The reason I ask is that if I drive my car here in the heat, park up and leave it half an hour, then come back to it, I can easily see 56 degrees at ACT, the underbonnet temperature being around 45 degrees.

If I drive carefully for a couple of miles, both drop to around 33 degrees, but no lower, since the air temperature is around 35 degrees.

So what's safe, and what's not?

 

they are all safe, its what load the engine is under that matters with regard to safety. IME on a turbocharged car with about 15 psi boost i would expect to see about 30-35 degrees IAT, any more than that is asking for det/loss of power.

 

Just keep to half the speed you did last time you were there, should be fine, if you go easy on the diver's boot...

dunx

 

reading the OP's thread again, it is very clear that you are seeing heat soak. This is not the actual air temp, but in fact the underbonnet temp once a car is parked up as everything trys to become the same temperature (heat soak off of hot bits onto cooler bits, that would normally sustain a cooler temp when running due to airflow and water flow) Nothing to worry about as long as the temp comes down after a short drive.

 

The OP is on about ACT's not IAT's. Your 30-35des IAT could be totally irrelevant if the OP had a monster FMIC and nitrous / meth / water injection.

Charge temps (post IC) are what's important to measure.

 

they are the same thing, i think it is you who is confused.

 

Not to me....

I consider iat to be inlet air temp pre turbo and act to be air charge temps post turbo. Never thought it to be anything different IMO.

 

Thats not what it has been on all the cars i have ever mapped mate, The ecu needs to know what the temp is of the air entering the engine is, its not interested in what the air temp is before the turbo, hence "inlet air temp" i at the inlet to the engine, that why all IAT sensors are in the manifold or very close to the throttle body.

 

I'm talking of the temperature of the air just before the inlet, AFTER the turbo and after the intercooler.

I also monitor inlet temperatures on the air filter.

And dunx: the diver's boot is firmly left at home. Even small speeding here now carries a heavy fine and any more than 30mph over the limit is loss of vehicle, and €1000 fine.

With the limit only 56mph, and lots of nice, quiet roads...........

 

Chaffe,
Even for scoobys mate? They take the air temp from the maf sensor which is pre turbo, assuming oe ecu - spec c group n map aside. Unless my drugs need changing which I can't discount! Lol

 

Agree the temp id taken by the o/e ecu at maf pre turbo. Except spec c. Ofcourse the o/p doesnt say what ecu he's using???

 

Agree the temp is taken by the o/e ecu at maf pre turbo. Except spec c. Ofcourse the o/p doesnt say what ecu he's using???

 

It's a 98 on an "S" plate, so it's using a Link, mapped by Bob Rawle. Old technology, but the only stuff available really when I first bought, and it DOES work well

 

IAT = Inlet Air Temperature. This is sometimes measured by a probe in close proximity to the air filter, when on the rolling road for instance and Classic STis have an air temperature sensor at the beginning of the inlet tract just inside the engine bay to measure IATs and this information goes to the ECU. A WRX does not have this probe.
ACT = Air Charge Temperature. As a rule these are measured just prior to the throttle body and the best way of discussing ACTs is "x" deg.C above ambient. This assumes you are monitoring the ambient temperature.

In hot conditions particularly with a top mount and to a lesser extent with a front mount, there can be a lot of heat soak from the warm or hot engine. The top mount obviously suffers worse but it also effects front mounts to a lesser degree. (If you pardon the pun )
I have seen top mounts on many occasions beyond 70 C. and front mounts close to 50 C. but once the car equipped with the front mount is moving forward at normal road speed the temperature comes down very quickly. This also happens with the top mount but more slowly and bear in mind the top mount is sitting above the turbo charger.

I cannot tell you what temperature is safe or unsafe but common sense tells me you never give it the beans away from a heat soak situation until the intercooler, top mount or front mount, has had adequate time to recover.

 

Diven the O.P.'s previous problem au Francais, I recommend a vast reserve of paranoia, and a bucket of caution, cooled to -270 K

dunx

P.S. Just add water injection when you get home...

 

So are you saying a subaru cannot compensate for rising act then if they have put the IAT sensor before the intercooler? every car i have ever worked on, except subarus it seems measures the temp of the air going into the engine. This way the ecu can calculate the air density and inject the correct amount of fuel/produce the right amount of ignition advance for that given load on the engine.
It seems that people are also using IAT as a description to the sensor at the air filter, this is only the case with subarus, Every other manufacturer will describe this as the temp sensor in the inlet manifold/close to the throttle body. On every other forum (including a few tuning forums), ACT and IAT are exactly the same thing and are both measured at the manifold. Regardless to the facts i have stated, the OP's car is still suffering from heat soak due to the interheater being above the engine.
It seems that the MAF sensor will need ambient air temperature (NOT inlet temp) to caculate air density, but almost all cars will also measure Inlet air temp at the manifold to produce an accurate density of the air going into the engine as obviously its heat and density will change as it passes through the turbo and intercooler.

 

Firstly, we are a Subaru bbs and it is Subarus we are talking about so please do not complicate things with This statement is not quite accurate anyway.
Secondly,The O.P. actually runs a Hybrid FMIC. I only know this because we fitted it.
Thirdly,Absolutely not at all. That is not what I am saying.
On Classic cars for instance, the intake air temp sensor is fitted to the STi only and locates, on the O/E car in the black plastic duct feeding air from the area above the headlight as already described above in my previous post.
Utter bollocks.
AIT = Air Inlet Temperature. Nothing more, nothing less. The air temperature entering the inlet tract. Next time you see a printout from a DynoDynamics RR look at the information across the bottom of the print out and satisfy yourself as to the placing or location of this probe. (Not really relevant on a turbo car IMHO but that is the way a respected international Dyno manufacturer does it.)
ACT = Air Charge Temperature. This is the temperature of the charge air entering the engine often measured close to the throttlebody. On a turbo engine the IAT and ACT can vary signifigantly. Please do not confuse this with naturally aspirated engines.
I do hope this helps.

 

So how come on all the turbo cars ive mapped the Inlet Air Temp sensor is in the inlet manifold or very close to the throttle body? and they have no other temp sensors in the loom other than coolant

 

Are you mapping Subaru turbos then?

If so then you must be puzzled why knock is appearing at what you think are low charge temps?

 

The air inlet is where the air goes through the filter and in to the inlet tract or thereabouts.
The air charge temperature is exactly what it says.
If you house an air charge temperature sensor in an aluminium inlet manifold you will get heat soak from the aluminium inlet manifold affecting the sensor and this has to be offset as you are not actually measuring the actual air temperature ie. the air charge temperature.

 

That first bit is not true, once it goes through the turbo and intercooler its temp will change several times, it is the temperature that it enters the manifold at that is important. The heat soak will be minimal on the sensor in the manifold as they are designed to measure the temp of the air flowing through them not the temp of the object they are screwed into.
I map standalone management, not subaru specific, and this is what i have been discussing (as mentioned above) just trying to clarify what subaru are trying to achieve, or how they are achieving it by measuring the air temp soo early on, i could understand it if they measured it twice (once at the maf, and then again at the manifold) Prehaps due to the fact that no air charge (should) be lost that this system works for air density, and that is why they can run soo bad if a dump valve is fitted.
I am currently in the process of retro fitting aftermarket programmable engine management on my subaru, It will require an IAT sensor as close to the manifold as posible (after the intercooler) as it uses this value to calculate air density, but this system will run with a massive air leak without comprimising AFR or ignition timing (of course the turbo will suffer). Just be aware if you ever work on anything other than a Subaru that people will be talking about IAT sensors, and they will be in the manifold.

 

In my experience ACT sensors are best fitted in the intercooler pipework approx 6-12 inches from the throttle body. This reduces the potential for heatsoak from the inlet manifold especially when the throttle is closed, seen plenty of this from our circuit racing Sierra Cosworth.

Martyn

 

O RLY?

So AIT and IAT sensor locations are different?
It may just be that people can't type or are ignorant?

ACT removes any confusion.

 

most certainly, and that is where the confusion has started me thinks! as i originally said IAT.

 

as my very fisrt post says "IAT" lol

 

Argue as much as you want but AIT and ACT are two different things for most people, DynoDynamics and their hundreds of operators included who do all makes of car not just Subaru.
Their base line information is : BP Barometric Pressure. RH Relative Humidity. AT Air Temperature ie ambient temperature. IT Inlet Temperature.
The probe is about 3mm diameter 200 long and placed on or close to the cone filter or in the inlet scoop before the pannel filter.

As Martin says, on an FMIC equipped car the best place for an ACT probe is in the thin wall pipe feeding and close to the throttlebody. Placing the sensor in the alloy inlet manifold results in a distortion of the reading that has to be compensated for because the brass sensor picks up heat from the manifold as well as air flow temperature.

The IAT is the temperature of the air being fed to the turbo compressor and can be influenced by under bonnet heat/temperatures.
The ACT is the temperature of the air entering the engine, usually measured close to the throttlebody. This air has been compressed so temperatures can rise to as much as 200C. It is then forced through an intercooler core and pipework to the throttlebody and into the inlet manifold. An efficient system in the cruise may be at 2-6 C over ambient and on a powerful Subaru, given the beans it may be 12-20C over ambient.

Come back with whatever you want but I see no point in going any further with this discussion.

 

Im not arguing, im agreeing. ACT and IAT however are the same, the AIT or ambient air temp are also the same.
Answer this; how does a subaru retard ignition timing or adjust afr to stop det if the ACT rises? it wont know if it has no temp sensor in or near the manifold? Surley cant reley on the knock sensor alone, because when it knocks its already too late.

 

It seems harvery cant see the difference between AIT and IAT, im sorry if your dislexic and appologise now

 

roflol @ above

I'm not sure what "dislexic" is... is that something close to being "Dyslexic".

Chaffe,
What do you mean by AIT? Ambient Inlet Temp or Air Inlet Temp?

 

Don't correct me if I'm wrong but am i right in thinking that all these sensors are the same but dependant on where you fit them= what you call them.Although with some other makes they just call them the same regardless of where there fitted.