I decided to try and get a few more BHP's out the old Jag for something to do, she's a 98 with 155k so I don’t want to do anything that’s going to put a strain and break stuff. She's recently had the head gasket replaced along with head skimming and compressions tested so all is well in that department, it has a new water pump, thermostat, upper and lower tensioners and a new chain, gearbox also feels good.

The only mods currently are a panel filter (K&N), 200 cell Cats and a aftermarket stainless exhaust system.

So what am I running currently and what does that leave me to achieve my target of 450BHP.

Your tuning help greatly received.

 

First step is get it on a dyno and get a base run.

Then you have two options:
1) Avos' Twin Screw
2) enlarge your intake, MAF, get the throttle body and elbow bored out/enlarged, port the supercharger, upper pulley, lower pulley, water+meth, killer chiller/radiator mods, and something to keep the fuel pressure up

Last step would be an LSD, and upgrade the brakes. Later model Brembo's are a good way to start, but there are aftermarket options too

 

You should be able to get into the 450 crank hp region with basic mods. As L80ous said, upper and lower pulleys, intake and exhuast, some increased fuel pressure, and some upgraded cooling should get you there. 450 hp at the wheels though will probably require a twin screw kit.

 

Yeah I'm after 450BHP at the crank.

Will I need both pulleys as this will require a lot of cooling work, uprated radiator etc.
Could I get away with lower pulley 35bhp? and 3.5 inch intake elbow 15bhp? Including my mod's this way I can leave the cooling standard so I understand.

 

450bhp is not easy thing from Eaton powered 155K engine. We have not seen any dynos over 440bhp. Pulley changes gives not max power if Eaton is stock one. You just get the power at lower rpms and that makes a feeling that you have more powerful engine.

 

So the lower pulley gives more power lower down but doesnt increase peak BHP, more power anywhere in the rev range will make the car faster, so not to be crossed off the list.

Why is 450bhp unrealistic in a 155k car?

I doubt my car is down on power, the first 1/4 drag run I did (Santa Pod) with a full tank of fuel I pulled a flat 14 seconds (including a 0.45 second reaction time) and I'm a heavy bloke as well. This was before my exhaust and cats also, and my previous cats where in very poor clogged condition with holes.

 

Or, take the easy route and buy an XFR!

 

To be honest, chasing numbers is a stupid game. Do the mods, drive the car. At the end of the day, on a dyno, the car will make what it makes. BHP is a made up figure anyway, with an 'assumed' drivetrain loss.

Go and get your car measured on a dyno, you should have around 300-320rwhp currently, and if you can get that up to ~400 then I very much doubt you'll be complaining.

Also just to clear things up a little bit, the reason pulley upgrades on the Eaton don't make significant hp gains is because you end up overdriving the blower, this causes a lot of extra heat, which offsets and gains you would expect from moving more air.
What you do get though, is more air throughout the rev range, which means you get a nice increase in hp and torque lower down in the rev range.
You can do all sorts of things to counteract the increase in temp, like a killerchiller, upgraded radiator, splitting the IC cooling system from the regular cooling system, adding water/meth to reduce intake temps etc etc. These will work, but you will always be limited by the blower.

You should still see a very nice increase in power, and a much more noticeable increase in torque through the whole rev range, but don't be disappointed if you don't end up with the right imaginary number on a machine

 

This is with only a lower pulley/stock upper on an eaton. Many upgrades to increase diameter of entire intake track. This 4100 lb car 0-100 mph in 10.5 could not be accomplished with less than 450 BHP. This is a real world performance on video, not just talk. Don't believe people that say it can't be done. I did it, you can too. You can't come close to a twin screw with an eaton but you can easily top 450 hp and a do a low 12 second 1/4 mile.

If you do upper and lower pulleys without porting everything you will overspin the blower and only make lots of heat. The right way is to make it easier for the blower to blow. Simple as that...

This video was shot on my cel phone, not fabricated in an animation lab.

 

Just a lower pulley and intake? No water/meth or any other mods?
I thought you had a few other tweaks when you did that run?

Not saying I don't believe you, just trying to get the full picture. After all, I'm (hopefully) on my way to doing the same thing

 

There is no matter what's your reaction time. It can be 0.45s or 2.45s and you still run flat 14s.

 

WD: You should have made dyno and 1/4mile test after all the mods you have done to stop speculations about the the power and time - and help others with Eaton to know the limits.

There is one 4.4litre XKR with Eaton which dynod 525bhp - but it needed 10% bigger engine capacity with new pistons, more agressive cams, ported heads, headers, high flow cats, catback, bigger MAF, upper and lower pulley, bigger TB ( I guess ), chiller killer and new ECU, which has been carefully tuned per each cylinder. Let's see what's the output when change to TS, but should be easily +100bhp more.

 

That is a massive increase in pace for a lower pulley and intake. I get a feeling of negativity from this forum in tuning the XJR, as such it can’t be done or perhaps pointless doing it.

All I'm I’m after is increasing the midrange pace of a now very old supersaloon and with a S/C V8 this shouldn’t be an impossible task. The mod's I’ve done people say are pointless and give no gains and the mod's intend to do you lot say the same. Why the long face?

I find it hard to believe increasing a blowers PSI would have little effect, it certainly has an effect of all the turbo cars I’ve owned in the past. As for the extra heat it creates, I'm only looking at doing one pulley, alone this can't create enough extra heat to cut out the gains it provides?

 

The pulley upgrade alone won't get you huge gains. It will get you small gains, but remember a supercharger makes boost in a very different way to a turbo. You will get gains, but it's more in the mid-range than top end, unless you deal with the heat and restrictions elsewhere in the system, including the blower itself

There is a lot of skepticism on this forum (and the XK one) when it comes to mods, but that's because historically they have been very expensive for very little actual gain. Avos, WaterDragon and a handful of others have made very good improvements over the years, an there's plenty of information if you search too

I know WD has changed his setup a few times over the years, and has since sold the car too, I believe? Either way, I just wanted to confirm exactly what was done when he made that run.

As I said in my first reply, there are things you can do to get a VERY quick car, but it's a package deal, there is no single shortcut to 400hp

 

These make for good reading
https://www.jaguarforums.com/forum/j...s-50-hp-95208/

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

 

What can look like negativity is due to people who've dynoed, tried various mods, re-dynoed and been disappointed. So, various mods are known NOT to make big numbers. Going down the same paths is fine but expect no great outcome.

 

"I find it hard to believe increasing a blowers PSI would have little effect, it certainly has an effect of all the turbo cars I’ve owned in the past. As for the extra heat it creates, I'm only looking at doing one pulley, alone this can't create enough extra heat to cut out the gains it provides?"

L8ous- I think the issue is not so much that increasing the PSI "has little effect" as it is that spinning the compressor only has a small increase in pressure without other changes, and that the energy needed to spin it faster is significant. Remember from high school physics that energy is conserved. The energy taken from the engine that make heats in the infeed air does not result in more power. Have a google at the term "non adiabatic compression" and "adiabatic compression".

So, although WaterDragon's explanation is an oversimplification that would make a physic teacher cringe, it sort of explains the problem in simple terms. The Roots type blower operates efficiently when in the range of the design pressure increase. Over that, its efficiency drops off quickly. So, run it faster and reduce the pressure rise that it must generate by lowering pressure drops in the rest of the system.

I will tell you that, unlike some BS yoiu read on the internet, on this matter, the reported experience of many folks matches the theoretical predictions made by others! Great online conspiracy? I doubt it!

 

So to sum it up in layman's terms, leave it alone cause it's already running near enough peak performance as standard?

 

Yes, I should have done more dynos and the 1/4 mile when I had that set up before I sold that car. There can be no doubt, after seeing that video, that this is a 12 second car, on street tires, at street weight.

When I first came to this board I was not able to discern what information was correct and what was incorrect.
I think people should be able to get accurate information about what mods do and do not work on this board. I hope others can benefit from my successes and failures, so I am displaying my info of what worked for me here: This is a cut and paste of the first post of the links below:

2000 XJR with 56,000 miles. When stock, the boost gauge read 9.5-10 as all 4.0s do. It is the 4.2s with the larger crank pulley that get 11.6. Those who say otherwise are flat out ignorant. After my mods I see 18 psi when it is above 65 degrees, and 19 if below 60
Here is a list of the mods I did to get the performance you see in the video:
ProM 92mm MAF
Custom 4" to true 3.5" less restrictive intake
Maxbore.com TB used stock tb, was 75mm, now 82.5 mm +20% flow at the same pressure
port matched elbow between TB and blower
water/meth injecting before the Steig ported blower this gave additional 1 lb of boost vs injecting after blower
Lower +4 lb pulley installed
Kenne Bell Boost A Pump 17.5 v to pumps when activated. The stock fuel delivery system tops out at approx +20% or +74 HP, so you MUST add fuel delivery capacity or you will be limited to an approx +74 HP gain from any number of mods.
Completely stock exhaust
12" pusher fan in front of inter cooler radiator (this made a big difference)

Notes: I'm running 245 45 18 tires, these are 3% larger than stock tires, so the speedo is reading 3% low. Also, this was not a hard race "launch" using the stall converter, so the time obviously could have been better, and this was with 3/4 tank of fuel, and a full trunk, so I could have taken out over 150 lbs, but I did not because I wanted a real world accurate test as I am not selling anything. This is not marketing, this is a video of a real run.

When I first came to this board I simply trusted what I read on the board, but after learning enough to suspect some opinions were likely wrong, and I started to suspect some were intentionally giving incorrect information, I started testing things myself. I have tried many things that did not work, and found that some of the information given on this board was very incorrect, like:
1: Eatons could never perform this well, to that I say really? did you see the above video??
2: Porting Eatons does not work or is counter productive, but I gained more than 1 PSI via porting, porting reduces temps too.
3: Adding pulleys is counter productive as they make Eatons consume more power than they would make, this has proven to be baloney, fancy graphs are posted which are completely incorrect and stated as "fact" on this site that propose adding a lower pulley will only gain 15 hp. This graph is completely incorrect and frankly B.S. When you watch my video, does it appear the power at the top end rpms is only 15 hp over stock? Not a chance, this car PULLLS hard at the high rpms! Like I said, video proof trumps non-factual, non-evidencial graphs any day.
4: Modified Eatons will make so much heat your engine will always be suffering heat soak- again, not in my experience, mine does not fade run after run after run. Of course I beefed up the cooling efforts. The water/meth injection has been VERY effective, and ported blowers run cooler. The 12" fan on the inter cooler radiator has worked very well for me, probably as well as or even better than a much more expensive larger radiator with no fan. Again, I do not see any major heat fade. I have the stock inter cooler radiator. I do not believe you need to upgrade if you have water injection and a fan in front of the inter cooler radiator.

These 4 above were things I was incorrectly told definitely would not work, but tried myself anyways and found out for myself that they do work...and very well. I'm giving the above list because these things do each work to add power and were not expensive or hard to do.

As you can see, the car is pretty fast, and reliable so far, even with the stock head gaskets (knock on wood), and the stock rear end is still holding, these are all straight bolt-ons, and you can do one piece at a time if you like. Many of these parts can be found used at large discounts on Ebay, etc. This build could be duplicated for $3,500 or less and yields approx +100 flywheel hp over stock as evidenced by the reasonable 0-100 calculators and the fact that adding + 8 to 8.5 psi of boost, while still successfully controlling temps could yield no less than approx 100 hp.

For the record, my aim is not to have made my car the fastest. My goal was to get to the point of diminishing returns and stop there.

This car is somewhere in the mid 12's 1/4 mile.
__________________
Have a look in the engines section, then send me a PM or post here. I am happy to help.

here are a few of my posts:
https://www.jaguarforums.com/forum/x...19-psi-108378/
https://www.jaguarforums.com/forum/x...easily-119287/
https://www.jaguarforums.com/forum/j...terial-101234/
https://www.jaguarforums.com/forum/j...rt-deux-76322/
https://www.jaguarforums.com/forum/j...-inside-99281/
https://www.jaguarforums.com/forum/j...coolers-98272/

 

More power can be had, it's a matter of which ways work, for what gain, at what cost. Past some desired gain level about all you can do is use a TS or go very expensive.