I've had my 96' Dodge Ram TD for only two weeks and thanks to this forum i've learned a ton! i have a few questions still to be answered... EGT's seem to be of high importance with our trucks, but is it really the EGT that were all worried about or is it really the intake air temperature? or the turbo's oil temperature? I'm very familiar with gas engine turbo technology and how important it is to keep the intake charge cool to prevent detonation, so when everyone says make sure your EGT's don't get to high is this a generalized way of safegaurding your engine? Let's say two identical trucks are running 1500degrees EGT after the turbo, but one truck has a more efficient intercooler (water/air, or larger) wouldn't that make the EGT numbers irrelevant? Has anyone tried the benefits of a water cooled bearing jacket in their turbocharger?
Here's another question that sounds pretty stupid but i'm never going to know unless i ask. When i first started reading about modifiying our trucks i read about some guy saying before you BOMB your truck you should do this... i was like what? BOMB your truck? what the flip does that mean? After further reading i figured out that this didn't involve C4 or detonators, but couldn't figure out how it had anything to do with modifying the truck? What, Where, when and why did this start? Thanks, and go easy on me.

 

BOMB- Better Off Modified Baby

As far as egts go, this is how hot your pistons are seeing, and if you hold it above 1250-1300* for too long you'll melt your pistons. Somewhere there is a thread that compares turboed gassers to diesels. It was pretty interesting all the differences there were. I'll try and scrounge that up for you tonight.

 

BOMB---Better Off Modified Baby

Most floks on this site are measuring EGT between the engine and the turbo, aka pre turbo. Measuring from that location yields arguably the best window into what's going on in the combustion chamber. Too hot--pistons melt. It may not be that simple, but when I think of it that way, I tend to err on the side of caution while watching the gauge. Monitoring egt POST turbo will generally yield #'s that are between 200 and 450 degrees less. The gauge is also less responsive on the post side, so the data you're seeing may already be old news to the motor.
hope this helps a bit.

BTW---welcome to DTR!

 

Due to a faulty pyro this engine was driven for approximately 15 minutes at 1400°
The engine still ran before it was torn down but sounded horrible and lacked power.
The only mod besides cheap gauges was the stock plate slid forward.

 

Another shot after cleanup

 

So what are the EGT guidlines? What temps are safe and for how long can they be maintained? if i'm running a 14 second quarter mile how hot is it safe to run?

 

1300* for more than a short interval will make aluminum soup. Draggers often see 1500* at the end of the track, but it's only for a SHORT interval. Just because the pyro sais it's 1500*, doesn't mean the pistons are 1500*. They are subjected to oil cooling from below, and airflow keeps them cool. HOWEVER, for sustained periods of that much heat, the piston cooling system becomes over burdened and fails to remove the heat.....you end up with infidel's images. Aluminum actually melts at somewhere around 1100* (please correct me), but EGT's can be higher because at 1300, the pistons aren't actually 1300...make sense? You'll notice, unlike a gasser, when you chop the throttle on a diesel, EGT's can fall 500* in a blink of an eye. This is because of the massive airflow in a diesel, and the lack of throttle plates to restrict that airflow at an otherwise "closed throttle position". A diesel always reaches full air volume potential for an rpm even if there is no fuel to burn and accelerate the rpm. This is why they cool so fast. So if you spike a run at 1500 no big deal...chop the big foot and she'll be at 700 in less than a couple of seconds.

As far as intake temps go.....cooler is better as in any. this creates density and density provides for more oxygen to burn fuel to create the BTU's that drive an engine blah blah blah. Obviously we don't worry about knock in a diesel like a gasser does. But hot air is inefficient air. Yes high intake temps can lead to high EGT's. This is why wastegate setings on small turbos can be dangerous. If you go past a compressor's efficiency map, the air is hot, and make EGT's hot. Not to mention overspeeding the turbo and melting it down. Our intercoolers are okay to about 50 psi, but more than that they are a bottleneck, and an aftermarket is needed. A larger compressor will deliver a higher volume of cool air, this is nothing new to you I'm sure. But as with a gasser that won't spool till 3000 rpm with a top end designed turbo, a diesel does the same...not 3000, but much higher than usual, which causes lag. The solutuion to this equation is sequential twins or a custom built hybrid to give high airlflow, but low spool up. from this point on, the opinions and theories are many. Bottom line, move the air to burn the fuel, and you'll have no EGT issues with normal driving. Aftercooling the aircharge will only go so far, and water/meth will always help too, but air VOLUME is the target of primary concern. Hope I helped you a little mr. hydrospeed.

Chris

 

Draggers and Sled Pullers see way more than 1500 for short intervals. Where to stop is all a matter of how comfortable you feel

I'm sure infidel will agree, intake temps can be too cool. This is one reason blocking the grill is a good idea in the cooler months. Optimum intake temps are between 50-90 degrees.

 

Not to hijack this thread but I have a question about my EGT's. My pyro is post turbo, installed at the casting dimple in the turbo outlet elbow. Anyway the highest temp I've seen to date has been 750 degrees on the gauge, say at 10 psi boost. So however you want to do the math you can. I'm guessing that is around 850 degrees pre-turbo?

I haven't seen a higher temp than this even with extended highway driving at heavy accelerator positions, up and down hills too. I'm thinking that's good right?? Once I add the fuel plate and other mods the EGT's will ride so it should give me a little extra cushion. Correct me if this isn't right. Thanks

 

Amos: General rule of thumb is that post turbo readings are 300 degrees lower than pre-turbo readings. So if the highest you have seen is 750 degrees post turbo then pre turbo that would have came out to about 1050-1100 degrees pre turbo. I dont like post turbo probes because i dont like math, and i like bieng able to look at the gauge and know for sure what my temps are. The fuel plate probably wont raise your temp's that much. My truck never got to 1300 degrees but once pulling a 32ft goosneck with round bales on it with just the fuel plate. After i installed the 3k GSK, i can now hit 1450 degrees by the time i make it to 60mph unloaded! I always let out of it just as soon as i hit that, and its safe because many here run MUCH higher temp's, but it is scary. So basically when you start modding, 1000 degrees post turbo is about as high as you want to be for any length of time. spikes of 1100-1200 post turbo are fine. Just dont hold it there for any amount of time. If i were you, i would pull my probe from the post position and drill and tap, and put it before the turbo in the manifold. MUCH more accurate, and reassuring, and not hard at all to do. Just screw a bolt or something int he threads you have it tapped into now or something. Post is fine, but i dont like them myself just because i dont like guessing at stuff, and trying to do the math while my temperatures are climbing, because likely by the time i can figure out what my temps were 10 seconds ago my pistons would be melting

Eric

 

Another hijacker. How would one go about moving the pyro probe into the manifold? I worry about drilling and getting metal into the engine or turbo. Should I unbolt the turbo and drill with a vaccum, or take the manifold off...? My egt tops out at 650-700 post turbo.

 

I separated but did not remove the turbo. I then taped off the turbo inlet with a couple pieces of 2" wide masking tape. I drilled with a slender magnet underneath the hole inside the runner. Once done I started the engine with the turbo off just for a second to blow out the filings I might have missed.....that might have been overkill though.

Chris

 

Chris' method is the one I use except I just slip a piece of cardboard in-between the turbo and manifold, fire it up when I'm done.

 

x2

 

I also did what Infidel suggested. Works great.

Eric