EGT's vrs Gages

[Reddog1]

I have been chasing EGT's for over a year.



My Pyro is Isspro (?). I have asked for suggestions on reducing the EGT’s and I received some very valuable info.



Well, I think I may have discovered a way to lower my EGT’s by about 200 degrees. Just get a different gage!



I bought a used VDO pyro. I have both pyros installed.



At about 65 MPH. at 80 degrees, and altitude of 4000 feet, the Isspro is at 1000 degrees, and the VDO was at 800 degrees. When the Isspro shows 800 degrees, the VDO shows about 650. At an idle, the Isspro shows 350 and the VDO 250.



Reading the temps on these gages is like reading a thread on transmissions.



Obviously, I do not know which gage is correct. Just as obvious, I hope the correct one is the VDO.



Short of sending the gage/s back to the vender, anyone have an idea how to check the gages for accuracy?



How many of you know your gage is correct? If my VDO is incorrect, the previous owner of the gage could have easly distroyed his engine.



Wayne

 

[illflem]

A infrared temp gun works well to find out which one is right. Attach both senders to a bare light bulb with aluminum foil, fire it up and take the temp. You will need a gun that reads at least 800°.

 

[Reddog1]

Thanks Bill. I will see if anyone around here has a 800 degree plus infrared temp gun.





Wayne

 

[WadePatton]

My gauge is a Hewitt and I trust it because it reads the ambient air temp correctly. If my engine is stone cold, the pyro will be reading right at the outside air temp.

 

[Tardog]

To test the bottom end of the scale, drop both pyros in boiling water, this should be "200 ish" F. Maybe a bit higher takening into account of your altitude?

 

[dpuckett]

Originally posted by Tardog

drop both pyros in boiling water, ... . Maybe a bit higher takening into account of your altitude?

Actually, it would be lower at altitude. Say in the 190-200 range. Seems like I remember water boiling at 185 at 6500. Just trying to help; I dont kow everything.



Daniel

 

[Riflesmith]

If your ISSPRO pyro has a signal converter, you need to contact ISSPRO. Some of their converter boxes left the plant with a potentiometer set up incorrectly. Call their toll free number(should be listed in the instructions if you still have them), and have the instructions faxed to you. I went through this process last year when I switched to ISSPRO EV's. Corrected the problem very easily and the temps are much more realistic now.

 

[willyslover]

you didn't say if the isspro temps of 1000* were at climbing heavy throttle. . or just cruising down Hwy50



I'm at 4000' also [hwy 108 Twain Harte] and the VDO sounds more like my temps [at idle for sure, after a cool down time ] but also at the 1000* referance one above v/s VDO at 800* given it's a cruising temp and not some power added , meaning trying to go faster

 

[wlowe]

Well this was a perfect opportunity to test my new Craftsman digital VOM meter with built in infrared temp gun. At idle my Isspro EV Pyro was dead on with the temp gun (230 degrees).



Bill

 

[Reddog1]

Thanks for the input.



Riflesmith - I bought my gage when they were having the problem. At that time, I called them and they said my gage was ok. I think maybe they were wrong. I will call them again.





willyslover - I was just cruising.





wlowe - After you check yours, drop down and check mine please. LOL





I have decided that I will run two gages. First, have them read the same. It may sound like overkill, but if my Issopro was reading 200 degrees too low, I could have destroyed an engine. Pulling a trailer or camper at 1200 degrees up a grade would actually have been 1400 degrees .







Wayne

 

[dresslered]

I bought a used VDO pyro. I have both pyros installed

I'm curious as to where each probe is installed and are the lengths of the pyros the same? You can back out a pyro probe as little as 1/2" and see quite a difference in the readings. If you don't get the thermistor (inside the pyro) precisely inline with the hot exhaust stream, your temperatures can be way off. Even the temp guns will measure the manifold temperature rather than the exhaust gas temeperature. If the temperature probes are the same exact lenth, try swapping locations and see if the error between the two gauges tracks. Again, it could be a bad calibration in the gauges, but I would first suspect location of the probes.

 

[Reddog1]

dresslered - You make a good point. Both pyro probes are in the exhaust path center. I actually had the manifold off when I installed the VDO.



The Isspro was the first gage installed (about a year ago). As per the instructions, I installed it in 4-6 cylinders. I recently installed the VDO in 1-3 cylinders. I will swap the probe positions today, and see if I have the same results.



The Isspro is much more responsive than the VDO. I am comparing readings at cruise.



I have been exceptionally busy recently, so I haven't had time to contact the vendor.





Wayne

 

[illflem]

Even the temp guns will measure the manifold temperature rather than the exhaust gas temeperature.

I've found the manifold temp and pyro temp to be pretty close if you've been driving the truck then stop and idle for a few minutes.

Never been able to talk anyone into riding under the hood with the temp gun to get the manifold temp at cruise though.

 

[dresslered]

Wayne-

Actually, I am surprised that the ISSPRO uses a 1/4" pyro as the VDO does. I really like the VDO but many people prefer an 1/8" pyro because of the increased responsiveness. I'll be curious to hear about your results. I don't think that the locations that you mentioned would differ by the 200 degrees--again, I would compare the depth of the two pyros.



Illfem-

I would agree that during an idle, the exhaust stream would roughly equal the manifold temp. During a hard acceleration or pull, I would expect to see a larger delta. C'mon, don't you have anyone daring enough in the Bitterroot to ride the block?

 

[Reddog1]

Thanks for the input.



illflem - At an idle, both gages are about the same. The most obvious difference is when the Isspro is at about 900and the VDO is 650. When the Isspro is 1300 the VDO is 1100.



dresslered - I an satisfied that both pyros are in the same stream. I installed the VDO with the turbo just to make sure.



The pyros on both are 1/4". The Isspro is definitely more responsive. That is not the issue. I am comparing the gages at cruse, so response time is not a factor.



I will keep you posted. My free time lately has been very limited.





Wayne

 

[d90boy]

It seems to me like the very responsive pyros use the D'arsenval (sp?) movement where there is no extra power wire needed to the gauge. The Isspro sounds like one of these whereas the VDOs I've had look like a normal gauge but require a power source to work. There is a big difference in their movement, the VDO is quite slow to respond.

 

[WadePatton]

I have a Hewitt and it requires no extra wiring. VERY responsive. I wouldn't have it any other way.

 

[bmoeller]

My Isspro pyro is VERY responsive. This one doesn't use an electronic box to control it. Just has the 2 wires to the thermocouple and 2 for the backlights.



Where is your thermocouple located? If it is slow, sounds like it is post turbo instead of pre in the manifold. Post responds Very slowly unless you have hose come loose and loose all your boost. Then it will move VERY FAST!