Madjak

Hi all,

I figured I'd make this a new topic as the old Honda Intake thread is very long as is more focused on cutting and welding on the existing Mazda intake flange. I'm going about this a little differently and thought I'd document it here as to how well / if it works.

OK so I have a NA8 built motor and I've just purchased a Skunk2 ultra street manifold and Skunk2 alpha throttle body. I chose this manifold over a Skunk2 Pro because of the taper at the rear of the throttle body. My car is RHD so I need clearance around the brake master cylinder. It also as close to ideal runner lengths for the high RPMs I run.



My plan is to drill / slot the existing flange on this manifold and port match it to my existing ported NA8 head. I've mocked up the bolt hole locations and nearly all can be machined directly into the existing flange. This means my only major modifications to the manifold will be the removal of the injector port holes and humps. I'm not sure yet how well the runners will match to my existing head but they should be close. I'd probably run as is until I rebuild my engine later this year where I can port match a bit better.



The above image was my initial mockup. I'm just going to space the top right bolt hole and clamp the flange with a washer. The benefit to this manifold is that it already has nice flat areas machined into the back face of the flange, right where my new mounting holes need to sit.



Placement wise, I made a scale printout and mocked out the location. It hard to see in the below photo by the manifold will sit very close to the triangular supports that come off the chassis rails to the stut tops. I'll have to move the biasing valve out of the way. Also this manifold comes out straighter than the Skunk2 Pro so it will sit down in the bay a bit more. This might make the fitment tighter than what I wanted but I doubt a Skunk2 Pro would fit past the brake master on a RHD car. The throttle body on this manifold is also angled nicely back into the engine bay. It should help the air intake miss the pop-up headlight mechanism.



I should have the parts in the next 3 weeks. My plan is to fit to the engine and upgrade to E85 and 1000cc injectors at the same time. I'll get the engine dyno'd with and without E85 so I can compare to the stock NA8 intake. Later in the year I'm looking at slapping on a Rotrex and boosting the engine for some more serious power.

NiklasFalk

iTrader: (1)

Being an ***;
How much have you sunk into the BP head to prevent the increased flow of going to a BP4W (NB8) or a BP6D?
It seems like the best flowing BP heads are just on par with an untouched BP4W/BP6D.

There is a risk that a BP4W with a simple flattop can be just as efficient as your elaborate plan.

But you will never know until somone tries solutions back to back.

Madjak

I purchased this entire engine complete already built and ported. The head is seriously ported with very oversized valves and extremely high deg (315+) cams. With a stock NA8 intake i'm getting around 165hp at the wheels. Its working well already and I think the limitation is the manifold atm. This test is to see if that is true or not.

A new ported head, cams and square top would be a substantial investment and i'm not sure how much extra power it would give over this manifold and my existing head. Given this is only going to cost me less than $300 us I figure its worth the shot.

Another advantage to this head is the Honda manifold is bolt on (yet to be confirmed).

Braineack

iTrader: (62)

put your pics on a real server so we can see them.

Madjak

Fixed... though the photo is pretty average.

Der_Idiot

iTrader: (2)

That looks like it'll fit in there quite well actually, wonder how well that manifold flows?

Madjak

There are some dyno charts around showing a 5-10 hp improvement above 5000 rpm over a skunk2 Pro manifold. Thats on a Honda engine which responds well to better flowing intakes. I doubt it would be representative for our engines.

My choice for this manifold was 90% because of fitment with the required runner length and better flow. Plus I found one second hand with a throttle body.

Midtenn

iTrader: (15)

Just my opinion, but you're going to loose a lot of support from the top 3 holes even with an oversized washer. If you are already going to be welding on a tab for the rear most hole, I would also add some material around those holes so you have completely inclosed hole to support the weight of the manifold bouncing up and down.

OGRacing

iTrader: (1)

not 10 hp on a stock motor. right?

Madjak

The Honda intake finally rocked up and I also purchased a spare inlet gasket to check alignment. It all matches up pretty much exactly as per my mockup so it should be fairly easy to fit. I'm a little worried about the drilling of the top holes holes taking out too much metal and weakening the flange. I figure I could either use big washers or weld it up, but I'd rather not do as it may warp the flange.

The port sizing is a little larger than the gasket so I'll need to trim it down a bit. Later in the year I'll spend some time to port the head to match but for now I'll just bolt it up and run it for the rest of the season with mismatched ports.

B18_Skunk2_zpsdqmuw4zu.jpg?t=1429759449B18_Skunk2_b_zps7djs4d7j.jpg?t=1429759339

The throttle body is also pretty tidy. This is the Skunk2 alpha cast body so it's the cheaper version of the billeted one. Still the throttle moves pretty nicely. I'm going to have to find a honda plug for the TPS and the other plug I think is the IAC. I'll have to find out some more info on it.

Chooofoojoo

iTrader: (7)

Bought mine off a member here started to be port matched, and I did some additional work on it to clean it up. Bolted up to my bp4w head like a champ.

Now Lazarus has it for actual testing

Madjak

No not stock... it was a built B18 going from 220 HP to 230HP or something like that... The gains were across the board but that doesn't mean that much when comparing to a different engine. It does mean that this manifold flows better than a OEM Honda manifold which already flows better than ours.

anyway I will know soon enough when I dyno it!

NiklasFalk

iTrader: (1)

Just one thought around "port matching" (which have been bugging me for a number of years) but it might be less relevant to boost (if you only care about max whp at wot).
Stock manifold and head ports are smaller than the OEM gasket by a fair amount, but are not that far away from being a straight runner without a step (i.e. the gasket creates a small gap but not a step).
Port matching to the OEM gasket is then IMHO a way to create a "chamber" in the runner (smaller area before and smaller area after) which will have an unknown (to me at least) effect (the air speed will be slower there at least). Some would make a shorter chamber and others a longer, but it's still an increased area in the runner (not continuously tapered at least).

Depending what you want to do with your head one choice could be to gradually make the runner narrower to fit the desired shape of the port in the head (ignoring whatever shape the gasket has).

Old school port matching is done by making a template (cardboard/paper) of one side and transfer that to the other. Using an oversize gasket as a template sounds plain dumb (foolish shortcut) IMO.

If your desired port shape happens to match the gasket, then that's fine. But don't think that the gasket shape dictates anything regarding port/runner design.

I know mine are matched with the loose intake in place (i.e. runner to runner regardless of gasket). But it's a lot easier when the intake is short and you can work trough it.

Madjak

From memory my head porting already matches the oem gasket. I'll take off the inlet manifold next week and take some photos. This skunk2 manifold has slightly larger runners than the oem gasket by around 1mm so I don't think there is a lot of matching required. The bigger issue is the Honda injector ports. I have to choose to keep the mazda ports and filling them in or using the Honda ports and filling and matching the head to the manifold.

bigben

Keep the mazda ports. Injector orientation is really important relatively to your head design. I would not mess with using the honda stuff.
Nice project by the way!

Ben

Leafy

iTrader: (1)

That other connector on the throttle body of the honda is the map sensor IIRC. The IAC for the hondas is on the side of the plenum.

Madjak

Yup your right... It's a denso 1 bar map sensor. I'll just block this off or leave it unplugged.



Edit: The runners are sitting out by about 20mm in this photo. I need to trim the front bit off for it to sit properly.

Fits in well. Unfortunately the faces of the ports on the head angle downwards about 4 degrees so the runners end up sitting fairly flat. I was hoping they would angle up more and sit a little higher. The Skunk2 Pro manifold would fit better for you LHD guys but unfortunately the brake master gets in the way for me.

I'm going to have to trim that front triangular support from the chassis rail to the strut top. Other than that it just requires a little drilling and cutting.

Oh and my head matches the gasket pretty much 100% so I can use that as my guide. It does slope down a little so the runner angle isn't ideal. I might sit the runners a little higher and grind the base to get a bit of turn down before the head so that the angles match. It doesn't need a lot. I might need to build up the top of the port more than I was planning where the Honda injectors sit.

Madjak

After some more thinking on how to fit the manifold I need to decide whether to cut and weld the flange or start modifying the existing Honda Flange. Fitment will be fine, it's going to miss all the things I was concerned about... So it's just down to the flange now and making that work.

How are the cut and welded and reinforced flanges holding up? I know the first ones made were cracking but is it still an issue with lots of reinforcing and a good weld? This would be an easy option for me, CNC a flange and weld it on, but I'm concerned about longevity which is why I want to keep the manifold in one piece.

If I use the Honda flange, it will need to be cut halfway through the existing injector ports and then filled and patched with weld to seal against the head. The Mazda injectors run right thought the middle of it all so my original plan of just plugging the injector ports won't work. I was hoping to mount it all up with only minor welding so that the flange didn't need machining but I doubt I can do that with the welding require to fill the injector ports.

I might try modding the Honda flange first, and if I start having big issues or it's taking too much time I can chop it off and weld on a new one.

Madjak

Update: Ok so fitment without welding didn't work out. The injector port locations on the Honda flange need to be welded and then cut in half to clear the Mazda injectors. Also the angle the manifold sits off the head wasn't exactly ideal with the plenum very close to the chassis with some of the vacuum ports hitting. The TPS also hits on the chassis so the throttle body would need to be turned 90 degrees which would require an adapter as the bold spacings aren't equal.

Instead I've decided to cut off the flange and weld on a new one. Simpler and easier to get the required alignment.



I ran the manifold through my table saw to cut off the flange at an angle for the runners. Also I drew up the flange in CAD and had it waterjet cut out of 12mm ally. Once welded, I'll reface this down to around 10mm. Also made up 6 triangular braces for strengthening.





Above photos show it's fitment in the engine bay. There is a good inch clearance around the brake lines and biasing valve. This isn't much of an issue for your LHD cars, but for the RHD models fitting the Skunk2/Blox pro manifolds won't work without moving the brake lines and biasing valve. I'm still sorting out placement of the fuel lines which are a bit awkward with the stock fuel rail, probably easier with an aftermarket rail.

The throttle body angles off at a great angle, missing all the pop-up light mechanism. I'm planning on building an air ram and filter box in the space left from running the Honda half width radiator. It will see half the front mouth's air pushed into a flat filter and up into the air intake. Nice cold air with a smidgen of added pressure.



Angle is pretty much ideal now for flow into the head. The 70mm throttle body looks serious with the added bonus of the Mazda throttle cable fitting straight in. The cable mount also happens to bolt on to the plenum with bracket that came with the manifold without any modifications... Couldn't have worked out any better.



Triangular bracing underneath. There has been no cleanup on the welds. I need to machine the welds flat around the mounting holes. I only put 6 braces on so you can't see them from above... it also means it's easier to access the two end nuts.



I have to finish off fitment, fuel lines etc and it will be off to dyno next week. I'll be also tuning for E85 as well so I should get some solid numbers on the improvement over stock manifold as well as running E85. Will be interesting to see some real figures.

Overall I'm very happy with the fitment. It looks like it belongs on the motor and hopefully will see some decent gains for the effort.

Alternative

Looks great! Keep up the good work! 🍺🍺🍻