Tuesday, March 10, 2015

VE, spark and EGT, I think I got it...

Hey,

I started notice that my EGT while cruising is alarmingly high.

I could get up to 950C/1750F+, at first I thought the EGT is off (it does have a bad ground and the needle jumps around sometimes)

One drive when I was cruising @ 100kph/60mph~ I saw the EGT is very high, for every little gas pedal moment the EGT would raise even more...

It was dark, I pulled over and opened the hood, the exhaust manifold and the turbo turbine were glowing red like I never saw it !

Investigation begins...

Many reading days later, conclusions:

- Higher BTDC degree = Less EGT = Less power
- AFR lower or higher then 14.7 = Less EGT

My ignition map when EGT was too high:



The marked area is my cruise cells.




I added spark to the cruise area like so:



The EGT dropped by as much as 300C/570F~ !!
Of course the power in the area dropped too.

I'm ultra happy with my little win :)

Now I need to find the right balance between EGT and powa.

***UPDATE***

Beside the ignition map update I did something else that I didn't thought is responsible for the big change in EGT - I was wrong...

As I wrote:
- AFR lower or higher then 14.7 = Less EGT, max EGT @ 14.7

I changed my afr map - that is incorporated into ve table, so every change I make in the afr table should bring the afr to the value present.

High EGT AFR Table:




Keep in mind that my wideband could be off a little... still checking.

Low EGT AFR Table:




As  I wrote:
(real) 14.7 will get the highest EGT, lower or higher AFR should get lower EGT, so...

15.4 got me very high EGT, 14.7 gave very cool EGT, I think my wideband is a little off.
Could be my 15.4 is closer to real 14.7 and my 14.7 is lower then real 14.7.

I need to find a way to check that.

Anyway the AFR change made the big difference in EGT.

Change it and you will see the difference in no time.

:)

*****In the new post about mileage EGT and AFR I sort things out - please check it out.*****




7 comments:

  1. Can you fix the pic links?

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  2. Are you sure you are not too far advanced already? Generally when you increase advance, you will get more power.... unless you are already past MBT, then power will drop with increased advance.

    How exactly are you measuring power?

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    Replies
    1. My first concern was EGT, advancing spark more kept EGT much lower - that is for sure, about power - I think I lost power - not sure.

      Delete
  3. Remember, EGT is maximum at 14.7; stoichiometric and falls either side of it.

    How are you measuring power?

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  4. I am curious as to what you are using to measure EGT. What gauge/sensor are you using and where did you mount it? Thanks

    ReplyDelete
  5. I use an autometer EGT mounted about an inch from the head on the manifold.

    BTW I have new info about EGT at cruise - will post tomorrow. (40deg cruise with lean afr !)

    ReplyDelete