I don't know why you would get any knock retard at idle...would like to say that it was false knock, but that would be only opinion. That knock at part throttle cruise is strange also...is that at a shift or top gear cruising down the highway? Were you scanning anything else when it happened? If you could post the entire scan I believe a lot more people could take a guess at what's going on.

I saw the pics you posted of the stock intake...since its essentially a Fender Well Intake I would think Intake Air Temps would be ambient. Where is the location of the IAT sensor?

Again, sorry for all the questions, but you seem to be the only one with a scanner and a Cobalt SS.

 

Well If I have any idea how to post the scans I would. It's just raw files that need to be opened with the autotap application. Posting them wouldn't do much good unless you have the software.

The IAT sensor is probably located after the blower. Since the blow creates excess heat as it compresses the air and the intercooler removes the heat the IAT is so of a measure of how good the intercooler is doing at keeping air temps down. There is a lot going on in that area of the car and unless I got the shop manual I wouldn't even know where to look for it or what it would look like.

 

There are two intake air temp sensors. One is integrated into the MAF assembly (before the blower). The other is integrated into the MAP sensor in the intake plenum (after the blower).

(incidentally, there are two manifold pressure sensors as well, as well as a baro sensor! though i suppose technically the first sensor shouldn't be called "MAP" because it's not in the manifold - i think they call it SCIP - supercharger inlet pressure. either way, there are 3 pressure sensors, one at the SC inlet, one in the manifold, and one baro)

If you'd like to know the exact pinouts for the MAF/IAT and/or MAP/IAT assemblies, send me a PM.

 

there should be some way to convert the file to a spreadsheet. What type of file is the autotap file? if you could, go to www.yousendit.com and email the file to one_slow_grandprix@hotmail.com

Ill see if i cant do something with it.

 

Okay, this opens up a new line of questions...which intake sensor is autotap reading? I would guess it's the one integrated in the MAF since Zinner reported an IAT of 77 degrees. I'm thinking the one integrated in the MAP would be closer to engine temp (way higher when under boost). This also brings up the question...does autotap have the ability to read both sensors? If it can that would be really useful in baselining the stock intercooler and evaluating any mods to increase it's effectiveness.

Zinner...I've seen autotap scans posted in other forums so I'm guessing there's a way to export the data into something...comma delimited (spl?) format, .CSV, etc. that a spreadsheet program (like Excel) can read.
If all else fails you can always take a screenshot (shift+Print Scrn) and saving the file as a JPEG. (alt+Print Scrn will take a snapshot of just the open window). After taking the snapshot just open any picture editing program (like Paint) and edit->paste. Save the file a JPEG.

 

If it was reporting 77 degF, then it absolutely was the pre-SC sensor in the MAF. You're right in assuming that the post-SC temp should be substantially higher. Probably 50-200 degF higher. You could look it up, Eaton has a deltaT curve for the M62 on its website.

It is definitely technically possible to read data from the second sensor. You'd need to set the scan tool to read a different area of the ECM's memory. I've never used the AutoTap, so I don't know if it has the capability to do that or not.

 

Reports 77 when it's 55 outside.

So I would think it's post supercharger.

 

Let's clarify the terminology a bit, so I know we're talking about the same thing. By PRE-SC, I mean the sensor on the air filter side of the supercharger (BEFORE the air is compressed). By POST-SC, I mean the sensor on the manifold side of the supercharger (AFTER the air is compressed).

At 77F, it's absolutely the PRE-SC sensor. The pre-SC sensor should be just slightly hotter than ambient temp (just like you said).

The post-SC sensor will be way WAY hotter than 77F. Probably at least 150F. The act of compressing the air heats it by at least 70+ degrees. Even up to 150-200+ degrees, depending on how fast the charger is spinning.

It's definitely the pre-SC sensor.

Edit: Now that I think about it, maybe not 200+ degrees hotter, depending where the sensor is in relation to the intercooler. If it's downstream of the intercooler, it shouldn't be that hot at all. I'm not entirely sure about the physical position of the sensor in the manifold, so I dunno. Still, 77F has to be pre-compression temps. It'd be nice, but the intercooler just isn't that good.

 

There 2 intake air temp sensors...one is built into the MAF sensor(MAF/IAT) and lives just after the air filter in the fender....the other is part of one of the 2 MAP sesnors....the SCIP is the supercharger inlet pressure sensor and it houses the other IAT it is mounted directly to the top/front of the SC after the throttle blades and before the rotors...its on the smooth right hand side of the blower before the fins.. the other MAP sensor is the TMAP and is located on the intake to the left of the SC assembly. the BARO sensor is located in the area between the throttle body and cam cover..

IAT1 is the one in the fender, IAT2 is on the SC....both are accesible via a Tech2 GM scantool or a snapon Modis scanner...i dont know which the autotap "sees" probably the IAT1(MAF/IAT) since that is a required OBDII Mode6 parameter

 

Very intestesting. I didn't see an extra IAT varaible I could pick, I did notice from driving it those that the temp quickly dropped as I got moving.

I got the advanced GM support with the autotap and I am waiting on the CAN software support from autotap. Autotap told me their hardware is already CAN compliant (J2284) and it's just an upgrade.

I emailed autotap to see what they say about the second sensor. I realize the autotap isn't a professional quality tool but they do list that they support IAT on their website.

 

Exactly what I said before.

zinner - pm me if you get a chance. I may be able to help you with the autotap.

 

Okay lets see if I have this straight...IAT2 is located on top of the blower? I was hoping it would be in the intake manifold after the intercooler. My pea-brain is failing to understand what the IAT2 temps would be used for. If it's used for more accurate IATs at the motor, why have IAT1?

 

I do not believe this is correct. I should have read his post more clearly.

The second IAT sensor is integrated with the POST-SC MAP sensor. Not the PRE-SC MAP sensor, or SCIP.

You can see it clearly in this photo. Or look at any other engine bay pic. If you zoom in, you can see that the sensor on the top there is a 3-wire sensor. Therefore it must be a pressure sensor only (5V ref, GND, and SIG). The post-SC pressure sensor will have 4 wires - the 4th is for the temperature sensor built into the assembly.

https://www.cobaltss.net/gallery/sho...atid=newimages

 

Alright, I was feeling inspired, so I made a pic so there's no more confusion. No laughing at my Word skillz. Like the lightning bolt on the SC? I thought it was a nice touch....



This just shows the airflow related sensors. Obviously I'm not showing others like coolant temp, cam/crank sensors, etc. Also note that there is one more pressure sensor - the BARO or atmospheric pressure sensor. It's located outside the intake tract, so I didn't show it on here...

IAT1 (pre-SC) should normally read slightly above ambient - like 77F.
IAT2 (post-SC) should read anywhere from 50-150 or even 200 degrees higher than IAT1 depending on throttle, engine RPM, etc.
SCIP should read pretty high vac (~30kPa/5psi absolute) at closed throttle, very close to atmospheric (~100kPa/14psi) at WOT.
MAP2 (post-SC) should read exactly what your boost gauge says (plus atmosphere, depending how you wanna take your reference - ex 12psi on your boost gauge = ~26psi absolute)
Hope this clears stuff up.

 

Thanks DanM...you seem to have access to a lot of good info on this car.

I am still curious as to the exact location of the MAP2/IAT2 sensor...I reallize it is in the intake manifold, but is it before or after the intercooler? If it's before the IC it will be useful in gauging the SCs effeciency...and to some extent the intake, but if it's after the IC it will also be useful for gauging the effeciency of the IC as well.

This would be great for checking the effectiveness of any mods to the intake, SC, and/or IC.

 

Yaj....DanM is correct in his pictogram...the MAP2/IAT2 (otherwise known as the TMAP) is located on the INTAKE MANIFOLD, on the left(facing the engine) side of the engine..its a black four wire sensor...should have BOSCH written on it...( I had to go look at the engine to verify this....GM Service Information is incorrect) The Supercharger Inlet Pressure sensor(SCIP) is the 3 wire sensor on the SC in the area between the throttle blades and the SC ribs.

 

That's good news Maven...from your discription it sounds like the MAP2/IAT2 is after the intercooler. I guess now I need to find some software that is capable of reading that info.

 

That doesn't cost 7000 dollars. BTW autotap does not support it and didn't sound like they were willing to help with it.

 

I hereby bump this thread in honor breaking 6000posts. I think this was my first post.

 

Cute


6k was years ago