I'm a little curious about the process of tuning using an EGT. Namely is the process just maintaining specific temperature? If the temperature starts to decrease lean out the fuel, if the temperature increases beyond the norm richen the mixture? Is there anything specific to tuning using an EGT for the FC?

How close can you put the EGT sensor to the rotor housings (Min. Distance if you have a custom manifold)? Should more than one EGT be used to determine individual fuel mixture on each rotor? How does timing work with the EGT?

Sorry for the amount of questions, but any direction would be greatly appreaciated.

 

by the time you figure out your running lean you gonna need a new engine why in the world would someone tune a car based just on the egt if you want to tune your own car get a wideband.....

 

Most people use EGT's to help tune their timing, not just their fuel-mixture. You can have good AFR's, but if you're timing is too advanced (putting you in detonation danger), you would need the EGT gauge to help you see the increase in temps... An EGT gauge is highly recommended if going to a full standalone EMS because you'll have to set your own timing-map.

Serious people monitor the EGT's for the individual rotors, but that's pretty advanced stuff. One is all you'll need. Numbers will vary based on placement, so I'm not sure of a good "general idea" to give you... I'm sure someone else will chime-in who has personal EGT tuning experience.

 

If you don't know what you're talking about, then don't say anything at all.


-Ted

 

Looks like the entire forum should be closed then. lol

 

i do know what im talking about the OP is trying to learn about tuning and wants to just use a EGT which is a bad idea because it is very hit and miss on trying to get the right AFR and on a rotary that could end up in bad news...it would be a lot eaiser for him to use a wideband to tune and use the EGT as a secondary meter to check on if its run lean or not...
usually i see n/a guys put two sensors on their header and turbo guys put one on their downpipe...
then eriksseven explained the rest of the stuff....

 

That is the standard selling pitch from the wideband O2 vendors. While I guess it is true in the case of a novice, advanced internal combustion engine tuning for power is performed via EGT, or even better on the dyno. The O2 sensor is actually designed for tuning for economy and emissions.

This article is rather dated, but gives you the basic idea for tuning via trends, which also happens to be the proper way to tune with an O2 sensor:
http://www.rhinoracing.com/yaw/carb_tuning.htm

 

Although I haven't done any tuning, I still see people who are not lacking in experience using EGT's to tune their cars. I want to know how they tune with it and why they do. I figured the questions I asked were specific enough to help me get a fundamental understanding of the process.

Just because everyone wants to use WideBands doesn't mean it's the only, nor the best way. I like to see others philosophies when it comes to cars so I can take what I like and add to my knowledge base. Is that not allowed?

Evil Aviator, thanks for the link. I just read about the tuning. Is there more to tuning with the EGT than posted there? That link answered a few of my questions and I imagine that there's more. How do you alter the timing using an EGT or is that impossible?

 

Sure its allowed. Thats what keeps this advancment of knowlegde. BUT, it looks like your trying to tune a car solely on the measurement of the exhaust gas. I don't know of an EGT gauge that will move faster than a wideband. Get a wideband and save yourself some money.

I have dual EGT's and I call them overkill for my HP goals. But they helped diagnose a funny idle very well for me once before. I chipped a tiny spot in an apex seal and immediatly the front rotor EGT fell about 400 degrees lower than the rear rotor. Motor was quickly set down and rebuilt with nearly zero damage to the internals. All that from a difference in EGT's. Without them, the only noticeable difference was a slightly lumpier idle. Car still boosted 12lbs and power was still very smooth with the chipped apex seal.

 

I don't have any of those gauges yet. I don't even have a stand alone yet. This is for when I do get it though. I was curious on what the use of the EGT was for since I couldn't see any practical use for it. While reading around the forums I noticed that certain people tuned with them. I was curious about how and why they did, but no thread was made for it, so I made this one. But enough with my explinations for making this thread.

So would you recommend using two independent EGT's to measure the front and rear... how close are the probes to the housings since the article linked by evil aviator said about 24" would be ideal. Could you only fit them on N/A headers or would you be able to fit them on a custom turbo manifold?

 

the EGT probes are universal all you need to do is weld a bung onto your header/downpipe and it screws right in

 

The info is out there if you look for it.
Try do a search on "egt" - there should be lots of hits; start reading them.


I can't find my original post, but this thread has a reference to what I said before...
https://www.rx7club.com/single-turbo-rx-7s-23/what-does-high-egt-mean-432997/


-Ted

 

I'm not talking about the probes universality. I'm talking about the distance from the rotor housings. If I were to do a dual EGT setup (according to the link posted by evil aviator) the ideal location is 24" away. I know of no turbo setup that has 24" of space in the manifold to attach a probe prior to the turbo. I'm just wondering how detremental it would be to place the probes closer to the rotor housing.

Thanks Ted for the link. That answered alot of my questions about tuning with it. There was one question that didn't get answered though and I think I might like some insight on it if possible:

 

thats the question i answered for you...the directions that come with the EGT should tell you how far away you should put it i think its around 6" from the port and about the 10-2 position.

 

EGT's use thermocouples.
These are designed to take really high heat.
So you want them as close to the exhaust port possible.
Don't worry about them "burning up" - this is next to impossible.

They do NOT like debris being thrown at them though...
That tends to split the stainless steel casing and kill the sensor instantly.

I would highly suggest you install an EGT gauge before you start to heavily mod the car.
This way, you get a very good idea of what the EGT's should look like under all driving conditions.
Then, apply those conditions when you do go heavy mods (especially the standalone EMS).


-Ted

 

That 24" might be where the wideband should be mounted.

I have my dual Autometer EGT's mounted about 1" from the exhaust port in a stock divided manifold. Also with these gauges and sensors, there is no bung to install. Just drill and tap the manifold. Don't forget the anti-seize.

 

https://www.rx7club.com/3rd-generation-specific-1993-2002-16/dual-digital-egts-612960/

one of the FD guys uses two thermocouples and a device to convert them to an analog signal which can be logged by an engine management system. This will react more quickly and accurately than just an in-cabin gauge and will allow advanced tuning. I may run this setup at some point.

 

arghx: I guess my biggest worry about them is still that the actual "heat" takes "some time" to heat the thermocoupler. No matter how fast the signal from the thermocoupler to the PFC is, the signal could be a fraction of a second slower, which might be perfectly acceptable for our (RX-7 folk) purposes.

 

dude most commonly used engine management systems use absolutely ancient processors and have a slow sample rate anyway. And they communicate with a serial connection over 9600 baud, which was fast in... 1991. Or you may have a laptop which is running a bit slow for whatever reason and can't process the data very fast. What I'm saying is, there are lots of limitations on how responsive and precise your datalogging can be, and I wouldn't worry about the thermocouples being the limiting factor.

My power FC sample rate is about .125-.130 seconds after looking through some logs. I think the aforementioned factors are limiting me more than the responsiveness of my sensors themselves.

 

my thormal couple is about 3" from my downpipe (turbo).

Once I go dual EGT, They'll be about 3" from the ports. I think the dual EGT setup is HUGE. It's almost a must have for tuning a rotary. Like mentioned above, you can REALLY see what's going on with your motor. Even dual wideband wont tell you as much as dual EGT.

EGT isn't great for initial tuning, it's a GREAT way to maxamize power tho!!

 

My EGT probes are like 1" from the exhaust ports on my engine, no issues with probes melting/dying..........................................yet

 

"K" type probes are used on your common GE F-110 and PW F100 or the JFS used on the F-16. It all depends what your reading the probes with. Just an old analog gauge......sleepy slow. Digital readout, plenty fast.

"K"type probes is what you use on automobiles also. Alumel and chromel wires. Handle a Fluke 52 II sometime and see how fast a thermocouple can be read.

Zeitronix has a wideband controller that can also read EGT. I connected the probes off a old analog gauge (Sold by Pegasus Racing. Westberg was the mfg) to the Zeitronix, and the difference in speed is the difference b/t day and night.

Zeitronix also sells the "K"type probes for the exhaust.

 

Your absolutely correct. I guess I'm basing this "slowness" of the thermocouplers on the fact that when the car is cold, it takes about a second to begin registering anything on the probes. My car idles around 1000F and it will take well more than 10 seconds to get to that point. This is all when the car has been sitting and is completely cold, which could be totally irrelevent to the discussion.

I wonder:
If there was a means of comparing a thermocouplers signal to an internal infared heat sensor, maybe on a graph of y=temp and x=time, what would the graph show. I would hope that the max temp would be the same on both, and I'm hoping (for the sake of my position on the discussion (: ) that there would be a difference in the lines.

But this is all laboratory testing, beyond any of my goals.

 

I wanted to share a couple of pictures with the forum. Both pics are of a recent motor. The rear rotor experienced a crack lenghtwise on one apex seal, and a small piece of the "new upper half" of the apex seal broke loose.

Pic #1 is at ~1100 rpm idle.

Pic #2 is at ~3000 rpm, no load.

These pics show that there is some merit to having dual egts, as only one egt here would show a smaller difference in combined temps. As seperated temps, you can easily see there is a problem with the rear rotor.

This is off topic of whether or not to tune with an EGT, but worth sharing.