Mugen airbox - car now 'bogs' down in low rpm?

[Alvis]

Hi guys,

I recently bought and installed a Mugen airbox on my D16Y4 and it now 'bogs' down in the low rpm (ie below 3k). Does this mean the car is running to lean?

You can hear the induction sucking but not a lot of action... Would an upgraded fuel rail help in getting a more richer air/fuel ratio?

(I have NGK Iridium sprakies in the car and new Top Gun ignition leads)

My upgrade thread with pics of install: http://www.ozhonda.com/forum/showthread.php?120635-JDM-Mugen-inspired-EK-sedan...-in-progress-pics/page5

[Tai]

Did you reset ECU?

Did you install the intake after or before the leads+plugs?

Intake kit might be too big for your D series engine.

[Alvis]

Yeh, I rang Honda on how to reset the ECU (some say fuses, some say battery) and they told me to disconnect negative battery terminal, let it sit for 30 minutes, start it up for 15 minutes (no acceleration), turn off and turn back on. So that's what I did...

And leads and plugs installed before intake...

[Tai]

I Reckon the intake kit you have is too big for your engine.


Basically if you use your mouth as an example lol, you can easily suck air from a straw without problems, then suddenly you are sucking air from a Massive pipe or a didgeridoo it will take a lot more force at the beginning to get the air moving.

So in your case you suddenly have a more bigger intake on a car which it isnt tuned to nor is it required for such a small engine.

[Alvis]

yep, I'd say that's true because the airbox is designed for a B series Type R engine...

Any suggestions on what might improve the response? Does this mean it's running too lean air/fuel ratio?

[EK1 Civic]

I Reckon the intake kit you have is too big for your engine.


Basically if you use your mouth as an example lol, you can easily suck air from a straw without problems, then suddenly you are sucking air from a Massive pipe or a didgeridoo it will take a lot more force at the beginning to get the air moving.

So in your case you suddenly have a more bigger intake on a car which it isnt tuned to nor is it required for such a small engine.

I was planning to put a dc2 airbox in my d16 so i had a pod enclosure. Would i suffer the same case? Otherwise i was just gonna stick to a high flow panel filter and cai feed.

[Tai]

Basically if you keep it without the similar piping diameter size it should be fine.

so if you use the straw analogy again, If you were to make it all curly and heaps long you can still suck from it easily as the straw size is still the same size.

I got a Spoon CF intake Arm mated to the stock rubber arm, KnN panel filter, and the Piping to the airbox underneath is still similar size as OEM.

Overall the piping size is very similar to OEM but just without the resonators to restrict "direct" airflow.

I'm not sure abotu DC2R airbox but a few ppl have done it without complaints.

Mugen Airbox has a Massive CAi feed and the pod is quite larder than oem panel filter.

[Alvis]

Sounds like a good setup Tai, they are cool little intake arms those Spoon ones and hard to come by too :)

To help me understand, and ignore my ignorance lol, I have a question using the straw analagy: regardless of pod/filter size shouldn't the same amount of air be flowing through the intake arm, that is, the intake arm only has the capacity to take in so much air?

Or are we saying with the stock airbox it wasn't flowing at 100% capacity, hence the 'bog' down I'm experiencing at low rpm?

[EK1 Civic]

Im not sure if the dc2 airbox is straight fit to the intake arm. But if its able to mount onto the stock ek intake arm, i don't see any issues arising because its limited to the pipe size diameter. Need to ask around with people who have done dc2 airbox swaps into an ek for more insight. Don't wanna do something thats just gonna lower the power output, wtfs point of that =/

[Alvis]

IMO I'd say it'd say it might lower the torque low down more (like mine) rather than the power through the mid-high range

[Tai]

Ok the OEM setup is basically pretty much Direct suction if that makes any sense.

The Mugen one is a pod filter sitting in a larger airbox with empty space.

Basically the OEM doesnt have gap or larger empty space addded in the air intake setup causing a drop or extra suction required to get the vacuum action happening.

The Mugen one is suspending in empty space in the airbox so it requires more force to get the vacuum action starting hence the bog or lag.

But overall your engine wouldn't benfit as much as the B series engine which need more Air since it makes more power comapred to the D.

I hope that makes sense hahaha.

[EK1 Civic]

Ill do a quick search and if not ill start a thread, to see if anyone with a d engine has done this and seen any gains or no gains xD

[EKVTIR-T]

As above variations on the intake can genuinely give noticeable results under foot.

I get a similar result as yourself when I use my k&n panel instead of oem.It produces a flat spot in the lower rpms so I much prefer the response using the oem panel

Just feels like more torque all through the rev range

If the motor was modifed and needing more air then its a different story

[TheSaint]

i had the same thing with the simota big tube intake on my D15b7 ... has amazing induction roar and a bit more torque but it bogged a bit below 2000 rpm

now i have a Fujita CAI (smaller diameter pipe with pod down in front of the wheel) and it doesnt sound as good in low rpm (almost stock) but it doesnt bog and sounds amazing in high revs

the Fujita kit for my D series has alot smaller diameter pipe than the one i installed on my B18c

[Tai]

The mugen airbox for your D series would most likely be felt in the top end area as thats where it requires much more air flow during high revs.

[Alvis]

Ok the OEM setup is basically pretty much Direct suction if that makes any sense.

The Mugen one is a pod filter sitting in a larger airbox with empty space.

Basically the OEM doesnt have gap or larger empty space addded in the air intake setup causing a drop or extra suction required to get the vacuum action happening.

The Mugen one is suspending in empty space in the airbox so it requires more force to get the vacuum action starting hence the bog or lag.

But overall your engine wouldn't benfit as much as the B series engine which need more Air since it makes more power comapred to the D.

I hope that makes sense hahaha.

Damn! You're good Tai! Definitely makes more sense to me now :D

And yeh, same Saint - really really sweet induction purr on the Mugen but you don't feel it until say after 4+k then it really starts moving (for a D series anyway lol)

Right, so is this just a trade off I have to live with for overall better drivability? And will any modification on the fuel side of things (fuel rail and injector size) give me a better response?

Or would a Haltech Interceptor ECU mod help more?

[Tai]

No point in tuning and changing parts to make it feel more responsive, will cost as much after all that as getting a B16a, which will easily make more power stock than a modded D16y

[Alvis]

Might sound silly to some but i didn't want to change the engine because I know the history of the car and it has so little kilometres on the clock... who knows what you get when you buy a second hand Type R engine could be a bucket full of worms and then i'd kick myself lol + if i changed engine wouldn't I need a new ECU anyway?

I was quoted on a Haltech unit providing an extra 10-15kw - but I'm not sure on this brand. I was also looking at Unichip?

[mugen_ctr]

better off getting more engine modifications done, than a tune up, if u do get a tune up, your just wasting money, and what would u tune anyways? A/F? you can already do that with alternatives which is cheaper.... 10-15kw is with the supporting mods, i highly doubt you would see such gains with very little mods, and with a d-series, not bagging them since i have one, but money for power, not worth it in the end.

[Tai]

You aint gonna squeeze out 15kws from a D series, you'd be lucky to get even 5kws lol.

TBH dont waste your time trying to add more power.

Save the $$ on suspension mods so the car is more enjoyable to control.

If you were to buy an engine conversion you would get a Halfcut with majority of parts needed including the ECU.

Just leave your engine as is.

[Alvis]

You guys obviously know more about modding engines than me, so I appreciate what you have to say... it's funny I was tossing up between ECU and suspension/front strut brace so looks like suspension is my best bet :)

Is there any point doing something small like changing the fuel side of things to enrich the A/F ratio given the increased airflow - was thinking a fuel rail?

[EKVTIR-T]

Please dont go and buy a Haltech for your stock D series,its really throwing money away...

You already spent more on the intake than the motor is worth and had unsatisfactory results.

Maybe a few suspension mods as they said but putting money into D series is pretty futile

[Alvis]

'unsatisfactory' bit harsh lol - Overall the drivability of the car is better with smoother power delivery in mid-high end range, sounds good and is legal in NSW; it's really only down low (below 2.5k) where it's not too crash hot. And if I sell it one day i'd pretty much get 70% of my money back - so in long run it doesn't sound that bad...cost of a normal intake really - but yes, ur right and point taken on modding D series - you don't get much bang for ur buck unfortunately :(

[mugen_ctr]

If u really wanted to tune ur air fuel mixture, id recommend getting something like Apexi SAFC or so, its not to overly pricey for what it is, and does the job, but i suspect its ur cars running fine, and not the actual tune of fuel mixture but rather as what others have said about aftermarket intake systems
Ecu is a good idea and performance mod, but for D-series, naar, lol, better off goin suspension work, an plus you enjoy it more in the long run.

only really good mod i can see for D-series, turbo charging it really, even a worked D-series with forged internals an ITB's, is still weak, come to think bout it, with that amount of money spent on worked D-series, probs coulda netted you a B-series swap with added mods, lol

[dougie_504]

It's a D-series bro, you're not supposed to feel anything below 3k revs anyway lol.

Stock box is best for low-down power, but aftermarket ones tend to be better for high-end power. If you want low-down you could try an K&N panel filter in your stock box.

[Alvis]

If u really wanted to tune ur air fuel mixture, id recommend getting something like Apexi SAFC or so, its not to overly pricey for what it is, and does the job, but i suspect its ur cars running fine, and not the actual tune of fuel mixture but rather as what others have said about aftermarket intake systems
Ecu is a good idea and performance mod, but for D-series, naar, lol, better off goin suspension work, an plus you enjoy it more in the long run.

yeh the engine is healthy and no problems with it, but like you say the overall opinion seems to be d series engine is 'not worth the money or effort' and suspension is probably the best thing for it. I'll just leave as is for time being and enjoy the new mid/top end power and induction growl :D


It's a D-series bro, you're not supposed to feel anything below 3k revs anyway lol.

And true dougie - guess there's not too much to start with below 3k anyway lol


Thanks for ALL your input guys, appreciate it :)