Fitech Coolant Temperature Sensor Reads Low
 

Did a quick search and didn't find anything so I thought I would share. The Fitech CTS reads low, by about 20 degrees, this will affect your EFI maps and cause enrichment. My car showed a maximum of 168 degrees, I changed out my thermostat, this did nothing. I read the Fitech CTS sensor often reads low. I changed it to an AC Delco 213-928 and viola it reads 186. I also put in a set of hotter plugs, the combination of the two really made the car run better. If you are certain the EFI temperature is reading low, spend the 20 bucks and change out the CTS to the AC Delco unit.

That's been an on going issue for quite a long time with the Holley stuff too and has pretty much come to be accepted, accept the majority I've read claim they read too high. I tend to think FiTech and Holley use a lot of the same sensors. Part numbers for sensors to correct the issue are provided on the Holley website if you want to just buy them locally.

I just went to O-Reillys and bought a couple of them.

On our Holley EFI's they both read too high compared to the mechanical gauges we still had on both cars. The new O-Reilly sensors had the temps dialed perfectly with the mechanical gauges. It also helped with cold start fueling which seemed to be where I noticed it most.

It's typically an OHM difference between your electric sender for the FiTech and your mechanical gauge elsewhere in your car. Sometimes they'll be completely off always. Othertimes they may be slow (in my case). My sender eventually reads within 1 degree of my mechanical guage, but it takes a couple minutes to catch up.

The best known sensor for accuracy with the FiTech is the AC Delco 213-928. It's about 30 bucks.

Our EFI temps were reading 15 degrees high on both cars, throughout the entire temp range. They were consistent, but off.

That happens a lot if the sender is in the head, near the exhaust. It will pick up some of that EGT and transmit it. That said, in the head is actually the best place since the fueling calculations create cylinder temperature by reading IAT and Coolant. By having the CTS in the head you don't have any radiant cooling effecting the reading if it's taken in the cross-over.

I was running both senders in the water cross over right on either side of the thermostat. The AFR heads I use on one of the cars (Chevrolet) doesn't have provisions for a sender.

On the Pontiac dad chose to have both senders at the water crossover so he could hide everything under the intake. He didn't want a sender in the head.

Eventually, after we got the EFI reading correct temps on both cars that matched both mechanical gauges, the extra gauges were removed. Ended up adding sensors to monitor fuel pressure and oil pressure too so those mechanical gauges could also be removed. Now the Snipers monitor everything on the handheld and it cleaned up the clutter of extra gauges.

On a side note, those 0-100psi pressure sensors tend to read a little lower than the mechanical gauges, opposite of what I found on the coolant temp sensor.
I had fuel pressure set at 60 psi on the Chevelle with a very nice (expensive) autometer mechanical gauge. When I added the holley 0-100 psi pressure sensor, which ironically costs $100 by itself, it would show 57 psi. Since I had the cars base fuel table dialed in really well at the 60 psi I had with the mechanical gauge, I left it be, removed it, and just monitor it with the Sniper, and realize it might be reading 3 psi low. Oil pressure was spot on (mechanical vs Sniper sensor)

Dad had a similar issue but with oil pressure. He felt the oil pressure on the Sniper was lower than usual the other day on our 300 mile cruise. I temporarily hooked up his Autometer mechanical gauge and it seemed to be maybe slightly higher. Problem with a mechanical oil pressure gauge is it's very slow to change, the Sniper changes constantly and reads down to the tenth. Regardless, I changed the scaling on that sensor in the tune to mimic more what the mechanical said.

So these pressure sensors seem to be hit or miss. Some seem okay to me, others read a little low.