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Thread: Exhaust Gas Temperature....

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    Exhaust Gas Temperature....

    After repairing my car, I want to try and avoid anymore serious problems so I am on a gauge spending spree.... i've got: Boost, Oil Pressure, Oil Temp.... and now I am thinking about going for EGT.....

    Do you think this would be a good way of avoiding/noticing detonation, while knowing how the engine is running on full boost??

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    Guest P1 Racing's Avatar
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    Ideally you want afr and egt. But you'll also need something to adjust fuelling if you are detonating, such as a programmable ecu or safc etc.

    If you just want to monitor det, Jez has just starting selling electronic knock sensors.

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    Ahh nice....

    I was wondering if there was anything to interface with my alpine headunit?? I think I may drop Jez a PM.


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    EGT is definitely worth monitoring

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    jez also sell the vems egt and wideband afr gauge. its a nice bit of kit just got one myself

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    Guest ByReaL's Avatar
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    what will be good EGT values for:

    standard internals short bursts or long hi speed driving
    forged internals short bursts or hi speed driving

    or other engine load points and RPM and a good EGT

    ?

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    Guest Damo's Avatar
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    im not sure about good values, i try to keep them below 950 deg

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    Guest ByReaL's Avatar
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    Quote Originally Posted by damo_s13 View Post
    im not sure about good values, i try to keep them below 950 deg

    sustained (for long time) 950'C like in circuit racing or short burst like in drag racing ?

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    Guest Damo's Avatar
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    sustained, normal track stuff. i dont really see over about 750 on the road short burst stuff

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    Just had a look at the VEMs unit Jez is supplying... very nice indeed, but I think I am going to have to save the pennies for it. Also, I would like to know if I could interface it with my Alpine head unit before I went ahead with it.

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    Guest Damo's Avatar
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    i dont think you can do anything like that with a head unit...

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    Guest ByReaL's Avatar
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    Quote Originally Posted by damo_s13 View Post
    sustained, normal track stuff. i dont really see over about 750 on the road short burst stuff

    so at what EGT point standard / forged pistons start to melt or engine take damage?



    where you measure EGT? (where the EGT probe is placed)
    i placed mine just before the turbo in the exhaust manifold

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    Guest Damo's Avatar
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    Quote Originally Posted by ByReaL View Post
    so at what EGT point standard / forged pistons start to melt or engine take damage?



    where you measure EGT? (where the EGT probe is placed)
    i placed mine just before the turbo in the exhaust manifold
    mine is placed in the same place as yours,

    its hard to say at what egt things start to melt as the egt is not the piston temp as you have oil cooling it etc

    i think anything over 1000 deg is not good and from what i have read most tuners try to keep egt's below 950 deg

    im sure some one will post with better info.

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    I saw OVER 1300 celcius (melted a 1300 degree probe) and did not melt pistons. Very interested to see what my exhaust valves look like though.

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    Steel often melts at around 1370 degrees C (2500F).

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    Aluminium melts around 660degC.
    The reason the pistons aren't melting at EGTs of over that level is because the pistons only see that sort of temperature very briefly, then get cool air on the inlet charge, and also the combustion process gives up very little to the cylinder. You'll notice that we also have oil squirters to cool the piston and water jackets to sink the heat away.

    So if you see sustained EGTs over 900degC you know that you're going to be possibly damaging your engine, more than likely by heat soaking the oil and coolant if you keep it up. Bursts of EGTs over 1300degC aren't necessarily catastrophic but aren't particularly good for the valves or the turbine wheel. Your piston crown may not be seeing that temp though as EGT rises as a result of retarding the ignition.

    Personally I regard monitoring Lambda and EGT as every bit as important as measuring oil and water temps, it common to monitor the latter but its only recently that the former have been easy and cheap enough to monitor.
    You can see well before the oil heats up that the EGTs are rising, and issues with fuel pump pressure, blocked injectors or bad fuel control are shown in the Lambda reading.

    Its when you get to tuning and upping your boost that the Lambda and EGTs come into their own, obviously the fuel bit is clear, you adjust your fuel map and see how the changes have effected things.

    The nice bit is when you're going for absolute power, as you up your boost, increase fuelling and notice that the EGT starts to rise, pulling ignition out will cause EGT to climb, but you need to do it to avoid detonation, so then you start to use fuel to cool the temperatures, the Lambda tells you how much you're going past peak torque fueling you've gone, and the EGT shows the effect that the fuel is having - it takes the guesswork out of things. BTW thats not how you tune a car, but its a scenario that illustrates the combined useage.

    The VEMS Wideband & EGT gauges are available from (in Alphabetical order): Apex, APT, Driftworks, H-Dev as well as a number of places that aren't traders on here.

    Maff is working on an awesome program that uses the gauge's datalogging facility and overlays the Lambda and EGT over the Nissan MAP that you load in. I think its still in alpha but he'll be able to tell us more.

    Rob

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    anything more on this overlaying of nissan map? Maff?

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    Yup its up and working, on the live map trace the RPM scale is 100% the AFM is just about right call it Beta

    http://kardiak.co.uk/downloads.php

    Next step is getting it working with a Moates Ostrich for live mapping, but ive been lazy recently, if you need any help or a keyfile add me on msn and we'll sort summit out.

    maff667 AT gmail DOT com

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    Quote Originally Posted by #1 Adam View Post
    After repairing my car, I want to try and avoid anymore serious problems so I am on a gauge spending spree.... i've got: Boost, Oil Pressure, Oil Temp.... and now I am thinking about going for EGT.....

    Do you think this would be a good way of avoiding/noticing detonation, while knowing how the engine is running on full boost??
    using EGT for detonation monitoring is very difficult and probably dangerous. Detonations lower EGT, this is very important fact, also timing and AFR affect EGT in different way. You can monitor EGT very carefully, hold it in good health range and smile and your engine can detonating to death. Use EGT as only overall temperature monitoring, not for detonation detection, it is very very hard.

    Use good detonation detection and be focusing on AFR. Use EGT only as overall monitor that you are in acceptable range.

    try to start here for example:

    http://www.foxvalleykart.com/egt.html
    Last edited by raddy; 06-05-2008 at 16:12.

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    Interest read.

    Thanks for clearing that up, raddy. I wasn't aware that det lowers EGT's.


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