Euro 3.2 + turbo : can I get away with 8 psi of boost?

kamaro · 12-13-2021, 01:51 AM

I have been driving my turbo'ed Euro 3.2 for a while now with a 3.5 psi spring in the wg but now I feel bored with that level! .. so I'm thinking of rising the bar a bit more, I have an EFI via a Microsquirt and I'm doing the tuning myself, I wonder if I can get it to ~ 8 psi safely? .. I'm using a 91 fuel right now which is the highest octane in my area, but I can add a bottle of Torco to rise the octane if necessary, would like to hear from you guys about that, would I be "tickling the dragon's tail" by doing that with a 10.3 CR engine?

slow&rusty · 12-13-2021, 04:14 AM

Take out the guess work and install a wideband to really know how lean the engine runs at the higher boost.

Dr J · 12-13-2021, 04:23 AM

Do you have knock sensors? Do you have an intercooler? What are your air intake temps on boost? The key is to avoid detonation (knock).

pkabush · 12-13-2021, 09:07 AM

Quote:

Originally Posted by slow&rusty

Take out the guess work and install a wideband to really know how lean the engine runs at the higher boost.

Agreed. If you don’t have a AFR meter your guessing and hoping. Especially with your CR. I’d seriously consider a J&S safeguard as well.

12-13-2021, 09:53 AM

Agreed, Air/fuel sensor/gauge air intake temp sensor/gauge. With boost comes great responsibility...to your engine. Following to see how the extra boost hits

kamaro · 01:00 PM

I've got both a WB gauge and a knock sensor installed, my current AFR is around mid to high 10s at WOT. also I have a full bay IC with decent IAT (I saw a maximum of 90*F after muliple WOTs back to back).

Rodsrsr · Rodsrsr's Garage

@ 10.3 compression I wouldn't mess with it. I'm running a US spec 3.2 and only run .5 bar spring which is a solid 7 psi. You also have to think about the gearbox, not sure f your running a G50 or 915.

Mr. Merk · 12-14-2021, 07:57 AM

What kind of power are you guys making?

Rodsrsr · Rodsrsr's Garage

I haven't Dyno'ed it yet, but its a fresh 3.2, (new rings, bearings, arps, valve job, 20/21 web cams, enlarged throttle body, headers with outlaw). I'm guessing it'll fall in the 400ish range. No need to go hunting for more power until I upgrade the gearbox.

Its surprisingly well balanced in its current configuration.

matthepcat · matthepcat's Garage

The problem with high compression turbo is also the fact that your pistons are for NA, meaning the rings are higher up on the piston. There is less "room" for detonation resistance as it is.

I melted the ring lands on my stock US SC motor with a turbo under boost in what felt like 4 seconds of uphill load boost in cold weather.

I bet you could run 5 lbs and be ok with enough octane and fuel enrichment, but you will not get that magical turbo shove that comes from running 15lbs with proper internals, ignition & knock sensor control.

quattrorunner · quattrorunner's Garage

I don't even think it matters that the afr is safe, 10.1/1 is high and I'd be more concerned with ignition and boost. 8psi is just a bit high for that compression. Add meth or lower it to 5-7psi. These are not civics or ls v8's.
I definitely understand the temptation tho. You're stung by boost addiction for sure.

kamaro · 12-14-2021, 11:53 PM

After hearing from you guys, I think I will just let it as is and don't risk it. I will start saving some $$$ for a low compression Mahle 3.4 top end. Since I already run EFI and have a 930 transaxle, going to 3.4 low compression would be the natural next step. Only if its not that expensive to build!

quattrorunner · quattrorunner's Garage

And you're using a 930 gearbox which almost requires more hp to enjoy it. I miss my 915 and more spirited days. when you get to over 400hp things start to get serious.

Jeff Alton · 12-15-2021, 09:24 PM

The Euro 3.2 we did a turbo conversion we did, we replaced the pistons with 8.5CR to deal with 1.0 bar. The North American version 3.2 we turbo converted we will run at .7 bar but with programable ECU and dyno tune for best performance.

For what that is worth...

Cheers

mikedsilva · 01-14-2022, 11:36 PM

Quote:

Originally Posted by kamaro

After hearing from you guys, I think I will just let it as is and don't risk it. I will start saving some $$$ for a low compression Mahle 3.4 top end. Since I already run EFI and have a 930 transaxle, going to 3.4 low compression would be the natural next step. Only if its not that expensive to build!

Keep in mind, that the 10.3 that porsche quote, actually cc's to a lower number. I cc'd a set of euro 10.3:1 pistons and got an accurate 9.8:1.
I think the general consensus is that the porsche quoted numbers are with a zero deck height.. there are threads around PP suggesting this.

It sounds to me like you could do it but just go gently

onboost · 01-15-2022, 08:10 AM

Quote:

Originally Posted by Rodsrsr

@ 10.3 compression I wouldn't mess with it. I'm running a US spec 3.2 and only run .5 bar spring which is a solid 7 psi. You also have to think about the gearbox, not sure f your running a G50 or 915.

Quote:

Originally Posted by Jeff Alton

The Euro 3.2 we did a turbo conversion we did, we replaced the pistons with 8.5CR to deal with 1.0 bar. The North American version 3.2 we turbo converted we will run at .7 bar but with programable ECU and dyno tune for best performance.

For what that is worth...

Cheers

Quote:

Originally Posted by mikedsilva

Keep in mind, that the 10.3 that porsche quote, actually cc's to a lower number. I cc'd a set of euro 10.3:1 pistons and got an accurate 9.8:1.
It sounds to me like you could do it but just go gently

10.3:1, 9.8:1 with the kinda boost you're looking to run she ain't gonna last long, and you'll be thinking about more than a gear box.. question is which will go first?

Typically the sweet spot is 8.0:1 -8.5:1 and 1bar as Jeff stated.

kamaro · 01-15-2022, 08:14 AM

I heard that these engines are pretty much knock proof, I don't know how far that can be, but that what encourages me to rise the bar a bit at a time. And I'm fully equipped to get into the battle with a dedicated AFR gauge, boost cut tuned into the ECU,and a knock sensor.

mikedsilva · 01-15-2022, 10:33 AM

Quote:

Originally Posted by kamaro

I heard that these engines are pretty much knock proof, I don't know how far that can be, but that what encourages me to rise the bar a bit at a time. And I'm fully equipped to get into the battle with a dedicated AFR gauge, boost cut tuned into the ECU,and a knock sensor.

I've only had experience with normally aspirated, and they are definately not knock proof.