KR Vs ABF combustion chamber size.

Are the combustion chamber sizes in these two cylinder heards the same size ?

thnks

Rob.

 

They are a differnet shape depending on Head type, lots of threads on this .

 

I would certainly imagine that if they both share the same compression ratio the ABF will have a slightly larger compression volume (Vs over Vc = Cr)... Which makes me think that when I fitted my KR head to my ABF bottom end many years ago I upped the Cr slightly. No bad thing, though might encourage it to pink using an un-tined K-Jet setup.

Just a thought.

Jai

 

I have a KR head and an ABF bottom end.
I have CC'd the KR head but so it would be interesting to know the volume of an aBF head.
I did use the search but I will ty again.
This will be for a FI project so I think I will probably source an ABF head as even with stacked gaskets it looks like thr ABF CR will be 9:1.
I guess it would be even higher if I used a KR head.

 

All the 16v EA827 heads are 45cc.

 

They're not the same compression ratio

KR is 10:1
ABF is either 10.5 or 10.8:1 - can't remember off the top of my head, but I'm sure that Toyotec knows

 

Ah, well if the ABF ratio is slightly higher it could be the fact that the head volume is the same size then.

Best handover to an expert... lol

 

Abf, 9a, Ace = 10.5
Pl, Kr, Adl = 10

 

ABF Head



KR Head

 

compression is different because of the longer stroke not the head volume, sure the volume is the same

 

My old photos taken for Brookster when he encountered head interferance with his high compression slugs using an ABF bottom end and later KR cylinder head. Gasket =multilayer 2.0 unit.

ABF Head 051 103 273 D

This cylinder head has a gentle dome and has less shrouding around smaller 27mm exhaust valves.

KR Head 051 103 273 (same as pre 94 9A and 6A units) see also 027 103 373 E

This head is deeper and is more cylindrical with more shrounding around 28mm exhaust

Both heads hold 45cc of volume but with modified combustion shape.

051 103 273 D OE fitment on ABF post 94 9A and ACE 10.5:1 and ADL 1.8 10:1
051 103 273 OE fitment on KR 10:1 , pre 94 9A a and 6A engine 10.5:1
027 103 272 E OE fitment on pre 89 KR and PL engines 10:1

 

45cc so i was right, I thank you

 

so the reason he had interfearance issues was because he had non standard high compression pistons installed?

 

Yes Wossner 12 : 1 comp

the piston crown is 1.4mm higher than standard, had the head modified to suit.

even when i took the standard pistons out there were signs that they had been catching a some poit in their life.

 

due to the size difference in exhaust valves, which of these heads would be best for use on a turbocharged 16v?

Am i also to belive that the ehxuast valved in the KR head are sodium filled, but the ABF exhaust valves are not?

 

the kr has sodium cooled ex valves the ABF doesn't so KR valves would be better

 

would the larger KR exhaust valves promote a higher exhaust gas velocity? or am i talking rubbish?

 

depends on the port shape/diameter

I'd talk about it with the man in the shed, he knows a lot about it

 

Holy thread revival.
Found this looking for info on comb chamber volumes.
My ABF pistons are 0.7mm above the face of the block at TDC.
The MLS gasket is 1.75mm thick
Comb chambers are std
valve cutouts deepened and a calc says they are now 1cc each.
My calc suggests the existing CR is 10.5.
Right, my question about aftermarket 'off the peg' forged pistons ( listed at around 12:1) is ......... is there any mods generally
needed to the combustion chamber to allow these 'off the peg' pistons to fit (ie rotate) ?

If they 'off the peg' and work fine it must mean the extra material on the crown is within the combustion chamber....