Individual exhaust temps

Greenspeed

Greenspeed

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Nov 15, 2011
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Hi all,

I asked this a while ago, but the thread seems to be too old to comment on. I never got around to posting the data we collected, so here goes.

To recap, as you can see in the data, there is a large difference in cylinder temps. Pulled the pump off this winter and got it on the flow bench. Am told that it is quite balanced above about 1800 rpm. So that's out.

We did a little experiment before pulling the pump though. I was going to swap probes 1 and 6 to verify, but I could put my hand on the 6th runner and doing that to the 1st runner caused a funny smell. I figured that was a good enough test for the TC's. Next step was swapping injectors. Zero difference whatsoever.

The EGT only graph has the average value thrown in, which is pretty much identical to what showed up on the ISSPRO dash gauge, the TC for which was in the WG pipe between manifold and top turbo.

nBHY6.jpg


The second one is of the warm up and run, continuously. Ambient was about 50*F that morning, IIRC. As you can see, cyl 6 was coldest throughout, with a massive difference at idle. I am told this is expected though because the pump is not balanced for idle, only top end. The inset is just the actual run, stretched out.

QzFjz.jpg


Any body have any thoughts on this?

Thanks!
 
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My initial thought, would be that the hotter cylinders are getting less air. Especially since you have already checked out the fueling. Are you tuning a plenum intake manifold? Are you measuring drive pressure at each runner too? Could be higher on the hotter cylinders, not allowing enough clean air into cylinder.
 
We are not measuring drive pressure at each cylinder. The stock plenum was removed and replaced with a box type after the head was CNC ported by C-TECH. Each cylinder should flow the same? I would think that if drive pressure was different between cyls, it would be lowest for 3 and 4, since they have the most direct route?
 
Very rarely will you ever get all cylinders spot on.

AVG is about 250-300 spread.

Here's why

Each cylinder will get more fuel,Air, than the others.

Second, each bore will wear differently due to difference in ring gap,avalible fuel, and heat in each bore.

EGT's also change due to the difference in compression across the bores, from slight variances in valve lash setting, to not so close accualy camshaft lift and duration on the lobes.

I've seen Bone stock cummins and duramax have protrusion that varie +3 thou, this can make changes to static compression and dynamic to a smaller margin but it's still a contributing factor.

As mentioned above equal boost and back psi make a big difference as well.

Just a few thoughts.
 
And would it be a good idea to get them to all produce the same amount of heat? By say "balancing" the pump based on egt's on the dyno?
 
Greenspeed said:
And would it be a good idea to get them to all produce the same amount of heat? By say "balancing" the pump based on egt's on the dyno?
Click to expand...

Yes, you'll find that in a race engine the closer the better, little gains always add up.
 
A stock CR Cummins will run a 150*F spread, an old 12v might be more because of the head flow differences.
 
Would either of you two mind sharing the data that supports what we are seeing? Thanks!
 
Lets not move on without stating that hotter running cylinders will always have HIGHER temperatures than ones without enough oxygen molecules. Deprived cylinders will produce less heat period. Also reversion plays a role with in-cylinder temps because of displacing the much needed oxygen from both flowing backwards because of pressure differentials between the exhaust manifold and the cylinder and the cylinder itself and the intake tract.

Like Diesel Power stated, variables are numerous when speaking of any aspect in the combustion process and timing. If you flow well going the right direction, you just may be creating a situation that will flow well backwords too! Also if there may be detonation happening that can lower your EGTs as well. You can have audible and non-audible detonation.

Have any coatings been put into thought as far as keeping the heat as much as possible within the burn? If you can harness great head flow in on each induction port, great flow in the exhaust port to effeciently turn the turbine, you may be able to reduce your reversion/contamination without having to employ anti reversion attributes. If you have a more homogenous mixture throughout your chamber your burn will not only speed up if it lags, it will be more complete and there should be more stable readings between cylinders and less smoke.

Another thought, if we have stable good running temperatures out exiting exh. gas velocity will be better than some cylinders that are cooler. This also takes into consideration that the exhausting port is shaped & sized correctly for the cylinder head being utilized.

Great topic, the graphs are interesting. Thank you for posting! I will be following this one.
 
Its not often in a diesel if things are running well, but if in any area in the chamber, we have enough fuel accumulated, enough pressure from both mechanical compression and the advancing flame front the heat built up can ignite this area of non-moving mixture. Detonation can happen in any engine, from engine to engine, the circumstances are just different.
 
LMFAO

You know what happens when you stop detonation in a diesel. It stops running.
 
well if you swapped injectors that would mean they flow the same. But do the individual ports on the pump flow the same and at the same time in the piston travel? wonder if theres a variation there and if its possible to measure.
Also you may have variance in compression, but that would show with a compression / leakdown test.
On inline motors with one carb per cyl its normal to see the inner cylinders need richer jetting to compensate for the extra heat. But its possible to balance cylinder vacuum via throttle butterflies, none of which apply to a diesel =(
 
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I have to jet my 2 cylinder snowmobile engine differently to keep egt's the same. That's completely separate intake and separate exhaust until the can, the cylinders are identical as well. I would imagine that a 6 cylinder with one block, head and so on could only be worse.

It'd be neat if you could measure cylinder pressure at ignition and tune with that.

Sent from my DROID X2 using Xparent Blue Tapatalk 2
 
If you can build a machine that can keep up with the rate of normal combustion at any rpm, you should be able to tune according to your readings. Being a change of settings or tuning your head by material removal or parts change along with a cam etc etc. That would be a kool machine to learn from and use. I am not sure what books you read SINNER, or heard from whomever, you can believe what you wish, the burn rate of detonation is along the same lines of igniting an explosive. Upwards of 2,000 FPS of flame speed I believe maybe more? The normal combustion process begins sometime prior to TDC after ignition delay and ends sometime after TDC. It is not as fast as a detonation period.

There is a point ATDC where our combustion becomes useless to us due to the effective work being applied to our piston ends, we just hope that pressure is maintained so we can have a good blow-down phase and evacuate our cylinder effectively.

If you look at CATs 3406E, probably other engines too, they utilized stainless steel sleeves within the exhaust port because of the materials quality in not transferring heat away from our exhaust gasses used to spin the turbo.

Things that I have thought about following this topic.

When should we open our exhaust valve(s)?
How quick should we open our intakes & exhausts when filling or evacuating the cylinders?
How quick & when can we close our intakes & exhausts?
Should we utilize coatings or inserts?
What should the fueling be timed at?
What quantity of fuel is going to be injected?

I guess the two main factors we should be looking into is 1 balanced cylinder to cylinder pumping of fuel which all of you have stressed already and 2 heat control.
 
AVG is about 250-300 spread.
Click to expand...

You're an idiot, and you didn't build your motor either.

I posted this in your other thread, this is just playing around on the dyno:

[ame="http://s30.photobucket.com/albums/c338/texashwhu/?action=view&current=IMG_0894.mp4"]IMG_0894.mp4 video by texashwhu - Photobucket[/ame]
 
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