125 replies to this topic

[alexb]

Inlet temperatures should follow boost levels. Major influence is boost, followed by humidity. I assume however that humidity doesn't change much in a run. For dry air it's pretty simple to calculate. Assume 20C outside T:

- at 0.8 bar boost: 73C

- at 1.0 bar boost: 84C

- at 1.2 bar boost: 94C

- at 1.5 bar boost: 108C

At 100% compressor efficiency.

 

What the real IAT will be will depend on how heat soaked the components are. Under normal driving conditions that never happens as you're only under boost now and then. So component temps stay low and you have a lot of heat capacity as a buffer, cooling inlet temps down. On track it's the other way round, everything gets heat soaked and instead of having a heat capacity buffer, you now have the reverse.

 

Looking at the graphs, I still think there are two wires crossed and the T reading from the TMAP sensor is somehow off.

[CHILL Gone DUTCH]

I will do some testing to confirm without the car moving later holding certain revs and see affect of inlet temps

[alexb]

Log IAT, MAP and RPM while moving the car and accelarating to get it under boost. You can't get a non moving car to boost, at least not for more than a split second and certainly not while holding revs. Might also be illustrating if you start logging with engine not running to see what happens to IAT when you start the engine. IAT should follow MAP from the moment you're above atmospheric. At stationary you have something like 0.2 bar if I remember correctly and zero influence from the SC (by pass). IAT should be same as outside. Everything above atmospheric and the SC is actually doing something and IAT should go up and follow MAP until off boost.

 

And you might want to ask Peter, he's very good in this stuff as he's seen millions of logs

[Exmantaa]

I will do some testing to confirm without the car moving later holding certain revs and see affect of inlet temps

 

 

We looked also to your graphs and thought that it was a lot of latency in the system.

Check temps on a cold car/ignition on.

Or remove the TMAP from your manifold and do some temp testing. (Ambient air, maybe hot air gun etc.) 

[Exmantaa]

Log IAT, MAP and RPM while moving the car and accelarating to get it under boost. You can't get a non moving car to boost, at least not for more than a split second and certainly not while holding revs. Might also be illustrating if you start logging with engine not running to see what happens to IAT when you start the engine. IAT should follow MAP from the moment you're above atmospheric. At stationary you have something like 0.2 bar if I remember correctly and zero influence from the SC (by pass). IAT should be same as outside. Everything above atmospheric and the SC is actually doing something and IAT should go up and follow MAP until off boost.

 

And you might want to ask Peter, he's very good in this stuff as he's seen millions of logs

 

The system on the SC is not so straighforward, as it has a lot of latency and heat build-up in the system that confuses things. Also I think the hot PCV gasses can skew your IAT measurement a bit @ idle and low load, but that is only a tiny amount of air/gas....  

[CHILL Gone DUTCH]

Ok I've just done the test with hair drier and In open air And the temp readings are going up as you put heat on as you would expect, As for the delay in the reading you speak off ?? I'm not sure what causes that

[alexb]

 

Log IAT, MAP and RPM while moving the car and accelarating to get it under boost. You can't get a non moving car to boost, at least not for more than a split second and certainly not while holding revs. Might also be illustrating if you start logging with engine not running to see what happens to IAT when you start the engine. IAT should follow MAP from the moment you're above atmospheric. At stationary you have something like 0.2 bar if I remember correctly and zero influence from the SC (by pass). IAT should be same as outside. Everything above atmospheric and the SC is actually doing something and IAT should go up and follow MAP until off boost.

 

And you might want to ask Peter, he's very good in this stuff as he's seen millions of logs

 

The system on the SC is not so straighforward, as it has a lot of latency and heat build-up in the system that confuses things. Also I think the hot PCV gasses can skew your IAT measurement a bit @ idle and low load, but that is only a tiny amount of air/gas....  

 

 

I should have mentioned that my way of reasoning applies to cold systems. Heat soaked is different, but it will take a while to get there. So from cold, the only way I can see is as above. The hotter the system gets, the more latency you get, as the system loses it's ability to cool down the charged air.

 

But look at the first graph, the one that starts with an IAT of 65C at stationary. Looks like he blips the engine a couple of times (sharp peaks in RPM) and T goes down to 50, after that it looks like some driving (hard to say without a time scale), as RPM goes up/down more gradually. But still if you look at the T and RPM graphs, they are the exact opposite. With higher RPM, T goes down and lower RPM, T goes up. Doesn't make sense, even with latency where you may start at a higher T and the system reluctant to cool down, the general trend should still be  the same.

 

I would check by making a log using my own car, but no spare time .... and just realize I don't have a TMAP. Well, I have one, but it's on my desk, waiting to be installed.  

[alexb]

Ok I've just done the test with hair drier and In open air And the temp readings are going up as you put heat on as you would expect, As for the delay in the reading you speak off ?? I'm not sure what causes that

 

There goes my theory it seems ...

 

The latency that Exmantaa speaks of is not a delay in reading of the T sensor. There is a delay caused by the sensor, but that's very small (caused by the sensor element heat capacity, but that's tiny compared to the rest of the system). I think he's referring to the whole intake system reacting as a temperature buffer. The higher the temperature of all the components is, the more the passing air will soak up heat from them and the higher your average IAT's will be.  

[CHILL Gone DUTCH]

there was a big difference
 
 

 

Is it worth mentioning that the chances are that the car was sat for a long period of time probably running at 100 engine coolant temp before I started logging also my manifold sits straight on to the inlet of head there are no fancy heat proof gaskets just the standard one

[alexb]

Ah, I was thinking about that. The system was heat soaked and getting some air in from stationary actually cooled it. That also explains the flat tops of some of the peaks. It reaches an equilibrium lower than when running stationary. It actually looks like you're cooling down the engine by getting some decent air through it. And as the components are hotter than even mildly charged air, the system cools down.

 

If or when you're going out for a run, can you please log MAP with it? The amount of boost should directly relate to the IAT you see. With some effect from the laminovas and the system latency

[CHILL Gone DUTCH]

It's only a case of ticking a box Give me a min

[CHILL Gone DUTCH]

[alexb]

Starting with a hot engine again? And is the first part where it starts off with a T of 79C and a pressure of around 0.6 bar stationary? Stationary should be around 0.2 bar. And again you see that T goes down even under boost ... been staring at this for half an hour and just can't get what's happening. All I can think of is that a lot of cold air is sucked into the hot engine and it cools it down. When that stops, it skyrockets again due to the heat capacity of the engine. Pretty thin ice to skate on tbh. And I would like to be able to explain the flat spots in the T curve. And how they change.

 

Towel in the ring time for me I guess

[CHILL Gone DUTCH]

here is one with a cooler start,

 

[CHILL Gone DUTCH]

Starting with a hot engine again? And is the first part where it starts off with a T of 79C and a pressure of around 0.6 bar stationary? Stationary should be around 0.2 bar. And again you see that T goes down even under boost ... been staring at this for half an hour and just can't get what's happening. All I can think of is that a lot of cold air is sucked into the hot engine and it cools it down. When that stops, it skyrockets again due to the heat capacity of the engine. Pretty thin ice to skate on tbh. And I would like to be able to explain the flat spots in the T curve. And how they change.

 

Towel in the ring time for me I guess

As for the steps it could be because the log was quite short and the time across the top is actually a short period

[haggi961]

To bring a old topic back to life I'm just wondering what people thoughts are on the liners being rated to 750bhp and not 400bhp?. I'm just wondering if there's any proof that it says the liners are rated to 400bhp because in the build book it says they changed the liners from 400 bhp to 600bhp but it doesn't state they are only good to 400bhp.

[The Batman]

only one way to find out Haggi

[haggi961]

I think 400bhp is going to ok for the liners if they tested it to 750bhp plus it's done with a turbo where as the charger isn't as bad with the torque.

[The Batman]

Plus you will struggle to get more than 400 anyway Intake manifold

[fezzasus]

Just remember there's a very big difference between the engine being able to operate at that power output, verses the engine components being durable at that power output. I don't believe the GM work did any durability testing.