Stock FA20 Limits
 

I know I know, this has been asked about a million times but a lot of people have different answers.

Im planing on running a turbo kit (still deciding which one) how much psi can this stock engine hold with premium 91 (I’ll upgrade the injectors of course). I dont daily drive the car but I do drive it a lot on the weekend. :popcorn:

https://media1.giphy.com/media/12aW6JtfvUdcdO/giphy.gif

How much psi can a stock fa20 handle on 91 swamp water gas.... paging @ @ and @ I look forward to this trolling thread.


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I think its about 300 - 350 horsepower before you have issues like cooking connecting rods or shredding 4th gear.

A lot of turbo kits use an appropriately sized turbo for the car and run 7 psi. But if you want to push it, for science, I've read about plenty of people running higher boost on stock internals.

https://www.youtube.com/watch?v=VE9JhiUupY4

It depends on what you want to believe. Most people here will tell you the truth; adding boost at all puts the rods on a timer.

But if you choose to cherry pick what you want to believe, 25 psi is safe and your transmission won't shred gears and your axles will hold

So lets say I wanna run it “safe” at 7-8 psi and then later on buy a built block and turn the boost up. What kit would you recommend

dude .. you can run 26 psi and rape these engines all day... lol


(I had a friend tell me that, couldn't believe he wanted me to take that seriously.. 10 psi on petrol is about the sweet spot but that is going to fluctuate slightly with tune and kit. max 350-360 fly hp)


As someone that's had this debate you are probably debating whether you need the beefier turbo. If so, well. Need 400 or more hp with E85? got ways to manage heat? Is primarily track or at all? Daily drivability an issue? Personally without beefing up the block going anywhere over 360 and near 400 .. total crap shoot how long the rods and head gasket will take it.

Torque breaks rods. Torque from lugging a motor breaks it faster. Torque at low rpms break rods more than at high rpms. Detonation breaks rods more than torque, and the limits of 91 will be reached in order to avoid detonation before the limits of the rods from torque.

For superchargers, most don’t go over 12 psi with 91, and the motor isn’t exactly loving that much boost on 91. For turbos, since torque comes on earlier, unless you do progressive boost, it might be best to limit boost to 8psi.

[QUOTE=Irace86.2.0;3342224]91 will be reached in order to avoid detonation before the limits of the rods from torque. [\QUOTE]


yeah left that little limiting nugget out..

So im just gonna run it at 8 psi, I drive it a lot on the weekends and when I get time off I go to meets the whole time off so if I ever wanna boost more I’ll just get a built engine. Any kit you guys recommend?

I had the same question as you. And decided to go with JRSC three years ago. JRSC would be my decision again today after 35K miles. Initially, I was thinking about a getting a built block and increasing the boost. But the car drives so nice now, I will not touch anything.

Car feels very much normal for daily driving, But downshifting and revving above 3000 rpm starts rapidly increasing the power up to red line. That is so much fun. I think it is safer for the engine that I am not stressing the engine at low rpm.

One negative point (maybe not): Since there is no plateau of the power curve, the upshift especially at 1st and 2nd should be timed carefully before the rev limiter engages. I wish I had a bit higher red line with this kit.

So if you are rev-happy driver, you would be happy with JRSC. If you want to just accelerate at any gear, get Edelbrock or turbo.

It sounds like you're just looking for the answer you want to hear.

You won't find it here.

Neither exhaust diameter, nor kit choice, is REALLY influenced by your parameters.

Your fuel choice puts a hard limit on your power.

Any good kit is fine.


If you are limited to 91 octane then when you build the motor you will want to plan on dropping compression to avoid knock. Probably something around 10.0:1 or less depending on your power goals.

7 psi is different on different turbos.

It's about torque.

I've been running a centrifugal supercharger on E85 at 13psi max boost for over a 1000 miles now. My tuner was happy with all the levels, and honestly it all depends how you drive it.

Mt BRZ makes 340hp at the crank, 310 to the wheels. Torque is 222 ftlb.