The 92mm crank is custom. It doesn't come from an OEM application.
That is what I originally thought as well, but Magnus lists two 2.2 litre engines on it's website one using a 4G63 block and the other a 4G64 block and for the latter it states that you can use either a Magnus or an OEM
crankshaft. THAT'S an interesting idea. I don't see how the bore would affect the rod/stroke ratio BUT I've been trying to figure out how to do an all OEM stroker for the "cheap" build. Taking a G4cs to 0.020" over would make it 87mm. Then if you sleeved it back to 85.5mm you could run run 0.020" overbore 2G pistons which would put you at 2.3L exactly. Of course with the longer stroke the 8.5:1 cr would be bumped up to 9.7:1...thicker HG puts you at 9.5:1. If you ran 1G pistons then the CR would be 8.86:1. I like it. Is it possibly to sleeve an iron block though?
I don't think there is any problem doing it, I think it just has never been done because it isn't necessary. People usually sleeve aluminium blocks to make them stronger the 4G63 is already strong enough to take more than most of us can throw at it. The purpose of sleeving the block here is different.
Given what you have said I have probably cocked up on my assumptions about the rod/stroke ratio and bore. I thought that a larger diameter bore would exacerbate
the cylinder side load throughout the stroke. If it doesn't then there would be no benefit in doing THIS:
(a) What if you utilized the same 2.1 litre configuration above using a standard 2.0 litre bore. Would you lose power or low down torque?
What I was getting at here was that I thought the smaller 2.0 litre bore would create less cylinder side load.
My question to loss of power or low end torque was aimed at the difference between 'normal' 2.0 litre motors and long rod ones. Normally you don't get something for nothing and since the Mitsu engineers chose not to use long rod configurations that gave a higher rpm limit, I assumed that this affected not just the rpm limit but perhaps the power band, pushing the usable power to higher rpms not utilized as much on the street.
As you stated You could still possibly do this with a long-rod setup but if you wanted to do it on a G4cs you'd have to sleeve the cylinders as mentioned. I doubt you'd get different torque character than from a normal 2.0 but you'd have a rev-happier motor. Of course the standard 4G revs just fine so I'm not sure what the point would be.
If bore has no effect on rod/stroke ratio, there would be no point. You would be making a huge amount of work to lose 70cc of displacement without gaining any rpm advantage.
(b) And if so could you play around further with custom road lengths/piston heights to create a 'stroker' with a higher rpm limit? (c) What effect does the CR have here? NA motors with high CRs can spin to high rpms so could you bring torque at lower rpms back by using a higher CR and still keep your RPM limit? (Many 2.3s already use 9.0:1 CR or higher!)
This is where my understanding stopped!!! I was under the impression that displacement in the 2.3 stroker was achieved not only through using a larger bore, but by using a 'shorter' piston that allowed more air/fuel to be drawn in. What I cannot get my head around, is that if the stroke remains constant, by doing that surely when it came to the compression cycle you wouldn't be able to achieve the same compression ratio because you'd have a bigger 'gap' at the top of the stroke. Obviously I'm missing something here.
I don't have it with me but a while back I sat down and did all the math for rod/stroke ratios of 2.0, 2.1(destroked 2.4), 2.3(stroker), 2.4(standard), and 2.4(long-rod). The 2.1(destroked 2.4) has by far the best rod/stroke ratio but I just don't see the point when 2.0 will do 10k already.
Magnus quotes 11,000 rpms but yes I take your point. Is all that work worth it to make the 2.1 litre gaining in fact just 70cc displacement, if a long rod 2.0 utilizing the same block can rev just as high?
I just wonder how much longer the bores would remain intact with that better rod/stroke ratio? I appreciate people will say I am mad for thinking about this but my direction on this was why not build a rock solid 2.0 litre super long rod engine with a valve train and head that could flow to 8,000 rpms. You could theoretically rev to 8K all day and still have a 3K buffer to your actual threshold. As I said I was just concerned whether lower end torque would be affected. I'm interested to do this with a slightly higher compression.
Finally, if the 4D68 crank fits in a 7-bolt 4G63 would it fit in a 4G64 7-bolt? That might give you the option of a 2.2 litre stroker utilizing all OEM parts and that idea I do like!
2190cc and a theoretical 10K plus rev limit. I would almost guarantee that means the answer to my above question is NO!