Exhaust Back Pressure Sensor

Jimster
Posts: 134
Joined: Wed Mar 19, 2008 11:06 pm
Location: Bridgend, South Wales
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Exhaust Back Pressure Sensor

Postby Jimster » Wed Apr 09, 2008 11:19 am

Is anyone recording EBP, if so, what sensor are you using? I'm trying to find one with out any luck :(

Support

Postby Support » Wed Apr 09, 2008 11:34 am

Hi Mr Jimster,

You can use one of our standard fuel/oil/boost pressure sensors:

http://www.race-technology.com/oil__fue ... _2_67.html

This is a very high quality sensor, and ideal for this application.

There are 3 things to be aware of:

1/ The exhaust is very hot(!) and the sensors maximum temperature is about 100C... so you need to mount the sensor remotely from the exhaust. When I did this some years ago, I used 10mm copper pipe and mounted the sensor on the car bulk head. Obviously the pipe needs to be long enough that the heat doesn't conduct back far enough to fry the sensor! I'm not aware of any sensors that are able to take full exhaust temperatures.

2/ The gasses in the exhaust "pulse" with each exhaust value opening, but you want to measure the average pressure - so I would recommend having an external filter. This is very simple to implement and will work better than just using the software filters in this application. If you want details of how to do this then let me know.

3/ Not a problem - just an observation. Since exhaust gas pressure (I think) is proportional to the mass flow squared.. and mass flow is proportional to RPM x engine load..... basically the pressure is very close to ambient until you are at max RPM and full throttle and then it goes up very quickly indeed!!

Hope that help?

Andy

Jimster
Posts: 134
Joined: Wed Mar 19, 2008 11:06 pm
Location: Bridgend, South Wales
Contact:

Postby Jimster » Wed Apr 09, 2008 11:39 am

Thanks andy, can you give me some more details on this external filter?

My EGT will be around 1000C how long will the sensor last on a copper pipr 300mm long?

Also what kind of back pressue am I going to see, before the turbo running around 25 psi boost

faraday
Posts: 267
Joined: Sun Feb 25, 2007 1:18 am

Postby faraday » Wed Apr 09, 2008 2:49 pm

Don't mind a bit of boost!

Don't be surprised if the back-pressure rises above boost pressure!

Sometimes this "cross-over" event coincides with peak torque. Matching and wastegate size will have some effect, but if things are as they used to be (my last turbo experience was over twenty years ago), you'll see high pressures much sooner than you might expect.

Modern compressors might be more efficient, which will lower charge and exhaust temperature for a given power output, but you don't get 25 psi boost for free.

:)


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