Where to place cts

[joegreen]

I was looking around today and realized i have nowhere to put my cts. I have a pipe plug in my thermostat housing and in my water pump. Could i buy an adapter to install the cts in one of those places. I know you need to make sure the cts has a flow of coolant over it. Is there anything i am overlooking. Motor is a non emissions sb350 with carb intake in a 78 k20

[brian617]

Thermostat housing is bad idea as it will only get coolant flow after stat opens. Hole in water pump bad idea too as that is return coolant that has already dissipated heat via heat core. Best location is in coolant crossover at front of intake, or even "T'd" in heater hose fitting leaving manifold to heater core. Some of those carb manifolds have a boss for drilling and taping to fit CTS.

[RobertISaar]

even "T'd" in heater hose fitting leaving manifold to heater core.

the 2.3 ranger used this type of setup..... it's not my favorite way of acquiring coolant temp data, but it is one of the least invasive ways of going about it. as long as you don't suddenly have a plugged heater core, it should be accurate enough since the rubber lines won't dissipate too much heat.

[lionelhutz]

I've seen thick spacer plates you put under the thermostat that can take a CTS sensor through the side.

[EagleMark]

Whatever you do with a "T", make sure the CTS is sitting very deep in the "T". If you just get the tip of CTS in flow it is not accurate.

[joegreen]

I dont have a boss to drill and tap in the intake manifold and a spacer under the thermostat housing is no good. Home depot here i come. Maybe i can rig up a (t). Another thing i should mention is my tbi adapter is from a 454 that has coolant running through it. Their is a pipe plug on the side but i would need an adapter. Also i am missing one of the outlets for the hose on the adapter.

[Six_Shooter]

What engine is this?

Post a few pictures.

NEVER EVER EVER put a CTS in the thermostat housing, the ECM will HATE the sudden change in temp when the thermostat opens.

[JeepsAndGuns]

I have mine in a "T" coming off the rear of the intake going into my heater core. It has been there since I first switched to fuel injection. Its been there with my old 7747, and my current 7427. Never had any issues.

[brian617]

NEVER EVER EVER put a T-stat in the thermostat housing, the ECM will HATE the sudden change in temp when the thermostat opens.

I almost always put a T-stat in my thermostat housing :laugh:

[Six_Shooter]

I almost always put a T-stat in my thermostat housing :laugh:

oops... :doh:

[notime2d8]

I had this same question and had a thread a few months ago. I had mines in the thermostat housing and it made the idle stay high until the t-stat opened as it was trying to get the car up to temp, And then it'll quickly drop down idle speed when it opened. It also messed with my car going into closed loop.

[EagleMark]

Gotta remember there's no flow of water in the T stat housing! Well not until it opens. The CTS needs a constant flow of water always so it knows when it's cols and what the temp is as it warms up. If you look at a TBI intake and where the CTS is... it's in a constant flow of water and when that water get's hot enough the T stat opens.

[joegreen]

some pics

[JeepsAndGuns]

Something interesting. Take a look at a Jeep 4.0, they have their CTS in the thermostat housing. BUT, the outlet for the heater core is also on the t-stat housing, and that is the part of the housing the CTS is located at. It gets the constant flow of coolant as it goes out of the engine into the heater core. So basicly its inline with the heater core.

Is that the outlet for the heater core to the left of your t-stat housing? If so, it looks like it has a thread in fitting. Simply remove it, and place a T between it and the intake

[lionelhutz]

Is there no threaded bung hole to the drivers side of the thermostat outlet? Most manifolds seem to have at least one threaded hole somewhere on the front coolant crossover.

Why can't you fit something like this under the thermostat?

http://www.summitracing.com/int/parts/mez-wn0028u/overview/

[joegreen]

i could but six shooter said to never place it in the thermostat housing. ill check and see if the heater hose fitting threads in. maybe i can rig up a T their.

[EagleMark]

That piece lionelhutz linked to is under the T stat and should flow good water. Just as the heater hose pictured would. But that heater hose could not have any kind of hot water cut off like some have.

And as for the T in hose! Every time I have used one it was to deep and only the tip of CTS was barely in water flow and did not work. The T needed to be trimmed down and re threaded deeper to let the sides of the CTS get water flow.

[lionelhutz]

The rule is never place the CTS after the thermostat. That plate goes under or before the thermostat. The only issue you might have with a plate like that is the sensor and thermostat clearing each other.

[joegreen]

I see now the thermostat goes in that new housing. I went to home depot and lowes and could not find any tee for the heater hose fitting and i could not find a tee for the oil pressure switch. I want to tee my mechanical oil pressure switch and the switch for the tbi aswell. I am trying to do this as cheap as possible and that new thermostat housing is a bit much.

[lionelhutz]

You don't need the oil pressure switch. It's just a backup to the fuel pump relay and there are millions of vehicles on the road that only use the relay.

[joegreen]

so a few questions on the oil pressure switch. If my fuel pump relay fails then i am stuck although i could just buy a spare. also does the oil pressure switch kill the fuel pump if oil pressure drops while i am driving. i wanted to use it kind of like a safety option.

[RobertISaar]

you could rewire the oil pressure switch to do such a thing. rather than having the switch provide an alternate current path for the pump, you would require both the relay on and switch above the cutoff pressure to get the pump to run. you might deal with longer cranking times and would possibly have to disable or modify the fuel pump DTC.

keep in mind though, if the pump shuts off and the engine is still trying to run(oil pressure switch opens up), you'll run continuously leaner the longer it goes. i think the better option would be to modify the code(if possible) to monitor the switch and if it indicates low pressure, completely cut off the injectors, rather than stop the pump and wait for the injectors to empty the fuel rails.

[Six_Shooter]

Robert it would take literally less than a second (in most vehicles) for the engine to stop running when the fuel pump stops. You can try this in your own car, have it running and then pull the fuel pump fuse, it will shut off quite quickly.

[RobertISaar]

i know, i've done it before. :laugh:

i actually have a fuel pump disable switch hidden away as an extra layer of theft prevention. on a OBD1 W-body, the fuel pump fuse will actually disable the ECM as well, IIRC. pulling the relay cuts only the pump though.

a second of the AFR going from whatever it is commanded to all air..... let's say 6000RPM, that's 100 revolutions, 50 of which would have a combustion event with a varying AFR. that seems like it has a lot of potential to cause issues. the first detected knock event(if it happens) could take up to 1.25 revolutions to recognize and account for(assuming 80Hz loops of the knock sensor register being read). a really bad knock event from proper spark but too lean of an AFR isn't as likely as too advanced/proper AFR, but if you're right on the edge of too much, that one event could shatter a piston. unlikely, but bad stuff. a TGP went down recently because of an injector that decided to flow significantly less than what it was supposed to while under some hefty boost...... piston supersized itself pretty quickly and locked up, followed by part of the crown seperating itself from the rest of the piston.... or perhaps that happened in reverse? either way, a good time was not had.

if i wanted to have the engine shut down if oil pressure went low, i would cut both fuel and spark to stop it.

[lionelhutz]

Install a good relay and don't worry about it. GM quit doing the oil pressure switch bypass in the 90's (and I doubt other manufacturers had a back-up bypass at all) and you don't constantly find cars dead on the side of the road due to fuel pump relay failures. With the possible failure of so many parts that are vital to the engine running, why just worry about the fuel pump relay failing?

[Six_Shooter]

i know, i've done it before. :laugh:

i actually have a fuel pump disable switch hidden away as an extra layer of theft prevention. on a OBD1 W-body, the fuel pump fuse will actually disable the ECM as well, IIRC. pulling the relay cuts only the pump though.

a second of the AFR going from whatever it is commanded to all air..... let's say 6000RPM, that's 100 revolutions, 50 of which would have a combustion event with a varying AFR. that seems like it has a lot of potential to cause issues. the first detected knock event(if it happens) could take up to 1.25 revolutions to recognize and account for(assuming 80Hz loops of the knock sensor register being read). a really bad knock event from proper spark but too lean of an AFR isn't as likely as too advanced/proper AFR, but if you're right on the edge of too much, that one event could shatter a piston. unlikely, but bad stuff. a TGP went down recently because of an injector that decided to flow significantly less than what it was supposed to while under some hefty boost...... piston supersized itself pretty quickly and locked up, followed by part of the crown seperating itself from the rest of the piston.... or perhaps that happened in reverse? either way, a good time was not had.

if i wanted to have the engine shut down if oil pressure went low, i would cut both fuel and spark to stop it.


At 6000 RPM it would shut off almost immediately, the fuel demands are much greater and so the existing fuel present and pressure would be exhausted in a very short time.

You're over thinking this.

[EagleMark]

I've hit fuel cutoff many times and never had an issue.

Every aftermarket TBI system I've ever seen and every harness I've ever built has no Oil Pressure switch. They all run off the relay only and failure of a relay is very rare. If it did there's a red wire hanging from stock relays for priming. If you hook 12 volt power to this you have fuel pump on always.

[joegreen]

ok so if i dont put on the oil pressure switch can i just leave that plug dangling or will the ecm be confused that their is no oil switch?

[steveo]

the ecm would never take an oil pressure switch input. it may take an oil pressure or temperature sender, but not a switch, and in your case, neither.

a switch would be for the fuel pump backup and/or a warning light in the dash

[EagleMark]

ok so if i dont put on the oil pressure switch can i just leave that plug dangling or will the ecm be confused that their is no oil switch?It's redundant, not even needed so you'll be fine.

[joegreen]

Thats nice to know. It relieves alot of headache for me. Now to concentrate on the cts. Thanks for everybodys help so far