From knowing nothing to having a Thunderbird supercharger on an m20b27i

[Victell]

Read this, you need to run 91.
http://www.superchargersonline.com/i...age=page&id=47
http://www.superchargersonline.com/i...age=page&id=46

The conclusion you're getting from those links is that you cannot run 87 octane in a boosted application, which isnt true. It explains how octane relates to power. You can run boost and choose any octane you want. You just have to tune for it and understand how it dictates your timing (and power) limits.

Higher octane will allow higher power. Some are willing to pay for race gas, others might want to run 87. Either way needs a corresponding tune.

[FLG]

The conclusion you're getting from those links is that you cannot run 87 octane in a boosted application, which isnt true. It explains how octane relates to power. You can run boost and choose any octane you want. You just have to tune for it and understand how it dictates your timing (and power) limits.

Higher octane will allow higher power. Some are willing to pay for race gas, others might want to run 87. Either way needs a corresponding tune.

I don't think anyone is doubting it can be done... But in this case (or any really) it's not a matter of power, it's a matter of safety.

The only way I'd run a lower octane is if that's the only one available. Like I wouldn't go buy 100 octane race fuel and tune on that because I can't get it drivinf around. 93 is avail mostly everywhere.

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[Ether-D]

Well, my first tune is gonna be pretty conservative and I don't even know how much fuel I have in the car currently. It's not going anywhere so it may have to be tuned on 87...

[TheTacoMan]

Why is this such an issue, the difference of price between 87-91 isnt that much for a little more peace of mind in having a longer lasting engine and avoiding detonation?
87+ meth may be doable but I personally wouldnt do it. Spending all this time building a FI setup and then running shitty gas does not make sense to me.

[Victell]

I don't think anyone is doubting it can be done... But in this case (or any really) it's not a matter of power, it's a matter of safety.

The only way I'd run a lower octane is if that's the only one available. Like I wouldn't go buy 100 octane race fuel and tune on that because I can't get it drivinf around. 93 is avail mostly everywhere.

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I would say the "safety" has to do with how close your tune is to the point of preignition, not so much with the octane. If you tune for lower octane and stay far away from detonation with grossly retarded timing, then your octane/tune combo would then be "safe". Although you're really leaving a lot of power on the table by doing that. Personally I would run the highest octane possible to get the most from the setup. If I was rich I would run race fuel in my daily driver.

Originally you said "I was hoping I could tune it for regular" which is true, but some replies you indicated you CANT. As long as you understand that you CAN.

[Victell]

DO NOT learn how to tune on a supercharged engine using 87 octane fuel.

How come? I thought ignition tables would be different but Im not sure what else. What would be the difference in learning from different octanes? Other than wasting your time on a tune that you'll end up not using anyway.

[TheTacoMan]

[FLG]

I would say the "safety" has to do with how close your tune is to the point of preignition, not so much with the octane. If you tune for lower octane and stay far away from detonation with grossly retarded timing, then your octane/tune combo would then be "safe". Although you're really leaving a lot of power on the table by doing that. Personally I would run the highest octane possible to get the most from the setup. If I was rich I would run race fuel in my daily driver.

Originally you said "I was hoping I could tune it for regular" which is true, but some replies you indicated you CANT. As long as you understand that you CAN.

Yes you can but why would you? Honestly I feel this convo shouldn't even be here haha. Unless you only had 87 avail then we'll you have no choice, but you have a better grade fuel and I'd be running it. When I go to the track I even throw some 100 octane in my drift car and mix it with the 93 simply because I know air temps and engine temps are at their highest, I'd never risk my engine.

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[Ether-D]

Why is this such an issue, the difference of price between 87-91 isnt that much for a little more peace of mind in having a longer lasting engine and avoiding detonation?
87+ meth may be doable but I personally wouldnt do it. Spending all this time building a FI setup and then running shitty gas does not make sense to me.

I just have a regular gas station that is owned by a really nice local lady who really likes it when I fill up my cars there. She only has regular. I feel like it helps her. Her prices for non-ethanol regular are the same as premium in town. It has nothing to do with cost. I just like doing business with local folks.

So from what I gather, 87 can be run on a FI motor if the boost is relatively low and the timing is retarded enough to keep it from detonating, resulting in a loss of horsepower. Is this correct?

[TheTacoMan]

If you are hell bent on running 87, I would mix it with high octane gas or use meth or both.

[Ether-D]

I'm not really all that hell bent. I just have to separate the facts from the opinions. Sometimes, opinions come across as as facts. Hell, a lot of opinions are facts. But not all. I really appreciate you guys having my engine's back.

[The Dark Side of Will]

How come? I thought ignition tables would be different but Im not sure what else. What would be the difference in learning from different octanes? Other than wasting your time on a tune that you'll end up not using anyway.

Because as he learns, he'll make mistakes along the way. He needs some safety margin for that.

I would say the "safety" has to do with how close your tune is to the point of preignition, not so much with the octane. If you tune for lower octane and stay far away from detonation with grossly retarded timing, then your octane/tune combo would then be "safe". Although you're really leaving a lot of power on the table by doing that. Personally I would run the highest octane possible to get the most from the setup. If I was rich I would run race fuel in my daily driver.

Originally you said "I was hoping I could tune it for regular" which is true, but some replies you indicated you CANT. As long as you understand that you CAN.

Preignition and detonation are very different things. Preignition is instant death to an engine (e.g. holing a piston). Detonation is survivable... for a while. How long depends on how much boost the engine is running.

The "corners" of the map, like the situations to which I alluded earlier in which the engine or intercooler might be heat soaked, or other combinations of operating parameters which are rarely experienced--and thus difficult or unlikely to be correctly tuned--are going to be risky.

High coolant temps are especially bad... He'll need to be very familiar with and have very conservative settings in the ignition advance vs. coolant temp and mixture vs. coolant temp tables to make sure he doesn't pop the engine on the first hot day he drives it hard.

[The Dark Side of Will]

So from what I gather, 87 can be run on a FI motor if the boost is relatively low and the timing is retarded enough to keep it from detonating, resulting in a loss of horsepower. Is this correct?

Correct. Your boost is going to be pretty constant and determined by your pulley size.
So the way it will work is that you'd install a pulley for, say 5 psi and tune that on 93. Once you're comfortable with that, run your tank all the way down, fill up on 91 and drive/log/tune from there.
Then repeat for 89 and then 87.
If horsepower creep happens, pulley for 8 psi and repeat starting with 93.

Now... you *DO* have a knock detection system, right? Knock sensor on MS? J&S Safeguard or something similar?

[Ether-D]

I do not have any knock detection anything, but cept for my ears. Let's take it there. How do I go about getting my ms2 to listen for knock?

[Ether-D]

Meanwhile, I'll be getting my o2 sensor on Monday.

When it gets running, I know you guys are gonna want video. I have no idea how to put a video on the intertubes. Especially with this shit satellite internet. It really sucks so completely. But if you have an iPhone, I'll send you a vid that way I guess. I'm pretty technologically impaired.