Hello, I'm a USA Diesel Owner
 

Finally got the Jetta to something postworthy: Main problems were stuck open thermostat and missing factory bellypan. Also, lots of bad rubber, a few electrical things. It had been used and then sat for a while. Has a Malone Stage 1.5 tune.

The open thermostat was hurting me by 4-5mpg. I finally cobbled enough parts to get the factory bellypan back together. Also removed mudflaps. This gave me inspiration to do a significant grill block. Still testing to see if it is adequate in the hot weather. The cooling happens through the emblem and the ~ 1.5" x 2' opening on the lower bumper (not visible in pics). I believe it will be adequate driving like I stole it in 95F weather. For higher temps I will remove the emblem.

Working hard on the driver mod and looking for some 50+mpg numbers. I broke 55 in a stock (small grill block) Beatle TDI which I am in the process of selling. it is in much better shape than the Jetta haha. These are tank-to-tank numbers.

Looks good. And with a TDI you will have a high upper maximum MPG as you work on the "driver mod," or the "nut behind the wheel." Is this a manual transmission?

https://ecomodder.com/forum/attachme...p;d=1590876879

Yep. Auto trans is to be avoided in these years. I understand it injects zero fuel when coasting in gear. I got behind a Model S who was hypermiling on I-80W near Auburn and the engine/regenerative braking were pretty comparable on each short little downhill.

Even though a grille block may eventually fool you into believing the thermostat could become somewhat redundant, it's still preferable to have it operating properly.

Oops I did it again
 

Haha, love diesel's low heat rejection efficiency. Looking forward to ABA testing with the intercooler and other lower grille blocks. Upper is "temporary." Also have a gap to fill on the driver side one.

Update: I went to measure for a muffler and before I knew it the sawzall was out and the 19lb behemoth was on the ground :confused: My hypothesis was: based on its excessive size, it was designed to cancel out low frequency more than make it quieter. It now spools even quicker and has the exact sound I was going for. Total volume still about the same inside so I guess I'm done for now! :D Planning to make a high velocity tip to get the vapors out safely since they are dumping around the rear axle.

This was inspired by some work where the author measured pressure drop across the MK4 TDI flow path on the air and exhaust sides. The muffler had the most restriction, and it appears the most weight. I'm really stoked about how this car is coming along. Next step I want to pay Malone to work on the low/mid maps to wring as much mpg as possible. It currently has injectors, injection pump, and the stage 1,5 tune. Because of all the fueling mods I believe there is room to improve.

Oh, yeah! Weight reduction, baby!

It's usually pointed out that turbocharged engines don't really require further restrictions after the turbine outlet, so a shorter path for the exhaust might be quite desirable. Plus the turbocharger already provides some reasonable levels of noise suppression too.

Totally! Glad I didn't buy something before I started cutting. It would have been dead weight.

Another update: The grill block seemed ok testing at 92F. Couldn't get the coolant temp to move. Waiting for the first 100 degree day.

Nice to welcome another TDI owner on this website! TDI's have enormous potential in terms of consumption figures. With cheap adjustments like grille blocking, weight reduction, overinflating tires and a different driving style, you could easily gain 20%. I recently did a 78 MPG trip where I previously got around 60 MPG … And meanwhile I know there is even more to it.
Good luck!

Welcome from a fellow TDI enthusiast and all diesel family.