When I bought my 92 Formula (L98) I was informed that it had an aftermarket 180 degree therm, but the heater didn't work well so I changed it out. I got a 160 because: 1. I read that 180's don't do as well in colder climates. It was an Arizona car, and Indiana ain't Arizona. And, 2. I thought these engines came from the factory with 160's, so I figured it would be happier anyway. But this week I was informed that if I'm using a 160 the car is tricked into thinking it needs to run richer, causing mixture issues. I've been having mixture issues, and threw a 23 code last week. Spent the week trying to fix all that--those familiar with my code 23 thread from last week will know all about that. ("How do I complete a circuit to test an ECM wire") Wiring checked out, sensor checked out, and I ended up changing ecm's, but when I started it up, I still got the low rpm idle and rich smelling exhaust. After running it for a few minutes it does ok. So could a 160 therm really make that much difference? Seems far fetched to me.

 

car comes factory with a 190. Use a 190 or a 180

 

....most forums I see recommend 180 to burn off condensation in the oil and etc. Maybe I really should switch back? The funny thing is, I ran that 160 for a while and had no problems. The low idle and seeming rich condition only started when the weather warmed up. Is there a connection? I'm betting so, but don't know enough about this to say for sure. What saith the forum?

 

Really? Ok. That makes sense, my car is probably confused. I'll switch back ASAP.

 

But then, another question. Wouldn't any therm be closed up at startup? No matter what kind? Even a 180 would close at startup, so would that really solve the low idle and car confusion issue at startup? The coolant is always at ambient temp at startup no matter the therm.

 

Well if the car is running "rich" then the plugs will be fouled already and that might hurt the idle somewhat... But just making sure you know that a lower thermostat temp in cold weather is going to hurt... Now if you live in texas or the equivalent then yes get like a 180 thermostat so it is "Happy"

 

Oh and to answer your question... Yes the thermostat doesn't open until it sees temps that it's rated to open at. Basically a 180 thermo will open when the coolant hits the 180 temp.

 

Ok last quote haha. Basically that's rite that if your thermostat is to low for the application it's in, then the car will never reach ideal operating temps that burn the condensation in oil (Mostly cars that aren't taken for long drives have this issue).

 

A 180* thermostat with a adjustable, temperature controlled, fan switch set at 190*

 

This is a good setup.

 

Ok, now is there a typo here? What you said confused me. You said a cooler therm would hurt in cold weather, but then said if I lived in Texas (hot) to get a 180! I live in Indiana, and it gets very cold here during the winter. I blame Autozone for part of this. When I went in to ask for a therm, and told them my car/engine, a 160 is what they gave me, and something else I read online said these cars came with a 160 out of the factory. It had to be true because it was on the internet!

 

Ok sorry for confusing you haha I kinda rambled on... Basically though a lower thermostat like a 160 is not good if you live In a cold climate. If it's around 40F-50F or colder then you should run the factory 190thermostat. Now if you live in a hot state like me (TEXAS) then you'd wanna run around a 170-180 thermostat to prevent overheating in stop N go traffic or on a spirited drive.

I don't think many people that run the 160 thermostat actually "Need" it. Mostly a track car would run a 160. JMHO

 

Lower thermostats make the car run COLDER, and in COLD weather it will never reach the IDEAL temps that these cars are meant to be ran at which is around 180-190ish.

That sums it ALL up lmao.

 

Ok, I understand. Sorry for the confusion.

 

Absolutely. I agree that makes perfect sense, and it makes me wonder why Autozone would give me a 160? Live and learn. I was gonna change the plugs out anyway, no big deal.

 

 

I run a 160*F thermostat in my 1997 Express. Fans are set to turn on at 176*F. Going down the interstate it runs about 170-172*F.

My 2012 and now 2014 Nissan Titan have a nissan motor sports aka Nismo thermosat for a 300ZX installed in it that starts to open at 144*F and it maintains a ~170*F coolant temp year round.

With stock thermostats in hot weather, the timing advance curve has to be sacrificed too much for my tastes.

My Ram also had a much cooler thermostat than the stock 205*F. I believe it was 164*F or something close. Ran around 170*F year round. Was metric rated from a Mazda MPV van application and ground down 1mm to fit the Hemi housing. The Ram saw track gains of 1-2 tenths in warm weather with the cooler thermostat and practically eliminated the clutch fan from kicking in and further slowing the truck.

 

The engine should run fine with either, as far as 160 vs 180 or 190. 160 lets the engine run cooler which is nice for oil and aluminum heads and not pinging. 180 190 is more thermal efficient and gets better mileage but harder on oil and detonation. Doesn't make much difference to the heater.

 

I run 160s in my cars with the correct fan switch for the temp.
I don't run my cars in the winter. I would run a 180 in the winter.

 

because all auto zone employees are "mc donalds run aways" with the intelligence of your average rock. DO NOT buy parts from auto zone!!

 

The thermostat is to maintain a minimum operating temperature. Once it's open, it's open. The water pump, fan and rad need to keep the engine from running hotter. If you're overheating in stop and go traffic either your thermostat isn't opening properly to allow proper flow or the rest of your cooling system can't remove the excess heat properly.

Unless the ECM has been reprogrammed for a colder operating temp, running a colder thermostat will keep the ECM in an open loop and burn more fuel because it sees the engine isn't hot enough and keeps dumping in more fuel to make it hotter. Sort of like using a choke. Vehicles with normal emissions on them will normally run in the 190-205 range. A hotter engine produces less emissions at the sacrifice of power that a properly set up cold running engine can produce.

If you run a carb then you can run whatever thermostat you want. 160 in always hot climates. 180 for general year round use and 195 for northern climates with more cold months. Just remember, it's a minimum heat. In really cold weather, an engine may not even reach 195 so the thermostat won't even open.

For track only, the engines don't run long enough to really worry about engine heat unless they're hotlapping, road course racing etc. Running a thermostat in a track only car just helps it warm up faster. I don't run a thermostat in my car. Running alcohol fuel, the engine has a hard enough time making heat and I use a tiny rad. I usually have the water pump shut off until I'm ready to make a run then leave it on until I get back to the pits. It takes 5-10 minutes to get the engine back to around 100F sitting in the pits with the water pump and fan on. No thermostat and the fluid flows freely through the system to cool it down.

 

With TPI, The ECM will go closed loop with coolant over 100degs, a certain amount of engine run time and when the 02 sensor gets to 600degs. (IIRC)

Even a car 100% stock can go open loop with extended idle time, which is why it's a good idea to step up to a heated 02 sensor.

 

All you guys that are mentioning what thermostat your running truly aren't helping him.

Sorry but I saw 2 of you that live in TX (Even thought the 1 mentioned not running his in the cold) and Texas is not as cold as where this guy lives so please don't confuse him by stating what YOU run and he needs to run around a 190 thermostat because of where he lives.

 

I wouldn't use a 195*F if I lived in the Arctic circle!!! The GM ECMs are in closed loop before they ever even reach 110*F. Ever heard of HOT SPOTS! Almost ZERO cars before the emissions era ran a thermostat over 170*F. Hotter temperatures are an emissions bandaid. Bore wear stops around 140*F. My Mercruiser marine engine has a thermostat that opens at like 130 or 140*F and it runs under 160*F year round. In 40*F weather with the lake in the 40* range, it injects water from the lower unit right into the inlet of the water pump, forces relatively cool water through the block, it hits the water neck where part of it is recirculated to the inlet of the water pump and the excess is pushed overboard through the exhaust manifolds and risers. It runs very cool year round and guess what its just a chevy 305. I run it very had and as a result had to rebuild it about a year ago at about 800 hours when it started having massive piston slap. Turns out one of the skirts had broken and the piston was wobbling in the bore. The bores were flawless though. Even though I could still clearly see the crosshatch and there was no ridge, a light hone, a new piston, and new 2 piece total seal gapless rings went in at the recomeended gap. After a few trips, the rings seated I runs GREAT.

On a country morning in janurary the temps in Texas can be single digits, so its not all warm.

 

Uhh I have lived in texas for the last 9yrs... and coming from florida it's way more dry here and it never hits single digits (Not that im aware of)... Usually high 80s-90s during the summer.. And around 40F-70F during winter

Also Im pretty sure running around a 160thermostat doesn't benefit you "stock tpi motors" in cold weather... And I know a 180ish thermostat is plenty fine in a cold state unless your cooling system is crap. So let's just leave it at that lol.

 

Quit talking out of your rear until you have some concrete data to back this up. 160*F dramatically helps me by allowing me to run more timing advance and keep the intake charge cooler. Less intake heat = cooler IATs and less timing retard. The cooler the engine runs the less of a tendency you have to detonate, PERIOD. EVERYTHING I have ever owned HATED the heat and required the timing to be backed off during hot months or else face detonation.



Where my family has a vacation place close to Jacksboro, TX it gets plenty cold in winter. A few years ago I spent New Years day there with the family, went to drive in the next morning and it was 7*F on my overhead temperature display. The all time low temperature is recorded as -8*F on December 22, 1989. Also woken up many mornings with the temperature below 20*F where I live between Fort Worth and Dallas.

http://average-temperature.findthebe...acksboro-Texas

 

Umm hey SMART *** why don't you re-read what I wrote and maybe you'll comprehend that I said (In very cold weather states like where the OP lives you shouldn't run a 160 thermostat)

And sorry but nobody gives a **** what thermostat your running in your 305 sbc boat which is mostly irrelevant to say the least

 

This is what you wrote above:
"EVERYTHING I have ever owned HATED the heat and required the timing to be backed off during hot months or else face detonation."

LMFAO you even said ^^^ it yourself. IN HOT MONTHS YOU HAD TO BACK OFF YOUR TIMING. Now im no genius but I quite frankly stated many times that I was talking about the thermostats in COLD WEATHER... As in places like where the OP lives and not just a random damn state like texas which reaches 90 degrees regularly.
So just quit arguing as im correct and your wrong. Now give me some good reasons and quit claiming what your boat likes/needs.

 

Just quit trying to understand, if you cannot comprehend that 180*F is the same 180*F in Alaska as it is in Mexico City. SMALL BLOCK CHEVYS HATE HEAT SIMPLE AS THAT!!! Keep them under 170*F and they are happy. Like it was said earlier that is the opening point of the thermostat. Why would you need to run the engine hotter in cooler weather??? It will take the same amount of time to warm up regardless whether it has a 160*F thermostat or 205*F thermostat.

The reason the boat comes into this is it is a ****ing chevy 305, simple as that. If you ran a boat engine hotter it would self destruct from detonation!!!

Pulling timing is VERY REVALANT, especially on a TBI or TPI or any later model engine with a knock sensor. When they get hot the ECM will not only retard the timing as coolant and IAT temps rise, it will also sense detonation with the knock sensor and pull the timing back. Some more moder ecm algorithems also have low octane logic that will pull 6-8* of timing until the fuel level in the tank is altered.

 

Also point of the matter, the thermostat is NOT causing the original posters idle issue. It is something else, like a bad IAC, bad TPS, misadjusted TPS or a bad coolant temp sensor. Also keep in mind that the TPI engines run on base timing of 6*BTDC until they reach about 100*F. This cause them to run rich and rough, took me several days of searching through the 7730 ECM hack to find the coolant temperature parameter to enable ECM spark advance control at ALL temperatures.

 

Never said that's what was causing his poor idle condition... I simply just explained to him how the thermostats work

 

Ahhh so your telling me that these cars (Low CR ratio motors) will pull timing to prevent detonation when they hit 180 Degrees or even 200? If that's what your saying (It is) then your wrong. These lb9 and l98 motors can run on 89octane and run around 200F and they still wont get detonation at only 200F temp. Also most 80's SBC motors like around 180F temps.... Just saying

 

Closed-Loop CAN happen as low as some have stated, but that is only ONE condition which allows Closed-Loop. All conditions must be met to achieve Closed-Loop mode, and if the ECM has stock programming, or just slightly altered programming, the parameters for closed loop operation should look something like this:

AUM/BUA Closed-Loop Operation Parameters
CTS < 14.7°C (58°F) for 75 seconds;
CTS >14.7°C (58°F) and < 40.7°C (105°F) for 51.4 seconds;
CTS >40.7°C (105°F) for 12.5 seconds;
O2 >0.699V & O2<1.99V for 10 seconds;

Coolant Temperature Sensor Related Parameters
BLM enabled between 50°C (122°F) and 140°C (284°F)
Cold spark advance disabled above 56°C (133°F)
Hot spark retard begins above 116°C (240°F)
Highway Mode spark advance > 59.8°C (140°F)
Knock sensor disabled below 66.5°C (152°F)
Power enrichment at base A/F ratios > 56°C (133°F)
Target IAC idle RPM >80°C (176°F)
IAC multiplier at 1.0 (base) > 32°C (90°F)
Knock Control enabled > 67°C (153°F)
EGR Duty-cycle enabled at 56°C (133°F)
EGR Duty-cycle at MAX >80°C (176°F)
TCC lockup enabled >50°C (122°F)
SHIFT light enabled >50°C (122°F)
Diagnostic communication enabled at 70°C (157°F)
DTC 43 enabled > 90°C (194°F)
Cooling fan #1 enabled at 107°C (226°F)
Cooling fan #1 off at 104.7°C (220.5°F)
Cooling fan #2 enabled at 115.2°C (239.5°F)
Cooling fan #2 off at 110°C (230°F)
Cooling fan duty cycle at 100% at 80°C (176°F)
Acceleration enrichment multiplier at 1.00 below 80°C (176°F)
Acceleration enrichment multiplier at 0.75 above 80°C (176°F)
Acceleration enrichment multiplier at 0.50 above 104°C (220°F)
Acceleration enrichment decay factor at 25% below 80°C (176°F)
Acceleration enrichment decay factor at 40% above 80°C (176°F)
Acceleration enrichment decay factor at 50% above 104°C (220°F)
Acceleration enrichment decay factor at 60% above 128°C (262°F)
Fuel limiting factor timer at 217 counts below 80°C (176°F)
Fuel limiting factor timer at 169 counts above 80°C (176°F)
Code 13 (oxygen sensor fault) enabled above 70°C (157°F)
Code 14 (CTS high fault) enabled above 130°C (266°F)
Code 32 (EGR fault) enabled above 30.5°C (87°F)
EVAP canister purge enabled above 70.3°C (158.5°F)
Hot closed-loop timer enabled above 70.3°C (158.5°F)
Rich/Lean O2 offset at 16 counts between 20°C (68°F) and 92°C (197.5°F)
A/C clutch disabled above 150°C (302°F)

 

ABSOLUTELY DO!!!! Log a stock engine running stock timing advance and you will be suprised how much knock you record when the temperature rises above 180*F and you load the engine heavily.

9.5:1 and iron heads with the tiny stock cams is not "low compression" for pump gas.

 

I just can't see it getting knock from temps lower then 200F. So im gonna do a bit of re-search for my self. I have never had any timing retard in my ls1 motor (Higher CR then TPI) and I have even ran 89octane gas in 80-90F weather with WOT runs with the stock thermostat.

So if im wrong i'll be back to apologize

 

Hmmm, I think we need to stick with Gen I engines for this "discussion", LS1s need a lot less timing and their operating regime is quite different.

 

Yea their basically different motors... But still I was just saying because it's a SBC and the argument has basically turned from what tpi motors like to what a SBC motor likes.

Here's where it turned
"SMALL BLOCK CHEVYS HATE HEAT SIMPLE AS THAT!!!"

 

TPI = SBC with a port fuel injected intake tuned to resonate around 3,000 rpm.

LS1 = completely new design from the gound up. LS engines generally only run 24-26* of total timing. Also have aluminum heads that doe not require much timing. Its hard to make them knock. While it is technically a small block, its not a traditional small block.

 

Long story short you just proved why its better to keep them slightly on the cool side. It keeps the WOT fuel a little richer and the AE a little richer with no ill effects. I have never been around a TPI engine that didn't pickup up 1-2 tenths at the track by keeping it under 180*F, preferably in the 140-170*F range. Also the cooler you can keep the intake runners the better.

 

This was a datalog of my 350 Vortec Express on a 95*F day, stock engine calibration, stock 195*F thermostat, stock clutch fan, running it very hard. Peak knock retard was 2-3* and it was only running about 24* total timing.

 

Ok well what's this mean?
Rich/Lean O2 offset at 16 counts between 20°C (68°F) and 92°C (197.5°F)
Just curious as to if it adds fuel when between 68F and 197.5F or if it leans it out?

I would guess it makes it richer but im not really sure.

 

Running it cooler makes it slightly richer, but that is not a bad thing because the intake runners in the head, the intake base, TPI intake runners and plenum stay cooler, which results in greater air density. Running it cooler just makes it run like it does before it is completely heat soaked. You know that punchy cool weather morning feeling.