it has something to do w/ it keeping a higher pressure in the radiator, increasing cooling efficiency
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'95 200sx SE = konig divas on 185/60R-14 Kumho 716s, open-airbox, k&n filtercharger, 1.3 bar radiator cap, all red taillights, removed black doorframe vinyl, mesh grill, remote start alarm, no-chrome window frame, sylvania silverstars, optima red top, w/ 4AWG ground, full kenwood sound system. my car!
Well,
The fastest cheapest way to add like 150 HP to your car is to pay a truck driver around $20 to get him to rear end you at 60 MPH at the exact time you want to launch your car vs. your buddy. That should give you a crazy hole shot and easily will get you into the 10's.
I have the NISMO cap and it helped on hot days w/ the A/C on in stop and go traffic to keep the temps down.
The higher pressure had me nervous about leaks, but none so far!
__________________ 1991 Sentra SE - Auto to Manual swap, 15" Rota Subzero's, 205/50 Kuhmo 712's, Tsuru headlight conversion, SE-R front and rear disc brakes, SE-R front and rear swaybars, SE-R throttle body, SE-R rear inner taillights, HS CAI and Header, H&R springs, Koni shortened struts, ES Hyperflex kit, B&M Short Shifter, Autometer gauges.
The central issue that the higher pressure cap solves and wasn't explained is that coolant only works well when it's liquid. Liquids have two properties called specific heat and latent heat of vaporization. Specific heat is the amount of heat needed to raise the temperature of, in this case, a liquid one degree per unit mass. You'll typically see BTU per pound per ºF or kilojoule per kilogram per ºC .
An interesting property of liquids is that temperature rises as heat input rises until boiling point is reached. Then, temperature remains constant until all liquid is vaporized, regardless of heat input. More heat per unit time just increases boiling RATE, not liquid TEMPERATURE. The amount of heat needed to vaporize a unit mass of liquid is called latent heat of vaporization. Only after all liquid has been turned to vapor does temperature begin to rise again.
Boiling point is dependent upon pressure. As you raise pressure, boiling point increases. Pure water at atmospheric condition boils at 212 ºF/100 ºC. Raising the pressure of the cooling system forces boiling point up (as does the addition of anti-freeze, which we'll ignore for this discussion). The higher the pressure, the higher the boiling point.
Latent heat of vaporization of water is quite a bit greater than specific heat of liquid water or steam. When you heat coolant to boiling, you get steam, which has low specific heat. It won't absorb heat the way liquid coolant can. You then get hot spots that overheat gaskets and fasteners and causes long, torsionally soft things to bend, like the head.
Raising system pressure raises boiling point of the coolant. If your cooling system is marginal, upgrading to the 300ZX cap can make a significant difference in your car's longevity.
The SE-R suffers both a marginal radiator AND water pump cavitation. Cavitation is simply vaporization caused by mechanical means instead of thermal stress. Raising the system pressure makes these bubbles more difficult to form and keeps them smaller.
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Bruce in Houston
'94 Nissan Sentra SE-R w/ $tuff, converting to ITA
'98 Suzuki Bandit 1200S w/ $tuff
'02 Dodge Dakota SLT 4-dr tow beast, stock!
Last edited by bahearn : Jan 20th, 2003 at 03:51 PM.
Originally posted by Centurion I see a couple of ppl using a 13lb. radiator cap, how in the world does that improve performance?
13 Psi is stock. You meant 16 or 17 Psi.
Unless you are going for show and have the money, it is not worth it to spend $40 on the NISMO cap when you can get the 300ZX TT cap for much less. It is around $10 or so.
Only difference is that the NISMO cap has approx. 1 Psi more pressure than the 300ZX TT
Linear Mode
