11.5 CR + boost, is it safe?

[shadowsong6]

I'm looking at the Livernois Big bore short block (10:1, or 11.5:1 CR options), and there in-lies the problem.

The end goal is to throw a Whipple on top of it (probably wouldn't see more than 18-20 psi max, but more than likely somewhere closer to the 12-15 psi range), but that will be a few years down the road, so it will be an NA motor for a long time, that makes me want to look at 11.5:1, but I don't know how safe that would be once the boost is added. I live in Texas, so our pump gas is 93 octane, not that 91 piss water. E85 is an option, but I'd prefer to have the ability to switch back and forth, and would probably be on pump more often than E85.

 

[Scott8583]

Your best bet is to ask Livernois that question. Anything less the then 11:1 on these little motors will kill low end. Granted you can make up for it with extra boost. If your planning on running pump gas, then 11.5 + boost is not for you. If you swap over to E85 there is no reason to ever switch back to pump, E85 is far superior! (Gas mileage is its only down fall)

I'm running 11.25:1 with 15 psi from a Roush 2.3 TVS and plan to eventually bump it to 18ish.

 

[the5]

Gonna be running an 11.5:1 Built motor soon on 93. My tuner says max on pump is about 10 PSI. After that race gas or E85 is necessary. E85 is much safer for your engine and you will make more power.

 

[Livernois Motorsports]

I'm looking at the Livernois Big bore short block (10:1, or 11.5:1 CR options), and there in-lies the problem.

The end goal is to throw a Whipple on top of it (probably wouldn't see more than 18-20 psi max, but more than likely somewhere closer to the 12-15 psi range), but that will be a few years down the road, so it will be an NA motor for a long time, that makes me want to look at 11.5:1, but I don't know how safe that would be once the boost is added. I live in Texas, so our pump gas is 93 octane, not that 91 piss water. E85 is an option, but I'd prefer to have the ability to switch back and forth, and would probably be on pump more often than E85.

As with almost all builds, this will depend greatly on your tuner. However, look at all of the 2015 guys running ~12#, and they are exactly the same 11.5:1 CR already. Now, anything above that, we start wanting to see things like methanol, E85, or race gas to play it safe. At 18-20# however, even the 10#1 would likely need those to help out as well. So, we might be able to play around a little bit on the CR, or there is always the option of a custom piston as well, but to us, 11.5:1 is fine for boost on these so long as the tune is correct.

 

[5lho]

Gotta drill down on that question.....

 

[shadowsong6]

Well, the reason I'd wanted to stay on pump, and not E85 is the car gets driven daily, sometimes quite a lot, depending on my workload that day, so the MPG loss of E85 made is a little less desirable, but hey, who am I to complain about mpg when I'm probably looking at 700+ rwhp lol

@livernois, the s550 cars are 11.5? I thought they were still 11?

 

[Scott8583]

The mileage is only a pain on long trips, when you have to know there's a station every 250 miles. E85 is like race gas right out of the pump for under 2 bucks a gallon. Priceless!

 

[Livernois Motorsports]

Well, the reason I'd wanted to stay on pump, and not E85 is the car gets driven daily, sometimes quite a lot, depending on my workload that day, so the MPG loss of E85 made is a little less desirable, but hey, who am I to complain about mpg when I'm probably looking at 700+ rwhp lol

@livernois, the s550 cars are 11.5? I thought they were still 11?

Sorry, should have clarified. I mean with our engines. We made the move to 11.5 instead of 11:1 on the 2015 piston first. Making it the default on our s550 builds.

 

[shadowsong6]

Sorry, should have clarified. I mean with our engines. We made the move to 11.5 instead of 11:1 on the 2015 piston first. Making it the default on our s550 builds.

Ahh, got ya, thank you for the clarification. 11.5 and 12# sounds like a winner in my book!