Alec

"I truly believe, for people like this, there are gas powered trucks."

Dave: Why do you say that number six is the hottest running cylinder? I read some test results (from material touting Banks twin ram or whatever they call it system) and the #1 cylinder consistently had the hottest exhaust temps, which fits in with all of the lore about #1 running rich, wearing out the bore, etc. due to the mounting boss cast into the manifold just ahead of the #2 intake runner. So do you know something I don't, or did you mean that I should drill my new hole just before the #2 exhaust flange, ~6" after the #1 exhaust valve ?

Related to the probe in the middle idea, isn't bridging the two runners bad? I would think that a hole between the runners before they entered the turbo could set up a harmonic wave that would be detrimental to exhaust flow -- of course, maybe if you do it in the right place, it makes the flow better. Anybody have info on that?

Thanks,

Alec

Lil Dog

Those were my thoughts on the exhaust web. The pulsations in the exhaust manifold would start to interfere with each other if you removed the web completely. Thusly they ported the turbocharger to be twinned to the exhaust manifold and have the oscellating pulses meet at the turbine.

As for the absolute hottest cylinder, if you are running that close to the ragged edge, then you have other problems. Not withstanding the differences in the head for intake and exhaust flows, but if you have aftermarket injectors,well even the stock ones, the flows are not identical in terms of CC and your combustion temps are going to be different for each cylinder. If you have one "rich" injector you will cause damage sooner to that cylinder before the average EGT gets high.

As for the "industrial" engines, I am not talking 500hp highway engines. Rather 1000-5000HP stationary engines that are running at full load 24/7 only stopping for service. Generators, compressor engines and the like in remote locations. These units all have per cylinder pyros and I have seen engines drop valves and spit them through the turbo and the pyro head was bent, not broken.

I couldn't be bothered haveing a graph in front of me on a clip board to figure out the cylinder temps based on boost and post turbo temps.. And did I hear 1400°F Post Turbo? OMG!!! If you do the math thats about 1700°F pre turbo and my gauge doesn't go that high...If that was sustained for more than 8 seconds, I would be pulling the head to see what the corners of the pistons look like.

J-eh

Bushy

: ;D........1700*F ..... wusseys...... ;D

My 'ole Blunt Force Trauma machine has topped that by a good 100*F... oh, the pistons are round now......

No I wouldn't drill the web either...

Pastor Bob

hdm48

Ok, first I didn't mean to get midevil on the subject. Just making a point.
Just put the probe in the manifold like everybody else does. That's where mine is.
And most of the time I see the number 6 cylinder getting fried, not number 1. But I have been informed that number 1 is the hottest. So I stand corrected.
Opening up the seperator in the manifld will produce shock waves between the two sides. This is not a good thing. As you all know I'm sure, shock waves are what the exhaust uses to control scavenge and flow velocity. You all knew that right? What will happen is the shock wave from the rear will tell the front to stop flowing and POOF, all your power is gone and you have a very large cloud of smoke. Reverse this for the front.
But the turbo introduces the two sides together as they enter the housing at the turbine blades. Well, this is done in a controled manor. It all has to do with pulse timing veriances do to the unequal length of runners in the manifld. If you were to install a equal length header, you could do away with the devider. WOW, don't get me started on this. Just leave well enough alone. It works. BAAAA opps did I say that?
Anyway, useing more than one sensor is a waste of time with a street driven truck. But I do believe one needs to know the temp of the gasses as they leave the engine, not the turbo. The turbo is a big heat sink and if you change housings, you may get the same reading but the engine is melting. This is not so pretty good. I can't count how many times I have had to use meuratic acid to remove aluminum from cylinder walls.

OK, time to inhale

Dave

Alec

I am genuinely curious -- why #6 do you think? It was easy to believe that story about the big mean boss cast into the intake manifold that mugged Bo-Peep . . .

And on another similar but tangential note, how is it that you missed out on the discussion about turbo down-pipe diameter and its effect on performance in the 12valve forum. Seems like you might have something to say on the topic of optimizing exhaust flow . . .

Alec

hdm48

OK, so slap me up side the head. I missed a post. Wow, one little mistake and I'm labeled as a malcontent.

Just kidding.

Ok, why does number 6 fail? In all of the casses I have seen, number 6 fried because it wasn't cooled like 1-5 are. Unless a guy absolutely bakes the pistons, most failures are caused by lack of coolant getting to the rear of the engine.
Remember, the exhaust ports are surrounded by water jackets. And when the exhaust temps get high enough, steam forms here and sence steam rises it collects in the head and then pushes it's way down into the block.(even without steam, number 6 has the hottest wall temps) But by this time the piston in that cylinder has already started to expand beyond its bore size and starts to weld itself to the cylinder wall.
Once this starts, shutting the engine off is a bad thing. Running it at a high idle is your only hope to save it. But another thing has already happend, the rings, the piston has collapsed unto them and it's $$$ time.
If you are pulling a heavy load and you're water temp guage starts to bounce around, back off, you have steam pockets in the motor and disaster is just around the corner.
I have seen turbos turn the compressor side brown from heat. The motor still ran, but made about 5 hp.

ANYWAY, I got side tracked.
That is why number 6 fries first. If you think number 1 has a restriction, the next time you have the intake manifold off, look at the big chunk of metal the fuel filter mount blocking the air from getting to the rear.
Now THAT'S a restriction!!

Dave

Alec

Malcontent? How can anyone running DDIII's be called a malcontent?

That all makes sense, though. Thanks.

Now -- what about optimal exhaust design to keep velocity up and back pressure down?

Take it easy,

Alec

hdm48

According to the testing Piers has done, the ATS manifold offers a 18% increase in flow and this equates to a reduction in back pressure. Back pressure is stored heat, and that is what you are trying to get rid of. Once the cylinder has used up the heat generated to drive the piston, you don't want it anymore. Get rid of it.
BUT, if you port an ATS manifold, the flow really increases. Stock for stock, I feel the only real benifit from the ATS unit is the 3 piece design. But for $450 bucks I would have thought they would do a better job of matching the ports. My Mom could do a better job than they do.

Dave

Haulin_in_Dixie

I ported mine and could feel the difference. Everyone said it made no difference so I did not elaborate.