Autometer EGT in downpipe?

[bob86gn]

The instructions say to mount the EGT after the turbo in a turbocharged application. It seems most have it mounted before the turbo. What gives? I like the after turbo location a little better but which is better?

 

[bob86gn]

ttt

 

[U1ARUNIT]

Before the turbo is the most common place.

 

[boostx]

i placed mine right before the turbo

 

[The Pro]

Mine is in the crossover, works fine there.

 

[bob86gn]

Thanks guys. Looks like everybody has it before the turbo somewhere.

 

[TurboDave]

The reason you want it in front of the turbo is because it'll receive more consistent, and meaningful readings there.

After the turbo, is less consistent because the turbo extracts heat from the exhaust stream to do work. Problem is, the amount of heat removed isn't consistent. It varies widely with load conditions, etc. The temperature drop could be 400º or more, sometimes less.

Some of use don't just use the EGT at WOT, it's also useful at cruising and light load conditions, to check mixture changes, etc. so not knowing exactly what the temp drop is at all load conditions makes that kind of tuning useless.

 

[clean86]

Mine is after the exaust housing, in the DP. And I still get the same readings as others with there's in front of the turbo.

Good Luck.

 

[The Pro]

Wow, so during a pass, your WOT EGT after the turbo is 1200???

 

[clean86]

No more like 1500, it's 1100 at 2500rom cruising.

 

[TurboDave]

Originally posted by clean86
No more like 1500, it's 1100 at 2500rom cruising.

Well, who am I to argue, because you're obviously seeing what you're seeing. It just doesn't make any sense. Or more correctly, it shouldn't be working that way. Cruising down the highway, maybe. But under any boost, the turbo is going to exrtract heat to do work. The amount varies, but in "most" cases, I've seen as much as 400º difference at 15+# of boost, and no less than 250º, depending on the turbo

 

[clean86]

Sorry to throw a wrench into your thoughts but that is what is going on. I have been racing turbo cars for a while, single 88mm turbo mustang for a 4 years. one probe per hole and one 2 inches from the turbine housing. From the data we logged egt's cooled as it moved to the housing but was reheated as it entered the exaust housing. Most high HP cars I know, 1000 + 'run a close setup to the above. Not to mention how the turbo spools is a direct reflection on the temps in the exaust housing, so I would rather know what they are as close to the exit of the housing than in front before any unburnd fuel is ignited the housing.

Just my 2 cents
hope it helps some.

 

[The Pro]

Ideally, I'd like to know the temperature of the gas as it ignites. Since we can't (practically) do that, we take EGT measurements as close to the cylinder as possible.

This has not changed in theory or practice since EGT's have been created many years ago. Aviation is a prime example of EGT use. They do NOT use it as a tuning tool to improve performance, rather, it is a rich/lean indicator and coupled with the CHT gauges, lets you know straight away if you have problems with your current mixture....

I use it as another gauge to determine what "normal" should be. EGT is *not* an effective tuning tool IMO.

 

[bob86gn]

Thanks for the responses guys. I am a little happier drilling a hole in the DP instead of before the turbo. I plan on mounting it after the turbo and see what I get. Worse comes to worse I can move it and put a sheetmetal screw in the DP.