AchillesGr

iTrader: (1)

hi,
i have my engine disasembled and fiting an A-spec 3574 kit.
i receive a manifold and a downpipe from a-spec and i wondeer if i need to install two or one egt probes.

yes, the best is pre turbo , but should i use one, or two probes? is there a realy need for two? is there a variation in temps that i should monitor ? before my a-spec kit i had a single turbo setup and ONE probe located at the rear rotor outlet pre turbo.

i have a pfc and one autometer analogue egt gauge.

options:
1)one post turbo probe
2)one pre turbo probe
3) two of them .

i am not using the car for race . i only use it on a street and my pfc programming capabilities are limited at this time.
i am thinking to use the two probes only for problem diagnose so to prevent a blown motor and not for precision tuning trying to get the most of the motor.


i apreciate any help.
thanks

hkp

iTrader: (2)

i use two but its for tuning and diagnosing problems. the way i look at it, you cant go wrong with two egt pre turbo.

arghx

iTrader: (3)

you may see 100-200 degrees F (38C-93C) difference between front and rear rotor, preturbo. This is going to depend on where you put the probe, the reaction time of the gauge, and driving conditions. I suppose you could put the gauge after the turbo, which will read a little cooler, but that's mostly going to tell you the temperature of the exhaust entering your catalytic converter if you have one.

After messing with EGT gauges for a while I have some doubts about how useful they are for aftermarket performance tuning purposes. I don't think there is always a direct relationship between the temperature of the exhaust and the likelihood of engine knock occuring. Lots of cars with EGT sensors from the factory, but they are mostly used for emissions control.

ALPSTA

iTrader: (3)

I got an A-spec manifold with two probes located pre-turbo. I guess this is the best for tuning efficiency and correct readings. However one thing my mechanic warned me about is that with pre turbo set-up over time the tip of sensor brakes and damages the turbo. So I am having second thoughts about my decision. Another thing is the cost of two egt gauges vs. one. Or you can always buy an ugly but cost effective dual display egt gauge.

I am not a tuner but my common sense tells me, the temp difference between front and rear rotor doesn't matter that much. Single egt post turbo will display an average of both and if it goes high enough to cause a warning, does it really matter which rotor it is.

If there is way to cancel the bungs on the manifold without ruining the manifold I may change to single probe post turbo, not sure yet.....

j9fd3s

iTrader: (3)

if you're going to run 1 probe, put it in the rear rotor, and since that's usually the hottest/leanest one, you should be just fine.

i kind of agree with arghx, egt is limited use, basically you just want to keep it under 1100C on the stock apex seals.

most of the stuff i've read about EGT tuning was in relation to airplane engines, and the concepts are valid, but having actually been IN (and flown) the airplane application is very different. in a plane takeoff rpm was 2500 and cruising rpm was 2400. so its basically a stationary engine. the second difference is that in the plane you are ONLY adjusting fuel, timing stays the same. the fuel adjustment also only goes from max power to max fuel economy, which is again different from the automotive use.

Speed of light

iTrader: (8)

Agreed. And with widebands so readily available, i don't really see a need for the EGT except maybe for development and/or logging max effort setups. We're really not tuning for EGT anymore and for most common and proven setups, the EGT we achieve is incidental to that setup and not particularly consequential.

The EGT was once very useful back in the day when there were no AFR gauges to be had outside of the lab. EGT thermocouples were standard on every engine dyno and used to make AFR adjustments; i.e., jetting our carbs.


I've had this happen and was fortunate not to have any turbine damage. I just pulled the EGT off and forgot about it as it wasn't worth the trouble.

oo7arkman

iTrader: (2)

Sure, very easy. They make stainless plugs that go into the EGT probe bungs. Last time I had the manifold out of my car I had two EGT probe bungs welded in and plugged them.

I put them in just in case I ever needed the option and to compare data of EGT with and without AI as well as different mixtures of water/methanol.

OP - If you are going to install them they really should be preturbo. Post turbo temps have been shown to have little usable information as the exhaust temp is variable after passing through the turbine and is not a true value of real-time EGT. Best place is as close to the exhaust ports as possible. I am not trying to plug a company and I do not have any of their products but the PLX digital gauges allow you to display both temps real time and log them.

NW Rx7

I think the pre egt is more beneficial for engines with more combustion chambers/ cylinders. Evo and wrx I'd do it but don't kno if it's necessary for rotary..

arghx

iTrader: (3)

the question isn't, "are EGT gauges useful" the question is whether they are worth the time and money for the given application, and IMO for most performance applications the answer is no.

AchillesGr

iTrader: (1)

guys,
thanks for all the replies.
i study carefuly all the above e=statements and my question is:

1)if i install two probes and i discover a diference, should i do something or is there something i can do? if ther eis nothing i can or should do and it is normal then why to monitor?
i am not talking about a case that there will be a dramaticaly large diference and that is an indication of a problem.

then:
2) if i use only one probe after turbo and there will be a problem, will the one probe show me that something is wrong?i mean, if the post turbo brobe reads the average , then if something is wrong will i see it at the reading?

3) if i use only one probe at the rear then the front will be completely unmonitired i assume.


thanks again for your input!

arghx

iTrader: (3)

There are going to be differences in EGT, just like how piston engines have differences on individual cylinders. Presumably you would want to have two probes in the event that something serious goes wrong on one rotor, so that you can spot it. But you have to be looking at it, and the gauge or whatever you are planning to use needs to respond very quickly to changes in exhaust temperature. In regular operation it's not very useful.

Now if you had an engine management system that can respond to EGT inputs you could configure it to respond to high exhaust temperatures.

Umm, maybe? Nobody here can fully agree what a "dangerous" EGT really is, either before or after the turbo. Is there a specific exhaust temperature that indicates the engine is running lean on one rotor, or an exhaust temperature that can be correlated with a high probability of engine knock? I'm sure there's an answer to that, but a Mazda engineer are probably the only ones who really know. Normally the biggest concern about high exhaust temperatures is excessive wear on the the catalytic converter and turbocharger.

Yes.

ALPSTA

iTrader: (3)

Achilles where in Greece are you? Do you work on your car or take it to a rotary specialist?

Answers:
1- Like Arghx said you may see 100-200 degrees F (38C-93C) difference between front and rear rotor so don't panic.
2- Yes if there are dramatic changes, it'll show in the gauge even if the probe is installed post turbo.
3- Yes that's correct, if you must choose one rotor then monitoring the rear one is your safest bet.

My solution is, get bungs welded on each runner of the manifold. Use them for tuning purposes and block them with bung plugs afterwards. Use and keep a permanent post turbo probe for the rest of the time unless you are constantly tuning your car or altering settings.

AchillesGr

iTrader: (1)

guys you helped a lot,
Arghx,
you are wright.since i am not a profesional and my programming capabilities are limited the two is too much . also as you said i must watch all the time the gauges and respond quickly and that is imposible and useless for me.
the main idea is to enjoy the car.



Alpsta, i am in Salonica //Greece.i work on the car on my own.i just finished my engine rebuild and last week i install the engine in the car. the kit i receive from a-spec do not have any bungs welded and your solution to weld one in each runer and then block it is the best..
do anyone knows any place to buy stainless steel bungs? from my search i found only iron bungs and not stainless steel. i do not want to weld regular steel on a stainless steel manifold.

thanks again!!

ALPSTA

iTrader: (3)

http://www.full-race.com/store/fabri...-egt-bung.html