Pyrometer Limits

[slp20045]

well my 7.3 has no turbo
and the manifold wold have to be removed so i installed it at the y junction on my exhaust
and i just tried it out and i didnt get above 475 WOT on the hiway so do u think i could turn the fuel up more ?

 

[slp20045]

P.S im also running Biodiesel since it likes it alot better and its a hell of alot cheaper

 

[The Warden]

I would strongly recommend re-locating the thermocouple as close to the manifold as you can get it. It doesn't have to be in the manifold itself, but you can get it in the pipe an inch or two from where it connects with the manifold, and you'll get a much better and more accurate reading. It wouldn't surprise me in the slightest if you were losing 200 or even 300 degrees between the manifold exit and where the two sides join together...and, it's not consistent enough to be able to always say you're losing the same amount.

Just my $.02...you could PROBABLY turn it up some, but I can't say for sure since the probe's so far back...

 

[lpennock]

According to my book on the factor turbo IDI there are a couple of things that could explain why the Cummings lives at higher tempatures than our IDI likes.

1. The turbo motor has a Piston head that was anodized for crack resistence so it could better with stand the pressures and heat caused by turbo charging.

2. The factor turbo motor also had an improved head gasket with a heavier fire ring and armor to withstand the higher firing pressures and temperatures.

3. They also switched to Keystone tip and intermediate rings which is suppose to improve ring life and prevent sticking.

Not sure how much of this applies to the Cummings but since it was designed from the ground up to be a turbo motor it probably has a lot of the features that were found in the factor turbo IDI.

 

[cetanefreek]

as far as EGT is concerned, I think #1 and #3 may apply, and the Cummins does have the keystone rings, however it does NOT utilize anodized pistons.

 

[MIDNIGHT RIDER]

While we're talking meltdowns, something that has always puzzled me is --- why are pistons made of aluminum ?? Why not steel ??


Way back in the dark ages, ALCO started turbo-charging some of their prime-movers, with the result that they started having piston burn-through issues.

They re-called all the turboed engines and replaced the pistons with cast-iron capped pistons = end of problem.

 

[MR.T]

well my 7.3 has no turbo and the manifold wold have to be removed so i installed it at the y junction on my exhaust and i just tried it out and i didnt get above 475 WOT on the hiway so do u think i could turn the fuel up more ?

I placed the thermocouple in the exhaust manifold between 6 and 8 (back two on on the drivers side). It's very easy to drill and tap in place, it's cast iron. Nor worries about the shavings without a turbo.

Mine will top out at 1250 F at full load (3300 RPM and full throttle on a hill). And, the pump is not turned up. The exhaust temperature rapidly cools as it gets further away, and I don't think there is any reliable coloration to somewhere down stream.

 

[MR.T]

While we're talking meltdowns, something that has always puzzled me is --- why are pistons made of aluminum ?? Why not steel ??

Less reciprocating mass, which lowers bearing loads and allows higher RPM.

 

[lpennock]

While we're talking meltdowns, something that has always puzzled me is --- why are pistons made of aluminum ?? Why not steel ??

Aluminum cools faster so it doesn't load heat as bad. That is the main reason aluminum heads on a gas motor allow more compression which equates to more power.

 

[slp20045]

ok well if it is placed in the manifold what would be the highest temp it could withstand

 

[MIDNIGHT RIDER]

ok well if it is placed in the manifold what would be the highest temp it could withstand

That is sort of a loaded question that would depend on several factors, one being engine timing.

Many claim that advanced timing lowers EGTs; but, that is not quite the case.

Advanced timing keeps the combustion heat inside the cylinder longer, allowing it to cool somewhat before it exits into the manifold, thus "fooling" the pyrometer into giving a reading that is somewhat lower than the actual EGT.

Retarded timing does the reverse and actually gives a more accurate indication, due to the heat getting into the manifold quicker.

The health of the oil and coolant systems play a big role in what is safe EGT.

A piston that has good clean cool oil being generously sprayed into it's bottom side, operating inside a cylinder that has a clean healthy water-jacket with clean fresh coolant being generously circulated around it, can live longer in higher temperatures than one that suffers from poor lubrication and questionable cooling.


To be absolutely safe, one should stay below the melting point of whatever aluminum alloy that his particular pistons are made of.

 

[slp20045]

so i guess thats the million dollar question then. what is the melting point of stock 7.3 non turbo pistons. and i change the oil every 5,000 miles and i use Mystic Synthetic Blend 15w-50 engine oil but like i said before that im running biodiesel cause it lubricates the fuel delivery system alot better then the ULSD on the market today plus it seems to run about 20 degrees cooler with it also and its cheap so its a win win in my book

 

[slp20045]

also does anyone know where i might find a slightly used injection pump and injectors worth the money?

 

[lpennock]

also does anyone know where i might find a slightly used injection pump and injectors worth the money?

When you can buy brand new injectors for about $30-35 each I wouldn't waste time with used ones unless you just happen to know the exact history of them. As cheap as they are it isn't worth fooling with used parts IMHO.

 

[slp20045]

okie dokie well i just got done turning up the old pump and she blows some pretty serious coal when pulling a hill and i still didnt get above 500 degrees after i moved the pyrometer to the manifold between #6 and #8 cylinder so do u think it can stand to be turned up more or does ambient temp play a role in it as well?