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That's a lot of miles on a vw bug. Pretty interesting it lost power so fast, even 30k miles. 11 engines would average out to be 68.2k miles per engine. I assume you bought all the engines from the same source? Maybe they weren't rebuilding the engine for longevity or something. Maybe that engine just isn't the great, but a ton of people use them in dune buggies, I figured that people would choose an engine because of ease of modding and longevity.
I've put 80k miles on my corolla and did feel a bit of a power decrease, but is was probably 5-10% and the engine was at 300k miles, 1.8L. I did almost nothing to the car maintenance wise besides oil. It was a beat up trashed car to start with, and I fixed the major stuff and just drove it. I took it off road a little and used it like a mini truck, I hauled scrap in it and such. Probably 2000lbs of junk stacked in the car, trunk etc and the suspension was just about maxed out. Stock it has maybe 4in of ground clearance, and with the load in it, it was more like 1-2in lol.
I've read a little more about the propane injection and every time someone mentions mpg, their claims seem very high. Basically every claim works out to around 30% gain except one that claimed a 60% gain in a VW TDI car. One guy explained how he did a DIY style install that didn't really meter the propane or anything, just based it off of pressures and the logic more psi is more flow/gas. It was an gas propane setup, not liquid, he had the first regulator right at the tank set to 10psi, and the second regulator right before the injection point set to around 1psi. He stated how long his propane lasted, and his mpg, so I reversed the logic and he's using about 20% propane vs 80% diesel by volume which is right spot on with what other people say the mix is safe at. He set it up so the propane only injected when the throttle was pressed far enough to make a little boost using a micro switch. The VW guy used a pressure switch on the boost side of the turbo to activate his propane. Seems like a combo of both would be needed and have to monitor EGT's. The VW guy used a fork truck vaporizer and used liquid propane and used a solenoid to turn the propane on/off and the injection point was before the turbo. He didn't speak english super great, and I don't think he knew how the system worked too well, seemed like he bought it as a kit from somewhere or something.
Anyway, at the 20% level, I think that's pushing the limits a little for how much propane is added, I was thinking starting off around the 10% mark. Of course I'd need to buy the propane solenoids and such to try this.
The guy doing the double regulator setup claimed 29mpg out of his truck, but he didn't give much info like auto/stick, gear ratio etc. He said his normal mpg was around 21-22mpg which is just over 30% gains.
If this propane setup is truly good for 20%+ gains, I don't understand why every diesel doesn't run propane with it. The fuel savings alone would easily pay for a proper system within 50k miles. Of course I'm assuming bulk propane prices, not the $20 for a 20lber refill which is over $4/gal.
It would be interesting to put this idea to the test and figure a way to meter mpg fairly accurately for quick aba style tests at different amounts of propane, say 0%, 1%, 5% 10% 20% for starts. It would be interesting if it only took a tiny amount of propane to get the mpg benefits.
I do need to get a gauge for EGT and get some base line numbers. From what I read, EGT at low load with diesel + propane is less than normal diesel, but at higher loads (and more propane in a digital system) the EGT can get too hot so either needs to be turned off or keep out of the throttle. People online said the extra power comes in low to mid rpm which sounds perfect for mpg and daily driving.
Assuming the 26.6mpg is accurate for the expressway trip at 60mph, a 30% gain would be 34.6mpg, add some areo mods and in ideal situations the truck could pull some impressive numbers, but that's a lot of assuming and theory talk. Hitting a typical driving average of 25mpg I think would be a pretty solid goal to start with, and more or less confirm the more ideal mileage when I take a long trip again.
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