Stone said:Oh and Nick...I am back to work now.
Thats awesome Stone.
Does that mean your feeling better?
How is your back? Still bugging you?
Is it perminant damage?
And on the less important side, are you keeping the cruiser now?
Cheers,
Nick
Thermocouple..Pre or Post? (1 Viewer)
- Thread starter Towpack
- Start date
This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.
Thats awesome Stone.
Does that mean your feeling better?
How is your back? Still bugging you?
Is it perminant damage?
And on the less important side, are you keeping the cruiser now?
Cheers,
Nick
denis
(O) toyota nut (O)
if only one has to be used : pre- because I'm interested in what's happening in the combustion chamber. Worry n°1 = head, worry n°2 = pistons. The turbine will be much harder to harm IMO.
Some days I'm thinking about putting one probe right in each cylinder, luckily I have not yet found a convenient way to do it
Some days I'm thinking about putting one probe right in each cylinder, luckily I have not yet found a convenient way to do it
I'm not saying post turbo is the way to go....
But....
On the advice of 2 certified heavy duty diesel mechanics, who recommended to go post turbo.
There reasons were, that the pre turbo EGT would be less accurate to the inner turbo temperature than a (close to turbo) post EGT location of the thermocouple.
They also said that a lot of factory installed thermocouple's were installed post turbo on heavy duty diesel engines.
They mentioned also that there is a possibility of the thermocouple melting off and dropping into there turbo.
So hence my decision to go post.
But whatever works for you....
GB
But....
On the advice of 2 certified heavy duty diesel mechanics, who recommended to go post turbo.
There reasons were, that the pre turbo EGT would be less accurate to the inner turbo temperature than a (close to turbo) post EGT location of the thermocouple.
They also said that a lot of factory installed thermocouple's were installed post turbo on heavy duty diesel engines.
They mentioned also that there is a possibility of the thermocouple melting off and dropping into there turbo.
So hence my decision to go post.
But whatever works for you....
GB
Gold Boy said:
GB:
When I spoke with the guys at Piers Diesel Research about the possibility of this happening to the probe of my ISSPRO thermocouple, they responded by saying that they have never ever seen that happen in all the years of installations that they have done. This is keeping in mind that they mostly tweak Cummins and Powerstroke turbo diesels, some of which put out a thousand foot pounds of torque and around 800 hp at the rear wheels...way more fueled up and boosted than any Toyota diesels will ever be.
Denis:
Combustion chamber temps are also what I'm most concerned with, not the turbo itself. I've thought about this, and prior to shutdown, my EGT's are nowhere near red-hot temperatures. In fact, as I'm slowing down to park, my EGT's have probably been sitting between 400-600*F for a couple of minutes already. Not like my EGT's are 1250*F and then the engine is shut down immediately...so I figure my turbo most likely has already had adequate time to cool down.
Nick:
Back's better, but will still have to sell the truck at this point. Thanks.
denis said:OK Greg sorry for theI guess that's how I like to pick on words and split hairs. The flame front is a spark ignition (SI) term. You have a pretty much homogenous mixture that gets ingnited at one time, one place by the spark, and the combustion propagates from there. In a diesel, long story short the fuel is being injected in a spray of tiny droplets, which spontaneously burn because of the high temperature in the cylinder. Some start burning quicker than some others, locally raising the temps and putting those nearby in adequate conditions for burning as well. At the very begining of the injection the burning zone is somewhat local to the spray but these engines are designed to make the mixture somewhat homogenous as fast as possible putting swirl and/or turbulence in the airflow. That way in an ideal diesel engine a "flame front" would be everywhere in the cylinder and pushing in every direction. At least that's the way I understand it.
Thanks denis! I don't have time for a details repsonse just now, so I'll post more in a few weeks.
No worries on the flip off!
...gb
Post man!
On turbine aircraft engines they go post. Just after the first stage of turbine wheels. Why? I dunno.
Why did I go post, simplicity. Its right there. And I have seen thermocouples on Turbine engines come apart. No idea if my autometer is of the same quality....
Really tho , this is a just a reference gauge. Not something you live and die over. You really think the difference and lag by going post is going to matter? I hardly doubt it.
I also do think there is merit to being able to see what temp the turbo is still at before shutting down. If your thermocouple(pre) is reading 1250, your turbo is at 1250, And the housing isn't going to cool anywhere near as quick as the hot air. But does it really matter? Probably not.
When it comes down to it tho, it is just a reference gauge. You set up your fuel so under heavy load it doesn't go above. I hate driving to the pyro, pain in the ass, retard the fuel a bit. Then once and while look at it on a big ass hill.
And I don't think spikes above 1250 for short periods is of matter(the ones post cannot see). Ever heat metal with a torch? It takes a while to get to hot(red) state, flashing a torch over something for a short period barely does anything. Its the long times at high temp that are going to cause damage. Sustained 1250 plus. Not jumps.
On turbine aircraft engines they go post. Just after the first stage of turbine wheels. Why? I dunno.
Why did I go post, simplicity. Its right there. And I have seen thermocouples on Turbine engines come apart. No idea if my autometer is of the same quality....
Really tho , this is a just a reference gauge. Not something you live and die over. You really think the difference and lag by going post is going to matter? I hardly doubt it.
I also do think there is merit to being able to see what temp the turbo is still at before shutting down. If your thermocouple(pre) is reading 1250, your turbo is at 1250, And the housing isn't going to cool anywhere near as quick as the hot air. But does it really matter? Probably not.
When it comes down to it tho, it is just a reference gauge. You set up your fuel so under heavy load it doesn't go above. I hate driving to the pyro, pain in the ass, retard the fuel a bit. Then once and while look at it on a big ass hill.
And I don't think spikes above 1250 for short periods is of matter(the ones post cannot see). Ever heat metal with a torch? It takes a while to get to hot(red) state, flashing a torch over something for a short period barely does anything. Its the long times at high temp that are going to cause damage. Sustained 1250 plus. Not jumps.
One more thing...
So all your pre turbo guys who drilled into there manifold, tapped or welded. How are you sure you never over torqued or caused a stress spot in the manifold? If welded how did you relieve the stress caused by heat. Did you afterwards heat it up(whole manifold) and then let it cool slowly to relieve it? Or if you drilled and tapped, sure you never over tightened, or caused spot such as a tooling mark that could result in a crack?
Keep an eye on them for cracks. I had no intentions on drilling into my nice new manifold.
So all your pre turbo guys who drilled into there manifold, tapped or welded. How are you sure you never over torqued or caused a stress spot in the manifold? If welded how did you relieve the stress caused by heat. Did you afterwards heat it up(whole manifold) and then let it cool slowly to relieve it? Or if you drilled and tapped, sure you never over tightened, or caused spot such as a tooling mark that could result in a crack?
Keep an eye on them for cracks. I had no intentions on drilling into my nice new manifold.
Darryl:
I'll keep an eye out for any signs of problems with my manifold...but so far no issues. We were very careful in how we drilled, tapped, and torqued the thermocouple in there, and I don't anticipate any problems...you never know though...
I'll keep an eye out for any signs of problems with my manifold...but so far no issues. We were very careful in how we drilled, tapped, and torqued the thermocouple in there, and I don't anticipate any problems...you never know though...
Oh you actually went into the housing on the turbo, not the exhaust manifold?
Not a bad idea, but the exhaust manifold is cheaper to crack I think I saw prices of around 1k for the turbo housing........ CT 26 one.
Not a bad idea, but the exhaust manifold is cheaper to crack
I think I saw prices of around 1k for the turbo housing........ CT 26 one.
I like the harness on your isspro thermocouple. Nice disconnect. The autometer use screws under shrink wrap.
brownbear said:
Yup...that was a big consideration when I was deciding which gauge to go with.
Hey,
As I understand the purpose of the pyro is to determine the safe limits of combustion temperatures due to the relatively low melting temp of aluminum. To gain the most utility from the diesel motor the knowledge of the combustion temp must be known, the fuel must be limited to prevent damage to the motor during the most severe of possible conditions, ie max torque w/high ambient intake temps. This only applies to pre electronic fuel controls in modern engines. The pre-electronic fuel controlled motors were limited by the tuning of the injector pump, modding the engine with turbos and injector pump tuning removes the original engineering design protections and increases the requirment for instrumentation so the intimate internal health of the engine can be monitored. Pre turbo will give the most accurate indication of combustion temps, most post combustion pyro installations are are engineered by the manufacturer for the drop in temps due to the turbo heat/energy extraction by the manufacturer/vendor of the instrument. Most manufacturers of turboed engines specify the required cool down period for a turbocharged engine and use of these guidelines for a modded engine of samr/similar design would be an appropriate starting point.
Gotta love turbos and diesel!
eric
P.S. remember cool down is for more than the turbo, my military truck requires 5-10 minutes cooldown at high idle after "hard running" wether the truck is turboed or not.
As I understand the purpose of the pyro is to determine the safe limits of combustion temperatures due to the relatively low melting temp of aluminum. To gain the most utility from the diesel motor the knowledge of the combustion temp must be known, the fuel must be limited to prevent damage to the motor during the most severe of possible conditions, ie max torque w/high ambient intake temps. This only applies to pre electronic fuel controls in modern engines. The pre-electronic fuel controlled motors were limited by the tuning of the injector pump, modding the engine with turbos and injector pump tuning removes the original engineering design protections and increases the requirment for instrumentation so the intimate internal health of the engine can be monitored. Pre turbo will give the most accurate indication of combustion temps, most post combustion pyro installations are are engineered by the manufacturer for the drop in temps due to the turbo heat/energy extraction by the manufacturer/vendor of the instrument. Most manufacturers of turboed engines specify the required cool down period for a turbocharged engine and use of these guidelines for a modded engine of samr/similar design would be an appropriate starting point.
Gotta love turbos and diesel!
eric
P.S. remember cool down is for more than the turbo, my military truck requires 5-10 minutes cooldown at high idle after "hard running" wether the truck is turboed or not.
has anyone gone post and pre turbo combined?
Otterav said:
the electric fuel controlled units also need to be monitored. Especially when doing something out of the ordinary such as towing. Or modified ie tires gears...
The big diesel ford/gm/dodge, when they get "chips' installed then have to also monitor EGts. Cause basically you just fawked with all the parameters.
My point exactly, change the motor from stock and all bets are offbrownbear said:
eric
Otterav said:
I also think high mileage engine, as injection pump and injectors are worn/outta spec. Things are not stock then either.
Mr Toyota set up the engine at standard conditions, sea level blah blah.... and puts in some degree of either way. So you do need to tune at higher altitudes.
When installing pre-turbo, wouldn't the little metal bits caused by drilling/tapping be bad news for the turbine?
cruiser_guy
Out of Africa / North Africa
Mattse.cx said:
You don't have any till the break through point when drilling and the cutting oil holds alot of the chips when tapping. I did mine with the manifold off the truck but others have done it with the manifold in place and have not suffered any failures that I know of.
- Thread starter
- #39
Mattse.cx said:
When installing the TC to my truck I dipped the drill in white grease and drilled through gradually in several stages,replenishing the grease everytime.Using white grease just means you can see the build up of swarf/filings easier.Did the same with the tap and reckon I must've caught 95% of the filings.I removed the air inlet to the turbo and spun the turbine with my fingers when finished to 'flick' any remaining filings through.Maybe just being extra cautious but started up with no problems.
Greg_B, there is no "flame front" so to speak in a diesel
Denis, a nephew is a civil engineer, and I asked him to pose this question on a engineer forum. It did not spark (ha) a large debate, and the answer is kinda yes and no...but here you go:
http://www.eng-tips.com/viewthread.cfm?qid=165696&page=1
gb
