Y2k Jag XJ8

[PhilA]

Cleaned the MAF, shall see how much of a difference that makes. It was grubby on the hotwires so clean, they should be cooled more accurately rather than insulated.

Phil

[PhilA]

I'll tell you what, went to pass a car tonight on the way home and stamped my foot to the floor.

Hot damn. That made a significant change in how well the car runs.

[PhilA]

Picked up some extra fuel mileage.

20241229_192153.jpg (198.23 KiB) Viewed 1894 times

That's on 175 miles trip. 28.4 uk mpg.

Phil

[Hooli]

About what the Sov I had did, which is why the XJR surprised me by being so much worse.

[PhilA]

Cam timing in the R is different, that'll hit the economy significantly. That and the compression ratio is way down over the NA version so putzing about will be pretty terrible.

Going to get the front wheels balanced tomorrow, along with load test to see if they're out of balance, bent or just plain crap.

Hopefully just out of balance.

[Hooli]

Aye but the Sov and my old XJ40 did bang on what the book says. So I expected the R to do the same, which wouldn't be too much worse than the Sov. But it's actually a lot worse, although some people do claim to get the book figures on forums.

[PhilA]

They're far too easy to drive fast. I think that's some of it.

[Hooli]

Nah it's not that. Book says 27.9mpg at 70mph. Sat on cruise I've watched it creep past 23mpg when sat on a motorway and after 20mins it starts to drop back to 22 when things get warmed right up.
Something is causing it but I can't find it. All temps look ok, fuel trims are fine blah blah blah.
I've spoke to a few other owners who see the same, so it's not just mine that does it

[PhilA]

Nah it's not that. Book says 27.9mpg at 70mph. Sat on cruise I've watched it creep past 23mpg when sat on a motorway and after 20mins it starts to drop back to 22 when things get warmed right up.
Something is causing it but I can't find it. All temps look ok, fuel trims are fine blah blah blah.
I've spoke to a few other owners who see the same, so it's not just mine that does it

Makes me wonder what the timing is doing, on average, at high speed cruiser.

[Hooli]

Nah it's not that. Book says 27.9mpg at 70mph. Sat on cruise I've watched it creep past 23mpg when sat on a motorway and after 20mins it starts to drop back to 22 when things get warmed right up.
Something is causing it but I can't find it. All temps look ok, fuel trims are fine blah blah blah.
I've spoke to a few other owners who see the same, so it's not just mine that does it

Makes me wonder what the timing is doing, on average, at high speed cruiser.

That was my thinking. Early on the waterpump to the intercoolers didn't work so it lost a massive amount of power 30mins down the road. My current theory is that pump is a bit weak so the intake temps still get too high which makes the ECU retard timing. If I take it on a long trip I might watch the live data & find out.

Long term I do fancy a pulley upgrade when the timing chains are done, so an uprated intercooler pump is often paired with that. I've flushed the intercoolers out & so forth so shouldn't be anything physical with them.