I posted earlier that I was going to sell my truck and buy a relative's low mileage Chevy. That has fallen through, my evil aunt decided she wanted the truck and took it without paying anything. That's the bad news. Good news is I would've missed my truck and it looks like I will be keeping it for a while now. At least until the tranny starts acting up, then it's gotta go. lol

Anyhow, on to the question at hand. When I did the plenum, Hughes recommended a 180 degree thermostat, which I installed. I have no mods (exhaust and drop in high flow filter only). I have seen a couple of folks (Z-man the plenum master, for one) say that if you are not getting a tuner to keep the stock 195 degree t-stat. What are the negatives of the 180 degree t-stat in a stock motor? Is it worth the trouble of changing back to the 195? Will I get a little better mpg's maybe with the stock t-stat or what? I average about 12.5 mpg now, 4 X 4, 360.

Thanks.

 

in as tight a response as possible:

the 195 will allow better mileage.

the 180, as you have it, fools the PCM that the engine is running cooler, and cooler engines need more catalyst (fuel) to positively ignite- so, you run rich- which eats at your economy, and whittles at your power, but gives you the impression of having a smoother running engine.

180 WITH a tune, allows the programmer to advance spark and pull fuel.. leaner engines produce more power, and run cleaner.. advancing spark on a cooler engine is possible as it knocks a little threat off the possibility of pre-ignition (aka pinging) when the engine is as lean as it can be, cool as possible, and a few degrees closer to TDC.. all that combined, makes a more powerful BOOM on the power stroke, and sends more ponies to the terra. ..

without a tune for the 180, your wasting gas.. and your running rich which hurts o2 sensors and cats..

 

Just had an interesting conversation with Kevin at Hughes. Asked him what's up with their recommending a 180 t'stat; not too sure I thought much of his answer.

He said that they recommend it because "most of the guys who buy their plenum kit tell them the truck runs smoother/better with the 180".

I asked him about the fact that the computer will be giving the injectors more fuel, and that a lot of the guys here say that will be just wasted fuel if you can't tune the computer to reduce the fuel back down, and advance the timing a little. He replied that "the computer will adjust the air along with the fuel".

I told him "no way, Jose", that the computer can't control the amount of air, and just has to work with the amount you've got entering the engine. You're going to be running somewhat rich, period.

He said, "well what are you looking for, power, or fuel economy"?

I replied that I didn't see how running a mixture richer than 14.7:1 was going to give me any more power, and that it seems to me that maybe the richer mixture just makes the engine run a little "smoother" because it ignites easier, or for whatever reason makes it feel like the engine is running "better". I allowed as how I could expect more power if I had more of a 14.7:1 mixture inside the combustion chamber, either with a bigger displacement engine, or with forced induction, but I don't see how I'll get more power by straying from the ideal stochiometric ratio of 14.7:1.

"Well, that's just what guys tell us, that their engines run better with the 180 thermostat".

Uh huh. What I take away from this is that they really haven't done their homework on this one, and that just as has been said here many times, don't use a 180 unless you have a tuner.

***

Afterthought: another reason they probably like to recommend the 180 is because there's no way in hell your engine is going to ping at 180 on a rich mixture, and customers are going to be more inclined to rave about how the Hughes plenum kit solved their pinging problem.

***

"Is it worth the trouble of changing back to the 195?" Yes.

"Will I get a little better mpg's maybe with the stock t-stat or what?" Yes.

"I average about 12.5 mpg now, 4 X 4, 360". I bet it would be 13.5 - 14 with the 195.

 

I was getting 13.5 mpg's w/4x4, 360, and i'm getting over 14 now

 

Our heads are ment to work with 180 , that's why they tend to crack because people run with 195

 

The heads crack because they were cheap castings. Decks were too thin.

 

I don't think a metal with a melting point of 2300 F. is going to give much of a crap about a difference 15 degrees; then again, I'm not a metallurgist, I just play one on the internet.


And I'm pretty convinced that a stock engine runs more efficiently at 195.

 

This is interesting. I have a Hypertech tuner and what I believe is either a bad original t-stat or a 180. I don't believe my Hypertech has the ability to advance the spark, unless its built into the tune and not an option they advertise. I'm doing the plenum/kegger/timing set/water pump within the next month or so and will be putting in a new t-stat.

By the sounds of it, I should be putting in a 195 Stant? Forgot to mention my truck does run a little cool and I live in the Great White North. (Canada)

 

you're gonna want that 195 for your heater up there..

if you want to split hairs, the engine closes loop somewhere around a sustained 120~140*... which is below the 'stats rating.. the biggest problem with running the lower 'stat is that it will continue to dump fuel until it reaches full operational temperature of around 195~205*.. It doesn't really trim until then, it just dumps..

the timing (that the PCM controls) is tied to several factors.. the o2's (in closed loop), the IAT, and the temperature as read by the sensor.. if the PCM thinks it can safely advance, it will.. I've read where the IAT can move 1.5* advanced or retard by itself, I don't know what the o2's and temp sensor can do, but I'd guess more than the IAT.. the problem is, it's NOT going to advance timing on a cool engine... it will hover near the scripted tables until it reaches a operational temperature where it can make a better decision..

the cooler stat will allow an unloaded engine to maintain a lower temp.. a loaded engine is another beast- and the operational temperature will not be based on when the stat opens and closes as much as other factors such as total coolant volume, exchange surface area, water pump volume and velocity, ect.. in other words, all the cooler stat does to a loaded engine is give it a head start..

something you said about running cool: richer engines run cooler, lean engines run hotter.. if you're habitually cool and all other things are consistent, you're likely running rich.. likewise, if you habitually run warmer, all things consistent, then you're likely running lean.. all things consistent= radiator, water pump, coolant, stat, and sensor health.. if you're just driving to work and such, and running that cooler stat on an unloaded engine, it will beyond doubt run rich because the PCM is attempting to make sure your engine continues to run by adding catalyst, and hoping that it warms up- and the rich conditions work against it achieving that.

 

My temp guage has NEVER gets above 95*C. Even on the hottest days pulling my trailer with ATV on it and the bed loaded down with camp gear. (read as "lots of beer") It usually sits at about 85*C. I really do think it is the stock 192 that the truck came with.

I drive a good 20 km's to work one way. SO it gets to operating temp almost every time I drive it. Best milage I have gotten recently was 13.5 mpg running 93 oct. (less pinging)