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TDI Fuel Economy Discussions about increasing the fuel economy of your TDI engine. Non TDI related postings will be moved or removed.

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Old February 16th, 2018, 10:49   #1
thompsoncustom
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Default Injection pump and injection pressure mods for MPG?

Wondering who has played with their injection pump and increased MPG. Ive been thinking lately that advancing the injection pump timing and increasing pressure at thw injectors could both increase mileage.

Wondering what you guys thought?

Btw my car is a 02 Bora sport edtion

Last edited by thompsoncustom; February 16th, 2018 at 11:08.
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Old February 16th, 2018, 12:40   #2
IndigoBlueWagon
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Above 1600 RPM pump timing is managed by the ECU. You can advance pump timing mechanically, which will help cold starts and make sure the entire range of timing is available to the computer. Short of installing a higher pressure pump, there isn't a way I know of to increase pump pressure.

Best way to improve FE is to make sure everything is working properly in your car and then adapt your driving habits to improve FE.
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Old February 17th, 2018, 06:11   #3
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Thanks been out of the hypermiling game for awhile but years ago i modifyed a 3 cylinder geo metro xfi and got above 65mpg so i think ive still got the driving part under control along with aerodynamics.

Nozzle size and number of holes should change pressure. Any idea on which injector nozzle are best for FE.

The diesel thing is new to me but i fell that if pressure at the injector could be increased vaporization of the fuel should be better. Thanks for the info on the pump timing above 1600rpm looks like i would need some kind of computer program to modify the ecu to change timing.

I should also add that my 02 is a automatic not a manual unfortunately but i think i read that the autos have a bigger injection pump.

Last edited by thompsoncustom; February 17th, 2018 at 07:15.
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Old February 17th, 2018, 10:10   #4
Vince Waldon
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Quote:
Originally Posted by thompsoncustom View Post
I should also add that my 02 is a automatic
The auto IP does have a larger plunger (11mm as opposed to 10) but the auto nozzles are re-sized accordingly, so it's a wash really.

Just my opinion, and doesn't answer your question, but most folks will agree any micro-improvements in FE you might be able to make tweaking fuel pressure/nozzles/timing (that VW hasn't already long since evaluated and either implemented or rejected) are likely a drop in the bucket compared to the penalty you're paying for having an automatic transmission, and any improves will suffer the same dilution.
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Old February 22nd, 2018, 05:48   #5
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I totally agree that the auto trannys hurts me more than anything else and its on its way out so when it dies it will get replaced with a manual. But in till then idk like to do everything possible to increase my mpg as much as possible.
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Old February 22nd, 2018, 07:37   #6
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After a good hot thermostat, alignment and correct tire pressures, there really isn't much else to mention other than tight control of your right foot. Because gasoline engines have a very narrow air/fuel ratio (14:1) window where they will produce power, diesels produce power all the way down to 80:1 air to fuel ratio.
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Old February 25th, 2018, 18:35   #7
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Quote:
Originally Posted by IndigoBlueWagon View Post
Above 1600 RPM pump timing is managed by the ECU.
at all speeds it is controlled by ECU
there is no rpm dependant timing curve on the computer governed VP pumps, it is 100% controlled by the cold start solenoid

On the nozzles, I got the same fuel mileage running stock manual nozzles, to pp764, to DSS-R .360 with a 12mm/de110 pump
The bigger ones just got there a lot faster. Tells me that the shorter injection duration is worth a lot more for fuel economy than any gains people tout about smaller nozzles spraying finer streams.

42 with stock ECU maps, 48 with advanced timing maps and more fuel in the smoke maps

Last edited by [486]; February 25th, 2018 at 18:37.
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Old February 26th, 2018, 07:24   #8
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486, I agree good FE can be achieved with using "big" nozzles; two weeks ago I might not have agreed though... I am running the gear to make a fair amount of HP, and I had my tuner re-write my tune to increase my FE. As close as I can calculate right now, my FE is up 16% and I still have plenty of power available at WOT if needed.
To the OP, I suggest you get a mild tune and .205 nozzles; this gives you the best of both worlds so-to-speak, for a minimum investment.
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Old February 26th, 2018, 20:29   #9
[486]
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Quote:
Originally Posted by Nevada_TDI View Post
I had my tuner re-write my tune to increase my FE.
Mine was very poorly tuned when I had it together last.

Probably still be when I get it together again.
I hate smoke, but I'm far too lazy to plug in my computer and reflash the junk the ten or so times it seems to take me to get it running decent without too much black. :\

Still somewhat shocking to me how it still made the same MPG, despite a lot more smoke (and speed).

Last edited by [486]; February 26th, 2018 at 20:33.
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Old February 28th, 2018, 09:01   #10
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Originally Posted by hichamaziz View Post
You can advance pump timing mechanically
optimal timing is something like 8 degrees at 70 mph cruise (plus or minus five, depending on how big your nozzles are)

set your static timing to that and the computer sets trouble codes, unless you disable them in the .bin
and you're just running the stock timing map, clipped to bottom out the advance piston anywhere it requests less than your static timing
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Old March 1st, 2018, 17:29   #11
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Quote:
Originally Posted by hichamaziz View Post
You can advance pump timing mechanically
optimal timing is something like 8 degrees at 70 mph cruise (plus or minus five, depending on how big your nozzles are)
set your static timing to that and the computer sets trouble codes, unless you disable them in the .bin
and you're just running the stock timing map, clipped to bottom out the advance piston anywhere it requests less than your static timing
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Old March 3rd, 2018, 17:15   #12
thompsoncustom
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I need to pull my injectors and see what I have for nozzles. I'm also looking at getting VCDS to play around with timing adaptation. With VCDS can I do all my timing changes there or should they be done manually or both?

I read somewhere on here that a 205 degree thermostat can also help increase fuel economy. Thoughts?
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Old March 8th, 2018, 05:41   #13
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Ditch the auto now, you are loosing 25% right there. I owned both for many many years, it is simply amazing how much fuel the transmission costs...
Autos should have the 0.154 nozzles and an 11mm pump. Verify, as the years go by someone may have changed stuff-the pump has a bosch id plate with long numbers and the nozzles will have a stamping inside the injector body. Clean the intake, make sure the VNT is working properly on the turbo and good vacuum hoses through out the system. You could get a bigger pump head (12mm) and keep the small nozzles so it really pushes fuel but be aware it will put more stress on the timing belt.
You can run the timing advanced, near the top end of the graph. You might have to play with the timing belt depending on where it is positioned on the injection pump sprocket, sometimes there is not enough range to get it where you want and off a tooth for max timing.
18 years into our automatic tdi, best tank was 750 miles running I-81/66/95 down to Florida 24 hour trip non stop. I drafted, I did not use a/c and kept the windows up just vented with the sunroof. I was never able to repeat it, the next best was usually 650-675 with normal commuting tanks around 550.
With a manual trans I was into 800 easy commuting, higher on trips.
Scangauge or similar bluetooth apps give lots of info like TPS, load, temps, all handy to know for max mpg. We run ours at 1/3 throttle for max mpg.
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Old March 8th, 2018, 07:48   #14
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Quote:
Originally Posted by clacker View Post
...
With a manual trans I was into 800 easy commuting, higher on trips.
Scangauge or similar bluetooth apps give lots of info like TPS, load, temps, all handy to know for max mpg. We run ours at 1/3 throttle for max mpg.
Throttle?
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Old March 8th, 2018, 15:24   #15
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On the scangauge running 30-35% TPS (throttle position sensor). It would shift at the minimum rpms that way and hit around 60mph pretty easy unless rain or a head wind.
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