I am assuming the electronics have got very confused (I hope they have) as since switching to the K&N air filter my MPG has plummeted to 13 or 14 MPG where it was at 20 with the actors setup.

Any clues as to what it's doing? The fuel gauge does not agree with the new low MPG.

- Simon "On first name terms with my local Dealer......now."

'61 Plate 5.0SC Autobiography - in Black ——— Gone
'53 plate 4.4V8 Vogue Bonatti Grey inside and out. ----- Gone

Do you mean replacement filter, or you've fitted a cone filter? In which case what have you done about the secondary air injection system? Also, how have you ensured it's sucking in cold air, rather than hot engine bay air? Compromising either of these systems will give you poor fuel economy. 

@dan - what do you suggest one does - i bought vehicle with k&n cone air filter due to 2006 facelift done on 2004 v8; should i try and put in a cold air intake or not

Was the battery disconnected at any point ? Stolen / Gone: 2006MY Supercharged LPG Autobiography - Zambezi Silver with Sand/Jet/Jet Oxford Leather.....

I have fitted a cone filter yes and all I have done for now is locate the filter at the end of the tube where the old filter was located. "On first name terms with my local Dealer......now."

'61 Plate 5.0SC Autobiography - in Black ——— Gone
'53 plate 4.4V8 Vogue Bonatti Grey inside and out. ----- Gone

It might be worth confirming your MPG figures with a brim to brim test. Just to see whether it's giving you incorrect information... 

Cone filters can have an adverse effect on the engine performance. Years ago I fitted my Suz GS1000 with cones directly on the carbs. After a lot of tinkering with the jets, I finally got the mixture right. It didn't have its full "workable" torque range though.

After talking to a Porsche race tuner, they left the original air box in place, just used a low resistance filter element and spent all their time and money on making the inlet tract smooth as, to improve laminar flow into the engine as the cones make the airflow turbulent, reducing the amount of air going in.

When I returned the Suz to the standard housing, I noticed it actually ran better.

Now MPG, assuming your air flow is more turbulent than before, to get the same performance out of the car, you need to give it a bit more welly to get it going, i.e. increasing the fuel consumption.

I fitted a replacement K&N in my car and notice no difference (not that I was looking for any, I just won't pay the ridiculous prices for paper air filters they charge here (more than a K&N filter !!)).

I suggest that you go back to standard and enjoy "normal" MPG.

On measurements, as far as I know the fuel consumption is calculated on the estimated amount of petrol being injected. Accuracy is about 10% according to my source, which is confirmed by my own brim to brim measurement.

I assume you "zeroed" the MPG counters in the computer after installing the new filter ? MY 2010 5.0 SC Galway green and sand interior!!
Have the Faultmate MSV2 Extreme to be tinkering with the settings etc. !!

Yes I zero'd the mpg figures in the on board computer. The reason for the K&N install was that I will be doing a 2006 facelift shortly and wanted to get the filter bit done and out of the way. The choices as I see it are a) stick with the K&N and try to sort out what it's doing or b) do the mod I have read about to the original filter housing and go back to OEM layout.

Does anyone have pics of the mod to the air filter? "On first name terms with my local Dealer......now."

'61 Plate 5.0SC Autobiography - in Black ——— Gone
'53 plate 4.4V8 Vogue Bonatti Grey inside and out. ----- Gone

In my opinion, fitting a k&n filter or similar should have no effect on mpg on a standard fuel injected engine. the air flow meter monitors the volume of air entering the engine and the lambda sensors on the exhaust monitor the air/fuel mixture which will adjust the amount of fuel the ecu gives the engine therefore the engine should always be running at its optimum air/fuel ratio no matter what filter you have. the mpg difference is probably because you reset your mpg calculator. give it time to average itself out and i would imagine it would go back to the same. '04 td6 se
'63 land rover s2 200tdi
'04 mk indy kitcar bike engine

Are you sure your original mpg figures are correct 20 mpg sounds very good , the most I ever got out of mine was 18 mpg and that's driving like a Sunday driver with an egg under the throttle , normaly I get 16 at best 12 at worst  1990 3.5 v8 defender
2000 4.6 v8 30th anniversary prins lpg
2004 4.4 v8 vogue prins lpg
2011 4.4 TDV8 Vogue
faultmate extreme
rsw allcoms
Autel 906BT
Gap iiD tool

Fairly sure yes - regularly reset to check it - I do a lot of motorway miles in the FF averages out at about 19.1 and occasionally the long term average would be 17 if I'd done more trips around town.

I have found the K&N cold air intake kit used by some others but reluctant to spend yet more on the facelift so will be investigating the OEM air filter mod when I fit the new front end. "On first name terms with my local Dealer......now."

'61 Plate 5.0SC Autobiography - in Black ——— Gone
'53 plate 4.4V8 Vogue Bonatti Grey inside and out. ----- Gone

check out my post in this thread
http://www.fullfatrr.com/forum/topic16158.html  1990 3.5 v8 defender
2000 4.6 v8 30th anniversary prins lpg
2004 4.4 v8 vogue prins lpg
2011 4.4 TDV8 Vogue
faultmate extreme
rsw allcoms
Autel 906BT
Gap iiD tool

that was the mod I read about - did you ever take any pics of the result? "On first name terms with my local Dealer......now."

'61 Plate 5.0SC Autobiography - in Black ——— Gone
'53 plate 4.4V8 Vogue Bonatti Grey inside and out. ----- Gone

not sure i may have will have to check it out, as i said it can be done its very tight for space the air filter housing is easy the intake pipe from the inner wing is the bitch , on reflection i guess you could use some ali flexible duct which would be easier to shape  1990 3.5 v8 defender
2000 4.6 v8 30th anniversary prins lpg
2004 4.4 v8 vogue prins lpg
2011 4.4 TDV8 Vogue
faultmate extreme
rsw allcoms
Autel 906BT
Gap iiD tool

ebajema wrote:

Cone filters can have an adverse effect on the engine performance. Years ago I fitted my Suz GS1000 with cones directly on the carbs. After a lot of tinkering with the jets, I finally got the mixture right. It didn't have its full "workable" torque range though.

After talking to a Porsche race tuner, they left the original air box in place, just used a low resistance filter element and spent all their time and money on making the inlet tract smooth as, to improve laminar flow into the engine as the cones make the airflow turbulent, reducing the amount of air going in.

When I returned the Suz to the standard housing, I noticed it actually ran better.

Now MPG, assuming your air flow is more turbulent than before, to get the same performance out of the car, you need to give it a bit more welly to get it going, i.e. increasing the fuel consumption.

I fitted a replacement K&N in my car and notice no difference (not that I was looking for any, I just won't pay the ridiculous prices for paper air filters they charge here (more than a K&N filter !!)).

I suggest that you go back to standard and enjoy "normal" MPG.

On measurements, as far as I know the fuel consumption is calculated on the estimated amount of petrol being injected. Accuracy is about 10% according to my source, which is confirmed by my own brim to brim measurement.

I assume you "zeroed" the MPG counters in the computer after installing the new filter ?

Interesting what you say about smooth vs turbulent as the last thing you want when porting a cylinder head is a smooth mirror like tract, they are intentionally roughed up to improve air flow..........................think golf ball !!! One day your life will flash before your eyes......................................make sure yours is worth watching!