Thermocouples

[Jellybean]

why use Thermocouples in a manifold?

[Tricky-Ricky]

Thermocouples are depending on construction material, much more resistant to exhaust manifold temps, and these are usually made of inconel or similar, or are you asking why use a temperature probe in a exhaust or inlet manifold?

 

There are various types depending on application, temperature and response time, some info here.http://www.omega.co.uk/prodinfo/thermocouples.html

[Jellybean]

Thanks , yes , why use a temperature probe in a exhaust or inlet manifold

[Tricky-Ricky]

Basically to know what the intake temp is, IE how efficiently and intercooler or intake system is functioning, also most modern ECU systems will have an IAT sensor that will fine tune mixture depending on temps.

 

And in the exhaust to monitor that exhaust gas temps are not exceeding 950C, any more and the combustion temps are incorect, which can be caused by quite a few things.

[Nodalmighty]

My Ecu has a pair of K type decoders built in. It uses this info to add fuel in an attempt to reduce temps. Generally the thinner the sensor the faster the response although there are fat sensors with thin tips.

 

I use http://www.universal-thermosensors.co.uk/index.htm for all my thermocouples.

[Jellybean]

Thanks , in comparison to using Wideband sensors , why use one over the other , cost?

[Mike2JZ]

Thanks , in comparison to using Wideband sensors , why use one over the other , cost?

 

Ideally you want both a wideband and EGT sensors (1 per cylinder if you really want to go into detail checking each cylinders tuning). ECU can use both to refine it's running conditions/setup alerts/logging etc.

[Wez]

As stock a MKIV does not have an EGT or wideband fitted and are not needed for an engine to run but they are certainly nice to have if you utilize them correctly

 

If I had to pick one over the other I think it would be the wideband, but no reason not to have both installed and setup on the ECU.

[Jellybean]

Thanks

[Tricky-Ricky]

Thanks , in comparison to using Wideband sensors , why use one over the other , cost?

 

You wouldn't, as they measure completely different aspects, one is air fuel ratio, and the other temperature.

[Jellybean]

You wouldn't, as they measure completely different aspects, one is air fuel ratio, and the other temperature.

 

Not for the same purpose? If not,Why measure one over the other?

[Chris Wilson]

Manufacturers probe the actually combustion chambers (all six of them on a 6 cylinder engine), and measure combustion pressures and temperatures in real time. A cheaper way is via special spark plugs, but they are still way beyond most people's budget.

 

To have a rough idea of combustion temperatures a probe as near the valves as possible on all 6 cylinders is a cheap way to gain useful date, likewise an O2 senor in each manifold runner for seeing mixture balance.

 

But if you buy an exhaust temperature probe make *SURE* it's an Inconel one. I sell them, with the correct 1/8 BSP olive type adaptor and the correct compensated K type connectors if anyone needs one. If it's after the turbo it's a waste of time and money, it *MUST* be as near the port as possible.

[Tricky-Ricky]

Not for the same purpose? If not,Why measure one over the other?

 

Well under normal circumstances you wouldn't measure combustion temps, but pretty much all modern engine control systems use some form of AFR measurement

to control fueling as std.

However adding the wide-band aspect of AFR measurement is far more accurate and gives more of an idea of how the engine runs, but surely you already know this?

[Chris Wilson]

Not for the same purpose? If not,Why measure one over the other?

 

You can have abnormal combustion chamber temperatures with a normal AFR. Try retarding the cam timing and see what happens

[Mike2JZ]

Not for the same purpose? If not,Why measure one over the other?

 

 

Generally speaking tuning via EGT sensor isn't accurate, when used only by itself. There is a misconception that making the engine run leaner will increase the EGT temperatures exponentially, which is incorrect. So tuners will tune the ECU's parameters to reach the peak EGT temperature. But this peak usually won't match the optimal air-to-fuel ratio that the engine needs to create peak power.

 

I guess opinions on this can change, but if it were me. I would tune the engine to reach optimal AFR targets for my setup using the wideband, whilst noting EGT temperatures at said level. You could even tune the engine richer or leaner on a dyno (safely) just to see the values that the EGT sensors would return so you have a rough indication of the expected temperature range that your setup will produce under different operating conditions.

 

From there you can setup warnings and thresholds on the EGT sensors, so in the event of something going wrong that the Wideband dosen't pick up on, on a per cylinder basis. You can be notified/engine protection strategies will kick in.

 

In short, wideband is good enough for 80% of the tuning you would need. Using individual cylinder EGT's are an extra safety net for your tune, but not a requirement. Also worth noting that you will need an ECU that can handle 6 inputs from 6 EGT sensors, which not all of them can do.

[Jellybean]

Thanks , was just curious , after I saw this setup

 

https://scontent-ams3-1.xx.fbcdn.net/v/t1.0-9/15032310_10211236702852739_7511255294269147227_n.jpg?oh=f33683631c6ba4afd1d591f7f26cd73c&oe=58C4C112

[Tricky-Ricky]

Nice looking engine! yes set up to monitor EGTs on all cylinders, not really necessary, unless its pushing cam timing or compression limits, one at the collector, or at the turbo is usually good enough to alert you to combustion temp problems, as Chris said cam timing can play a big part in influencing EGTs despite correct AFRs.

[Nodalmighty]

The fact it has a torque plate suggest this is a full on drag motor and these will be for data logging rather than realtime correction