[Shellsbluebikini]

Good old A5OC - I recall those tails of woe !

Yep...that's the one...I think the guy was from somewhere in Eastern Europe....Slightly off topic but when Audi upped the power from 200bhp to 265bhp for the S3 they strengthened the engine internals,fitted a slightly bigger turbo and upgraded the inter-cooler and radiators...and fitted a new and upgraded Dsg auto box to cope with the extra torque...all done no doubt so they could guarantee the engine and drive train

Back on topic...I think the 3.0d engine fitted to the XF is a genuine 300bhp lump...the varying outputs are probably no more than marketing tools...The lowest official BHP was 211hp...the highest as far as I'am aware is 295bhp...84bhp from highest to lowest output..that's a significant difference in anyone's book and all done without any upgrade of the engines internals...ok bigger injectors..but that's it!!

 

[wilf]

I still actually haven't seen hard evidence to support the anecdotal fitment of larger injectors/revised exhaust to an "S".

To me, it is just a chipped 3.0D, not that it is any the less for that.

 

[Seahorse]

Has anyone bothered editing Wikipedia so the numbers are right?

 

[Shellsbluebikini]

I still actually haven't seen hard evidence to support the anecdotal fitment of larger injectors/revised exhaust to an "S".

To me, it is just a chipped 3.0D, not that it is any the less for that.

I also suspect this to be the case...although I do believe the injectors are slightly bigger....but I'v never read anything to suggest the engine internals have been upgraded....something which most manufactures are only too happy to highlight in their promotional material....if only to justify charging extra ££££ for the privilege of having a few more horses under the bonnet

 

[Chaz]

My 535D was remapped to 700 NM which is the known limit of the gearbox .... plenty have had that done, no issues. I remapped my 535D 2 days after buying it .....

 

[Rigger]

The turbos are sequential. Rigger sums it up very well in his earlier post. The only thing I'm not certain about is whether or not both turbos operate above 2700rpm.

I'm fairly sure the first turbo gets bypassed. Otherwise the volumes, pressures and flow rates wouldn't work well if both were working together. I'm also fairly sure the switch over for the turbos is 2800rpm.

 

[Tam Lin]

I'm fairly sure the first turbo gets bypassed. Otherwise the volumes, pressures and flow rates wouldn't work well if both were working together. I'm also fairly sure the switch over for the turbos is 2800rpm.

According to the Jaguar Technical Guide, the primary turbo is responsible for all the boost up to 2500 RPM, but acts over the entire rev range: The higher revs are referred to as the bi-turbo regime.

 

[ExFS]

The turbos are sequential. Rigger sums it up very well in his earlier post. The only thing I'm not certain about is whether or not both turbos operate above 2700rpm.

I can remember a very interesting link on a previous post somewhere which had a moving diagram showing the turbo flow in operation. I had a search but couldn't find it, does this ring a bell with anyone else. Was it perhaps pre jaginfo?

 

[TheStig]

I'm fairly sure the first turbo gets bypassed. Otherwise the volumes, pressures and flow rates wouldn't work well if both were working together. I'm also fairly sure the switch over for the turbos is 2800rpm.

I just wonder if a small turbo could cope with the air flow at high engine speeds on it's own? If the air was already pressurised by the big turbo then that would make sense. I'm just guessing!

 

[wilf]

From memory, are there not multiple valves/flaps in the intake manifold to control the airflow? I can recall seeing an animated schematic showing how the turbos worked, can't find it now.

Whatever, it is complex, and I am content to leave it be to work its magic.

 

[TheStig]

Nice find Tam Lin.

It looks as if the output from both turbos is 'Siamesed' over 2700/2800rpm. Below this the small turbo is idle.

 

[Tam Lin]

I can remember a very interesting link on a previous post somewhere which had a moving diagram showing the turbo flow in operation. I had a search but couldn't find it, does this ring a bell with anyone else. Was it perhaps pre jaginfo?

It's in the same guide I quoted above

 

[Tam Lin]

I just wonder if a small turbo could cope with the air flow at high engine speeds on it's own? If the air was already pressurised by the big turbo then that would make sense. I'm just guessing!

It's an incredibly elegant piece of engineering and -Jagular mode- latest generation BMWs and Audis are of course using triple sequential turbos-/Jagular mode- so in my case the car would be permanently at the dealer's having its actuators replaced sequentially

I think the primary reason for spooling both together and sorting out the complications that causes is the "smoothness" of the transitions this allows, so you get a relatively clean torque curve rather than a camel race seen sideways on..

 

[Rigger]

I stand corrected Tam Lin, and thank you. I was only working off memory, but always good to have the hard facts there in black and white. Do you have a link for the schematic shown in your posts?

 

[coneman]

That's brilliant Tam Lin, I had never seen that before and it is as you say elegant.
However, I think I could probably be happy with just the single turbo for about 99% of the time. I hardly ever seem to get above 2800rpm (cue sticking actuator).

 

[Chaz]

According to the Jaguar Technical Guide, the primary turbo is responsible for all the boost up to 2500 RPM, but acts over the entire rev range: The higher revs are referred to as the bi-turbo regime.

View attachment 6980

Thanks for that. Out of interest, who remapped your 3.0D (non S?) and what are your thoughts on it - have you 'compared' it to a S version yet?

 

[TheStig]

The exhaust from the big turbo seems to go to what looks like a DPF. There isn't one shown for the small turbo's exhaust. Does this mean there's no DPF on the exhaust gasses flowing from the small turbo? If so, this would suggest that the ideal revs for a forced regeneration would be just below 2500.

 

[Shrek]

As a remap pumps more fuel in under hard acceleration, does anyone know what effect this has on the EGR? I had a 2.5 TDI Audi that was remapped, and it managed to lunch the EGR sometime afterwards. I've read reports on some cars that the EGR can soot up under normal map/operating conditions, so a remap would make that happen sooner, no??