Honda Intake Manifold

[madjak]

Fitment might be tough. The skunk2 ultra street I'm thinking of using leans forwards and has a tapered plenum. I've mocked it up in photoshop and checked dimensions and its very tight but I think it will fit. Only real way to know is to try it as I can't find any info of this manifold or the skunk2/ blox manifold on a rhd car.

Will have to move the prop valve I think. Looking at the flange design I think it will mount up to the head with just some slotted holes.

[speed]

I'm all for it. I just didn't have anything technical to add so I was keeping quite. You should now feel encouraged!
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[Ice88]

If your running the engine at high rpms then using the Honda location may prove worth while.

Really depends on how optimum the injection point on the B6 was to start with.

+1 on giving it a go. I had something similar planned but not a B engine

[madjak]

Looking at the manifold I think I can fit it directly to the head without cutting off the flange. My original plan was to make a transfer plate that went between the head and the manifold. This would have allowed room for the Honda injector path to merge into the oval intake on the head.

Now that I'm planning on a direct fit as I think there is room for the stock stud locations. If I run the Honda injectors I'd have to modify the head to make them fit. So Mazda injectors it is.

[project.r.racing]

I incorrectly assumed that your engine was close to standard.

Carry on

Agreed. Simple info that could be placed in the first opening post. And does change views/opinions.

[madjak]

I incorrectly assumed that your engine was close to standard.

Carry on

Agreed. Simple info that could be placed in the first opening post. And does change views/opinions.

Yeah probably would have been useful! I tend to get focused on a specific idea and forget that no-one else knows about my build.

Dann, How much does increasing the intake plenum flow help with turbo / supercharger efficiencies and end power. My understanding is limited, but the guys chasing high power builds tend to focus on the plenum volume and flow. Have you ever upgraded the intakes on the cars you've built for big power?

[madjak]

Below is the intake I'm looking at getting. It's a two part manifold where the plenum unbolts. This is handy because you can port the runners easily and add spacers to the plenum for more volume but I doubt more spaces will fit. From my rough measurements, the brake proportioning valve will hit so it will need to be moved, but the tapered plenum helps it fit past the brake master and the angled chassis rail supports. The throttle body also is angled back in the right direction which will help to get the intake plumbing past the light mechanism on my NA.



Here is my mockup of the hole placements.



You can see the flange has machined flats where the mounting holes will need to go. This means I can weld or just slot the existing holes to fit with the Mazda studs. Most of the holes are within 10mm of the required position which is handy.



I can probably just JBweld the Honda injector ports and blend them in. Alternatively I could get them welded up and grind them smooth.

I'm at the point where I just need to order one now and then see how it fits. Hopefully it will.

[NitroDann]

Never. Broken gearboxes are your nemesis far before chasing 10 more HP with this much effort is worth it

[tbro]

1/You can see the flange has machined flats where the mounting holes will need to go. This means I can weld or just slot the existing holes to fit with the Mazda studs. Most of the holes are within 10mm of the required position which is handy.
2/I can probably just JBweld the Honda injector ports and blend them in. Alternatively I could get them welded up and grind them smooth.

1/ Slot the holes with a mill, by the time you weld up the old holes you'll need to machine the mounting face.
2/ Why not fit welch plugs while your working out what works and fits, then if all goes pear shaped you can still sell it on to a Honda player, same with not welding up stud holes but slotting them.

""I'm surprised there is no encouragement on this forum for anything different. It seems everyone wants to build the same thing all the time""

You asked the question earlier why no one discusses these type of mods, simple, for 99.99% of peps here if you can't buy it or it doesn't have "that fancy name on it " then they don't want to try anything new.
A few years ago I tried to discuss adjustable sway bar mounts for the MX5, guess what, according to the experts waste of time yadda yadda yadda,because no-one had done them before they wouldn't work or so the experts reckon. These are now sold and produced in the US.

Thus I now keep my ideas for fellow builders and racers and leave the rest for parts fitters or copiers.

Might even offer my rad/oil cooler/intake idea, might not either

Terry

[project.r.racing]

It's a two part manifold where the plenum unbolts. This is handy because you can port the runners easily and add spacers to the plenum for more volume but I doubt more spaces will fit.

Explain adding volume to the plenum doing something?

Yeah you can add volume to if. But the runners dont increase in size, so you still have the same amount of air going through the runners. For a n/a engine, maybe having larger volume is good for engine response, but on a forced engine, limited change.

[madjak]

1/ Slot the holes with a mill, by the time you weld up the old holes you'll need to machine the mounting face.
2/ Why not fit welch plugs while your working out what works and fits, then if all goes pear shaped you can still sell it on to a Honda player, same with not welding up stud holes but slotting them.

Yeah I might need to increase the size of the flat areas which I can do via a mill. The flats will need to be machined from the side because the runners and plenum base will get in the way.

Once I have the manifold I'll figure out if it will fit prior to hacking it up. I really think I should be able to slot the holes to make it work. The only odd one is the top left which I'm not even sure I need to fix. The flange looks pretty thick on these manifolds.

I also thought I could taper the flange 5-10 degrees to lift the plenum a little if I have to clear obstacles. Not sure on bonnet clearance though.

Might even offer my rad/oil cooler/intake idea, might not either

I'm always interested to hear ideas. My radiator is a half width Honda radiator, with custom support brackets. I'm planning on boxing in the other half to directly feed air into the intake. I figure I should get this done first.

So far all my experiments have worked... we'll see if this intake does too.

[madjak]

It's a two part manifold where the plenum unbolts. This is handy because you can port the runners easily and add spacers to the plenum for more volume but I doubt more spaces will fit.

Explain adding volume to the plenum doing something?

Yeah you can add volume to if. But the runners dont increase in size, so you still have the same amount of air going through the runners. For a n/a engine, maybe having larger volume is good for engine response, but on a forced engine, limited change.

That one I'm not sure I can explain! People talk about ideal plenum volumes being 1.5 times the cc of the engine as being ideal. Too small and I suppose there isn't enough of a buffer of air to smooth out the intake pulses. Too big and you get more throttle lag. I haven't read up on it, I just know that changing it can alter the power curve a little.

Designers of these manifolds must start off with some set targets. Runner length, plenum volume but in the end it comes down to trial and error to see what works. The unboltable plenum is good for that as you can trial a spacer quickly and see what you gain or lose. I guess for people chasing that last 2-3 hp it might be handy. In this case I'm not sure it will help because I doubt there is much room to fit anything that will make a difference.

edit: probably very handy for cleaning out the manifold though. My current one is disgusting.

[pezchops]

1/ Slot the holes with a mill, by the time you weld up the old holes you'll need to machine the mounting face.
2/ Why not fit welch plugs while your working out what works and fits, then if all goes pear shaped you can still sell it on to a Honda player, same with not welding up stud holes but slotting them.

Yeah I might need to increase the size of the flat areas which I can do via a mill. The flats will need to be machined from the side because the runners and plenum base will get in the way.

Once I have the manifold I'll figure out if it will fit prior to hacking it up. I really think I should be able to slot the holes to make it work. The only odd one is the top left which I'm not even sure I need to fix. The flange looks pretty thick on these manifolds.

I also thought I could taper the flange 5-10 degrees to lift the plenum a little if I have to clear obstacles. Not sure on bonnet clearance though.

Might even offer my rad/oil cooler/intake idea, might not either

I'm always interested to hear ideas. My radiator is a half width Honda radiator, with custom support brackets. I'm planning on boxing in the other half to directly feed air into the intake. I figure I should get this done first.

So far all my experiments have worked... we'll see if this intake does too.

if you can get accurate dimensions of the MAZDA sets of holes you can have your machinist datum from an existing hole on the honda set to machine your MAZDA set of holes.
you will need to know an off-set amount from the honda hole you datum from to the close MAZDA hole
i would get them to use a slot drill and plunge through the flange rather than slotting the old hole.
you are just removing metal you dont need to.
also plunging the holes to the stud size, the flange will self align when you bolt it on the head...with slots it will move all over the place.
like TBRO said ,you can have bungs made for the injector holes if you cant find welsh plugs the right size.

i dont think you need to weld a piece on for the MAZDA stud that is off the honda flange profile.
it looks like the mazda stud will be free standing away from the flange.
if not the slot drill pluging at that coordinate will skim the edge for you.
use like a D shaped spacer with the stud size hole through it and have it just a little lower than the thickness of the flange.
then the washer and nut will still work to tighten down the flange.the flat of the D spacer sits against the flange.

[speed]

1/You can see the flange has machined flats where the mounting holes will need to go. This means I can weld or just slot the existing holes to fit with the Mazda studs. Most of the holes are within 10mm of the required position which is handy.
2/I can probably just JBweld the Honda injector ports and blend them in. Alternatively I could get them welded up and grind them smooth.

1/ Slot the holes with a mill, by the time you weld up the old holes you'll need to machine the mounting face.
2/ Why not fit welch plugs while your working out what works and fits, then if all goes pear shaped you can still sell it on to a Honda player, same with not welding up stud holes but slotting them.

""I'm surprised there is no encouragement on this forum for anything different. It seems everyone wants to build the same thing all the time""

You asked the question earlier why no one discusses these type of mods, simple, for 99.99% of peps here if you can't buy it or it doesn't have "that fancy name on it " then they don't want to try anything new.
A few years ago I tried to discuss adjustable sway bar mounts for the MX5, guess what, according to the experts waste of time yadda yadda yadda,because no-one had done them before they wouldn't work or so the experts reckon. These are now sold and produced in the US.

Thus I now keep my ideas for fellow builders and racers and leave the rest for parts fitters or copiers.

Might even offer my rad/oil cooler/intake idea, might not either

Terry

Terry, I understand where you are coming from. Is a shame that new ideas are often put down.

Is always easier to criticise someone's work then it is to create it from scratch.

I say bring on new ideas and share them with pride


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[Magpie]

That one I'm not sure I can explain! People talk about ideal plenum volumes being 1.5 times the cc of the engine as being ideal. Too small and I suppose there isn't enough of a buffer of air to smooth out the intake pulses. Too big and you get more throttle lag.

Designers of these manifolds must start off with some set targets. Runner length, plenum volume but in the end it comes down to trial and error to see what works.

Hopefully I can provide some real data for you to ponder with respect to using a sausage filter and a custom air box for ITB's. Seat of the pants suggests that there is more torque down lower than previous, however low rev range driving is not something that I have done before. The seat of the pants could just have been I'm happy to have it back and it feels good....

Whilst there has been some trial and error, 40/90/current trumpet lengths most of the work has been done mathematically and with expert opinions. Who is to say the experts are right but, current interim data does support the experts and the mathematics. Like you say Madjack you have to start somewhere and theory is as good as any.

As a caveat what works for my build may not work for others so take it with a grain of salt, however a lot of time has gone into backing up the theory with evidence.

Madjack go for it, use the forum as a test bed for your ideas, some will support others will disagree. I would only listen to those who disagree and support their argument. A statement not support by fact is just a personal unsupported opinion and needs to be treated as such.

What has changed, facts:
1. Runner length has increased.
2. Filter surface area has decreased (Pipercross sausage filter to flat K&N Filter). Will calculate when have the car back. However can't measure the restriction of each because the pipercross cannot be retrofitted.
3. Air no longer sourced from the engine bay
4. Now have some plenum volume due to a sealed airbox as opposed to being open to the engine bay air movements. Will calculate volume when I have the car back.