Nitro V8 Posted July 30, 2023 Report Share Posted July 30, 2023 Hi all Thinking of doing the 74mm tb conversion on my 2003 3.2. I will probably use the Uniwerks carbon plenum/kit. My question is which 74mm tb should I use? Does it matter if it is from a 996 or a 987 or any other model. Or is there a specific one I should get? Thank you Quote Link to comment Share on other sites More sharing options...
Lonewolfgjp Posted July 30, 2023 Report Share Posted July 30, 2023 Hi there I think you have got a few options, I used the one off the gen1 Cayman 3.4 but you can use the 996 one as well. There maybe some others you can use as well 👍 Quote Link to comment Share on other sites More sharing options...
Nitro V8 Posted July 30, 2023 Author Report Share Posted July 30, 2023 47 minutes ago, Lonewolfgjp said: Hi there I think you have got a few options, I used the one off the gen1 Cayman 3.4 but you can use the 996 one as well. There maybe some others you can use as well 👍 Hi. That’s great, thank you. Quote Link to comment Share on other sites More sharing options...
Patt Posted July 31, 2023 Report Share Posted July 31, 2023 If you research, you'll find a list of cars and the Bosch part numbers too. It's much cheaper to use the 996 factory plenum, but it's your choice Quote Link to comment Share on other sites More sharing options...
Nitro V8 Posted July 31, 2023 Author Report Share Posted July 31, 2023 Has anybody tried an 82mm tb with an adaptor down to a 78mm plenum? would this have any benefit at all over the 78mm tb? Just a thought as I have seen a cheapish 82 for sale. Quote Link to comment Share on other sites More sharing options...
Nitro V8 Posted July 31, 2023 Author Report Share Posted July 31, 2023 2 hours ago, Patt said: If you research, you'll find a list of cars and the Bosch part numbers too. It's much cheaper to use the 996 factory plenum, but it's your choice Thank’s for pointing me in the right direction. I will have a read up. Cheers Quote Link to comment Share on other sites More sharing options...
Patt Posted July 31, 2023 Report Share Posted July 31, 2023 Berty on here did an article on the 987 that is just as relevant to 986. Both myself and EDC have posted in our threads about our builds using the larger TB too. 1 Quote Link to comment Share on other sites More sharing options...
½cwt Posted July 31, 2023 Report Share Posted July 31, 2023 2 hours ago, Nitro V8 said: Has anybody tried an 82mm tb with an adaptor down to a 78mm plenum? would this have any benefit at all over the 78mm tb? Just a thought as I have seen a cheapish 82 for sale. Other than creating a blockage through the effective restrictor... 1 Quote Link to comment Share on other sites More sharing options...
edc Posted July 31, 2023 Report Share Posted July 31, 2023 I've posted parts and price and pics before. 996 plenum was about £35. I've still got the bits I think in my garage to do this second time around on what was my new to me 550 coming up 10 years ago 1 1 Quote Link to comment Share on other sites More sharing options...
Nitro V8 Posted August 1, 2023 Author Report Share Posted August 1, 2023 8 hours ago, edc said: I've posted parts and price and pics before. 996 plenum was about £35. I've still got the bits I think in my garage to do this second time around on what was my new to me 550 coming up 10 years ago Hi I'm struggling finding any photo's of the install so I can understand the pipework lengths etc. The photo's in your thread are no longer live. Does anybody have any photo's that may help? Thank you in advance P.S. Quote Link to comment Share on other sites More sharing options...
Patt Posted August 1, 2023 Report Share Posted August 1, 2023 Ony one I could find. The 80mm pipe I think was a meter long an most. The tricky bit was cutting the elbow to the TB 1 Quote Link to comment Share on other sites More sharing options...
Nitro V8 Posted August 1, 2023 Author Report Share Posted August 1, 2023 That's great, thank you! Are the 74mm 911 plenum outlets the same size as the 986 68mm plenum's or is there a step in size? Cheers Quote Link to comment Share on other sites More sharing options...
Patt Posted August 1, 2023 Report Share Posted August 1, 2023 they are larger to suit the larger TB they were designed for.. You'll need to stretch the joiner hose, or stick it in a bucket of hot water first. 1 Quote Link to comment Share on other sites More sharing options...
edc Posted August 1, 2023 Report Share Posted August 1, 2023 (edited) The mod design is actually very simple. A 1 foot length of pipe and 2 90 Deg bend silicone hoses plus around half a dozen jubilee clips. The art and skill is the trimming of the silicone hose to fit the shapes/angle/contour of the TB and MAF pipe. Edit - plus the longer bolts for the TB. Edited August 1, 2023 by edc 1 Quote Link to comment Share on other sites More sharing options...
map Posted August 1, 2023 Report Share Posted August 1, 2023 Here’s my current set-up 74mmTB - - 2x45 degree and 1x90 degree plus silicon connectors and clamps. Photos show routing and assembly Happy to answer any questions. 1 Quote Link to comment Share on other sites More sharing options...
Nitro V8 Posted August 1, 2023 Author Report Share Posted August 1, 2023 Patt, edc and map. Thank you all very much for the guidance and photo's. A great help. 👍 Quote Link to comment Share on other sites More sharing options...
Nitro V8 Posted August 1, 2023 Author Report Share Posted August 1, 2023 A few more questions please. 1) I found edc parts list and it says 12” Ali pipe 83mm id. I think this should be od as that is how they tend to be sold and it matches the id of the silicone elbows? 2) I can only find 80mm od Ali tube (auto silicone hoses) so is that ok? 3) They sell a beaded version so is 12” accurate enough to order beaded or did it need cutting down? 4) There is a choice of id for the silicone elbows of 80mm or 83mm. edc parts description says 83mm. Would 80mm be better to match Ali tube or will this struggle going over the 74mm throttle body or maf housing? If the internal of the tb is 74mm I can only think the wall thickness would be a couple of mm so 78mm max od? Is the maf housing tight for a 80mm id silicone hose? Thank you Quote Link to comment Share on other sites More sharing options...
map Posted August 1, 2023 Report Share Posted August 1, 2023 @Nitro V8 - various options here: https://www.demon-tweeks.com/automotive-plumbing-solutions-aluminium-air-coolant-intercooler-pipe-400863/?sku=APSCP9089&istCompanyId=a2904180-3a7d-4e56-b876-cf81c9512180&istFeedId=6fbc4b04-fd28-4ce1-8513-835c8f118690&istItemId=wptiipmli&istBid=t&gclid=EAIaIQobChMI2_nvq8b8_AIVDbDtCh1ONQtYEAQYAiABEgKxjvD_BwE&gclsrc=aw.ds 1 Quote Link to comment Share on other sites More sharing options...
map Posted August 1, 2023 Report Share Posted August 1, 2023 @Nitro V8 - my system runs 74mm ID from cone filter to TB. 1 Quote Link to comment Share on other sites More sharing options...
edc Posted August 1, 2023 Report Share Posted August 1, 2023 There's lots of ways to slice the cake. When I did it there was nobody to copy so if it was a company doing it you'd call it development, or guess work for a home garage DIY! I actually bought a several metre length of drain pipe to model with and was originally looking at Marley and other similar plumbing and drainage products to mock up a design 😁 I didn't have the patience or time to develop it further. Once a working design was on that was it, it stayed on. There was no thought to optimise it. IIRC, @Patt when we came to do the same on @Patt car the silicone hose ID was 80mm. If I was to do it again I'd likely aim for something more like @map version where the bends are less of a tight angle but I didn't want to spend lots of money buying and cutting up parts to figure out a slightly more complete design. A flattened out U shape fitted easily and the parts were easily buyable then. 1 Quote Link to comment Share on other sites More sharing options...
Nitro V8 Posted August 2, 2023 Author Report Share Posted August 2, 2023 Thank you for all the replies. Hopefully when I do mine I can take plenty of photo's and maybe we can put it in a "how to" section so others can benefit from all the good work you guys have done. Cheers 1 Quote Link to comment Share on other sites More sharing options...
Nitro V8 Posted August 3, 2023 Author Report Share Posted August 3, 2023 Hopefully last question! Does anybody know the od of the maf tube where the new silicone elbow will join up to? Just so I can get exact size fit. Thank you Quote Link to comment Share on other sites More sharing options...
Nitro V8 Posted August 3, 2023 Author Report Share Posted August 3, 2023 (edited) Ignore the above, I’ve found the answer it is 3” 76mm. So it goes down from 76mm at the maf to 68mm at the throttle body. Interestingly the 996 maf tube is 31/2” 90mm. Goes down from 90mm at the maf to 74mm at the throttle body. I wonder if that is to accelerate the airflow? I therefore wonder if we are doing the 74mm tb and plenum conversion on our 986’s should we be using a 90mm maf tube? Edited August 3, 2023 by Nitro V8 Quote Link to comment Share on other sites More sharing options...
map Posted August 3, 2023 Report Share Posted August 3, 2023 1 hour ago, Nitro V8 said: I therefore wonder if we are doing the 74mm tb and plenum conversion on our 986’s should we be using a 90mm maf tube? Be careful of MAF sensor housing (you mentioned maf tube) dimensions - my understanding is that the MAF:Housing ratios are calibrated in some way. I see that the Bosch MAF listed for 986 2.7 & 3.2 is the same part number as that listed for Porsche 996 3.6cc 2002 + Porsche 997 C2 / C4 3.6L, 3.8L & Porsche 997 MKII 2009 Based on some motorsport feedback of a few years ago I retain a nagging doubt there's some form of engine config specific calibration - maybe it's in the engine's mapping? Happy for anyone with specific knowledge to share that along with supporting engineering type info. Quote Link to comment Share on other sites More sharing options...
Patt Posted August 3, 2023 Report Share Posted August 3, 2023 yeah - don't touch or move the MAF or it's tube - even moving it's location can cause issues that would require a re-map to fix properly. And the 986 Anniv is more of a 987 intake, thus very different. Quote Link to comment Share on other sites More sharing options...
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