Honda Intake - No welding req
 

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.

https://www.miataturbo.net/attachmen...ine=1428644898

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.

https://lastpixel.app.box.com/repres...tu0iik2m4ydlko

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.

http://www.all4honda.com/images/stor...05-0500_02.jpg

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.

https://lastpixel.app.box.com/repres...h4vp95y53h4l72

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.

Being an Ass;
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.

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).

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

Fixed... though the photo is pretty average.

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

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.

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.

not 10 hp on a stock motor. right?

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.

Attachment 184156Attachment 184157

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.

Attachment 184158

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 :party:

https://dl.dropboxusercontent.com/u/...403_074953.jpg

https://dl.dropboxusercontent.com/u/...403_081155.jpg

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!

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.

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.

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

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.

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

https://www.miataturbo.net/attachmen...ine=1429950077

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.

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.

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.

https://www.miataturbo.net/attachmen...ine=1432094404

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.

http://i292.photobucket.com/albums/m...psihvta5sl.jpg

https://www.miataturbo.net/attachmen...ine=1432094404

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.

https://www.miataturbo.net/attachmen...ine=1432094404

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.

https://www.miataturbo.net/attachmen...ine=1432094404

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.

http://i292.photobucket.com/albums/m...psimy3ezwx.jpg

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.

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

looks awesome!

Great looking project! I hope the dyno results match or exceed your expectations.

A few questions...
1. What alloy did you use for the new flange?
2. Can you share details of the weld process which you used?

I assume TIG welded...?
Any special prep or post treatment (ex: heating components before welding)?
What welding machine did you use and what were the (approximate) settings (ex: amps, volts)?

3. Would you be able/willing to share the CAD file for the flange?

Please let us know how the dyno sessions go!

Thanks

1. 12mm 'medium' grade ally... Not sure on the specs but I told the guy I needed for a intake flange and had to be welded.

2. I didn't weld it, I had a friend weld it. I know he used a TIG and had to put the flange and manifold in an oven due to the thickness. Other than that I think good welding is more art / magic than settings. I'm thinking of taking a welding class as it would be nice to be able to do this sort of stuff myself.

3. Sure, CAD file is here: https://lastpixel.box.com/s/vwdgkpy6...hd984iew4my92a
One thing to note, this is for a BP engine, also when it was welded the flange shrunk a little lengthways. This just meant I had to file the holes a little. Also the ports on this CAD file are to suit by head which is ported to match the gasket. The version "NA8_Intlet_Flange_For_Honda.DWG" is slightly modified so that the widths of the end ports are reduced 3mm so that they can be ground on an angle once the runners are welded on.

Dyno is tomorrow or Wednesday. I'll report back when it's done.

here are a few pics of it all mounted up and ready to go. I still need to tidy up the wiring, it's just temporary to get me through to the dyno.
https://www.miataturbo.net/attachmen...ine=1432518679

https://www.miataturbo.net/attachmen...ine=1432518679

Honda Intake - No welding req
 

How's that half rad working out?

Works fine for me, but I may have been lucky. I only did it cause the radiator was cheap and I hadn't read up on cooling on the forums. I figured if my car was cool with the thin stock NA6 one then a thicker smaller one would be fine. There's been a bit of discussion about it in the cooling thread but generally I wouldn't put one in a street car. My car happens to be balanced, but this may have been a fluke between radiator sizing, engine heat output and coolant flow.

• My car is used for sprints and track work only.
• Engine has a simple coolant re-route, no heater, no thermostat, oil cooler.
• Radiator is a Honda ASI radiator which seems to work very efficiently.
• The radiator is ducted in on the LHS, RHS is where I'll built an airbox but at the moment it's a void.

Tracking my car on hot days (35 deg C) I see a max of around 92 deg C in the logs. That with 4 very fast WOT laps, but looking at the graph it would sit there forever.

Dyno results are in...

https://www.miataturbo.net/attachmen...ine=1432720221

Solid Line is E85
Dashed Line is 98 octane (95 Ron?)
Red overlay is the stock manifold (*Estimated from previous dyno - Dec 2014)

The engine really needed to run to 8500 rpm to get max power, it was still ramping up above 8000... reving to 8200 on the dyno was high enough for me.

My old IM (red line) made pretty much 180HP @7800 with a dead linear power curve. It tailed off above 7800 and had nice rounded top. Torque curve was very flat but trailed off at the upper revs.

New Honda manifold combined with very large cams causes a lot of manifold pressure fluctuations throughout the curve. This made tuning very difficult and you can see the lumps still final dyno graph. The Honda manifold looks really good from the 6250 through to 8200 where it has really flattened off the power graph. At 6750 I think I'm making over 40HP more than stock manifold (50HP on e85). The highest we saw on the various runs was around 215HP on e85.

All up this is much better than I had expected. Given I'm reving between 6000-8000 in most events this should give me a lot more power than previous.

Next event is this weekend so I'll report back once I've actually driven the car.

I have a video of the car on youtube... can someone embed this into this thread? I can't seem to get the linking working

edit: oh that wasn't that hard!

<p>a turbo would smooth out the TQ nicely.</p>

Yeah it probably would but I don't like turbos...

I run in an under 2000cc production sports class against Honda, lotus, toyota 86 GT etc. Put a turbo or sc on and I'm in a Group A class against exotics... like a supercharged lotus @600+ HP and very lightened race cars. This car is quicker than most turbo mx5s on the courses I run. On the track drivability trumps power.

Thanks for the info on how the manifold was put together.

Nice looking engine bay :-)

One thing to note is that while the throttle cable bolts on perfectly and fits into the Honda throttle body, the throttle wheel is a smaller diameter than the Mazda one. Enough that accelerator movement is reduced to 2/3rds. This combined with the larger diameter throttle body will make the throttle a lot more sensitive. I haven't driven the car yet but I suspect it will have some impact on throttle control.

There may be larger ones I could source from a different throttle body, however for now I'm just going to machine up my own.

Here is a video of the car running on a hill climb. Excuse the bad start and dodgy shifting but it was only the second run after changing to the Miata Roadster short shifter and 5th wasn't in the same spot as usual. My final run was a bit over 1 second quicker but the batteries died on the gopro.

Albany Windfarm 2015: https://youtu.be/4BCfCiIE3HU

Wow! Awesome results!

Guessing it shouldn't be hard to maybe retrofit a Skunk2 Miata throttle cam onto this piece to fix the pedal travel issue?

I was just going to make a billet one up on the lathe. I'm enjoying making things in the workshop.

After driving the car I don't think I noticed any difference in throttle control. I suppose you can adjust to 25% less pedal movement easily enough, although if you watch the vids you can see I'm over reving when heel and toeing under brakes. It wouldn't take long to get used to it though.

Do you happen to recall what fuel you were using for the red line?

98 octane... only changes between the dashed line and red line was the intake, switch to 1000cc injectors and new fuel lines. Everything else was the same including tuner and dyno.

propped! thanks!

Double post

huh? I only posted once to ask, and another time to say thanks and give props where they are due.

Sorry mate, mine was the double post. Typed out the reply on my mobile and I must have submitted it twice.

Cheers for the props. Hopefully someone will try this same intake on a more stock motor so we can see how well it performs.

Hi there. :)

Not timely, but i'll have it done by the end of the year on an unopened BP4W.

Hi Rick.
My compliments on your Build.
Rick I am interested to know if you still have the Skunk 2 Ultra Street Flange that you cut of for your Miata.
I have a project going and could make good use of the removed Flange for my B16B Type R Honda Motor.
Please PM me if you are interested and able to supply for suitable agreed reward.
Cheers Rick
From hotbricks (Shane)

Sorry, the flange was cut into pieces as I had to hacksaw off the flange prior to the finishing cutting on the table saw. I needed to test fit to set the angle.

I've seen a CAD version of the B-series flanges somewhere. You should be able to download it easy enough and then get it waterjet / CNC cut.

holy crap nice build. great results.

Just a bump back from the past... I pulled this manifold off the engine last week and inspected all the welds. No cracks to be seen which is awesome considering the vibrations that go through my engine. It looks like this style of bracing works very well if anyone is modifying a Honda manifold in the future. BTW I still think the straight runner design is 10x better than the curved miata skunk2 intake. So it's still a worthwhile mod for anyone with a very heavily worked engine. Also there is a center feed Skunk2 available now... That would be interesting on a highly boosted engine.

Last rebuild this engine hit over 220whp @ 8,800 rpm. The main mods since this thread was the mechanical water pump switched to EWP, reworked head with new valves (RB26 supertech), more revs, and a dogbox with straight cut gears.

100 percent true about runner shape IMO too. Curved manifold works great on engines where you have very nice "straight shot" to the valve from the top. After porting out my head I ended up with almost straight portion inside the head (I believe it is about 22deg on roof, measured from flange face) and manifold angle is about the same. With for me optimal runner lenght of 350mm velocity stacks end up just before shock tower. Oh and I can agree on that bracing too. I saw many custom manifolds, friend of mine Peugeot 306 with 270hp, 750Hp golf 2 (karl schagerl) with tripple fuel rail and longest runner lenght I ever seen on Turbo car except peugeot 405 T16 PP car. Both of those cars have straight manifold and both have this kind of bracing. I will add triangle brace on the runner from top - something like simpson uses on their Exhaust manifolds.
https://cimg9.ibsrv.net/gimg/www.mia...c7c09126bf.jpg

After four years of running this manifold I figured whilst I had it off my car I may as well smooth out the casting marks and bell mouths. I'm modifying the throttle bracket to make a throttle blipper for my sequential.

https://cimg0.ibsrv.net/gimg/www.mia...751387680b.jpg

What is the length of the manifold, from flange of the last runner to end(top) of plenum.. close to the brake master?