egt probe after turbo?

dsmcurse · Sep 21, 2009

when i used a stock style evo 3 exh. manni. i had the egt probe tapped into the manni. real close to the engine on the number one runner. now that i have new turbo set up, and im so close to gettin my car runnin agin i was wondering if the difference in temp will be that great compared to my old set up? my hx40 is t4 flange not mitsu so i got a nice stainless turbo header. i cant really see my self drilling and tapping this header as it will be very hot and have to hold up the weight of the very heavy hx40. so my probe will go in by the O2 sensor after the turbo. is this inaccurate?

silvreclips · Sep 21, 2009

Yes this is fine, actually many people prefer to mount it in this location because if it melts its not going to mess up your turbine wheel. You will read about 200F lower than right out of head tho.

Rob10_99 · Sep 22, 2009

The difference from inches after the valve VS post turbine are huge, as stated 200F or more.
I would keep the EGT probe as close to the valve as possible, that's why it's there right? To see the temp of your cylinders/pistons?

1gDSM4g63 · Sep 22, 2009

You should tapped it in the first runner of the manifold.

Boostjunki84 · Sep 22, 2009

+1 for tapping the manifold. If you are going to have it, it might as well be accurate. Without doing this you would be essentially guessing anyway.

notverygood · Sep 22, 2009

I Installed my probe after the turbo and it read over 300 degrees cooler than the same probe PRE-TURBO. Seemed like it gave me a false sense of security-as aluminum melts around 1200, I wanted to make sure to be as close to the combustion chambers as possible. good luck.

dsmcurse · Sep 22, 2009

i havent seen any one tab a runner of turbo header. if anything id have to have it done where all 4 runners meet and its a collector right before the flange where the turbo bolts onto. if i drill and tap here how will it affect the integrity of the stainless header? i have seen egt's in the collector part. but have also heard horror storys of this leading to major cracking. im kinda indecisive on what i should do. any more suggestions?

vanilla gorilla · Sep 22, 2009

On my 4g64T, I used to run a pyrometer. I had my EGT probe in the first runner (farthest from the fuel pump) of my mild steel tubular header. It was right off the head, like an inch and a half from the flange. I ran it like this for a while with no problems whatsover. And no, LOL

, the probe didnt melt or break or anything....why would it? Its made to be in a hot environment. Under WOT I would see temps of around 1550, and the prettiest tipped spark plugs ever (this was all before I got a wideband). Not sure if they would be any difference in temp readings for a 4G63T.

d_hidayat2000 · Sep 25, 2009

4G63T EGT should be around 800 deg C till 825 deg C on WOT

knochgoon24 · Sep 25, 2009

Because of the laws of thermodynamics, you WILL see a lower temperature after the turbo than you would in the the runners.

The turbo just doesn't extract energy from the pressure of exhaust gases. There is also a temperature drop between the turbine inlet and outlet.

As long as you take that temperature drop into account, you should be fine.

dsm-onster · Sep 25, 2009

Why do you want to use a pyro? You're better off with EvoScan and a wideband. . . You can actually log a knock sum with EvoScan

d_hidayat2000 · Sep 26, 2009

Yup evoscan and a wideband should be good enough, if you don't run extreme AFR, just run the safe AFR like 12,5 during spool up and 10,9 under full boost
BUT
if you want to use the race gas and lean out the AFR, You'll need this EGT
the leaner the AFR (till around 12,5) = More Power = More Heat

and I'll put his EGT before the Turbo, because You can't calculate the exact temperature drop before and after the turbo on various load condition
I think Nobody want to read false EGT

Defiant · Sep 28, 2009

Pointless. Well, even more pointless than an EGT gauge, which on a street car is just another "Too Late" gauge.
Your turbo runs on heat, not pressure. It converts that heat to kinetic energy and depletes it as it spins up.

Damaging exhaust temperatures occur so quickly in a mis-tuned engine that trying to prevent them by use of a laggy gauge is like trying to steer by looking out the back window and guessing where the road went just before you crashed.

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egt probe after turbo?

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