Limiting RPM...

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I'm luving it
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Limiting RPM...

Postby I'm luving it » Mon Feb 10, 2020 8:55 pm

Anyone (Paul) know of a way to limit the injection pump to a max RPM? Or any other way? My motor revs up quick when off roading. I would like to limit it to 3500 to be on the safe side. I know there is a governor set at 4000-4200 but that’s way to high for me.

Thanks!
HAD***1981 Turbo Diesel, long bed, 4x4, 5 speed, 5.29 locked Toyota axles, 33/10.50/15 tires, 2.5” exhaust, GT1548 turbo, 12 pounds of boost, intercooler, 30 mpg.

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Paul
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Re: Limiting RPM...

Postby Paul » Mon Feb 10, 2020 9:16 pm

I'm luving it wrote:Anyone (Paul) know of a way to limit the injection pump to a max RPM? Or any other way? My motor revs up quick when off roading. I would like to limit it to 3500 to be on the safe side. I know there is a governor set at 4000-4200 but that’s way to high for me.

Thanks!


Well, yes. There is a full throttle stop screw on the passenger side of the pump. You can screw this in to stop the throttle travel sooner. This will reduce the governor spring tension at full throttle and the engine will not rev so high. Trouble is, I cannot tell you just how much to screw it in as this question has not come up before. Most folks want more revs, right?

However, I think one or two full turns will do what you want. Also, note that doing this will not reduce the full load fuel at lower speeds due to the nature of the governor, so should be an OK thing to do.

Hope this helps - -

Paul
'84 P'UP 2 wd diesel, 5 spd with 0.78 fifth gear and differential back to 3.73.

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Re: Limiting RPM...

Postby I'm luving it » Wed Feb 12, 2020 12:36 am

Thanks Paul I will try that. You by chance have a picture of the correct one to turn?
HAD***1981 Turbo Diesel, long bed, 4x4, 5 speed, 5.29 locked Toyota axles, 33/10.50/15 tires, 2.5” exhaust, GT1548 turbo, 12 pounds of boost, intercooler, 30 mpg.

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Re: Limiting RPM...

Postby Paul » Wed Feb 12, 2020 12:54 am

Yes, here is a photo.

Paul

Max Engine Speed Screw.jpg
'84 P'UP 2 wd diesel, 5 spd with 0.78 fifth gear and differential back to 3.73.

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Re: Limiting RPM...

Postby puttputtinpup » Wed Feb 12, 2020 8:41 am

The 1st time I met Jerry in Atlanta for dinner, we talked about the over revving of off-road turbo diesel troopers and Pups. He and the Isuzu engineers were trying to come up with a rev limiter for those engines for the1988 diesels. I suggested a switch of some kind incorporated into the tach that would kill the fuel solenoid voltage at the specified rpm...redline. in order to save the engine.

1987 was the last yr for the turbo diesel. It wasn't offered after that, so they never developed a rev limiter.

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Re: Limiting RPM...

Postby I'm luving it » Wed Feb 12, 2020 9:27 am

Thanks Paul! I am drooling over the fancy pump
I like the tach idea! Just have to wire I relay so it would work off the shift light of the tach. Set your shift light at 3500 and when light comes on it would power the relay and disconnect the fuel cut solenoid. Alas I am currently running a tiny tach with no shift light.... I will add that to the ever growing list.
HAD***1981 Turbo Diesel, long bed, 4x4, 5 speed, 5.29 locked Toyota axles, 33/10.50/15 tires, 2.5” exhaust, GT1548 turbo, 12 pounds of boost, intercooler, 30 mpg.

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Re: Limiting RPM...

Postby Halden » Wed Feb 12, 2020 9:38 am

My solution would be to just have the radio on full blast. Outta sight, outta mind... (Kidding!)
It's not pronounced "Ih-soo-zoo", it's pronounced "It-screws-you"
83 LS Long Box Dsl 4x4
82 Short Box Dsl 5 spd
64 Chevy C20 w/ 283 & 4 speed.
05 Sonata with a standard

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Re: Limiting RPM...

Postby I'm luving it » Wed Feb 12, 2020 5:51 pm

Sounds about right for the way you drive! :D
I never thought I babied my truck until I saw your 3000+ RPM shift points :shock:
HAD***1981 Turbo Diesel, long bed, 4x4, 5 speed, 5.29 locked Toyota axles, 33/10.50/15 tires, 2.5” exhaust, GT1548 turbo, 12 pounds of boost, intercooler, 30 mpg.

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Re: Limiting RPM...

Postby Halden » Wed Feb 12, 2020 7:06 pm

I'm luving it wrote:Sounds about right for the way you drive! :D
I never thought I babied my truck until I saw your 3000+ RPM shift points :shock:


Typically I am pretty conservative, but from time to time I get on it. A NA engine will never outpace the governor. Even my gas vehicles I'm not afraid to hit the danger zone... It's set by the engineers as a safe max operating speed.
It's not pronounced "Ih-soo-zoo", it's pronounced "It-screws-you"
83 LS Long Box Dsl 4x4
82 Short Box Dsl 5 spd
64 Chevy C20 w/ 283 & 4 speed.
05 Sonata with a standard

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Paul
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Re: Limiting RPM...

Postby Paul » Wed Feb 12, 2020 11:05 pm

Notes - -

If one shifts down a gear at too high a speed, there is no governor that will prevent engine over reving.

Using the fuel cut solenoid to control over reving will likely cause a rather vicious on/off cycling of the engine.

Best rev limiter is the right foot.

Paul
'84 P'UP 2 wd diesel, 5 spd with 0.78 fifth gear and differential back to 3.73.

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Re: Limiting RPM...

Postby I'm luving it » Thu Feb 13, 2020 1:07 am

True.....the fuel cut solenoid for me would be used as a final kill for the engine to avoid damage. The hard part about the right foot is when you are in 4x4 Low and spinning the tires to get traction on slippery surfaces like snow and mud. The RPM quickly goes up when the turbo spools up. Before you know it you are approaching 3500+. These pictures were taken this weekend. The snow was deep.
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HAD***1981 Turbo Diesel, long bed, 4x4, 5 speed, 5.29 locked Toyota axles, 33/10.50/15 tires, 2.5” exhaust, GT1548 turbo, 12 pounds of boost, intercooler, 30 mpg.

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Re: Limiting RPM...

Postby puttputtinpup » Thu Feb 13, 2020 1:59 pm

Jerry said that was one of the major causes of rod failure in the 4x4 turbo diesel. Over revving in mud & snow

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Re: Limiting RPM...

Postby JoeIsuzu » Thu Feb 13, 2020 6:03 pm

Paul wrote:If one shifts down a gear at too high a speed, there is no governor that will prevent engine over reving.
:lol:
My younger son (15 years old at the time) demonstrated this pretty vividly when we were driving the P'up to the first meet in Concord, NC. We were accelerating up an interstate ramp, and when he hit about 65 or 70, he shifted to 5th gear. No, he shifted to 3rd gear! He didn't know what happened, and wow, it felt like an eternity getting him to push the clutch in and get it out of 3rd. I don't think I took the time to calculate the RPM. But we made it to Concord, apparently with no damage.

Jack

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Re: Limiting RPM...

Postby Paul » Thu Feb 13, 2020 11:21 pm

I'm luving it wrote:True.....the fuel cut solenoid for me would be used as a final kill for the engine to avoid damage. The hard part about the right foot is when you are in 4x4 Low and spinning the tires to get traction on slippery surfaces like snow and mud. The RPM quickly goes up when the turbo spools up. Before you know it you are approaching 3500+. These pictures were taken this weekend. The snow was deep.



OK, well, how about making an adjustable full throttle stop (say, with a pull cable) to replace the screw that is in the photo. This could give you almost any top engine speed limit you want.

Nice photos. Looks like fun off roading.

Paul
'84 P'UP 2 wd diesel, 5 spd with 0.78 fifth gear and differential back to 3.73.

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Re: Limiting RPM...

Postby I'm luving it » Fri Feb 14, 2020 12:04 am

Interesting idea. I’ll try and figure something out. Thank you for the advice.
HAD***1981 Turbo Diesel, long bed, 4x4, 5 speed, 5.29 locked Toyota axles, 33/10.50/15 tires, 2.5” exhaust, GT1548 turbo, 12 pounds of boost, intercooler, 30 mpg.