[geeyoutoo]

Have a look at this, from the archives, it is a survey that was done some time back and this one was specifically for the CRD.

http://www.patrol4x4.com/forum/zd30-crd-engine-3-litre-82/egt-survey-crd-88474/

You never know what you might find in these places.

We normally recommend the probe to be located closer to the turbo, within 50 to 60mm. Info like this can be found when looking at both DI and CRD archives as they are still basically the same engine and share a lot of components.

 

[geeyoutoo]

I don't believe that the EGT should be measured after the turbo and I have never done it that way because the data you get back is pointless on its own.

Not really the whole story, and this has been written many times, placing the probe close to the turbo flange, 50-60mm, is a simple and very effective method of getting an overall view of what is happening in the engine, the reaction time is very quick so you are getting positive feedback instantly.

In the archives we have a significant database of temperatures in this position that can be used as a reference, so going to all the trouble of fitting it in a manifold and possibly having one cylinder being dominant does not make a lot of sense, sure a correctly positioned probe in a manifold will be more accurate but why go to that trouble when 50mm from the turbo flange works just as well. We use 550C as a maximum for a DI (a little higher for a CRD) and many of us can achieve significantly better with a bit of work, in reality we are only after something to guide us and based on existing data,,,,, we do, simple as. I cruise at 210-240C on flat at 100k at 9psi and rarely see over 450C, this is down from 700C+ when I first fitted an EGT gauge but had no other NADS gear.

Now if I was building an engine or for some reason had to remove the manifold then I may just take the time to fit a probe in a carefully selected position, but for the masses who won't be doing this, 50mm from the Turbo flange is very good option.

 

[geeyoutoo]

geeyoutoo, I don't see how it can be measured correctly due to all the patrols on the road been so different in regards to engine compression, load up, ambient, altitude, fuel, fuel pressure, road conditions, temp of coolant, boost and all that other stuff. The only way is to do before and after to get some sort of true reading. I understand its a swine to fit one at the exhaust manifold but is it not just guess work now. If I said the ZD patrol standard boost is 28 PSI can any one show me a document from Nissan stating in black and white that that level of boost is to high or to low. So how can we guess what it should and shouldn't be. Its difficult one to I know and maybe even nissan have no real level of what EGT is ok apart from what heat the engine can displace.

As said we have collected data over a period of time with the objective of putting together as "safe a guide as possible" for the average punter, remember it's the average punter that we are concerned with here, those of us that have mechanical skills and background can please ourselves what we do, sure all engines are slightly different in various conditions but not that different, run a DI constantly over 550C (CRD's higher) in any conditions and you are closer to a failure than at 500C and you are not leaving much room and inviting a problem.

Even just a few years ago if someone had said we will all run our DI's at 18psi, it would have been almost impossible for the average punter to achieve, through guy's playing around collecting data and writing it up almost anyone can achieve it now without spending thousands, so what we have gained in knowledge has come from the roots of the forum and experimentation, the same as a safe EGT limit, it may not be written up in a glossy magazine but that doesn't detract from the quality of the info across the spectrum (that is the key), remembering it is a safe limit guide, that is really quite easily achieved.

 

[geeyoutoo]

Looking at the ZD30 engine I feel the root course of high EGT on this engine stem from multiple issues and they all need addressing when fitting a Ex Gas temp. What limits this little engine is the amount of EGT it makes and so we could be limiting the power all because were taking a lower reading. Is it not worth a little bit of extra time and doing both? I expect the ZD can run 850C at exhaust manifold with ease and 650C after the turbo for long periods of time. The OEM pistons are built to handle no more then 1200C for very limited period.

But this is changing your original point that post turbo EGT is not effective and that manifold readings are the only effective measure.

I go back to the point this was put together for the average punter, all measurements are subjective but when you have a data base that put's readings into a perspective and the EGT survey's go a fair way to doing that I feel, why should the average punter go to all that trouble removing manifolds to get a temp that he can already cross reference with other users in the same position.

I don't think we are robbing our engines of HP by aiming low, it's more important in how you aim low, you can pump plenty of fuel in as long as you are pumping in a corresponding amount of air, I have no problems with how much grunt mines got, it's way over std and as said my temps are hundreds below what I had and what I had was a significant contributing factor in the demise of my first engine, simple as.

Surely it makes sense to aim low than to aim marginal and run the risk of doing it all again?

I agree with you dbsep, the location and readings are largely irrelvent. BUT it will show a trend in its action. If you usually see 300*C cruising and then see 700*C, you know the motor is underload, the actual number could and does vary significantly to each vehicle, but the temperature change will always mean the same thing.

Isn't this exactly what I've been saying (just a little differently) that something to trend against is what the average punter needs, not having to remove manifolds (bloody helll the heat shield is hard enough).

 

[geeyoutoo]

But I see dbsep's point and reflect on what I was saying the otherday. The advice being given from this site is a reflection on individual vehicles, setups, circumstances and personal preferences. Just because I see 600*C doesn't mean my car has something wrong with it because someone else sees 400*C. When calibrated or calculated from EGT position, any precombustion treatment, gear, load, etc. You'll probably find they are the same or could be hugely different. So what is gained by saying EGT should be either 400*C, 600*C or anything in between at a given rev or speed?

So even when we survey and get a variation of 200*C, vehicles anywhere on that scale could either be running ok or sht, we just don't know because the comparison is not the same.

This discussion is going nowhere so after this I'll stop, you believe what you want and I'll believe what I do, our members can make up their own mind based on our experiences and data, that is the choices a good forum gives, I have put forward the EGT surveys as a reference point for our "average punter", and I see no "evidence" (structured or anecdotal) to rule it out as a guide, I can live with that no worries.

If you read the survey (and I have read every single one in great detail) you will notice we had a lot of questions re mods etc to give the guy's something to compare too for their vehicle.