Improving mpg in Vw TDI

[Arragonis]

Originally Posted by MaxHedrm

The advantage of freer flowing air is that when you do request more power by dumping in more fuel you can get the air to burn it rather than just dumping it out the exhaust. So, you may not see a FE improvement, but you may see improved drivability.

Nope, this engine (the one in the Autospeed article) has all the air it needs already. Improving the flow in this case made no difference at all. Adding fuel (via the remap) added the power.

I have seen loads of postings on Skoda forums where people with my car (PD130) have fitted the PD160 intake and say things like "wow". But no A-B-A testing and no before / after dyno to back it up. The PD160 replica intake made as part of this article made no difference, in fact it went worse.

There is no agreed international calibration for the butt-o-meter

[Mario_Marques]

Originally Posted by NachtRitter

Same with mine... cleaning the intake made no difference in FE. What made a huge difference for me is getting updated nozzles / injectors. Could be because the old nozzles were not flowing as well, but putting new larger nozzles improved my freeway FE from ~28MPG to ~48MPG... huge difference!

I'm sure it wouldn't have made anywhere near as much difference if my current nozzles didn't have ~300K miles on them.

I think, it dependend on how clogged is your intake, egr and intercooler, it's very noticeable in performance when you clean all the intake in some cars(i'm talking only about diesel vw's).
About the 15", they are very light, the tires are thin, and i have a very long gearbox, with 17" i cant run at very low rpm's because the engine starts to choke(i dont know the corret word in english), with 15" i can run at 6gear, 1500rpm's and if i smash teh pedal the car goes to the front, no clutch vibration, no engine choking, feels very free and light, i can spin my wheels even in third gear if i full throttle
it's very noticeable the difference 17" vs 15"(i'm using audi a2 15" wheel).
I believe in car with short gearbox like tdi 110 you wont feel that kind of difference, to get the point, my 5th gear top down at about +/-210km/h(redline) and i still have another gear to run, i can run at 120km/h in 6th at +/-2000rpm's.
When you modify your intake you have to think like your car ecu, your car injects fuel vs maf readings, if you change your intake your maf readings will be different, sometimes you loose performance when you change your intake you have to know what your doing, and in a turbodiesel car, the turbo sucks the air, you dont need a "special racing intake"
I just mod my intake because i have to, i have no choice my car was a drag racing car, when i was using it to race i dont care about smoke, mileage etc, i just need a lot of air to burn a lot of fuel, as a street car, i care about the smoke, i care about the mileage, i'm very happy whit my street econo tune, very, very happy, but i know i can do even better, i have to try more ideas i have collected in this forum, and see if they work in my car, i'm not an engineering, i'm just a mechanic.

[MaxHedrm]

If you changed the rolling diameter of the tires your FE didn't go up as much as you think since the odometer thinks you are going further than you really are. Your speedometer is off too, luckily it reads faster than you are actually traveling, so you'll just get honked at and not get the police after you. :-D

[Mario_Marques]

Originally Posted by MaxHedrm

If you changed the rolling diameter of the tires your FE didn't go up as much as you think since the odometer thinks you are going further than you really are. Your speedometer is off too, luckily it reads faster than you are actually traveling, so you'll just get honked at and not get the police after you. :-D

By mario_marques at 2011-02-01


This is my 5th gear with 15" wheels(not at redline but close), i also have digital meter in my car and i know how to calc gear rations vs wheel ratio
I still have the sixth gear, i can set the speedometer in vag-com for 15", 16", 17" or 18" wheels.

[MaxHedrm]

Setting it for wheels is not the same as setting it for a different rolling circumference. But as long as you have tires that match one of those sizes you're good.

Did what Google earth said match your speedo? If not you have to include that percentage in all your calculations ... that seems like a lot of work every time you fill up.

[Mario_Marques]

Originally Posted by MaxHedrm

Setting it for wheels is not the same as setting it for a different rolling circumference. But as long as you have tires that match one of those sizes you're good.

Did what Google earth said match your speedo? If not you have to include that percentage in all your calculations ... that seems like a lot of work every time you fill up.

I'm sorry, i have to try to explain better, when i adjust the speedo, i set to the wheel diameter too, standard wheel and factory specified tyre to match that wheel (entire wheel diameter), so with 15" i can only use 195/65R15 tyres, with 16" 205/55R16, with 17" 225/45R17, with 18" 225/40R18.
My speedo reads about 208km/h, gps tracking(the google maps thing you see in the picture is actually my data from gps tracker) reads 204, my car digital speedo reads 203 almost like the gps, it's hard to know the perfect speed reading from the speedo needle(my speedo scale goes from 0km/h to 260km/h.
Usually i dont drive that way in the streets, it's only for test purpose, i always drive safe under speed limit & econo.

[MaxHedrm]

Just making sure. I've probably spent too much time on vwvortex where stuff like this is way over their heads.

[COcyclist]

Originally Posted by Mario_Marques

i dont recommend you to delete egr if you want good fuel consumption, deleting egr will increase your fuel consumption

Thanks Mario, I have been trying to find this out for myself due to problems with a U.S. EGR cooler recall. From what I can find it is better to leave the EGR intact for lowest fuel consumption.

[Mario_Marques]

Originally Posted by COcyclist

Thanks Mario, I have been trying to find this out for myself due to problems with a U.S. EGR cooler recall. From what I can find it is better to leave the EGR intact for lowest fuel consumption.

Is better to keep it clean instead of removing it.
Fuel consumption increases a little when you delete your egr because when egr is open, turbo pressure drops down & maf readings, maf is the "thing" who gives your car the information to inject more or less fuel, more air, more fuel.
You can see this by yourself in vag-com, you can do the egr test and see how it changes the amount of air into the engine, in this test you can also see how is your vnt turbo system working, my car doesent have egr, in cars without egr, this test dont work.
The negative side of having a egr is that your intake will get clogged, when this happen you will loose performance and your fuel consumption will increase, so the ideia is keep it clean.

[ConnClark]

Originally Posted by COcyclist

Thanks Mario, I have been trying to find this out for myself due to problems with a U.S. EGR cooler recall. From what I can find it is better to leave the EGR intact for lowest fuel consumption.

In most cases with a diesel engine elimination of EGR will increase mileage

http://www.iaeng.org/publication/WCE...p1548-1552.pdf

There are some exceptions to this but it takes just the right amount of EGR coordinated with the right injector timing to best approximate the ideal diesel cycle.