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G4+ Thunder engine bay installation issues


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Hello. I've been running a Thunder on a build I did recently. This ECU is installed in the engine bay like shown in the attached image.

For the most part, the ECU doesn't seem to mind this at all but I did notice one glitch that would repeat consistently after some crawling through traffic. The ECU would not recognize the ignition key being turned off and would continue to idle the engine even after the key was removed. This doesn't happen when the engine bay is relatively cool. I haven't been able to identify the exact threshold past which this takes place, but I'd guess around 70*C ECU temperature.

Any ideas why this might be the case?

 

On to the second question, I plan to do something about keeping the ECU cool. While the obvious solution is to move the entire unit inside the car, that's something I'm considering as a last resort option. The current idea is to get a Thermaflect sleeve and wrap the ECU in it. That should prevent direct blasts from the radiator fan which is what seems to be sending ECU temperatures to 80*C and above. What I'm not sure about, however, is how this will affect the ECU's ability to dissipate its own generated heat. Can somebody from Link chime in to and let me know whether or not this is a good idea?

39676136_10217405720761396_4678614279052591104_o.jpg

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Looking at your pic you have replaced the dizzy and are running COP's, so there is no way the engine can "self idle" if the ECU is off. Therefore, your issue is more likely to be either A your main/ecu relay sticking on because of temp, although factory mounting for these is up under the dash rather than the engine bay, or B (more likely) you are getting some kind of back feed of power through the ECU which is allowing it to keeping it running even when the main relay feed is cut. Assuming the temperature thing is not a red herring, maybe one of the temp sensors drops to a really low resistance when hot and because of a wiring quirk, power is being drawn in through this? Have you got any sensors or solenoids being hot fed direct from the battery or are they all behind relays? Have you wired in the Main relay controls on the thunder or just connected "14v in" to an existing ECU relay-like feed on the existing car wiring?

My gut feel is that its unlikely to be ECU internal temperature, but this is a logged value so you can check. Can you post a config and log of when it fails to shut down? 

From the link help file "It is not recommended to operate the ECU at temperatures below -20 degrees C or above 70 degrees C." so as long as the internal ECU temp is reporting as <70c you should be fine. Best to confirm this before you go into work around heat shielding it. to check yourself you can just press f12 to view runtime values and its in one of the tabs.

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Thank you for your response. To your points:

13 hours ago, cj said:

Looking at your pic you have replaced the dizzy and are running COP's, so there is no way the engine can "self idle" if the ECU is off.

The engine isn't self idling. The ECU isn't powering down.

 

13 hours ago, cj said:

Therefore, your issue is more likely to be either A your main/ecu relay sticking on because of temp, although factory mounting for these is up under the dash rather than the engine bay,

It isn't a sticky relay.I triple checked, and once when this was going on, pulled the relay clean off and the ECU still wouldn't power down.

 

13 hours ago, cj said:

B (more likely) you are getting some kind of back feed of power through the ECU which is allowing it to keeping it running even when the main relay feed is cut.

Pretty much impossible because the line that goes to the ECU's ignition signal pin is the only thing aforementioned relay controls. The low power side is wired to the ignition key, and the high power side to the ECU and nothing else. When I turn off the key, everything else in the the car that is on ignition power goes dark, except the ECU. Also, when this happens, the Runtime Value for Ignition Signal remains ON.

 

13 hours ago, cj said:

Assuming the temperature thing is not a red herring, maybe one of the temp sensors drops to a really low resistance when hot and because of a wiring quirk, power is being drawn in through this? Have you got any sensors or solenoids being hot fed direct from the battery or are they all behind relays? Have you wired in the Main relay controls on the thunder or just connected "14v in" to an existing ECU relay-like feed on the existing car wiring?

I've wired up the Main Relay controls, and everything on the engine draws power from one of three relays that are controlled by the ECU's Main Relay Out. If this was something to do with flywheeling diodes, this would happen all the time. Every single time this has happened has been after a crawl through traffic.

 

13 hours ago, cj said:

My gut feel is that its unlikely to be ECU internal temperature, but this is a logged value so you can check. Can you post a config and log of when it fails to shut down?

I wasn't able to log unfortunately, but I was keeping an eye on ECU internal temperature while a friend was driving through some pretty thick traffic after a long drive. There was no headwind to evacuate the engine bay, and the radiator fan venting all the hot air inside the engine bay drove up the ECU temp to a really alarming 85*C by the time we reached home, and I rushed out and pulled the C connector to kill the engine, which is what I always do when the ECU fails to shut down.

This was the point when I decided to Thermaflect sleeve the ECU to prevent it from heating up. If that does not work, cabin mount is the only thing left to do. I really hope it doesn't come to that.

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36 minutes ago, 007 said:

the hot air inside the engine bay drove up the ECU temp to a really alarming 85*C by the time we reached home

That's a pretty key piece of the puzzle there. 

I've never engine bay mounted one, but have put them in some pretty cramped corners of cabins and the internal temps have stayed <40C so I dont think they generate enough heat on their own to cause a problem if you insulated it.

Having another look at your pics, you could get a thin sheet of alloy and bolt it between the ECU and the engine, and have the front section run 45* across to behind the headlight so it blocks radiator air, kind of like a lot of people do to shield cold air intakes. You may even be able to run a ducting tube to pick up clean air and run it into the ECU side of the alloy sheild if its still getting a little bit hot.

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6 hours ago, cj said:

Having another look at your pics, you could get a thin sheet of alloy and bolt it between the ECU and the engine, and have the front section run 45* across to behind the headlight so it blocks radiator air, kind of like a lot of people do to shield cold air intakes. You may even be able to run a ducting tube to pick up clean air and run it into the ECU side of the alloy sheild if its still getting a little bit hot.

After everything's been installed, there's hardly any room to fit even a pinky finger around the ECU. So I'll try to completely wrap it in heat reflective tape and have a tiny opening facing the firewall. I don't think a diagonal sheet will do much good once the hot air from the fan diffuses everywhere in the engine bay. Summer temps here nudge 50*C.

 

5 hours ago, Simon said:

For the ECU side they are tested up to 70C, 80C will be pushing it for sure. 

Thanks for the confirmation Simon. I must compliment you guys on this ECU. Even above 80*C, it handled itself like a champ. I had previously installed a Haltech Elite 1500 in a similar position, and that thing would start going into limp mode the moment internal temps crossed 60. I was finally forced to relocate it inside.

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  • 1 year later...

It's been a while, but the build is finally alive once again, and this time, I have concrete information.

The issue is most definitely with the ECU and not the wiring.

There are no problems below ECU temp 55*C. When the temp crosses 55, the ignition signal input (pin C2) stops registering key off, and instead reads Active. When this was happening, I even snipped the wire going to C2 clean off and probed the voltage from the ECU, and it read 3V. I left things untouched and let the ECU cool down, with C2 still snipped off and the moment the temp dropped below 55, the ignition input correctly changed to inactive and the ECU turned itself off.

 

I'd really appreciate if if someone could look into the matter and hopefully come up with a fix. This behavior doesn't look random to me, and I suspect should be reproducible in a lab.

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It could well be hardware related. As the ECU temp rises it will expand and if there is a suspect joint its likely to cause issues.

There is no firmware control around temp on the Ignition switch input 

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Thank you for the response Simon. What you say makes sense, but do you reckon that the nice and round threshold at 55C is coincidental?

I've disabled ECU Hold Power for now by using he same switched ignition output to A5 and C2.

Would it be possible for the team there to recreate the issue in the lab by putting a Thunder under a hot air blower?

I don't have another unit with me at the moment, or I'd have tested that one in the bench myself.

In case there's a suspect joint, would it be worth the effort for me to take the case off and visually inspect the board?

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Yes, get the ECU back to Link HQ in NZ for testing.  It has a lifetime warranty so you might as well take advantage of it.  They have a burn-in tester for testing the ECU's hot and cold, if that doesnt show up anything there are a few other tricks they can do such as heating and flexing the PCB while connected to the test rig.  

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