At what point in bombing do you lose reliability on a 24 valve.

 

I don't know that there is a real number that everyone would agree on. It also depends on how much fun you want to have.

 

I was just talking about this with a friend that has over 700HP...as he tore the engine apart and back together again, doing many mods, he said that at 700hp and twins that get 50-60lbs of boost, the cylinders were just starting to show a bit of wear...the crosshatch was feeling the pain...

 

Everyone will have a different opinion here (imagine that)....

But, I would think that once you get much over the 400 hp mark, you MAY shorten the lifespan of the engine. Also, what you use your truck for and how you drive it determines lifespan as well.

 

Hmm good area to stay in.........

350hp at the ground.

That is in my opinion pretty safe ground.
Although, a growing number of us run around with 450hp-650hp at the ground in daily drivers, and retain our reliability.
There are some exceptions where guys are running over 700hp in a daily driver.

--Justin

 

[quote author=PourinDiesel link=board=7;threadid=22932;start=0#msg215013 date=1069976163]
Hmm good area to stay in.........

350hp at the ground.

That is in my opinion pretty safe ground.
Although, a growing number of us run around with 450hp-650hp at the ground in daily drivers, and retain our reliability.
There are some exceptions where guys are running over 700hp in a daily driver.

--Justin
[/quote]
Yeah, that's easy for you to say... You live down the street from Cummins.

Seriously. That sounds like a good place to stop (350).

Gary

 

I think that you can bomb the Cummins pretty good before you lose reliability. What you do lose quite early is the foolproofness. The hotter the truck gets the more gauges are to be watched and the more stuff has to be considered.
I don't think that you lose reliability from having the high hp, but from using them most of the time. (I can't imagine going WOT for a prolonged period with a 700hp Ram on a public road- problems other than engine wear would be more imminent after 10 seconds)

Just my 2c

AlpineRAM

 

[quote author=AlpineRAM link=board=7;threadid=22932;start=0#msg215152 date=1069999160]
I think that you can bomb the Cummins pretty good before you lose reliability. What you do lose quite early is the foolproofness. The hotter the truck gets the more gauges are to be watched and the more stuff has to be considered.
I don't think that you lose reliability from having the high hp, but from using them most of the time. (I can't imagine going WOT for a prolonged period with a 700hp Ram on a public road- problems other than engine wear would be more imminent after 10 seconds)

Just my 2c

AlpineRAM
[/quote]
Strongly agree.

 

I would have to say around 450-500 to the ground is a pretty reliable truck.

 

I don't realy agree with most. I think anytime you up the power, you are going to loss life. I don't think anything is free in this world, and physics tells me for every action there is an equal and opposit action. Now this loss maybe fractional but it still is a loss. Think about it, you can not get more power out of an engine without causing more wear and stress. It is all related, more Fuel= more Power. Ok But at the same time more Fuel also ='s more HEAT. Both HEAT and POWER will create more Stress. There are many other relationships but this is just some of the more ovbious ones. So remember when you add power inhancments you will be reducing the life span and taking away from the reliability of the engine. This isn't anything new or grand, anyone in racing is well awhere of this constant struggle between more power and wear, and or reliability. That is why we are our own warranty station.

 

We're not talking about a Honda here.....we're talking about a Cummins. I assume that you've seen the picture of the connecting rods???.... these engine are built heavy duty. As a matter of fact, I recently read somewhere that the output of the 5.9L Cummins was purposly derated. There are a lot of guys running 350 horse or more with many, many miles and no problems. A matter of opinion I guess.

 

There are far too many factors that can contribute to a good or bad number.
It you have a dud from the start and you add power, then whatever glitch was in that engine will rear its ugly head. Human error or manufacturing glitches can be part of this.
Next thing to consider is proper lube, warm up etc.
Even a bone stock motor can meet an early demise if not run properly...and properly to one may be terrible to another.

So I go back to my old saying...

You wanna play...be prepared to pay.

Having said that...I ran with 400 plus for a long time hauling a large 5er. Then I went up over the head gasket threshold and once I o-ringed...it was fine again...safe temps, safe towing.

I played and paid a few times and knew what to expect.
It ran reliable as long as I knew what I was doing and what the engine was doing.

 

yep it's opinionated. you could say that joe donelly's truck that last made 799hp i see by his signature is very reliable. he tows his airstream trailer fine and goes off roading a lot (hunting, not mudding). in my opinion, 300-400hp is safe. it seems that a lot of people run a comp box and DD3's with an HX-40 or whatever and maintain good/great reliability. twin turbos then shoot the reliability down quick (imo) when the boost starts going above 60psi. i'm not saying that i wouldn't do it- far from the truth- just be prepared for when things break ;D

Tom

 

y-knot: I do agree with you on the point of more power equals more stress on the parts.
Your example of a tugboat's rod is not appropriate- as are the other comments about rod size as a measure of reliability or potential power output.
My opinion is that in the pickup application the power utilized over time will not change too drastically above a given point because even when towing there are other limits that will make the driver cut down power. Hence IMHO a 700hp ISB that is properly built will be quite reliable in a pickup, but would be unreliable in a semi or in a ship. (Due to the great percentage of full performance time these applications put on an engine)
Also the question about reliability is not a question about longevity. I think that it is possible to build a reliable (meaning starts in the morning, can be driven around without parts falling off) engine out of the IB that sports 500 or 700 hp. I don't think that these would sport good enough longevity for the commercial truck market, driveability for the average driver and foolproofness for the less gifted operators.

Just wanting to make my views clear.

AlpineRAM

 

In the mid 90's clark made a 25,000lb forklift that used the Cummins engine. I do believe it was identical to the marine engine.

I have worked on some of these with over 20,000 hours on them. In automotive time that would be the equivilant to about 650,000 to 800,000 miles.

Most operators use the throttle like an on/off switch, Idle or floored.

I would like to see 400,000 miles and I drive reasonably conservatively. Even with the added stress of extra HP, I couldn't see cutting that much life off one of these great beasts.

IR also usus the baby brother to our engine, while only a 4 cyl, and gets similar life.

If these engines last this long in harsh environments, with operators who don't care, imagine what they can do in the loving hands of a Dodge owner.

Just my 2 cents