4G93 Forged Pistons

[scott.mohekey]

In the interests of seeing whether we can use forged 4G93 pistons in our 6A13s, I bought a single stock 4G93 piston and conrod from a guy on trademe.

I've attached 3 pictures comparing a stock 6A13TT piston and a 4G93T piston. The 6A13 is on the left.

It might be a bit hard to see in the pictures, but the diameter of the pistons is identical, the position and design of the ring lands etc are identical, and the size and position (relative to the top of the piston) of the pin are identical. The crowns are VERY similar. The skirts and the con rods are where the differences appear. The con rods are very similar in length, I THINK the center of the big end is in the same position relative to the piston, the big end on the 4G93 is about 2 to 4 mm smaller in diameter.


SO.. it looks like if we use forged 4G93 pistons with custom con rods, we should be sweet! When I get some time in the weekend I'll put the 4G93 piston on the 6A13 rod and put it back into the engine with the crankshaft and see how it rotates.

[Nutter_John]

errr have you check to see if you can find low compresion forged 4g93 pistons ??

[bradc]

So what Comp Ratio are those pistons?

[scott.mohekey]

Something like this: http://www.streetlevelperformance.co...20Pistons.aspx

[Gly]

errr have you check to see if you can find low compresion forged 4g93 pistons ??

lancer GSR, 1.8l turbo, 4g93t,

and yes these forged pistons are available here in NZ from various manufacturers

Piston set Mitsubishi 4G93T dohc 81.50mm bore 19mm pin 9:1
Custom made, Wisco $1256.52 Set (Incl Tax) (set of 4)


note compresson ratio is if fitted to a gsr motor,
depending on deck height/rod length this will vary.

[scott.mohekey]

The stroke comes into it as well, which is largely determined by the offset on the crank shaft, i THINK.

[scott.mohekey]

We can convert the compression ratio from one to the other easy enough, its just some simple mathematics to get a conversion factor.

[Goku]

Hey Scott.... I thought we was going to keep this hush hush lol

[Adam.Findlay]

Im definalty going to keep an eye on this thread im too scared to push any extra boost after my oil blockage caused my conrod to melt in half and powderisd a piston, forged is my way to go,

[Turbo_Steve]

Adam....if it's an oil blockage it would still be pretty catastrophic, regardless of whether the internals were forged or not.

[scott.mohekey]

Hey Scott.... I thought we was going to keep this hush hush lol

Ah yeah.. sorry about that.. I got excited.

[scott.mohekey]

Im definalty going to keep an eye on this thread im too scared to push any extra boost after my oil blockage caused my conrod to melt in half and powderisd a piston, forged is my way to go,

You were running stock turbos etc right? You shouldn't need forged internals until you start fitting bigger turbos/really pushing the hp. Sounds like you could benefit from some gauges. What oil were you running too?

[scott.mohekey]

So what Comp Ratio are those pistons?

The stock 4g93t pistons are 10:1, while the stock 6a13tt pistons are 8.5:1, so we can use a scaling factor of 8.5/10 to convert from 4g93 to 6a13 (correct me if I'm wrong here).

So, the forged pistons I linked to (8.5:1) would be 7.225:1 in the 6a13, and the ones Carsten mentioned (9.5:1) would be 8.075:1.

[Nutter_John]

whats the measurement for each one from the small to the deck height , also what size is the bore of the small end

[Nutter_John]

The stock 4g93t pistons are 10:1, while the stock 6a13tt pistons are 8.5:1, so we can use a scaling factor of 8.5/10 to convert from 4g93 to 6a13 (correct me if I'm wrong here).

So, the forged pistons I linked to (8.5:1) would be 7.225:1 in the 6a13, and the ones Carsten mentioned (9.5:1) would be 8.075:1.

where are these maths coming from as without the stroke lenght you can;t work out the compresion ratio

[scott.mohekey]

whats the measurement for each one from the small to the deck height , also what size is the bore of the small end

Is the first measurement from the top of the piston (deck) to the center of the pin? If so they're the same on both stock 4g93t and stock 6a13tt.

What are you referring to by the bore of the small end? The diameter of the pin?

[scott.mohekey]

where are these maths coming from as without the stroke lenght you can;t work out the compresion ratio

Yeah, I didn't think they'd be right. It was a rough guess really.

[Nutter_John]

yeah sorry small end is the pin diameter

and

the other measurement is top deck to pin hole ( eg to see how much metal is above the pin )

[scott.mohekey]

yeah sorry small end is the pin diameter

and

the other measurement is top deck to pin hole ( eg to see how much metal is above the pin )

Ok, pin diameter is 19mm on both. I haven't measured the the top deck to pin center yet, but it is the same on both (is this called deck height?).

[Nutter_John]

can you do a photo of the inside bottoms of the pistons , this should see how much internal mass is in each piston head