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Romans 2005 Toyota Echo


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Here's some afternoon diagrams to go with the morning graphs @yoeddynz

So while I was trying to figure out the VVTI situation, I was trying to think if the crank being offset in the block helps give piston clearance for vvti (piston accellerates away from TDC faster?) 
The crank sits 11mm further towards intake side of the engine, relative to the centreline of the bore.

I just finished some of the drawings to take some measurements from to try understand whats going on with this.

So there's some weird shit that goes on as the piston accellerates at different rates depending on if its coming down or going up. (when rotated clockwise)

When the crank is laying flat at 90 or 270 deg, the piston is a different distance up the bore for each.
On the way up, it's 6.962mm higher by that time, than the way back down.

image.png.741d9206ec779dc4aa5cdaf72b1dbed0.png


Then also, the crank angle at which the rod is perpendicular to the crank, happens at an earlier time on the combustion stroke than compression stroke.

It happens at 21 degrees above horizontal instead of 12.44 degrees. Maybe there's a better gas expansion ratio at this point, of the gas expanding relative to the combustion chamber volume expanding. So more force can apply on the crank.
Or something else dunno. Either way it's weird shit.

image.thumb.png.2fc3e73ecda977ce1abdb43d20c5af09.png



Also some weird shit happens around 90 deg of crank travel on the combustion stroke. Where the rate of accel does weird stuff. I'm guessing this is also something to do with having the piston exert more force on the crank at that position.

image.png.305d4a545cb49fcf881f4187bb0af198.png
 

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Designed so the when at maximum expansion force from the burning mixture does not coincide with the point of most leverage on the crank, thus smoothing the forces out somewhat on the crank making for a more linear rod force to crank ratio line? 

Hard to explain when typed out but you probably get it. 

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Yeah! Must something like that. Says in toyota stuff that it's done for sake of more torque. 

Also some of the above stuff is incorrect because I just read its got a 12mm offset not 11. D'oh.
Will be the same but more exaggerated I guess.

Also, gash expansion is an interesting typo to make 

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Yeah, good point!
Although, to be fair I've stopped having problems with the crank bolt coming undone since doing it up tighter, and using some loctite haha.
If the crank had a keyway in it, I bet I never would have had problems in the first place. Just a cheaper shittier design this way.

It's quite smooth at high rpm though, it doesnt feel like it's going to explode into a billion pieces.
Like I cant quite explain it, but some motors happily do high rpm but dont sound happy about it.
It quite happily revs out and feels/sounds like it wants to keep going.
Not a particularly scientific conclusion but there you go. haha
 

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I wonder how long rings last at 10,000 rpm.

 

Those earlier graphs of piston location vs angle are quite interesting.

They make it ideally suited to long duration cam, can get quite deep into the compression stroke with open valve before it pumps much air back out.

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No matter what the actual RPM is, being able to get the tacho needle off the dial is immensely satisfying.  Making power is just a bonus

Edit:  Does the 1NZFXE have asymmetric rods to go with the offset crank?  I'm remembering the Subaru EZ36 which dropped the crank 20mm and had pork chop rods to help make everything fit / reduce geometry issues

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Balancing is an absolute must.*

*really should do.

Granted factory stuff is pretty well made these days. But those chinesium rods, who knows?

I tried to balance my own rods once. But the scale was so sensitive I couldnt get it to repeat.  Plus you really need a jig to do it right. 

Spending money building engines takes the shine off pulling 987654321 RPMs after the 2nd or third engine  goes bye bye. Not to mention the opportunity cost of doing that, instead of squeezing power by doing (or experimenting with) other things. 

Also, have your crank, flywheel, pressure plate, and front pulley all balanced together too. (You can easily upgrade to a puck disc later if the neck snapping, pantie dropping torque gets too much for the organic unit) 

I've made a career out of taking shortcuts. And learned the hard way......

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14 hours ago, keltik said:

No matter what the actual RPM is, being able to get the tacho needle off the dial is immensely satisfying.  Making power is just a bonus

Edit:  Does the 1NZFXE have asymmetric rods to go with the offset crank?  I'm remembering the Subaru EZ36 which dropped the crank 20mm and had pork chop rods to help make everything fit / reduce geometry issues

It doesnt even have a tacho :lol:

Nah the rods are straight, but on one side of the block they come reeeeaaallll close - most aftermarket rods you need to grind the block to make them fit. 

JUN conrods are actually a bit banana shaped so they fit without needing this. But those are like 4x as much so yep, die grinder it is. haha

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If I do some calcs for how much I've removed, being on the generous side at each step of the way it's something like 0.015cc per valve. 
Then maybe some extra off the bridge parts so lets say 0.1cc total per chamber or even double it to 0.2cc per chamber

Then it's still only lost say 0.1 CR absolute max.
So I'm still waaayyyy ahead of where I would be if I had to use the 13:1 pistons to get VVTI working. Or If I had to dig some valve reliefs into the pistons. 

So if it can breath only fractionally better at high rpm it's well worth the trade.

image.png.c820278cb4207fc2f6146e11ff2efe2c.png
 

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