exhaust temp help

buzzinhalfdozen · 04-05-2011, 03:36 PM

No arguing that Tom with properly working wide band o2's fuel management is greatly simplified. If for nothing less than the increased response time they are a worth while addition to any tuning arsenal. The biggest issue I've seen is racers searching for that "magic AFR" basically there isn't one. Joe

Chris Hill · 04-05-2011, 05:50 PM

Some other things for EGT from a pure theory standpoint.

Compression goes up, EGT goes down
If starting rich, leaning the A/F ratio will increase EGT, it will peak at stochiometric, then decrease as it gets leaner still
Advancing spark timing increases EGT till ????? (sorry, having a brain fart and can't remember)
EGR (including internal EGR) will decrease EGT
Detonation causes EGT to decrease? (I think this is correct)
Volumetric efficiency causes EGT to ???? (can't remember this also)

EGT trends with peak cylinder temperatures and thus NOx emmisions.

marvstrick · 04-05-2011, 08:04 PM

engine builder said to get ried off msd timing retard . i am running 40 degrees . when looking at timing with alterator on above 4000 rpm timing keeps going.

Ed Wright · 04-06-2011, 10:16 AM

Quote:

Originally Posted by buzzinhalfdozen

No arguing that Tom with properly working wide band o2's fuel management is greatly simplified. If for nothing less than the increased response time they are a worth while addition to any tuning arsenal. The biggest issue I've seen is racers searching for that "magic AFR" basically there isn't one. Joe

Ain't that the truth? Kids come in for tuning read on internet message boards that 13-1 is the magic number, and that is what they want. Heck, 13.5-1 will often make big dyno numbers, seldom goes down the track as quick. Depends on the engine and fuel of course, but there is no magic number. Mine likes mid-twelves. (Air/Fuel ratio, not EGTs)

Mike Taylor 3601 · 04-06-2011, 12:40 PM

I think EGT's can be alot like dyno's numbers vary I'd say you would have to find your spot on jetting for fastest,quickest,then use that # your EGT shows to be your reference.
I've not had any in car EGT's but on engine dyno on gas around 1375 was close to best temp alky was around 1200.
I had engines where EGT would be 900-1000 move jetting,timing never get to change,so would have to jet by power&torque to find best jetting,those engines were always better than average of comparable engine I had dynoed and had wider and flatter power&torque curves. On those engines when you pull headers they would be black about 2-3'' down tube then go to nice toasty tan.
EGT thermocouples are'nt the most consistent thing,they go bad they change,you can buy thermocouple tester that checks accuracy of thermocouple.
Where you put in header tube makes a difference I think Superflow told us to go about 3'' out from head.
I think most people put probe in #5 in BBC it seems to be hot cyl on BBC.
Usaully on dyno adv.timing would drop EGT,ret. would raiseEGT.
Mike Taylor 3601

04-05-2011, 03:36 PM	#1
buzzinhalfdozen Senior Member Join Date: Sep 2006 Location: Bellevue Ohio Posts: 984 Likes: 0 Liked 11 Times in 8 Posts	Re: exhaust temp help No arguing that Tom with properly working wide band o2's fuel management is greatly simplified. If for nothing less than the increased response time they are a worth while addition to any tuning arsenal. The biggest issue I've seen is racers searching for that "magic AFR" basically there isn't one. Joe __________________ Joe Buchanan SS/BX 3117

04-05-2011, 05:50 PM	#2
Chris Hill Senior Member Join Date: Jan 2002 Posts: 655 Likes: 8 Liked 244 Times in 26 Posts	Re: exhaust temp help Some other things for EGT from a pure theory standpoint. Compression goes up, EGT goes down If starting rich, leaning the A/F ratio will increase EGT, it will peak at stochiometric, then decrease as it gets leaner still Advancing spark timing increases EGT till ????? (sorry, having a brain fart and can't remember) EGR (including internal EGR) will decrease EGT Detonation causes EGT to decrease? (I think this is correct) Volumetric efficiency causes EGT to ???? (can't remember this also) EGT trends with peak cylinder temperatures and thus NOx emmisions. __________________ Chris Hill https://ihmusedparts.com

04-05-2011, 08:04 PM	#3
marvstrick Member Join Date: Jan 2008 Posts: 153 Likes: 161 Liked 33 Times in 10 Posts	Re: exhaust temp help engine builder said to get ried off msd timing retard . i am running 40 degrees . when looking at timing with alterator on above 4000 rpm timing keeps going.

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04-06-2011, 12:40 PM	#5
Mike Taylor 3601 VIP Member Join Date: Oct 2008 Location: Somerset,Ky Posts: 1,371 Likes: 353 Liked 306 Times in 103 Posts	Re: exhaust temp help I think EGT's can be alot like dyno's numbers vary I'd say you would have to find your spot on jetting for fastest,quickest,then use that # your EGT shows to be your reference. I've not had any in car EGT's but on engine dyno on gas around 1375 was close to best temp alky was around 1200. I had engines where EGT would be 900-1000 move jetting,timing never get to change,so would have to jet by power&torque to find best jetting,those engines were always better than average of comparable engine I had dynoed and had wider and flatter power&torque curves. On those engines when you pull headers they would be black about 2-3'' down tube then go to nice toasty tan. EGT thermocouples are'nt the most consistent thing,they go bad they change,you can buy thermocouple tester that checks accuracy of thermocouple. Where you put in header tube makes a difference I think Superflow told us to go about 3'' out from head. I think most people put probe in #5 in BBC it seems to be hot cyl on BBC. Usaully on dyno adv.timing would drop EGT,ret. would raiseEGT. Mike Taylor 3601