1986 FJ73 Converted to HZJ73 Fuel Mileage

[svsisu]

I also would expect driving 55-60 to yield best results. I CAN drive 75 in mine but I feel like it’s just working it harder and I don’t.

It’s seems pretty happy at 62/64 with my 34” tires, but under 60 feels like it’s just easily plodding along without much effort.

It seems like driving 55 everywhere just p1sses people off. So you can always put your turn signal on and never turn it off and they will think you are a confused old man

I average about 19 in a turbo 1Hz, unbuilt troopy on 35s, and 4:1 tcase gears. It seems happiest 60-65, over 65 and that average starts to go down quickly. What I really like is that average doesn’t change much in 4wd soft sand, beach driving.

I love driving slowly and pissing people off, especially during tourist season

 

[davegonz]

I average about 19 in a turbo 1Hz, unbuilt troopy on 35s, and 4:1 tcase gears. It seems happiest 60-65, over 65 and that average starts to go down quickly. What I really like is that average doesn’t change much in 4wd soft sand, beach driving.

I love driving slowly and pissing people off, especially during tourist season

What gears are you running?

The last two 1HZ that I turbo'd (60 series and an 80) had lower mileage after the turbo. You're getting great mileage.

 

[svsisu]

3rds are 4.11, and the 4:1 tcase gears lower the high range about 10%. The 35s help with that, and staying around 65 mph makes a big difference.

 

[davegonz]

3rds are 4.11, and the 4:1 tcase gears lower the high range about 10%. The 35s help with that, and staying around 65 mph makes a big difference.

So your gearing is effectively 3.70. Hmm. I'm running 33's with my 4.11 gears. But you're turbo'd!

 

[svsisu]

I think my gearing may be closer 4.56 (that’s lower, right?) with the reduction gears, but don’t know what it is effectively with the 35s. I’ve been toying with putting 3rds (3.70?) from a 60 series in, but the truck drives really well and feels like it has the right gearing in the mountains.

I think my RPMs are about 2400-2500 at 65mph, relatively flat interstate driving. I’m getting ready to do a pretty long road trip and will try to get some more data, and fact check my numbers. It has taken a bit of a hit since I added the pop top.

There is a guy (@The Machinist) on here that has a turbo’d 1Hz 60 series, with standard 3rds, 4:1 tcase gears and I think 35s. He reported 17-23 mpg while NA and slightly less since the turbo. His thread is a “fresh start for a tired 60-1Hz conversion. Good info, and what I think are realistic, accurate data points.

I know you have a good bit of experience with these engines and putting turbos on them, so it’s interesting to see the variance across peoples experiences.

 

[The Machinist]

I think my gearing may be closer 4.56 (that’s lower, right?) with the reduction gears, but don’t know what it is effectively with the 35s. I’ve been toying with putting 3rds (3.70?) from a 60 series in, but the truck drives really well and feels like it has the right gearing in the mountains.

I think my RPMs are about 2400-2500 at 65mph, relatively flat interstate driving. I’m getting ready to do a pretty long road trip and will try to get some more data, and fact check my numbers. It has taken a bit of a hit since I added the pop top.

There is a guy (@The Machinist) on here that has a turbo’d 1Hz 60 series, with standard 3rds, 4:1 tcase gears and I think 35s. He reported 17-23 mpg while NA and slightly less since the turbo. His thread is a “fresh start for a tired 60-1Hz conversion. Good info, and what I think are realistic, accurate data points.

I know you have a good bit of experience with these engines and putting turbos on them, so it’s interesting to see the variance across peoples experiences.

My truck currently has 33s and stock 3.70s, but I'm planning to put 35s to help lower rpms on the highway. My 17-23mpg numbers from before the turbo were with a fully loaded truck going 70-80mph on the interstate on a trip from California to Colorado. New injectors, rebuilt injection pump, new filters, etc. Best guesses on the engine based on the last timing belt sticker was that it had in the ballpark of 300,000 miles on it when I got it.

Since this is a converted diesel, any chance a clogged in tank sock filter affecting fuel mileage? Hell, do these 70 series even have them?

Have you noticed any odd stumbling or breaking up at part throttle or under sustained high rpm that might indicate a fuel delivery issue? Maybe swap out fuel filters or add a cheap parts store lift pump to test if that helps anything. Although I'm not sure that this would make your mileage all that much worse.

Does it smoke or soot excessively? Any symptoms of clogged or dirty injectors or improper injection timing?

 

[davegonz]

No soot or weird throttle response under load or idle.

Yeah, my next step was going to replace the fuel filters. I don't see why that would impact things, but it's cheap to try.

 

[Dougal]

Everyone is talking axle ratios. But what is the rpm?

Also. We've got Americans and Aussies in here talking MPG. Are they aware US gallons are smaller than the rest of the world?

 

[davegonz]

I'm in the process of installing a tiny tach to get rpm numbers. Unfortunately, I ordered the wrong-sized transducer.

 

[FJBen]

I think my gearing may be closer 4.56 (that’s lower, right?) with the reduction gears, but don’t know what it is effectively with the 35s. I’ve been toying with putting 3rds (3.70?) from a 60 series in, but the truck drives really well and feels like it has the right gearing in the mountains.

I think my RPMs are about 2400-2500 at 65mph, relatively flat interstate driving. I’m getting ready to do a pretty long road trip and will try to get some more data, and fact check my numbers. It has taken a bit of a hit since I added the pop top.

There is a guy (@The Machinist) on here that has a turbo’d 1Hz 60 series, with standard 3rds, 4:1 tcase gears and I think 35s. He reported 17-23 mpg while NA and slightly less since the turbo. His thread is a “fresh start for a tired 60-1Hz conversion. Good info, and what I think are realistic, accurate data points.

I know you have a good bit of experience with these engines and putting turbos on them, so it’s interesting to see the variance across peoples experiences.

Again, why am I talking…13bt…


That said I’m running 34” yokohama muds, I run around 2300 rpm at 65mph. I have stock 4.10s.

The rpm’s are a great point, but I agree above 65 it’s starts dropping quick.



And still i average 20mpg in American flag waving, PBR can shooting, bald eagle screeching Freedom units.

 

[sodafeld1]

Just to add, met a fella who reckons he gets 7.8l/100km or around 30mpg in his hilux with a 1kd engine, which was designed to be 11% more efficient apparently.

Also had a look at the hdfte in a cruiser hdj79 ute, don't know it's economy probably more fuel, but sounds sweet for sure, would be a good work horse.

 

[nuclearbeef]

Another data point:
1985 BJ75 Troopy with the stock, non-turbo'd,

3b.
Around town I get approximately 20 US MPG.
Going to and from Windrock last year on the interstate at 75 MPH, I got only 13 US MPG!
(edit) A/C on full blast.

 

[AirheadNut]

Another data point:
1985 BJ75 Troopy with the stock, non-turbo'd,View attachment 3691442 3b.
Around town I get approximately 20 US MPG.
Going to and from Windrock last year on the interstate at 75 MPH, I got only 13 US MPG!
(edit) A/C on full blast.

The fact that you could even go 75mph in a 3B troopy with AC is a miracle!

 

[Omrib]

4.11:1
32's
1hz with 520kkm
Getting around 16.7 Mpg optimistically
Going around 55

Offroad is between 800 and 1500 rpm and never had any problems going through 3 days offroad with the 90 liter tank
And getting half way home

 

[svsisu]

Follow up report. I've recently done two trips from the coast of NC to the mountains of WV and back, roughly 950 miles per trip. Elevation ranged from 3' to over 4000', no AC and windows down, mostly driving at 65-68 mph with RPMs in the 2450-2600 range. Using milage calculated by gps and google maps between various fuel stops, and the amount of fuel added at each stop I averaged 18.45 US gallons/Statute mile. This jives with most other road trip calculations I've done. Again, this is in a 5500 pound troopy, with an even less aerodynamic pop top installed. Slightly better than other numbers posted, but not as good as some.

 

[davegonz]

Thanks for the extra data point!

I would sell my 73 in a heartbeat for a Troopy to haul my bikes in!