Went back to stock airbox cover, lost HP.
#47
Instructor
How about a pricey one, Bose noise cancelling headsets; while you're at it, might as well buy one for you passenger; this way you can really have a very nice conversation while driving.
"Just drive the darn thing"
"Just drive the darn thing"
#48
Originally Posted by TomF
To throw another wrench in the works.... maybe the dyno results above are symptomatic of the combination of the B&B mufflers and the motorsound airbox. Remember, Porsche is famous for engineering the complete package, where each component complements each other. Just my .02...
While a highly restrictive muffler could make it impossible to realize a gain, I'm not aware of a scenario where an adequate flowing muffler can "interact" with intake changes.
Porsche probably did a good job of optimizing the intake. They are unlikely to have left free horsepower lying on the table. Any additional flow - assuming there was ever a restriction - is likely offset by lower velocity and hotter air. I flatly do not believe a car has been made noticeably slower by going back to a stock intake. Show me the time slips.
Whew, that was thirsty work.
#49
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Originally Posted by ignomini
The power change is going the wrong way. It looks to me as though air velocity in the intake tract has been dissrupted by poking the holes. There have also been scenarios demonstrated where a surface across from the air intake interacts with airflow in a positive way. Poking the holes may have eliminated this effect.
While a highly restrictive muffler could make it impossible to realize a gain, I'm not aware of a scenario where an adequate flowing muffler can "interact" with intake changes.
Porsche probably did a good job of optimizing the intake. They are unlikely to have left free horsepower lying on the table. Any additional flow - assuming there was ever a restriction - is likely offset by lower velocity and hotter air. I flatly do not believe a car has been made noticeably slower by going back to a stock intake. Show me the time slips.
Whew, that was thirsty work.
While a highly restrictive muffler could make it impossible to realize a gain, I'm not aware of a scenario where an adequate flowing muffler can "interact" with intake changes.
Porsche probably did a good job of optimizing the intake. They are unlikely to have left free horsepower lying on the table. Any additional flow - assuming there was ever a restriction - is likely offset by lower velocity and hotter air. I flatly do not believe a car has been made noticeably slower by going back to a stock intake. Show me the time slips.
Whew, that was thirsty work.
#50
Originally Posted by Bull
I see. So, why did they put the open boxes on the Cup Cars, etc., with more free flowing exhausts and engines tuned to move more volume through?
What we've often seen in the supercharger business is stock intake and exhaust systems flow well enough that changing them has no real effect. However, supply pressurized air, or make other changes to increase air flow capacity of the engine, and then there are additional increases to be had by changing intake/exhaust pieces.
There are exceptions. For whatever reason, Honda (Acura) strangled the RSX Type S. We saw 15-18 more front wheel horsepower simply by changing the intake and adding a header. That was an eye opener.
#51
Robin Sun (Robin 993DX) did a dyno comparison a while back. I can't find the threat, but result was that using a drilled airbox cover (with large holes) produced less HP due to higher air intake temps from the engine compartment. A drilled airbox cover with smaller holes did not loose HP because it did not suck up as much hot air.
#52
Originally Posted by Blue Ocean
Robin Sun (Robin 993DX) did a dyno comparison a while back. I can't find the threat, but result was that using a drilled airbox cover (with large holes) produced less HP due to higher air intake temps from the engine compartment. A drilled airbox cover with smaller holes did not loose HP because it did not suck up as much hot air.
with the standard wing raised at speed, the air the compartment is cooled considerably.
#53
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Originally Posted by Blue Ocean
Robin Sun (Robin 993DX) did a dyno comparison a while back. I can't find the threat, but result was that using a drilled airbox cover (with large holes) produced less HP due to higher air intake temps from the engine compartment. A drilled airbox cover with smaller holes did not loose HP because it did not suck up as much hot air.
Edward
#54
RL Technical Advisor
Jeff:
Running the risk of repeating myself, I'd caution anyone against drawing any conclusions about airboxes based on chassis dyno test results since one cannot replicate airflow when the car is strapped to the dyno,.....
"Ventilated" airboxes do work when the car is moving or when the engine is run on an engine dyno where suffficient airflow is present. Porsche figured this out as well with the 964 Cup cars.
Running the risk of repeating myself, I'd caution anyone against drawing any conclusions about airboxes based on chassis dyno test results since one cannot replicate airflow when the car is strapped to the dyno,.....
"Ventilated" airboxes do work when the car is moving or when the engine is run on an engine dyno where suffficient airflow is present. Porsche figured this out as well with the 964 Cup cars.
#55
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Originally Posted by Thaddeus
I found a compromise. The stock air box cover has a 'snorkle' thing that runs inside the cover, that blocks part of the filter after the air flows into the chamber. I found this snorkle assembly unsnaps from the cover, leaving a larger opening for air to enter, and removing the obstruction to the filter. I think I have about 30% more opening for the air to enter, and the entire filter can now do its work. The engine is still quieter than when using the Fabspeed cover. Cheap mod, indeed: no cost whatsoever, and no permanent modification. I can put it back in under a minute. Perfect!
#56
Seems to me the best mod here (at least for C4's) is a series of holes in the airbox with a rotating wheel that will alternate bursts of air to the airbox and rear spoiler. That way the airbox will receive "supercharged" bursts of air and the spoiler will flap up and down allowing the cars to keep up with C2's. In the spirit of this thread.
I drilled the box on my 964, hated the noise, felt no difference and went back to stock.
I drilled the box on my 964, hated the noise, felt no difference and went back to stock.
#57
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Originally Posted by ignomini
I agree with you there. Better flowing cylinder heads, more aggressive cams, and higher rpm equals higher air volume needs. Changing the intake and exhaust makes sense in that scenario.
What we've often seen in the supercharger business is stock intake and exhaust systems flow well enough that changing them has no real effect. However, supply pressurized air, or make other changes to increase air flow capacity of the engine, and then there are additional increases to be had by changing intake/exhaust pieces.
There are exceptions. For whatever reason, Honda (Acura) strangled the RSX Type S. We saw 15-18 more front wheel horsepower simply by changing the intake and adding a header. That was an eye opener.
What we've often seen in the supercharger business is stock intake and exhaust systems flow well enough that changing them has no real effect. However, supply pressurized air, or make other changes to increase air flow capacity of the engine, and then there are additional increases to be had by changing intake/exhaust pieces.
There are exceptions. For whatever reason, Honda (Acura) strangled the RSX Type S. We saw 15-18 more front wheel horsepower simply by changing the intake and adding a header. That was an eye opener.
#59
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Originally Posted by slider
I tried to unsnap that snorkle an I had a hell of a time...in the end, I just left it on, but if you can pass along any tips for removal, I'd be grateful...it seems very straight-forward, but then again, I'm in the 1/3 prickly crowd...
#60
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Originally Posted by Mc-993
As a newbie, I am getting used to the way these boards work... It seems like about 2/3 of you are very supportive and helpful and the other 1/3 seem to fit into the "*****" category.
Thanks to the 2/3.
Thanks to the 2/3.