TROUBLE 20v TurboHELP URGENTO!

[vvega]

did you get the bottom end rebalanced ????



v

[Mr Revhead]

why would he need it rebalanced??

[JT]

Because he modified the pistons (and obviosuly pulled the block apart) and you wouldn't want the rods and crank to take any undue stress caused by being off balance.

[Mr Revhead]

but the pistons go up and down, no rotatinal inertia invloved....
the later pistons have no balancing holes/weight in them even though they have quite large cutouts in them.

[rollas22]

To clear everything up:

1. the pistons got machined perfectly to match each other, they have for small cutouts in each piston (perfect balance)

2. the block and everything has been all put back together by a mechanic, everything was measured and checked against toyotas specifications in the 20v workshop manual.

3. Nothing hits/grinds when the timing is all together and correct.

Just a note, this car will be on show for all to see at up n coming shows. Also will be forsale in the near future - to purchase a investment home

[vvega]

oh well dont say your wnet worned

and mr revhed the pistions are part of the balancing equasion
if you change the wieght of them then the counterwieghts on the crank will have to modded
not wieght to each pistion ethier
the wieght difference to the old pstions

v

[Mr Revhead]

are you sure on that?
when balancing rods etc what you are really doing is making sure they all weigh the same.
the counterweights on the crank are to counterbalance the journal side of the crank... not the pistons.
and as his rods are the original ones i dont see that as a problem
when you balance a crank you do it to make sure it rotates with out vibration due to one side weighing more...

[rollas22]

Just a quick note these are AW11 pistons being used in a 20v Block with 20v crank. They where all machined the same @ speedtech NZ in wellington, they shud know there stuff as they built the 20v turbo DX corolla...

[86 Power]

Post some pics for everyones benefit

[vvega]

What is Balancing?
Balancing is the action of matching weights of the reciprocating parts of the engine. These parts include, but are not limited to:

Pistons and Piston Pins
Piston Rings
Rod Bearings
Connecting Rods (large and small ends)
Crankshaft
Damper (harmonic balancer)
Flywheel/Flex plate
Pressure Plate/Clutch
"Estimated" Weight of oil
Once you have these parts together, the process of Balancing the parts goes as follows:

First, the individual parts are weight matched. These include the pistons, rods and rings. There is not much you can do to the rings or rod bearings so, other than just setting up the "File-Fit" rings before balancing, all you do is supply a "single set for "one" piston" to the shop doing your balancing. You first weigh all the pistons and all the rods, locating the lightest of each. At that point, if you are reducing weight of these items, do it first to the lightest parts. You now match weight of the pistons and rods.

NOTE: "All" other machining must be done BEFORE balancing is attempted...!

The RODS are matched as "small ends" and "big ends". This means you match all the "big ends" by hanging on a special hanging fixture, then you do the same with the small ends. Be sure to double-check!

The PISTONS are also weight-matched, but the "material removal" machining is done either under the piston pin boss with a special offset cutter, or it is done by drilling holes (very carefully) on the surface of the pin boss. You do this to both piston bosses, sharing the material loss. You DO NOT want to remove the material off only one side.

The Damper, Flywheel/Flexplate, Pressure Plate, etc. are individually spin balanced. Just like the wheels and tires on your car.

After you have completed this weight matching, you are now ready to mount the Crankshaft in a special Balancing Machine that spins the Crank with the Damper and Flywheel installed, as well as "Bobweights" that duplicate the compiled weight of the Pistons, Pins, Rods, Rings, Bearings, and a calculated "weight of oil". The crank is usually mounted in Teflon or Nylon "V-Blocks" on the Balancing Machine. The Balancing Machine measures "out-of-balance" through Computer-Controlled sensors. Just like the way your wheels are balanced when you have tires installed (or hopefully during normal maintenance as well), yet the engine balancing machine is much more accurate.

Any errors in the balance of the crank is corrected by either:

Drilling to remove weight
Welding to add weight
Machining and Adding "Heavy Metal" (Mallory Metal)
The Balancing Machine in many cases has a Milling Machine built on to it, making quick removal of material. The Milling occurs on the crank's counterbalances. If metal (weight) needs to be added, it in most cases is done within the existing balance holes in the crank. In other cases directly to surface of counterweights. In only extreme cases, typically with very lightweight design crankshafts, is Mallory Metal used.



http://www.centuryperformance.com/balancing.asp

i cant be bother argueing
just read it

v

[vvega]

Just a quick note these are AW11 pistons being used in a 20v Block with 20v crank. They where all machined the same @ speedtech NZ in wellington, they shud know there stuff as they built the 20v turbo DX corolla...

so they wieght the same as the 20v pistons then ???

just ask them and be sure dude
nothing worse than a avoidable error

v

[DOCILE]

What is Balancing?
After you have completed this weight matching, you are now ready to mount the Crankshaft in a special Balancing Machine that spins the Crank with the Damper and Flywheel installed, as well as "Bobweights" that duplicate the compiled weight of the Pistons, Pins, Rods, Rings, Bearings, and a calculated "weight of oil".

i cant be bother argueing
just read it

v

Bob weighting a crankshaft is not used for balancing an in line 4 cylinder engine. The nature of the engine ensures that the 4 pistons and rods are always acting in equal and opposite directions. This means that as long as the pistons and rods are weight matched to each other, it is irrelevant what their individual weights are, and this has NO impact on the balance of the crank and other reciprocating components!

Bob weighting is a technique used primarily for V configuration engines (V6, V8 etc).

I appreciate your serious concern in this matter, but you are wrong.

Also to further put your mind at rest, the AW11 pistons supplied to rollas22 are weight matched to less than 0.5 grams of imbalance, which is significantly better than the factory tolerance!

Andre
Speedtech Motorsport

[vvega]

sounds good then

wouldnt have hurt to see if the the crank was still in tune

hope it goes well

v

[DOCILE]

sounds good then

wouldnt have hurt to see if the the crank was still in tune

hope it goes well

v

You seem to have missed the point.

Unless during the time it took for us to modify rollas22's pistons, he 'accidentally' ground some material off the counterweights on his crank, the balance of the crankshaft will be identical to how it was before the pistons were modified!

No better, no worse!

Andre

[vvega]

i ment to itself and to the flywheeland pressureplate assembly
oh well