I run a 31 degree advance on 87 gas in my GTUs, which is my track car. No sign of detonation yet. I had already posted a thread on this in the 2nd gen section awhile ago. There is no need to use anything more than 87 on a 13B-DEI motor. Only the 13B-MSP requires 91 as the ECU will auto-retard the timing if it detects lower than 91 fuel. (I'm at between 26 and 27 degrees BTDC)

To be in Top Tier, all your gas levels (reg, plus, super) must meet the minimum detergent requirements. That's why I only put Shell in my tank since that's the only Top Tier gas manufacturer on the east coast. The only other gas I would consider putting in, is BP/Amoco Ultimate, since their ultimate is comparable to Shell's V-Power.

On the west coast and all else, there's plenty of companies that I would use, Chevron, Conoco, Phillips, 76, Texaco, just to name a few. I also only use Techron fuel injector cleaner from Chevron as it's the only one that I've heard that works efficiently.

Is the boost any higher due to the ported wastegate via other mods, like exhaust? If not, and the boost is still stock, running 87 is all you need.

 

How much more boost would you need to run before you need to jump up to the next octane level? 8lbs? 10?

I know a guy w/o a ported wastegate and free flowing exhaust running 87 still, and he doesn't seem to show any signs of predetonation. I'd guess he gets up to around 10psi or so.

 

Ref:
http://www.toptiergas.com/deposit_control.html
"The deposit control performance of unleaded gasoline conforming to section 1 of this document shall be met at the retail level in all grades of gasoline sold by a fuel company in all marketing areas of a selected nation."

All grades of gasoline in the U.S. must meet EPA detergent standards, and all grades of gasoline must meet Top Tier standards in order for the retailer to gain Top Tier status. Sometimes a given retailer's premium grade may have more detergents and additives than their lower octane grades, but it does not mean that their lower octane grades are bad for your car. Many retailers use the same detergents and additives in all of their fuel grades.

 

Yes I do not have it and it was german anyway...
https://www.rx7club.com/2nd-generation-specific-1986-1992-17/ks-vs-gasoline-678353/
Here I only have 90 and 93, I use 90 for now on a S4 TII stock but a full RB exhaust.

 

So a stock s4 TII can run 87 fine, no problems?

 

Yes.

 

To gain the most performance on a boosted engine (turboed or SC) you would advance the timing and run higher octane fuel...I have an N/A s4 which I haven't even driven yet but id probably put 87 in it due to the fact that higher octane fuels burn slower yes, I have no idea how to advance timing on a rotary and because higher octane fuels (some of them) have additives that build up on the rotor faces...I know this because it builds up all over the valves faces and behind the valves in piston motors. And it only makes sense that in a rotary you would have to burn the fuel as quick as possible because you have 2 more power cycles than a piston motor.

Oh and for my stock car we run sunoco ultra 94 mixed with 104 octane leaded airplane fuel...yes its against the rules but lead cools the inside of the motor...but its disgusting for emissions.

 

Okay. But I guess what I'm getting at is that all 3 octanes have this additive package. This doesn't make one octane 'better' than any of the others. Like how everyone thinks that 93 octane is 'better' in their cars than 87 octane.


I think I'm missing something here....

 

The important thing to understand is that the octane rating is only an anti-knock rating. The detergent level and energy content of high octane fuel may or may not be better than other grades or brands, depending on how the oil company decides to make the fuel. You need to get statistics from each retailer if you really want to compare fuels, as the octane rating is only one of many factors.

 

I wasn't referring to the octane rating between different fuels, I was merely trying to make the point that some retailers have cleaner fuel for the fuel system than others, and those are the retailers that I usually fill up at.

The risk of detonation is much much much higher in a boosted engine than an NA engine. That's why usually, to make the most power, tuners would rather retard timing and run higher boost, than advance timing to make the same power at lower psi. This risk also contributes to the fact that all good tuners strongly recommend using the highest octane level available in your car at all times, if you're going to be pushing serious power on a boosted engine.

On an NA, the risk is much lower, and by my own example, 87 works fine with no drawbacks that I've seen so far with a heavily advanced motor. Rotaries don't make any more power if you advance the timing past 27 degrees BTDC.

 

You can run a little more timming. however i doubt you will yeild more power with the slower burning fuel + a little more timming vs the faster burning fuel and stock timming

I ran 87 in my n/a its entire short n/a life and beat the hell out of it. ran great.

 

Like I said, no reason to use 93 octane if you want to advance the timing. I've maxed out any timing gains and it runs fine on 87.

 

Yes. But I souced one and I downloaded the FSM.

 

my TII came with an owner's manual ^_^ its going to be fairly stock so i'll be sticking with 87-89