CHT gauge vs AFR gauge, when they’re needed Options

[Literati914]

I’m contemplating the addition of an AFR gauge (wide band) and a CHT gauge. But was wondering when you guys feel each is needed?

For instance AFR readings are apparently helpful with carbs, but is a gauge needed with aftermarket EFI systems (don’t they usually have AFR run through a tuner program)? Any use when running Ljet or Djet?

As for a CHT gauge, - I’m wondering if those are really necessary if you’ve got the A/F set properly in the first place (engine oil and cooler assumed clean and fresh). Isn’t proper A/F under different loads, the key to keeping temps in range?

.

[technicalninja]

They do different things and I believe you need both.

Digital FI should ALWAYS employe a wideband. Most of the time you can piggyback a gauge onto it if you want but I'd set the unit up to actually log O2 sensor at all times.

I will try to add CHT logging to my set up as well.

Things I'd prefer to have logging on.
WB02
Fuel pressure.
Oil pressure and temp.
CHT. (air-cooled)
MAP/MAF.
RPM.
TPS.
Boost (if blown)
IAT. (pre turbo, post turbo, post intercooler if blown)
EGT.
Coolant temp (water pumper).
Knock sensor.

Things I'd want a visible gauge on. (requirement)
Speedometer/Odometer (unnecessary on race car)
Oil pressure/temp
RPM
Coolant temp (water pumper)
AFR- wideband
Voltage/amperage (either/or/both).
Boost/vacuum (blown)

Things I might want a gauge on (space permitting).
CHT
EGT
Fuel pressure.

Things I'd want a BRIGHT warning light as well on.
Oil temp/pressure.
Fuel pressure.
Coolant/CHT temp.
AFR 16/1 and above, 9/1 and below.
Knock sensor

Sometimes the oil pressure gauge can be used for multiple measurements. Flip of a toggle switch could put FP where OP was a moment ago. Same way with the oil temp gauge. That could read coolant temp or maybe even CHT/EGT (with a very special gauge-probably digital).

Race car would have gauges all tilted so when everything's "in the green" all the needles would point directly up for sweep checking.

[rfinegan]

Both are great tools when setting up a new engine or fuel system.
After that, they provide information that the system is working properly, or not working properly. So the value is subjective at that point. NICe to have but not needed

FWIW: I have both CHT in the console and LM1 hand held and can hook up when needed. For Carbed 2056

[StarBear]

I found that an AFR was essential in dialing in the setting for the new AFM in my LJet. Got the bung installed and ran the probe cable under the car thru the engine pan seal up through the engine compartment around the passenger sail panel and into the window so I could monitor it while driving. Temp setup only; no permanent installation.

Would love to do a in-panel CHT gauge; maybe someday.

[Literati914]

Ok - I actually like the idea of data logging without any permanently mounted gauges (for simplicity sake).

I understand that A/F can be controlled this way on aftermarket EFI systems (and Ljet apparently), but can we do the same with CHT ? Maybe just run a thermocouple wire directly to an ECU ? I'm not sure how that could be incorporated.. maybe there's an adapter needed?

What are the options for both/either CHT & A/F monitoring withOUT a permanent gauge and would interact with a given EFI ECU?

.

[StarBear]

Ok - I actually like the idea of data logging without any permanently mounted gauges (for simplicity sake).

I understand that A/F can be controlled this way on aftermarket EFI systems (and Ljet apparently), but can we do the same with CHT ? Maybe just run a thermocouple wire directly to an ECU ? I'm not sure how that could be incorporated.. maybe there's an adapter needed?

What are the options for both/either CHT & A/F monitoring withOUT a permanent gauge and would interact with a given EFI ECU?

.

For the AFR, see above. I’ve read (but not done) that a potentiometer can be used with the CHT to control resistance to the ecu. Some threads on that.

[Porschef]

I’ve been running both for years, but at this point the CHT gauge has become much more valuable as it keeps a lookout on temps constantly. I try to avoid going over 375° which is likely on a hot day going uphill. Lets me know when it’s time to downshift without guessing.

Now that the AFM is dialed in it’s not all that important to have, unless something goes way wrong (like when the ECU crapped out). I may remove it and sub in a voltmeter.

If you decide on a CHT gauge, I’d highly recommend the Dakota Digital unit. Very accurate. While I prefer analog stuff, this is an instant readout. I’ve read that the VDO units are not as accurate or responsive.

Hope that helps (IMG:style_emoticons/default/beerchug.gif)

[emerygt350]

Both are super useful. Cht is important for even a perfectly running engine. I took out my original gauge panel in the floor console and made a new one with room for my cht and AFR. No damage done to my original piece that way.

[Literati914]

For the AFR, see above. I’ve read (but not done) that a potentiometer can be used with the CHT to control resistance to the ecu. Some threads on that.

I was asking about what specific units to look for that can run via either ECU only and/or with a gauge.

.

[Literati914]

Now that the AFM is dialed in it’s not all that important to have, ..

..If you decide on a CHT gauge, I’d highly recommend the Dakota Digital unit.

Which is why I'm not crazy about actually mounting a permanent gauge, and am trying to ascertain which ones are available that can be monitored remotely (hand held device or ECU programming). I think I remember someone mentioning a blue tooth unit, which may be the ticket. But even a wired one thru the window (as described by the other member above) for tuning purposes is fine. I'd like to know brands and models tho, if possible.

Yes dakota digit CHT is probably the only one I'd get IF mounting a CHT gauge. IF there was a good anolog option I'd be all for it - I don't mind adding gauges per say. I'm just trying to avoid a digital gauge in an anolog aircooled /4 daily driver. I mean there's lots of 914 running around without CHT gauges, but I get that some people feel the info is necessary too. So, again if something that could be hook directly the EFI control units and monitored that way.. or via some hand help device I want to consider that an option.

[emerygt350]

It's hard to find analog cht or AFR. I have an analog (looking) AFR but I couldn't find any reasonable analog (looking) chts. I have seen too many pictures of dropped seats to not have one even though I admit it is ugly.

[FlacaProductions]

Aircraftspruce.com - search around in there for "CHT" - quick one that I just did shows plenty of analog CHT gauges although I didn't dive in. My only requirement was that it be temperature compensated and the Dakota is just that - and proven in our 914 world. I do wish it were analog, tho. There are versions that I've seen on ebay/amazon that are digital but can drive a relay (or have one onboard) that could be used to trigger an external alarm and/or LED at a certain threshold - not sure if they are temp compensated or not, however. But you could hide the main unit behind the console gauge panel and install a discreet LED somewhere (the FASTEN SEATBELT light, for example) as long as you know what the indicator indicates!

[emerygt350]

Yeah, I saw those aircraft gauges, mucho dineros.

[emerygt350]

Aircraftspruce.com - search around in there for "CHT" - quick one that I just did shows plenty of analog CHT gauges although I didn't dive in. My only requirement was that it be temperature compensated and the Dakota is just that - and proven in our 914 world. I do wish it were analog, tho. There are versions that I've seen on ebay/amazon that are digital but can drive a relay (or have one onboard) that could be used to trigger an external alarm and/or LED at a certain threshold - not sure if they are temp compensated or not, however. But you could hide the main unit behind the console gauge panel and install a discreet LED somewhere (the FASTEN SEATBELT light, for example) as long as you know what the indicator indicates!

Having it hit a light would be great. Something like the oil temp light, however, once it comes on I bet you will start wishing you had the full gauge real fast.

[Montreal914]

Here is another option for the CHT kit. You can customize it (right side of page) such as: Sensor ring size, cable length, 0-5V output (for modern EFI), etc.

It can be set up with a light or buzzer @ temperature you can program.

https://thesensorconnection.com/product/cht...r-kit-ws?v=2398

Obviously not analog, but a reasonably priced option.

It would be nice to use the 0-5V output to drive a 60mm VDO volt gauge (somehow) that one would have converted the faceplate for a scaled head temp gauge. (IMG:style_emoticons/default/idea.gif)

[rjames]

I really like my PLX Bluetooth AFR. App is on my phone. No need to add a gauge unless I want to, and a gauge can plug into the existing head unit that is about the size of a deck of cards and tucked away behind my center console.

[FlacaProductions]

@Montreal914 - yup - that's exactly the unit that I was thinking about. Using the 5v output may be something to talk to John Bell about...

@rjames - which model PLX do you use - SM-AFR WIDEBAND + MULTIGAUGE LINK COMBO (GEN5)?

[rjames]

@Montreal914 - yup - that's exactly the unit that I was thinking about. Using the 5v output may be something to talk to John Bell about...

@rjames - which model PLX do you use - SM-AFR WIDEBAND + MULTIGAUGE LINK COMBO (GEN5)?

What I've got:

[FlacaProductions]

@rjames - thanks.

[VaccaRabite]

IMO every 914 should have a CHT gauge. Every. Single. One. That is the measure of your heads and it changes WAY faster then oil temps. Dash gauge is run from a ring terminal on the spark plug off Cylinder 3 - not the stock location. My ECU uses the stock location for warmup enrichment, but the location is not as accurate or as fast to change.

I track AFR as well, but I don't have a cabin gauge for it. The ECU watches that and I'll pick it up in the logs, or I can plug in the shadow dash if I want to see it.

Zach