'97 Passat TDI Build

[Caddylackn]

Originally Posted by freebeard

It gets you to a sweet spot in BSFC chart. ecomodder.com/wiki/Brake_Specific_Fuel_Consumption_(BSFC)_Maps

Any benefit 'shrinks' with the length of the journey.

Introducing the turbo complicates things.

Unfortunately I can't download the table/chart/graph . It doesn't take my login. They also don't have the 1.9L 1Z motor chart just the 1.9 AHU. It should be close though.

I was afraid that quick acceleration would bring in too much boost and fuel. Eventually I will find a happy medium. I can also go in with a VAG COM and laptop and try to reduce the fuel injection length pulses. Been ten years since i have tried to tune with a VAG COM.

As a rule of thumb, your max. effeciency should be near your peak torque, provided that is not too high in the rpm band where there are more friction losses. My peak torque (stock) is only at 1,900 rpms so I would say that 1,600 - 2,100 rpms would be my driving range. Somewhere in here is my sweet spot. Trial and error will find it.

Unfortunately since I have the 0.681 5th gear mod, I have a large gap now between 4th and 5th gear. It is hard to use 5th gear at 50 mph unless it is level or downhill, and in 4th gear at 50 mph steady, my instantaneous mpg is only 50 mpg or so on level. I have about 6 miles of driving at 45 - 50 mph on my commute and I have been doing that in 5th. I should try some P&G in 4th and compare to P&G in 5th.

[Caddylackn]

To fix my constant heat on problem, I had to get to my heater control panel and adjust the cable (it slipped). I added some epoxy to keep it from slipping as the heater control cable is not routed correctly and is under tension when everything is put back together. Turning it to full cold caused the cable to slip on the clip fastener. The epoxy will hopefully keep it from slipping. I was able to get at least the #2 fan speed to work. I keep it on Cold. Haven't tried to switch it to hot yet, then back to cold.

The A/C works great now. I was able to buy some cans of R134a in Idaho, and added R134a until it was full and at recommended max high pressure range.

Driving at 65 mph up to 70 mph to work and back I have been getting this mpg this week:

mpg To work:-----mgp from work:
62.9---------------52 (with errands and extra stops)
63.3---------------58.6 (windy)
65.0---------------61.7
63.7---------------
I still coasted this week, but only the long sustained coasts. So 55-60 mph (right lane) commuting saves about 3 - 4 mpg on average than 65 -70 mph (left lane) commuting or about a 5% savings in fuel. So about a $1 savings per week in diesel if my math is right. I will just keep it at 65 mph for now.

Traffic has not been a factor so far.

[Caddylackn]

My gas mileage has been steadily creeping down. Every time I refill, I find my Scan Gauge II is off by 10% (used 10% more diesel than gauge estimates). This is with 4 calibrations now. So, four times I corrected the fuel used and recalibrated the Scan gauge

I believe my old injector nozzles are worn out (they are chinese knock offs I bought on Ebay ten years ago). My idle is rough and I was getting black smoke on any moderate acceleration on a hill. I believe my nozzles are leaking fuel, which is why my Scan Gauge is underestimating the amount of fuel used.

I replaced my nozzles this weekend with new Bosio 520 DLC nozzles. Right away my rough idle cleared up and I have much less vibration driving. So I probably had at least one injector leaking. Two were real sooty when I pulled them out. I did not adjust timing or adjust fuel with the Vag COM yet.

I will fill up after the end of the week and recalibrate, again. Hopefully my gas mileage goes up.

[Piwoslaw]

Originally Posted by Caddylackn

My gas mileage has been steadily creeping down. Every time I refill, I find my Scan Gauge II is off by 10% (used 10% more diesel than gauge estimates). This is with 4 calibrations now. So, four times I corrected the fuel used and recalibrated the Scan gauge

Just to confirm: When you calibrate, you "undershoot" the correction by half? For example, if it was 10% under, then you add only 5%, etc.

Originally Posted by Caddylackn

and I was getting black smoke on any moderate acceleration on a hill.

Black smoke while accelerating could also be if you are leaking compressed air somewhere between the turbo and the intake manifold. If replacing the injectors doesn't clear that up, then you should check for loose air hoses.

[Caddylackn]

When I fill up, I use the fill command setting on the Scan Gauge II. It will show the projected fill up of 5.5 gallons (for example) based on the last calibrations, when it actually took 6.0 gallons to fill. I use the buttons to adjust it to the correct 6.0 gallons at fill up. This is supposed to calibrate the instantaneous fuel usage. I have now done this four times.

Before I did any fillup calibration, I was off by over 30% of the projected fill up amount.
The computer counts injector pulses, and the injector pulse duration is set with the Vag Com and is known. So, if I am over 10% off on fuel usage, I think it is from leaking fuel injector nozzles. The old nozzle tips do look a little worn. New fill ups will tell if I am correct in my assumption.

the black smoke was only on acceleration. It should have some black smoke on hard acceleration (I have larger nozzles and a tune), but it was smoking on even slight acceleration on hills. This seems to have cleared up with the new Bosio nozzles. I haven't done any hard acceleration yet. .

My boost pressure seems normal. It makes about 10 psi on hard acceleration and 2 to 5 psi on cruise depending on the grade. I haven't checked it when I have floored it for extended periods. I will check the pressure side intake for leaks.

[Caddylackn]

I finally have my Scan Gauge II calibrated correctly. With my new injector nozzles, I was able to calibrate it correctly to match my fill-up gas mileage calculations. My old injectors leaked so I could never converge on calibration the Scan Gauge II correctly.

Fall hit along with heavy rains and wind. It seems that the effect of rain is about a 8% - 10% hit in gas mileage reduction. Here are my last week's mileage numbers with the new Bosio DLC 250 injector nozzles. 60 - 63 mph average commute driving 35 miles each way.

day--------to work(mpg)--to home(mpg)--daily average--notes
10/31-----50.8------------52.7-------------51.75-----------heavy traffic home
11/1-------55.6-----------56.1--------------55.85-----------Daily record high
11/2-------50.6-----------55.5--------------53.05------------ -
11/3-------51.8-----------51.6--------------51.7------------ -
11/4-------50.3-----------57.3--------------53.8------------ gusty tailwind home


I didn't record which days had rain, but those appear to be the 50 mpg trips. Morning mileage is worse, as it gas mileage takes a big hit until the car warms up. This year tdi has a coolant heater that draws about 80 amps to get the coolant up to temp for emissions. It takes big draw on the alternator and a big parasitic draw on the motor. When I start the car it is running at 0.27 gph at idle when cold for about 5 miles. When it is fully warmed up at idle it is 0.16 gph - 0.17 gph, so the parasitic effect of the alternator draw is obvious. I shoot for 1.0 gph on level ground while driving (60 mpg) so the alternator draw is about 0.1 gph or a 10% reduction in gas mileage.

I had some wastegate or boost leak problems this week. I lost boost going up a hill, then regained it, then noticed boost pressure being about 2 psi higher during cruising speed. So, maybe a waste gate issue or boost control? Or a boost leak fixed? or a boost leak created? Going to check the intake tubing today. I used to cruise on level ground at around 16 to 17 psi (absolute pressure). Now it is about 18- 19 psi (absolute pressure or MAP), but gas mileage is the same. I am now going to do the famous Italian TDI tune up every day at least once to keep the waste gate from carboning up and sticking. A full throttle short run everyday to keep the carbon away.....

[Caddylackn]

Update:

I stupidly removed my battery cable last weekend and lost my last fillup mileage, so I couldn't calculate my last tank gas mileage when I filled up. There was at least 600 miles on the odo. My daily mileage commuting readings for the last month were all over 50 mpg, some around 55 mpg. I hit a best of 57 mpg one way 35 mile commute. Lowest trips around 48 -49 mpg in the pouring rain or a trip with a bad traffic snarl. The weather has been cold; mid 30s to low 40s consistently. It takes about 10 miles of driving for my car to warm up and turn off the coolant electric heaters. These draw about 60 - 70 amps, so a big alternator and power draw and associated gas mileage reduction. I have considered doing the fuel temp mod, which tricks the computer to thinking the motor is warm and turn off cold enrichment.

Last month, I did a 90% upper grill block and saw about a 2 mpg gain. Only the VW logo now is not blocked. The only air that gets through is around the letters. The upper grill area is so small on a passat that I didn't think I would see much or any gain difference with blocking it. I can tell the difference when coasting, I picked up a few mph on hills I always coast down. I will fill up this upcoming week and I should see the gas mileage average go up a little.

To Do:
1 .I need to fix my rear window wiper. My rear window spoiler basically prevents any rain from cleaning my rear window, so it gets dirty and hard to see out of.

2. I only have one heater fan speed, speed 2 of the 4 speeds. Not enough to get great defrost or heat until about halfway through my commute. I used to get speeds 1, 3, 4 until I did my complete dash teardown and gut out to replace the heater core. Now I got the opposite of what I had, so maybe I have a wire switched?

3. I may put some studded tires on for winter, and remove my rear wheel covers. This winter has been pretty snowy so far. I can drive my crown vic with studless tires and expect about 18 - 19 mpg on my commute.

4. Looking for some cheap used passat headlights to convert to led projectors. I would convert my original ones, but the aiming plastic gear mechanism is stripped on one, and I like the idea of completing these headlights before swapping in case I ruin one in my conversion. I am not stuck with no headlight until I find another one. I have done two other headlight projector and led conversions. My bronco, and my crown vic. Major vision improvements without blinding drivers. The passat stock headlights suck b_lls. Poor light distribution and cloudy plastic lenses that get microcracks and the projector chrome surface degrades. There are no real options to buy new headlights without spending about $500 on european Hellas. Even these Hellas are becoming hens teeth.

The headlight projector retrofit consist of baking the stock headlight in the oven at 300 deg. F for about 1/2 hour to soften the urethane glue to remove (prying off) the lens cover. Then put in the new H1 projector housings from the front using the factory bulb hole, and try to align the new projector to the same focal point so it can be aimed correctly. I put the bulb in with temp wiring and fire it up with the headlight level and see where it falls. Usually spinning the housing will get it correct. Then tighten and seal the projector housing, then put the original lens back on, or make a new lens cover out of lexan. Cut the lexan, then bake it in the oven at 300 def F, after placing on top of the old cover. It will then bend to the correct contour of the stock cover in the oven. Then epoxy, or urethane seal the new lens on. Then make a wiring conversion harness to use the new H1 LED lights from the stock headlight connector. Then install and aim after sealing the edges well where the lens attaches to the housing so water doesn't get in.

[Caddylackn]

I got some new mods and finally fixed one of my engine issues. I will be posting my upgrades with photos shortly.

My gas mileage went down slightly after my aeromods.

I dialed my Injection Quantity down but have been fighting engine codes and the dreaded flashing glow plug light for the last few months.

Replacing my MAF last week helped get my gas mileage back up (on daily trips) but still throwing the 01246 code. I do have air bubbles in the fuel line and will have to replace fuel lines until that is fixed to rule that out. My TDI doesn't use a lift pump so the Injection Pump sucks all the way from the gas tank. Any cracks in the line or fittings will let bubbles in. I replaced the thermoplastic Tee o-ring. Fuel filter only has 5k miles on it.

[Piotrsko]

A related known issue with F250 7.3's is that the fuel pickup is too close to the return line and that #2 diesel entraps air for a short while worse in the heat of summer. Reformulation of #2 has caused this problem. Makes #8 injector cackle because it's at the dead end of the fuel rail.

You might have good fuel lines but crap fuel

[Caddylackn]

Finally posting my previous mods.

I removed my temporary spoiler and replaced it with a steel one. It was a ford pick up hood . I just used the skin. Sheet metal is so pricey now, I picked this hood on craigslist for $20 and have plenty of steel left over.

Old:
https://forums.tdiclub.com/data/xfmg...jpg?1686599834

New:
https://forums.tdiclub.com/data/xfmg...jpg?1686599832

https://forums.tdiclub.com/data/xfmg...jpg?1686599831

It is fully welded and bondo'ed. Not really that much filler.