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VTEC on B18c4, and ECU question


Lars P

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VTEC on the B18C4 with the Dual inlet is at 5800 rpm. At 4500 you get a slightly stronger pull towards VTEC hence the dual inlet design.

As for changing the thermostat, cost wise its probably about £20 from a motor factors and yes you do need to drain coolant to change it.

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The PK9 is just tuned properly/sensibly, they put the vtec point where the two cams cross over so its a smooth transition.

If you raise the vtec point 100 or 200rpms you'll get a more aggressive jump and a tyre chirp, the car won't be any quicker but you'll feel the change.

Also there isn't just one vtec point

If you're giving it beans (above 65% throttle usually) you'll hit the hard vtec point @4400rpm, if you're cruising and slowly increase speed (below 35% throttle) the car wont switch to the vtec cam till 5200rpm or so.

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Useful info about the VTEC rpms tontvti! Wasnt aware of that!

In regards to draining the coolant, I suggest you buy the Holts SpeedFlush 2 system pack,

http://www.halfords.com/webapp/wcs/stor ... yId_165750

only costs 6.99 and if you follow the step by step guide on the back it works like a CHARM! Cleans out the full system of limescale deposits!

Good Luck! And keep us posted!

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Tonvti am sure that is wrong mate - are you saying the mb6 is some how graced with two VTEC points when even the Type Rs have one?

The MB6 has a dual runner intake. The 1st runner is go upto 4500rpm. At this point the 2nd runner kicks in to give you the mid range punch to drag you to VTEC and then the change in Cam profile happens at 5800rpm. :mrgreen:

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IMHO It should be even more than two points, a 2d table that would activate it depend on load/IAT/coolant temp over a variety of RPM.

If you're cruising at 4600rpm by your theory it would be in vtec pointlessly wasting fuel on the more agressive cam.

It has to change to the more agressive cam regardless of load at a later point because the lower cam runs out of steam.

Thats how its done in my editing software, TBH I assumed that follwed the stock code. Every other switchable Cam ecu I've seen was load/rpm dependent not ust rpm dependent. Seems like a total waste of fuel to just be rpm dependent!?!?

"Assuming makes an a*s out of you" I Know :mrgreen:

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Tonvti am sure that is wrong mate - are you saying the mb6 is some how graced with two VTEC points when even the Type Rs have one?

The MB6 has a dual runner intake. The 1st runner is go upto 4500rpm. At this point the 2nd runner kicks in to give you the mid range punch to drag you to VTEC and then the change in Cam profile happens at 5800rpm. :mrgreen:

Thats wrong mate, the cam change happens at 4500 rpm, the dual flappy thing in the inlet manifold opens at 5800, and is controlled by vaccum, which is switched electronically by the ECU.

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i don't understand this :?

VTEC on the ATR, ITR, CTR, etc enagages slightly before 6k rpm. Now why would honda have the VTEC on the MB6 engage so early just does not make sense.

So that means the high cam profile engages for almost 4k on the MB6. To be fair the MB6 is just a 4 door hatchback not some focused sports car like the ITR. Jalesi do you have some official white papers or tech info which backs up what your saying?

Thanks

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Tonvti am sure that is wrong mate - are you saying the mb6 is some how graced with two VTEC points when even the Type Rs have one?

The MB6 has a dual runner intake. The 1st runner is go upto 4500rpm. At this point the 2nd runner kicks in to give you the mid range punch to drag you to VTEC and then the change in Cam profile happens at 5800rpm. :mrgreen:

Thats wrong mate, the cam change happens at 4500 rpm, the dual flappy thing in the inlet manifold opens at 5800, and is controlled by vaccum, which is switched electronically by the ECU.

This is right the cam change is at 4500 rpm (Vtec). and at 6000 rpm the butterflys open in the inlet . which people think is vtec .

The reason vtec comes in at 4500 rpm is that the compression ratio on a b18c4 is 10:1 compaired to the itr and others with the single stage of 11:1 so the lower vtec keeps the torque up mid range but then the power would have dropped off top end of the revs so that is why you have the butterflys to boost top end power . this set up gives good power . but its not as good as itr and others that honda sold a sports cars .

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