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Old 09-12-2011, 04:47 PM   #1
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Default '01+ bumper "mouth" cool radiator better than 99/00?

I may have the opportunity to swap an 01 front bumper cover with my '00.

Does the 01 bumper mouth provide better airflow for the i/c and radiator?
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Old 09-12-2011, 05:52 PM   #2
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The orifice makes little difference from what I understand about aero, you're better off ducting the front of the radiator.
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Old 09-12-2011, 06:35 PM   #3
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Not enough difference to notice any improvements I would imagine. But I think it looks cooler for sure.
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Old 09-12-2011, 07:34 PM   #4
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The 99/00 and 01+ still use the same air diverter behind the bumper, so my guess is its mainly cosmetic. I have an 01+ bumper sitting in the garage waiting for me to arrange for paint, but my motivation is a MSM headlight upgrade rather than cooling. Time and money spent on ducting will probably be more effective than a bumper swap, just my

If you need measurements or something, let me know.
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Old 09-12-2011, 08:05 PM   #5
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Increasing the orifice will not increase pressure on the front side, we've been over this.
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Old 09-12-2011, 08:06 PM   #6
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Ducting and hood air release increase flow
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Old 09-12-2011, 08:21 PM   #7
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The overall function will be about the same. As others pointed out the little airdam inside is the same one for both styles.

However there's a reason both my NB1's have this swap done: It looks LIGHTYEARS better.
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Old 09-12-2011, 08:30 PM   #8
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Quote:
Originally Posted by jacob300zx View Post
Ducting and hood air release increase flow
I tried to tell you ***** this before you hole-sawed JZ's bumper.
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Old 09-12-2011, 09:13 PM   #9
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Quote:
Originally Posted by 18psi View Post
however there's a reason both my nb1's have this swap done: It looks lightyears better.
+1,000
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Old 09-13-2011, 11:16 AM   #10
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Quote:
Originally Posted by hustler View Post
I tried to tell you ***** this before you hole-sawed JZ's bumper.
Potty mouth!

Then why/how this?
https://www.miataturbo.net/showthrea...1&highlight=4c
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Old 09-13-2011, 11:41 AM   #11
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Quote:
Originally Posted by BarbyCar View Post
**** **** *** ---- bitch

There could be many reasons: no ducting, bad ducting, leaky ducting, no belly pan, cooler air, driving less aggressively, less traffic, spark angle changes, fans turning, and unknown. It's pretty widely accepted that increasing frontal area or the heat exchanger opening on a Miata will not increase the pressure differential.
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Old 09-13-2011, 03:46 PM   #12
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Quote:
Originally Posted by hustler View Post
**** **** *** ---- bitch

There could be many reasons: no ducting, bad ducting, leaky ducting, no belly pan, cooler air, driving less aggressively, less traffic, spark angle changes, fans turning, and unknown. It's pretty widely accepted that increasing frontal area or the heat exchanger opening on a Miata will not increase the pressure differential.
We are in violent agreement. Just posing a thought that maybe there is an optimal hole size that is a little bigger than factory for some applications of a Miata (street vs. autox vs. track vs. drift etc). And yes I'm familiar with edge effect, gas laws, laminar flow, density effects and thermodynamic properties of air.

The slight temp reduction I saw was on back to back lapping sessions the same day (within 40 minutes) with the holes open and then taped over. Other measurable parameters unchanged. I wouldn't say this was a scientific test but I wouldn't ignore its numbers either. I also wouldn't make this mod based on 4C improvement either.
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Old 09-13-2011, 04:18 PM   #13
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Race cars do it like this (note the nice curving contours):


That increases the efficiency of what you have without the addition of more frontal resistance. You see this in just about every race car out there.
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Old 09-13-2011, 06:40 PM   #14
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I suspect holes-in-the-bumper works if you don't have the above ducting.

Think about it - when air flows in a ducting-less setup, in the mouth, the air in the upper part of the radiator, behind the bumper metal, and behind where the holes in the above pic are, is gonna be pretty dead. The above ducting solves that issue.

The TDR ducting / paneling that comes with the ic approximates this.
Plus their tube/fin i/c has far better flow:
See results:
https://www.miataturbo.net/showthrea...&highlight=tdr

As for ducting vs. holes, if the rear of the radiator is flow challenged (e.g. no hood vents), I think theoretically the ducting is better. With hood venting, I don't know.
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Old 09-15-2011, 12:57 AM   #15
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Quote:
Originally Posted by BarbyCar View Post
Quote:
Originally Posted by hustler View Post
**** **** *** ---- bitch

There could be many reasons: no ducting, bad ducting, leaky ducting, no belly pan, cooler air, driving less aggressively, less traffic, spark angle changes, fans turning, and unknown. It's pretty widely accepted that increasing frontal area or the heat exchanger opening on a Miata will not increase the pressure differential.
Like hustler said, there are a million different variables that could have affected why there was a 4oC difference. 4% is hardly significant considering all the possible variables. 10% perhaps.

Here's some info on airflow through radiators.

Quote:
Originally Posted by Race Car Vehicle Dynamics Section 15.9- Applied Aerodynamics
Three parameters are defined which "closely relate" to the cooling performance of a radiator, namely,

1. Matrix (core) pressure drop coefficient, Kp=(delta)P/.5(rho)Vf^2
where (delta)P is the static pressure drop front-to-rear across the radiator and Vf is the velocity of air across the radiator.

Thus, 0.5(rho)Vf^2 is the dynamic pressure (kinetic energy) at the face.

2. Velocity ratio
Rv=Vf/V0
where Vf is defined above, and V0 is the free stream velocity

3. Drag coefficient of the radiator,
Cd=Drag of radiator/(0.5(rho)V0^2*A)
where A is the radiator face area.

In general, a large Kp (pressure drop across the radiator) and a large Rv (velocity ratio) produce the best cooling performance.

What does that mean in real world terms? To get the best, consistent performance out of a radiator, force as much air THROUGH the radiator (not around, THROUGH) at as high of a pressure as possible and allow it to leave as easily as possible. Opening up large holes in the bumper does not help with either increasing incoming velocity or pressure.
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