Improving the breathing on the K12 CR range of engines (Now Fitted)



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Re-tested with worst conditions, (9°C in front of 16 and lower humidity)
60-100 6s flat! Really nice gain, -1s gained!
i will test another time with similar conditions (16°C +-) and another comparison test with sprintfilter fitted.
(I have videos if you want i will post it out)
Nice to see that my 'seat of the pants' indication of a very noticeable improvement in acceleration, is born out with your test figures. The downside of this modification however is that on my 1.2 the engine it is still pulling like a train in second gear, with no tail off, when it hits the rev limit at 6.5K revs It really wants to go to 7K at least.........
Nice to see that my 'seat of the pants' indication of a very noticeable improvement in acceleration, is born out with your test figures. The downside of this modification however is that on my 1.2 the engine it is still pulling like a train in second gear, with no tail off, when it hits the rev limit at 6.5K revs It really wants to go to 7K at least.........
The downside of which mod? The seats removal or intake mod?
And in both cases why downside?
I'm sorry but i'm a english newbie and i don't understand some common saying..😅
By the way with these mods the car it's completely take corners in maravellous way without squeaking the tyres (remember -21kg of spare wheel+tools, -50backseats, originally was 1121 curb weight (without LPG system)..
Next step is flexi-board boot storage system and car parcel shelf removal (average 15kg) and putting a fitted carpet to create a smoother and plainer surface..
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'Seat of the pants' is a saying describing the instinctive feeling that you get through just driving the car about perceived changes in performance ;). Ok on the weight reduction, especially on a track day, it does make a big difference on BHP/Ton, but are you not likely to need to carry more than one passenger in the car?
Now i understand!! Thanks!
I’m 23 and I usually transport only one passenger at time (my girlfriend), if necessary i can reassemble in 10 minutes (4 17mm bolts)..
Since November 2017 i carried more than one passenger three or four times...
I’ve done a new mod in these days, an upgraded air feed for my little nissan note:

that’s the before without the grill removed
that’s the before with the grill removed, how you can see the air can pass through only by these little holes..

After porting the plastics ( you can see the scoop upon that two uprights)

made a air conveyor/duct

fixed and sprayed with a metal protector

an huge improvement for air conveying

and a air restrainer for our scoop
Because now, the air is forced upwards and if I didn’t do that the air goes straight up into the engine bay...
I didn’t test yet because of coronabulls***
You can easily do that on your micras, i did both in 4 hours flat..
I predict a much more ready And clever engine, a faster throttle response, and a slightly better acceleration/resumption from release-press the pedal .. and more instant torque.
Here we are with an update!
I tryied the car with the air conveyor mod and it’s really improved, it’s super-ready at the throttle, a more rapid response, and more you push more you have because the in-pressure raise... big thumbs up at this mod, super recommended.
A sprintfilter sport filter!



Look at the astonishing differences between the two filters, only imagine the differences in soaking air... at the right the Sf under sun rays.


And here the Bosch filter ( better than others) under sun rays, you CAN’T see through, instead in the , yes!


With the car in idle, revving up is more easy, the engine run unrestrained.
With the car in moving, the 1-2-3 it’s improved in a impressive way.. the 3rd gear is quite similar at the 2nd in terms of rapidity of gaining speed, torque and power...the engine is really unleashed...
Anyway i suppose the ecu needs some time to adapt her values with the newer ones, in these days i will go to contact an expert (found in a mechanical group) to ask him if i need to unplug the battery for a reset..
Jolly good, that’s my “phase 2” intake mod, the phase 3 is removing all the airbox and use a direct air intake ( like kd1 Sf intake or something like that) (phase 1 is change the panel filter)..
Post your thoughts below !

And a big cleanse!


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Hi Johan, I'm glad that your experience with this mod bore out my experience of the results, these little engines are strangled from breathing with the factory inlet configuration, all it needs now is the rev limiter to be raised to 7000rpm instead of the 6.5/6.6 that it currently has . I find that is still pulling like a train in 2nd and 3rd gears when it hits the limit :mad:. Changing up from 4th to 5th gear at an indicated 100mph does surprise some people 🤭
I feel the same way..i think the ecu is the very limit of the engine..
My very next mod is a straight muffler to improve gas exhaustion, which helps gains power to the high rpm range..
By the way the 3rd gear spool up over 110 kmh.. (65mph?)
Did you follow Rauf cars on youtube? He has an 120bhp k11 micra! Really interesting to follow.
I can't be alone in thinking that a little extra performance could be squeezed out of the non 1.6 or diesel engined cars if the engine could breath better.
Not wanting mind numbing induction roar I steered away from open air filters, (though in hindsight, what I have finally come up with could be useful in that application as well), so the initial stage was to buy a K&N panel filter to replace the standard paper one.
The next thing I wanted to do was find a way of neatly replacing the, apparently very restrictive, air feed from the slam panel, with a resonant chamber in it, with something considerably more free flowing.
I had a look at the air feed box under the filter and soon realised that there was two variations (both with yet another resonant chamber 'stuck' on the side.
The one on my car was the post 2005 design:-


Resonant chamber integral with the box:-


The inlet spigot fouled up with support webs for the chamber on the side:mad::-


The earlier version had a separate chamber attached to the side of the box with rivets:-


And with a usable inlet spigot :cool:


With this in mind I decided that the earlier version would be better to 'play with' and I managed to buy a complete early type engine top cover/ filter box on ebay, for the princely sum of £14.50 inc carriage, with the bonus that it came with a spare MAP sensor and vacuum switch and piping still attached:cool:


Having got the replacement earlier filter box to play with, I measured up the spigot, finding that the O/D was a just under 55mm and the bore tapered from 50mm at the opening to about 46mm on the inside edge.
I plan to open this up to a consistent 50/51mm to maximise flow.
The next stage was to design a suitable 'big bore' cold air feed that looked as if it was OEM;)
More to follow tomorrow.......

Well the clips finally arrived today, so no time was wasted fitting the parts:-


Looks neat and seems to make for a smoother acceleration through the rev range, and appears to hit the 6.7K rpm rev limiter much faster now ;).
The old system was restricted to 39mm dia at the airbox entry, now 51mm dia there and the slam panel air gatherer had an outlet dia of 41mm, now 57mm diameter with 60 mm I/D flexi to the air box :cool:
Now we are making the most from the K&N panel filter!
Looks really smart, I wouldn’t mind doing the same to my little 1.2 S. It’s a long shot as I’m not sure you are active anymore but would you mind linking the elbow and the pipe (if they still exist). Great job 👍🏼