Well kinda ongoing...

I've been playing around with temperature sensors this weekend, by placing them in different places in my engine bay to try and find out if heat soak really is a problem for Coops.

Mostly the external temperature was about 20 degrees.

First I put it around various unspectacular locations in the middle of the engine bay to read the ambient temps there. At cold it was on average 20C, the same as the external temp as you would expect. When driving and up to ragging temps it was reading on average 33C. When hooning it would rise to about 40C and if stopped in traffic for a few seconds, would keep rising and rising and...! Scarey. In fact the ambient temps would not drop unless I was doing 35mph or more and would take about 2 mins or so before the temps would drop below 40C.

Then I put the sensor in the Airbox...

Interesting. Now knowing what the ambient temps were doing in the engine bay, I was expecting this to be higher than the external temps. But no. Whatever I did, the temp would stay almost exactly the same as the external temp. Even if the car had been ragged and then sat in traffic for a few minutes, within a few seconds of driving the Airbox temp would be the same as external temps (and the airbox temp never really went above 25C as long as some throttle was used, sucking air in), especially if driven at considerably more than 35mph, but still off-boost.

I have a cold air feed as well. Which I plugged this up and hoped the airbox temps would be a bit higher, but from what I could see they were the same.

Conclusion - With the standard airbox it seems that it really does suck all the cool air in from the outside and is completely unaffected by heat soak in the engine bay. And cold air feeds do jack, although mine isn't connected up as nice as it should be. I wonder if I can be bothered now!

Question - I wonder how different this is with cars that have a monster air filter and doesn't seem to suck air in directed straight from the front of the car?

I have a cone filter in the std. airbox position and when it was fitted the garage did some tests and reported that it was getting lots of cool air in this position and as a result they felt it wasn't worth placing it in the "riskier" SMIC position (although obviously this gives you a straight run to the turbo).

I've got 4 temperature sensors.

A. Ambient (behind right fog lamp)
B. Chargecooler coolant
C. After FMIC
D. After chargecooler

If the A is 15deg, B is 17 deg, C is 20 and D is around 18/19. Pootling around town the temps go up a little so maxium inlet temp (even after chargecooler) is around 27. C never gets that high, maybe 25 max.

If I'm booting it however C rises steadily, however D actually starts to get lower! until they cross over at which D stays constant and C keeps going up.

I haven't had chance to do any really good testing yet. I wanna try some 1/4 mile with the same starting temps and monitor C/D.

Chris

Edited: I've also noticed that the sensor behing the C/C is actually quite prone to heat soak. Remember the thermostat is just below the inlet and the throttle also has a coolant jacket around it to prevent icing in the winter month. I've since removed this and diverted coolant straight back to the expansion tank

There's always someone who brags about being better equipped!

See, I was going to stick a sensor in the piping, somewhere after the SMIC and before the Inlet manifold, but resisted against this for fear of it being sucked off in the airflow! Sucked off.. tee hee ...anyway, so what probes... er, I mean what sensors do you use? Did you just wedge the wiring in the piping?

It's all interesting results though. I had no idea that the engine bay temps get so high, yet the airbox is so unaffected.

Your car must fly with those charge temps!

I use the maplins temperature sensors, with maplins display, box etc...

My sensors are mounted inside pipe adapters (the blue type that connect oil/fuel braided lines in motorsport). I've then got aluminium hose joiners (between Samco hoses) with a threaded hole, and the adapter screws into this. It keeps sealed and there's no danger of sensors falling off and getting sucked in/out.

Here's my original display unit - Mk1

Thought that was a bit bulky so I compacted it all into a new display - here's the thread from it - Mk2

Chris

I use the same Maplins sensor, with one probe just after the airfilter and another one just before the throttle body.

My findings were very much like Welformed's - once moving, there is very little difference between air intake temps and ambient.

However, heatsoak is a definite issue when you've been sitting in traffic for a while, especially with a chargecooler (which can become a charge-heater). Chargetemps at the throttle body take a while longer to drop once the car is moving.

Also of interest is the length of time it can take for the temps to drop - even after parking overnight, I can still see temps of over 20 degrees in the morning until I start the engine and suck cold air through

Nobby - do you fire your CC fans off the Maplins display unit?

I'd thought about activating an IC water spray using a setting on the display unit, but I rarely see more than 30 degrees when driving, even at 1.5 bar, so I can't be bothered.

Interesting. With traffic becoming a problem and how fast the engine bay heats up, it seems that maybe CC may not be the best mod? Certainly not one that can be used at short notice.

I take it you have an exposed A/F?

Chris that first one wouldnt look out of place on a Russian space station

Well done for monitoring at different points , very interesting findings.

Nigel - no I've got a manual switch. There were far too many cables inside the box already. Plus the connector I used only has 8 pins and all are used for the 4 sensors input

Simlarly lots of the connectors aren't rated that highly so that rules out the switch as a power feed (I've used a switch plus relay anyway now, negates the high feed problem)

Kevin - LOL. <Yuri_Gagarin>Moscov we have problem, chaarje temperachuresss are high....

Welformed - yep. Straigt induction pipe plus K&N

Well done! It seems Fiat engineers were no boneheads after all.. (lots of people seems to think so..)