If my Magnuson 2650 equipped LT4 was/is tuned for maximum output with E85 and I don't have access to it, I was told it would be safe to operate on 93 octane pump gas as long as I didn't get into the boost. If 108/110 octane race gas, would it need to be tuned all over again to utilize all the boost available?

 

In regard to E85/93 octane question: if you’re running E85 you undoubtedly have a flex fuel sensor. That will let your engine know if you’re running ethanol or not, and if you are, how much E you’re actually running. It will scale timing up the more E you run. If it senses little to no E (like 93 octane) it will pull timing automatically. If your car is setup with aggressive pulleys for racing, you won’t want to run boost (unless you get a Smoothboost control where you can turn down max boost or put on a milder pulley combo).

Race gas is a different animal altogether. It requires a completely different tune vs E85 or pump gas. You will need to run a dedicated race gas tune anytime you want to run race gas. If you run 93 octane on the race gas tune you’ll stand a very good chance of nuking your engine. E85 is much safer than race gas because the flex sensor will let the ECM pull timing and protect your motor. The race gas tune won’t do that and bad things will happen on 93 octane…

My advice is to get the Smoothboost. You can leave max pulleys on all the time and simply turn down the boost controller if you want to run 93 octane. When you go to the track and dump in E85, simply dial the boost back up. Easy peasy. I’ve been running Smoothboost for years and will not own a blower without it.

 

Been running 100 octane tune with 2650 @13# initially and now 15# boost (700/685whp). A8 running 10.3 @136 mph on unprepped track during 80-100* days....for 4 years now. Plenty of fuel pressure but had to take timing out from 6000-6500 rpms due to the 100 octane limit. I may consider adding E85 or meth soon so more timing can be added. Car runs great though...buy 100 octane at the pump and don't have to be concerned with meth pump leaks in my car like I had with another car I owned.

 

Yeah 100 octane is decent but there’s definitely more power to be had by going E85 on that combo. It’s preferable to meth as the distribution is much more balanced than a typical single/dual meth nozzle setup. Plus with the flex fuel sensor your cars tune can automatically add timing depending on E content. 2 or 3 degrees of timing can be worth 40-50 WHP or more on your setup. When I was making less power (~900 WHP) I gained nearly 80 WHP going from 93 to just E55 FYI.