Is there a big difference between tuning for 110 over 93?

 

Does anyone have an opinion?

 

The process is the same, but the targets used on a modified engine for 93 vs. 110 can be a large difference.

 

Open ended question with zero detail. It's why you aren't getting much of a response. Describe specifically what you are asking about... engine, power goals, current fuel and tune description with timing levels, n20 jets... etc.

If you are leaving the tune the same and only upping a nitrous wet shot... There is no tune difference for the most part. But if your not at peak TQ timing on 93, you can likely add timing on 110. Then again depending on how much you spray...you'll end up pulling timing. So a lot of variables. If you aren't into detonation or seeing knock now.. and you don't plan on getting more aggressive with the tune... No reason to run more octane.

 

It mostly has to do with the amount of timing you can safely run. You can add a lot more advance without any ping on 110 than you can with 93.

If you tune it to 110 it will go boom when you put 93 in it. But for the most part the fuel cells and stuff will be the same, it not like the differences between an alcohol fuel and a petroleum fuel where the VE tables are vastly different. Very small differences there. But again, its the timing. Timing for a 110octane will blow up a 93 tuned engine in seconds.

Thats the long story short version.

 

Huh?

That's making a ton of assumptions that usually aren't true. #1 it assumes the engine is knock limited on 93 octane. Most are not. If you can run the engines peak torque timing on 93, putting 110 in it will not require anymore timing advance. Nor will it make more power with additional timing. So to say it will explode with a 110 tune can be a pretty inaccurate statement. In fact if you aren't spark limited on 93 there's no reason to run 110 as it will just hurt performance. When power adders come into play its a different story. But again, it all depends on the setup.

 

As stated above, yes you could theoretically get a little more power, maybe, but spark works off of something called MBT. This is the theoretical spark limit, and any more advance will show no gains. The idea is to fire the spark early enough, based on airmass amount, and fuel type, to complete the burn at about 15* ATDC, regardless. This is the “sweet spot” as they would say. More air will accelerate the process, and therefore require less timing. This is also due to the increased amount of dynamic compression during this period.

What octane essentially boils down to is a compression limit of the fuel type. Because we are squeezing the crap out of the air that goes into an engine, 10 fold normally, the more compression we add the closer we get to the knock limit of the fuel. Spark, adds to the compression, basically, because as we light the fuel, it begins to expand, while the piston is still traveling upward. Do this too early and you will exceed the compression limit of the fuel type and potentially hit unsafe cylinder pressures. Do it too late and it will not completely the burn at 15* ATDC and you will lose he energy created from the expansion, as the piston will move back down whether you light it or not because of rotational inertia. That part of the advance table will be gutless.

So, now we know a little more about octane, what it translates to is more timing won’t exactly help you, in most cases, because you may be advanced too far and missing the MBT and making the engine work against itself. This would be too much advance where the burn completes prior to 10* ATDC. Think of the expansion as a “spring” if you will, where again, that sweet spot is 15* ATDC. Advancing makes the spring longer and retarding makes it shorter.

Octane rating is the stability of a fuel to withstand these excess pressures. The more the better. Now if you want to actually take advantage of octane, you have to increase the compression of the engine, be it through a static increase, advancing the cam, or adding on those neat little air compressors we call blowers.

Moral of the story is, you need to make mechanical changes to see gains, not just “advancing” it in the tune. Now, with newer tech out, it is possible to change dynamic and effective compression with the camshaft. So in this case, maybe you could make some gains by advancing the cam, but this is debatable as to whether you could enough to require 110 octane. Nothing is free, any gain made in one place will mean you are losing something else, in this case, exhaust evacuation with an over advanced cam. So there are limits to that too.

 

That's not at all what I meant. If you tune for 110 and then put 93 in the tank you're going to have a had time. Putting in higher octane than what you tuned for does nothing. If you can get peak torque off 93 then you're right adding timing with 110 will no nothing but that is why i said my explanation was a really long story short because no one wants to sit here and write the literal pages it would take to explain all the differences between different engines and different setups that might work on and the ones it might not.....its just a can of worms.

The topics question is pretty open ended. Whats the difference between 110 and 93? Well, the short answer is...a lot. Of course I'm going to make assumptions on a question like that on a car forum. You basically have to to narrow that open of a question down to something you can answer quickly. When this question comes up from time to time I've usually had it framed from the perspective of someone wondering what putting premium pump gas into a race engine will do because they either can't find the 110 here or don't know better and bought something tuned for 110 which often is a snowmobile here. The turbo ones can't use any available pump gas once you tune them past factory.

So my advice is don't do it and that putting 93 in their 110 tuned engine is going to ruin their day. It's pretty sound advice I think.

 

I run 93 on the street and 110 leaded on the strip even with a stock ls6 long block i was able to add 5* to the entire high octane spark table. The engine responds nicely to it. I think its worth a tenth or two over 93.

 

Also matters if your comparing 110 race and 93 race or 100Race and 93 street. Street fuel has VOC stabilizers in it to aid in emissions management, race gas is kinda the opposite. Simple visual demo, spill a teaspoon of street fuel on a sidewalk and a teaspoon of race fuel,, on a warm day the race gas is gone is gone seconds.. I've tuned a tidy bump in HP just by switching from street 93 to Sunoco 93 race spec.. (Especially apparent in carburated engines. ) YMMV