VEMS Home Products Documentation Wiki Webstore
WikiHome ProjectPage DocsPage UnderDevelopment MembersPage SiteIndex RecentChanges Preferences
ExhaustGasTemp (2007-05-30 01:08:58)

For EGT measurement one can use a K type or E type thermocouple.

The new VEMS-speed K-thermocouple unifies the advantages of extreme durability (5mm body, very strong even if pushed well into a large exhaust), and very fast operation:

EGT_VEMS_speed_m.jpg

Will be in WebShop soon (66.6 EUR), available again at appr 2006-11-19 (first batch was sold immediately, a merchant purchased all).

It is posible to order custom size sensor / fitting (eg. if you already have a thread in the turbine housing), just write it in the order note. Consider that custom size might take upto 3..4 weeks (without shipping), so order in advance.

The traditional K-thermocouple:

Note that the fitting is often just welded into the exhaust (fast) instead of cutting a female thread into the exhaust (tough). The sensor is removable in any case, of course. Specify in order note if you have special fitting-preference.

The 120mm long sensor looks like this:

egt_short_640_480.jpg

[[Manual: Detailed.Sensor.Exhaust.Install]]

Also available in WebShop:

For the curious

There are 2 issues to measure Temperature with a thermocouple:

GenBoard/VerThree has amplifiers for EGT inputs:

[[Manual: Detailed.Sensor.Exhaust.Install]]

Thermocouple connector

Connector pair available in WebShop:

The male is compatible for wire-to-wire and case-mount. The green and yellow are EU and USA standard colors for the same (K-thermocouple).

Don't reverse the colors of contacting wires, as that will result in measurement error. The polarity is marked on the male and female connectors. Also, the + and - contacts of the male connector are of different width:

Alternatively, the cables can also be connected by terminal strips, or other means. Make sure you don't have long copper wire in the path, because temperature difference between the 2 ends of such non-compensated connection show up as measurement error.

Target EGT temperatures:

The exhaust parts start melting at around 899C (1650F). There is a web page on the Avweb site where a guy goes into a lot of detail about EGT and CHT temps, with color charts and graphs 8-). Bear in mind that the engines he refers to are mostly redlined at 2700 rpm. The rest of the information is equally valid for airplane and auto engines.

AI Nut

Some people claimed he targets 732C(1350F) EGT (at max power), others try 816C(1500F) for short time. The warning from Bill: Of course without knowing EGT at stoich, this number is fairly, if not totally meaningless when carried over to a different engine.

The wisdom from Dennis:

The answer to this question is a function of engine design and operating requirements.
For drag racing, you can peak out at 1600-1750 deg F for short periods.
We run durability engine tests (6500rpm, full load for 300 hours) at numbers at or around 1500 deg F.
If you have to protect a catalytic converter, you tend to run richer at high rpm and leaner at low rpm - each OEM has differenct criteria on that regard and nobody talks about what they do - for obvious reasons, I can't either.
Basically, some engines can run at 1500 and others at 1600 with no ill effects. It really depends on whether the basic engine design will be sensitive to high EGT's or not.
I know of an engine that runs at 1500 and has no issues whatsoever and another that experiences seat distortion/valve problems at same EGT & load conditions.
Also, the point on the rpm scale where peak EGT occurs is a factor. Pretty much any engine should endure a peak EGT of 1500 at peak torque - you could probably creep up to 1650 at peak power.
I won't go into the fuel situation as gas versus alcohol versus "nitro" creates a whole new set of circumstances.
Valve size plays a factor. Figure out the heat absorbtion area of a 1.910" head diameter exhaust versus a 22mm head diameter on a 4V engine and you can see that the AMOUNT of head absorbed can play a bigger factor that the temp level of the surrounding gasses.
Although M/S makes pretty sure you have equal fuel, manifolds don't always have equal air distribution. Thus, if you pick the wrong hole to measure, you could have a "great EGT" but still burn parts. How lucky do you feel that you picke the wright hole to judge the whole program by???
Point being: Asking "what is a safe EGT???" is like asking "what's the price of a tire???" The answer depends upon what you're trying to do and for how long and whether you're using the proper perspective for judgement.
Sorry to bother you but since I'm no longer registered at M/S, maybe you could pass this empiricle wisdom on.....

Dennis

Some gathered rumors and facts from Jörgen Karlsson.

Exhaust temperature is pretty useless for tuning the fuel delivery on a car but I would never tune a car without it as it show when it's time to step away from the ideal fuel delivery to cool the engine.
I also find it useful for tuning the ignition timing, if the exhaust temperature drop when you add some timing it's a good indication that you went in the right direction.
One thing that should be noted is that you exhaust temperature drop when the mixtures go weaker then lambda=1.1 (AFR=16.2:1) or so. Also worth noting is that knock is most likely to occur between lambda=1.05 and lambda=0.85. You definitely want to stay away from the entire window if you are boosting a fragile engine. I have heard that many modern engines tend to knock the most at around lambda=0.9, this is also where they produce the most power.
A few of my friends work at Volvos test and development facility here in Gothenburg. The guys from the lab that I know tend to tune their own turbo cars so that they never exceed 1000C for more then a minute at a time! And their engines stay together most of the time.
A note taken from an internal Audi education program is that they added a temp sensor on the 2.7l biturbo so that they would not have to resort to tune the car to 950C to maintain a safety margin. By using the temp sensor they can enrich the mixture when they actually go higher then 1000C. Volvo did the same thing on the 16v turbo in the early nineties.
Note that the engines I have been talking about all have good oil sprayed pistons, sodium filled valves and turbos with an extended temperature range.
The old Audi fivepots that I used to play around with often pulled exhaust studs or cracked their manifolds when going higher then 800C for a few minutes. I had it pegged at well over 1100C for two minutes without hurting anything. I was impressed that I could cruise at 210km/h without going into the boosted range, I forgot to check the EGT!

As a pole some engines melt pistons and valves at 800C.

Jörgen

note for HW-developer's

Some instrutions on 100-1000X amplification (translated sloppily):

  1. Low offsetet and drift OPA (suggesting chopper balanced??, like: ICL7650, or low noise ICL7652....)
  2. OPA inputs guard-ed by ground, see applications notes and datasheets of above
  3. At high amplification rate use low TK resistors, since temperature dependence will distort (0.1% TK-25ppm, Elektrade Ltd in HUN)
  4. In feedback branch connect a C 220nF...2.2uF parallel with the R. (Makes it slower, but problematic without) (polypropilen - mylar? - or teflon type is the best)
  5. Use S/D ADconverter (most are applicable to small signals like this)
Ciao,
HG

[[Manual: Detailed.Sensor.Exhaust.Install]]

Links

Pentronics therocouple document (good info):

http://www.pentronic.se/eng/katalog/pdf/3/3_1-10.pdf

Earoelectric - Thermocouple temperature measurement document (good info):

http://www.aeroelectric.com/articles/excerpt.pdf

Pyromation - Temperature Transmitter Products datasheet:

http://www.pyromation.com/lit/ad03.pdf

Here is a standalone thermocouple instrument, and will give temperatures upto 1000degC from a K-Type thermocouple.

http://www.squirrelpf.com/msavr/files/data-1.pdf

Its RS catalog number is: 260-167 They cost 50.57 each (ouch, almost as much as a genboard v3.1 with some discount).

EGT-probe at http://www.teamrip.com/accessories.html

1/8NPT -27 thread, there are stainless bungs available too..Looks like the probe is something around 50mm, thread included..

Any suggestions on a sensor? WebShop

Can the sensor wire be bought and welded? It's tough. There are connectors for EGT (where exactly?)

New standard is sensors with longer, 2.5m cable. If the sensor cable cannot reach the AD597AR, I'd rather move the cold junction than attaching several EGT cables.

See also