| Author |
Message |
raygreenwood
Samba Member
Joined: November 24, 2008
Posts: 21513
Location: Oklahoma City
|
 Posted: Fri Aug 28, 2015 3:17 pm Post subject: |
 |
|
Take a picture of the multimeter face so I can tell you how to set it up. Typically most have an auto-range feature.
The 175 ohms hot would not be out of the question...in fact it would be very good.
It sounds like your reading is off by a factor of 10....which would give 2500 ohms cold...which is about right.
Your dial meter does not really have an adequate dial range for this.
If we can verify that the CHT is in the correct range we can move to the next test.
Ray |
|
| Back to top |
|
 |
Lars S
Samba Member
Joined: October 04, 2007
Posts: 783
Location: Sweden
|
| Posted: Sat Aug 29, 2015 4:18 am Post subject: |
|
|
| ClassicCamper wrote: |
Hi again, so next test completed. I suck with the multi meter, so please bare with me. Here is what I did:
1) Set meter to zero. Touched leads together to zero out.
2) Connected Red lead to disconnected temp sensor cold. The reading was 175 on the black set of numbers below the top green ones
3) When engine was hot (operating temp), The reading was 250 in the black line of numbers or 0 on the top most set of green numbers. Note: this is the same reading I'd get if I touched the two leads together.
4) Meter was set on Ohms x 1k
Sorry for the ignorance. Still getting used to it. I'm getting bummed out that this isn't accelrating smoothly at all. But, I'll keep plugging away. Open for suggestions. |
Looks like you have used the meter correctly.
According to your meter settings and readings you have about 2 Ohms cold and 0 Ohms warm...that reading corresponds to a wery hot motor and results in a lean mixture calculated by the ECU. Surprised you can start and run it cold.
If we can werify that the readings are OK the sensor is definitely out of range.
Lars S
_________________
Porsche 914 -72, Bahia Red daily driver 
VW411 2-d -70, White, sold 
VW412 4-d, -73, Gold Metallic, daily driver
Suzuki T500, -69, Candy Gold, sold
Suzuki K50, -77, Black, daily driver
BMW R69S -69, White, sold
Husqvarna 118cc, -47, Black, Sold |
|
| Back to top |
|
|
raygreenwood
Samba Member
Joined: November 24, 2008
Posts: 21513
Location: Oklahoma City
|
| Posted: Sat Aug 29, 2015 7:15 am Post subject: |
|
|
| Lars S wrote: |
| ClassicCamper wrote: |
Hi again, so next test completed. I suck with the multi meter, so please bare with me. Here is what I did:
1) Set meter to zero. Touched leads together to zero out.
2) Connected Red lead to disconnected temp sensor cold. The reading was 175 on the black set of numbers below the top green ones
3) When engine was hot (operating temp), The reading was 250 in the black line of numbers or 0 on the top most set of green numbers. Note: this is the same reading I'd get if I touched the two leads together.
4) Meter was set on Ohms x 1k
Sorry for the ignorance. Still getting used to it. I'm getting bummed out that this isn't accelrating smoothly at all. But, I'll keep plugging away. Open for suggestions. |
Looks like you have used the meter correctly.
According to your meter settings and readings you have about 2 Ohms cold and 0 Ohms warm...that reading corresponds to a wery hot motor and results in a lean mixture calculated by the ECU. Surprised you can start and run it cold.
If we can werify that the readings are OK the sensor is definitely out of range.
Lars S |
Yes.....what lars is stating is what I was hetting at.
At no time should the CHT....when its at its hottest......read "0" ohms. This is why I want to be sure you are reading in the correct range on your multimeter.....because if you are in a setting that is an order of magnitude higher than it should be......it will read 0 ( actually it will not read 0, just that the meter will not have the resolution to display anything other than 0 in that setting).
However....the CHT should not ever read below about 2000-2200 when cold depending on ambient temps......and when lightly warm......like less than 5 minutes....depending on temp of head.....could read anywhere in the low 1000+ to a few hundred ohms.
Just from what i can see......your CHT reads.....you note when cold....but what temp is "cold"? It changes rapidly as temperature rises and falls. At freezing it can be close to 3000 ohms. At 72F.....it could be just below 2000 ohms.
You should be reading on the green scale on that meter.....and that would say about 1700-1800 ohms.
Your reading of "0" when warmed up.....again....on the green scale.....is, reading 0 because that meter barely has the resolution needed. Is it reading 0 on the green scale...or just close to it?
Either way if the meter is accurate.....50 is too low when warmed up. 0 is, way too low when warmed up.
About 75 is as low as most CHT that are jn good working order should go.......and that is too low. It should not drop below about 100 ohms when fully warmed up.
This means that either the CHT is faulty....or you are running quite hot.
For the moment.....insert a 125 ohm resistor in line with the CHT and drive it again.
Also.....once I find the range that the car runs best at for maximum warmed up....say 125 ohms......I disconnect the CHT and connect a fixed resistor in place of it....attached to ground on one end........as a temporary fixed setting......to do all of the rest of the fuel mixture tuning.
To really get the fuel mixture correct....you MUST do this. If not....every adjustment you make to fuel mixture....even if its correct. ....will show you the wrong result because the CHT keeps changing it.
So.....install a fixed resistor. Drive and adjust thd outer full load stop....FIRST. Adjust until it runs best.
Then reattach the CHT and let the car fully cool....and drive it again. If the CHT drops to low again now.....at least you know that it is NOT the full load stop because it is now properly adjusted.
Re-install the fixed 125 ohm resistor.....and now adjust the center setting.....about 1/10th of a turn or less at a time....until the car runs best. Then reinstall the CHT......and let it fully cool. Drive it again. After a main fuel adjustment on the MPS.....you will need to repeat the outer full load stop adjustment. ....because changing the main mixture....changes that adjustment.
Reconnect the ChT and let it cool again. The car should be driving quite well now if all else is correct (timing, advance and fuel pressure). If the CHT is still, dropping below 100 and causing problems. ....install the a resistor inline to the ChT that allows proper warmed up range of 100-125 ohms at maximum warmed up state.
Once that is, done.....you may need to retweak the main, mixture. Ray |
|
| Back to top |
|
|
|
