btjtaylor
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- Accord CU2 Manual
A common upgrade for K-Series engines is changing the intake manifold. Generally speaking, these swap a little low end torque for increased high end power. Additionally, at least in my opinion, they do also look a lot cooler in the engine bay than the (partially) plastic one our cars received!
The actual choice of intake manifold is a very divisive one - I think most can agree that the RRC manifold (From the JDM Civic Type R FD2) is probably the "best" for peak power but it's also expensive to buy, around £600. I went for the RSP manifold from the FN2 as with the improved T7Design trumpets installed it appears to perform just as well for a lot less (~£250 in total) -
- there are also some cheap manifolds available on eBay that are copies of Skunk2 parts but to be honest, I would go for an OEM one as the build quality is much better.
Parts I used:
A suitable intake manifold - I went with the RSP from FN2 Civic Type R for £100 from Facebook Marketplace - I was quite lucky as it was new in box. One good thing about the RSP is that it has a removable plenum cover so you can open it to clean it/port it as desired, so I don't think a used one would be too much of a problem, even high mileage. I also fitted the T7Design trumpets inside the manifold https://www.t7design.co.uk/honda-k20z4-rsp-inlet-manifold-velocity-stack-raw-billet-810-ad3-2d3.html - or alternatively you can also fit RRC/RBC/etc. manifolds with the adapter kit below as long as they have a coolant port. If they don't have a coolant port, or you are feeling brave you can fit a coolant bypass adapter to the head as per the Milan Mastracci video - I didn't go down this route myself, particularly as you have to tap a thread into the head.
PRL intake manifold and (stock) throttle body adapter kit https://prlmotorsports.com/products...1&_sid=ecbef6249&_ss=r&variant=41433242468545
P2R injector adapters and rail spacers
https://powerrevracing.com/products/9th-gen-si-injector-adapters-rbc-manifold
Alternatively you could also fit RDX or other suitable injectors with appropriate wiring harness adapters e.g. https://prlmotorsports.com/products/2012-2015-9th-gen-civic-rdx-injector-plug-n-play-clips
Drill and die grinding bit to port match the throttle body opening (I used this one https://www.amazon.co.uk/gp/product/B0931QMZYR/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1)
The RSP is 62mm and the stock throttle body is 64.5mm so you don't need to remove a huge amount of material
Throttle body wiring extension harness:
The connector for the throttle body no longer reaches its new position so I purchased this pre-wired connector from Aliexpress (https://www.aliexpress.com/item/100...o.order_list.order_list_main.5.3bed1802NQ0SHo), cut off the original connector and crimped it onto the wiring to extend the length.
There is a plug and play extension harness sold from the USA but it's extremely expensive for what it is (https://www.casperselectronics.com/cart/index.php?route=product/product&product_id=881)
DC5/EP3 "extra clearance" upper radiator hose - Gates part number 21229 - not strictly necessary but moves the hose away from the throttle body area making it easier to connect intake piping. https://www.ebay.co.uk/itm/404025369437?_ul=GB
Approx 6 litres of coolant to refill the system after draining. I used Comma Xstream G30 ready mixed coolant as it's what my local motor factors had - Honda OEM probably better but i'm sure it doesn't make a huge difference. A spill-free funnel is a good tool to have for this - I recently invested in a Sealey VS0045 which I can fully recommend.
Gasket paper (I used a sheet of Flexoid 1.6mm paper and cut it with a snap-off knife) to create a gasket from the TB adapter to manifold, if required.
4x Stock injector o-rings. Mine were badly perished so I would recommend replacing them regardless of condition for peace of mind. (Honda part number 91302-R40-A11 - I got mine from Cox Motor Parts. Not hugely expensive around £12 inc delivery.)
Hose tee with 10mm-4mm-10mm fittings for connecting a vacuum line to run to the "vacuum ***isted" engine mount solenoid - I used https://www.ebay.co.uk/itm/280632956898
A can of spray silicone lubricant to aid installing hoses/o-rings.
Some 10mm I/D hose and appropriate clamps to re-run any vacuum hoses as required
3/8" vacuum port plug for for the port nearest the fuel rail on the manifold as it won't be used. I bought https://www.ebay.co.uk/itm/134787543181 and also plugged the throttle body coolant ports with them.
Liquid PTFE thread sealant for the coolant plug in the manifold and the vacuum line barb in the throttle body adapter plate
Installation notes:
There is a great video from Milan Mastracci who does a great job of explaining the steps which i'd recommend watching first
He used the coolant bypass method rather than the PRL adapter but the rest of it is (mostly) the same
I recommend draining the coolant out of the radiator drain plug first to avoid any mess, especially if you're going to replace radiator and coolant hoses etc. A good opportunity to refresh the coolant regardless!
The parts in the PRL kit aren't labelled so i've done my best to annotate below!
Once the factory manifold is removed all 3 of the mounting studs need to be removed first before you attempt to install the manifold. It's not possible to get the manifold into place with them installed. You can use a stud remover tool or the "2 nut" method to wind them out of the head. The PRL kit comes with 2x replacement studs which replace the two studs on the top section of the manifold. The third stud near the coolant port is not used and replaced with a bolt.
The top left bolt of the manifold has bad access due to our belt setup being placed a bit more awkwardly than on the Civic. You have to put a single bolt in the right hand side of the manifold, then rotate it up and out of the way, put the bolt through the manifold and adapter, then rotate it back into position and tighten the bolt.
Our cars have a vacuum controlled engine mount which is mounted to the stock manifold, the mounting point for which no longer exists on the replacement manifold. I tucked the corner of its bracket behind the top left bolt for the manifold as shown below. I've not had any issues with this but If you wanted a more solid attachment you could possibly bend the bracket and bolt the manifold through it
There is a vacuum line going to the engine mount solenoid which needs to be plumbed in. I used a 10mm/4mm/10mm tee as above connected to the nearest vacuum line.
The actual choice of intake manifold is a very divisive one - I think most can agree that the RRC manifold (From the JDM Civic Type R FD2) is probably the "best" for peak power but it's also expensive to buy, around £600. I went for the RSP manifold from the FN2 as with the improved T7Design trumpets installed it appears to perform just as well for a lot less (~£250 in total) -
Parts I used:
A suitable intake manifold - I went with the RSP from FN2 Civic Type R for £100 from Facebook Marketplace - I was quite lucky as it was new in box. One good thing about the RSP is that it has a removable plenum cover so you can open it to clean it/port it as desired, so I don't think a used one would be too much of a problem, even high mileage. I also fitted the T7Design trumpets inside the manifold https://www.t7design.co.uk/honda-k20z4-rsp-inlet-manifold-velocity-stack-raw-billet-810-ad3-2d3.html - or alternatively you can also fit RRC/RBC/etc. manifolds with the adapter kit below as long as they have a coolant port. If they don't have a coolant port, or you are feeling brave you can fit a coolant bypass adapter to the head as per the Milan Mastracci video - I didn't go down this route myself, particularly as you have to tap a thread into the head.
PRL intake manifold and (stock) throttle body adapter kit https://prlmotorsports.com/products...1&_sid=ecbef6249&_ss=r&variant=41433242468545
P2R injector adapters and rail spacers
https://powerrevracing.com/products/9th-gen-si-injector-adapters-rbc-manifold
Alternatively you could also fit RDX or other suitable injectors with appropriate wiring harness adapters e.g. https://prlmotorsports.com/products/2012-2015-9th-gen-civic-rdx-injector-plug-n-play-clips
Drill and die grinding bit to port match the throttle body opening (I used this one https://www.amazon.co.uk/gp/product/B0931QMZYR/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1)
The RSP is 62mm and the stock throttle body is 64.5mm so you don't need to remove a huge amount of material
Throttle body wiring extension harness:
The connector for the throttle body no longer reaches its new position so I purchased this pre-wired connector from Aliexpress (https://www.aliexpress.com/item/100...o.order_list.order_list_main.5.3bed1802NQ0SHo), cut off the original connector and crimped it onto the wiring to extend the length.
There is a plug and play extension harness sold from the USA but it's extremely expensive for what it is (https://www.casperselectronics.com/cart/index.php?route=product/product&product_id=881)
DC5/EP3 "extra clearance" upper radiator hose - Gates part number 21229 - not strictly necessary but moves the hose away from the throttle body area making it easier to connect intake piping. https://www.ebay.co.uk/itm/404025369437?_ul=GB
Approx 6 litres of coolant to refill the system after draining. I used Comma Xstream G30 ready mixed coolant as it's what my local motor factors had - Honda OEM probably better but i'm sure it doesn't make a huge difference. A spill-free funnel is a good tool to have for this - I recently invested in a Sealey VS0045 which I can fully recommend.
Gasket paper (I used a sheet of Flexoid 1.6mm paper and cut it with a snap-off knife) to create a gasket from the TB adapter to manifold, if required.
4x Stock injector o-rings. Mine were badly perished so I would recommend replacing them regardless of condition for peace of mind. (Honda part number 91302-R40-A11 - I got mine from Cox Motor Parts. Not hugely expensive around £12 inc delivery.)
Hose tee with 10mm-4mm-10mm fittings for connecting a vacuum line to run to the "vacuum ***isted" engine mount solenoid - I used https://www.ebay.co.uk/itm/280632956898
A can of spray silicone lubricant to aid installing hoses/o-rings.
Some 10mm I/D hose and appropriate clamps to re-run any vacuum hoses as required
3/8" vacuum port plug for for the port nearest the fuel rail on the manifold as it won't be used. I bought https://www.ebay.co.uk/itm/134787543181 and also plugged the throttle body coolant ports with them.
Liquid PTFE thread sealant for the coolant plug in the manifold and the vacuum line barb in the throttle body adapter plate
Installation notes:
There is a great video from Milan Mastracci who does a great job of explaining the steps which i'd recommend watching first
I recommend draining the coolant out of the radiator drain plug first to avoid any mess, especially if you're going to replace radiator and coolant hoses etc. A good opportunity to refresh the coolant regardless!
The parts in the PRL kit aren't labelled so i've done my best to annotate below!
Once the factory manifold is removed all 3 of the mounting studs need to be removed first before you attempt to install the manifold. It's not possible to get the manifold into place with them installed. You can use a stud remover tool or the "2 nut" method to wind them out of the head. The PRL kit comes with 2x replacement studs which replace the two studs on the top section of the manifold. The third stud near the coolant port is not used and replaced with a bolt.
The top left bolt of the manifold has bad access due to our belt setup being placed a bit more awkwardly than on the Civic. You have to put a single bolt in the right hand side of the manifold, then rotate it up and out of the way, put the bolt through the manifold and adapter, then rotate it back into position and tighten the bolt.
Our cars have a vacuum controlled engine mount which is mounted to the stock manifold, the mounting point for which no longer exists on the replacement manifold. I tucked the corner of its bracket behind the top left bolt for the manifold as shown below. I've not had any issues with this but If you wanted a more solid attachment you could possibly bend the bracket and bolt the manifold through it
There is a vacuum line going to the engine mount solenoid which needs to be plumbed in. I used a 10mm/4mm/10mm tee as above connected to the nearest vacuum line.
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