Ok, I have the predator which will allow me to change my fan on/off settings and I'd like to go with a cooler thermostat.

Any reason not to run a 160? I see most folks run the 178 on the Corvette.

TIA.

 

Tom I have a 160 T-stat and have my fans turn on early via my Predator.What I have heard that a 160 in a cold climate might not let the engine get warm enough....but I don't have that problem here in Miami.My car runs 176-178 on the highway in 90+ heat.

 

Thanks,

I ran a 160 in a Mustang and there were some folks who claimed that didn't get the EEC-IV (Ford's PCM at the time) out of cold-startup mode and into closed loop. I don't think that was true, and the GM PCM is very quick to get into closed loop so I don't believe that is a concern.

Where did you get your 160?

TIA,

 

It's a Hypertech and I got it from Shawn @ LAPD

 

GM Product Performance has been saying for over 20 years that higher jacket temperatures reduce ring and piston friction, which shows up as more power at the brake.

Aluminum engines, in particular, should be run as hot as possible because the higher themal conductivity of aluminum and low jacket temperatures will pull a lot of heat out of the engine, which will reduce power.

The greater power produced by hot engines can be offset to one degree or another if the combustion air is heated up in the inlet tract, but the Corvette's composite manifold is pretty well insulated, so as long as the car is moving, a hot engine is better.

I think the myth of low temp thermostats originated with drag racers from between runs heat soak that heats up the manifold and inlet ducting, which transfers to the inlet air on the next run and reduces power.

Duke

 

Sir Duke,
So.............
Are you in essence saying the 178* would be a better choice, or there is nothing to gain at all from a lower temp TSAT..?.
With the caveat, of keeping the IAT's as low as possible?.( through a CAI I am assuming?). :confused:

 

Although I don't know all that much about it, I'll ring in with Duke on this one. I think it's easy to go overboard trying to reduce temps in an engine designed to run hot. If you really run your car hard and are experiencing temps you feel are excessive, and you never drive in cold weather, then maybe going to a cooler 'stat makes sense. There's got to be a point of diminishing returns, however. What if someone offered a 130 degree 'stat? Would that be better? Why not just remove the thermostat altogether?

 

I believe that keeping the OEM 195 thermostat is the way to go, and if you don't want to see the temp go up to close to 230 before the fans engage in warm weather low speed traffic, set the fan(s) to engage at about 210 to 215.

As long as the car is moving at at least 30-35 MPH a lower temperature t-stat is may actually loose power, so for normal driving or track hot lapping the OEM t-stat is best. For drag racing and dyno pulls there may be some advantages to a lower temperature t-stat to reduce the amount of heat soak and keep IAT at lower levels when there may not be cold ambient air reaching the airbox inlet due to no airflow over the car because it's not moving.

Here's an enlightening test you can run. If you hot lap or do dyno pulls feel the inlet manifold after you come back to the paddock or after the last pull. You should find that it is cool to the touch even though the coolant and oil may be well over 200. Due to the thermal isolation of the inlet manifold and the considerable volume of air flowing through it at WOT it will not get hot!

Back in the late eighties I ran an event with POC on the long course at Riverside with my Cosworth Vega. It was July and over 100 degrees. Due to a clogging radiator the car was running hot - about 230, but it never ran better, and it pulled 6200 in fifth down the backstraight or about 122 MPH - not bad for a two-liter engine in a 2700 pound car. Also, the aluminum manifold is always cool to the touch after a hot lap session.

BTW, for track sessions I rig up a "ram air" system through the headlight bucket. I wonder how much power that adds? ;)

Duke


Duke

 

Duke,

I have to tell you I have heard EVERY imaginable scenario on the cooler thermostat issue.

I have heard that the engine makes more power when it is hotter because you aren't wasting energy by putting that energy into the water in the form of heat, then sending the water to the radiator and throwing away that energy. I never quite followed that one, although it has a neat ring to it. :)

I have heard that hotter makes for thinner oil. Yet some people say that multi-visc oils still stay thick at high temps.

My observations are that oil pressure DOES drop at higher oil temps, whether it is multi-visc or not, BUT water temp and oil temp don't have that much to do with each other.

I have heard that hotter makes for tighter clearances and the engine is HARDER to spin when it is hotter...

I have heard that cooler H20 temps lead to cooler IAT temps and that means denser air and more hp. But my playing with the predator and observing IAT's makes me think that once you get a little air circulating under the hood, IAT's get real close to ambient with the stock thermostat.

But here is the reason I have always understood the cooler thermostat to help:

Detonation. If you cool the heads, you are less likely to pre-ignite the air/fuel mixture. Run the engine at a cooler water temp and you can push the limits inside the cylinder and increase cylinder pressures - thus increasing hp.

I'm wide open to the discussion though - any thoughts?

 

Well, the current radiator won't keep the car that cool no matter what stat you put in it. The real downsides to running without a thermostat are taking longer to warm up, more time with bad emissions and more wear on the engine from running under cold conditions.

 

Duke,

Is it 230 degrees? If so, folks, isn't there some possibility the factory knew what it was doing? Also, it seems to me that in stop and go traffic, my engine actually runs cooler with the air conditioning on...is that because the fans come on at a lower temperature?

Thanks for any and all advice. This subject makes me nuts.

TT :crazy:

 

>If you cool the heads, you are less
>likely to pre-ignite the air/fuel mixture.
>Run the engine at a cooler water
>temp and you can push the limits
>inside the cylinder and increase
>cylinder pressures - thus increasing hp

Problem is how are you going to increase the cylinder pressure?


>The real downsides to running without
>a thermostat are taking longer to warm up,

The TStat does not really determine how long it takes for a car to reach its operating temp, but it does change the operating temp if the rest of the cooling system is up to the task.

Put a 160 degree TStat or a 192 degree TStat in the car. When you cold start it will take the same exact time to reach 160 degrees. Both stats will be fully closed when they are under their opening temp.

 

Where is that heat going? Into the air you are sucking into the engine, right?

I'll admit, I'm not 100% sold on a cooler thermostat. And I'd like to explore the issue further.

 

Advance the timing. Which, depending on your point of view would happen as follows.

If you are in the summer and you are running your a/c, you could very potentially get pinging at WOT. The air entering the engine is already hot, and the extra load of the a/c isn't helping.

So, the PCM starts pulling timing. BUT, if you have the cooler thermostat, it may keep you from getting the pinging, giving you your timing back.

Or, you could run a cooler thermostat, and advance the timing a little with a predator or LS1-Edit type device.

Note, I said "not running a thermostat" which DEFINITELY is a determining factor in how long it takes for the car to reach its operating temp.

If you are running a thermostat, then you are recirculating water back through the engine WITHOUT running it through the radiator UNTIL it reaches the thermostats operating temp. Then it slowly opens, and lets some of the water, and eventually all of the water, circulate through the radiator - opening and closing as necessary to keep the water at the desired temp.

Not running a thermostat at all lets the cold water circulate through the radiator from the moment you start the car, thus delaying warm up of the car.

Correct, but as I said, I was referring to NOT running a thermostat - which is of course, different.

 

I've already told you about 3 times that advancing the timing on a stock 02 Z06 (or even a car with an airbox mod) is not going to do squat except generate more Knock Retard. Accept that. For some reason you just do not listen to me or you just do not believe me and then you keep asking the same questions. You wonder why I am not so quick to keep sending you explanations and reasons for my results? You keep making me repeat myself and you are wasting my time.

Just because an engine can take more timing that does not mean it will make more power with more timing. If you are looking for more power with more timing then you are definitely looking for more power in the wrong area. On a similar note, just because an engine can be leaned out that does not mean that it will make more power if you lean it out. Changes in timing and A/F ratio need to be tested on a wideband dyno (wideband before the cats) and with a proper OBDII data-logging tool before and after changes are made. FWIW, you will probably build power if you enrichen the low-RPM areas of the A/F curve. If you doubt me please ask WA2FST. You cannot expect to build power just by advancing the timing and leaning out an unknown mixture. That is why the out-of-the-box Predator tune and the older Hypertech HPP do not make much sense.

I know of at least 3 people besides me that have dyno tested more timing and everyone has gotten a 0 HP gain. Ask WA2FST, Reboot, and McRat.

You can see some of McRat's tests here:
http://www.zz0066vette.com/forums/sh...threadid=20818


Wa2Fst & Reboot here:
http://www.zz0066vette.com/forums/sh...threadid=24833


Reboot here:
http://www.zz0066vette.com/forums/sh...threadid=21383

Change zz0066 to z06 in the above URLs


Here are some dyno runs for McRat:




Since the very beginning of our conversations I’ve been stressing the fact that instead of researching this stuff in books and on the WWW you will learn a heck of a lot more if you just run the car at the track and put it on a dyno with a good data-logging tool and a wideband (before the cats). I still stand by the statement and I guarantee that the results will surprise you. No disrespect intended. :)

 

MAN.......
Something is screwed with this post....... :confused:
I just got 12, count em' 12, notifications of this one post........ :mad
I come to the site, and there is ONE .......... :mad
I thought rb had lost it!!!!!!!! :lol: :lol: :lol:

 

I believe the question was, "if you cool the cylinder heads by using a lower temperature thermostat, how could you then increase cylinder pressure to take advantage of the lower likelihood of knock."

If you lower the cylinder head temps, then you are less likely to encounter
Knock Retard, and then you could potentially advance the timing.


Actually Ross, while I addressed my initial question to everyone, I don't think I asked you ANY questions in this thread. You just hopped in here and hopped on me. I'm not sure why.

I'm really thick skinned, and I don't care what you say about me or to me here. But I honestly don't see where the personal attacks are needed.

While I don't know if I agree with Duke on the cooler thermostat issue, (and my jury is still out on it right now) I don't think you will see Duke and I pounding on each other like that. It is possible to disagree with someone without - in so many words - calling them an idiot.

Maybe we are on different pages here. I understand that you do not think that advancing the timing will help improve performance because you think it will cause Knock Retard to kick in from the PCM.

However, in this discussion, we are talking about reducing head temps by running a lower temp thermostat - and the possibility that you would then be able to advance the timing without encountering KR. That is a different discussion than "just advancing the timing."

As a general rule, a four stroke internal combustion engine at WOT runs best with the timing advanced to the point just before it experiences detonation, particularly at higher rpms.

You are trying to build maximum cylinder pressure.

Almost without exception, that maximum pressure is going to be the highest amount of advance you can get, without getting detonation or pre-ignition. Because if you over-advance, the pressure wave will reach maximum BEFORE the piston reaches the top dead center mark, and the pressure wave will push down on the cylinder with the most force BEFORE it reaches TDC.

Advancing the timing is not as big a deal at 2,000 rpms. The piston is travelling up the cylinder at about 240 inches/second. With the stroke of the engine being 3.62 inches that means it is taking the piston about about .015 seconds to travel from the bottom of the cylinder to the top of the cylinder on the power stroke.

Since the gas (air/fuel mix) takes a finite time to burn we have to fire the spark BEFORE the piston reaches the top of the cylinder. At low rpms, we can fire the spark fairly close to the point where the piston reaches Top Dead Center.

As the engine picks up speed, the amount of time that the fuel takes to burn remains constant, but the amount of time it takes the piston to move up and down the cyliner is much shorter. At 6,000 rpms, the piston is travelling 724 inches per second. Now it take 0.005 seconds to travel to the top of the cylinder (1/3 the time as before). So the spark must be fired while the piston is lower in the cylinder than at 2,000 rpms in order to allow the same amount of TIME for the fuel to burn and achieve maximum pressure.


So, if we can cool the cylinder heads, we can possibly squeeze an extra degree of advance out of the engine without getting detonation.

I am aware that there is an ideal air/fuel mix at WOT and going leaner than that ideal mix will result in less hp. That number is around 12.6-12.8/1. However, it is a general rule that manufacturers run their cars a tad bit rich at WOT because it reduces temps in the cylinders and that lessens the chances of detonation, and it also decreases engine life.

The idea here is two-fold:

1. If you are running a lower temp thermostat, then you can run leaner without increasing the cylinder temps as much - avoiding detonation.

2. The factory is playing it safe and there is a little room to squeeze out a bit more hp by leaning it out a little.

I hope the predator is not trying to improve my low-rpm power, or part throttle power. I hope all they are doing is modifying my WOT data. I don't care about low-rpm power. The car has enough driveability. I just want the most hp the engine is capable of making at WOT.

Wes has told me he believes in wideband dyno testing. You'll also note he runs a cooler thermostat though...

I'm not looking to make radical changes to the air fuel mix. Just lean it out a little bit at WOT. It should be a fairly known a/f mix that the factory sets the car at for WOT operation. All Diablo has to do is test several Z06's on a wideband and see what the a/f ratio is, then adjust their tuning to achieve closer to ~12.8 than the factory was getting and they should see some hp increase.

Ross, you have a distorted view of me. You can ask Wes whether I race, and test, my cars. I live in a drag-racing challenged portion of the United States right now. We have mountains and curves and they are a blast, but they aren't conducive to 1/4 mile drag strips.

When I was in Florida, I raced 1/4 mile at Bradenton, Sunshine (1/8th in St Pete) and Orlando quite a bit. Advancing the timing isn't out of a book. Its from experience AND knowledge of how the engine works.

I believe if you advance the timing while cooling the cylinder heads, there may be some hp to be found.

Now I will ask you a question: Have YOU advanced your timing and tested on the track or a dyno?


[Modified by Tom Steele, 10:11 AM 11/1/2002]

 

Ok you guys ... go to your corners. :) JK of course.

Tom, why not just pick up a couple of the cooler tstats (a 160 and a 178) and give it a try. All the theory in the world means nothing without empirical data. It's a cheap and easy swap. let us know what you find out. :cheers:

 

Looking at this one, here are some of the pertinent quotes I see...

Wes says that he added 30# injectors and that by using the MAFT and airbox, he got a total of 13 hp.

"Airbox and MAFT tuning was worth 13rwhp, injectors/tuning added another 8. "

Now do you think he ENRICHENED the air fuel mix to get the improvement? I'm pretty sure he adjusted the MAFT to get the WOT mixture a little leaner than factory.

As for TIMING

"The reason adding larger injectors seemed to help, though, was b/c I could dial in less load and this had a positive effect on WOT timing (from what my datalogs showed). Timing seemed to stay at 25-26^ longer in the rpm band (up over 5000rpm) whereas normally it would just stay at 22^. "

This is really similar to the old MAT sensor trick, where the air temp sensor is moved to a cooler portion of the intake tract, and fools the computer into advancing the timing. By fooling the MAF, it thinks there is less load on the engine and advances the timing.

 

>I understand that you do not think
>that advancing the timing will help
>improve performance because you
>think it will cause Knock Retard to kick in from the PCM.

No, I said that advancing the timing just will not provide a power gain. I said that the only thing you will get is KR signals. Even if you do not get KR signals you will not get more power. This is true even if you reduce operating temps. McRat's dyno runs I posted above were done with a low temp thermo and earlier fan programming.

When Wes ran with his MAFT he was never able to just test 26 degrees TA against the stock 22 degrees TA because that is impossible to do with a MAFT. He just assumed that the extra advance was providing a power gain and he was wrong. Every single person that has tested extra advance at WOT on a stock (or airbox equipped ) 2002 Z06 has found a gain of about 0 HP.


>As a general rule, a four stroke internal
>combustion engine at WOT runs best with
>the timing advanced to the point just before
>it experiences detonation, particularly at higher rpms.

You have to stop with the general rules/keyboard mechanics and actually test the particular car. You are assuming too much about what is really going on.


>I believe if you advance the timing while
>cooling the cylinder heads, there may be
>some hp to be found.
>Now I will ask you a question: Have YOU
>advanced your timing and tested on the track or a dyno?


Yes I have tested, no gains found. Yes I have a 172 degree TStat in the car. Other members have tested advanced timing with reduced coolant temps, no gains from the timing. Have YOU tested it? What do you consider to be a good gain, 1 HP? You are definitely looking for power in the wrong area. I can believe that some small part throttle cruising gains may be gained from slightly advanced part throttle timing, but on a stock 2002 Z06 22 degrees TA at WOT is as good as it gets. Once you start to modify the car this can change.


>Now do you think he ENRICHENED the air
>fuel mix to get the improvement? I'm pretty
>sure he adjusted the MAFT to get the WOT
>mixture a little leaner than factory.

You cannot just assume that leaning a factory car is going to produce a significant power gain. You have to check your current A/F curve and then decide how much of a change can be safely made. If you are expecting a significant increase in power you would need to make a pretty significant change in the A/F ratio. It would be pretty dangerous to do that without wideband testing and a vendor like Diablo would be crazy to put a significantly leaner than stock ratio in their standard box. The stock PCM tuning determines what A/F ratio the PCM shoots for at WOT but in the real world the PCM has no idea what the ratio really is at WOT. Production tolerances can make every car different and some cars may come from the factory with a stock WOT ratio that is already leaner than other cars. If Diablo was attempting to lean cars enough to get a significant power gain they would risk damaging cars that are already coming out a little leaner from the factory. I don't think that you will ever find a pro dyno tuner that just leans a car before checking its current state of tune.

If you want max area under the entire curve (instead of just a good peak number) some areas will probably need to be enrichened and some areas will probably need to be leaned. In addition the changes will not consist of an equal shift at all parts of the A/F curve. Some areas of the A/F curve may require different changes than other areas. Every car can be a bit different so there is no blanket answer. If you want the best overall gain the PE must be adjusted for each individual car. Downloading a generic "performance program" is not something that I would expect to get much power from. How much power did people get from those old Hypertech units? If you tune your car on a dyno with a wideband and a good OBDII scanner then I would expect bigger gains. You would probably get gains similar to what people are getting when tuning MAFTs on a dyno.

I thought we were already discussing this same subject at the bottom of this thread a few days ago:

http://forums.corvetteforum.com/zerothread?id=418355

That is what I was referring to when I said that I was repeating myself. I apologize if my last post came across as a personal attack.

:blueangel:


[Modified by rbartick, 8:34 AM 11/1/2002]