Not sure if this belongs here as it's just all theory at the moment (though could quickly be converted to reality)
A few people may know the banana teg is not my real project car and in my shed I have a very neglected and dusty EF7 crx which was on it's way to becoming a track car when it got sidelined way back when I put that H22a in my old EG (which became an NZHondas whre car for a while)
Then it got sidelined for an H2B coupe, then a JRSC Teg so now I think it's only fair that I finish what I started 5 or 6 years ago.
OK so heres the plan...
I want to use it in the Motul Honda cup, obviously not this season thats just not going to happen, but I'm hopeful for 2011 if they still let EF's in.
It had a turbo d-series ZC hybrid in it which was a bit of a technical feat in it'self but I have since pulled it out and sold most of it and very soon I'll start the new engine.
I have 'aquired' an F20b dohc vtec form an SiR accord. As a few of you already know this is a baby type-S engine with 11.0:1 compression and euro-R camshafts. Well the manual one anyway.
Mine's out of an auto but it's only a matter of getting other cams which I'll get to soon to make it a 200hp ripper with actual torque as well which we all know B's lack.
I have spent a lot of time on the existing d-series L3/S20 gearbox playing with the ratios, installing an LSD and I'm, pretty happy with it and I really want to keep it.
a) Parts are cheap and available
b) M-factory etc are doing gear kits now
c) Quaife do LSD's
d) a million and one oem gear combinations available form all sorts of models.
and probaly most importantly e) H/F series gearboxes are shit, they're massive, heavy and aside form custom gear kits there's little you can do with them.
So the first Frankenstien mod is an Evolution F2D kit which will allow the use of an H or F series block with any post '87 d-series box, cable or hydro.
These are $800US and include billet mounts and a flywheel and everything you need.
And to up the awesomeness level my brother will make me a set of these too in 50mm dia
I already have the hondata needed to tune them.
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OK thats not that unusual but now it starts to get weird.
This is the BTTC accord owned by Gary Morrell in Taupo.
It's also an F20b but there's somthing a little strange going on.....
It's head's on backwards. And the benefit of this is the trumpets are facing directly into the airstream like a K-series.
At first when I saw this I thought it was some serious engineering and wondered why they would bother to go to so much trouble just to ensure cold air.
So today I went down to my lair and grabbed the F20b head off the bench and plonked it on the block the other way around.
Bores line up perfectly.
Head bolts line up perfectly.
Aside from a few of the sensors and obvious cam shaft backwards issue it's pretty straight forward. Easier than getting the dohc head on the sohc block with the ZC.
I've worked out I can actually use off the shelf H/F series cams, all I have to do is lathe off the retainer ring from one end and press another one on the opposite end because without it the cam will 'float' back and forth, which is not good.
Other than that the cam is basically symmetrical.
The cams will still spin anticlockwise the way they were designed to but the inlet cam will be at the front and the exhaust cam will be at the back.
I can even still use the timing marks on the camgears
This means the dizzy will have to be mounted on the rear cam like it is in a ZC ratehr than the front cam like it is in the F20b normally.
Obviously brackets will have to be made and different diameter seals will be used to stop leaks.
What appeared to be a big undertaking is actually simpler than first thought.
Here's some pics to show what I mean....
Thats the head on backwards and bolted up.
Camgears where the dizzy should be
Will have to relocate the oil filter. The headers will run down the back liek a K20a
Plenty of room for the water feed tube.
These are the rings which need to be lathed off
Dizzy now sits on the rear cam not the forward, you can see the slot for it on the left cam.
Pullies line up pretty well, can always shim/space them if necessary.
The cam pullies will need to be lathed a bit in the centre to clear the hole in the head at the end of the cam.
Lobes all align mint even though they're backwards
Obviously all this balance shaft shit will go in the bin.
Other than that theres a few water fitting which have to be shifted, this one fouls on the cam belt..
The oil feed to the head will have to be external.
The oil feed to the vtec pins will be external and permanent. (vtec always engaged) This is because the solenoid has to go in the bin because now there is a cam gear there.
OK now here's the next stage.
Ian alerted me to the existance of a motor called an F18b which is a sohc vtec 1.8 litre which came in the 1.8VTS accord (around 1997)
Its got an amazing bore/stroke ratio of 85 bore x 81 stroke, it's the same bore as an F20b but the stroke is a full 7mm shorter!!
Thats a bore/stoke ratio of 1:0.952
That shits all over a B18c. B18c bore is 81 but stroke is way longer at 87.2
Thats a ratio of 1:1.07
And as far as bore to stroke ratio goes it even just beats a B16a/b.
The B16a's actual stroke is shorter at 77.4 but the bore is 81 so thats a ratio of 1:0.955
Now if we bore the F18b out 2mm from 85mm to 87mm and put Euro-R 87mm H22a pistons in it all of a sudden that bore stroke ratio gets even better.
1:0.931 Quite undersquare.
It's essentially now a de-stroked F20C (S2000 engine)
The F20c has an 87mm bore, same as H22a but has a stroke of 84mm
We will be the same bore but the stroke will be 3mm shorter.
The archilles heel of the S2000 engine is it's high piston speed (highest piston speed for any mass produced consumer engine)
Reducing the stroke by 3mm reduces the peak speed of the piston considerably.
So what's this all in aid of?
Well if an F20b in stock form can be revved to 7800 - 8000 at a stretch and even it's big brother the H22a can be revved to 7500 surely this 1900cc short-stroker should be feasibly good for 8500 - 9000.
Im summary it will be:
F18b block rods and crank.
H22a pistons (maybe mounted 180 degrees around to match pockets to valves)
H22a head on backwards
vtec killer cams
12.0:1 compression (head shaved and single layer gasket)
Question for the gurus is..... Are honda pistons made with off-centre gudgeons? Can I rotate the piston backwards without them tipping over and jamming in the bores under load.
(many pistons are designed to focus combustion energy down one side of the piston to counteract the off-centre load applied on it by the resistance of the con-rod and off-centre crank journal)
Because I'm still rotating the engine anti-clockwise flipping the pistons could mess things up a bit.
Why not get a K or even a fully built B?
Because the CRX has always been a platform for me to try new shit and this is something I look forward to conquering.
I think I can build it for less than a K20a or a 1900cc bored B18c as well. (B20 is shit I wouldn't go there, strokes too long at 89mm)
It wont happen all at once, the car will get the straight F20b F2D swap first, then the ITB's made by my brother.
Then while thats running I'll build the head-spun H22/F18b and when it's ready swap it in.