Hey guys roughly 2 years ago I built an EQ headed 408. I originally built it for nitrous but have yet to hit the button. It currently has 11.47:1 compression. I ran it on VP110, but my wallet didn't like it much. This summer I converted it over to run E85. I love it to be honest! It runs cooler, makes more power, and is street friendly. Question I have now though is would I be able to ditch the nitrous setup and go turbo? If so what psi would I be safe at? What would be a good turbo choice? I'm not really looking for all out performance, just something to run here and there on the street and track at times.

 

There is so much to an engine's knock resistance, static compression is only a part of it. Skill of the tuner is going to matter a lot more in the case of an engine like that.

Do you know the actual ethanol blend? In my neck E85 is actually E50, around 99 octane. It would be perfectly happy running in an engine like yours, but might be marginal under boost. If it is more like E70 or E80 you will have a much better chance.

I say turbo it, if you can't tune it to make good power without being knock prone worry about changing the compression ratio then.

 

I was also thinking of going with a Holley Sniper system as well. My buddy has a boosted VW and he's alot better with tuning e85 and EFI

 

Get the compression down to 9:1 or 10:1

As a professional tuner I get around 5k to setup and tune a vehicle, it is an arduous process with many details that typical tuners don't even consider and I've never had an engine failure.

I would not touch anything with 11:1 compression no matter what type of fuel because I know better. It isn't worth the trouble or hassle. High compression is the opposite of safety when it comes to performance w/ boost pressure. The lower the compression, the safer the engine and more power you can make with boost and reduced fuel quality with higher temperatures. If money was no consideration using E85 I would look at options such as 8:1 and we could squeeze 2k rwhp from the right engine using Alcohol for racing situations reliably, strictly for racing. To drive on the street a bit of compression is helpful for economy and low-midrange driving situations which are not racing but just normal and part throttle driving is a compromise which will reduce the total potential power and safety somewhat but that is tuning knowledge how far you can safely push an engine based on how it acts.

In general because I know it seems ambiguous I will give a general review
8.5:1 compression I have used 93 octane for up to 24psi and approx 2.5x factory engine output
8.5:1 compression with E85 I've used up to 4x output
9.5:1 compression on 93 octane gasoline I've used safely well intercooled setups on the street around 18psi max 2x output.
9.5:1 compression E85 you can easily 3x output figure 1000rwhp from an engine that originally puts down 350rwhp NA
10:1 with 93 if the engine is all aluminum like L33 5.3L 05-07 with VERY careful intercooling near-ambient temps I've successfully 2x output (around 650rwhp) approx 15psi of boost. But the IAT and piston temperature is critical and must be monitored carefully with safety features. I recommend WATER INJECTION at this level as a addl layer of security.
10:1 with E85 is no sweat 1000rwhp 3x output same as with 9.5:1 the alcohol does a great job keeping it cool. Still need quality intercooling and it MUST use minimum timing (reduced timing until the EGT almost spikes is minimum cylinder pressure, safest piston tuning). I've used 50% alcohol content here and noticed no difference between 50 to 75% E content. I would never depend on getting over 55% Alcohol so I do not consider it an option (I don't tune around 56%+ alcohol content being available).