Let's talk about IAT's and Heat Soak
 

OK, for those of you who track the SL I wanted to add some insight about how the supercharger in my opinion works on our cars. Now let’s not all get rawled up here as this may very well just be my issue and not yours. However the case, I strongly feel that it applies to all supercharged SL's. I just replaced my IC pump about a week ago and today I decided to take her on a nice little run on the interstate. Here's the situation, I just started her up in the garage and let her warm up for about roughly 10 minutes or so and drove to the gas station 2 miles down the street. Stepped inside and purchased me a Red Bull and started her back up and hit the interstate. As soon as I get off of the ramp, I gunned it and what do you know a F_ _ king stall again. At this point I’m thinking my supercharger is screwed up because I know I just replaced the IC pump brand spanking new from the dealership, which by the way does not take a GED to replace. At this point I just want to squeeze the trigger on myself, never pull the trigger you might miss, always squeeze the trigger. Anyway, so I continue to drive at the normal speed limit which is 60 mph and finish drinking my Red Bull. Well about 15 minutes into the drive, my car feels perky again and starts issuing a can of kick ass out to everyone on the interstate, WTF, over? She came back to life, what is going on here??? Hmmmm, dumb founded at this point of course. Now some time ago FLSL55 here mentioned something about our intake air temperature (IAT) and that it needed to be somewhere below 110 degrees or she will start to suffer from heat soak. He also suggests that the 55’s should be driven for a while until the IAT’s get to the desired levels before taking your place at the tree and just letting your car idle was not going to be good enough, the car must be driven around first to bring those temps down. Well I was thinking, this actually makes sense, and maybe that’s what happened to me, my car was not warmed up properly and needed to be brought to a proper operating temp so that my IAT level was well below 110 degrees. So by me driving around for about 15 min, that must have done the trick. Now I don’t have one of those scan gauge II devices to let me know what my IAT’s are, but I do take notice to my engine temps. In my car the temp reads anywhere from 90 to close to 100 degrees as we all know it reads in 10 degree increments. However, today it was as low as 80 degrees when she started running right. Does anyone here think that my theory is correct or am I totally off track? I believe that FLSL55’s theory is correct and that my car reached the perfect operating temp with the IAT and all, therefore allowing me to put a smile back on my face. On the flip side, is this what happens to us in these 55’s, we need to hold off before jumping on somebody until our engines reach optimal operating temperature’s? Man, I wonder if the turbo’s are better than the supercharger’s, since they run off of the exhaust? Sorry guy's for the long post, most will probably not read this.
Chuck.

Did you check and cleared codes?
Have you checked/replaced your pump relay?
What's going on with your car is not normal.

Cleared codes? I never had any codes displayed to clear. As for the pump relay, I have also replaced the auxiliary pump, is that the pump relay that your talking about? As for my car, I really don't know what else to look for. I have a new IC pump, auxiliary pump, good radiator, all new pulleys including the clutch for the super charger, maybe my fuel pump is bad??? :nix:

The codes may not be able to be seen with a ODB2 scanner. Mine set codes all due to the IC pump causing causing a overtemp issue and forcing my AF rich. It did not go back to normal until I reset the ECU with the Star computer. Then full power came back.
The aux pump will only cause low heat during idle.
The IC pump has it's own control relay in the relay box, it may be intermittent. Cheap to change.

K, thanks for the Intel, but I was reading else where that the relay had nothing to do with performance.

Hey Charles,

I must not have been totally clear.

I'm talking about a fully warned up SL55. When you shut the car off for 10 to 15 min, the intercooler temps (since it's full of coolant) raise to over 150 degrees' F.
When you start the car this is what the IAT temp shows on the scanguage. 150 degrees or so.

You need to get the IAT temps DOWN, to 110 degrees F or below to have full power. Once the ECU see's IAT temps above 120 it starts to pull timing hence you loose power.

You need to drive the car to get the temps DOWN. Just sitting at idle won't do the trick.

I have proven it time and time again on my car.

Do you mean you supercharger shuts off or the car stalls? If the car is stalling than something is wrong and you need to take it to a shop. If the supercharger is shutting off, your IAT's are above 220F!!!! Not good at all.

You need to buy an scanguage II my friend. It will tell you how healthy your car is. There is a 30 day return policy.

The relay controls the pump via the ECU, if it fails or becomes intermittent your IC pump will not come on when commanded by the ECU.
You can test it by jumping the terminals in the relay socket to make the pump run all the time and see if that's your problem.

Guess what? I am missing the damn fuse entirely, some ass wipe screwed me probably when in servicing.

Good deal, You found the problem I'll bet ;-)

Yes Sir, I will have to invest in one this week and it's the supercharger that's shutting down on me. Thanks for your advice it will be used.

Check this out brother, I don't know if you have the schematic readily available, but on the drivers side relay box I'm missing the "F" fuse which controls the return pump, also the large 40 amp fuse which is the "F2" fuse it displays no life through my test light.

On the passenger side relay box, I'm missing the "N" fuse which controls the air pump and the 40 amp "F31 and F32" fuses which only one is supposed to be operational, that fuse according to the schematic was in the wrong slot and it does not light up either, it controls the secondary air pump.

I spent almost an hour checking every fuse that our cars have including the one in the trunk and the ones behind the passenger seat and they all are operational except for the ones I just stated had deficiencies. Thanks for your time the both of you.

I don't have my computer with me today, but I'll check when I get back to the ranch tonight. I may have time between meetings to check for you.

Thanks but don't waist your time. The "F" relay fuse is only for the SL500, I just got back from the Benz dealership. Now I am back to square "A". I made an appointment to have all of my codes checked and cleared if not already. One thing I failed to mention is that every once in a while I get a check engine light. I have always thought that to be linked to either fuel or exhaust according to the manual and never had it researched. Anyway, that might be my problem, I may have internal issues that require attention.

Your exhaust is not stock correct? (res delete) That could be the problem.....?

Resonator delete will not cause a CEL. He has another problem.

Had a throttle actuator set a code once when I stabbed it in a turn, guess the adaptive learn mode got a suprise with an aggressive move ;-)

No, my exhaust is stock Bro.

I don't have the same car or engine you have but I track my SRT-6 (supercharged 3.2) and my IAT's are between 138º and 172º during the 20 minutes of racing. In normal driving they stay at 15 to 20º above ambient temperature, perhaps a touch less on the interstate. On the drag strip they can be as high as 150º when I go to get in line and just driving to the tree they drop to around 118º all depending on ambient temperature. At the end of the 1/4 mile they have reached 160º. They go up fast and come down almost as fast if your moving. The cooler the IAT's are the more timing the ECU will permit, at least thats what I'm seeing on my data logs.

Les

Thanks for the info Les, however I have some internal issues and just can't figure it out just yet. I'll have to let the boys at the dealership hook her up to the Star system to see exactly what is going on with my car. At this point Bro, I have already replaced damn near every part that the car can have replaced minus the supercharger itself. If I don't get this resolved soon, she will be going away, I don't have the time nor the patience to invest much longer after this to get her in order. :wall:

Ahhh, I thought you deleted your resonators. My mistake. ;)

I did, but I kept them because I was not sure how I felt about removing them, so I had them put back on. You have a damn good memory, I almost forgot. :D