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fm540i

Retrofit X51 Power Kit Airbox into stock 997C4S

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I'm about to embark into uncharted waters. The X51 airbox is a direct replacement for the stock 3.8L airbox except the air inlet tube connecting the airbox to the inlet manifold is larger ie. a wider diameter. Anyone tried the retrofit, the X51 airbox looks great and at $800 is a lot cheaper than the Champian Motorsport carbon fiber box which runs $3 grand.

2007 C4S

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I'm about to embark into uncharted waters. The X51 airbox is a direct replacement for the stock 3.8L airbox except the air inlet tube connecting the airbox to the inlet manifold is larger ie. a wider diameter. Anyone tried the retrofit, the X51 airbox looks great and at $800 is a lot cheaper than the Champian Motorsport carbon fiber box which runs $3 grand.

2007 C4S

fm540i:

did you ever make this move? I'd be interested in hearing your results...

thanks,

-don

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I'm about to embark into uncharted waters. The X51 airbox is a direct replacement for the stock 3.8L airbox except the air inlet tube connecting the airbox to the inlet manifold is larger ie. a wider diameter. Anyone tried the retrofit, the X51 airbox looks great and at $800 is a lot cheaper than the Champian Motorsport carbon fiber box which runs $3 grand.

2007 C4S

I was under the impression that the X-51 air box had TWO air intakes ?

If so, it would not be a direct replacement for the stock 997 unit and would require a new engine hatch liner or cutting an additional hole into the existing one .

I would also check if the air intake connection to the engine is larger than the std. 997's

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Your correct, the retrofit instructions call for the modification of the deck lid. I've ordered the kit but still need to come up with a solution on the air inlet hose. The stock MAF sensor works but the stock inlet diameter is obviously smaller than the X-51 inlet. I'll keep everyone updated.

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Your correct, the retrofit instructions call for the modification of the deck lid. I've ordered the kit but still need to come up with a solution on the air inlet hose. The stock MAF sensor works but the stock inlet diameter is obviously smaller than the X-51 inlet. I'll keep everyone updated.

Any updates?

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I've finished the retofit and love the results. The X51 airbox is a direct drop in replacement for the stock airbox but there are a few work arounds required. First, you have to be comfortable cutting a hole in the lower metal portion of your decklid. Follow the template and be careful and it's not a problem. A good dremel tool is helpful. It will take some time to deburr the cut and fit the factory seal to the decklid properly but once done it looks stock. Just above the lower metal deck is a black plastic deck which is countored for the cutout. Once you make this cut the second air inlet breaths freely to the outside air. Beyond this the only issue is the inlet duct between the new airbox and the stock inlet manifold. I purchased a good quality silicone transition that acts as a spacer between the x-51 inlet hose and the stock manifold. Once trimmed and glued with a good high temp silicon it fits up perfect to the stock manifold/ Stock manifold has an OD of 3.25 inches. X-51 inlet hose has an ID of roughly 3.75 inches. Buy a silicone hose with roughly .25 inch walls and an ID of 3.25 inches and you have it made. It's a beautiful airbox and the engine breaths much better at higher RPM. Sound is a little louder and I find the engine is a little rougher until fully warmed up. (lot's more cold air coming in than stock)

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I've finished the retofit and love the results. The X51 airbox is a direct drop in replacement for the stock airbox but there are a few work arounds required. First, you have to be comfortable cutting a hole in the lower metal portion of your decklid. Follow the template and be careful and it's not a problem. A good dremel tool is helpful. It will take some time to deburr the cut and fit the factory seal to the decklid properly but once done it looks stock. Just above the lower metal deck is a black plastic deck which is countored for the cutout. Once you make this cut the second air inlet breaths freely to the outside air. Beyond this the only issue is the inlet duct between the new airbox and the stock inlet manifold. I purchased a good quality silicone transition that acts as a spacer between the x-51 inlet hose and the stock manifold. Once trimmed and glued with a good high temp silicon it fits up perfect to the stock manifold/ Stock manifold has an OD of 3.25 inches. X-51 inlet hose has an ID of roughly 3.75 inches. Buy a silicone hose with roughly .25 inch walls and an ID of 3.25 inches and you have it made. It's a beautiful airbox and the engine breaths much better at higher RPM. Sound is a little louder and I find the engine is a little rougher until fully warmed up. (lot's more cold air coming in than stock)

Whats the price for the airbox? Is the airbox compatible to the to a 997 C2 also?

Pictures please?

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I've finished the retofit and love the results. The X51 airbox is a direct drop in replacement for the stock airbox but there are a few work arounds required. First, you have to be comfortable cutting a hole in the lower metal portion of your decklid. Follow the template and be careful and it's not a problem. A good dremel tool is helpful. It will take some time to deburr the cut and fit the factory seal to the decklid properly but once done it looks stock. Just above the lower metal deck is a black plastic deck which is countored for the cutout. Once you make this cut the second air inlet breaths freely to the outside air. Beyond this the only issue is the inlet duct between the new airbox and the stock inlet manifold. I purchased a good quality silicone transition that acts as a spacer between the x-51 inlet hose and the stock manifold. Once trimmed and glued with a good high temp silicon it fits up perfect to the stock manifold/ Stock manifold has an OD of 3.25 inches. X-51 inlet hose has an ID of roughly 3.75 inches. Buy a silicone hose with roughly .25 inch walls and an ID of 3.25 inches and you have it made. It's a beautiful airbox and the engine breaths much better at higher RPM. Sound is a little louder and I find the engine is a little rougher until fully warmed up. (lot's more cold air coming in than stock)

Whats the price for the airbox? Is the airbox compatible to the to a 997 C2 also?

Pictures please?

First post said 3.8ltr engine-(S) and price! Final pictures would be nice!

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The airbox is around $700, the deck seal $10, the inlet hose around $50. I'm also going to add the air mass sensor wire extention as soon as it arrives from Germany. The stock airmass sensor is a direct fit but the stock wiring harness could be a little longer. The only item I have not addressed yet is the oil filler tube. I purchased the X-51 oil filler tube because it's shorter than the stock tube which does not fit up perfectly to the new airbox. The only problem is I can't figure out how to unbolt the stock oil filler tube without dropping the engine. If your hands are smaller maybe it could be accomplished but I can barely fit my hands deep enough to feel the oil filler bolts let alone actually get a socket on them. I'll take some pictures when I get a chance.

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The airbox is around $700, the deck seal $10, the inlet hose around $50. I'm also going to add the air mass sensor wire extention as soon as it arrives from Germany. The stock airmass sensor is a direct fit but the stock wiring harness could be a little longer. The only item I have not addressed yet is the oil filler tube. I purchased the X-51 oil filler tube because it's shorter than the stock tube which does not fit up perfectly to the new airbox. The only problem is I can't figure out how to unbolt the stock oil filler tube without dropping the engine. If your hands are smaller maybe it could be accomplished but I can barely fit my hands deep enough to feel the oil filler bolts let alone actually get a socket on them. I'll take some pictures when I get a chance.

I look forward to the pictures. Part numbers would be great too!

Is the Air cleaner the same ?

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The airbox is around $700, the deck seal $10, the inlet hose around $50. I'm also going to add the air mass sensor wire extention as soon as it arrives from Germany. The stock airmass sensor is a direct fit but the stock wiring harness could be a little longer. The only item I have not addressed yet is the oil filler tube. I purchased the X-51 oil filler tube because it's shorter than the stock tube which does not fit up perfectly to the new airbox. The only problem is I can't figure out how to unbolt the stock oil filler tube without dropping the engine. If your hands are smaller maybe it could be accomplished but I can barely fit my hands deep enough to feel the oil filler bolts let alone actually get a socket on them. I'll take some pictures when I get a chance.

Hullo fm540i

I have been thinking about this for a while to retrofit the x51 airbox , but I have a c2, I wonder if it will work on a c2. price sounds really fair. I see you are from chicago , so am I. what part of chicago are you from.

Ronnie

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The airbox is around $700, the deck seal $10, the inlet hose around $50. I'm also going to add the air mass sensor wire extention as soon as it arrives from Germany. The stock airmass sensor is a direct fit but the stock wiring harness could be a little longer. The only item I have not addressed yet is the oil filler tube. I purchased the X-51 oil filler tube because it's shorter than the stock tube which does not fit up perfectly to the new airbox. The only problem is I can't figure out how to unbolt the stock oil filler tube without dropping the engine. If your hands are smaller maybe it could be accomplished but I can barely fit my hands deep enough to feel the oil filler bolts let alone actually get a socket on them. I'll take some pictures when I get a chance.

You can gain access to the screws for the oil filler tube by removing the alternator. No engine R&R required.

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The airbox is around $700, the deck seal $10, the inlet hose around $50. I'm also going to add the air mass sensor wire extention as soon as it arrives from Germany. The stock airmass sensor is a direct fit but the stock wiring harness could be a little longer. The only item I have not addressed yet is the oil filler tube. I purchased the X-51 oil filler tube because it's shorter than the stock tube which does not fit up perfectly to the new airbox. The only problem is I can't figure out how to unbolt the stock oil filler tube without dropping the engine. If your hands are smaller maybe it could be accomplished but I can barely fit my hands deep enough to feel the oil filler bolts let alone actually get a socket on them. I'll take some pictures when I get a chance.

You can gain access to the screws for the oil filler tube by removing the alternator. No engine R&R required.

Thanks for your input...you have PM. Thanks..

Dave

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The airbox is around $700, the deck seal $10, the inlet hose around $50. I'm also going to add the air mass sensor wire extention as soon as it arrives from Germany. The stock airmass sensor is a direct fit but the stock wiring harness could be a little longer. The only item I have not addressed yet is the oil filler tube. I purchased the X-51 oil filler tube because it's shorter than the stock tube which does not fit up perfectly to the new airbox. The only problem is I can't figure out how to unbolt the stock oil filler tube without dropping the engine. If your hands are smaller maybe it could be accomplished but I can barely fit my hands deep enough to feel the oil filler bolts let alone actually get a socket on them. I'll take some pictures when I get a chance.

You can gain access to the screws for the oil filler tube by removing the alternator. No engine R&R required.

Thanks for your input...you have PM. Thanks..

Dave

I've just been looking through the Porsche parts list with a Porsche 'independent' here in the UK. It looks possible that the larger X-51 throttle body may well fit to the standard intake manifold - the gasket part number is the same for both, so the bolt centres must be the same! We are looking at buying an X-51 airbox, hose, throttle body and oil filler tube to see if they can be fitted directly to the standard intake manifold. If they can, it will be the best 'true' cold air kit ever made for the standard car! We will also be doing before and after dyno runs to see if there are any gains.

FWIW, cooler intake temps SHOULD equate to better power due to higher charge density. The X-51 airbox draws entirely cool air from outside the car where the standard airbox also draws hot air through the bottom of the box on the RH side. There's also the possibility of the engine breathing slightly better due to the design of the box and the bigger throttle body. Then again, the standard airbox / throttle body may not be the limiting factors so there may be no gains at all. Will report back in due course.

We are also going to be trying the cams / exhaust / ECU upgrade from 9ff in Germany. This offers (claims?) 395BHP with no airbox mods. Again we'll be checking the validity of the claims. The independent I'm speaking to in the UK has just taken on the franchise for 9ff and will use my car as a test mule.

Interesting times ahead!!

Ian W

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Ian - keep us informed on how you get on with this stuff - as another UK based 997S owner with the need for more power I'd like to know how you get on.

David

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The airbox is around $700, the deck seal $10, the inlet hose around $50. I'm also going to add the air mass sensor wire extention as soon as it arrives from Germany. The stock airmass sensor is a direct fit but the stock wiring harness could be a little longer. The only item I have not addressed yet is the oil filler tube. I purchased the X-51 oil filler tube because it's shorter than the stock tube which does not fit up perfectly to the new airbox. The only problem is I can't figure out how to unbolt the stock oil filler tube without dropping the engine. If your hands are smaller maybe it could be accomplished but I can barely fit my hands deep enough to feel the oil filler bolts let alone actually get a socket on them. I'll take some pictures when I get a chance.

You can gain access to the screws for the oil filler tube by removing the alternator. No engine R&R required.

Thanks for your input...you have PM. Thanks..

Dave

I've just been looking through the Porsche parts list with a Porsche 'independent' here in the UK. It looks possible that the larger X-51 throttle body may well fit to the standard intake manifold - the gasket part number is the same for both, so the bolt centres must be the same! We are looking at buying an X-51 airbox, hose, throttle body and oil filler tube to see if they can be fitted directly to the standard intake manifold. If they can, it will be the best 'true' cold air kit ever made for the standard car! We will also be doing before and after dyno runs to see if there are any gains.

FWIW, cooler intake temps SHOULD equate to better power due to higher charge density. The X-51 airbox draws entirely cool air from outside the car where the standard airbox also draws hot air through the bottom of the box on the RH side. There's also the possibility of the engine breathing slightly better due to the design of the box and the bigger throttle body. Then again, the standard airbox / throttle body may not be the limiting factors so there may be no gains at all. Will report back in due course.

We are also going to be trying the cams / exhaust / ECU upgrade from 9ff in Germany. This offers (claims?) 395BHP with no airbox mods. Again we'll be checking the validity of the claims. The independent I'm speaking to in the UK has just taken on the franchise for 9ff and will use my car as a test mule.

Interesting times ahead!!

Ian W

Ian

i was looking in to this as well, my carbon fiber box came in last week, mine is 3.6 engine. keep us posted on your progress.

cheer

Ronnie

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The X51 throttle body does fit, according to RSS here in the states who manafacturers a new intake distribution tube said the X51 throttle body will fit the non X51 intake.

Dave

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The X51 throttle body does fit, according to RSS here in the states who manafacturers a new intake distribution tube said the X51 throttle body will fit the non X51 intake.

Dave

This is looking good for the 'ultimate' CAI then? Airbox, throttle body, inlet hose and oil filler tube. The Porsche independent I mentioned has ordered the parts and I will be speaking to them again next week to arrange a time for a test fit. I'm not sure when I will be able to lend them the car but I will post back to this and other Porsche forums with impressions and dyno graphs after we're done.

We're also intending to do stock dyno runs, header and catalyst runs, header catalyst and airbox runs and then over the next couple of months, the 9ff cams / headers / cats / ECU both with and without the CAI kit above. We'll then hopefully be able to give the whole Porsche community out there some real independently tested feedback on what works and what doesn't and in what combinations. Whilst doing the dyno runs, we'll be carefully monitoring the engine coolant and intake temps to ensure no timing is being pulled by the ECU. All runs will be done using 99RON fuel.

Ian W

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The X51 throttle body does fit, according to RSS here in the states who manafacturers a new intake distribution tube said the X51 throttle body will fit the non X51 intake.

Dave

This is looking good for the 'ultimate' CAI then? Airbox, throttle body, inlet hose and oil filler tube. The Porsche independent I mentioned has ordered the parts and I will be speaking to them again next week to arrange a time for a test fit. I'm not sure when I will be able to lend them the car but I will post back to this and other Porsche forums with impressions and dyno graphs after we're done.

We're also intending to do stock dyno runs, header and catalyst runs, header catalyst and airbox runs and then over the next couple of months, the 9ff cams / headers / cats / ECU both with and without the CAI kit above. We'll then hopefully be able to give the whole Porsche community out there some real independently tested feedback on what works and what doesn't and in what combinations. Whilst doing the dyno runs, we'll be carefully monitoring the engine coolant and intake temps to ensure no timing is being pulled by the ECU. All runs will be done using 99RON fuel.

Ian W

See my latest blog for my thoughts on dyno testing... here.

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The X51 throttle body does fit, according to RSS here in the states who manafacturers a new intake distribution tube said the X51 throttle body will fit the non X51 intake.

Dave

This is looking good for the 'ultimate' CAI then? Airbox, throttle body, inlet hose and oil filler tube. The Porsche independent I mentioned has ordered the parts and I will be speaking to them again next week to arrange a time for a test fit. I'm not sure when I will be able to lend them the car but I will post back to this and other Porsche forums with impressions and dyno graphs after we're done.

We're also intending to do stock dyno runs, header and catalyst runs, header catalyst and airbox runs and then over the next couple of months, the 9ff cams / headers / cats / ECU both with and without the CAI kit above. We'll then hopefully be able to give the whole Porsche community out there some real independently tested feedback on what works and what doesn't and in what combinations. Whilst doing the dyno runs, we'll be carefully monitoring the engine coolant and intake temps to ensure no timing is being pulled by the ECU. All runs will be done using 99RON fuel.

Ian W

Thanks Ian...I wanted to do this right now as well but I am leaving to Japan for about a month...I got all my exhaust parts-X51 headers, AWE 200cpi HJS metallic cats and mufflers (although I am switching to Borla). I am about ready to pull the trigger here in the states for the X51 airbox, throttlebody, airtube and oil tube. I am also considering doing the RSS intake plenum along with this.

Good luck on your endeavour and please fill us in...waiting with baited breath....

Dave

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The X51 throttle body does fit, according to RSS here in the states who manafacturers a new intake distribution tube said the X51 throttle body will fit the non X51 intake.

Dave

This is looking good for the 'ultimate' CAI then? Airbox, throttle body, inlet hose and oil filler tube. The Porsche independent I mentioned has ordered the parts and I will be speaking to them again next week to arrange a time for a test fit. I'm not sure when I will be able to lend them the car but I will post back to this and other Porsche forums with impressions and dyno graphs after we're done.

We're also intending to do stock dyno runs, header and catalyst runs, header catalyst and airbox runs and then over the next couple of months, the 9ff cams / headers / cats / ECU both with and without the CAI kit above. We'll then hopefully be able to give the whole Porsche community out there some real independently tested feedback on what works and what doesn't and in what combinations. Whilst doing the dyno runs, we'll be carefully monitoring the engine coolant and intake temps to ensure no timing is being pulled by the ECU. All runs will be done using 99RON fuel.

Ian W

See my latest blog for my thoughts on dyno testing... here.

I responded...there is power in the exhaust, maybe not as much as claimed but there is power to be had.

dave

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The X51 throttle body does fit, according to RSS here in the states who manafacturers a new intake distribution tube said the X51 throttle body will fit the non X51 intake.

Dave

I am not clear, if the x51 throttle body(which is larger then the stock one) does fit the non x51 intake (which is smaller then the x51 intake manifold, then how does the inside diameteres match up

x51 ID verses the non z51 intake manifold ID , ?/ or are they the same.

Ronnie

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The X51 throttle body does fit, according to RSS here in the states who manafacturers a new intake distribution tube said the X51 throttle body will fit the non X51 intake.

Dave

I am not clear, if the x51 throttle body(which is larger then the stock one) does fit the non x51 intake (which is smaller then the x51 intake manifold, then how does the inside diameteres match up

x51 ID verses the non z51 intake manifold ID , ?/ or are they the same.

Ronnie

Sorry Ronnie didn't see this..you have to remember that the throttle body doesn't connect to the intake manifold directly. It connects to a plastic intake distribution tube commonly called the "plenum", this is the part that RSS has done through the aftermarket. As far as the X51 throttle body ID vs. this part, well this is the million $ question. Whats nice about the factory piece being plastic you can probably grind it down to gasket match this and you could probalby do it with the RSS aluminum part as well. I was told by RSS that the X51 TB does fit. Haven't seen this myself though...(my disclaimer :D)

Dave

Edited by Dave07997S

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The X51 throttle body does fit, according to RSS here in the states who manafacturers a new intake distribution tube said the X51 throttle body will fit the non X51 intake.

Dave

I am not clear, if the x51 throttle body(which is larger then the stock one) does fit the non x51 intake (which is smaller then the x51 intake manifold, then how does the inside diameteres match up

x51 ID verses the non z51 intake manifold ID , ?/ or are they the same.

Ronnie

Sorry Ronnie didn't see this..you have to remember that the throttle body doesn't connect to the intake manifold directly. It connects to a plastic intake distribution tube commonly called the "plenum", this is the part that RSS has done through the aftermarket. As far as the X51 throttle body ID vs. this part, well this is the million $ question. Whats nice about the factory piece being plastic you can probably grind it down to gasket match this and you could probalby do it with the RSS aluminum part as well. I was told by RSS that the X51 TB does fit. Haven't seen this myself though...(my disclaimer :D)

Dave

thanks dave , i really meant the plenul, the irony is i already fitted the rss plenum in the car. I also have the airbox , filler tube, sitting in my house. I was thinking about just getting a silicone transition tube from the throttle body to air inlet hose. i am not sure how much the throttle body is . have you ordered your stuff yet

ronnie

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The X51 throttle body does fit, according to RSS here in the states who manafacturers a new intake distribution tube said the X51 throttle body will fit the non X51 intake.

Dave

I am not clear, if the x51 throttle body(which is larger then the stock one) does fit the non x51 intake (which is smaller then the x51 intake manifold, then how does the inside diameteres match up

x51 ID verses the non z51 intake manifold ID , ?/ or are they the same.

Ronnie

Sorry Ronnie didn't see this..you have to remember that the throttle body doesn't connect to the intake manifold directly. It connects to a plastic intake distribution tube commonly called the "plenum", this is the part that RSS has done through the aftermarket. As far as the X51 throttle body ID vs. this part, well this is the million $ question. Whats nice about the factory piece being plastic you can probably grind it down to gasket match this and you could probalby do it with the RSS aluminum part as well. I was told by RSS that the X51 TB does fit. Haven't seen this myself though...(my disclaimer :D)

Dave

thanks dave , i really meant the plenul, the irony is i already fitted the rss plenum in the car. I also have the airbox , filler tube, sitting in my house. I was thinking about just getting a silicone transition tube from the throttle body to air inlet hose. i am not sure how much the throttle body is . have you ordered your stuff yet

ronnie

Hey Ronnie, not yet. Do you have the template for cutting the lower deck for the 2nd airtube??

I saw your post regarding the oil filler tube and the alternator. I will see if I can find out how to do this. I am leaving to Japan for a few weeks, and I will probably order it when I get back.

Dave

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