No thermostat on an L28 - Pinks Z

[Thumper]

Again, not my experience. My Toyota truck had to be run without a thermostat when the thermostat failed (just for a day or two). It had an aluminum radiator and the needle would get maybe 1/8" off of full cold, max.

 

One of my friends with a Z with a brass radiator thought her car made more power without a thermostat. I had to convince her otherwise after her driving for months like this. Her car also would barely register any temp at all.

 

We both lived in LA, so there was plenty of traffic involved in both situations.

 

Hmm interesting. One thing I just thought of is that my se-r it idled at 1000-1100rpms because of cams so the water pump was moving alot faster than say a v8 (or a stock car) that idles at 600 rpms. Also the radiator was 10yrs old and the oem thin one at that.

 

Btw "83 HKS L28ET" interesting place you live. My my friend at one time Mike moved to miami. He drove a light blue 280z with a l28 turbo. Hey if you meet him say wuz up for me.

[dskubitz]

My old 260z would over-heat (230-260) all of the time. I took the thermastat out and found that the engine would still run around 240, it would just take longer to get there. Then I changed the radiator and presto, the engine never got even close to the mid range.... until I added the thermostat. I never saw an engine overheat without the thermostat in.

[Tony D]

Want a good explanation on why you WANT to run a thermostat?

grapeaperacing website has an extensive article on the micro-spot boiling in the head...

 

While you may 'not overheat' on an anecdotal level, what you are doing to the head, and the rest of the engine without a restriction at that point is not good, and the article referenced explains it very well. Someone else can find it again, it was in the 'favorites' of my old laptop, but no backup when it crashed... so the search is up to you!

 

The adventerous will link it here as well...

[Mr.INSANE]

If the L series really ran hot Nissan would've done something. But the entire S30 and S130 Run had Viscous fan's they never changed the design.

 

Although I remember Nissan supplying different hoods for overheating 240z's along time ago

 

Timz: How did the CSR water pump work for you? Worthwhile investment. Ive not heard anything really good about them so far.

[Daeron]

http://www.grapeaperacing.com/GrapeApeRacing/tech/coolingsystems.pdf'>http://www.grapeaperacing.com/GrapeApeRacing/tech/coolingsystems.pdf

 

And the home website, http://www.grapeaperacing.com appears to have more information and reading material. Thanks, TonyD!

[Pyro]

a copy/paste from I don't remember where.........

 

 

 

What some people will say in public. This is absolutely false, of course. Try to conceive of blowing on something hot, say a spoonful of soup, first slowly and then more rapidly. Which cools faster? For extra credit, try imagining the same spoon with first slow and then fast water moving across the bottom. Sheesh!

 

The issue with running without a thermostat is two-fold. The first part is that the thermostat provides drag on the water flow. This drag increases the backpressure the water pump and all of the enginesees. This additional pressure, over and above the nominal 15 psistatic pressure the radiator cap sets, raises the boiling point of the coolant. The reason this is important is that it suppresses localized film boiling at hot spots such as around the exhaust port. The transition from nucleatic boiling (bubbles of steam originating from irregularities on the surface) to film boiling (where the hot surface is coated with a film of steam) is called Departure from Nucleatic Boiling or DNB. DNB is very bad, for steam is a very good insulator compared to water. Once DNB occurs, the area under the steam gets hotter because the steam doesn't remove very much heat, adjacent metal which is still wetted heats from conduction. DNB happens there. The process spreads until substantially all the coolant-wetted surfaces are insulated by a film of steam. The engine overheats. In addition, the buildup in steam pressure forces the radiator cap open, bleeding coolant, therefore making the situation worse.

 

The second issue is that of water pump cavitation and surge. If the pump is operated at high RPM with insufficient head pressure(provided by the frictional losses in the coolant passages and the thermostat), there is a great likelihood that the pump will either cavitate (localized boiling and/or degassing on the impeller) or surge (an unstable flow regime). Either phenomena is destructive. Cavitation's collapsing bubbles act like little sand blaster, eroding away impeller material. Surge can do the same thing and in addition, can vibration stress the impeller enough to break it. Many times what looks like corrosion damage to the impeller, especially when the housing is damage-free, is actually cavitation damage.

 

The myth of velocity originated among those unschooled in physics or thermodynamics, I suppose, because a common racer "solution" is to press a fixed restriction into the thermostat housing neck when no thermostat is desired. The conventional (but wrong) wisdom is that the restriction "slows the water" as stated by the previous poster. In reality, all it does is provide some more dynamic pressure in the block by restricting the flow. The exact same result could be accomplished (assuming the water pump doesn't surge or cavitate) with a higher static pressure (cap pressure), assuming the system could withstand it.

[TimZ]

Timz: How did the CSR water pump work for you? Worthwhile investment. Ive not heard anything really good about them so far.

 

On my car, it couldn't keep up. I tried several different options, including running it on a Kenne Bell boost-a-pump and bumping the supply voltage when the water temp got above 195 or so. No help.

 

I've since gone back to the mechanical pump and viscous clutch fan - it's dead simple and reliable and I no longer have overheating problems. On my last set of dyno pulls, the water temp never exceeded 195, which is the t-stat setpoint. That never happened with the electric setup.

 

I was bummed that the electric pump didn't work well enough for me, as I really liked being able to run the pump after shutting the engine down.

[Mr.INSANE]

On my car, it couldn't keep up. I tried several different options, including running it on a Kenne Bell boost-a-pump and bumping the supply voltage when the water temp got above 195 or so. No help.

 

I've since gone back to the mechanical pump and viscous clutch fan - it's dead simple and reliable and I no longer have overheating problems. On my last set of dyno pulls, the water temp never exceeded 195, which is the t-stat setpoint. That never happened with the electric setup.

 

I was bummed that the electric pump didn't work well enough for me, as I really liked being able to run the pump after shutting the engine down.

 

It would be really neat to have it set up like you mentioned, except keep the speed of the pump with the motor.

 

What do you think the problem with the pump is if you have any idea's could be that the pump motor getting hot heats up the water or something.

 

i want to see someone hook an electric motor up to just the stock water pump like some v8's setups so its belt driven but not by the crank.

[Tony D]

i want to see someone hook an electric motor up to just the stock water pump like some v8's setups so its belt driven but not by the crank.

 

Been Done, our Bonneville car has been running the Summitt Racing V-8 universal electric water pump kit since 1999. Simple hookup, it works. Just not as pretty as the CSR Pump Setup.

[(goldfish)]

a copy/paste from I don't remember where.........

 

 

 

....boiling point of the coolant. The reason this is important is that it suppresses localized film boiling at hot spots such as around the exhaust port. The transition from nucleatic boiling (bubbles of steam originating from irregularities on the surface) to film boiling (where the hot surface is coated with a film of steam) is called Departure from Nucleatic Boiling or DNB. DNB is very bad, for steam is a very good insulator compared to water. Once DNB occurs, the area under the steam gets hotter because the steam doesn't remove very much heat, adjacent metal which is still wetted heats from conduction. DNB happens there. The process spreads until substantially all the coolant-wetted surfaces are insulated by a film of steam. The engine overheats. In addition, the buildup in steam pressure forces the radiator cap open, bleeding coolant, therefore making the situation worse.....

.

 

 

It also let a hand covered in cold water to be dunked in molten lead

[icarus]

stumbled across this old thread while searching, for something completely unrelated actually... but i digress;

 

i unintentionally ran one of my L28ets in my s130 without a thermostat for several months due to the PO not having one installed for some unknown reason. it would take a long time to warm up and would never quite reach an acceptable operating temp. it was when i opened her up to install a 195F thermo i had picked up to hopefully cure the problem that i discovered that it had not had any thermo to start with.

 

also, i have heard horror stories of people actually breaking things in pistons due to running with no thermostat. cruising down the freeway in the icy winter with no thermo can cool your motor down pretty quick. and some have reported massive damage due to cold piston slap. i believe they were running forged pistons in the rig, which would exacerbate the problem of course, as well as make it much more costly. i dont know if they were intentionally running no thermo for their "racecar" or if it was just neglected in reassembly..