12HT drivers, heres some questions for you

[cruiserpilot]

I don't have a functioning tach. I run 3.73 gears and 34" tires. Mostly I run at 90 kph in 5th and 4th.
I spooled it up to 120 a few times just for fun, but fuel economy becomes non existent even for short periods
that have a serious effect. Drive it like a diesel, not a gasser. No benefit driving higher revs above the
power curve, my .02

 

[Silveredition]

I only rev mine to 2500 when in a hurry to get up to highway speed. Usually try to keep it below 2000. At 110km/hr it sits on about 2500 with 31x 10.5 15's... 3 inch straight through exhaust with no muffler, and it sounds great!!

 

[AussieHJCruza]

I don't routinely rev mine above 3k, but IMHO, if Mr T specs the max rpm be set to 4100 or 4150, I would be confident that it could do it without difficulty
From having a 1HD-T with go fast mods and a whole host of gauges to match, and experimenting in various situations, you're putting a lot more load on everything and EGTs and water temps will be a lot higher lugging up a hill at 2 grand as opposed to revving it at say 3k where the fan is moving a lot more air, water pump turning faster, most likely making more boost, EGTs lower and so forth.
That's my experience

 

[Vossie]

1987 HJ61 tach:
View attachment 1505003

thanks, this helps quite a bit as it gives Toyota's own view on where red line is

Why would I want to routinely do it? Its something you do as a test when there is a problem.

sorry, bit of a misunderstanding here, my bad. reason im asking is due to wanting to cruise at speed where my rpm would be in the 3,5k rpm range and maintain it for a long period of time, say 6 to 7 hours.

 

[Vossie]

I only rev mine to 2500 when in a hurry to get up to highway speed. Usually try to keep it below 2000. At 110km/hr it sits on about 2500 with 31x 10.5 15's... 3 inch straight through exhaust with no muffler, and it sounds great!!

i find i drive like this usually, keeping revs to around 2k unless needing to move quickly. getting 31's pretty soon. are you running a 5 speed box?

I don't routinely rev mine above 3k, but IMHO, if Mr T specs the max rpm be set to 4100 or 4150, I would be confident that it could do it without difficulty
From having a 1HD-T with go fast mods and a whole host of gauges to match, and experementing in various situations, you're putting a lot more load on everything and EGTs and water temps will be a lot higher lugging up a hill at 2 grand as opposed to revving it at say 3k where the fan is moving a lot more air, water pump turning faster, most likely making more boost, EGTs lower and so forth.
That's my experience

ja, i can understand that. work a diesel rather than lug it.

 

[AussieHJCruza]

Re the longer periods of time, haven't done it in the 12HT but had the 1HDT revving at 3k to 3300 for 1800 km (was towing a reasonable weight so wanted to stay out of 5th except on downhill sections) with no problems.

 

[Silveredition]

i find i drive like this usually, keeping revs to around 2k unless needing to move quickly. getting 31's pretty soon. are you running a 5 speed box?

Yep - 5 speed box

 

[Dieseler]

12ht likes the 2000-2500 rpm range on the highway for best mileage I often like to run it past that point getting up to speed I love the acceleration and the sound of the growl of the 12ht.
When I push mine up to the 120kph I am in the 2800rpm range but the 3000 range to me is a little high for a long duration a lot of heat in the engine and turbo running at 3k+.
What is your back end gearing.
I would look for a 5spd trans but the rpms you are pulling with the 4 box I don't think you will drop down that much in the rpm range.
At highway speeds 100kph-110kph I only get a drop of 500rpm from 4th to 5th or 2500 down to 2000rpm I have 35s which helps keep the rpms down as compared to running a stock tire and IIR my HJ61 has 4:10 stock gearing but I could be wrong on that ....I have too many cruisers to remember everything about them.

 

[HoJo 61]

I might add my 2 cents also.

3.7 gears, H55F, 33" tires, 3" exhaust and Supra turbo.
2K rpm @100km/h and 0.5bar of boost.
I don't usually rev it past 2500rpm, as i don't really have to. Hauls ass pretty nicely from 1500rpm.