E85 is it best to run a new engine in on 98?

I've been told to run new built engines in on 98 and not e85! I actually think e85 would be better. If it is better too run a new engine in on 98 pump what are the benefits. Thanks

It is better to run the engine using what ignition timing has been tuned for unless it has flexfuel...

Yes but if engine has has upgrades like forged bottom end and supercharger. And the engine is going to be running on e85 only why tune it for pump 98?. E85 is safer fuel why do people tune on 98 pump first after rebuilt engine?

It is not only about fuel but about ignition timing settings - it has to be spot on for particular type of fuel to create cylinder pressure at the right time through the cycle. And the ignition timing for e85 is different to ignition timing for pump gas as the flame propagation speed is quite different so the pick pressure in the combustion chamber will come at different pistion position. So if you will ignite your fuel mixture too late during the cycle, not only you won't make any additional power but you also overheating the exhaust valves which is absolutely not necessary.

The bottom line is that you should use the type of fuel your ignition timing is tuned for or use the flexfuel system which will automatically interpolate between ignition timing tables for e85 and pump gas and calculate the best values for best performance. It has to be educated approach rather than just thinking that one fuel is better than the other.

BTW - e85 will require much bigger injectors, of course e85 compatible...

Most E85 Tunes are actually built for flex fuel, and can run anywhere between E0 and E85, so we tend to do the initial tune (and break-in) on E0 fuel, then use E85 as the secondary fuel. The ECU will make the necessary fuel pulse width and ignition timing changes based on he ethanol content.

So even if planning to only run E85, you want to tune so that if some less than E85 fuel is present everything is safe.

Perfect thank you. What is the reason why not too tune on e85 first. Does 98 make the rings bend in better?

To me it absolutely doesn't matter what type of fuel is used first as long as fuel injection and ignition timing settings are correct. There might be a question about cylinder wall lubrication untill the rings are broken in properly since spirit dissolves oil but i do not think it is too much of an issue..

That makes sense to me as well mate. That's why I want some facts why not too tune on e85 first up. Thank you