Thread: Td5 wastegate

Any of the above conditions can result in excessive EGT if the vehicle is working hard, such as pulling a heavy load, running at sustained high speed, subjected to climbing a long grade, etc.

Above taken from Paul's post....what I was warning against.

Just to clarify what I was trying to put simply, yes Paul is correct.

More boost equals higher temperature in the compressed air from the turbo...the more air is compressed, the hotter it gets.
Hotter air gets thinner, or less dense.
This thinner air leads to the rich fuel issue which is the hotter egts.
This is where the bigger intercooler comes in...it cools that now hotter air causing it to become more dense, this results in the more appropriate combustion ratio which means lower combustion temperatures.

So yes, more air means cooler, but more boost without the intercooler does not equal more air.....only less dense air which means less oxygen for combustion.

That's why fitting a bigger more effective intercooler is not only worth it for a performance gain, it's essential for engine longetivety.....

Hope that clears up what I said

Oh and also, whilst the update intercooler might be good on a non chipped car, and it is certainly worthwhile to do, it may not be good enough for a chipped, (or ecu upgrade to be more specific), Increased boost car. You may like to consider an allisport jobbie, $822 shipped including silicone hoses....bout the same for an Alivetuning kit.
But you absolutely need an egt gauge....you will be surprise how quickly the standard td5 can get to high temps, never mind one that has been "tweaked" a bit.

Cheers
Kev

Originally Posted by bigkevg

More boost equals higher temperature in the compressed air from the turbo...the more air is compressed, the hotter it gets. Hotter air gets thinner, or less dense.

I am not sure this argument is logical in this situation. Both sentences are correct but not necessarily linked. Hotter air only gets thinner if the volume of the air is allowed to expand. You can't have the air getting compressed by the turbo and getting less dense at the same time.

My thermodynamics is a little rusty but I suspect that, as the heated compressed air passes throught the I/C, as the temperature drops, so does the pressure. The effective volume probably does too somewhat (relates to velocity of the air). So I think the density might increase slightly but not greatly.

My guess would be the increased egt with increased boost probably comes mainly from the higher inlet gas temperature and the fact that the increased power means the engine is doing more work in a given time, and hence gets hotter.

Cheers

Originally Posted by Mundy

I am not sure this argument is logical in this situation. Both sentences are correct but not necessarily linked. Hotter air only gets thinner if the volume of the air is allowed to expand. You can't have the air getting compressed by the turbo and getting less dense at the same time.

My thermodynamics is a little rusty but I suspect that, as the heated compressed air passes throught the I/C, as the temperature drops, so does the pressure. The effective volume probably does too somewhat (relates to velocity of the air). So I think the density might increase slightly but not greatly.

My guess would be the increased egt with increased boost probably comes mainly from the higher inlet gas temperature and the fact that the increased power means the engine is doing more work in a given time, and hence gets hotter.

Cheers

Actually Mundy you are both correct and incorrect. Yes there is a thermal issue in relation to the air being hotter as well, but there is most definitely an air density issue, and with diesels it is the air density that causes the most problem. There are plenty of articles about how turbos, superchargers and intercoolers work, so I'm not going to post any specific link for one.

Cheers again
Kev

Originally Posted by Disco Muppet

I'm with OffTrack, I was under the impression that by increasing the boost it would run marginally cooler?
With the wastegate mod, isn't it really only an issue low down, i.e it might pick up a bit quicker but it's not got quite the dramatic change that a remap offers?
Either way....looks like a D2a IC is on the cards for me....
Might be a weekend project if I can find some willing helpers
I've been looking at boost/EGT gauge packages, so we'll see what happens.
Also, how obvious is the webbing on the exhaust manifold?
I was giving the engine a quick once over, looking for oil leaks, coolant, etc and I had the acoustic cover off.
Poked around underneath the manifold with a mirror as the stupid turbo heat shield was in the way and I couldn't see it.
Perhaps mine has been removed?
The lady I got it from towed a small trailer for a living, it's a possibility I suppose

Hey DM

The webbing is very obvious, so it may have already been modified...bonus!

The intercooler change is not too bad, remove fan, use sheet of cardboard to lay radiator back against engine...protect fins with cardboard...remove intercooler through gap.....fiddly and very tight fit, but doable.....get some silicone hoses and do those as well while you are at it if the budget allows.

Kev.

Originally Posted by bigkevg

Any of the above conditions can result in excessive EGT if the vehicle is working hard, such as pulling a heavy load, running at sustained high speed, subjected to climbing a long grade, etc.

Above taken from Paul's post....what I was warning against.

Just to clarify what I was trying to put simply, yes Paul is correct.

More boost equals higher temperature in the compressed air from the turbo...the more air is compressed, the hotter it gets.
Hotter air gets thinner, or less dense.
This thinner air leads to the rich fuel issue which is the hotter egts.
This is where the bigger intercooler comes in...it cools that now hotter air causing it to become more dense, this results in the more appropriate combustion ratio which means lower combustion temperatures.

So yes, more air means cooler, but more boost without the intercooler does not equal more air.....only less dense air which means less oxygen for combustion.

That's why fitting a bigger more effective intercooler is not only worth it for a performance gain, it's essential for engine longetivety.....

Hope that clears up what I said

Cheers
Kev

Hi Kev,

It sounds like you are saying that turning up the boost automatically leads to an increase in EGT's?

Using figures from a nanocom recording of my d2 with a Td5Inside remap and stock D2 intercooler, and stock boost setting:

Intake Manifold Temp: 56°C
Absolute Boost : 213 Kpa

From the above you can calculate the air density in the manifold as 2.2553 kg/m3.

What you seem to be arguing above is that the temperature increase resulting from increasing the boost outweighs any advantage from the boost increase. For that to be true the air density in the manifold would have to be equal or lower than the figure I calculated above.

Assuming we raise pressure to 20psi we have two fixed points:

Absolute Boost: 240Kpa
Target Air Density: 2.2553 kg/m3.

The only other thing that can alter the density is temperature, and for the above conditions Air Intake Manifold temp would need to be 98°C. I'm struggling to see how that is actually possible even with very high EGT's.

The following is a nanocom recording of the kind of thing that occurs with my D2:



green (c1/10) is the rpm divided by 10 so it fits on the axis.
Red is absolute manifold pressure
blue is manifold air temp.

From memory this was driving through the Mullum Mullum tunnel which has a deceptively steep climb at the city side exit. It's 80 through the tunnel and 100 after the exit so it's a combination of climbing reasonably hard, then accelerating to 100 and then settling down to cruising at 100ish.

As you can see the intake temperature increases fairly slowly during periods of high boost.

I'll try to have a play in the next few days to record the differences between the stock and 20psi settings. I think it's fairly safe to say I'm not going to see anywhere close to 98°C at the intake manifold.

cheers
Paul

Hi Paul

I am by no means arguing that the increase in boost is not worth it.

To clarify, I am not an expert in this matter, nor have I been trained in this subject. I have simply researched what happens to air when compressed in a turbo, it's effect on combustion in a diesel and resulting outcomes re egt etc etc.

The standard td5 can warp manifolds without any modifications. Manifolds warp because of too much heat.
Change any part of the equation (fuel/boost), and the results will obviously change. Those results will depend on how much change is done.

If you increase fuel by remap, then you need more air....now normal driving around this may be relatively insignificant, but under full throttle and load, this could result in the imbalance of air/fuel giving higher egt.
So we up the boost....theoretically more air, and at lower, normal driving I'm making the assumption that this is ok, but again at full throttle under load, the boost heats the air more resulting in less dense air for the amount of fuel resulting in higher egt...no?

So we add an intercooler to cool the compressed air to make it more dense therefore putting the ratio back to a beneficial point to keep egt temps down.

The standard intercooler is designed to do a certain job, no doubt with some margin. But they found it necessary to increase the size of the update one to cope with minor changes to the output of the update motor.

Again, designed for a standard motor, but with margin for extreme weather ofcourse.

Again, all the D2s can, and do, warp their manifolds, generally with towing or spirited drivers, or good off road fun, leading to the conclusion that they, like all standard car parts are made to just do the job, and no more.

I have also read that heat effect from high egts is an accumulative effect as well and even though a single event may not cause apparent damage to a turbo, the ongoing events of numerous events can lead to turbo failure.....

Yes, I agree that you can do any of these things individually, and with responsible careful driving, you may not have a problem, but logically, you could and if required to push the car a bit, towing, long hills, pushing it a bit, having some fun off road etc, you are asking for trouble. This is where the egt gauge is the best investment you can buy, even for a standard car.....should actually be standard fitment for all diesels IMO.

With all mods to an engine, you change something, then something else has to work harder to meet the extra demand, so all mods need to be considered if you want you engine to stay reliable and efficient, plus perform to the way you want the mods to make it.

So yes, do it, do it.....more boost, remap, I have....does it go better, you betcha, but I don't push it because I haven't fitted my egt gauge yet....and I'm just about to fit an allisport intercooler.....as well as fit the egt, cut out the webbing on the manifold, enlarge the stud holes, and maybe get it ceramic coated if funds allow.

The boosted air from a turbo before intercooler can reach temps way in excess of 190 degrees according to my research. The intercooler brings this back down to, or much closer ambient temp. This depends on how efficient your intercooler is I guess......standard won't have too much in reserve....hence the market for aftermarket larger more efficient intercoolers I guess. Once the capacity of your intercooler is reached, it won't take long for those inlet temps to be much higher....

http://www.allisport.com/index.php?o...id=190&lang=en

Just a link regarding temps......sorry couldn't find other one I was reading regarding more info on temps ....will try again later.

Cheers

Hi Kev,

Yes you will see the outlet temp of the turbo go up. I'd hazard a guess the 190°C outlet temp is at 30psi boost.

Stock outlet temps are going to be closer to 138°C, and 20psi boost will be roughly 158°C.

I'm cheating of course: Stealth 316 - Turbo Outlet Temperature

What really matters is the temperatures at the inlet manifold as this is what the engine consumes.

These are based on 22°C ambient temp.

The stock cooler (assuming around 70% efficiency):
16psi: 56°C
20psi: 63°C

D2a intercooler assuming 25% more efficient than D2 stock:
16psi: 40°C
20psi: 43°C

Aftermarket 95% efficient cooler (guess work)
16psi: 28°C
20psi: 29°C

So if the d2a intercooler is 25% better than the original it's a decent upgrade.

The real question is how much difference the increase in density makes to EGT's. In the grand scheme of things a 7°C increase in inlet temp is fairly minor, but does the increased density lower EGT's sufficiently to offset?

cheers
Paul

I have measured boost temps on some of my turbos. At 24psi I'm around 135c. Even if you drop efficiency down to around 60% and suffer the extra heat gain you will still keep gaining air density and losing egt right up to when you explode your turbo.

Better intercooling is always a good thing. But sometimes impractical to achieve.