NHC250 needs more power

[jwaller]

As some of you have read my truck now desperately needs more power with the install of new 1600's.

what are all my options for the NHC-250?
how high can I run the EGT and still be totally safe.

the other weekend I ran my truck with the pedel literally to the floor for 4 hours coming home with my trailer and never got over about 60mph and never close to redline.


if I turn up the pump I dont want to have to be wary of killing it. so how high can I go and whats the limit.

I have some procedure for turning it up from other member but feel free to suggest anything.


also whats the hp and TQ limit of the trans and transfer? when do they become a problem?

 

[WillWagner]

Don't know about the HP/torque limit. The easy way to turn it up, drill the ball out of the throttle shaft and give it a 1/4 turn CCW at a time 'till you like the power. Watch the smoke, get a pyro. 1400 max.

 

[73m819]

thats odd about your low power, because the 819 with the 1200s weighs 36k, (a LOT more then your 81, has all the power it needs, it will do 60-65 easy (long hills is another story), i have to back off the rpm a bunch to keep from running over a deuce if its in front of me.

 

[WillWagner]

Maybe you have a plugged fuel filter?

 

[AMGeneral]

Is it the same procedure for turning up the pump on a 816 with an external governer?Or does that involve a more complicated process?

 

[WillWagner]

If it has a Cummins with a PT pump, yes.

 

[DaveP]

Will. 1400 degrees ? is this because there is not a turbo to cook? i did not realize that we could run them this hot. i have been keeping mine down to 1200. probably out of old habit.

 

[acetomatoco]

Everybody wants to outdrive his brakes....trucks designed for convoys at 40 mph do not like mustang speeds...oh those poor Rockwell axles...Some folks should be kept behind the wheel of a LDS427 so they can see the scenery.

 

[Recovry4x4]

It's not the power that outdrives the brakes, it's the speed.

 

[Westech]

and big ars tires!!!

 

[jwaller]

Everybody wants to outdrive his brakes....trucks designed for convoys at 40 mph do not like mustang speeds...oh those poor Rockwell axles...Some folks should be kept behind the wheel of a LDS427 so they can see the scenery.

Those poor rockwell's are turning the same exact speed they were toting around those little 1100's. I just go further every time they turn.

 

[steelsoldiers]

Will. 1400 degrees ? is this because there is not a turbo to cook? i did not realize that we could run them this hot. i have been keeping mine down to 1200. probably out of old habit.

It's not the turbo that should worry a diesel owner with high EGT's, it's the melted pistons. Of course, once a piston goes, all kinds of crap will go downstream and take out the turbo. At least you don't have that to replace in a NHC250. For maximum longevity, I would keep sustained EGT at 1250 or below. Short bursts above that won't melt the pistons because drag racers and truck pullers will run 1400-1500. It's that long pull up a hill that will get you. You can control the EGT's with you right foot, but it's a lot nicer to be able to mat the pedal without worrying about #6 vaporizing.

 

[jwaller]

Re: RE: NHC250 needs more power

thats odd about your low power, because the 819 with the 1200s weighs 36k, (a LOT more then your 81, has all the power it needs, it will do 60-65 easy (long hills is another story), i have to back off the rpm a bunch to keep from running over a deuce if its in front of me.

well ron here is how I figure it.
truck by itself weights about 22k
truck with 146 29k
truck with 270 39k

all weights are per the scales at GL.

Truck by itself will go full speed with no problem
truck with 146 would hold speed on all but larger hills.
truck with 270 will not hold speed on any high or grade. loses speed quickly and never recovers.

compared to yours I think I need more fuel. it will blow a light haze of smoke when pulling but not a think black cloud like the deuce or like your 819.

I know turning these 1600's will take more power and be harder on the truck but it just doesnt have the hp to do what I want it to do. So thats my problem and I have to solve it somehow.

I have replaced the fuel filter 4 times in the last 2k miles to no avail. I have run 4 cans of diesel doctor thru the system at the proper mixture.

 

[jwaller]

Will. 1400 degrees ? is this because there is not a turbo to cook? i did not realize that we could run them this hot. i have been keeping mine down to 1200. probably out of old habit.

It's not the turbo that should worry a diesel owner with high EGT's, it's the melted pistons. Of course, once a piston goes, all kinds of crap will go downstream and take out the turbo. At least you don't have that to replace in a NHC250. For maximum longevity, I would keep sustained EGT at 1250 or below. Short bursts above that won't melt the pistons because drag racers and truck pullers will run 1400-1500. It's that long pull up a hill that will get you. You can control the EGT's with you right foot, but it's a lot nicer to be able to mat the pedal without worrying about #6 vaporizing.

this is great info. just what I was looking for. Do you all like to mount your EGT such that it samples all the cylinders or is there 1 that likes to run lean and you look at that one?

also what EGT should a stock 250 run? so I can judge where mine is now as compared to normal.

 

[Cdub]

RE: Re: RE: NHC250 needs more power

When the in-frame engine overhaul was done on my NHC-250 Cummins, I had asked the mechanic about more power and he said " If you want more power you have to change some Iron in the engine...." and if you do. One thing leads to another...ie change this you have to change that...and so on and so on.......

 

[steelsoldiers]

this is great info. just what I was looking for. Do you all like to mount your EGT such that it samples all the cylinders or is there 1 that likes to run lean and you look at that one?

also what EGT should a stock 250 run? so I can judge where mine is now as compared to normal.

In my 5.9L 12v Cummins, I ran the probe in the rear passage of the manifold right before the turbo. The 5.9L manifold is Siamese'd so the probe was picking up the rear three cylinders. 5 and 6 are usually the first to go because of cooling issues. I don't know how much of this info correlates to the NHC-250 since I don't have one in front of me. Diesels don't like to run rich. Excess fuel equals incomplete combustion with lots of black smoke and high EGT's.

You could always run a methanol unit on it to keep the EGT's down on long grades. Nitrous would help burn off that excess fuel too if you want to drag race your 818.

 

[spicergear]

How about a turbo with only 3-6psi? Ought to give another 100#tq huh? Maybe save some bread and get a big cam 350 or 400 Cummins...may even be able to find one with a Jake on it--

 

[DaveP]

Well like i said, i like to keep the little 250 in the XM818 1200 or below on the pyro. one of the reasons i asked about the temp without a turbo is we always had to add a little to the reading on the pyro if the probe was mounted after the turbo. this was done so if the probe burnt off it would not crash the turbo on its way into its next life. still boils down to without piston coolers they get hot quick when the fuel is increased. set the top end of your engine and it might make enough of a difference that keeps you happy. and on the bigger tire question, when i put the 16's on the M819 it robbed any power that it ever had. it will Cruise real nice top end on flat roads but hills kick its hind end fast. oh and i can throw a flame about 2 feet.

 

[AMGeneral]

Took some time out this evening to turn up the fuel on the NHC 250 in my M816 wrecker,as per earlier posts on this subject took it a little at a time with the screw inside the throttle shaft(BTW the plug inside the shaft was plastic on mine,probably the results of the pump rebuild 2 or 3 yrs ago).I ended up turning the screw 1 complete turn counter clockwise,really helped the truck feel more like a "somewhat awake hippo" verses a "dead elephant".Before the truck would blow out a slight haze on acceleration or under load.Now it renders a definite black smoke and has a somewhat noticeable power difference.Now I just need to change the button to get it to turn up to 2450 rpm for that 3 to 4 shift hole plus install a pyro on it.Not really interested in top speed or higher speed,just trying to mantain better speeds on hills.

 

[Gamagoat1]

OK ,
Here's what happens when the fuel is turned up on the NHC250 in a M816.
The high rpms shattered the oil rings on #3, the pieces destroyed the piston and liner. #4 is just burnt, the skirt is gouged and the liner is destroyed. The bearings are like new,
The engine has very little wear on it but the fuel has been turned up at least a full turn at rebuild. All the other pistons and all bearings are fine, so it looks as though 3 and 4 are the critical ones.