AT on a graph = ambient temp
IT on a graph = intake temp


Please can you tell me where you would expect each of these probes to be found out of the following:


1 ) outside the building
2 ) inside the cell away from the car
3 ) inside the cell near to the air filter
4 ) inside the boost pipework



Serious answers only please.



Thanks.

 

i might have learnt soemthing from the posts previously dealing with these things so i would hazard a guess at:
AT = 2
IT = 4 (assuming it's in the pipework ratehr than pointing in the general direction of the air filter)

 

not a DD expert, but i would hope that the AT sensor is in the dyno room and the IT sensor is in the filter/intake assy (pre compressor on a forced induction)

 

AT i would have thought would be inside the cell but awa from the car

IT i would say was in the sell near the air filter

 

Dojj, sorry if I wasnt clear in my first post, just people who have the first fucking clue what they are talking about please

 

At - 2
it - 3

 

At -2 (but near a heat source or in a cup of coffee if you want big figures)
It - 3

 

on my dyno

At, on desk in front of cell

It,hanging on wall to side of cell

and its the IT one that people misuse!!

 

Thanks lads.


And just for the record, if you did go for option 4 not option 3, what effect would it have on the power output?

UNDER read
CORRECTLY read
OVER read


?

 

AT - 2
IT - 3


If the probe is in the intake it wont correctly sample the air temp due to the probe sampling temps of the pipe itself (heat soak), rather than the air passing through it. Which is traveling that quick it wont have time to even think of stopping to warm up.

 

f3=find
f5=refresh
f10=file

 

The hotter the intake temp the more power the Dyno will add to the correction factor.

The probe would gradually get hotter and hotter and hotter over a period of runs and that engine would be getting more powerful each time what an engine!

 

The general rule-of-thumb is a tolerance of up to 8° between AT and IT before it starts compensating by an amount that may not be believeable. We certainly prefer to see these kinds of figures.

 

Thankyou for your input lads.

Was trying to explain something to someone, and they thought I was making it up about IT giving mis readings.

Here is the graph we were discussing:

 

i got one of them right and was going to put 3 but wasn't clear on what "intake" was as it could be the air going into the engine or the temp of the air going into the inlet manifold

so, when it's described as "intake" what is being taking in?

thank you please

 

i try and keep them the same much better for tuning as you know if you make a change in map you can see change in graph rather than thinking its a correction on power for intake temps!!!

 

Well i never.... our old friend Alan

 

why try to do anything? surely they should be used as intended to measure, not be fudged?

 

AFAIK they only correct.

ie "if it wasnt so hot your engine would have made more power"

rather than actually measuring a correct figure

 

i dont use the sensor in the airfilter as they just end up with figures like the graph above

when mapping with the inlet temp probe near filter after a few runs on dyno it can increase so figures become inflated

so mine hangs at side of cell

 

It's in the wrong gear too.

 

Why arent these rollers showing actual measured power and corrected power according to SAE/DIN whatever?

 

We try to get the IT probe in the vicinty of air of a similar temp to that being consumed by the engine, so in the cell close to the car is good, but not in the engine bay.

If its in the engine bay itself, the air is much hotter there and not a true reflection of the actual intake temp because the air going into the engine hasn't been in the engine bay long enough to get that hot. That's my slant on it anyway.

 

that's nonsense. it should be in the intake so that it measures intake air temperature. unless it has a huge thermal mass, the sensor will read the actual temperature of the air being ingested by the engine in that position (wether it has been heated above the AT or not).

 

On the graph in question, the person informs me the intake temp probe was put INSIDE his boost pipework.

I personally think he MUST have that incorrect, as I just dont see logistically how you would get it in there, but on the other hand it certainly looks like it was!

 

As far as im aware it takes the IT reading before the run actually commences and uses that as a correction factor, it doesnt average it during the run, so it wouldnt be measuring the actual air going in, also I suspect the probe couldnt react that quickly anyway as they look fairly substantial to me and very fast acting probes have to be mega lightweight by definition.

 

Chip,

Where is this leading too... ?

 

rolling roads are dangerous in the wrong hands!

I can just see the operator telling his cust how good his mapping is as the power is going up and up( cos he is moving the probe!)


LOL

 

Why use a rolling road that alters the figures at all?

 

as far as im concerned its my dyno and thats how i run it!!,i dont have to please you only myself and im happy with results i get without over reading

 

ALL rolling roads and engine dyno's adjust figures

Its called normalisation !

 

But the same could be said for a Dyno that doesn't measure a real-time acceleration run?

 

Are these rolling-roads intertial only or do the feature electromagnetic brakes and variable load?

 

They're 'steady state', typically using eddy current absorbers.

 

Fascinating thread guys

 

so where should this temprature measurement be taken from then?
one side of me thinks that putting it as close to the actual inlet manifold as possible because then you have the actual temprature of the air that is being used by the engine, after it's gone through whatever induction pipework form the air filter, as possible to see what sort of fueling you would need

the other side of me thinks that it should be placed at the air filter side so that you know the temp of the air coming in, and that the sensor may misread due to it being cooled/heated by the air rushing past in the inlet manifold and generally being hotter than it should due to the heat coming from the engine

is there a difiniative right or wrong answer to this or does it depend on the operator in question?

 

Because if you dont, then you could run your car up on a very cold day and get a massively inflated figure that it wouldnt be able to adjust back down, likewise the opposite on a hot day.

And because if you build two identical engines and roller one on a hot day and one on a cold day they would get totally different figures.

How the hell is that useful for developing an engine?

Any engine from december would seem massively better than any engine you built in july!

 

Its supposed to be a measure of the temperature of air going into the air filter.
Where you choose to get a reading from to represent that is a matter of some debate, but not a lot, essentially it needs to be somewhere between the air filter and the dyno wall, where you think it best respresents the actual temperature of air that will go into the air filter, often putting it to close will result in it picking up radiant energy from hot engine components that will make the sensor hot but wont heat up the air going in to the same extent.
Im with Gary in that two far away is better than too close if you have to be either.

On a turbo car, putting it AFTER the turbo is always going to make it think the air coming into the air filter was hotter than it really was as the turbo compresses the air, which heats it up! (pv=nrt)

 

Exactly what I do, take it from next to the air filter intake or roght next to it.

 

Martin do you have some graphs to show the IT you get doing it this way mate?

1 at the beginning of a long mapping session and one at the end would be perfect