scary fuel increase

[andyleaves]

I have a hole starting in the larger of the two exhaust flexes (6a13 ohc - v6-24), and I have changed the standard air box for a cone filter mounted onto the MAF and have a funnel type thing to bring cold air direct to it...

The car now sounds err! very D A M N loud in fact it sounds like a V6 should gutsy...

However would these two factors suddenly increase my fuel useage from about 380 miles from a tank to about 300 miles maybe a little less out of a tank?

About ready to swap the cone back out, cant do with that kind of fuel usage increase and not really much more grunt.

[Turbo_Steve]

Yep...your lambda sensor will be reading lean, so the engine will overfuel.
Air in the exhaust is very bad for fuel economy.

[Davezj]

you can do a temp fix on the flex section.

consisting of gungum, jubalee clip x4, steel (not ally) 440ml or 500ml bear can (empty, you can drink it).

cut both ends off the bear can and you have a perfectly formed exhaust patch.

loads of gungum on flex section, put bear can patch on and secure with clips. this should plug the hole until you can source new downpipes.

i have Kronenbourg 1664 downpipes at the moment so i know this works.

[bradc]

The pod will be screwing things up too, take it out and burn it. Then reinstall the normal airbox

[andyleaves]

Steve, Brad, did it at 08.00 this morning, sounds a bit better all ready...

Davezj, I like the idea better than what I did, I actually went to Halfords and bought a silencer wrap, to do pretty much the same thing, but I prefer the 1664 version, very nice.

Love it, sounds like a cooking recipie...

[Dom B]

The fuel increase could be the v6 sound syndrome, every time you pass an acoustically reflective surface you feel compelled to wind the windows down and give it the gas lol.

Seriously though i put a double cone filter in my alfa in a proper cold air box the did a bunch of porting of the intake system and TB etc, sounds fabulous really puts a smile on your face when driving but i actually gained a clear 2 mpg. Not saying a lot as it was only from 25mpg average to 27 over several tanks but it was a definite increase.

[Turbo_Steve]

Which is great, and something we're looking into as a club: the main problem is that all the piping has to be fabricated to stabilize the MAF flow...these are so stupidly sensitive to the flow pattern. The joys of the oscillating mirror design.

A lot of expense, but definitely worth the results if you're prepared to do the research.

[andyleaves]

Well i've put the standard air box back on, as stated and spent a good hour or so under the car yesterday sorting the flex out.

Shed loads of Gun Gum, and two holts silencer wraps...
Gonna take it out a bit later, and have a good listen see if I still have that horrid hole in exhaust noise type thingymajig...

Steve has any one managed this yet? (MAF & Air pattern?)

what about things like injen systems?
Could we not swap the maf from a diff motor (Just a thought)

[Turbo_Steve]

AlanDITD has already had some good results with a few bits of pipe and a normal cone filter.

Swinks and Confused have both fitted CDA carbon units, which are an enclosed airfilter with feed pipe...they've had some issues, but seem to have resolved most of them. Whether or not their MAF is reading accurately isn't going to show up unless they do a whole lot of EvoScan logging, or some before/after dyno runs.

Swapping the MAF will require a replacement ECU - this engine uses a frequmcy based input, where most use a voltage based input.

Even if that wasn't the case, the MAF scaling table in the ECU would usually need to be reprogrammed anyway.

[andyleaves]

Well now...
Went for a little drive on the erm!!! private runway today filled up at the begining of the trip (Really filled up) costed the car for 73 miles hitting around 70 - 90 on average, hit 115 at one point , newho the needle is now sitting just below the full mark on the gauge.

Does that sound about right to the rest of you?

[aboo]

Sorry for the tread hijack but since I did the RPW downpipe & decat upgrade & new dump valve I'm only getting about 17 miles to the gallon.

Do I have a problem?

[andyleaves]

Aboo actually that seems to be about right but then...
If your exhaling more waste, or rather getting rid of it quicker, then it would make more sense that you would use more fuel...
After looking back at my figures I was actually getting 240 miles form a full tank, now that is fuel usage.

[Turbo_Steve]

Sorry for the tread hijack but since I did the RPW downpipe & decat upgrade & new dump valve I'm only getting about 17 miles to the gallon.

Depends how you're driving it! - If you're using more throttle, then it's probably about right.

However, if you're cruising, it probably means you have a leak in the exhaust causing your lambda sensor to see oxygen and run the car rich.

[bradc]

Or the bov might be set up badly?

[Turbo_Steve]

True: What kind of Dumpvalve is it, a Recirc or a VTA?

[aboo]

VTA Steve & its if I'm cruising or with full throttle. It may be the exhuast as I think the centre sections on its way out.

[ANTHONY]

still on the high-jack theme would a decat increase the fuel consumption

[andyleaves]

I would have thought so, on any car...
But then I might be wrong.

[Turbo_Steve]

actually, many people find a decat saves them fuel, as they have more power for less throttle, so can cruise with less load = less fuel

[andyleaves]

Would that work with a sports cat then?