EGT Limitation

[mrx79]

Hi,

Due to a very small tubrine, my engine is EGT limited. With increased boost and increasing rpm's (redline is about 8000rpm) egt is the limiting factor, even with reasonable ignition advance, so advancing any further is barely an option to reduce egt's any more.

Because the engine is about 8:1cr it's thermal efficiency is also not very high compared to higher cr engines.

So i can use water injection to increase my det. threshold to be able to run more boost, but, 100Water and 50/50WM doesn't lower my egt's (some ppl say it should, but i never noticed it during my logs).

So do you guy's have any ideas what i can do to keep my EGTs low to be able to run the boost with water/WM i'am able to do det. wise?

Thanks in advance

[parmas]

Originally Posted by mrx79

Hi,

Due to a very small tubrine, my engine is EGT limited. With increased boost and increasing rpm's (redline is about 8000rpm) egt is the limiting factor, even with reasonable ignition advance, so advancing any further is barely an option to reduce egt's any more.

How much small the turbine is? When you say EGT limited, what temps are you seeing?

Because the engine is about 8:1cr it's thermal efficiency is also not very high compared to higher cr engines.

So i can use water injection to increase my det. threshold to be able to run more boost, but, 100Water and 50/50WM doesn't lower my egt's (some ppl say it should, but i never noticed it during my logs).

You are you using water/meth injection right? Have you tried to compare EGTs with and without water injection? How much are you injecting vs base fuel?

So do you guy's have any ideas what i can do to keep my EGTs low to be able to run the boost with water/WM i'am able to do det. wise?

There are ways to decrease egt. If you are into the 12.5:1 ratio enriching to 11.5:1 would decrease egt but you might loose power. What if you increase boost and decrease rpm? EGTs are mostly affected by engine rpm

Thanks in advance

.........................

[mrx79]

the turbine ar is a GT28RS 0.48ar on the T3 turbine housing.
I'am seeing:

/wo WM: 898°C @ 8030rpm / 220kPa @ Lambda = 0,769
/w 50/50: 906°C @ 8065rpm / 221kPa @ Lambda = 0,776

950°C is my personal limit, but i would feel a bit better if i can keep it a bit lower then that.
Because i know that the material of my exhaust manifold is not rated for that kind of temperatures and i would like to avoid cracking. But up to now it hold's pretty well.

Also my goal for this year would be to run more in the region of 12:1 or 12.5:1 if possible afr, but then i would definitly be above 950°C.
Also i'am planing for more boost, when i've fixed my ignition misfire issue.

What is your EGT limit?

I'am injecting 140cc constant 50/50 WM by weight.
This gives me a ratio of water to fuel of about 24%@4000rpm/200kPa falling to 8,6%@8000rpm/230kPa.

My question to the experienced guy's here: Is there anything with water injection which effects EGT's directly besides the normal "more advance, richer mixture" things which also are valid on a non-WM injected engine?

I thought about a second stage (for high rpm) of pure water at the TB or direct port inj. but this makes the setup much more complex and i would avoid any kind of unneccesary complexity.

[parmas]

Originally Posted by mrx79

the turbine ar is a GT28RS 0.48ar on the T3 turbine housing.

I NEVER KNEW 0.48AR EXISTS. 0.64 USUALLY IS.

I'am seeing:

/wo WM: 898°C @ 8030rpm / 220kPa @ Lambda = 0,769
/w 50/50: 906°C @ 8065rpm / 221kPa @ Lambda = 0,776

950°C is my personal limit, but i would feel a bit better if i can keep it a bit lower then that.
Because i know that the material of my exhaust manifold is not rated for that kind of temperatures and i would like to avoid cracking. But up to now it hold's pretty well.

YOU ARE ALREADY ABOVE AND BEYOND MAX SAFE EGTS. MAX SAFE IS ABOUT 825/850degC

Also my goal for this year would be to run more in the region of 12:1 or 12.5:1 if possible afr, but then i would definitly be above 950°C.
Also i'am planing for more boost, when i've fixed my ignition misfire issue.

COULD BE THAT YOUR EGTS ARE SKYROCKET DUE TO MISFIRING AND BURNING FUEL INTO THE EXHAUST

What is your EGT limit?

I'am injecting 140cc constant 50/50 WM by weight.
This gives me a ratio of water to fuel of about 24%@4000rpm/200kPa falling to 8,6%@8000rpm/230kPa.

WHY ARE YOU DECREASING INJECTION TILL 8KRPM?

My question to the experienced guy's here: Is there anything with water injection which effects EGT's directly besides the normal "more advance, richer mixture" things which also are valid on a non-WM injected engine?

I thought about a second stage (for high rpm) of pure water at the TB or direct port inj. but this makes the setup much more complex and i would avoid any kind of unneccesary complexity.

I WOULD FOCUS ON SOLVING THE MISFIRING ISSUE.

COULD BE SPARK PLUG HEAT RANGE/ BAD FUEL ATOMISATION/TOO MUCH FUEL INJECTED/RETARDED TIMING/IGNITION SYSTEM FAULTY OR OVERHEATING COILS/DWELL TIME INCORRECTLY SET

POST SOME PICTURES OF YOUR PLUGS

[rotrex]

Very rich AFRs plus water methanol lead to ignition delay and slow flame propagation speed. It has a similar effect as retarded ignition increasing your EGTs.
Misfires can dramatically increase EGTs as the fuel continues to burn in the manifold.

I have no personal experience with EGTs as I do not run a turbocharger.
140cc a minute sound like very little to me. I am peronsonally closer to 600 ml/min on less boost.
What HP level do you run? Engine capacity or type? Sounds a bit like a Honda B16 or B18 spinning 8000 rpm on a turbo. Sounds like at least 300HP to me. In this case I'd work with 450 to 500ml/min mix. I like Richard's rule of 1 to 1.5cc/min per HP.

Sorry to be of no more help.

[mrx79]

Thanks for your comments. A "misfire" could be the reason. I know my ignition system is not the best for WM right now, i know this, i'am currently working on it this year.
But i don't think this will not change the max. EGT.

Concerning the mixture rate, at a constant flow rate, it's normal that the concentration get's lower with rising rpm.

Engine is as (i guess) mentioned earlier somewhere here in the forum a B16 with around 370hp. I know the flow rate is below usual levels, but i wanted to start thinks slow because i did not had much luck with higher flow rates in the past.

[katherinehayden]

The engine is not capable of producing EGTs which are high enough to harm any thing. EGT may also be used to detect abnormal combustion events, including the detonation and pre-ignition. you can see the article in Dissertation writing service UK

[parmas]

Originally Posted by mrx79

Thanks for your comments. A "misfire" could be the reason. I know my ignition system is not the best for WM right now, i know this, i'am currently working on it this year.

GIVE PRIORITY TO SOLVE THE IGNITION SYSTEM. UNTIL THEN WE MIGHT HELP YOU FURTHER.

But i don't think this will not change the max. EGT.

HOW COME AN ENGINE 8.0 COMPRESSION VS A 10.0 HAS HIGHER EGTS ? TRUST ME GETTING THE IGNITION SYSTEM WORK PROPERLY WILL EFFECT MAX EGT.

Concerning the mixture rate, at a constant flow rate, it's normal that the concentration get's lower with rising rpm.

COULD YOU EXPLAIN IN DETAIL THE ABOVE SENTENCE?

Engine is as (i guess) mentioned earlier somewhere here in the forum a B16 with around 370hp. I know the flow rate is below usual levels, but i wanted to start thinks slow because i did not had much luck with higher flow rates in the past.

B16 YOU MEAN HONDA?

[rotrex]

From:
http://etd.lsu.edu/docs/available/et...Thesis2012.pdf

When ignition timing was fixed it was found that exhaust temperature increased with increasing water content as a result of later combustion and less heat lost to the ambient environment. However, applying an ignition timing scheme to achieve maximum torque resulted in a decrease in exhaust temperature as water content increased. This is because of the heat lost to vaporizing additional water in the fuel. Furthermore, it was suggested that the use of hydrous ethanol may allow the use of higher compression ratio devices that would increase the power output of the engine [Brewster et al, 2007].


Makes sense. Water leads to an effective retardation of combustion due to ignition delay and reduced flame propagation speed. You lose power. So you need to add timing and voila, EGTs drop again.

[parmas]

Thanks for the article rotrex I will try to read it.

I agree with the theory of water injection acting similarly as ignition retard. The same theory applies when you over inject fuel or when weak/cold spark is used.

I would love to make a chart one day with different water or W/M mixtures at various flowrates including basefuel ,ignition timing and egts with pictures of the spark plug burn to understand better the theory.