Hello

As Shell V Power is about £2 a Litre now and I get about 18mpg I use my 99 XKR very little now. I have heard that there is a boost control system available for the Supercharger.

Has anyone heard of this?

Just wondering how much it would cost, what would be the mpg gains for everyday driving and if it would cause any problems.

Thanks 👍

 

Just remove the supercharger belt so that you can drive boostless. However, it will be slower than an XK8 if you do this.

 

You should get more then 18mpg, esspeciallially if you are using more premium fuels. I get 24mpg on E10 Tesco fuel. Regardless you will spend more on a clutch system for the supercharger then you ever will with fuel bills.

 

The XKR has a lower compression ratio and would have worse mileage than the XK8 with no boost, especially with no VVT. There is a simple vacuum operated bypass that you might be able to block open and negate boost. It won't cost anything and you could always reengage it at any time. The ECU might go nuts. Without boost, you could safely run regular with that low compression. Again, the fuel mileage would likely suffer but you'll save money.

. I personally removed the vacuum line to the bypass from prior poor experience with a similar Eaton blower setup- at a certain range, like right at the highway speed limit, it would increase and decrease boost, up and down on its own and made it impossible to cruise at a steady speed. I also did not like feel of power on my XKR that was arbitrarily limited by the bypass at lower RPMs and then kicked in hefty boost with a small increase in throttle. It sort of reminded me of a two stroke motorcycle that would suddenly "come on the pipe" if you know what I mean. I prefer more of a predictable, straight line throttle/power relationship.

I also do not agree with the logic for the bypass, but we won't get into that.

I have a friend that has a "blown" Chevy hot rod, but there are no lobes in the Jimmy supercharger, it's just normally aspirated. It used to get "Best of Show" at Autorama, a half century ago. You could gut your Eaton, but I wouldn't.

If the blower belt were remove, it would barely run, if at all.

I don't have an issue with fuel mileage on my XKR, it is parked for now and I'm driving one of our XK8s. 18 mpg sounds like you do only city driving. Make sure your tires are aired up.

 

One thing you could do is stop wasting money on Shell V Power and use cheap supermarket fuel instead - unless your car watches TV and sees the advertising, it won't notice the difference and if your engine doesn't run properly on normal E5/E10 then its time to fault find it.

 

18 around town sounds about right ...I just got 33mpg (UK gallon) on a trip from central England to the Somme in france running about 75 mph on the autoroutes.
If you take the charger belt off the vanes will not rotate and will block the airflow.
The biggest fuel control is your right foot.

 

If the belt is removed, engine vacuum will have to spin the screws. Virtually no air & fuel get past them if they don't rotate. It may idle with high vacuum but it won't run worth a darn.

 

it will run ok…

the hellcat and the old amgs were all clutched off

 

Thanks mate, I think it was a stupid question that I raised, if I am honest. I just saw the Variable boost control on a car resto show and thought "Oh I wonder if that would work on mine". It was for a Turbo and S/C probably would not work. Tyres are always kept to 30PSI back and 32PSI front .... obsessively. So yes you are right 18 is about right, I have only done one 100 mile run recently and got about 23. I have to live with it and use it less... walk and take the bus more 😀👍
Thanks mate 👌

 

It runs fine but uses a lot of juice, suppose it is the nature of the Supercharger being on all the time and less efficient than a Turbo. I completely disagree with your opinion about supermarket petrol respectfully. Shell fuel or any super Unleaded is better for your engine especially with older performance cars, it is cleaner and purer than the supermarket stuff and contains the cleaning agent IMVHO. The V Power RON is 99 as opposed to supermarket 95. You do notice the difference in pickup and acceleration

Just my opinion, respectfully 😀👍

Cheers

 

Thanks, confirmed what I thought 👍

 

I run both my cars and my boat on supermarket fuel and they run just fine. If its additives you want a can of cleaner from time to time isn't expensive. From what you've said the price of supermarket fuel is at least 30p a litre cheaper than V Power which is quite a lot of miles per pound more. Your choice of course, but I guarantee a car running on supermarket fuel is always going to be faster than a car parked in a garage with a tank full of V Power.

 

I run my 4l xk8 on Tesco E10 and French E10 and did 33 MPG on a recent trip to the Somme.
Had to change a plug last week ...cigarette ash grey so burning perfect.

 

Fair comment, but the supermarket stuff is only about 3p cheaper than standard Shell. The V Power ranges from 10p to 15p more. You are right, it is all about getting out and just driving it.

 

Some of the reports regarding the new E10 for standard petrol in the UK do worry me slightly if I am honest. Our trustworthy government say that any car from 92 onwards will be fine.... hmm
That seems like a very arbitory figure.... other independent opinions by motor magazines say that it may cause problems for any car more than 15 years old and 100k miles, especially in respect of the extra ethanol content degrading rubber hoses and connections etc. I think I will keep using E5 super Unleaded to be on the safe side, pay the bit extra and use it less.

 

the whole industry has been ready for decades. every jaguar since 93 is explicitly e10 ready

nobody has problems with old vehicles and ethanol, even old 80s junk. occasional/zero use vehicles will have trouble with white gunk settling in the tank, regardless of age

 

Fuel injected cars will have zero issues with the E-10.

only carburetor cars that let the gas sit 3 months or longer will have some issues with fuel separation, otherwise the E-10 worries are greatly overblown.

Z

 

E10 isn't a new fuel, it has been around for decades in other parts of the world. Have a look in the manual that comes with your car and you will see that Jaguar says fuel with up to 10% ethanol content can be used. By the way the manual also lists the octane requirements for the engine, and has a few words on super unleaded.

 

OK thanks , I think maybe the typical tabloids non knowledgeable so called journalists were scaremongering when they said E10 might destroy the rubber hoses on older engine components. Also I am wondering why the Super Unleaded is still E5.
The jury is still out to be honest, still unsure. I know that the modern super cars like the Koennigseg run even better on bio fuel. Thanks 👍

 

E5 isn't banned, so I suspect the retailers have Super Unleaded as E5 and the other pump as regular E10 so they can offer both E5/10 with just two pumps. As they no doubt sell far less Super than regular I suppose they can still achieve their targets for renewables while selling both grades. How long that will last I don't know. I think the most important thing as ever is to use the car and not to leave petrol sitting in the tank and fuel lines going off. I actually converted my boat to run on portable fuel tanks for exactly this reason - I never have stale fuel. Even if the ethanol were to destroy any seals or rubber in the fuel system, its not exactly the end of the world to change them (on my boat the only original fuel system component are the braided hoses from the filter to the pump/throttle body - everything else has been changed anyway).

Ethanol has a higher natural octane rating than petrol, so maybe that is why a high performance engine like the Koennigseg uses it. This means that on E10 they need less octane booster than on E5, so that is one less additive wasting space in your tank.