Monitoring CHT and EGT - Page 4

ohecht · 04-29-2003, 06:24 PM

I know when I had to chase the treads in my O2 sensor (which looks like a "bung" welded on by the PO), it took a regular spark plug tap (18 or 19mm, I can't remember)

I was told there were air injector fittings near the heads that could be used for EGT probes, but I could not see any on mine.

I was going to look into the "hose-clamp" probes that only require a drilled hole, but I need to get details on the right sizing.

Olivier

RoninLB · 04-29-2003, 07:59 PM

" spark plug tap (18 or 19mm, I can't remember)"
--- confirmed, thanks..

"air injector fittings near the heads"
--- Yep.. I got 'em.. and the more I learn about using this machine the more interesting it gets.. but a basic seems to be 1in from the head for the probe. and JPI install says 2-4in.. and I bring it up the JPI tech on what I figured was a basic.. so he says hesidently " yes that's correct, but we figure the lifespan of the probe at 1400deg.. which is 600-1,000 hrs.. but on your EGT situation , it isn't an issue".. and I figure 1,000 is 50k miles.. and a quick eyeball of the SSI says about 1.5in for ease of use.. cool

" I was going to look into the "hose-clamp" probes that only require a drilled hole, but I need to get details on the right sizing."
--- the install is kinda idiot proof.. I will do some kind of EGT probe harnsss shield/protection/still thinking.. maybe that header wrap.

Olivier/Ron

RoninLB · 04-29-2003, 08:15 PM

Quote:

Originally posted by ohecht

That is my sticking point for now, with my luck I am almost certain to break an exhaust stud.
Olivier

bring it to a shop for new studs.. what can it possibly cost

RoninLB · 07-02-2003, 04:49 PM

Quote:

Originally posted by dwightp
.

Ron:
Keep us updated on your fittment. In aviation and I knew about these units but hadn't heard of anyone using for aircooled auto application. Looking forward to hearing more....

well got it working last nite and did a ride.. I'm a bit overwhelmed on using this unit.. so many options, and re-setting the alarms from aircraft routine to 911 routine.. but so far so good.. it reads CHT/EGT within 2 deg.. and it also has a voltage alarm, that I didn't know about.. so far on the CIS I have a difference of about 90deg from the max EGT cyl to the nearest one.. and I'm running pretty high EGTs.. even though I have the CO over smog specs..

ohecht · 07-02-2003, 07:12 PM

That looks great. I would probably do the same when I have another reason to pull my exhaust. I ended up just using a J-type CHT sensor on each spark plug, with a dual CHT gauge and 3-position switch, so I can monitor all the cylinders in pairs.

So far, the highest temperature after fairly normal driving has been just below 300 degrees, with very little variation among the cylinders. Once I get the aftermarket cruise working (I was sick of messing with the stock setup), I will clean up the wiring and finish connecting the A/F mixture gauge and trans temperature gauge.

Olivier

jyl · jyl's Garage

Very cool! Can you post a pic of the display as mounted in your car?

Doug Zielke · 07-02-2003, 07:57 PM

Ron sez:
"I'm running pretty high EGTs.. even though I have the CO over smog specs.."

Very interesting, Ron.
Remember the thread from a aircraft engine expert, where he discussed how the leaning of the mixture doesn't always mean a higher EGT?

I'm looking forward to seeing your EGT/CHT readings as you experiment with the new carbs.

RoninLB · 07-02-2003, 08:51 PM

Quote:

Originally posted by ohecht

with a dual CHT gauge and 3-position switch,
just below 300 degrees,
I will clean up the wiring and finish connecting the A/F mixture gauge and trans temperature gauge.

I think you go a great package.. very cool... nothing better than a nice/personalized 911, IMHO..

I had to take the ground seriously on this one..
the 50 page oper. man. stressed about 4 times to only use the engine ground. not even mentioned once what would happen if you used chassis ground. the lunar module had a computer ground problem one week before takeoff to the moon. if it wasn't fixed it wouldn't fly/true story.. it's common knowledge among older LI NY aircraft manf. electrical engineers. so this JPI-700 6C is a computer.. but the quality is suitable for long term marine applications/perfect .. so I'm figuring that I have to take seriously anything that goes to engine ground.. how about finding a fault in two computer systems, ignition&heat, because both computers HAD to use engine ground, LOL

300deg...
now I'm doing around 225-236deg at 5-15mi stretches at 32-36k rpm.. give or take a couple of deg.. LOL
so your really not making that much more HP than me.. and those were my summer road rpms&heat .. I won't drive low rpms in metro NY/BS.. only thing over stock is full great exhaust & Fan.

BUT. the dual bargraph doesn't come on for me.
[the long top is EGT.. and the very short is CHT.. in the same column] / [good reason why only 3 max CHT segments].. because my CHT is so low.. the CHT bargraph doesn't come on till 300deg.. LOL.
so your on the lower edge of similar aircraft eng readings.. readings that mean anything.

I got this on the console.. which will be fine/I think.. because the only real driving info I'll need is the alarms/generally speaking.. I think the present gauge system allows the clock& AC vent to fine tune everything to a nice package...

great entertainment/gotta love it............. Ron

RoninLB · 07-02-2003, 09:27 PM

Quote:

Originally posted by Doug Zielke
Ron sez:
"I'm running pretty high EGTs.. even though I have the CO over smog specs.."

Very interesting, Ron.
Remember the thread from a aircraft engine expert, where he discussed how the leaning of the mixture doesn't always mean a higher EGT?

I'm looking forward to seeing your EGT/CHT readings as you experiment with the new carbs.

yeaahh right.. I been doing the ignition routine to find a pattern.. so far nothing changes.. wow. fuel mix. now I remember. more tweaking.. cool..

in the beginnings 1st 1hr I was concerned.. then it hit me that I've been running the exhaust heat by watching the spark plugs historically.. which have always been fine in the stock CIS.. but I gotta lower the mix ASAP/at least for info.. it has historically run like crap with the stock mix.
but my perception was for lower EGT.. gotta see the carb exhaust #s for comparsion.. maybe they'll be a noticable difference in life of the pistons? maybe CIS sucks?

I gotta start doing a log for all these numbers.. or it'll get lost in outer space.. accurate to within 2deg./gotta love it
............. Ron

RoninLB · 07-02-2003, 09:46 PM

Quote:

Originally posted by jyl

Very cool!

Can you post a pic of the display as mounted in your car?

really really very cool.. thanks.
it's been the only thing hanging in the console plate.. because I got the JPI running as soon as possible. LOL.. so it needs another 2 hours then the pic with a redundant volt meter.. but it's a stock gauge dia.. so maybe I flip it for another gauge..
real soon for the pic.

ohecht · 07:52 AM

Here are some shots of the gauges installed. They are visible form the driver's seat, but there is some glare due to the angle towards the passenger window.

The CHT (in the console with a 3-position switch to see either of the three "pairs" of cylinders) and trans temp (middle) don't use much of the avilable range (unless I am really pushing it or develop some sort of problem). The top gauge is a VDO volt gauge, the rest are from Westach.

The A/F gauge (bottom) is acting strange, but I think I may have a bad O2 sensor, even though it is new. It only reads anything when the car is either under load or at high RPMs. The sensor is not putting out any voltage at idle. Has anyone had this sort of problem? Are there sensors that operate at lower temperatures? Should I put in a heated sensor to get more consistent readings? It seems that the exhaust may be too cool to get a good reading except at high RPMS or under load.

Olivier

ohecht · 07-07-2003, 03:33 AM

Here are some shots of the gauges installed. They are visible form the driver's seat, but there is some glare due to the angle towards the passenger window.

The CHT (in the console with a 3-position switch to see either of the three "pairs" of cylinders) and trans temp (middle) don't use much of the avilable range (unless I am really pushing it or develop some sort of problem). The top gauge is a VDO volt gauge, the rest are from Westach.

The A/F gauge (bottom) is acting strange, but I think I may have a bad O2 sensor, even though it is new. It only reads anything when the car is either under load or at high RPMs. The sensor is not putting out any voltage at idle. Has anyone had this sort of problem? Are there sensors that operate at lower temperatures? Should I put in a heated sensor to get more consistent readings? It seems that the exhaust may be too cool to get a good reading except at high RPMS or under load.

Olivier

ohecht · 07-07-2003, 06:20 AM

What kind of readings should I look for in the A/F gauge? I have read that it will only be accurate at close to WOT, otherwise it will be fluctuating. Right now, it seems to gradually move towards full rich during sustained open throttle runs.

The highest temp reading I get on the trans temp gauge is about 125F after a 5-10 minute drive at around 45mph and in 3rd gear on a 95F day.

Does that sound normal? I'm sure the temperatures would go higher during longer drives and on the track.

So far, all the cylinders are amost the identical temperature at around 275F during regular in-town driving.

Olivier

Olivier

tbitz · 07-07-2003, 06:47 AM

If your O2 sensor is not heated (one or two wires) it won't read properly at idle. The sensor needs to be upto temperature to operate. Also note that the NB (narrow band) O2 sensors only tells you if you are rich or lean. Don't try and read any accurate air fuel ratio numbers from it. They are just not designed for that. To read accurate air fuel ratios you need a WB (wide band) O2 sensor.

Also most of the passive thermocouple guages (like what you show above) are calibrated to be accurate at one ambient temperature. Above and below this ambient temperate they will be off by the difference in ambient temp. For example 30 degress higher ambient from calibration will read 30 LESS than true CHT.

ohecht · 07-07-2003, 08:33 AM

TOny,

The CHT thermocouples are calibrated to 75F. I am hoping that is close to the temperature near the transmission when the car is in motion, but there are not a lot of places under the car that stay that cool and I could not get the "cold sides" of the connections into the passenger compartment (it gets hot in there, too). I am looking for relative readings between cylinders at best, though, so I should be OK since all the connections are in the same position under the car.

Do you know where I can get a wide-band sensor for this application?

I have used the O2 sensor to set the mixture before, through the test plug using a dwell and duty cycle meter checking the frequency valve. I understand how the narrow band sensors are exponentially unaccurate as you go away from the stoich ratio, but wouldn't it be ok for this use assuming you are getting 50% duty cycle from the frequency valve (which I would assume means you are near the idle mixture)

I would love a part number on the wide band sensor, since I leave it disconnected from the K-Jet system and only really use it for setting the mixture and now the gauge.

Thanks,

Olivier

tbitz · 07-07-2003, 09:33 AM

NB O2 is good for tuning to stoic ratio. If the voltage is quickly swinging above and below 0.5volts then you can assume you are at stoic. If it is constantly above 0.5v then you are rich, if it is constantly below 0.5v you are lean.

Wide band O2 sensors require a special controller. I have purchased a DIY kit from the link below and have it running on my 911SC. I picked up the WB O2 sensor from the Honda deal. Part numbers are available from the links below:

http://www.diy-wb.com/

http://www.techedge.com.au/

RoninLB · 07-07-2003, 09:41 AM

Oliver.. Aircraft Spruce has a great catalog for A/F gauges, etc... and I think the CHT will come into play at the track.. or driving thru deserts, or on mountain roads.. you'll see the oil temp rise , but it kinda makes you wonder what's happening.. but you'll also see that your CHT will be OK/maybe.. then you'll have a clearer idea what's happening to oil heat affecting the engine.. but the heads-up that the CHT gives, before oil temp. gauge reacts, is priceless.. and ibitz's info is local knowledge to CHT guys. it's good he mentioned it.. it should be in the quickly glanced at instructions..

www.aircraft-spruce.com

tbitz · 07-07-2003, 11:00 AM

Olivier,

To fix your problem, you can buy some thermocouple wire to extend the junction just behind the guage. Make sure you know what wire you are using, probably K-type.

I recall looking for at a 25ft reel from www.omega.com for about $25.

ohecht · 07-07-2003, 01:25 PM

Tony,

My CHT leads are J-type, but I will look for extensions. I will also check out the WB part numbers at that link and check mine again.

Thanks,

Olivier

ohecht · 07-07-2003, 02:40 PM

Tony,

I checked out those sites, and they are great in terms of information and what people have already done in this area.

I do not need to go so far as to get a controller, etc., as that exceeds my needs right now. I noticed a $30 VW wide band sensor that would work in terms of installation, but is it possible to measure an output voltage from such a sensor that is in the range the gauge and ECU I already have expect (.1-.9 volts)?

I think that is the whole point of the ECU they are selling, but I saw a few references to the "narrow band sensor output". Some wide-band sensors seem to have both sensors in side (the NB as a reference), so maybe that is what they were talking about.

Olivier