How To: Mesh Fender Liner inserts (engine bay)
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Joined: Mar 2001
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From: FL-->NJ/NYC again!
How To: Mesh Fender Liner inserts (engine bay)
The idea behind this 'mod' is to relieve a high pressure area (the engine bay) by allowing air to exit. I have to give credit where it's due:
[taken from this thread: https://www.rx7club.com/3rd-generation-specific-1993-2002-16/want-cooler-engine-bay-without-changing-hood-530715/ ]
[taken from this thread: https://www.rx7club.com/3rd-generation-specific-1993-2002-16/want-cooler-engine-bay-without-changing-hood-530715/ ]
A much better solution is to cut out the plastic fender liner openings that are visible from the inside of the engine compartment. Way back in 1995 when I did a lot of testing on my first FD, I had found that cutting both of those wheel well areas out and replacing the plastic with an open wire screen, actually reduced my 60 - 160 MPH acceleration times a full 1.5 seconds. That is a HUGE gain in anyones book. It was tested 4 times and results were consistent.
Thus, my conlusion is that removing those liners drop pressure build up inside of your engine compartment which, also should allows for a much better exchange of air as it is allowed to flow thorugh instead of being trapped underhood.
BTW - I just did that very mod on my 2nd FD a few weeks ago.
Thus, my conlusion is that removing those liners drop pressure build up inside of your engine compartment which, also should allows for a much better exchange of air as it is allowed to flow thorugh instead of being trapped underhood.
BTW - I just did that very mod on my 2nd FD a few weeks ago.
I truly have not noticed much additional dirt accumulation. After all, the air is supposed to be moving out of the compartment instead of IN. I assume that in rainy conditions you would get more wet inside than normally but, I do not drive this car much in the rains. The first FD, however, was a daily driver and I even raced it in the rain with no problems.
It helps to either relocate your battery for a clean air flow path from the radiator or, have on sit on its side (Odessay), like mine. On the pass. side the M2 box tends to be blocking air exit to a point but, altogether, I still think the opening there is beneficial as underhood pressures will find the way around a blocking element to exit.
Edit; To answer your question I never did underhood temperature tests in this car. My goals were primarily driven by high speed performance gains and cooling was never a problem for me.
Also, diffusers are designed not so much to block air from getting under the bumper but, to provide a low pressure area under the back of the car. When you gradually expend a restricted high pressure air flow (as diffusers do) the air pressure will drop to the point where instead of positive pressure it can create negative pressure or vacum.
Formula and other racing cars that use that simple technology by creating diffused air tunnels under their sidepods can develp huge downforces. As an example, when I raced Formula Mazda with front and back wings but no diffusers, my downforce was adjustable probably between 200-400 lbs at high speeds. On the other hand, a Formula Atlantic car with much smaller wings BUT, underpod diffusers had developed 2400 lbs of downforce at 140 MPH. Plenty enough for that car to be driven on a ceiling, upside down and be sucked to that ceiling.
That is why it was impossible for my FM to keep up with a well driven FA in corners.
It helps to either relocate your battery for a clean air flow path from the radiator or, have on sit on its side (Odessay), like mine. On the pass. side the M2 box tends to be blocking air exit to a point but, altogether, I still think the opening there is beneficial as underhood pressures will find the way around a blocking element to exit.
Edit; To answer your question I never did underhood temperature tests in this car. My goals were primarily driven by high speed performance gains and cooling was never a problem for me.
Also, diffusers are designed not so much to block air from getting under the bumper but, to provide a low pressure area under the back of the car. When you gradually expend a restricted high pressure air flow (as diffusers do) the air pressure will drop to the point where instead of positive pressure it can create negative pressure or vacum.
Formula and other racing cars that use that simple technology by creating diffused air tunnels under their sidepods can develp huge downforces. As an example, when I raced Formula Mazda with front and back wings but no diffusers, my downforce was adjustable probably between 200-400 lbs at high speeds. On the other hand, a Formula Atlantic car with much smaller wings BUT, underpod diffusers had developed 2400 lbs of downforce at 140 MPH. Plenty enough for that car to be driven on a ceiling, upside down and be sucked to that ceiling.
That is why it was impossible for my FM to keep up with a well driven FA in corners.
To place it in perspective my 1.5 second gain was off of a time of approximately 25 seconds, (60-160) without pulling out my old records. If I remember correctly that was one of the last mods I did before the crash.
BTW- not that extreme gain when compared to an other test that I ran with both headlights up and down. The air resistance introduced by the raised headlights increased the same 60-160 acceleration times by over 1 second. So, we're taking about roughly the same amount of reduction in drag in both cases.
BTW- not that extreme gain when compared to an other test that I ran with both headlights up and down. The air resistance introduced by the raised headlights increased the same 60-160 acceleration times by over 1 second. So, we're taking about roughly the same amount of reduction in drag in both cases.
Thread Starter
Joined: Mar 2001
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From: FL-->NJ/NYC again!
The pics are pretty self-explanatory..... make sure you get the aluminum mesh, and you can see the template I traced in one of the pics. The rivets are 1/8th diameter 1/8th grip aluminum short rivets that I picked up from a local hardware store. They can be had from www.arrowfastener.com, part #RSA1/8IP.
Edit: btw, free set of apex seals if you can make out what kinda pen that is and tell me all eight indications and dosing regimes for the drug
Edit: btw, free set of apex seals if you can make out what kinda pen that is and tell me all eight indications and dosing regimes for the drug
Last edited by GoodfellaFD3S; Feb 24, 2010 at 07:13 PM.
Thread Starter
Joined: Mar 2001
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From: FL-->NJ/NYC again!
More..... btw my dad did this on his R1 about three years ago and his engine bay doesnt seem to have gotten any dirtier.
Last edited by GoodfellaFD3S; Feb 24, 2010 at 07:09 PM.
How does pressure build up in the engine bay? The whole bottom of it is open. Also, how would pressure buildup in the engine bay significantly reduce acceleration of the car? I'm willing to believe that his acceleration tests were accurate but I am not sure I buy the mechanism.
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How does pressure build up in the engine bay? The whole bottom of it is open. Also, how would pressure buildup in the engine bay significantly reduce acceleration of the car? I'm willing to believe that his acceleration tests were accurate but I am not sure I buy the mechanism.
, air enters from the front of the bumper at an angle parallel to the ground and eventually travels/gets pushed to the firewall/back of the engine bay of the car. At this point, yes some air would be forced to exit via the side vents and opening under the engine, but there will also be some circling around the engine bay thus causing an area of pressure (since the hood is closed and there's an under stray under the engine, encapsulating some of the incoming air). Cutting outlets into the fender liners would create more of a direct path for the air that enters the car to exit the engine bay rather than hit the firewall and circulate/cause areas of pressure and turbulence.
Man, I think I understand how this could work, but it's REALLY hard to cut up new (and NOT CHEAP) fender liners! 
I replaced my passenger one as it was messed up by a previous owner, and took me a few years just to finally say "yep, go ahead and fork out the cash".
+1 on wanting to see an installed pic. Kind of hard to visualize how it would look.
Wonder if it would be any help opening up the bottom of the fender liners for airflow through the oil coolers?
BTW, some Japanese company recently started making a smaller/different design coolant overflow tank. Looks like it's designed to get out of the way for better airflow.
Dale
I replaced my passenger one as it was messed up by a previous owner, and took me a few years just to finally say "yep, go ahead and fork out the cash".+1 on wanting to see an installed pic. Kind of hard to visualize how it would look.
Wonder if it would be any help opening up the bottom of the fender liners for airflow through the oil coolers?
BTW, some Japanese company recently started making a smaller/different design coolant overflow tank. Looks like it's designed to get out of the way for better airflow.
Dale
Joined: Jul 2001
Posts: 10,672
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From: Charlottesville VA 22901
Call me crazy but somehow I don't think cutting holes in my fender liners will cut my lap time by 1.5 seconds or more
But I'll sure give it try lol.
In most any decently modded FD I'll leave oaktree at vir at around 50mph and finish at around 155 if the engine etc... is happy so the fender liner mod should shave atleast a second.
I come out of turn 17 (hog pen) at 110 mph and finish at 150 mph so I should get another 1/2 second here.
If this works I'll surely post the results
But I'll sure give it try lol.
In most any decently modded FD I'll leave oaktree at vir at around 50mph and finish at around 155 if the engine etc... is happy so the fender liner mod should shave atleast a second.
I come out of turn 17 (hog pen) at 110 mph and finish at 150 mph so I should get another 1/2 second here.
If this works I'll surely post the results
Call me crazy but somehow I don't think cutting holes in my fender liners will cut my lap time by 1.5 seconds or more
But I'll sure give it try lol.
In most any decently modded FD I'll leave oaktree at vir at around 50mph and finish at around 155 if the engine etc... is happy so the fender liner mod should shave atleast a second.
I come out of turn 17 (hog pen) at 110 mph and finish at 150 mph so I should get another 1/2 second here.
If this works I'll surely post the results
But I'll sure give it try lol.
In most any decently modded FD I'll leave oaktree at vir at around 50mph and finish at around 155 if the engine etc... is happy so the fender liner mod should shave atleast a second.
I come out of turn 17 (hog pen) at 110 mph and finish at 150 mph so I should get another 1/2 second here.
If this works I'll surely post the results
I look forward to hearing your results.
Rich, did you also do the CrispyRX7 mod to the fender liners for hoped-for increased air flow through the oil cooler?
Thread Starter
Joined: Mar 2001
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From: FL-->NJ/NYC again!
Alberto, my buddy Nick performed the oil cooler fender liner mod thingamajig back in like 2003 so no offense to Crispy but he can't lay the claim of his name to the fame
you could spray the mesh with some black paint and make it blend better in the bay. my .02$
looking good though!
Homer: Hey, what are all these holes? (points at bullet holes in car hood)
Car Salesmen: These are speed holes. They make the car go faster.
Homer: (impressed) Oh yeah, speed holes.
looking good though!
Homer: Hey, what are all these holes? (points at bullet holes in car hood)
Car Salesmen: These are speed holes. They make the car go faster.
Homer: (impressed) Oh yeah, speed holes.
Thread Starter
Joined: Mar 2001
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From: FL-->NJ/NYC again!
As mentioned, my pops used the same stuff years back and it blends in very well in the bay. No need for paint. Remember, I took those pictures with a flash.
Intuitively I think these spots will help to speed the air out of the bay faster/more efficiently than a vented hood. That not being the case is fine, b/c I like the OEM hood for many reasons and for my car have never seen the need to run a vented hood
Intuitively I think these spots will help to speed the air out of the bay faster/more efficiently than a vented hood. That not being the case is fine, b/c I like the OEM hood for many reasons and for my car have never seen the need to run a vented hood
Racecar - Formula 2000
Joined: Sep 2002
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From: Bath, OH
The idea behind this 'mod' is to relieve a high pressure area (the engine bay) by allowing air to exit. I have to give credit where it's due:
[taken from this thread: https://www.rx7club.com/showthread.php?t=530715 ]
[taken from this thread: https://www.rx7club.com/showthread.php?t=530715 ]
Quickie question:
Since you are venting air from the front of the engine compartment, wouldn't that possibly cause stagnation and more heat at the rear of the engine compartment (turbo area)?
Joined: Jul 2001
Posts: 10,672
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From: Charlottesville VA 22901
FWIW I've seen FDs and other cars w/o any fender liners at the track
You can also just ditch the rear hood weather strip and put a few washers under the hood hinges to increase airflow through the engine bay.
Seriously though I don't think this mod will work in the real world to this sort of extreme. At this I don't even use an undertray so I should have plenty of places for air to go once it moves through the front air duct.
I've seen plenty of people recording significant air and water temperature drops with a vented hood, but never a MPH or ET improvement.
Sorry to be such a naysayer, but I like to keep everything open to discussion.
Sorry to be such a naysayer, but I like to keep everything open to discussion.