From knowing nothing to having a Thunderbird supercharger on an m20b27i

[Ether-D]

So today I got back out there and fixed a few things that needed attention. I shortened the bitch tube (aka breather tube) by about 1/8" at each end with the bench grinder so I could install it without removing the intake manifold. This manifold was not fun to install and I wasn't about to do it again if I didn't have to. Also, on the first try I took off too much material from the top and ruined it, but I have plenty of spare stuff and had another. So now I have a removable bitch tube.

Then I got the brake booster vacuum hooked up nice. The Ford TB had the two small coolant tubes built in so I just hooked those right up to the existing m20 TB heater hoses.

I'm trying to talk myself into ordering the o2 sensor even though I can't really afford it. Well I can, I just don't usually let the nest egg get below a certain amount. So, that's really all that's standing between me and tangible completeness. Then all the tuning.

So I reckon I'll have to start running high test. Is that required? I usually get my gas at a place that only sells non-ethanol regular. Is it just a maximum performance thing or required if you want your engine to not blow up?

[The Dark Side of Will]

Run the highest octane you can get all the time.

OE calibrations have multiple timing tables and can "test" fuel octane by advancing the timing at idle until they detect knock, and correlating the amount of timing required to fuel octane.

I've never heard of Megasquirt being able to do that.

[Ether-D]

I was hoping I could tune it for regular. Then keep getting my gas there. I wouldn't switch back and forth, I would just always get it there. There are plenty of gas station options, I just like to get it at this one because I like the lady who owns it.

[FLG]

Sorry to tell ya but regular gas and performance don't mix. You need to use highest octane you could readily/easily find.. Assuming it's the usual 93

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[Ether-D]

Right. But, If it were possible, I would like to tune it for low octane at the expense of some horses.

So are you guys saying it's just not possible, or it's not optimal? Because I really don't need to squeeze every single horse out of this. It's just a DD. Though, I am a fan of efficiency and would totally be into 93 if it was inefficient to run regular.

I just really like to get my gas at this little country store and I feel like she counts on my 2 tanks a week…

Thanks for your feedbacks. I'm not arguing, I'm just trying to decipher preference from all out facts.

[FLG]

Well its possible but highly would not recommend . Your going to be fighting detonation and risk destroying your build.

You need to run high octane fuel. Sorry.

Just ask the girl out already, though might cost you more then 2 tanks a week. Haha
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[Ether-D]

Well its possible but highly would not recommend . Your going to be fighting detonation and risk destroying your build.
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Alright… Thanks for your expertise.

[Ether-D]

BTDubz, I let all of the silicone dry nicely and went out there to start it without the belt and that bitch fired right up and idled relatively nicely. A little miss here or there, but pretty good for a big ole contraption I made in a messy ass barn…

[The Dark Side of Will]

BTDubz, I let all of the silicone dry nicely and went out there to start it without the belt and that bitch fired right up and idled relatively nicely. A little miss here or there, but pretty good for a big ole contraption I made in a messy ass barn…

Sweeet!

While you can, in theory, tune the engine to run lower octane, it's risky. The M20 and M30 have lousy octane tolerance/detonation resistance due to their weird chamber shapes. The M20 runs 87 stock, so you may be able to go up to 5 psi on 87... but, again, risky. Detonation can kill any gasoline engine.

If you're that set on it, learn how to tune on 93, figure out how wide your safety buffer is and tune for lower if you can.

Good tuners can make surprising combos live.

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

[Ether-D]

That sounds perfectly reasonable. Thanks.

[The Dark Side of Will]

Heat is the enemy... A batch of bad gas; a hotter day than you've tuned for; being stuck in traffic long enough to heat soak your intercooler... Any of these can give you detonation when you floor the gas, even if you've tuned it knock free under more ideal conditions. You'll have to be aware of temps and be careful.

Detonation tends to be a slow killer on engines that are in relatively low states of tune... dangerous and you never want it, but a <300 HP M20 can probably take a bit before it's seriously hurt (e.g. cracked ring land and loss of compression).

[Ether-D]

Yeah, I've seen pics of a m52 with a cracked valve from a m90, but I think he was running the OE management and thrashing it. I don't want any of that business.

But here's this. Sorry, I think I'm in love.

[Victell]

Im going against others here and say you can tune it for low octane if you want. Especially in the prototype tuning stages. Your power will be lower, but that wont matter right now because you are only testing.

Remember, lower octane is not cheap or bad gas, its just a lower octane. Plus if you want you can sample higher octane during this phase without risk. But you cant do the opposite and tune for higher octane and test with lower.

For a final product, I think a lot of people would like the option to run a low octane tune, and be willing to sacrafice some power for it. I probably would like that option.

[TheTacoMan]

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

[Ether-D]

Thanks Taco, that's great reading. Everybody read it. Doit.