Why 550C for TD42T.

[heathgu]

I have talk to a lot of deisel specialists and they all say 550c.

Why is 550 the be all end all i push mine heaps hotter occasionally.

Is it a cooling thing or what does some else happen? Other then a melt down after serious long periods of hot running EGT?

Cheers Heath

[bogged]

I have talk to a lot of deisel specialists and they all say 550c.

Why is 550 the be all end all i push mine heaps hotter occasionally.

Is it a cooling thing or what does some else happen? Other then a melt down after serious long periods of hot running EGT?

550 is probably considered a safe figure. EG if they told you 650 and it died, you could send em the bill..

If you run too hot for too long, your engine will shit itself. causing your wallet to become lighter by many dollars.

It also depends on where you actually have the temp pickup fitted, it can make a ~100 degree difference.

[spannercrab]

Realistically it's the combustion temperature everyone is concerned about - post turbo is not the best place to have the pickup as the turbocharger itself dissapates an indeterminate amount of heat and converts it into energy which is used to spin the compressor wheel.

Pre-turbo is the cheese, even better pre-turbo one per cylinder - but this is fairly impracticle given the $3-400 price tag of EGT gauges. The post turbo solution is a happy medium, although it's harder to judge what is "correct" as it's only a representative figure based on the actual EGT and the heat dissapated by the turbocharger.

Plenty of people exceed this generally accepted "Safe" figure and don't do any damage, there are others who do. As Banks Power so eloquantly put it:

You’re usually gambling against a stacked deck and it’s only a matter of time until you lose. The higher the EGT, the shorter that time will be.

EGT correlates directly to fuel quantity and intake air temperature, by reducing either (intercooling, water spray, fuel load reduction), you can reduce the EGT's.

The bad things that happen usually involve cylinder walls, piston rings, pistons, valves and turbine wheel (melting and pitting of each).

EGT's apply also on NA engines - the figures are a lot higher than 550 (around 700degC maximum) as there is no pesky turbo to get in the way and take the heat out.

Unlike a petrol engine, leaning out the mix does not increase EGT's and will actually cool the engine - too much fuel or not enough air results in post-combustion burning, which leads to burnt exhaust valves and other melted bits ... a diesel belching black smoke is a sure sign of an overfuelling problem.[/b][/quote]

[speed=t/d]

Firstly, I have no experience in this at all, I'm no mechanic or diesel pump expert, so I state this for further input from someone on this site who might be able to shed further light on what I have heard.

Spoke to a fella today about this same issue. He reccons that dyno's are a waste of time as the EGT should be measured when the engine is under load conditions on road. He stated that many diesel pump/service places will tune the vehicle under 'on road'conditions to 550 under load.

Anyway, the only way to learn is to ask...what's the go...thanks guys.

[spannercrab]

I wouldn't go so far as to say dyno EGT setting is "worthless" but it is certainly expensive compared to road testing. Most diesel shops do not have chassis dyno's at their disposal.

There is no reason that either wouldn't work effectively, however under "real" road conditions the engine RPM's are more realistic based on speed and load. However having said this, few diesel shops would be in range of a suitable road (such as one of the range ascents) in order to set this under true "severe road conditions" either.

I would suggest that a reputable diesel pump servicing shop (as opposed to one that just "guesses" by winding up the fuel screw until desired qualitiatve results are achieved) would put the pump on the bench and wind the fuel out to a pre-determined, precisely measured maximum.

I would also suggest that a diesel pump servicing establishment with a pump testing bench would not just "wind up the screw" indeterminantly without putting the pump on the bench to test it either instead of, or as well as the "real road test".

I had my pump tuned in this manner and have found that 550 on the longest climb, on the hottest day, with a load is the absolute EGT maximum that I get out of it.

Unless you are racing the truck or demand absolute peak performance, taking with it the obvious risks that come from "overdoing it" - that a sensible, pre-set, measured fuel dose, matched to the turbocharger / engine / intercooler etc. combination is the better way to go.

[GQ TROL]

Heath,
The temp of 550 is really only accepted best practise. As the EGT increases, the likelihood of failure also increases, so 550 is an acceptable compromise between performance and engine life. That figure could just as easily be 450 or 650.

If you’re exceeding the recommended EGT, the critical part is for how long. Occasional bursts at 650 and beyond is hardly going to reduce engine life drastically.

Also, if you're in the middle of a competition stage and see the EGT gauge sneeking past 550....are you really going to back off the throttle?

[speed=t/d]

Thanks Spanner, that explination has filled in the gaps for me. Just one further question, is it necessary for a EGT guage to be installed when having the pump 'tunned' up or is it a safe bet that once its set for 550 degree that's as far as it will go?

[bogged]

is it necessary for a EGT guage to be installed when having the pump 'tunned' up or is it a safe bet that once its set for 550 degree that's as far as it will go?

Its never a safe bet.

Way too many variables in this, it will always go above 550 even if its tuned to that temp. that is where best power is at, nothing stopping you driving up that long hill for another 10 mins in the rev zone, which will go up past 600 easily
Mine is set for 550, and on way to murray sunset, it hit that easily on the hills with the trailer full on the back, same as the hill out of Dargo heading north.

[busman]

I have a DTS turbo kit on mine and i want to fit boost and egt gauges. The exhaust has a bung it in just after turbo is it ok to put egt there and if so is 550c ok? or should i put it before turbo? For the boost gauge there is a bung in the crossover pipe just before the inlet manifold or should it be connected at the turbo? The boost cuurently reads just under 10psi max plumbed into the crossover pipe.

Thanks for any info.

[spannercrab]

G'day busman,
I haven't sighted a DTS kit, but that is correct, the 550degC measurement is taken after the turbocharger, as close to the turbine outlet as possible. Although technically fitting the probe into turbine inlet a more accurate measurement in order to determine engine health, most people in Oz seem to talk post-turbo figures.

It makes little difference where you take the boost readings from if you are running the system sans-intercooler, but typically the specification is taken as compressor outlet pressure (i.e. as close to the compressor discharge as possible) - if you are running an intercooler, then the specification is pre-intercooler, so the boost measured from the compressor discharge end.

When a kit supplier specifies "12 psi with intercooler" this is usually making allowances for pressure drop across the intercooler core, so they intend to have 10psi ending up in the manifold. it's up to you if you want to run 10, 12 or 20psi at the intake manifold - and so affects where you will put the gauge.

speed=t/d,
If your pump is tuned "by the gauge", and not "on the stand" then there is nothing to stop it going over 550 depending on conditions on the day it was tuned, fuel amounts may vary (cold weather, insufficient load etc could increase the amount the fuel screw is wound up) ... on the stand, with a measured fuel dose, it's far less likely that you will go over the 550, assuming the calculations are done correctly. Although the more information you have about your engine the better, so I would never recommend *against* an EGT gauge.

[speed=t/d]

Thanks Spannercrab and Bogged, very interesting stuff. I've intended to have my 03' TD6 'tunned' for some time now. I've done the first bit myself with a 3" DTS turbo exhaust kit. I spoke with a mob in Sydney and another in Brisbance re 'tunning' for increase in power/engine effeciency. One says $400 odd bucks and we'll tune it on the dyno and give you good gains in both. The other says, bring it in and we'll take it for a drive (under load) see how it performs then we'll decide what we'll do. (dyno not necessary waste of $180-at this stage). The thing that concerns me is that the mob that want's to tune it on the dyno never mentioned anything about EGT's or possibility of over compromising EGT's in on road conditions. (as bogged mentioned on extended hills etc). From what's been said there seems to be a 'risk factor' associated with these sort of 'tune ups' and a EGT guage would be a good investment if set up correctly to prevent engine damage. Am I reading too much into it or am I paranoid???

[blackmav]

I have a DTS turbo kit on mine and i want to fit boost and egt gauges. The exhaust has a bung it in just after turbo is it ok to put egt there and if so is 550c ok? or should i put it before turbo? For the boost gauge there is a bung in the crossover pipe just before the inlet manifold or should it be connected at the turbo? The boost cuurently reads just under 10psi max plumbed into the crossover pipe.

Thanks for any info.

Yep.

[Hoonz]

Thanks Spannercrab and Bogged, very interesting stuff. I've intended to have my 03' TD6 'tunned' for some time now. I've done the first bit myself with a 3" DTS turbo exhaust kit. I spoke with a mob in Sydney and another in Brisbance re 'tunning' for increase in power/engine effeciency. One says $400 odd bucks and we'll tune it on the dyno and give you good gains in both. The other says, bring it in and we'll take it for a drive (under load) see how it performs then we'll decide what we'll do. (dyno not necessary waste of $180-at this stage). The thing that concerns me is that the mob that want's to tune it on the dyno never mentioned anything about EGT's or possibility of over compromising EGT's in on road conditions. (as bogged mentioned on extended hills etc). From what's been said there seems to be a 'risk factor' associated with these sort of 'tune ups' and a EGT guage would be a good investment if set up correctly to prevent engine damage. Am I reading too much into it or am I paranoid???

if you can get it to QDAD in bris they'll do it properly

[spannercrab]

Hi speed,

Long answer:

Out of the two options - the dyno sounds like the better of the two.

I would make the perhaps rash assumption that anyone prepared to charge $400 for significant dyno time would measure critical factors like engine temperature and EGT - so they may have just taken it as a given.

Much like most dyno's are equipped with blowers to provide airflow through the radiator core under load - you don't need to ask, they just do it. Although it's *always* better to ask!

If you have a TD6 already, you may not get any "significant" power or torque increases without upgrading the turbocharger and/or exhaust system as the OEM's on both are renowned to be rather restrictive. A restrictive exhaust (and conversely restrictive turbocharger) can result in increases in EGT anyway, as it restricts airlow, resulting a richer fuel mix, resulting in melted stuff (in the extreme instance).

I would suggest your money would be better spent at a minimum on a mandrel bent exhaust system (3" preferably if you were running the factory t/c : 2.5" possible if you were to upgrade the turbo also) *then* think about dyno / pump tuning in order to maximize performance.


Short answer:

Off-bench tuning = EGT Gauge = Good Idea