Radiator coolant additives

[Dave WM]

is the thermostat Nissan or aftermarket?

[Mark Maras]

13 hours ago, TomoHawk said:

Since the clutch seems to be the right size for the spacer, do you think it would hurt to leave it in there?

 I wouldn't run the flex fan with the clutch. I think the reduction in the number of blades would require the flex fan turning at full engine speed, especially at idle. I'm not a big fan of clutches. Everyone I've turned by hand has different resistance than the others. I measured my old flex-fan assy. The spacer is 2" and the fan is 3/4" from the 3 row radiator.

[Zed Head]

14 hours ago, TomoHawk said:

so I can cruise some race tracks. 

I think I will look into changing the stock fan to a flex-fan, but do you still use the clutch with the flex-fan?

Don't forget that the fan is for very low speeds and idling.  Doesn't have much effect once you're moving.  A full shroud would be a good next step if you don't have one.

[Chickenman]

15 hours ago, TomoHawk said:

( Snip ) I think I will look into changing the stock fan to a flex-fan, but do you still use the clutch with the flex-fan?

 

I wouldn't switch to a flex fan. Personally, I've never seen one that works as good as a stock fan on any car. Flex fans flatten out at high rpm. That's their design. While this initially seems like a good idea, as it reduces HP loss... it also turns the Flex fan into a very good airflow blocker to the radiator. Effectively a 17" Pizza Pan placed right behind the rad.  Plus they will slice your fingers or hand off in a split second if you make a mistake.. Plastic fans will badly bruise or even break a finger or wrist. But at least it won't chop them off like a guillotine!!!

What does work on the track is careful consideration given to radiator ducting. You want air pressure high in front of the rad and as low as possible behind the rad. Box in the front of the radiator to the grille so that the high pressure air is forced to go through the radiator.  The stock design has too much area in the nose for the air pressure to bleed off. A shroud on the fan is a must.  Make sure you are running the belly pan. That lowers coolant temp significantly.

Air stacks up in the engine bay at high speed and needs some way to get out. Consider adding hood vents or simply prop the hood open about 1" at the back . You MUST use hood pins if you do this. Don't rely on the safety latch!!! The hood opening idea is quite effective. We used to run our D Production Z's this way back in the late 70's early 80's. With good air management ( ducting and venting )  and a decent Rad, overheating should not be an issue in a Z under 90 - 95 F ambient. Above 90 - 95F ambient gets tuff on any car.  We ran a 160 degree thermostat and no fan at all on the race cars.

If you need a fan for street use and track use, the 7 blade 280Z fan with factory shroud and clutch is very hard to beat. Even some of the best electric fans have a hard time keeping up with the flow that a decent mechanical fan makes.  Mechanical fans can use a much higher pitched fan blade and a wider blade than electrical fans. It's all pure HP required to drive the fan.And it's all a compromise. Stop and go traffic in Downtown LA with the AC on is much harder on the cooling systems cooling ability.  than running 100 MPH on the race track

 

Edited September 27, 2016 by Chickenman
Added gory hand chopper details... saw it once in person. Still get chills.

[Zed Head]

The "splash board", as Nissan calls it, belly pan or splash pan to most of us,  is kind of a mysterious part.  It's not mentioned at all in the Cooling chapter, but the shroud is.  I've never seen any actual temperature measurements, but beandip does say his car handled differently without it.  Might be one of those assumptions that happen occasionally.  Maybe it's just for splashes.  Seems like Nissan would have called it a shroud and/or mentioned its importance if it was designed for cooling.  Who knows.

beandip, #3 here - http://www.classiczcars.com/forums/topic/21260-splash-pans/

Found this old article about overheating.  Actually has some interesting stuff that was covered here recently, on temperature switches and sensor resistance charts.

http://www.jrdemers.com/280ZX/overheat/overheat.html

 

[Mark Maras]

59 minutes ago, Chickenman said:

I wouldn't switch to a flex fan. Personally, I've never seen one that works as good as a stock fan on any car. Flex fans flatten out at high rpm. That's their design. While this initially seems like a good idea, as it reduces HP loss... it also turns the Flex fan into a very good airflow blocker to the radiator. Effectively a 17" Pizza Pan placed right behind the rad.  Plus they will slice your fingers or hand off in a split second if you make a mistake.. Plastic fans will badly bruise or even break a finger or wrist. But at least it won't chop them off like a guillotine!!!

What does work on the track is careful consideration given to radiator ducting. You want air pressure high in front of the rad and as low as possible behind the rad. Box in the front of the radiator to the grille so that the high pressure air is forced to go through the radiator.  The stock design has too much area in the nose for the air pressure to bleed off. A shroud on the fan is a must.  Make sure you are running the belly pan. That lowers coolant temp significantly.

Air stacks up in the engine bay at high speed and needs some way to get out. Consider adding hood vents or simply prop the hood open about 1" at the back . You MUST use hood pins if you do this. Don't rely on the safety latch!!! The hood opening idea is quite effective. We used to run our D Production Z's this way back in the late 70's early 80's. With good air management ( ducting and venting )  and a decent Rad, overheating should not be an issue in a Z under 90 - 95 F ambient. Above 90 - 95F ambient gets tuff on any car.  We ran a 160 degree thermostat and no fan at all on the race cars.

If you need a fan for street use and track use, the 7 blade 280Z fan with factory shroud and clutch is very hard to beat. Even some of the best electric fans have a hard time keeping up with the flow that a decent mechanical fan makes.  Mechanical fans can use a much higher pitched fan blade and a wider blade than electrical fans. It's all pure HP required to drive the fan.And it's all a compromise. Stop and go traffic in Downtown LA with the AC on is much harder on the cooling systems cooling ability.  than running 100 MPH on the race track

 

 Oh Yeah. There's no doubt that a flex fan would amputate a finger(s), but even with my track record, I have never injured myself with one. Same goes with a chain saw. I have a lot of respect for both. It's not the obvious things that bite me.

 Out of curiosity I calculated the square inches of blade on my 70s era five blade flex fan, app 87.5 sq. in. (My orig. steel seven blade fan is hiding from me.) The eight bladed plastic fan on the 260 is 120 sq. in. I think the slipping clutch requires more surface area (mass) of fan blade to pull the same amount of air as a non clutched fan and might negate Cliff's theory of the pizza pan flex-fan. Sorry Cliff. 

 

[Pop's Z]

Re: flex fans...I had one on a Datsun 2000 roadster. They are incredibly noisy! I would never have one on a car I owned again. At the time I was just being cheap and didn't want to pony up for a new fan clutch. Also, it didn't cool that well.

 

Cheers, Mike

[Mark Maras]

 Odd, I don't recall any more noise from my flex-fan than the orig. clutch fan. Different styles or manufacturers possibly?

[psdenno]

5 hours ago, Pop's Z said:

Re: flex fans...I had one on a Datsun 2000 roadster. They are incredibly noisy! I would never have one on a car I owned again. At the time I was just being cheap and didn't want to pony up for a new fan clutch. Also, it didn't cool that well.

 

Cheers, Mike

The five blade flex fan I had on my 240Z for many years made significantly more noise than the stock fan and clutch set up.  Coincidently, I went with the flex fan when my stock fan/clutch launched through the radiator because it was a less costly alternative.  I was in my cheap fix phase at the time.  I currently have a plastic fan and clutch back on and prefer it.

Dennis

[TomoHawk]

With all the carbon fiber parts being made, it's a wonder why a splash pan hasn't been offered for the Zed.

Back to coolant additives...

[Chickenman]

Curious as to why are you only using water in your Rad. Unless it's a track requirement... as for most Drag Strips? A proper coolant has anti corrosion additives s that are extremely beneficial when running aluminium and Iron together. I'm sure you know that.

The Water Wetter reduces the molecular tension of Coolant ( Antifreeze in Canada ) mixes. This allows more wetting of interior surfaces than just Coolant without Water wetter.  Coolant mix  also raises boiling temperature, which is good for reducing nucleate boiling, which in turn reduces the formation of steam pockets. While the heat absorption capability of Coolant mix is slightly less than that of distilled water, the addition of Water Wetter does bring the W/Wetter plus  Coolant mix much closer to the heat absorption capability of distilled Water.

Personally, I prefer the additional anti corrosive capabilities and increased boiling point of a Coolant mix with Water Wetter.  The anti corrosion additives of Coolant mixes are a big bonus to me.

BTW, VW/Audi ( and Porsche, BMW, Mercedes) use a low sulfate coolant referred to as G12.  The stuff is not cheap, but independent tests show it is vastly superior in preventing galvanic corrosion compared to Regular Green fluid or even DexCool ( yuck ). Pentosin makes an excellent product, much cheaper than you can get at VW/Audi dealers. As with any Coolant change, you should flush the whole system, although G12 can be mixed with other fluids, it decreases it's performance. But at least it will not turn into Red sludge like mixing Dexcool and regular " Green " Glycol antifreeze/coolant.

I'll see if I can find the link to the test data. It's quite interesting...

 

 

 

 

[TomoHawk]

Yes, it (non-slippery coolant) was a requirement by some of the places I visit in my summer travel this year.