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Fri Jun 20, 2025 6:45 pm

From full to dry ... 266 miles. 7.887 gallons. 34.48 MPG?

Which I don't quite get. I ran it dry, dumped my reserve gallon in the tank and then at the pump, refilled the tank and the 1 gallon gas can. 7.778 gallons? Seems low. Unless I didn't get a full fill from the pump.

Max

Sat Jun 21, 2025 6:12 am

You did not. The tank (unless you dented it severely) is 10.6 Gal. I had that same problem with a SuperBeetle I had. I literally had to remove the nozzle, wait a second and then start again. I never had that problem with trunk filled gas tanks. If I did not pull the nozzle, it would continue to act like it was full, even when I knew it wasn't.

Sat Jun 21, 2025 7:08 am

Yeah, that's why I generally average several tanks to calculate mpg. Across the four fill-ups I have so far I have 29.12 mpg.

Max

Sat Jun 21, 2025 12:58 pm

Max Welton wrote: Yeah, that's why I generally average several tanks to calculate mpg. Across the four fill-ups I have so far I have 29.12 mpg.

Max

Sounds like you've got your MS dialed in pretty good. Especially for your altitude (I know you're changing altitudes when you go almost anywhere). You mentioned it several times when dialing your Squareback.

Sat Jun 21, 2025 7:30 pm

Bobnotch wrote: Sounds like you've got your MS dialed in pretty good. Especially for your altitude (I know you're changing altitudes when you go almost anywhere). You mentioned it several times when dialing your Squareback.
Thanks. I have the 2nd barometer option (basically a second map sensor open to the atmosphere) so it can correct for changes in ambient barometric pressure (weather and/or altitude). Also, I'm running it closed-loop which makes experimenting a lot safer.

Max

Sat Jun 21, 2025 7:47 pm

Ossipon wrote: You did not. The tank (unless you dented it severely) is 10.6 Gal. I had that same problem with a SuperBeetle I had. I literally had to remove the nozzle, wait a second and then start again. I never had that problem with trunk filled gas tanks. If I did not pull the nozzle, it would continue to act like it was full, even when I knew it wasn't. I will have to start doing that.

Max

Wed Jul 09, 2025 10:05 am

I drained my t34's tank dry to check it for debris and blow out the tunnel tube.
New sender unit from ISP West.

When refilling, I check the ohms vs gauge reading for every 5 liters added (standard gas can here in CZ).
Results:
Dry- halfway on the teardrop shape to the left of R, 85 ohms
5L- Just below the R level mark (reserve, should be 5L), 80 ohms
7.5L- Top of the R level mark, 71.5 ohms
13 L- at 1/4 level mark, 54 ohms
20L- at the "1" in 1/2, 40 ohms
30 L- just below 3/4 mark (or just below "1" in 1/1), 30 ohms
40 L- slowly crept up to the FULL mark, right on the nose, 10.5 ohms.

So, after making sure my gauges were grounded well, and adding a ground wire to the tank sender, Im happy with it.
I made sure to wait a while for the sender to fill, especially at the top end, since the holes fill up slower, and I imagine the angle of the tank had something to do with it.
(yes Im a data nerd when it comes to electrics :lol: )
Maybe this will help someone. Ive seen a post about the ISP sender not giving a decent reading, but Im happy with mine.

Wed Jul 09, 2025 3:10 pm

I had a new sender (may have been ISP) and found the float started absorbing fuel and was sinking/ not fully floating, it’s 2 pages back on my thread but here’s what it looked like. The OG vw one is fully floating. It may be worth checking

Thu Jul 10, 2025 10:09 am

Ceckert64 wrote: I had a new sender (may have been ISP) and found the float started absorbing fuel and was sinking/ not fully floating, it’s 2 pages back on my thread but here’s what it looked like. The OG vw one is fully floating. It may be worth checking

I haven't run into a new one doing that, but I have had a sticking float before. You'd be surprised what you run into over the years of working on cars. I've had a float stick toward the bottom of the tube, and only barely allowed a gallon into the tank. That's when I started keeping track of my mileage as a back up to the gauge.