I want to buy a NISMO radiator cap (1.3 bar pressure, I think stock cap is 0.9 bar). I want it for looks but I'm concerned that the higher pressure would be bad for the coolant system. Thoughts or experiences?

 

I wouldnt stress it......ebay right?

 

from what i've read... the higher pressure raises the boiling point of the coolant, making it more efficient since it needs a higher temperature to make the coolant get overheated.

 

Got mine from here:

Lee Auto

At $27, it was the cheapest I found. Also saved on shipping cause 2 of us ordered them.

 

Yes i know that higher pressure makes the cooling system more efficient, and thanks for the link Blues, but my question was can our radiator and coolant system take the extra pressure? It's not worth it to me if it's a risk.

 

if you want it for looks then get the nismo (1.3 bar) but if you want it for function then get one regular stant cap for a 95 300TT (1.2 bar). here is a rundown of the benefits.

 

Thanks for that article, I've seen it. I'm more looking for personal experiences on Maximas with the higher pressure caps, but I'm guessing that because no one is reporting any problems; there aren't any.

 

Wouldn't 0.9 bar be a vacuum? (negative pressure)

 

That's what I thought when I read 0.9 bar! Maybe it is a slight vacuum?

 

Radiator cap pressure spec is a "relative pressure spec" - ie - its by how much the pressure inside the radiator will have to exceed the surrounding air pressure before it starts releasing fluid into the atmosphere in order to limit the radiator pressure at that absolute max pressure.

 

I have the nismo one. So far only drove the car for about 200 miles with it on, so no long term feedback yet.

 

I always thought these things were all rice. Thanks for the thread and links Tom and others. This is an interesting idea. For those that want it to look good but don't care about the extra bit of pressure it is very easy to polish the stock Z cap to a nice bling level. I can't see this having any real use for street driving. I never see more than 190 unless I'm sitting in a parking lot. My most consistant temp is 187 in nearly all situations. How cool is it safe to run the coolant for short periods of time? Would it be safe to drop the coolant as low as possible for 1/4 mile runs? What temp would be achievable with either of these caps and the fans on a manual switch?

 

i got mine...for free! a order mixup. I've had it for about 3 months and i do alot of driving and no negative results from putting it on.

 

i have had mine for about 8000 miles. i don't know how much of a diffrence it makes but i would advice getting it its only $30

 

It's gauge pressure (pressure above atmospheric). If it said 0.9 bar ABSOLUTE, then it would be a slight vacuum.

Also, I personally don't think there is any "performance" gain to using one of these -- they only give you a little more breathing room before your car overheats. If the coolant is at a temperature where your stock cap can't handle the pressure, then you are operating well above the T-stat temp and the engine is running hot. For N/A, there would be no gains. For a forced induction setup, since there is more fuel and air (which is hotter because it is compressed) combusting in the engine, then the higher pressure cap might mean the difference between being able to drive the car and being stranded on the side of the road, watching steam and coolant billow from your hood.

A caveat: IF, and this is a big IF, the water pump can get the system to the higher pressure, even at lower temperatures, then you might receive a small benefit because the heat transfer rate is increased. But, since the system was designed with the stock cap in mind, I doubt this is the case.

 

Thats a great point Mizeree. I hadn't thought of that. I still have the question though. What is the lowest temp that would be safe for 1/4 mile runs? Will the temp ever go below 180 with the fans on manual? If so is it safe?

 

Lowest temp is most likely the correct operating temp of the engine as designed for - not lower or higher - efficiency of the motor is tied pretty tight to that.

Under 180? - Not with a properly working and present thermostat no.

Safe? - if your cooling system cannot ensure the motors remains at a temp that prevents the cooling water from boiling, then its not safe. Dont think anybody can say what is going to be safe - it depends on the state of your motor, your cooling system, air temp, tuning, mixture, timing etc. Dont know if you meant it this way, but its the expanding water that causes the cooling system to run at a specific pressure and not the waterpump - the waterpump is only there to circulate the water and can contribute effectively nothing to the system pressure because of its operation in a sealed-off environment - ie - the inlet and outlet pressures are effectively the same

 

Nismo makes a 160 degree T-stat. Its $60 though.


Yes, that is what I figured, but I was not 100% sure so I thought I'd add it as a caveat. Thanks for confirming my belief though.

 

i have had my nismo cap for over a year and i drive all over from vegas to phoeniz in the summer and i never have any problems