It was previously stated -- the MAF is used to monitor and regulate the EGR. When more exhaust is routed into the intake, the MAF reading is expected to drop.

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'05 Liberty CRD B100, SEGR - SOLD

'01 Beetle TDi B100, EGR delete
'83 Mercedes 240D B100, no EGR

--- SEGR Builder ---

So the reading the MAF sends to the ECM that's all it uses that signal for is EGR operation? Sounds stupid.

_________________
Ryan
2006 Ford F-250 PSD CC FX4
**GONE**
2005 Jeep Liberty CRD
SAMCO Hoses//GDE Tune//PML Trans Pan//TransGo HD Shift Kit//MBRP Exhaust

1986 2R Mustang SVO

Blame the EPA

_________________
05CRD: GDE Hot ECU & TCM tunes, Provent, Cat filter, Facet lift pump, TransGo kit, Florida TC, Samcos, stainless brake lines, HDS thermostat, Renegade light bar,
RL super sliders, Bilstein adjustables, Al's Gen 4.5 Arms, 235/85-16 Duratracs, DTT rear, Elocker front, EVIC+TPMS, Turbo timer, McNally pillar gauges, Weeks Stage II kit.

That is not 'all it's used for' as stated above. I monitored in Vag-Com the performance of my engine with both the MAF connected and disconnected on my VW TDI. Our CRD engines are very similar in how they operate, with regard to this function - Both have MAF, MAP, and VNT turbos.

Let me quash the 'epa only' idea first. The engine needs to know how much air it has to work with, so that it can maximize the fuel input. This is PARTLY for the epa, but more to ensure that there is not an overabundance of fuel, OR a too-lean condition. The economy of the Jetta would drop like a rock when the MAF was out and the car was set on a default value of 550 mg/r of air. The proper range of an operating MAF on that car was between 180 and 880 mg/r, from idle to WOT. With the MAF working properly, the car had insane amounts of power available, b/c it was matching the fueling maps to the available air.

*IF* the map is working to it's fullest, then our CRDs might just feel a bit more zippy than we have now. I will investigate this further on my own car, and report back. I strongly suspect that it will have a great effect in the available power and economy.

Dammit man, if I hear you compare a Jeep to a VW again I am going to go apeshit.

Ya the engine needs to know how much air in coming in, hence the MAP. There are many engine management systems that use only MAP sensors, Jeep included.

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http://www.Colorado4Wheel.com
"Its not about what you can DO with your Jeep, its about where you can GO with your Jeep."
Knowledgeable - But Caustic

Not that I care that much, but why do folks get their panties in a bunch over comparing one piece of late 90's European diesel technology (the VM Motori used in our CRD's) with the pre-pump duese diesels from VW? Bit of a head scratcher to me as to why folks like to compare our 2.8 and the older 2.5 VM's to the 5.9 Cummins developed in the early 1980's, but not to the 1.9. 2.0, or 2.5 TDI's designed and sold on the same continent during the same time period.

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2006 Liberty CRD Limited
Mopar engine, transmission, transfer case skids
245/70/16 Michelin Latitude X-Ice (winter)
235/75/16 Firestone Destination ATs (summer)
Thule roof rack, cargo box
V6 airbox mod
Flowmaster 50 2.5 inch muffler
Edge EZ module (set for fuel economy)
SEGR
TDIWagonGuy CCV filter
B99 (summer), B20 (winter)

Exactly. Our VM engine IS closer to the 1999-2003 VE-pump TDI engines than it is to the PD (weird design) or the even older VM stuff. Cummins is just different, no comparison in the engine.

But lets be reasonable here: For the purposes of this discussion, the engines are similar. The fuel is managed by the ECM, pressurized fuel is provided by the pump, and metered by the opening of the injectors. It doesn't change anything for this discussion, that the injectors are controlled IN the pump on the VW, or on the injector itself for the CRD.

We both have a VNT (the same one, I think) and both have EGR problems, MAF problems, and MAP sensors. So the difference is how they are used. No need to get huffy about it, right?

well hells bells, your doing apples and oranges still.

I don't care what VW does for their engine management, this Jeep is not a VAG.

Also, don't you think our US CRD is a little closer to the 2002-2004 KJ than a 1999-2003 VAG?

My point is just because one thing is true for a VW, doesn't mean its true for a Jeep. Sure basic principles carry over, but just because my Cherokee doesn't use a MAF doesn't mean a VW shouldn't need one.

By the same logic just because a Nissan ZD30 engine doesn't use a MAF and only uses a MAP doesn't mean a Jeep or VW uses one. Ya sure the ZD engine is a 3L common rail direct injected DOHC engine. But that doesn't mean ANYTHING about its engine management logic can be applied to our CRD.

_________________
http://www.Colorado4Wheel.com
"Its not about what you can DO with your Jeep, its about where you can GO with your Jeep."
Knowledgeable - But Caustic

These statements don't make sense for a diesel engine. Especially one that uses MAP based fueling.

_________________
05CRD: GDE Hot ECU & TCM tunes, Provent, Cat filter, Facet lift pump, TransGo kit, Florida TC, Samcos, stainless brake lines, HDS thermostat, Renegade light bar,
RL super sliders, Bilstein adjustables, Al's Gen 4.5 Arms, 235/85-16 Duratracs, DTT rear, Elocker front, EVIC+TPMS, Turbo timer, McNally pillar gauges, Weeks Stage II kit.

Dammit man, if I hear you compare apples to oranges again I'm gonna...

Come on now! Apples and oranges are both fruit!
That grow on trees.
That have a peel.
That can be turned into juice.
Both have seeds.
Both make a tasty snack.
And best of all, both can be easily thrown at someone.

Sorry man, couldn't resist.

_________________
U.S. Army Retired

I towed a vehicle on a u-haul trailer (total weight of ~5000lbs) from Florida to Pennsylvania and averaged a consistent 18mpg with my CRD over the trip. It towed fantastic- usually forgot that the trailer and car were even attached. My mileage on the trip from PA to FL was ~26mpg, so the trailer/car took about 8mpg off, which is about what I expected to happen.

This is a pretty entertaining thread folks...

So here's my mileage experience (I live in central FL). Running dino diesel I was getting 29-30 mpg highway, 25 in mixed driving. I claim to be an average driver...70-75 highway, not too quick off the line, but keeping up with most others. I switched to B20 about January and my highway mileage dropped to 27-28, occasionally 29 mpg. My mixed average dropped to 24. After I switched to B99, getting 26 highway, 23 for a mixed average. I installed the SEGR end of May (IIRC) and no change in mileage. My CRD is stock other than the SEGR....still running the factory tires at about 42K miles (but not much longer).

I'm heading up to NY soon and that's when I calculate my highway mileage most accurately. For some reason I usually get better mileage in the hilly states than I do in FL. And this is using the GPS/fillup measuring method, not the evic, although my evic has always come out pretty close to my calc.

My point is there are pretty significant variations in mileage possible with fuel types, driving styles, and so forth. Maybe this guy had a tail wind and the rover acted like a sail. We have had some pretty good T-storms over the past few weeks.

_________________
2006 CRD Limited
SEGR Mod
Saikou Michi Condenser -- Deleted
Samco Hose Kit
Fumoto 102
Etecno1 GX3123 Steel 7V Glow Plugs
GDE FT Eco and Hot Tunes
JBA 4.5 UCAs
OME Lift

My findings exactly In 2 different TDI's over several years on round trips to Florida from Ohio and back I got my best fuel mileage on both cars with fuel puchashed in Northern Florida and Gerogia On the last trip back with my 99.5 jetta I averaged for two tanks in a row OVER 70 MPG Conditions were perfect, cool night damp air, no AC, constant 70 mph but the fuel is a really big wild card I always calculate my mileage by hand and two tanks in a row rules out over/under filling so they were honest figures My overall mileage for 114k miles on that car were 49.6 mpg, my son ownes it now. Both my parents have died so I have not made the trip with my CRD Here in Central Ohio we get the rot gut diesel of the world

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Atlantic Blue 06 CRD Limited (his)
Joined by a 2000 XJ Classic (hers)

Wait a second.

The TDI (US) is an 8 valve motor.

Isn't the VM 2.8 a 16-valve? ( http://www.vmmotori.it/en/01/01/dettAut ... ?autoId=53 )

That alone makes them different in design.... I own a PD (pump dusse/unit injector) TDI, and given the current driving needs I'm likely swapping out for the other half's Liberty CRD for the remainder of the summer. The TDI just does better in the city with a lead foot, and I drive 25 miles to work -- 15 of which are highway. The CRD should get its best (hoping 27mpg) with me, where its geting 20-22mpg in the city right now with AC use and a lead footer who takes it to 4k/rpm constantly.

I don't compare the two engines; the TDI is a different animal from the VM. The VM I feel is more old school, with more valves and I'd even say may be designed better than the VW motor. Time will tell for that one. However I don't think its wrong to compare them; but it's hard to compare 1.9L to 2.8L -- 8 valves to 16 valves -- etc, etc.

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1998 VW New Beetle TDI & 2006 Jetta TDI Manual
No more: 2005 Stone White Liberty CRD
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