04 XJR...Assuming it is 390 HP stock...There is not much you can do with this year...Adding the obvious items as follows...K&N drop in, 1.5 lb supercharger pulley, air flap mod, and large intake piping...If there's something I forgot please chime in...PS not doing cats...I'm hoping for 420 BHP...

 

Clean out the throttle body back thru charge coolers if higher than 50-60k miles.

Put in an X-pipe with front resonator delete.

Upgrade SC cooling system to delay, at least, spark retard at anything near WOT.

Large air intake piping does not address the "elbow" restriction below the throttle body.

Oh yes forgot LSD. Spinning one wheel kinda negates the power.

 

I will search some of your ideas...Thanks Jackra!

 

I will be interested to see if you come up with anything that I have not thought of Viper.

My XJR is not my daily driver but is the preferred ride for long trips. Since I am retired I dont have to drive daily anyway.

 

Viper,


Those mods are a good starting point. Maybe not completely 420 bhp, but will waken the car up. You'll feel a better response. John is spot on with the cleaning and cooling mod.


Though, I'd be careful changing the diameter of the intake tube where your MAF is. If I am not mistaken, the stock tube diameter is used in the algorithm that factors in several inputs to determine how much fuel to run. Changing you diameter may keep the amount of air flowing the same, but increase, or most likely, decrease the velocity of the air flow which would impact that calculation. Think of plumbing, 5 gpm of water going through a 1" PVC pipe, vs 5 gpm going through 3" PVC... same flow rate, different pressure and velocity.


Most of us just upgrade to a more free flowing intake tube and filter, but I cant remember reading about someone upgrading to something bigger, with the exception of a few (mainly for a TS) and even then, had to have a custom calibrated MAF made up.




One more thing to watch out for..... once the modding begins, its hard for it to ever be enough. I think most of us who have modded our Jags started out by saying "just an intake, pulley and exhaust will do"

 

Quote:"One more thing to watch out for..... once the modding begins, its hard for it to ever be enough. I think most of us who have modded our Jags started out by saying "just an intake, pulley and exhaust will do"
__________________
So true Jazzyjags!

 

Do yourself a favor and put in a oil catch can between the PVC valve and the intake elbo. You will understand why when you get a good look at your intercoolers.

My 2 cents worth.

Wooford XJR

 

+1 on that. One of the first things I did after cleaning out everything and it does catch oil!

 

[QUOTE=jackra_1;1905395]Clean out the throttle body back thru charge coolers if higher than 50-60k miles.



Upgrade SC cooling system to delay, at least, spark retard at anything near WOT.

Large air intake piping does not address the "elbow" restriction below the throttle body.

Can you elaborate on these key points? Thanks!

 

When things get hot and you are accelerating hard there is a chance of pre-ignition and I believe the ECU will retard the ignition.

Quote from Cambo a while back :"Yes absolutely, the cooler you get the charge air, the less it will pull timing out".
That was in the thread you started on "Quest for 450 hp".

At the same time the super charger will not be operating at optimum output because of less dense air.

A meth/water system can play a role in cooling things down as well.

The elbow under the throttle body is a set diameter feeding the SC and not much can be done about that. So a larger diameter pipe feeding into the throttle body ends up by being restricted by that elbow.

So you can increase the cooling capacity of the SC cooling system as well as upgrade the SC pump to help out in cooling things down a little better.

 

Also look at ceramic coating the exhaust manifolds.
This removes most of heat source under the hood and has in a massive effect reducing heat soak.
Why start with hot air?

Coating the intake and coolers is optional as it does not have the massive improvement. That being said I also have the cadofy intake tube done.

If you search you will find the results from testing I posted some time ago

Cheers
34by151

 

My car made 398hp on a mustang dyno, after a Mina gallery intake tube and filter 1.5 pulley , resonators deleted. I took it back to the same dyno after I added high flow cats 200 cell, bored throttle body and changed out the rear stock mufflers. The car gained about 7hp,but lost about the same in torque. The car felt like it gained the most when I did the last round of mods. I have a meth system almost completely installed, but don't know if Ill finish it since I bought a supercharged AMG to play with

 

Wow! Mustang Dyno's do not give HAPPY WHP numbers...If you figure 15% driveline loss, that would be 460 BHP! On a Dynojet The numbers would show even higher...
An automatic tranny robs 15% loss minimal...And yes Jackra if the meth cools the charge then you will gain HP by pulling less timing, but without tuning it will be a lot less...I gained 50 WHP adding meth injection to my supercharged Viper...

 

When you say 398, you mean at the crank, correct? Hard to see on the graph, but is it showing 312 rwhp? Nevertheless, it still definitely shows an increase over factory numbers on a mustang dyno.

 

Your right that makes sense.

 

As far as an ECU tune to furthert ake advantage of my water/meth setup I do not want to run the risk of damage if I run out of meth/water on a long trip.

I have a VAP tune on my 2013 Range Rover Sport HSE. The beauty of that is I can go back to the original tune in about 10 minutes if I wanted to.

I may well have problems in MA getting emissions when I eventually move back up there with the mods that I have done on the Jag. I have all the necessary parts to reverse all of the mods just in case

 

398 at the flywheel.

 

OK...Mustang dyno's do read low...I don't know if a Dynojet is more accurate tho...

 

Jackra, You seem to maxed out your XJR...What do you think your BHP is? I can tell you I drive mine in the winter when the roads are dry and when it is 20 to 30 degrees what a difference in power opposed to summer driving, so a cooler charge makes a huge difference!

 

viper1996 I have no idea what my BHP is. Some day, when I have moved to MA, I will go and get the car tested.
I do know that when my rear tires "catch" the car accelerates much more quickly than before I did the mods. Sometimes they catch and sometimes they do not depending on the road surface.
Before I did the mods I had really filthy charge coolers etc.