Forged internals w/ Turbo mileage for daily use
 

Hi guys,
I have a forged internals (10.5:1 pistons, forged rods etc) turbo'd BRZ that now unfortunately is burning oil after 21,000 miles (or 35,000km). Leakdown showed a 22% leak in cylinder 3, other cylinders ranged from 8-15% but compression is 150-155psi all round. It is also has greyish smoke whenever I do a WARM start, but the car drives pretty normally otherwise.

I am potentially looking at rebuild options:

- going forged internals again (but I am scared that forged pistons has reduced the longevity of the motor)

- new OEM shortblock with forged conrods and running moderate power on E85

- or a used longblock (but they are going for 3-4k in Australia...)

Can anyone vouch for good longevity of forged motors? Or would going for a new OEM shortblock with forged conrods be the best way to ensure reliability for a daily?
Thx!

Look at an IAG shortblock

K-Swap and turbo

This is by far the best option.

Look up all the failure rates on built FA20's as well; so a built short block from IAG, or anywhere else for that matter, will most likely blow up as opposed to a stock, boosted (and properly tuned) K24.

Stock K24's get up to 400hp without a sweat and will be reliable all day long. Plenty of 500hp examples out there as well.

Also the most expensive option with a NA Kswap running $12k. A turbo added would easily crest $16k. It would be a great motor after getting it up and running for sure.

A new short block with forged conn rods will likely be just fine as it solves the biggest issue with boost on this engine. As much as I like E85 the lack of lubricity probably didn't help the longevity of your engine. A majority of blown FI FA20s where running E85 at the time. Maybe the added stress of the additional HP, maybe the added ring friction of E85 washing the cylinder walls. Who's to say.

Were these FI FA20s stock con rods? I haven't actually seen many forums of built FA20s or FA20s with forged conrods to have failures

From one of the very reputable UK tuners.

Many consider a forged engine to be "the silver bullet" that it fixes all problems, is infinitely reliable and will last forever. It could not be further from the truth, a forged engine needs to be treated with greater respect than the above package or a stock engine. It must be properly warmed up and cooled down, serviced and maintained far more regularly, taking on a forged engine is not something to take lightly, properly consider if it meets your needs or not.

You need to go back to stock pistons, new shortblock, Forged conrods and then boost.

Read this thoroughly.

https://www.fensport.co.uk/pages/for...e-build-prices


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Do you have a blueprint for the engine? Your more than likely going to have to tear her open to see what failed or is out of spec. Who built it? Are you sure it wasn't slapped together without tollerance checking?



Yes forged engines do have a tendancy to burn oil worse than oem. This is multiplied by bad break-in procedure too.

I don't know why so many people go with forged pistons...
 

Forged pistons expand and contract more than hyper pistons, this causes piston slap when the engine is cold and WILL reduce longevity.

Unless you're going for like 600 or more hp, non-hyper pistons shouldn't really be necessary. The short coming with the FA20 in the 86 is the rods. If you want a built motor that will last longer, get some forged rods, some good bearings (king), proper ring gap for the power level you want and use hypereutectic or even stock pistons and some good head studs.

The problem is when someone goes to the expense of a built engine they want growth for more power down the road and they end up over building it for that reason. Unfortunately, you WILL lose longevity with certain choices to give you that extra room for growth. If you're looking for 400-550whp, just use hyper pistons that won't expand and contract as much and you'll get more longevity out of your built motor.

Jaden

I would say stock rods for sure. People get greedy on E85 and a few months later running even higher boost they pop. But almost all acknowledge that they were playing with fire.

Thanks for the replies guys! Will get my mechanic to tear the motor apart and see what failed....