Maybe one of you guys can clear something up for me. I've been reading on some of the before and after results of adding ceramic style blankets to the exhaust, turbo, downpipe. I believe I understand most of the results(decreased lag,etc) but the one result that confuses me is the approx 100* egt increase that some people are seeing and thinking of that to be a negative result...Please help me understand if I am wrong, but I would think that WHILE their pyrometer is reading a higher egt where it is located, the temperatures actually inside the head and combustion area would be a touch lower(than before) since the gasses are leaving faster out the exhaust ports of the head AND now that heat has been transferred down the line (so to speak) and it's consequently showing up on the pyrometer as an increase in egt, yet the crucial area we're concerned about has decreased. Make any sense? If that was correct, wouldn't that mean that for a particular application, given say (before the modification) a safe temp of 1200* constant, would that mean that now a safe temp of 1300* constant. I haven't read many before and after results on the coatings, maybe someone can post some results on that too.

I know I wouldn't want to see higher temps on the pryo than what i've come to feel safe with.
I suppose a compromise might be this particular instance would be another modification that reduces egts at the pyro back to the 1200* (such as porting, i dunno), just something that would get you back to your known safety zone.

 

i have a head, ats manifold and a 12cm ex housing getting ported and coated. i am going to dyno before and after. the coating are going to be inside and outside. i will inform every one the results when done. i will dyno with a stock manifold, stock exhaust and a similiar 12cm ex housing. then swap it all over to the ported/coated stuff and dyno again. this is more of a test to see how well the porting and coating work on a diesel. it will be in a twins set up with a ht3b that is stock on the bottom. and it will be on a stock head gasket at 50 psi max. mike

 

WOT,

i understand what you are saying: without the coating the combustion gases cool in the manifold whereas when you coat the manifold the gases do not cool as rapidly and the result is in the gauge. that sound correct? maybe someone needs a reading at the port and in the normal pyro location then compare the readings with and without the coating to find the 100* difference. it sounds reasonable, heat = energy and the more heat you have at the exhaust housing inlet (from the coatings keeping the temperature up in the manifold) the more effective it will be at creating boost. it sounds like they (the coatings) are doing what they are made to do, according the numbers in your post.

Pat

 

where and what kind of money for the coating job?

 

You can buy an ATS with or without a coating, not sure if there are different coatings and which one would be the best.

 

I think you are correct. EGTs would likely NOT change (in reality) from coating a manifold. But the MEASUREMENT of those EGTS could very well reflect a difference.

Insulating the exhaust reduced heat loss in the exhaust gasses, and makes them flow more easily. But it WILL make the turbine housing/manifold/piping run hotter, and this may make the pyro think things are hotter in the flowstream.

I think insulating the exhaust side would help a lot in cold weather with warmup times.

jlh

 

Oh-- for coatings, I like Swain Tech. Doug Swain is former head of coating and materials research for GM.

http://www.swaintech.com/

Click on Racing..

 

WOT you are 100% correct. And you could even take this one step further and suggest that since the exhaust gasses entering the turbine are hotter and contain more energy, that you will make a tad more boost which would then lower the actual combustion chamber temperatures.

You are absolutely correct, in that people considering the slight increase in MEASURED egt's as a bad thing are in fact wrong and are not properly analyzing the situation.



Kevin

 

thanks for the response guys...a couple more thoughts on the issue come to mind...so for that given case, the now the elevated measurement the pyro is displaying is allright for inside the engine, ok, now what about the turbo, can they withstand the sustained increased temperature? And up to what temp? Different for different turbos, or is there a general rule of thumb? It would seem to me that IF possible you would want to insulate the exhaust before the turbo up to the highest possible temperature that the turbo could sustain(given that without whatever insulation modification installed, you we're still ok on the original egts). After the turbo, well, that seems to be an area of a lot of discussion.

on a similar note I just finished reading an interesting thread, which made me wonder if a "TAG" made in reverse type fashion would work on the exhaust housing. here's a link to it
https://www.dieseltruckresource.com/...threadid=30171

 

Yep, how bout that Zino guy

 

Guys, the last few comments, seems to me, to be slightly off base and not looking at the whole picture.

Posted by HONN - "Insulating the exhaust reduced heat loss in the exhaust gasses, and makes them flow more easily. But it WILL make the turbine housing/manifold/piping run hotter, and this may make the pyro think things are hotter in the flowstream"

"Flow more easily"...I wonder? Reducing the heat loss will increase pressure, making them flow more quickly, but is that the same thing?
"...make the pyro think things are hotter..." My pyro can't think...it just measures what is there!

Posted by 600 Megawatts - "take this one step further and suggest that since the exhaust gasses entering the turbine are hotter and contain more energy, that you will make a tad more boost which would then lower the actual combustion chamber temperatures."

I think more boost = possibly more fuel burned = higher temps? Yes, turbo should spool a bit faster but a net reduction in combustion temps is IMO, questionable; and more boost, for many who are already outside the MAP of their turbo, is of no value.

What bothers me most about this discussion is ignoring the effects on TIP or drive pressures. Many members running higher HP have undersized turbos and are dealing with excessive TIP. I would expect any increased retention of heat and pressure in the manifold and the turbine housing will only compound this problem. Those of us playing with 1500* EGT's don't need ANY heat retention resulting in more drive pressure and higher chamber pressures.

WOT - I'm no expert, but in my mind, we don't "transfer the heat down the line" with coatings and thermal blankets...we just add to it. It works on a gasseer race car without a turbo (ie. Zino's comments) but I believe a turbo changes everything. The way it was explained to me by a thermal blanket mfg. is formula I racers use these features to keep the heat from melting wires & hoses under the hood...not to increase performance.
RJ

 

RJ said:I would think that reducing heat loss will DECREASE pressure. Most gases expand when heated (increasing pressure for a fixed volume). Conversely, as they cool, they contract (which reduces pressure for a fixed volume).

The problem here is we are NOT dealing with a fixed volume-- it's open-ended, so we are dealing with DYNAMIC pressure, which behaves differently.

As to whether or not flowing more quickly is the same as flowing more easily, I can't say. It would seem to beg the question of efficiency: i.e. how much more energy does it take to increase flowstream energy by X amount.

Also, he said:In this ^^^ scenarior, it is ASSUMED that more boost allows more fuel to be burned. Thus, the assumption is that someone is SEVERELY overfueled. However, we know that high EGTs when someone's smoking actually come DOWN as the smoke clears up. This tells us that more oxygen burns the fuel more completely and AT A FASTER RATE. *THIS* is what lowers EGT. High EGT is caused by a shortage of oxygen which SLOWS the combstion process. In an O2-starved cylinder, the fuel is still burning as the gases are exhausted, and THIS is your source of high EGT.
So based on this reasoning, I'd say that raising the air intake (note: I didn't say just raising boost) should LOWER egts, not raise them-- even if someone is overfueled.

RJ is 100% correct, imho, that more boost does no good to someone who's already way off the map of their turbo's compressor.

TIPs are important, and you guys playing with 1500° EGTs might want to reconsider insulation your exhaust.

Corrections to any logic errors I made are welcome.

jlh

 

Sorry if I misunderstood.

I took your words..."reducing heat loss" as a sort of double negative..meaning increasing heat retention.
To me, holding heat that might otherwise dissipate is equal to increasing heat...thus increasing pressure!...No?
Your absolutely right about my comments regarding more boost allowing more fuel to burn! I was "looking in the mirror" so to speak, when I said that. Does not apply to all trucks, only those of us fighting some over fueling.
RJ

 

You must always remember what the turbocharger is... It is a heat recovery device. This heat recovery device is a gas turbine which is coupled to and drives a compressor. The gas turbine is an enthalpy machine. It operates based on the enthalpy difference between the inlet and exhaust. Higher inlet temperatures equal higher enthalpies. Higher inlet enthalpies means there is more energy available to do work. Thus more of the wasted exhaust heat of the engine is converted into useful energy in the compressor. Now that being said, if you are already outside of the compressor map for your turbocharger, than this additional work does you no good. If you are not outside the map, then this additional work is beneficial. BUT under no circumstances whatsoever, does the release of heat from the exhaust manifold and turbine housing into the engine compartment do you any good at all.

And once again, I have stated this several times on this forum.... EGT's are nothing other than a measurement of the temperature of the exhaust gasses in the exhaust manifold. We happen to use this as a general indication of average temperature within the combustion chamber and thus an indicator of potential piston and/or exhaust valve damage. Nothing else, nothing more. But dozens of factors, especially timing, change how a given EGT relates to a given mean piston/combustion chamber temperature. Insulating the exhaust manifold and turbocharger will increase the measured EGT in the manifold but do nothing except perhaps lower the temperatures which we really care about within the combustion chamber.

Look at 99% of the large diesel engines in the world, used in generator applications, marine engine applications, you name it, in almost every single case the manifold and turbine housing are insulated. period. You have a heat recovery device, a turbocharger, let it recover the heat, don’t release it under your hood.


Kevin

 

I agree with what's been said. And I think it's interesting to note that putting on a higher flowing manifold or porting alone(without insulating/coating), could make things a little worse in some scenarios unless the stock manifold configuration was already limiting the volume of gas available at the turbo inlet.

Keeping with the insulation/coating theme, I would also think that doing that to the down pipe and rest of the exhaust(as feasible) would be beneficial for the same reasons as we've been talking about. And I think some benefits could be had with putting a pyro pre and post turbo, as well as taking pressure measurements pre and post turbo simultaneously. Then test and tune with different sized and insulated exhausts, to help optimize your turbo's efficiency for your particular setup. For the do it yourselfer, it could be done cheap enough.
IMO, I think you would find that by not insulating the down pipe you would be decreasing the enthalpy difference. As would too large of exhaust.