90 & 91 Prado w/2LT engines

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now this i find interesting...
pressure i agree
tempatures i am not sure i agree. here is why i am doubtful of this statement.
you take a NA engine with a 1400F max egt, add a turbo and the exhaust temps drop (if you don't mess with the fuel setting) dramaticly
ifyou have a 2LTE and increase the boost to 14PSI you have a hard time breaking 1000F where as before with 7-8 lbs of boost you will be over 1400F easily.
the idea of a turbo adding heat is a misconception...

cheers
 
In a thermic system like an engine you cannot add pressure without temperature and vice versa. There are many ways to prove it through physics.
I will try to keep it simple because I forgot more thermodynamics than I care to remember :doh:
A typical car/truck engine would have an efficency of 30%-ish, with said efficiency being something like (fuel-heat)/fuel or pressure/fuel. Fuel is 1, heat is 0.7 pressure is 0.3
Now if you add a conservative 30% more fuel to go along with 7psi of boost but keep the heat equal you have 1.3 0.7 and 0.6. Your efficiency just jumped to a superb 46% and you have 150hp instead of 75. I wish a turbo would be such a miraculous device but it is not. Of course you will argue that you have to integer the thing along the cycle because these are not constants, and blah blah blah but the basic picture is just like I wrote. As long as the efficiency is below 100% (which means a part of the energy is used as mechanical work, the other part is used as heat), you add some fuel you add some heat it's as simple as that.
You are talking about the lower EGT, I will ask about the EGE "exhaust gas energy". 1000F at 14psi in N/A is not the same as 1000F at 30psi pre turbo.
I will look in my thermodynamic notes again if I can find them and will provide for a math-proof demonstration if required. I'd rather not but hey it might be a good exercice :D
 
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crushers said:
now this i find interesting...
pressure i agree
tempatures i am not sure i agree. here is why i am doubtful of this statement.
you take a NA engine with a 1400F max egt, add a turbo and the exhaust temps drop (if you don't mess with the fuel setting) dramaticly
Click to expand...
I realized I didn't really answer your question, this part is taken care of above,

ifyou have a 2LTE and increase the boost to 14PSI you have a hard time breaking 1000F where as before with 7-8 lbs of boost you will be over 1400F easily.
Click to expand...
Well if that's pre-turbo I would refer you to the EGE theory above, if that's post, you need to realize that in order to priduce boost, the turbo takes its energy from the exhaust so in addition to the EGE you will need to take into account a (much) higher temps drop across the turbo.
the idea of a turbo adding heat is a misconception...

cheers
Click to expand...

The turbo and fresh air alone are not adding a lot of heat, the added fueling does. The energy in the fuel is partly used for power, partly wasted in heat. For the same engine design the ratio (efficiency) will not be varying that much in the same conditions so "x" times more power =~ "x" times more fuel =~ "x" times more heat.
I hope this makes sense ?
Using the same amount of power at lower revs in a turbo than you would in a natural will generally bring a better efficiency because there will be lower losses thanks to the gases having more time to travel, and fuel having more time to burn completely, so you would have less heat, but usually when you have a turbo you're not using it to improve the efficiency but to increase the power so...
 
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denis said:
you need to realize that in order to priduce boost, the turbo takes its energy from the exhaust so in addition to the EGE you will need to take into account a (much) higher temps drop across the turbo.

...
Click to expand...

if the probe is in the same spot before and after the boost increase. why is the EGTs reading cooler... please help me get this through my thick head.
EGE should be the same, no? the air charge into the throttle body is actually hotter at higher boost pressures but the exiting gasses are cooler...
hummm...
 
denis thats too deep man.....

Simple thing is that when turbo'd a NA engine we see it get cooler. Unless we add more fuel.

To add boost we are simply just re-routing more thru the turbine, rather than wastegate. Yah as pressure increases so will the heat. But this isn't the combustion temps. ??

The combustion temps are based on the extra density of oxygen to efficently burn the fuel.

All I know is more air is cooler, less air is hotter. I can even see that with relation to lugging versus reving higher.

Anyhow I'm not disagreeing, but rather just trying to see what your saying....
 
The main point was Waynes doubt about heat in natural vs. turbo.
Now with a turbo at a given fuel quantity you can have too little or too much boost.
If the pre-turbine EGT are dramatically reduced when boost is added then the boost was probably too low too start with. But then if you keep adding boost there will be a point of diminishing returns, wasting energy compressing unnecessary air twice.
Again a turbo engine is not more air with the same fuel but more air with more fuel.
As for lugging vs reving you are right, the engine will swallow more air and for the same quantity the fuel amount will be injected sooner (in average) in the stroke making for a more complete burn. That does not necessarily mean the peak temps will be lower but the EGT definately will.
 
crushers said:
if the probe is in the same spot before and after the boost increase. why is the EGTs reading cooler... please help me get this through my thick head.
EGE should be the same, no? the air charge into the throttle body is actually hotter at higher boost pressures but the exiting gasses are cooler...
hummm...
Click to expand...

Read I never said in the scenario you are talking about the combustion temps and efficency were worse with the higher boost setting. The optimum boost level you will have to find yourself with more mesurments than just EGT. There was probably not enough air to start with indeed, but the EGT alone doesn't tell you everything that happens in the engine.
BTW a proper L engine shouldn't have such thing as a throttle body :doh:
 
denis said:
BTW a proper L engine shouldn't have such thing as a throttle body :doh:
Click to expand...

intake manifold ... my bad... better?

so how do you measure the actual temps inside the chanber then?
if the temps exiting the cylinder are cooler one would ASSUME the temps inside the cylinder would be cooler...
 
(I think the EGR removal on 2LTEs could benefit from throttle plates removal.)

combustion chamber temps : I cannot measure them right now but one day I will stick some probes in the glow plug holes :D
A fundraiser would make this happen a lot faster.
Some more L series diesel research will be conducted on my new-to-me 2WD LN85 :grinpimp:
 
i might be a bit bull headed but when actual test reports are posted i tend to beleive much faster than book knowledge. too many times have i found that book knowledge and real life experience do nto coincide with each other...

post up your finding, i am very interested in seeing what it is...
cheers
 
my brain hurts reading this thread.......

when I get at home all comfy on the couch I will have to try and read Denis posts above... with out kids crying and making noise... :) I need to concnetrate to read that :)

Happy holidays guys!!!!
 
Hey talking about swapping in a cheap 22r gasser. That's what I've got in my RJ77 (same body and chasis as the 78). It does fine on the rougher slower stuff but does not really have enough power for faster highways ie. crusiing at 120km. I would try to find something with a bit more omph.

Marlow
 
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