Long trip ahead; 70mpg tank goal with Helga (Jetta TDI)

[NachtRitter]

Yep, it is true... always trying to do better. Sadly, it wasn't to be on this trip. My last fillup was a disappointing ~56mpg. It was windy again, with "gusts up to 55+ mph" according to a big freeway "variable message sign"... all the wind seemed to be directly across the road, so no help but likely a hindrance. Hanging out behind larger vehicles didn't help either.

Back home now, so no more opportunity to rack up the high FE numbers until my next long trip toward the middle of May.

Thank you for the encouragement... everything held together well, and maybe I can get some things done for the next trip that I didn't have time to do for this trip...

[Frank Lee]

So if you didn't expect an fe increase, what's up with the muffler delete?

[Phantom]

It sounds better and less weight.

[NachtRitter]

Yup, exactly. I'd heard somebody else's muffler-less VW TDI and loved the sound. A side benefit (related to FE) is that I could fit the axle-back undertray much more easily without the muffler in place (the body of the muffler hung down quite a bit).

[AndrzejM]

Pity you didn't succeeded to go above 70 mpg but I'm sure that you will do it finally.
What other mods are you planning to do before next trip?

[NachtRitter]

OK, maybe I can claim a partial success... On the last leg of the return trip, I filled at Carlin, NV which is roughly 400 miles from home. It is at about 5,090ft and from there I had to climb up another 2,000ft before dropping down to 1,280ft where I live. I decided to fill up today (just so I could get an FE number that is nearly all related to the trip and doesn't have a bunch of errand-running mixed in) and the FE for the (less than) half tank is ... over 72mpg! Woohoo!

I only claim partial success because 1) it is only a half tank, and 2) since I filled at different stations than normal, the previous low and current high FE values could likely be a result of the filling process.

I will say that driving normal routes around home, the FE does seem noticeably higher. However, that could be in part because switching between pure dino-diesel and a biodiesel blend seems to confuse the Scangauge (the amount of fuel it thinks I used is noticeably different). So we'll have to wait 'til the next fill to see if there really is an improvement.

For my next trip in May (much shorter than the last!), I would like to get the wheel covers done. I tried to make a mold for fiberglass covers based on my current hubcaps, but haven't been happy with the results so far. I may also try to get the wheel spats done; didn't have time before this last trip.

[ausias]

I apologize for not responding earlier: neither direct answers neither reading new posts.
But I was busy testing and improving my Octavia TDI. that we learned is almost the same car as your Jetta TDI.


Most important thing is that I swapped my 5th gear. My 30:39 (0.769) is now a 27:41 (0.658).
So 1000 rpm meant 44.5 km/h (GPS measured) and now 1000 rpm means 52 km/h. Wow.
MY FE at 120 kph constant speed (and flat highway 50 km loop) went from standard 5.7L/100km to 4.8L/100km (measured using my callibrated onboard computer, MFA).
US: 41 MPG to 49 MPG
I'm very happy with all my mods.
I have lost some compression pressure in my engine it's about 18.5 bar on four cilynders (wear limit 19 bar) and it is supposed to be between 25 to 31 bar. Or maybe my neightbourhood workshop gauge is not working.
Assessing the numbers to theoretical fuel consumption it is suposed to be 0.5 to 0.7 L/100km less. According to the owner manual that says 5 L/100km at 120 kph as standard.

I have done several tests 50 km flat highway (but not finished yet all the before and after) between 80 to 94 kph and I'm getting fuel consumptions figures in the range from 2.8 to 3.4 L/100km
US: 69 MPG to 84 MPG

I have not planned any long trip and we'll need to wait before any full tanks, and more detailed pictures on aero and 5th gear swap.

[deejaaa]

Originally Posted by NachtRitter

............The other thing I did while the car was up is put a belly pan from rear axle back to the rear bumper. Sorry, no pics at the moment. It was a late decision; not something I'd planned to do originally. I looked at the area, had a nice big sheet of coroplast, had an idea about how to secure the coroplast, and decided to give it a try. We will see if it helps...........

any way you could get some pics because i plan on making one in the next couple of weeks. need some ideas.