driving by Pyrometer temperatures

[Bulletproof]

I am horrified by some of the posts I have read about the temperatures some are driving with on ordinary trucks. By that I mean ones not running ceramic stuff like racing cars etc. Temperatures in excess of 700 degrees celsius.

About 5 years ago I fitted the supercharger to the 5l in my hilux and was advised to fit a pyrometer as well. I bought the top of the range VDO oceanic that all the ships use with a range of 0-900 celsius.

I have alot of friends in the shipping and trucking industry so picked their brains on acceptable temperatures. They advised me that the optinum temperature for a diesel was in the lower 400s. On the boats this is easy to maintain as the sea only changes gradually. They would never let allow a reading above higher 400s.

In a motor vehicle things are a bit different because nothing is flat, we are either going up a hill or coming down and energy to do this is poles apart ,resulting in pyrometer readings hundreds of Celsius's apart.
This problem is getting worse as a lot of the hills that used to be windy are now straight to the top. With a Turbo or supercharger it is easy to keep the foot down and cruise up without any thought to what is happening in the motor.

I know from personal experience that the pyrometer very quickly goes from 450 to 600 and the 700 celsius.
So what is an acceptable temperature?
At 700 degrees celsius iron glows red hot, at 750 tips start to burn on turbo fins and as you approach 800 pistons can distort preceding a meltdown.
People I have talked to, say you should never maintain a temperature of over 550 without expecting some form of damage.
IN overtaking I allow the hilux to go to 650 but this only for a few seconds. I have now done 45000ks since and to date dont seem to have any damage. Oil still clear after 2000ks.
In the trucking industry I have been told the main problem is that truckies dont change down quickly enough because with twin turbos seem to have power to burn resulting in damage to their trucks.
I have found this the only way to keep the pyrometer temperature down to an acceplable level even though I still have the power to accelerate on a hill. The problem is you can go up 700c and within a matter of minutes down to 100 which creates a lot of expansion and contraction around the exhaust valves and people wonder why the head cracks.

What I am saying may be wrong, and would like other peoples thoughts and experiences.

Richard

[NJV6]

As some insight to this - can you discribe what temps are at say steady 100km/h flat road and 50km in town etc

Modern turbo diesel's such as the numbers the Koreans are pushing must be creating some high temps to get to power from small diesels? Or is it just better combusting.

To get around this 650 -100 as you say rapid expanding and cooling? In normal driving this will be a fact of life will it not?

[tweake]

firstly it depends on if your reading pre turbo or after turbo readings.

imho it doesn't matter how hot you go provided you don't go to hot.
hopefully you motor will be tuned to be a little short of max temp to allow for poor fuel, faults, block aircleaner etc.

it also depends on what the motor is meant to be doing eg a boat cruising at max economy or a small engine going hard out for max performance.

heard a bit on the running at max temp up hill and not letting it cool to fast to avoid head cracking. but having said that most small engines are built light weight for performance/economy/emmisions so its no wonder so many crack the heads.

[Bulletproof]

A pyrometer should be fitted after the turbo where the temperature is very roughly 100c less than the other side and these are the figures I have quoted. In my case because I have a supercharger and extractors and have it fitted in the collector of the 4 pipes.
There is no set reading at 100k or any other speed because what appears to flat could be 2 degrees up or down and there could be a tail or head wind, once again making the reading 100s degrees apart. unless you have a pyrometer you would never no what is happening.
Even when I go up to 650 Celsius{ which is equal to 550 on a truck fitted with a turbo} on a hill my water temperature doesn't move up at all. So if your temperature gauge moves up on a hill you are probably running very high pyrometer readings or otherwise have radiator problems

Richard

firstly it depends on if your reading pre turbo or after turbo readings.

imho it doesn't matter how hot you go provided you don't go to hot.
hopefully you motor will be tuned to be a little short of max temp to allow for poor fuel, faults, block aircleaner etc.

it also depends on what the motor is meant to be doing eg a boat cruising at max economy or a small engine going hard out for max performance.

heard a bit on the running at max temp up hill and not letting it cool to fast to avoid head cracking. but having said that most small engines are built light weight for performance/economy/emmisions so its no wonder so many crack the heads.

[KiwiBacon]

A pyrometer should be fitted after the turbo where the temperature is very roughly 100c less than the other side and these are the figures I have quoted.

This is very wrong.
A pyro after the turbo is a guessing game. If you guess wrong, you can toast your engine, turbo etc.

If you do the maths on the temp drop across a 65% efficient turbine at a few operating points you get some very interesting results.
Results which show just how scary that 100 deg C fudge factor is.

For example, my engine going up the Otira viaduct.
20psi boost, 20psi backpressure.
Pre turbo EGT's of 750 deg C.
Calculated post turbo temp is 565 deg C.
That's a temp drop of 185 deg C. If I guess 100 C, I'd have cooked it long ago.

My engine under hard acceleration.
20psi boost, 40psi backpressure.
Preturbo EGT's of 700 deg C.
Calculated post turbo EGT's of 411 deg C.
That's a temp drop of 289 deg C. If I doubled that fudge factor to 200C, then I'd still have a cooked engine and turbo.

My engine at 100km/h cruise.
9psi boost, 13psi backpressure
Preturbo EGT's of 450 deg C.
Calculated post turbo EGT's of 353 deg C.


IHI have a max turbo intake temp of 750 deg C, garrett I suspect is higher as they're pushing their new turbos into the 1050 deg C intake range to work on newer petrol engines without as much full throttle enrichment.

[Bulletproof]

So are you saying a pyrometer should be fitted pre turbo to take away the quess work ?
Because every person I know has been advised to fit them after the turbo and have done just that.

What you are saying makes more sense to me because you know exactly what is going on. I know with the XR6 falcon they are losing about 300c through the turbo with a temperature of 900 post turbo
In my case this doen"t apply because of not having a turbo, I am getting an accurate reading and try to maintain about 450 celsius at all times.
The only way a person learns is by talking about these things and it is good to get feed back.
Richard

[KiwiBacon]

So are you saying a pyrometer should be fitted pre turbo to take away the quess work ?
Because every person I know has been advised to fit them after the turbo and have done just that.

What you are saying makes more sense to me because you know exactly what is going on. I know with the XR6 falcon they are losing about 300c through the turbo with a temperature of 900 post turbo
In my case this doen"t apply because of not having a turbo, I am getting an accurate reading and try to maintain about 450 celsius at all times.
The only way a person learns is by talking about these things and it is good to get feed back.
Richard

Yes pre-turbo is the only way to know. But even then you've got to account for some cylinders receiving less air than others and the probe taking the average reading. Also the lag in the time it takes for the manifold and pyro to heat up results in the temps read under acceleration being lower than they actually are.

450 deg C in the header is way too low IMO, you're wasting power pumping unnecessary amounts of air with the supercharger, 750 is the danger point, put whatever safety factor you like on that.

[tweake]

a few guys have posted dual pyro readings on some forums. interestingly the new variable turbo's can have 250 degree difference and that can vary depending on turbo operation.

most put ot after turbo because its easy and safer if a sensor breaks.

[Bulletproof]

450 deg C in the header is way too low IMO, you're wasting power pumping unnecessary amounts of air with the supercharger, 750 is the danger point, put whatever safety factor you like on that.[/quote]


I run naturally aspirated until I get to 550-575 and then turn the supercharger on to reduce it to 430-450c which boat engineers have told me is the right temperature for a diesel. The 4 pipes are aboul 700 long so at he header where the pyrometer is ,the temerature will be quite abit less than at the head.
What would you recommend? I always err on the side of safety.
Richard

[KiwiBacon]

450 deg C in the header is way too low IMO, you're wasting power pumping unnecessary amounts of air with the supercharger, 750 is the danger point, put whatever safety factor you like on that.

I run naturally aspirated until I get to 550-575 and then turn the supercharger on to reduce it to 430-450c which boat engineers have told me is the right temperature for a diesel. The 4 pipes are aboul 700 long so at he header where the pyrometer is ,the temerature will be quite abit less than at the head.
What would you recommend? I always err on the side of safety.
Richard

I run my turbo diesel at up to 750C, been doing it for a while now with no problems. The occasional accidental excursion past too. That's got the probe where the cast manifolds meet. I don't sustain those temps for long as even passing in 5th gear the speed builds pretty quickly.
At 100km/h cruise I've got 400-450C preturbo.
A reputable source tells me his Isuzu factory manual specifies 750C max pre-turbo, that's in a truck engine which lasts half a million km between rebuilds.
I have a scania turbo-compound schematic which has the exhaust into the first turbo labelled at 700 deg C. Again that's a truck engine.

Are those marine guys talking post turbo?
I'd happily run upwards of 650C if it was my engine, but it's not my engine so stick to what you're comfortable with.

[Bulletproof]

I'd say we are talking about very similar temperatures.
On a hill like the spooners range or overtaking I go close to 700 with charger on but not for very long and then ease back to my 100 cruising speed around 450 without the charger and turn the charger on for overtaking .
Heading through Arthers pass towards porters pass I leave the charger on to keep within my 450 range otherwise naturally aspirated I would be over 700 Celsius at 100ks especially with 35s on .
Richard

[KiwiBacon]

I'd say we are talking about very similar temperatures.
On a hill like the spooners range or overtaking I go close to 700 with charger on but not for very long and then ease back to my 100 cruising speed around 450 without the charger and turn the charger on for overtaking .
Heading through Arthers pass towards porters pass I leave the charger on to keep within my 450 range otherwise naturally aspirated I would be over 700 Celsius at 100ks especially with 35s on .
Richard

Nothing wrong with those numbers.

[timotheus]

Some interesting stuff guys.

Ive looked at fitting a pyro to a 2LT Im looking after (owner in Oz) but the prices are a bit steep for just a hack Im looking after.

You can buy digital thermometers from Jaycar for piss all, they are rated to 1000"C and are claimed accurate to 2"C.

Question, what are your thoughts on clamping the probe to the manifold?
I know it will never be as accurate as being in the exhaust stream and wont show the fast variance you can expect, but shouldn't be that far off and should show if im holding it too high too long.

Tim

[Bulletproof]

My engine under hard acceleration.
20psi boost, 40psi backpressure.
Preturbo EGT's of 700 deg C.
Calculated post turbo EGT's of 411 deg C.

Beside the fact that a manually controlled supercharger is far superior over a turbo for 4 wheel driving giving power when and where you want and need it, is the that it doesn't have the back pressure associated with turbos.
I run extractors as well so I blow fresh cold air into the motor through the intercooler and then get sucked it out the other side .
This gets the heat away from the head and valves as quickly as possible leaving the motor to suck in a lung full of fresh cold air again.
Because I have a dual air system and most of the time are running naturally aspirated, I think it is more important to have a pyrometer at this time rather than when the supercharger is turned on which lowers the exhaust temperature by 150Celsius.
Naturally aspirated the temperature goes very quickly goes to 700 and I am not prepared to see what it would reach, so it would be very easy to cook the motor.
Richard

[KiwiBacon]

Beside the fact that a manually controlled supercharger is far superior over a turbo for 4 wheel driving giving power when and where you want and need it, is the that it doesn't have the back pressure associated with turbos.

The power your engine loses pumping against the turbo backpressure is less than the powered needed to turn a supercharger to provide the same boost.
That 40psi I mentioned above is a worst case spike and only happens for about 2 seconds under hard acceleration with a cold turbo and exhaust manifold.
As the exhaust gas warms, the backpressure decreases, at 650 deg C I get the same backpressure as boost. Which means the engine is losing almost no power driving the turbo, it comes entirely from the heat in the exhaust.

Low end boost is a problem with the wrong turbo, but variable vane turbos have sunk that problem. Even without a variable vane turbo I've got 10psi boost before 1400rpm and 20psi before 1800.

[Bulletproof]

The main point I was saying was that with extractors you are getting rid of heat real quick which is better for the motor, where as a turbo has to retain the heat to spin the turbo and produce boost.

And I think naturally aspirated need pyrometers more than boosted trucks

The subject of supercharger verses turbo for power is a separate subject by itself. In Nelson where we have very steep fire breaks that go up 100s of feet the trucks with turbos have to get a run up and hope they make it to the top. If they shut off to idle to regain traction can not get back into their turbo range. With my supercharger I am running 4lbs at 750rpm and can shut off and then accelerate away again more like a petrol V8 ith an auto.
But thats another suject.
Richard

[KiwiBacon]

The main point I was saying was that with extractors you are getting rid of heat real quick which is better for the motor, where as a turbo has to retain the heat to spin the turbo and produce boost.

And I think naturally aspirated need pyrometers more than boosted trucks

The subject of supercharger verses turbo for power is a separate subject by itself. In Nelson where we have very steep fire breaks that go up 100s of feet the trucks with turbos have to get a run up and hope they make it to the top. If they shut off to idle to regain traction can not get back into their turbo range. With my supercharger I am running 4lbs at 750rpm and can shut off and then accelerate away again more like a petrol V8 ith an auto.
But thats another suject.
Richard

The heat of a turbo is only a problem to engines with inherently weak heads (toyotas ) and mostly older indirect injection engines there.
Many people (incl aftermarket turbo companies) spec bigger turbos than necessary so they can brag about the number of kilowatts they dropped out on the dyno. As you and I both know low end boost is far more use.
The turbo I have on my rangie is roughly 3 steps smaller than most people fit, but the backpressure and EGT numbers I have show it's still far from choking and can support still more power than I currently have.

I fitted a really small one for an experiment, but the turbine was an old design which wasn't very efficient.
Low end boost was improved slightly, but at full rpm and full boost the exhaust backpressure spiked to 60psi.

[Bulletproof]

The turbo I have on my rangie is roughly 3 steps smaller than most people fit, but the backpressure and EGT numbers I have show it's still far from choking and can support still more power than I currently have.

I know this is a completely unrelated Subject.
You must have plenty of power in the rangie with 20lbs boost. I have a few friends with rangie's and the big problem seems to be diffs and axles .
What kind of running gear have you got to stand up to that power?

Richard

















[/quote]

[KiwiBacon]

I know this is a completely unrelated Subject.
You must have plenty of power in the rangie with 20lbs boost. I have a few friends with rangie's and the big problem seems to be diffs and axles .
What kind of running gear have you got to stand up to that power?

Richard

I've recently switched to later 24spline diffs from a discovery. But interestingly I didn't break any of the old 10 spline stuff, even lighting up tyres on tarmac.
I put this down to driving a bit smoother and not running big tyres.
Currently got about 520Nm on tap.

[Bulletproof]

I've recently switched to later 24spline diffs from a discovery. But interestingly I didn't break any of the old 10 spline stuff, even lighting up tyres on tarmac.
I put this down to driving a bit smoother and not running big tyres.
Currently got about 520Nm on tap.[/quote]


Thanks .
I have heard that ARB are turning out axles as well as lockers that are stronger, but I dont know whether this true or not.
Richard

[KiwiBacon]

Thanks .
I have heard that ARB are turning out axles as well as lockers that are stronger, but I dont know whether this true or not.
Richard

The main reason I went to the disco 24 spline is that's what the aftermarket support is for. I'll put some arb air lockers in at some stage, then I can simply bolt in stronger drive axles if I start breaking stuff. Like the bigger toyotas, my axles are full floating type so changing driveshafts (in the rear at least) is really easy.