Don1

My motor is a 13B. I did the street port myself and it is run only on the track. At full chat on the track at 145 mph and 7500 rpm I am seeing a/f of 12.5 but my egt can go over 1900 degrees F. My understanding, when I ran the same motor before my porting in a Formula Mazda, was that I should aim for an egt of 1675 which would indicate the best mixture.



It seems to me that if my a/f is ok the egt should not be that high.



I have several concerns:

What should the egt be?

How high is too high? What will fail if I get the egt too high?

If I need to get the egt down, should I just keep putting in richer main jets, or, am I missing something?



My setup now is: Weber 51 IDA (Racing Beat) with 45mm chokes, F11 emul., 70F10, 220 main fuel, 160 air.



Any advice would be appreciated. Thanks.

j9fd3s

[does his best lynn hannover impression]



everything affects egt, timing mixture, outside air temp, oil and water temps.



most obvious thing, would be to richen it up, the extra fuel will help cool things down.



you might wanna look at timing, its prolly pretty optimum...



intake temps? oil temps? water temps?

Don1

Timing - 10 degrees leading and trailing. Should I advance or retard?

Outside air - 80 degrees

Oil and water temp - 200 degrees

Intake gets good outside air. My guess would be about 90 degrees

j9fd3s

unless its a P-port, that tining looks a little retarded. more normal to see people in the 22-24BTDC L range. i would try 15btdc for a lap, and see where that gets ya

turborotor

Mike is right, 10 is very retarded, the will cause the fuel to ignite longer in the exhaust.

Don1

Thanks guys. I relied on my memory for the timing instead of looking it up. It is set to 22 degrees. Sorry for the misinformation.

mazdaspeed7

If I read that correctly, you are running zero split, leading and trailing firing at the same time. If so, that can raise the EGT's.

Don1

In a Formula Mazda the leading and trailing timing is the same. It never caused high egt before.

1Revvin7

only way I've ever seen that high is timing as mentioned...

Don1

Thanks. I agree. BUT, I have been offered an explanation that hadn't occurred to me. If you run TOO rich, there is the possibility that you could have burning fuel, that didn't get burned in the motor, going through the exhaust port and creating an excessively high egt. It was suggested to me to consider that possibility when a/f to egt relationship doesn't make sense otherwise.



All I can do to test that theory is to wait for an opportunity to get on the track and lean this sucker down to see what happens. Racing Beat suggested using 240 fuel and 110 air. It seems to me that my current setup, 220 main and 160 air, should not be that much too rich.



I checked the timing an hour ago and it is correct.