Previously tuned up 250?

hethead

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I have an M820 I plan to modify extensively into an "expedition rig" over the next 12 years when I hope to retire. I'm just tinkering and playing with it now, slowly adding things that will eventually come together. The end goal for the engine is turbo, piston coolers (I have a machining and fabrication background), intercooler, a 3rd gearbox, etc. But for now I'm just doing the easy stuff. So I installed a #15 button and rail pressure gauge. EGT gauge goes in tomorrow before I drive it more than a few blocks.

I haven't touched the throttle shaft or governor springs yet, just the fuel button, and under load, it pegs the 220 lb gauge real quick. I back off of it, of course, but it wants to spin up past 2100 pretty quick too.

I wasn't expecting that much of a difference to governed redline and that much of a rail pressure change by just changing the button and nothing else.

I'm wondering if wasn't turned up while it was still in service. It ran alright from Philly to Florida to Seattle but I assumed it was still at stock pump settings.

Anybody else buy a surplus truck that was turned up already? Or anybody else just swap buttons and get these numbers froma stock motor?

I'm keeping a close eye on rail pressure and EGT's for now (and only drive it a couple times a year, locally) but I may need to go to a lower pressure button. I'd like it to be a 200-300,000 mile engine at least.
 

US6x4

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Fire departments are known for turning up their engines as performance is more important than longevity for them. Do you know if it ever belonged to a fire department?
 

hethead

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Fire departments are known for turning up their engines as performance is more important than longevity for them. Do you know if it ever belonged to a fire department?
I don't. It still had the expansible van body on the rear when I bought it and just looked... ex military. I figure either somebody was into the pump before me to ring it's neck, or just changing the button affected the governed speed and had a huge affect on rail pressure. I'm hoping it's the latter.
 

Crf450x

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The fuel button is what controls rail pressure. Pressure is the only way a pt pump meters fuel. 220 sounds right for a 15. What was the number on the one that came out of it? You should definitely get that egt gauge in now because without a turbo, it's gonna be running pretty hot.

Your max rpm is gonna be determined by the spring and shims. Warm the engine up then see what the rpms go to at wot in neutral. I would expect anywhere from 21-2400, which is fine. If you want to lower it you can remove shims.
 

hethead

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Seattle, WA.
The fuel button is what controls rail pressure. Pressure is the only way a pt pump meters fuel. 220 sounds right for a 15. What was the number on the one that came out of it? You should definitely get that egt gauge in now because without a turbo, it's gonna be running pretty hot.

Your max rpm is gonna be determined by the spring and shims. Warm the engine up then see what the rpms go to at wot in neutral. I would expect anywhere from 21-2400, which is fine. If you want to lower it you can remove shims.
The one that came out was a 45, which had the rail pressure at about 160-170 ("snap test"). It would go to 2200 and I would be careful to not spend much time there. With this higher rail pressure, I let off at 2400 before it could go any higher. The EGT gauge is going in today for it's 25 mile trip back to it's storage. I'll have to keep on eye on EGT on the highway. And rpms. And rail pressure (which is ok in the short term). Long term I don't want to have to be monitoring quite as many gauges so urgently, so I guess I might end up removing some shims to bring the revs down. I don't want to run over 2200. And I'll bring fuel pressure down to around 200 with a different button I suppose. Looks like I won't have to touch the fuel screw in the throttle shaft if the rail pressure's already over 220 psi with this one. Thanks.
 

Crf450x

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The one that came out was a 45, which had the rail pressure at about 160-170 ("snap test"). It would go to 2200 and I would be careful to not spend much time there. With this higher rail pressure, I let off at 2400 before it could go any higher. The EGT gauge is going in today for it's 25 mile trip back to it's storage. I'll have to keep on eye on EGT on the highway. And rpms. And rail pressure (which is ok in the short term). Long term I don't want to have to be monitoring quite as many gauges so urgently, so I guess I might end up removing some shims to bring the revs down. I don't want to run over 2200. And I'll bring fuel pressure down to around 200 with a different button I suppose. Looks like I won't have to touch the fuel screw in the throttle shaft if the rail pressure's already over 220 psi with this one. Thanks.
Yeah I wouldn’t feel comfortable going past 2400. Anything under that will be fine. Sounds like you pretty much know what you’re doing though. I look forward to hearing about the egt. I never checked mine with no turbo and I wish I would have.
 

simp5782

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Valve springs are good to 2700 after that they let go.

More load on motor more rail pressure accuracy not just a snap test. I have 250psi at 1900rpms with a loaded trailer.

Small cam can run 215psi on the rail and a #14 button before you have temp issues with no turbo I ran one for years with this setup with no turbo and no Pyro. The different air filter system I had helped the longevity when the liner had issues at 225k miles
 

hethead

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Just drove it around town to check things before the trip tomorrow (which will be a 2 hour drive on the Interstate) and I kept the rail pressure down below 200 psi and the egt's hit about 700-800 F. I was only as high as low range 5th, though, so hardly a real test. I'll be keeping a close eye on things and post back here what numbers I see on the road in top gear with the #15 button and a straight pipe (muffler was rusted out falling apart). Thanks for your advice guys. I'm new to big diesels.
 

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hethead

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Seattle, WA.
Ok. Trip went great. The engine feels significantly stronger and it maintains 60 mph (gps) with a light throttle now. It feels like a 14 liter engine.

I ran it at 2200 rpm, at between 200-210 psi pump pressure and the EGT's stayed at 900 F or lower. I leaned on it kinda hard on purpose on a grade once and it hit 950 F but I couldn't get it any hotter.

I was wrong about the governor. It defuels at 2200 under load and maintains that rpm (which is 60 mph on my Goodyears).

I'm going to change to maybe a 20 button. If I throttle up, it'll climb to 260-270 psi and I don't want that high. Maybe 220 tops.

It sounded pretty good. Very light smoke under heavy throttle.

Changed the oil and filter too while it was hot.. It took 28 quarts.
 

hethead

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Location
Seattle, WA.
Ok. Trip went great. The engine feels significantly stronger and it maintains 60 mph (gps) with a light throttle now. It feels like a 14 liter engine.

I ran it at 2200 rpm, at between 200-210 psi pump pressure and the EGT's stayed at 900 F or lower. I leaned on it kinda hard on purpose on a grade once and it hit 950 F but I couldn't get it any hotter.

I was wrong about the governor. It defuels at 2200 under load and maintains that rpm (which is 60 mph on my Goodyears).

I'm going to change to maybe a 20 button. If I throttle up, it'll climb to 260-270 psi and I don't want that high. Maybe 220 tops.

It sounded pretty good. Very light smoke under heavy throttle.

Changed the oil and filter too while it was hot.. It took 28 quarts.
Also, after I changed the oil, there are some fairly big trees that my friend cut down to 4 ft. high stumps that his tractor can't seem to budge. I was gonna rock them with the truck but when I lined it up with the frame rail and pushed, the back wheels spun, the front axle engaged and it just snapped roots as big around as your arm, ripped it out of the ground and drove over it. I was impressed. These things are quite the bulldozers.
 
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