KurtVerbose wrote:

The turbo's for the 4.4 are quite different. There's one large turbo which does most of the work and a smaller one that comes in for high power. On the 2.7 there are twin turbo's, one feeding each bank of cylinders - same for the 3.6.

David, the small turbo works at low pressure (stopping turbo lag) feeding the larger turbo... Kind of A then B scenario as the bigger the turbo, the more lag you get (like big turbo scooby's and evo's) hence the small one to eliminate that...

KurtVerbose wrote:

The turbo's for the 4.4 are quite different. There's one large turbo which does most of the work and a smaller one that comes in for high power. On the 2.7 there are twin turbo's, one feeding each bank of cylinders - same for the 3.6.

Yes, that's the BMW way, with sequential in series turbos - a small one that spools up quickly that is then force fed by the large one as it comes up to speed. At higher revs the small one is completely bypassed.

When the high output 3.0 V6 came out, and the V8 is the same, everyone was surprised to find out it had sequential turbocharing, but in parallel. The larger variable vane turbo is running all the time, but at higher revs and high power it is joined by a smaller one in parallel.

It does make sense, and both systems have their advantages. BMW have gone on to make a 3 turbo engine with approx 130bhp per litre, but what you really want is a a small turbo to start off with, with a larger one mounted in series as revs increase, but then both operating in parallel at higher revs. The valving for this might be a PITA though.

Last edited by KurtVerbose on 9th Nov 2013 3:47pm. Edited 1 time in total

n1cktdv8 wrote:

I am pretty sure my TDV6 was a single turbo ?

I remain very interested in the remapping of my own car but it only takes one bad word in a score of many good to cast a doubt....

Looking forward to reading some successful remap comments  Is this where I put the car details and a bit about myself ?........

Ok, sorry for the belated response. If I'm honest i did not notice the gains immediately as with other diesels i've had mapped, i can only attribute this to the weight of the FF. of the line was not much of an improvement, i was for warned of this as apparently the gearbox will limit the torque from standstill.

Once moving the torque increase is most noticeable at motorway speeds the car accelerates with much more urgency right up to licence losing speeds! whilst going up hills she will hang on to top gear far longer than before.

with cruise set at 70mph the obc was reporting 30mph, best i ever managed before was 27.

I would recommend as the whole driving experience has greatly improved. -----------------------------------------------------------
Got: FFRR 2007 TDV8 Stornaway
Nissan 350z
GSXR1000 K5
CBR1100xx
XR400
Had:
Jag XF
Merc E320
Volvo XC90

Is it worth 500 quid?

Hell yeah! -----------------------------------------------------------
Got: FFRR 2007 TDV8 Stornaway
Nissan 350z
GSXR1000 K5
CBR1100xx
XR400
Had:
Jag XF
Merc E320
Volvo XC90

.....and a blackbird and a Gixxer in the garage you'll always think a 3 tonner is slow

My TDV6 was worth every penny of the £550 it cost, but I remain reserved on the FFRR. To be honest I am unsure I'll go ahead but I will continue with some research.

I'm looking for low end grunt for towing and mid range overtaking. Is this where I put the car details and a bit about myself ?........