bumper MG Midget 1500, £100 of second hand Ford Sierra box was my manual conversion. Mega Squirt build it yourself ECU, and fuel injectors, pump etc from the breakers. Oh and some inspiration/consolation from the pub. Got the 100 BHP they all said was impossible.

 

I guess I should have added "at a reasonable cost"

 

Maybe,........ but playing around with engines, cars in general aint gonna b cheap !!!.


" The need for speed" Easy to say, expensive to execute

 

True....true....