Egt probe in downpipe?

[Tony Hanna]

I've got an egt guage and thermocouple that's been laying in my glovebox forever. The original plan was to pull the head to install a ported exhaust manifold, new turbo, new headgasket, and new timing belt all at once. I was planning to install the thermocouple in the ported manifold before it went back together. Unfortunately things are going a little slower than I'd originally planned and it's got me wondering would it be worthwhile to go ahead and install the thermocouple in the downpipe for now?
I can always move it to the manifold and weld the hole up in the downpipe when I finally get around to pulling the head. I know the guage will read colder than what it would if the thermocouple was mounted in the manifold but could it still be useful for tuning mounted like that? Also, does anybody have an idea of how to correct the temp reading for being downstream of the turbo?
Thanks,
Tony

[Frank]

Some EGT is better then none. EGT in down pipe means your high limit is around 1300. Downside to this location is the fact that they are slower to respond, but do take into account all cylinders.

[Tony Hanna]

Frank,
That's exactly what I needed to know.:)
Thanks

[Rattlesnake]

I got mine on the DP right after the turbo and my EGT temp. always agree with my wideband.

Reinaldo Moloon

[Tony Hanna]

I got mine on the DP right after the turbo and my EGT temp. always agree with my wideband.

Reinaldo Moloon

That's nice to know.:thumb: I won't be running a wideband on mine at least for now, so I'm stuck with a narrowband a/f meter and an egt in the downpipe. Mostly I was curious about the high limit which Frank said is 1300. Another nice thing would be to know what a safe normal range would be. I'm going to be pushing around 18 psi worth of hot air out of the stock Mitsu until I pull it apart to swap turbos plus I have no idea how well the intercooler I'm going to use will perform. Taking that into consideration, I imagine the egt gauge will be a big help avoiding any engine damage.
Thanks,
Tony

[Rattlesnake]

When I didn't have the wideband I had the EGT probe on the DP, where I have it right now. My goal was 1300-1400 with the Dawes A/F meter on blue, anything lower or higher than that I could feel the car slightly loosing power.

Reinaldo Moloon

[Tony Hanna]

Thanks man. I'll probably tune for a little below 1300 to stay safe. Since this is my daily driver, I'd rather sacrifice a little power in favor of keeping the engine healthy.
Hopefully this will only be temporary. I'm really looking forward to a bigger turbo and methanol injection so I can run some decent boost. Hopefully by that point I'll have the extra cash to drop on a wideband.

[Rattlesnake]

Hey man, are you near Summit Point Raceway? I'll be there in the summer.

[Tony Hanna]

I'm kind of in the middle of the state. It looks like Summit Point is in the eastern panhandle. About 319 miles according to mapquest. Still, it might make for a fun roadtrip...

[WVRampage]

I was reading the instructions online about how to hook up the EGT and it says on a turbo engine it needs to go after the turbo,any explanation of this.

[Tony Hanna]

The idea is to put it in the exhaust runner for the hottest cylinder because it's likely to be the first to melt down if you go lean. With it reading the hottest cylinder, you know if you keep that one at a safe temp then the rest will also be at safe temps. That is if everything is functioning properly. If you mount it after the turbo like I'm going to do, theoretically you could go lean enough to damage the hot cylinder while the gauge is still telling you that you're safe. That's the way I understand it, somebody please correct me if I'm wrong.
In my case, with the engine together it'd be next to impossible to install a clamp style probe into the manifold runner, so I'm going to put it after the turbo and then move it when I pull the head to swap turbos.

[Frank]

They say after a turbo to help reduce the number of stupid trouble calls of people saying, they didnt detect any lean conditions because they were monitoring just one cylinder instead of all.


Frank

[Frank]

I would target 1200 as max if you are putting it in the downpipe. Keeps longevity up of things like the valves, etc.

[Tony Hanna]

Thanks again Frank.
1200 it is then.
Was I about right on the reason for running the probe in the runner for the hottest cylinder?
If I had the unlimited budget, I think I'd go for one of those digital aircraft egt's that can monitor 4 probes at once. I looked at one awhile back that you could set to either display the temp of 1 cylinder, cycle through all the cylinders, or automatically display the hottest cylinder. It even had a warning light that you could set to come on if any of the cylinders went over a certain temperature. That would be really handy to point out an injector that's on it's way out hopefully before it causes any damage.:thumb:
I'll dig around and see if I can find a link for the thing. I think they were selling on ebay.

[Tony Hanna]

Found it.
4cyl aircraft egt (http://cgi.ebay.com/ebaymotors/Aircraft-4-Cylinder-EGT-Probes-TSOd-STCd_W0QQcmdZViewItemQQcategoryZ26436QQihZ014QQite mZ330072496678QQrdZ1QQsspagenameZWDVW)
I'd really like to have one of these but I just can't justify installing a $435 gauge in a $200 car.:D

[Frank]

I have one and I am not confident that it is working properly. I need to call them up and find out what the deuce is going on.

[Rattlesnake]

Just make sure you put it as close to the turbo as possible. The further down on the DP the cooler is going to read.

[Mario]

If you're using a Wideband is an EGT still necessary?

[Tony Hanna]

I have one and I am not confident that it is working properly. I need to call them up and find out what the deuce is going on.
Frank,
How's it acting to make you think it's not working properly? For all my grousing about the price of the thing being more than twice what I paid for my car, I probably will still buy one eventually. You can bet if the Sundance finds a new home, the gauge will be kept to be put in the next TM that comes along though. So, yeah, I'd be really interested to hear what kind of problems you are having with it.

Rattlesnake,
I was planning to put it as high in the downpipe as possiable without interfering with the flange for just that reason.:)

Mario,
I guess if nothing else, it would be handy to have both because you could check them against each other. Your WB is going to give you en exact idea of your a/f ratio, and the EGT should be pretty close. If the two don't agree with each other then you know something screwy is going on.

[BARRON]

What about putting the probe in the swingvalve..just above the O2 sensor??

[Frank]

Frank,
How's it acting to make you think it's not working properly? For all my grousing about the price of the thing being more than twice what I paid for my car, I probably will still buy one eventually. You can bet if the Sundance finds a new home, the gauge will be kept to be put in the next TM that comes along though. So, yeah, I'd be really interested to hear what kind of problems you are having with it.

Rattlesnake,
I was planning to put it as high in the downpipe as possiable without interfering with the flange for just that reason.:)

Mario,
I guess if nothing else, it would be handy to have both because you could check them against each other. Your WB is going to give you en exact idea of your a/f ratio, and the EGT should be pretty close. If the two don't agree with each other then you know something screwy is going on.

I can only get cyl #2 to show valid data. All other cylinders go band edged... aka off scale. My 2 probe meter reads good for the other cylinders when I hook to those. I havent had the chance to call them. It could be a calibration issue. I am using one of those terminal screw strips from RadioShack to mate the probes to the wiring.


Frank

[Tony Hanna]

That's interesting. I read the pdf installation manual for the one from the auction and they make it out like the gauge is almost infallable with a second processor checking the first one and the first one checking the second one and the whole thing shutting down if something goes wrong. Have you tried doing anything like switching the wiring between cylinder 1 and 2 to see if you get valid data with the gauge set on 1? That would probably point to or rule out the gauge itself as the problem.
Just a thought,
Tony

[Frank]

Whatever I hook to cylinder #2 input typically works once I started using a terminal strip for a reliable connection.

Frank

[Tony Hanna]

So do you just have the terminal strip on the wiring for cyl2 at this point or all of them?
If you've got them all connected like that and have switched them around and still can only get the gauge to work on the cyl2 setting then yeah, sounds like time for a phone call.
I'm just guessing here, but I would imagine that dealing with aircraft instruments they probably have pretty good customer service. It stands to reason that if they have enough failures they could get a certification pulled or something, so I'd imagine they'd be pretty eager to make things right. Hopefully...
Tony

[Frank]

That is pretty much it. I just havent had the car running long enough to really dive into it with them over the phone.


Frank

[Tony Hanna]

Gotcha.
Well, good luck with it, and let us know how it turns out. I for one am really curious to see how good of a job that thing does when it's working right.:)

[puppet]

Maybe mount it in the collector.
Wasn't it mentioned by David Zelkowski that the temps in the collector were pretty close to being right on?

[Tony Hanna]

Thanks, but I'll probably just throw it in the downpipe right below the flange for now.
Hopefully I'll be moving it to the manifold soon.

[Dave]

I'm looking into an EGT as it's been suggested that it's a neccassary tool for tuning in compliment of a WB. You're WB readings can still be, not really wrong, but misleading in short.

I like Barron's idea. Could I drill and tap into the SV? If it's that close to the turbo, Frank, is 1,200* F still the max point? I just can't justify pulling the head to pull the exhaust manifold to install the probe. I have to wait until Aaron builds me my intake to pull the head again. I also like the idea of monitoring all cylinders instead of just one.

But the SV is thicker than the downpipe. The downpipe is stainless steel and the SV feels like... iron? Can you still run a tap into iron material? Never tried it myself.

While we're at it, can someone explain really why you need both an EGT and a WB? So far I'm just educated on afterburn.

[Tony Hanna]

I can't say for sure about in the swingvalve, but with the thermocouple mounted a little below the flange in the downpipe, the hottest I've seen has been about 1275. That was on the interstate pulling a hill at part throttle. At full throttle/boost, it seems to stay at or just below 1200.

[Mysterio]

I put my probe a couple of inches after the swingvalve on the downpipe for my EGT gauge and i've seen nothing over 1200*. Maybe slightly over but nothing that was noticeable. 1200 seems to be where it peaks at and then it cools back down relatively quickly once I let off the gas.

[Mike_Shepard]

This is a great topic to be reading as I have had a new Pyro gauge waiting to be installed and now that the top end is apart what better time than now huh.

I have been reading this and it seems alot of you guys are using different locations which has me wondering exactly where I should put mine. Originally it was going in the manifold but now im thinking other places.

Or hmmm maybe send it back and get a WB with the credit and some extra cash

[Tony Hanna]

This is a great topic to be reading as I have had a new Pyro gauge waiting to be installed and now that the top end is apart what better time than now huh.

I have been reading this and it seems alot of you guys are using different locations which has me wondering exactly where I should put mine. Originally it was going in the manifold but now im thinking other places.

Or hmmm maybe send it back and get a WB with the credit and some extra cash

I'd definately put it in the manifold if you've already got your top end apart. The only reason I didn't is that I installed it with the head on the engine. Mine's getting moved to the manifold when the head comes off to swap turbos.

[Dave]

This is a great topic to be reading as I have had a new Pyro gauge waiting to be installed and now that the top end is apart what better time than now huh.

I have been reading this and it seems alot of you guys are using different locations which has me wondering exactly where I should put mine. Originally it was going in the manifold but now im thinking other places.

Or hmmm maybe send it back and get a WB with the credit and some extra cash

Buy both. :thumb: I may not know exactly why you need the both of them, but I do know you need them... both.

[Mike_Shepard]

haha I have this pretty NB sitting in front of me and I'll probly just use it for the time being

[Dave]

haha I have this pretty NB sitting in front of me and I'll probly just use it for the time being

Well in my opinion those NB A/F gauges are just for looks. My dad and brother both have blown apart cast pistons (3 times on both of them) with their NB A/F gauges showing fat rich.

[puppet]

N/B isn't totally useless. It'll tell you when your lean ;) I take it that your Pa and Bro didn't have another way to tell them that they were running hot? ... (EGT)

The EGT will be helpful for you Bryan because it'll show you how the fuel is being distributed within the engine. In an ideal world we'd have four of those probes, monitoring each cylinder. Then, heat variances between the four can be tracked real easy. Like I said before, an absolute, ideal A/F ratio doesn't exist ... as it pertains to different engines. Each one will require a bit more or a bit less depending on quite a few differing factors. This is where the EGT monitor comes into play. It'll help you fine tune your A/F ratio. All you have to know is what heat range your engine likes and then try to keep it there.

I like the idea of keeping the probes before the turbo because ... at least for me ... it's good to know how hot the exhaust is before it enters the turbine section. Over fueling (EGT's reading too hot or too cool), ignition timing too retarded (EGT's reading hot), advanced ignition timing (EGT's reading cooler), detonation effects (EGT's reading way to cool), etc are pretty transparent here. We also know our equipment at this location is heat sensitive.

If you know your engine well enough, like RattleSnake does, then his choice of location doesn't factor in to his data. Other people here may take that temperature info to heart and assume that they should also be seeing those types of temperatures there as well. I'm real sure that turbo exhaust housing differences will have some impact on DP temperatures. Up or down, that housing will have an effect on heat absorption and dissipation. Resulting temps will be different accordingly. This aside ... you would have changed the EGT monitors most important role .. monitoring fuel distribution .. and relegated its status to a glorified exhaust pipe temperature gauge. That's just more useless info.

[Dave]

N/B isn't totally useless. It'll tell you when your lean ;) I take it that your Pa and Bro didn't have another way to tell them that they were running hot? ... (EGT)

The EGT will be helpful for you Bryan because it'll show you how the fuel is being distributed within the engine. In an ideal world we'd have four of those probes, monitoring each cylinder. Then, heat variances between the four can be tracked real easy. Like I said before, an absolute, ideal A/F ratio doesn't exist ... as it pertains to different engines. Each one will require a bit more or a bit less depending on quite a few differing factors. This is where the EGT monitor comes into play. It'll help you fine tune your A/F ratio. All you have to know is what heat range your engine likes and then try to keep it there.

I like the idea of keeping the probes before the turbo because ... at least for me ... it's good to know how hot the exhaust is before it enters the turbine section. Over fueling (EGT's reading too hot or too cool), ignition timing too retarded (EGT's reading hot), advanced ignition timing (EGT's reading cooler), detonation effects (EGT's reading way to cool), etc are pretty transparent here. We also know our equipment at this location is heat sensitive.

If you know your engine well enough, like RattleSnake does, then his choice of location doesn't factor in to his data. Other people here may take that temperature info to heart and assume that they should also be seeing those types of temperatures there as well. I'm real sure that turbo exhaust housing differences will have some impact on DP temperatures. Up or down, that housing will have an effect on heat absorption and dissipation. Resulting temps will be different accordingly. This aside ... you would have changed the EGT monitors most important role .. monitoring fuel distribution .. and relegated its status to a glorified exhaust pipe temperature gauge. That's just more useless info.

Very nicely put and I actually understood it... I think. ;) With that said, in your opinion where is the best place stick the probe? Probe meaning single...

[puppet]

I've got mine near #4. Most fellas have stated that placement over the years. Works for me. The collector section of our log mani might be a good spot too.

[Mike_Shepard]

Very nicely put puppet.