GET IN THERE 42.5 mpg in a LCR

Hang on...are the people quoting impressive MPG using the fuel computer or measuring it properly by filling the tank? After getting an indicated 60mpg from a 130PS TDCi Mondeo whilst actually achieving around 40mpg I don't believe them any more.
 
Jonnycoupe said:
Its does help air flow though.

How can the wastegate be fully open when its controlled by a pneumatic-mech actuator that is actuated by the intake manifold being pressurised to open it and limit boost.

Its closed, you get zero turbine bypass, shaft torque then churns a fair amount of air into the intake and reliveses some of the cylinder demands from the downstroke of the piston, hence reduced pumping losses = higher efficiency.
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I remain to be convinced on this. If the turbo is actualy shifting enough air to reduce MAP under cruise conditions, then the following will be true:

1) The turbine will be creating some back pressure, and hence increased pumping losses.
2) The additional airflow created by the compressor will drive an appropriate fuel correction (i.e. more fuel will be needed).

In the case of a normaly aspirated engine, simply opening the throttle a little will also reduce MAP and hence pumping losses, but has the advantages of a higher static CR (hence more of the fuel turned into useful energy) and no turbine in the exhaust path to increase pumping losses.
 
The airflow passing through the turbine is relatively low and its a small diameter throat so that helps draw air from the cylinders as theres a high speed region of air. Increasing the map will result in more power and the car with accelerate from cruise so thats not really the element at play, I thinks its just that the intake stroke has to do less intial work to pull air from the manifold and across throttle plate or maybe the later stage of intake where the turbo essential stablises the pressure differential across the throttle plate better than relying the on the vacuum from the pistons doing it.

As with the black art that is engines it all depends on a number of factors. For example a high power NA car at part throttle the large dia exhaust with low gas speed may present more backpressure than a nicely sized turbo with a similar amount of air passing through its turbine.
 
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Dogbreath said:
Hang on...are the people quoting impressive MPG using the fuel computer or measuring it properly by filling the tank? After getting an indicated 60mpg from a 130PS TDCi Mondeo whilst actually achieving around 40mpg I don't believe them any more.
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As I said, my trip computer seems to be +/- 1-2MPG out.
 
Simon said:
Nice work!

Do you like the engine though?
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It looks completely ridiculous in the engine bay, i had to get a magnifying glass to spot it, but yeah it drives very well and i love the high revs. I couldnt drive it every day to jobs as you really do have to be in the mood for the manual shifting and keeping it on the boil, but i have the low revving V8 merc for the boring stuff, this is a sunday afternoon thrasher really :)
 
[TW]Fox;11915443 said:
I don't think having a rusty G reg 3 Series in your garden thats not moved for 6 months really counts.
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cheeky sod

its rust free thank you very much and its in the driveway not the garden :)


muppet :)
 
[TW]Fox;11938660 said:
You are so slacking it took you 3 days to take that bait :p
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i've been busy buying old french cars :)

and recovering from the shock that it hasn't broke down yet :)
 
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