The B20VTEC discussion thread

[ericl33]

^ Pretty sure those questions have been answered time and time again in this thread, have a read guys

My old jdm b18cr decided to grenade itself spectacularly last year so I have been putting together a b20vtec setup for quite a while now for local track days (just for fun, not really following any rules). Main points of interest are wiseco 84.5 pistons, eagle rods, knife edged/grinded b20 crank, cnc closed deck, ITR head with OS supertech running gear and kelford 176-c cams. Final static comp turned out at 11.8:1. Had it on a run in tune with standard ITR cams and a Spoon header, standard jdm dc2 b-pipe + Spoon N1, ported ITR intake mani and 68mm TB and it was making 155hp at run in limit of around 6900rpm on 101's dyno. The powercurve with the ITR cams was not very smooth though, and came onto vtec pretty aggressively, the curve almost doubled its steepness @6000rpm upon engagement. Its done about 1000km and one track day on the run in, but I pulled the motor back out to do a few other little things to the car and have changed to the kelford cams and a larger b-pipe so we'll see how they go with a real power tune with more rpm and a smoother curve with more low down torque.

Even on the run in its a really fun setup to drive, and with everyone going K series these days there is still life in the b20vtec for sure.

Any comments on the setup are appreciated

why eagle rods? don't like stock?
is this what knife edge crank looks like?



what's benefit?

tried searching for CNC closed deck, not sure what it does.

any extra bracing?

[Water Boy]

The purpise of knife edging is it reduces the parasitic drag from the oil mist in the crank case. So basically it cuts through the mist and less oil condenses on the counterweights. All these kind of things cost horsepower. If you look at REALLY expensive race cranks, they'll be fully polished.

[ericl33]

The purpise of knife edging is it reduces the parasitic drag from the oil mist in the crank case. So basically it cuts through the mist and less oil condenses on the counterweights. All these kind of things cost horsepower. If you look at REALLY expensive race cranks, they'll be fully polished.

thanks m8.

[tinkerbell]

what specs on your engine if you dont mind?

bearing clearances 0.0015"
piston to wall 0.002"
ring gaps top - ~0.01"
ring gaps middle - ~0.02"
bore - 84.5mm
stroke - 89mm
chamber volume - 40.5cc
deck height - 0.017"
head gasket - 0.04"
piston volume +5.3cc

[Alexx]

The last oem rod I used is sitting on my desk in 2 pieces snapped in the middle. And the exchange rate was excellent when I got all the parts for this motor so the eagle rods were a no brainer.

Yes that is what a knife edged crank looks like. But that looks like a manufactured one instead of a modified stock crank. In addition to the above, it pulls weight out of the crank and balances it. My only real criteria when putting the motor together was that it behaved like my old type r motor, so i wanted to take it above 8krpm all day at the track and not have to worry about it. The response with all the lightened internals is real nice so far.

B series motors have floating bores/open deck from the factory, and with b20s the sleeves are particularly thin compared to b16s and b18s. Closing the deck holds the top of the bores in place. There are plenty of theories as to weather closed or open deck is the way to go (open deck for best coolant flow vs closed deck for bore strength), I basically just told my engine builder that it would be used for racing and left it up to him - but I didnt want to sleeve the block. You can buy 'block guards' to fill the gap but they are rubbish and place uneven pressure on the bores often leading to ovalled bores and premature failure. The block was placed on a cnc machine to trace the block and bores, and a plate was machined up with tapered sides to suit the motor and is pressed into place. The bore is then honed after the plate is installed. Cooling is addressed with appropriate coolant channels in the plate. I do run a large radiator though.

Its most likely overkill on an n/a setup but after my last motor blew I wanted to make this one as strong as (realistically) possible.

Im sure others with more experience can offer their opinion on closed deck vs open deck and maybe vs sleeves. Generally pre fabbed block guards like golden eagle etc are frowned upon though.

Specs to compare to tinks are
bearing clearances 0.002"
piston to wall 0.0025"
ring gaps top - 0.014"
ring gaps middle - 0.02"
bore - 84.5mm
stroke - 89mm
piston volume - 43.4cc
deck height - Standard
head gasket - 0.03"

[ericl33]

thanks very much for your insight

Appreciated.

[tinkerbell]

a plate was machined up with tapered sides to suit the motor and is pressed into place.

crank is not braced?

[Alexx]

To be honest im not sure of the exact specifics of assembly. It does run the stock girdle if that is what you mean?

[tinkerbell]

It does run the stock girdle if that is what you mean?

there is no stock girdle on a B20B block...

[FAITHLESS]

there is no stock girdle on a B20B block...

Interesting.

[tinkerbell]

Interesting.

or maybe it is more accurate to say:

there is only a crank girdle on B18C blocks...

[Alexx]

Well there you go. Like i said im not sure. Motor was specced and assembled by Jhh with a few parts off my old type r b18c motor. I can find out though.