Hi everyone, I just bought a set of new red top pistons (+0.5mm). Does anyone know how much horsepower the OEM pistons can handle? I have searched and searched and don’t know what the limit is.

I did purchase some amazing connecting rods from MRP so I feel good on those, but just wondering on the pistons. Thanks!

NA, I can't see you getting close to their limits - knowing your relatively mild build plan. (RPM/compression/fuel choice)

Assuming you tried to push a motor to 14:1+ compression and run methanol is another question - I assume that's what it would take to flat out tensile strength kill an oem Toyota piston without boost/nitrous/extreme timing/rpm/hydrolock/shite tuning decisions.

You have a lot of safety factor built in. Especially following OST's recommendations for oil flow, cooling, and capacity.

Bit like throwing rods and pistons at a 2jzgte when your end goal is 500whp.

Nick94tt wrote:NA, I can't see you getting close to their limits - knowing your relatively mild build plan. (RPM/compression/fuel choice)

Assuming you tried to push a motor to 14:1+ compression and run methanol is another question - I assume that's what it would take to flat out tensile strength kill an oem Toyota piston without boost/nitrous/extreme timing/rpm/hydrolock/shite tuning decisions.

You have a lot of safety factor built in. Especially following OST's recommendations for oil flow, cooling, and capacity.

Bit like throwing rods and pistons at a 2jzgte when your end goal is 500whp.

I get that. I guess it’s just comforting to know that, if for example, the red top pistons max horsepower is 300, then clearly I am fine. Versus if it’s max is 200 horsepower, then I need to be careful especially in the future if I decide to change it up and do something else.

It's more of an issue of what they can/can't do ultimately. Go boosted aiming for 300-400+, and you'll want some GZE pistons or more appropriate forged slugs.

NA, you're not applying all that much more stress unless you up the velocities (lengths, angles, speeds) or rpm.

It'd be interesting to see if it were physically possible to get them to/past 300 na - you'd need a ton of compression, timing, alcohol, and a cot in the corner of a well equipped machine shop...

Changes in the future will dictate the next setup, but you'll already have a solid long block - probably just need different pistons and head gasket depending on the level of silliness desired.

Oh ok, got it. The only thing in the future I would want to do is probably turbo (but this is years away.) so I would assume just pistons and a refresh of gaskets would all I need (plus the turbo kit, etc).

My ITB Kit already is coming with new injectors, fuel pressure regulator, the Link G4+ ecu, and more so I should be good from those things.

This is where I landed with all of my parts (I have been doing way more than this, but these are some main things).

Toda 264 cams

Toda valve springs

Toda Cam Gears

Toda Timing Belt

81.5mm hi comp pistons (10.3:1 compression)

MRP 4age Conrods Early Type 40/20

Big Port AE86 Engine Gasket Kit (incl are the stem seals)

TRD 4age 16v 0.8mm Head Gasket

MRP 4age 16v +0.5mm OS Valves

4age ACL Race Bearing Set STD Size

MRP Main Reinforcement Caps

4age ARP Main Stud Kit

ARP 4age 16v Head Stud Kit

MRP 4age 16v 200mm AE86 Light Weight Flywheel

ARP Flywheel Bolts 4age

MRP AT Power Billet Throttle Body Kit - AE86 Big Port, AE86 cable bracket + Mod (the mod here is for modifying the throttle cable ball)

MRP 4age 16v COP Conversion Kit - 1NZ Bosch Coils

Turbosmart FPR800 Black with Gauge

Xspurt Injectors 550cc (Qty 4)

Link G4+ Atom, 1/8" NPT Air Temp Sensor, 1/8" BSP Water Temp Sensor

AE86 Full RHD Loom suit COPs

Pipercorss Filter Box 80mm Suit AT Power Throttles

All that and I'm sitting here procrastinating on a stock head refresh with a mild port job.

Nick94tt wrote:All that and I'm sitting here procrastinating on a stock head refresh with a mild port job.

I did my port job as well!

On a related note. For "3rd party" cast pistons, which don't already have a coating (whatever it is that was done on OEM 10.3:1 pistons), would having the domes ceramic coated help when pushing for higher-than-stock HP? I'm guessing it at least helps with heat dispersion and so prevents hot spots from forming on the domes.

Asking because I've considered sending out my 3rd party (non-Toyota) 10.3:1 cast pistons to get their domes & skirts coated. Coated domes for what I mentioned above, skirts for reducing friction. I was considering a small turbo and pushing for sub-300 HP numbers using those pistons.

There isn't a horsepower limit... there is a tuning limit. There is a "flaw" with all the n/a pistons for the 4AGE... the 2nd compression ring rests on ring land that is not well supported (piston on right in photo)





It works fine as long as you avoid detonation... detonation tends to break the ring land... causing issues.

Rogue-AE95 wrote:On a related note. For "3rd party" cast pistons, which don't already have a coating (whatever it is that was done on OEM 10.3:1 pistons), would having the domes ceramic coated help when pushing for higher-than-stock HP? I'm guessing it at least helps with heat dispersion and so prevents hot spots from forming on the domes.

Asking because I've considered sending out my 3rd party (non-Toyota) 10.3:1 cast pistons to get their domes & skirts coated. Coated domes for what I mentioned above, skirts for reducing friction. I was considering a small turbo and pushing for sub-300 HP numbers using those pistons.

I've used similar 3rd party pistons in n/a builds... not sure of their ability to hold up to boost... partly because of my answer above.....

Thanks. Yes my pistons have that unfortunate slot design. That combined with being cast vs forged makes me leery of them, but as I said, I wouldn't try pushing them too much anyway. And I'd be paying someone for tuning, who hopefully knows what they're doing.

with turbo and e85, 300hp +