GT intake tubes
12-31-2005, 05:38 AM
#1
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GT intake tubes
I see that there has been a lot of debate on the effect on insulated tubes, modified tubes etc. (bottom line seems to be no real difference in power or engine sound?)
The tubes (insulated type) on my 91 GT is in bad condition and I am about to replace them. Since the insulated ones are very expensive and the "normal" plastic ones are very cheap I think I will go for those.
Just a few questions:
1. Was any GT's delivered without insulated tubes?
2. Any reason why I should not go for the cheap ones?
3. Any of you been successful in repairing / re-insulating the original ones?
Thanks in advance and happy New Year
!
The tubes (insulated type) on my 91 GT is in bad condition and I am about to replace them. Since the insulated ones are very expensive and the "normal" plastic ones are very cheap I think I will go for those.
Just a few questions:
1. Was any GT's delivered without insulated tubes?
2. Any reason why I should not go for the cheap ones?
3. Any of you been successful in repairing / re-insulating the original ones?
Thanks in advance and happy New Year
!
12-31-2005, 06:23 AM
#2
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Regards undesired heating of the intake air in a normally aspirated 928, I offer the view that it is inconsequential - and can be ignored.
You can adapt any tubes that fit, as long as they do not impede air flow. Normal S4 tubes have venturi chambers ( tapers) for ** intake noise control - and perhaps some other esoteric function - like being able to fit under the cross bar
.
The issue of cooling intake air/avoiding excessive heating came up some time ago and I posted a small calculation - which will not be repeated here. Bottom line(s), knowing that dry air is the nearly perfect insulator ( second only to vacuum) and has a very low heat exchange rate, it would take some finite time to heat the inlet charge.
The residence time inside these tubes is a function of their summed internal volumes verses the volumetric demand of a 5l engine at a particular rpm ( x 0.5, being a 4-cycle).
The air hangs around in the tubes for mere fractions of a second .... ** can't have audible noise unless a threshold internal velocity is exceeded.
Excuse the length - just having a poke at Porsche 'uber-engineering'
Best of the New Year!
You can adapt any tubes that fit, as long as they do not impede air flow. Normal S4 tubes have venturi chambers ( tapers) for ** intake noise control - and perhaps some other esoteric function - like being able to fit under the cross bar
.The issue of cooling intake air/avoiding excessive heating came up some time ago and I posted a small calculation - which will not be repeated here. Bottom line(s), knowing that dry air is the nearly perfect insulator ( second only to vacuum) and has a very low heat exchange rate, it would take some finite time to heat the inlet charge.
The residence time inside these tubes is a function of their summed internal volumes verses the volumetric demand of a 5l engine at a particular rpm ( x 0.5, being a 4-cycle).
The air hangs around in the tubes for mere fractions of a second .... ** can't have audible noise unless a threshold internal velocity is exceeded.
Excuse the length - just having a poke at Porsche 'uber-engineering'
Best of the New Year!
12-31-2005, 08:03 AM
#3
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GT's in the US came with the plastic tubes. The insulated ones showed up on the GTS.
The insulated ones were installed due to stricter noise requirements.
Use the plastic ones and save yourself the $$.
The insulated ones were installed due to stricter noise requirements.
Use the plastic ones and save yourself the $$.
12-31-2005, 08:23 AM
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GT's in the US came with the plastic tubes. The insulated ones showed up on the GTS.
if you have isolated ones they have been added separately by previous owner.
You can definitely use the plastic one and will not notice any difference.
Cheers/Peter
12-31-2005, 10:15 AM
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Are you sure that no GT's (or even late S4's) came original with insulated intake tubes? I think I have seen quite a few late GTs with such tubes...
Anyway, I have decided to go for the plastic ones for replacement (I hope that this was the original on my car then... )
Anyway, I have decided to go for the plastic ones for replacement (I hope that this was the original on my car then...
)
12-31-2005, 10:19 AM
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Are you sure that no GT's (or even late S4's) came original with insulated intake tubes?
Then again there is always an exception with Porsche
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12-31-2005, 10:19 AM
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Originally Posted by 928-Viking
Are you sure that no GT's (or even late S4's) came original with insulated intake tubes? I think I have seen quite a few late GTs with such tubes...
Anyway, I have decided to go for the plastic ones for replacement (I hope that this was the original on my car then... )
Anyway, I have decided to go for the plastic ones for replacement (I hope that this was the original on my car then...
)
12-31-2005, 10:48 AM
#9
Nordschleife Master
From the research done I believe the straight, insulated tubes may be of value on engines near and above 350hp output. The venturi tubes are good through 330hp or so. Not totally precise, but that's the ballpark numbers.
12-31-2005, 11:10 AM
#10
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Just out of interest how much do the venturi tubes go for ?
I replaced my POS GTS originals (this is a quite anacceptable design/materials - and price) with some aftermarket fiberglass/neoprene tubes and reused the GTS tube ends for a good looking result. Several folks have looked at the engine and not even noticed the tube swap (I was surprised).
I didnt really coinsider the plastic tubes - I think I paid about $80 to do the pair and had about 2' left so could have saved some more money on materials... I'm happy with the results
Alan
I replaced my POS GTS originals (this is a quite anacceptable design/materials - and price) with some aftermarket fiberglass/neoprene tubes and reused the GTS tube ends for a good looking result. Several folks have looked at the engine and not even noticed the tube swap (I was surprised).
I didnt really coinsider the plastic tubes - I think I paid about $80 to do the pair and had about 2' left so could have saved some more money on materials... I'm happy with the results
Alan
12-31-2005, 11:14 AM
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I got some aftermarket intake tubes from Bill Sanders and 4 rubber connectors from Home Depot for 3" pipe. Perfect fit, work fine. I know there's no real advantage, but it's not a performance 'downgrade'.
Bumblebee???
BTW, total cost like $33.
Bumblebee???
BTW, total cost like $33.
12-31-2005, 11:59 AM
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Are you sure that no GT's (or even late S4's) came original with insulated intake tubes? I think I have seen quite a few late GTs with such tubes...
There is as always with Porsche exceptions, one was the cars for Swiss market that had a different tube with a sand filter in the middle
Anyway, the venturi plastic type will work just fine.
I have seen a few GTS owners using them with no problems.
Cheers/Peter
12-31-2005, 01:50 PM
#14
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agreed
Originally Posted by Garth S
Regards undesired heating of the intake air in a normally aspirated 928, I offer the view that it is inconsequential - and can be ignored.
You can adapt any tubes that fit, as long as they do not impede air flow. Normal S4 tubes have venturi chambers ( tapers) for ** intake noise control - and perhaps some other esoteric function - like being able to fit under the cross bar .
The issue of cooling intake air/avoiding excessive heating came up some time ago and I posted a small calculation - which will not be repeated here. Bottom line(s), knowing that dry air is the nearly perfect insulator ( second only to vacuum) and has a very low heat exchange rate, it would take some finite time to heat the inlet charge.
The residence time inside these tubes is a function of their summed internal volumes verses the volumetric demand of a 5l engine at a particular rpm ( x 0.5, being a 4-cycle).
The air hangs around in the tubes for mere fractions of a second .... ** can't have audible noise unless a threshold internal velocity is exceeded.
Excuse the length - just having a poke at Porsche 'uber-engineering' Best of the New Year!
You can adapt any tubes that fit, as long as they do not impede air flow. Normal S4 tubes have venturi chambers ( tapers) for ** intake noise control - and perhaps some other esoteric function - like being able to fit under the cross bar
.The issue of cooling intake air/avoiding excessive heating came up some time ago and I posted a small calculation - which will not be repeated here. Bottom line(s), knowing that dry air is the nearly perfect insulator ( second only to vacuum) and has a very low heat exchange rate, it would take some finite time to heat the inlet charge.
The residence time inside these tubes is a function of their summed internal volumes verses the volumetric demand of a 5l engine at a particular rpm ( x 0.5, being a 4-cycle).
The air hangs around in the tubes for mere fractions of a second .... ** can't have audible noise unless a threshold internal velocity is exceeded.
Excuse the length - just having a poke at Porsche 'uber-engineering'
Best of the New Year!