???? about EGT an A/F ratio..

[RUQWKNF27]

EGT is its high means what?? I presume rich.
A/F ratio?? same thing??

I know all combo's are different. But is there a general sweet spot as far as A/F ratio without putting th ecar on Dyno to findout??

I think i may have Alzheimer cause one day I can remember theses simple things an the next I am a damn retard ...............................

[Dennis F]

To high of an EGT means a couple things to me.

1. Your running to lean
2. your knocking real bad, pulling timing. That can cause high EGT's as well since timing is firing much later in the cycle.

[turbo2nr]

You can be pig rich and have high EGTs because the combustion is still going on thru the exhaust. Or you could also have high EGTs because of a super lean condition. The o2 sensor (wide band) should point you in the right direction. Use both! An EGT by itself is not much good. Just My opinion.

[Razor]

EGT=Exhuast gas TEMPERATURE.

The Higher the temp.. the leaner the car is.

[turbo2nr]

That's not always true. You can run rich with not enough timing and still have crazy high EGTs/

[Razor]

On a properly tuned car it is.

On an improperly tuned car.. anything is possible.

Just like if you set your WOT timing to 15 degree's.. you'll hit 2000 degree's.

PLUS.. the higher the timing, the lower the EGT.

As above stated it is used to see where your tuneup is not to see air fuel ratio. As knock, timing, cylinder pressure, intake temp, etc all play a role on EGT.

[turbo2nr]

Well, somebody give this guy a A/F number to shoot for.


I'll say 11.5:1-12.5:1 at WOT. Depends on how hard you are running, and fuel.


Do you have a wide band 02, or are you just looking at the Micky-Mouse stock narrow band sensor? I think you should be aiming for mid .700s with that, but it's not very accurate.

[Razor]

Originally Posted by turbo2nr

Well, somebody give this guy a A/F number to shoot for.


I'll say 11.5:1-12.5:1 at WOT. Depends on how hard you are running, and fuel.

Not true hehe.. 11.0-11.2:1 at WOT as a starting point. 12.5 will break some parts.

On a low timing high boost app.. low 700's on race gas. On pump gas high 700's. Pump gas alcohol 770-780's top of third using a 22 degree chip

EGT= 1500-1700 depending on timing

[Ormand]

The problem with A/F ratio is that you have to have the leanest cylinders in a SAFE condition. So, that means that the overall A/F ration will much lower than if you could have all cylinders at the exact same conditions. 11 to 1, even 12 to 1 is richer than you would want for max power. There was an interview with Jim Bell a few years ago when he recommended 13.5 to 1 for max power. (Jim Bell of Kenne-Bell, for those who don't know) Jim cited tests on Bill Middaugh's GN, when it got to 501 hp, with stock ignition timing, a stock MAF, 113 octane fuel, and 27 lbs boost- and running at 13-to-1. The advantage to the richer A/F ratio is that it's more tolerant of fuel that's too low in octane, and it protects the lean cylinders.
Flame temp is max at 14.7 to 1 (stoichiometric) and goes down with richer or leaner mixtures. EGT will be different, depending on timing and mixture, since the gasses in the exhaust may at some temp other than the flame temp.

[Dusty Bradford]

Originally Posted by Razor

Not true hehe.. 11.0-11.2:1 at WOT as a starting point. 12.5 will break some parts.

On a low timing high boost app.. low 700's on race gas. On pump gas high 700's. Pump gas alcohol 770-780's top of third using a 22 degree chip

EGT= 1500-1700 depending on timing

Also not entirely true


11.3 is safe at 30# of boost on these motors. 11.5 still safe but I'd rather run a little richer.

12.5 is safe at 15# of boost

Chris, 13.5 is lean....10.5 is rich

Like was said. EGT could read 1800 and be lean or way rich. If you're too rich the unburned fuel ignites in the header and runs EGT's up. On a well tuned car an EGT of 1600 is richer than a reading of 1700. After I started using an a/f reading I wish I would have done it years ago, it's the best way to go.

[Razor]

Originally Posted by Dusty Bradford

Also not entirely true


11.3 is safe at 30# of boost on these motors.

What do you mean.. I thought everyone ran 30#

[Dusty Bradford]

Originally Posted by Razor

What do you mean.. I thought everyone ran 30#

I remember making a pass on 30# and thinking...Damn I lost 3# of boost somewhere

[Razor]

Originally Posted by Dusty Bradford

I remember making a pass on 30# and thinking...Damn I lost 3# of boost somewhere

On that Autometer 30 PSI guage you have 1st screw and 2nd screw. That 2nd screw is a doozy

[Dusty Bradford]

Originally Posted by Razor

On that Autometer 30 PSI guage you have 1st screw and 2nd screw. That 2nd screw is a doozy

Ha, we're too much alike. I brought mine into work and checked it against a calibration instrument. I marked the gauge with white out at 30, 33, and 35#. 35 was around that second screw but my car slowed down there. I lost mph there so went back to 33#

I was suprised how far off the reading was at 30# on my gauge. 30# was really 27. We also have a VDO in a friend's car. 30# was really 24 No wonder it wasn't running like it should.

[evil666]

Is my car tune tuned ok?

23 LBS BOOST WITH TURBO TWEAK CHIP WITH 23 DEGREE TIMING 1ST AND 2ND AND 21 THIRD AND FOURTH.

O KR
A/F=11.7-11.5 AT 5300 RPM
EGT=1690
O2=770-780
LAMBDA=.80
94 OCTANE AND ALKY (95% ETHANOL)
Thanks, Marco.

86 Grand National t-top (60300km)
stock long block,stock suspension, red stripe convertor, te44, smc alk injection, 24lbs boost, 94 octane, hooker cat back with dyno max ultra flow muffers, tomco 30lbs injectors, dynotech stage 4 street chip, thdp, mease 24 row IC, Ron Custom max boost brake module, MT drag radials (275/50/15) 3800lbs race weight with driver. (Torque convertor not locked)
.New set up: 42 ½ 009 injectors, turbotweak alky chip, rjc power plate, rjc boost controller, and will lock the torque convertor, zeitronix wideband, HR motor mounts, comp cam 980 valve springs, the rest is the same, will be going to the track this fall with new set up.
BEST E/T
60FT=1.52
1/8= 7.38
I/4= 11.74
MPH=113
BEST MPH= 114

[Dusty Bradford]

evil666 I'd say yes.

[Pronto]

What is the best location for the A/F and EGT probes? Does the A/F one go where the O2 sensor goes? What if your using the stock ECM? Over winter I would like to get some more tools to help tune better. I feel like I'm just shooting in the dark with a Scanmaster.

[RUQWKNF27]

I do not have a Broad Band yet. I am thinking of the Innovative LM1 Kit for the car.. I already have a EGT. I was just wondering a starting point when I get one..

[Dusty Bradford]

Egt usually goes in the header right before the flange for the turbo.

The Wide Band needs to be at least 12 inches from the turbo in the downpipe, we normally shoot for around 18. That put's it close to the a/c box on the T/R's. You also want to mount it on the top side of the pipe so moisture won't settle out in the sensor.