quote:

Originally posted by banjo:
Just curious, what is the reasoning behind not using a thermostat?

You can circulate water all the time making the water temp more consistent.

One factor not discussed is engine oil temp. Once you get a good heat soak in the engine and the oil temp is up, water temp. becomes less of a factor to a certain degree.

Regarding under hood temps vs. fresh air, one needs to consider that if you have a cowl hood, or no inner fenders with a grill or both, you're still going to get a majority of outside air coming into the engine compartment and circulating or pushing that hot engine compartment air out of the engine compartment.

Another thing to consider is that if you run a higher, consistent engine temp. it's going help to equalize the temperature of the air intake charge when using fresh air unless there's a major variation in ambient air for the day.

Either way, establishing a lot of data will make either combination predictable.

The way I look at it, running a thermostat will easier to maintain consistant water temp. It's going to only increase circulation when you need it. This way you have cooling capacity within the radiator for when you really need it. For example, with no thermostat, the entire cooling system will be at engine temp. For some reason you have an extended run time or hot lap, it will tougher to cool because everything is hot. Now go to the same scenario with a thermostat. As you bring the engine up to operating temp, thermostat is closed with minimum coolant flow. The radiator is now a reservoir of cooler coolant, so when the engine gets to the thermostat temp it start to move coolant and will be more effective at controlling,maintain temp due to the temperature differential. I have been running a thermostat a long time. I have a couple of holes drilled in it so there is always some coolant flow because I dont want to shock it. Further, it easier to warm up because you are primarily heating up the engine coolant.

In my experiance with vs without, I had to run the engine more to maintain a consistant temp without one which is why I decided to try one. My philosophy is to have excess cooling capacity and taper it back to what is actually need to maintain temp. I also do this with my transmission fluid. I guess the bottom line is what works for you.

Definitely agree with running the engine at 180-190 especially when the outside temps are hot. I don't think a lot of people get this one. It's all about temperature differential.

Are you're talking alcohol Bill? What temp thermostat do you use? I try to leave at 150 with my gas burner.

Bill, you run alky, so what happens when you're staging, engine water temp is just getting up to your thermostat temp, then right before you launch the thermostat pops open and rushes that cool water into the block/heads?

Yes, still on alky,I like it around 185-190, thermostat just doesn't pop open, it a gradual thing. It's going adjust how much coolant is passed based on the temp of the coolant it sees. According to stant, it starts to crack open 3-4 degrees before the set point and is fully open 15-20 degrees above the set point. So it's going to adjust gradually based on the coolant temp. I build between 8-10 degrees going down track, so it never fully opens. It also helps to build heat quicker.

Just curious where do you all keep you coolant temp sensor, I have mine in the intake, but was thinking it may be better to have it in the head due to coolant flow.

I've watched the temp gauge drop after reaching 185 plenty of times, but that was probably with a belt driven water pump.

I run an electric pump and a logger, and haven't seen any significant swings in temp. Few degrees maybe.

Like Banjo I run a thermostat in the intake with some 1/8" holes drilled in it to allow some circulation and to help get air bubbles out.

In addition to that I run a thermostat on the electric fan for same reasons. My fan is controlled by a switch on control panel so I can turn it off when I want to build heat like at end of day.

I have electric water pump and small Honda radiator. The thermostat on intake opens about 170* and fan comes on about 180* water temp does not move much. At end of day I turn fan off and toggle water pump off and on until I get water temp up over 200* to evaporate and pull moisture out of system.

I have a very large Moroso double transmission cooler that cools really well, I am thinking of adding an inline thermostat on it to direct cool fluid back to transmission and through cooler as it gets hotter.

What all of this means and how it relates to original post here is consistent temperatures helps to make a consistent car. As for external air or under hood air it has been discussed before and never really got same answers or definitive answer on it on performance or consistency. It may have much to do with individual set up. One system may help bring in cool air while another may also give it a "Ram air" effect at higher speeds. Both of those things may increase performance a little but make it change more with weather? Who knows?

Good thread on operating temperatures guys. As far as water temperature control, we have been using an older Davies Craig 8001 water pump and fan controller with their EWP 150 water pump.The controller modulates the EWP speed to bring the motor up to temperature then runs the fans as needed to control the set max temperature. We also run methanol so keeping the heat up is important.

https://daviescraig.com.au/swi...-controllers-fan-ewp

Tom

quote:

Originally posted by banjo:
Just curious, what is the reasoning behind not using a thermostat?

We had this discussion a while back on cowl hoods , fresh air etc?? Just shutting the door on my stock cowl picked us up .02 and .5 mph. That’s a big gain! We run a two row 6 cy stock radiator with a .675 restricter ( no T stat) in the bottom hose. Has a 1300 cfm fan, never gets above 150-60. Pretty efficient. I also have a filled block 1 inch down from deck. Cools down extremely fast too.

On my '69, I have a Buick GS forward facing scoop sealed to the hood. The car is predictable.

On the '81, stock flat hood, first year with it ran an air pan sealed to the cowl. The car was also predictable.

I took Bud's class last season, and tried without the air pan, strictly underhood temps. The car was much more consistent, in addition to being predictable. What he says about the 80% accuracy for a prediction was definitely true for me.

quote:

Originally posted by Larry Woodfin:
This is an experiment and I will post results in a few weeks.

Larry, clue us in, please; how is that cold air intake setup working for you? It looks like an S10 truck with a Spectre carb hat.
Thanks!
Troy

So let me ask this, when using a ET predictor or a Kestral 4250 how do you adjust for the under the hood air temperature difference verse the ambient outside air temperature the weather station is reading?

quote:

Originally posted by 69427:
So let me ask this, when using a ET predictor or a Kestral 4250 how do you adjust for the under the hood air temperature difference verse the ambient outside air temperature the weather station is reading?

You don't. The underhood temperature won't change. I've seen 25° ambient temperature swings with only 2°-3° underhood temperature change.

quote:

Originally posted by Larry Woodfin:
This is an experiment and I will post results in a few weeks.

Any results?

I sealed the hood to the toilet early last spring before running. Previously the scoop was open underneath, allowing underhood air to the engine. I don't have a full datalogger so I don't have ALL the data, but I have watched the pressure in the intake manifold with a home-made tool; and of course coolant temps. With the hood/scoop open, it sees about 0.07"/hg at the finish line based on what little data I could get. This is at 180° coolant temp and MPH at the finish line of 119. Then sealed it all up, and it's really sealed well. Same MPH I am seeing 1.62 psi. Engine goes a little lean and I can't get enough fuel to it to compensate without changing the pump and possibly playing with the injection even more than just the pump (toilet).

BUT...the car is now inconsistent which is probably due to slight lean issue. Also when the air is blowing in my face (going down track) the pressure will go a little higher. In the middle of hot sticky summer, it will be lower. If there's a cross wind and the car beside me is "just right", it'll affect the pressure a little too. The wind is unpredictable. Underhood air isn't as unpredictable.

I'd have figured that with 1 psi+, it would pick up some MPH but there are quite a few other variables at play too.

I’ve also been inducted into the under hood air process. Pun intended. I was so thrilled about it I started to figure out how to pull the air from the ****pit! <<< U can’t say penis. As far as a thermostat is concerned why not install 2 gauges in best spots to clear up any confusion. Hell, why not 15! I would tell you where BUD I would have to kill you.

This always seemed to be an issue for no matter what I did. Running with no hood (didn't like) it was an easy way out, but I made it work for too many years. I even had issues with the new car in 2019 & ran without the hood. We had tried just running the hood (no air pan) & tried using an air pan to pull cooler air. I didn't like the results.

2020, I decided I was going to run with a hood & make it work. This thread & one other gave me some other ideas. It was a combination of procedures/parts that finally made it work for me to run a hood:

Cold air pan with air coming from the grill. The bottom of pan has thermal barrier material applied.

Higher engine temp, not removing hood between rounds & not over cooling motor between runs.

Installed a pieced together carburetor: QF 1050/4150 main body with annular boosters, old HP 1000 metering blocks/base plate & a set of XP fuel bowls. The carb works really well.

The car has got me into the money 6 out of 7 races this year. The car is flat out deadly & is definitely making the driver look good! There's one other thing making it work good, is the Mickey Thompson PBRs.