Honda Intake Manifold

[plohl]

The maginitude of negative pressure wave is proportional to plenum volume. Hence large volume means a 'stronger' pulse. For restricted NA engines it's not uncommon to see plenum volumes 6 times the engines capacity.

Sent from my SM-N9005 using Tapatalk

[madjak]

Pezchops, thanks for all the advice. I was planning on using the mazda intake manifold gasket for initial alignment where I can sight the best alignment to the head ports. That will give me good centers for the holes I need to drill. Is there any issue replacing the existing studs with high tensile cap head bolts? The bottom holes are going to be very tight on the base of the runners, so much so I doubt I'd have much clearance for a nut.

I also like and will use the 'D' spacer idea. If I start welding the flange it will warp and will cause issues so keeping everything to just machining and bolting will be better. In that respect I might just machine some plugs to fill the injector ports. and locktite them in.

Plohl, the only way to get a 10 liter plenum would be to extend the front to the throttle body, but I doubt this would have the desired effect.

Here are photos of my clearance check. This print was scaled off a single dimension which was the runner spacings... I think it's within around 10mm or so.






Hard to see with the photo, but the back end should clear the clutch and brake master. The proportioning valve will have to move, though it would probably squeeze in there it would be too hard to adjust. My fuel and oil pressure regulators will have to shift a bit too.

Overall the placement is great, with the throttle body angled at the correct angle to avoid the pop up lights and the top of the plenum should clear the triangle bracing to the strut tops. This might not be as hard as I was thinking. By the looks of it, it will almost just bolt straight on, no welding required.

[NitroDann]

Thats pretty good news, whats it worth posted?

Cap heads are fine, be pedantic about the correct length and locktite them with nutlock.

Dann

[madjak]

I have sourced one second hand with a Skunk2 alpha 70mm throttle body for around $350... You can get them on ebay for about the same new just without the throttle body.

There is also the Skunk2 Ultra Race which has shorter runners. These suit the higher power turbo Hondas but they are operating in a higher rev range. Fitment would be the same as the flange is identical, just with lots more room around the plenum so you could run a larger volume. Someone needs to try one on a high powered turbo car... Dann?

The cheaper option is the Skunk2 Pro / Blox manifolds which can be found for $150 but these all require the flange to be cut off and the mazda flange welded on. The guys running these are seeing them crack with time even with lots of additional bracing. Add the cost of the welding I think the Ultras are a better option given they are almost bolt on with a little drilling (*yet to be confirmed)

[madjak]

Cap heads are fine, be pedantic about the correct length and locktite them with nutlock.

M8 x 1.2 pitch and 28mm is the length required... though mine might need to be different due to flange thickness so I'll probably get longer ones and grind them shorter to suit. I've seen cap bolts drilled and wired before on race engines so I figure they have a tendancy to work their way out.

[NitroDann]

8x1.25

[madjak]

Posted this up on Miataturbo also...

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. 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.

[NitroDann]

Amazing,

Do you have a list of the total parts used? (With part numbers?)

[Magpie]

Nice work, what are the runner lengths?

[Jeo]

So I'm not at all contributing here but that just looks plain old right. Well done!

[madjak]

I don't really have parts numbers... but here is a list of items and their costs:

Skunk2 Ultra Street intake manifold (B18)
Skunk2 alpha 70mm throttle body (included tps, map sensor and AIT sensor)
Purchased both second hand for $300 + shipping

12mm Flange waterjet cut - $80
6 x triangular braces - home made from scrap
Welding - mates rates - $120
Resurfacing of Flange - home done on a mill (probably $100 at a shop)

So total cost to me so far is $550ish for a intake and throttle body. There is some manual labour but so far it's been pretty easy. Cutting off the flanges requires some tools but could be done with a hacksaw or cuttoff disc if your keen. I used an electric drill and a porting bit to clean up the inside of the runners.

Pigtail connectors for the tps, ait are still yet to be sourced... wrecker wants $100 for both but I can find them online for $12 each (I need them now though)

As part of this and after NitroDann's E85 post, I've put in a flex sensor ($80) and braided fuel lines / filter. My long term goal is to put a Rotrex on this with a target of around 350hp.

Magpie, runner length is around 210mm from memory... It's pretty much ideal for my rev range of around 6000-8000. Dyno will tell if I'm right!

[Apu]

Hmmm, B18 you say...

Dann...suggestions?

[Magpie]

Thanks. Will be interesting to see your results.

Agree with the previous posts, it looks like it belongs, good work.

[madjak]

Hmmm, B18 you say...

Dann...suggestions?

I wanted to put a K20 engine in but is was going to cost too much, this is the next best. I now have a Honda intake, throttle body, sensors and a Honda radiator... what next?

I actually think these could be investment cast very easily... well at least the runner section. When I get time, I want to 3D print an intake and then use investment casting to make an ally one.

[slug_dub]

Bad time with fitment avoided! Great work.