Decreasing Displacement of a 1uz

[1uzUltra4]

Im currently in the Early stages of building an off road race truck.

Due to class restrictions the Maximum capacity in the class i shooting for is 3900cc Im hoping to use the 1uz which has 3969cc, but this last 69cc is going to push me into an unrestricted class. What im wanting to know is how hard would it be to decrease the displacement of a 1uz back to 3899cc.

My initial thought would be to Machine down either the block or head the required 1.4mm to reduce the displacement enough or get a set of custom pistons that would reduce displacement enough. But as with all things im sure its not a easy as this. What would the best solution be for doing this or am i trying to do something that is never going to work?

Any and all help would be greatly appreciated.

[Hiro]

Im currently in the Early stages of building an off road race truck.

Due to class restrictions the Maximum capacity in the class i shooting for is 3900cc Im hoping to use the 1uz which has 3969cc, but this last 69cc is going to push me into an unrestricted class. What im wanting to know is how hard would it be to decrease the displacement of a 1uz back to 3899cc.

My initial thought would be to Machine down either the block or head the required 1.4mm to reduce the displacement enough or get a set of custom pistons that would reduce displacement enough. But as with all things im sure its not a easy as this. What would the best solution be for doing this or am i trying to do something that is never going to work?

Any and all help would be greatly appreciated.

The only thing which affects displacement is the diameter of the bore and the stroke of the crank. Skimming the head and changing the pistons affects compression ratio only. You'll either need to get a short-stroke crank, or sleeve the block (and then run smaller diameter pistons).

[1uzUltra4]

The only thing which affects displacement is the diameter of the bore and the stroke of the crank. Skimming the head and changing the pistons affects compression ratio only. You'll either need to get a short-stroke crank, or sleeve the block (and then run smaller diameter pistons).

Edit -

I think i now understand what Hiro is saying. It would increase the compression of the engine as the displacement stroke X area is the same being forced into a smaller area.

So i would need a different crankshaft or a reground crank shaft to shorten the stroke or smaller diameter pistons.

Which is the better option and which is the easier option with a 1uz?

[Bazooka]

I'd suggest looking at offset grinding the crank and finding a suitable longer rod. There may even be something from another engine suitable to keep costs down.

[oldeskewltoy]

I'd suggest looking at offset grinding the crank and finding a suitable longer rod. There may even be something from another engine suitable to keep costs down.

This...

BUT the oil routes typically are centered in the journals... so offset grinding COULD weaken the crank too much... BUT it is likely worth it to see if it can be done. Cutting 69cc shouldn't be too hard......


Hmmm brain fart... not doing the math... i wonder to "lose" 69cc could the offset re-grind be "absorbed" with just a larger bearing shell???

[dnegative]

8.6cc a pot required..... might be close lol

[1uzUltra4]

Wouldn't a different sized bearing have the same effect as longer/shorter rods? Wouldn't displacement have to do with the centreline of the bearings on the crankshaft?

After talking to a few people it looks possible to do it but at this stage the cost of an making a custom offset crank, i could fab up a m112 onto the 1uz or turbo it and run in the unrestricted class.

[TheStitt]

If you go to the unrestricted class, turbo a bigger motor..

[Hen]

Regarding bearing size, I think he was refering to offset grinding the crank to reduce stroke, then using larger bearings to take up this reduction, meaning you can use standard bigend size. Though you'd need to either using a slightly longer rod, lower wrist pin or deck the block to ensure the piston doesn't end up down the bore at TDC, so having to run smaller bigends probably isn't the end of the world.

All in all I think you'd be better off going bananas in Unrestricted or choosing another motor to stay under 3900cc. 2GR maybe?

[lexsmaz]

As has been said if you go in a open class just start with a bigger motor & turbo that, as an example a LS1 is physically smaller than a 1UZ & a lot more powerful straight out of the box due to its bigger capacity, or get a smaller capacity turbo motor like a 2 litre that will keep you under the 3.9 litre open class ..

The 1UZ option is just going to cost you heaps for something that is a nice motor but nothing mind blowing as at the end of the day its only a 4 litre capacity motor ..

[1uzUltra4]

Thanks for the Info guys, It looks like im going to have to look for another motor. Running my buggy in the Unrestricted class is not an option if i want to be even close to competitive.

So slightly off topic any toy engines sub 3.9L with the same or more power and torque than a 1 uz?

[oldeskewltoy]

So slightly off topic any toy engines sub 3.9L with the same or more power and torque than a 1 uz?

to your slightly off topic question... I offer you a slightly off topic answer....



Here is a destroked (3.5 liter) 1GR - 440hp... $17,000

[trdee]

built 2GR-FE might be cheaper and easier? reading in that other bloke's thread the 1GR seems to be a lot less performance oriented in its architecture compared to the 2GR.

[Hen]

What is the mulitplier for turbo? I'd look at a 2GR, or a decent turbo on something smaller that would keep you under the limit (3S, 2ZZ, 4A, ??). It also depends how much work/money you want to put into the motor.

[lexsmaz]

Unless its changed the multiplier used to be by 1.7 ..

The 1jz just misses out it comes in at 4.25 litres ..

The Maximum for a forced induction motor works out at just under 2.3 litres ..