I am looking to buy a boost gauge and either a A/F or EGT gauge. After talking to my salesmen at Stillen he said the A/F gauge is the poor man's EGT gauge, is this true and should I buy the EGT over the A/F? Thanks.

 

He's saying "Poor Man's" as in trying to sell you a more expensive part and make you poor. The EGT is a nice piece of gear to have, but it takes a lot longer than the A/F to register a meaningful reading. By the time you saw a "Hot" condition on your EGT, the damage would probably already be done. If you use it for everyday use, it would probably be okay, but for tuning, forget about it. I would say get an A/F guage, save a few bucks and a piece of mind first. The A/F register's a bit quicker and you can notice a lean or rich condition before a mass temp change. Good luck. just my $.02

 

Oh yeah, forgot to mention. The temp of the exaust has little to do with the air fuel ratio. Each engine runs differently. A V-6 vs. I-4 vs. V-10 will all have different exaust temps and A/F readings. It's all up to the car and mods. My basis and info for this... I work on engines that run from 370 celsuis, to 805 C, and that's just the normal operating range! Good luck again. Matt

 

Thanks for the info! I am thinking why not just buy both? They make a 3 guage mod for the max so boost + A/F + EGT will fit perfect. Now I just have to figure out what the right air to fuel ratio is and proper exaust temp is supposed to be? Hmm the Air to fuel ratio supposed to always be 50/50 or what? Tahnks again. Ohh yeah what if the air to fuel ratio is off, then what?

 

Emax95
I know what I know of jet engines, and an EGT is pretty much works exactly the same for both. I also have an A/F, which I'm waiting to install on my NOS for. I'm planning on running fuel pressure and A/F for 60-70 shot of NOS. I know your running the S/C, but the same problems and safety warnings exist. My best advice is to use the email function to contact those who have walked the line already. my4drsc? I think should have some info, and I know sx7r uses the EGT and A/F, and should be able to give you a more specific answer on the A/F guage function. You should also contact Stillen and talk to a supercharger rep and see what he recomends, not a salesman, but an actual tech. I just don't want to give you bum scoop beyond the range of my knowledge.
Good luck man, I hope to get the S/C someday, I bet it pulls like nothing else. Love your car. Matt

 

What kind of A/F gauge? Are you taking about a $50-$70 one or $300 one? There is a big difference. Cheap ones are just a light show. I have an EGT and I'm going to cross reference it with a wideband O2 sensor on a dyno.

 

Yep the cheeper A/F are not as good as an EGT.

As far as response time to temp changes goes. Mine is pretty quick. I have my probe mounted in the exhaust manifold so it gets a good reading.

The trick with an EGT and tuning is to know your base line. I get 780c max in a 1-3 n/a run, I get 800c max ian a 1-3 nitrous run. It does creep up if I lower my fuel pressure. preignition(detonation) can also show up as high EGT's

The cheep a/f gauges dont mork that well, I have one too. I trust my EGT far more than the A/F. I've had both for about a year now.

What was said above about taking it to a dyno with a wide band O2 so you can match the EGT to the wide band readings is the way to do it.

 

Thanks for the info mardigrasmax, going with the gas soon myself.

 

In my opinion the ONLY real way to tune your car and get the proper air/fuel ratio is on a dyno with a WIDEBAND O2 sensor.

The EGT gauge can be a useful tool but is quite expensive at over $200 compare to a $40-60 AFR gauge.
Neither of these 2 gauges will yield completely accurate and useful tuning info.
I chose to simply go with the cheap AFR gauge because it WILL tell you if you are running dangerously lean.
It may not be the most accurate thing...but if you are running SERIOUSLY rich or lean...it will let you know.
It should only be used as a general reference and not as a tuning device....leave that to the dyno.

 

"meaningful reading" ??

That's BS dude. The A/F is worthless. It can show full lean but by that time, the car could've detonated and burnt a few pistons, valves, and anything else in the way!

The EGT is far superior over the A/F mixture gauge since it shows a gradual reading. You can see how the exhaust gas temps respond with an actual temp reading; with the A/F mixture, it's just an LED bar indicating a rough approximation.

Ever wonder why most of the modified Zs, Supras, and RX7s use EGT gauges rather than A/F mixture gauges.... ?

 

I have two EGTs on my Z.
just know what temperature to look for because, yes, every car is different.