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Engine, Exhaust, Transmission Discuss the FR-S | 86 | BRZ engine, exhaust and drivetrain.


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Old 06-10-2019, 03:06 PM   #1
Levente
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Which Piper Cams?

Hi!


I am building a 500 whp GT86 and deciding between the Piper Stage 2 and Stage 3 cams. Does anyone have experience with either cams?

The engine is an Element Tuning 10.5:1 Big Valve FA20 block with a G25-660 0.92 AR turbo kit from JDL, revving to 9000rpm. Also with FMB's improved intake manifold.

The application is time attack partly and a daily as well. Yes, I know.

The goal is to have a good balance, have power from 3500 rpm, not a trash useless 2000 rpm like in a full race car. The turbo has the bigger AR to let the engine rev high.

Does anyone have experience with either cams? Counterspacegarage said the stage 3 is fine for this goal, but my tuner says the stage 3 will completely destroy low end - even though he never installed a Stage 3 cam on a FA20 but has Subie experience.

Thanks for the help!
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Old 06-10-2019, 04:30 PM   #2
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Do you think a 2L engine with the lowered compression and stage 3 cams is going to be able to spool up that turbo very early for any reasonable DDing?
Not an engine building expert by any means.
but for being able to DD wouldn't a little higher compression, like 12:1 with stage 2 cams be a better hybrid?
Higher compression with less boost can make pretty similar numbers now days to lower compression high boost. but have more off boost/low end power. From my understanding if you only have 91-93octane gas lowering compression can be beneficial but if you have E85/race gas/wmi your not as knock limited with the higher octane to need to lower compression so you can still run a good amount of boost with a good amount of timing make close to the same power, and have more low end and quicker spool. Just my 2 cents. For a dedicated track car though 10.5:1 and stage 3 would be fine.
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Old 06-10-2019, 05:53 PM   #3
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https://www.ft86club.com/forums/showthread.php?t=118465
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Old 06-11-2019, 12:21 PM   #4
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Quote:
Originally Posted by 86TOYO2k17 View Post
Do you think a 2L engine with the lowered compression and stage 3 cams is going to be able to spool up that turbo very early for any reasonable DDing?
Not an engine building expert by any means.
but for being able to DD wouldn't a little higher compression, like 12:1 with stage 2 cams be a better hybrid?
Higher compression with less boost can make pretty similar numbers now days to lower compression high boost. but have more off boost/low end power. From my understanding if you only have 91-93octane gas lowering compression can be beneficial but if you have E85/race gas/wmi your not as knock limited with the higher octane to need to lower compression so you can still run a good amount of boost with a good amount of timing make close to the same power, and have more low end and quicker spool. Just my 2 cents. For a dedicated track car though 10.5:1 and stage 3 would be fine.

No, I have no info about this that is why I am asking. There is mixed info out there.

I do not know whether 12:1 compression is safe on 91/93 + meth injection since we have no E85 in Hungary.

Have you tried a cammed GT86?
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Old 06-11-2019, 12:22 PM   #5
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I check this, not much valuable real life info unfortunately.
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Old 06-11-2019, 01:26 PM   #6
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Both will easily hit your power goal, but 3 will make you have easier power delivery 5000-8000, whereas the 2 will shift the meat to 3500-6000.

Pick the cam based on where you really want the power to be.

With a G25, low end power really isn't a concern, even street driving.
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Old 06-11-2019, 01:59 PM   #7
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No, I have no info about this that is why I am asking. There is mixed info out there.

I do not know whether 12:1 compression is safe on 91/93 + meth injection since we have no E85 in Hungary.

Have you tried a cammed GT86?
I would talk to your tuner and or engine builder to get their opinions.

But generally the old train of thought was lower compression to add more boost, but lowering compression requires more boost to make the same power. but generally more boost would more then make up for the lower compression.

In the last few years it seems more and more people have been seeing what can be done with higher compression engines. Newer methods, technologies, tools, both DI and PI etc... people are finding you can make very close to same hp with out lowering compression, and then have more off boost drive ability, quicker spool etc.

Dynos vary, but generally it takes 20psi with a turbo on stock compression with 93 octane to hit 400whp. 20 psi at 12.5 compression is the same effective compression as 26.5psi at 10.5 compression. Now you can probably make a little more power on the later especially on pump gas, but at a huge cost to off boost drive ability, and much slower/longer turbo spool/lag.

93+wmi is the in-between point from 93 to E85 and can help a lot.
IF only using 93 then maybe 10.5:1 comp isn't a terrible option, but 11:5:1 especially with WMI could be a good middle ground.
to get 500whp on pump gas alone with 10.5:1 compression you'll probably need close to 35psi of boost. with E85 and stock compression, probably around 25psi. 11.5:1 comp with 93+wmi maybe 30psi. again dynos vary a lot. this is just my speculation based on the research and other peoples findings and dyno posts.

and again your builder and or tuner should have a preferred preference for you specific goal.

Last edited by 86TOYO2k17; 06-11-2019 at 02:09 PM.
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