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This is a cosmetic mod, and nothing more. If you believe Porsche left 8hp on the table through the design of the airbox cover, and if you believe that Fabspeed discovered this but Rothsport, 9M, etc, have not discovered it, please PM me to get in on a real estate deal I'm working
This was the content I was hoping for when I got online.
Are there performance benefits to more air flow? Yes.
It depends on a significant number of factors, but in the case of a stock 993, the answer is no.
I'm not going to write a long explanation of how intakes work, where restrictions are, what volumetric efficiency and cylinder filling are, how cam design, head design, port and runner sizes, and so on, affect airflow and horsepower. There are good youtube videos that cover this stuff if you're not a person who builds engines. If you think you're going to get more HP on a 993 by cutting some plastic out of your airbox cover,* all I can say is, Go with God my son.
*You may note that Porsche did not list a HP difference between 993's with and without the motorsound option. Motorsound cars had a bunch of holes drilled in the airbox cover. Maybe this was a 1990's era Porsche conspiracy to hide the gains from modifying airbox covers?
I'm not going to write a long explanation of how intakes work, where restrictions are, what volumetric efficiency and cylinder filling are, how cam design, head design, port and runner sizes, and so on, affect airflow and horsepower. There are good youtube videos that cover this stuff if you're not a person who builds engines. If you think you're going to get more HP on a 993 by cutting some plastic out of your airbox cover,* all I can say is, Go with God my son.
I don't need any assistance with this topic, at all.
Originally Posted by Churchill
*You may note that Porsche did not list a HP difference between 993's with and without the motorsound option. Motorsound cars had a bunch of holes drilled in the airbox cover. Maybe this was a 1990's era Porsche conspiracy to hide the gains from modifying airbox covers?
Respectfully, the "motor sound" cover has a small number 1/8" holes in it. The equivalent of perhaps a single 2" hole.
Respectfully, the "motor sound" cover has a small number 1/8" holes in it. The equivalent of perhaps a single 2" hole.
It's got about 200 1/8" holes in it, much more than a 2" diameter circular cutout. But for argument's sake, let's say it's just a single 2". A 2" hole added to a 993 airbox cover increases "airflow" by about 25%. You're saying that a 25% increase in "airflow" doesn't make any power -- how could that be possible? I thought the airbox cover starves the engine for airflow? If that was actually the case, surely a massive 25% increase in airflow would create more power.
Of course, the 993 airbox is not restrictive. In many cases, such as on early 911's, the stock airbox actually adds power, by channeling the intake charge and helping it accelerate. Remember: an engine is an air pump, and therefore can only pump X amount of air at Y RPM. For a properly designed engine, you could run it with no airbox cover and no filter and it would make no difference in power, and might in fact lose power.
Now, a modified engine can definitely benefit from intake mods, because in this case you've built an air pump that pumps more air than stock.
Here's some 993 dyno evidence from a post several years ago, BTW:
Originally Posted by DJF1
You know its also interesting when I did the dyno run on my 95 on the same shop, comparing filters etc, I did not have any HP gains Frankly Sam told me then that the open box should not make any difference so we tried the motorsound airbox with the K&N and if nothing else we lost HP up high with a bit better torque lower.
My sincerest apologies for incorrect images, While that 'exact' Air-box filter is for the 911, we do offer a very similar filter for the 993 (Images below). If you are interested in swapping yours out, I'd love to extend a Rennlist member discount to you all.
My sincerest apologies for incorrect images, While that 'exact' Air-box filter is for the 911, we do offer a very similar filter for the 993 (Images below). If you are interested in swapping yours out, I'd love to extend a Rennlist member discount to you all.
According to their web page it will add 8whp. My car have made 640ish hp with stock airbox (C4S). Will do a remap in a month or so due to a new turbo setup and have always wondered if there was any hp restriction in the oem airbox, so I will remove the lid and see if that increases hp, and then remove air filter and lid to see if there is any hp to gain.
According to their web page it will add 8whp. My car have made 640ish hp with stock airbox (C4S). Will do a remap in a month or so due to a new turbo setup and have always wondered if there was any hp restriction in the oem airbox, so I will remove the lid and see if that increases hp, and then remove air filter and lid to see if there is any hp to gain.
05-29-2020, 08:50 PM
Frankly Sam told me then that the open box should not make any difference so we tried the motorsound airbox with the K&N and if nothing else we lost HP up high with a bit better torque lower.
