So, just bought my first TDI and I'm liking it. I've spent a bunch of time learning about the TDI and differences with gas and maintenance and on and on. I'm now wanting to maximize my FE and have some good experience getting 34mpg from my thirsty subaru outback. I'm currently trying to shift at about 2,000 RPM which is when the turbo really kicks in and kills FE, anyone find this to be the best shift point or have better for FE? I'm a little hesitant to FAS all the time like I did before (engine only on while accelerating) because I don't want to hurt the turbo. I know nothing about the turbos in the TDI and what they handle. I know on regular gas turbo the idea of turning the car of immediately after accelerating is a no-no. Do I need to let it idle awhile before I kill the engine? I started just letting it be in neutral since everyone was saying the TDI's sip fuel at idle, but apparently the PD engine in the '04 is different since my mostly calibrated gauge registers over .3 g/h when it's warm at idle. I know all the other techniques will work just like normal, but anyone have any tdi specific tips? Just a recap, FE shift points, Any issues FASing with the turbo, any other tdi tips? Thanks, Matt
Hi Matt and well done on your *new* TDI. I love my i-CTDi I have the European 2.2 Honda diesel which I've had from new in '06 and have been hypermiling since '08. I probably shift at about 2000 revs, I can't be precise as I'm usually concentrating on engine load on my UG. I get peak torque at 2000 revs so this tend to be my max. revs if not accelerating but I'm usually way below 1500! I turn the engine off all the time and apart from waiting for the revs to drop to 1000 or below (my tickover is 850) I haven't had any issues. Bump starting isn't a problem either although it needs higher speed than my wife's Honda Fit (Jazz in the UK) - probably the due to difference between gas and diesel. If I get stopped by traffic lights (which is quite often unfortunately on my commute) it's engine off and then key start, again no issues. I car pool so I tend to do more ICE on Neutral coasting as opposed to ICE off. My diesel responds really well to P&G. I hardly ever let the car idle when stationary. Over .3 g/h when it's warm at idle seems high - mine is in the low 0.2's Hope that's of some help Enjoy!
Not directly hypermiling, but TCO related, Mike Sefton, CleanMPG's resident Canadian diesel guru suggests adding some lubricant to newer diesels so the European diesel pump gets the kind of lubricity for which it was designed. Might not be such a big deal for older diesels though.
I think 0.2 or 0.3 gph is too much for modern diesels. I was thinking 0.3 LITRES per hour. Any TDI owners care to educate me ?
It is a lot for a modern diesel. At first I thought my gauge was off, but it is pretty accurate compared to math done at fuel fill ups so I don't think so. I read somewhere that someone else was getting similar idle numbers with the Pump-Duese engine ('04-'06 or '07 I think). It uses a different type of injection and apparently uses more fuel at idle, but if it just my car let me know how to fix that. I tried FASing today (hopefully didn't cause any problems) and after a few short trips around town (2-3 miles at a time, with plenty of cool down time between) and got 54mpg. Matt
That does sound like a lot, for comparison my distributor pump 2001 TDI was around 0.1 gph at idle. Perhaps there was some emissions reason for doing that at the same time as introducing the PD engine. Common rail engines are more sensitive to bad lubricity than other ones, but it still can't hurt to put in an ounce or two of additive when you fill. Or if your state mandates biodiesel blends then that already has you covered. If you aren't comfortable with a FAS then NICE-ON will still give pretty good results. In my 2001, I did a lot of NICE-ON. And if you do run into a time where you need to accelerate quickly to merge or whatever, don't be afraid to run the rpms up. A dose of brisk acceleration once in a while helps keep things running smoothly on those engines.
Yea, I was thinking that I wouldn't worry about FAS with the good idle sipping, but with my .3 to .4 at idle it really makes a huge difference to turn the engine off. I haven't filled up with biodiesel yet since there aren't any stations real close to my house with it. Next time on the other side of town I'll try B20 which is the highest I can get here. What additive do you suggest? Matt
OK, so I think I have figured out the issue. I have the Ultra Gauge, which uses the MAF to determine fuel usage. I think it assumes about a 14:1 air:fuel mixture which is common in gas engines since they add gas based on the air measurements. Unfortunately for the UG, diesels have a variable air:fuel mixture from about 15:1 to 50:1. So, when my car goes down to idle, it runs really lean, but it's pulling so much air in that the UG thinks I'm using .3 - .5 g/h. There doesn't seem to be any work around to this. Now, I could just ignore what it says I'm getting at idle, but it kills my overall mpg numbers for the trip (I reset my trip in the UG about every 100 miles). It also makes me wonder if the rest of the numbers are at all accurate. When my turbo spools, I'm obviously drawing more air in, so the UG reports my gas mileage taking a huge hit, but is it really using all the fuel the UG thinks? I've calibrated it, so at least the overall mpg it reads is pretty close to actual mpg, but I'm wondering how I can effectively use my gauge to help me. The engine load gauge also seems to be off since it goes straight to 100% if I'm accelerating at even a slow rate. Any thoughts or am I just SOL? Thanks, Matt
I thought I'd update you guys on my numbers after putting some more miles on. In the city I am generally between 50 and 60mpg. My best round trip (the only way I can honestly post becuase all of the hills here) was about 26 miles in the city and averaged 66mpg. I was a little disappointed however when I did a hwy trip and kept my speeds down (mostly around 60 and never above 70) and only got 60mpg. All these numbers are according to my calibrated UG, but as shown above, it doesn't always show accurate figures, so I'm not sure if these numbers are correct. Matt
Keep in mind if you slow down using engine braking, the car cuts off fuel entirely-watch your MFD and you'll see. Increase tire pressure, try to do long coasts in neutral when you can. Spirited driving in moderation does not hurt FE that badly in VW diesels. I've gotten my Passat up over 60 MPG several times running to the burbs with some careful driving.
