Cold air induction for oem box!
11-15-2004, 09:07 AM
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Cold air induction for oem box!
Hey guys!
I just did a cold air intake on my oem air box today and it does work in my opinion. What I did was; I took off the front bumper, took off the black plastic tray that sits infront of the induction tube. Then, removed the foam located just underneath the black tray and I fit a fleible plastic tube onto the short intake (not the long one). The next step I did was I drilled through the fornt bumper grill. As you may realized the front grill is actually just have open. On the right side just right beside the number plate, you could drill through the grill and that is excatly where the other end of the cold air intake would be!
Anyway thats what I have done and the intake temp drops quite a bit. I also realize the aceleration smoothern from as low as 3000rpm!
It took me about 2 and a half hours to do and I think it is worth the time. Who ever interested in DIY, this is what I would suggest.
Boyboydan.
I just did a cold air intake on my oem air box today and it does work in my opinion. What I did was; I took off the front bumper, took off the black plastic tray that sits infront of the induction tube. Then, removed the foam located just underneath the black tray and I fit a fleible plastic tube onto the short intake (not the long one). The next step I did was I drilled through the fornt bumper grill. As you may realized the front grill is actually just have open. On the right side just right beside the number plate, you could drill through the grill and that is excatly where the other end of the cold air intake would be!
Anyway thats what I have done and the intake temp drops quite a bit. I also realize the aceleration smoothern from as low as 3000rpm!
It took me about 2 and a half hours to do and I think it is worth the time. Who ever interested in DIY, this is what I would suggest.
Boyboydan.
11-15-2004, 06:35 PM
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Originally Posted by boyboydan
I fit a fleible plastic tube onto the short intake (not the long one).
If so, that only opens up and allows air at a certain 7250rpms, so the improvement will only be in the high rev range.
Originally Posted by boyboydan
Anyway thats what I have done and the intake temp drops quite a bit.
Originally Posted by boyboydan
I also realize the aceleration smoothern from as low as 3000rpm!
11-15-2004, 06:47 PM
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VFAD short intake only works at 7250 rpms my friend. Why don't you do that to the longer tube instead? There's this Helmholtz theory that RotaryGod was talking about. A longer tubing there might help a lot more for the low rpm range.
11-16-2004, 02:29 AM
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Pics please.
Also, I'd be interested to hear results if you disconnected the VFAD vacuum tube so that it was open all the time. The VFAD control solenoid is attached to the back left of the airbox (as you look at it from standing in front of the car). Pull off the black tube that disappears straight under the airbox to permanently open the VFAD flap.
Also, I'd be interested to hear results if you disconnected the VFAD vacuum tube so that it was open all the time. The VFAD control solenoid is attached to the back left of the airbox (as you look at it from standing in front of the car). Pull off the black tube that disappears straight under the airbox to permanently open the VFAD flap.
11-16-2004, 02:29 AM
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I noticed the other day that the intake air temp was about 6 degrees C higher than ambient.. going to try the "stop coolant going through the intake" trick to see what difference that makes.
11-16-2004, 02:31 AM
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Originally Posted by sco
I noticed the other day that the intake air temp was about 6 degrees C higher than ambient.. going to try the "stop coolant going through the intake" trick to see what difference that makes.
:p 
11-16-2004, 02:34 AM
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Sorry - should have said throttle body.... brain not in gear
https://www.rx8club.com/series-i-do-yourself-forum-73/diy-throttle-body-bypass-mod-36389/
https://www.rx8club.com/series-i-do-yourself-forum-73/diy-throttle-body-bypass-mod-36389/
11-16-2004, 02:45 AM
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Originally Posted by sco
Sorry - should have said throttle body.... brain not in gear
https://www.rx8club.com/showthread.php?t=36389
https://www.rx8club.com/showthread.php?t=36389
https://www.rx8club.com/showthread.p...&highlight=oem
11-16-2004, 03:42 AM
#15
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It makes sense though. Since the #2 tube opens at 3750 (or ~3250 rpM?? can't remember) hehe
It will add more cold air in all right.
But getting a aftermarket front spoiler will have the same effect.
Do you mind showing us pics??
It will add more cold air in all right.
But getting a aftermarket front spoiler will have the same effect.
Do you mind showing us pics??
11-16-2004, 04:04 AM
#17
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We are both wrong...
I wrote this on my website but I never remeber it :p
5500 rpm it is
http://www.step-hen.com/rx8spec.htm#SDAIS
I wrote this on my website but I never remeber it :p
5500 rpm it is
http://www.step-hen.com/rx8spec.htm#SDAIS
11-16-2004, 04:15 AM
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Sorry guys for the late reply as well as all the confushions.
It was the short tube that I did or, the number 2 on the picture. I will try post the picture next week. Please understand finding a place to do DIY in Hong Kong is not that easy... I have to find a place and time to strip the bumper off again in order to take the Picture.
How I measure the temp? Well....is wasn't very profashional. What I did was, I drove the car constantly on the highway at around 110KM/H before I did my cold air. Then I parked the car and opened up the bonnet and the air box was quite hot (still can touch but hot). After the mod, I drove the car with the same road and same speed and I park back the car and try touching the box again. This time you can feel the box is warm istead of hot. Thats why I think the cold air does help!
Thanks guys for suggesting doing the long one too! I think I will do it next week together with the picture.
Oh by the way, the short tube will open at 3500rpm instead of 7k+ .
Boyboydan.
It was the short tube that I did or, the number 2 on the picture. I will try post the picture next week. Please understand finding a place to do DIY in Hong Kong is not that easy... I have to find a place and time to strip the bumper off again in order to take the Picture.
How I measure the temp? Well....is wasn't very profashional. What I did was, I drove the car constantly on the highway at around 110KM/H before I did my cold air. Then I parked the car and opened up the bonnet and the air box was quite hot (still can touch but hot). After the mod, I drove the car with the same road and same speed and I park back the car and try touching the box again. This time you can feel the box is warm istead of hot. Thats why I think the cold air does help!
Thanks guys for suggesting doing the long one too! I think I will do it next week together with the picture.
Oh by the way, the short tube will open at 3500rpm instead of 7k+
.Boyboydan.
11-16-2004, 06:41 AM
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mmm.... interesting 
will.... you might as well "butt-dynoing" the potential kw increase with this mod :p
Originally Posted by boyboydan
...... try touching the box again. This time you can feel the box is warm istead of hot. Thats why I think the cold air does help!
11-16-2004, 06:45 AM
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I have read numerous posts which state the VFAD opening point is 7250rpm, although there is a possibility of it occurring earlier, such as at 5500rpm.
Here are a few posts on this subject:
https://www.rx8club.com/showpost.php...26&postcount=6
https://www.rx8club.com/showthread.p...highlight=vfad
https://www.rx8club.com/showthread.p...highlight=vfad
Just curious what would cause it to open at 5500rpm when it is generally understood to open up at 7250rpm?
Here are a few posts on this subject:
https://www.rx8club.com/showpost.php...26&postcount=6
https://www.rx8club.com/showthread.p...highlight=vfad
https://www.rx8club.com/showthread.p...highlight=vfad
Just curious what would cause it to open at 5500rpm when it is generally understood to open up at 7250rpm?
11-16-2004, 07:22 AM
#22
Originally Posted by nojooc
I have read numerous posts which state the VFAD opening point is 7250rpm, although there is a possibility of it occurring earlier, such as at 5500rpm.
Above 5500 rpm, the Variable Fresh Air Duct opens to add another intake air path. When open, the VFAD doubles the amount of air available to the engine and reduces restriction. The VFAD is controlled by a vacuum actuator. It is not open at all times because noise is also increased.
The VFAD system is only on the High Power engine. The Standard Power engine has a short inlet duct with a large diameter.
The VFAD system is only on the High Power engine. The Standard Power engine has a short inlet duct with a large diameter.
11-16-2004, 07:32 AM
#24
Originally Posted by nojooc
Thanks for clearing that up Jason, but what happens at 7250rpms if in fact the VFAD opens at 5500?
At engine speeds below 3250 rpm, air flows through the primary intake ports only. This keeps the intake air velocity high.
At the lower end of the primary intake tubes near the ports, high velocity air discharges from the Port Air Bleeds. This is the Jet Air Fuel Mixing system. The air discharge is caused by the pressure differential between the upper end of the primary air intake and the port air bleeds. This high velocity airflow blows fuel off port surfaces and increases turbulence. Atomization is improved and the mixture distribution is optimized. Atomized fuel is directed toward the ports and away from surfaces for the Anti-Wet Port effect. This Jet Air Fuel Mixing system is present in both Standard Power and High Power engines.
Above 3250 rpm, and when engine load is great enough, the Secondary Shutter Valve opens to permit airflow through secondary intake passages. The engine is now using two intake pipes and two intake ports per rotor. This reduces restriction and increases airflow and torque. The Secondary Shutter Valve is controlled by a vacuum control solenoid. Although the High Power engine is shown, the Secondary Shutter Valve works the same way in the Standard Power engine.
Above 5500 rpm, the Variable Fresh Air Duct opens to add another intake air path. When open, the VFAD doubles the amount of air available to the engine and reduces restriction. The VFAD is controlled by a vacuum actuator. It is not open at all times because noise is also increased.
The VFAD system is only on the High Power engine. The Standard Power engine has a short inlet duct with a large diameter.
Above 6250 rpm, the Auxiliary Port Valve opens the third or auxiliary intake port for additional airflow. All six ports are now used to increase horsepower and torque. The Auxiliary Port Valve is controlled by an electric motor through gears, a rack and linkage. The valve cycles each time the ignition is turned off to clear carbon. The Auxiliary Port Valve is used on the High Power engine only.
The High Power RENESIS Rotary Engine takes advantage of pressure waves in the incoming air to boost charging. This increases torque and power at higher engine speeds. At engine speeds above 7250 rpm, the Variable Dynamic Effect Intake Valve opens to shorten the effective length of the intake tubes. Intake pressure pulses reflecting back and forth in the intake manifold tubes force more intake charge through the ports and into the chamber. The VDI Valve is on both High Power and Standard Power engines, and is controlled by vacuum.
At the lower end of the primary intake tubes near the ports, high velocity air discharges from the Port Air Bleeds. This is the Jet Air Fuel Mixing system. The air discharge is caused by the pressure differential between the upper end of the primary air intake and the port air bleeds. This high velocity airflow blows fuel off port surfaces and increases turbulence. Atomization is improved and the mixture distribution is optimized. Atomized fuel is directed toward the ports and away from surfaces for the Anti-Wet Port effect. This Jet Air Fuel Mixing system is present in both Standard Power and High Power engines.
Above 3250 rpm, and when engine load is great enough, the Secondary Shutter Valve opens to permit airflow through secondary intake passages. The engine is now using two intake pipes and two intake ports per rotor. This reduces restriction and increases airflow and torque. The Secondary Shutter Valve is controlled by a vacuum control solenoid. Although the High Power engine is shown, the Secondary Shutter Valve works the same way in the Standard Power engine.
Above 5500 rpm, the Variable Fresh Air Duct opens to add another intake air path. When open, the VFAD doubles the amount of air available to the engine and reduces restriction. The VFAD is controlled by a vacuum actuator. It is not open at all times because noise is also increased.
The VFAD system is only on the High Power engine. The Standard Power engine has a short inlet duct with a large diameter.
Above 6250 rpm, the Auxiliary Port Valve opens the third or auxiliary intake port for additional airflow. All six ports are now used to increase horsepower and torque. The Auxiliary Port Valve is controlled by an electric motor through gears, a rack and linkage. The valve cycles each time the ignition is turned off to clear carbon. The Auxiliary Port Valve is used on the High Power engine only.
The High Power RENESIS Rotary Engine takes advantage of pressure waves in the incoming air to boost charging. This increases torque and power at higher engine speeds. At engine speeds above 7250 rpm, the Variable Dynamic Effect Intake Valve opens to shorten the effective length of the intake tubes. Intake pressure pulses reflecting back and forth in the intake manifold tubes force more intake charge through the ports and into the chamber. The VDI Valve is on both High Power and Standard Power engines, and is controlled by vacuum.