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87 octane and boost

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Old Apr 27, 2021 | 07:30 PM
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Default 87 octane and boost

Yea yea yea...I know. Dumb idea. Search. Yada yada. Anyways, hear me out. First off I did search. Most of the crap I came across was people beating up on the op about this. No helpful info. So...
5.3, 9.4:1 compression. 93 octane right now, meth injected at 16psi with 5gph nozzle. I’m running a max of 22ish psi on 93, 11 degrees timing and going up to 12 in the upper rpms.

think I could get away with 12-14psi and maybe inject meth at a lower psi? Maybe lower the timing a few degrees. The reason I’m considering this is I’d like to start driving the car more but putting premium in it at $3+ a gallon and the distance I drive to work.....will add up quick vs $2.30 a gallon. That $10-$15 per fillup a couple times a week.
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Old Apr 27, 2021 | 09:17 PM
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Water/meth is good for about 20-25 octane points when it's 60% water. I run 90 with water/meth, what's another 3? You're still probably getting over 110 no matter what.
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Old Apr 27, 2021 | 10:21 PM
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Originally Posted by LetsTurboSomething
Water/meth is good for about 20-25 octane points when it's 60% water. I run 90 with water/meth, what's another 3? You're still probably getting over 110 no matter what.
well that would be pretty damn cool if I could run 87 and meth and get the same power.
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Old Apr 27, 2021 | 10:33 PM
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Originally Posted by Kfxguy
well that would be pretty damn cool if I could run 87 and meth and get the same power.
i didnt know that either. 20 to 25 octane is a big jump. Here I've been fretting over 91 and 93 octane.
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Old Apr 28, 2021 | 05:44 AM
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Saving 20-30 a week in this hobby isn’t worth it IMO. It’s your car though you don’t need our permission to run what ever fuel you want.
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Old Apr 28, 2021 | 05:49 AM
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I like hearing about low octane builds, since I run 93, no E85 around. I kind of wish I had built a lower comp. engine, but it ended up (5.3) with flat top pistons, 799 heads, and a mild cam, no IC'er. I plan on an IC'er sometime. Just on a street hit @ 8 lbs, I have seen MAT's in the 180 deg range. If I could duct the intake air outside the engine comp. prob could knock that down some. I could prob get away with lower octane if I just cruised it, no boost. Are you running knock sensors, wondered how much they knock timing back.
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Old Apr 28, 2021 | 07:02 AM
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Ballin on a budget to another level.
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Old Apr 28, 2021 | 07:43 AM
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You want to save money and run 87 but start spraying water/meth at a lower psi? Wouldn't that offset any "savings" you'd see?
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Old Apr 28, 2021 | 09:49 AM
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Originally Posted by wretched73
You want to save money and run 87 but start spraying water/meth at a lower psi? Wouldn't that offset any "savings" you'd see?
There's an excellent point, you'd want to factor in the cost of fuel and then the total cost of meth used for each fuel.
I'd be really curious to see what you'd come up with for spraying meth on 91 and meth on 87.
You know what else is gonna happen....you're gonna have a tank full of 87 for "cruising" and while heading to work you're going to run into someone who wants to play but that tank of 87 will make you think twice but not long enough to keep you from dropping the hammer lol.
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Old Apr 28, 2021 | 10:06 AM
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I’d be less worried about the cost of meth and more concerned with the fact the lower octane you run as a primary fuel the more you rely on the meth. If the meth fails you’ve got less cushion than you had with 93 regardless of what safe guards you have in place.
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Old Apr 28, 2021 | 10:32 AM
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No intercooler?
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Old Apr 28, 2021 | 10:33 AM
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Originally Posted by BCNUL8R
Saving 20-30 a week in this hobby isn’t worth it IMO. It’s your car though you don’t need our permission to run what ever fuel you want.
I was waiting on this exact reply. You did not disappoint.
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Old Apr 28, 2021 | 10:35 AM
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Originally Posted by forcd ind
I like hearing about low octane builds, since I run 93, no E85 around. I kind of wish I had built a lower comp. engine, but it ended up (5.3) with flat top pistons, 799 heads, and a mild cam, no IC'er. I plan on an IC'er sometime. Just on a street hit @ 8 lbs, I have seen MAT's in the 180 deg range. If I could duct the intake air outside the engine comp. prob could knock that down some. I could prob get away with lower octane if I just cruised it, no boost. Are you running knock sensors, wondered how much they knock timing back.
yes I run knock sensors. Its tuned at this point where it has no knock retard, the timing has been adjusted to where i dont get any knock.
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Old Apr 28, 2021 | 10:37 AM
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Originally Posted by Pro Stock John
No intercooler?
yes I have an intercooler.
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Old Apr 28, 2021 | 11:15 AM
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Originally Posted by BCNUL8R
Saving 20-30 a week in this hobby isn’t worth it IMO. It’s your car though you don’t need our permission to run what ever fuel you want.
adding $120 in monthly fuel costs is not ok with me. I dont make a bunch of money for a living.

Originally Posted by ddnspider
Ballin on a budget to another level.
I try, i try. But I'm still a broke cheapass

Originally Posted by wretched73
You want to save money and run 87 but start spraying water/meth at a lower psi? Wouldn't that offset any "savings" you'd see?
it's been at least 2 months since i spent $4 to fill up my tank.....hardly an offset....even if it spray it earlier its going to take quite a while to go through a gallon of it.

Originally Posted by The ******
There's an excellent point, you'd want to factor in the cost of fuel and then the total cost of meth used for each fuel.
I'd be really curious to see what you'd come up with for spraying meth on 91 and meth on 87.
You know what else is gonna happen....you're gonna have a tank full of 87 for "cruising" and while heading to work you're going to run into someone who wants to play but that tank of 87 will make you think twice but not long enough to keep you from dropping the hammer lol.
yea I know, however, on the way to and from work I'm in so much traffic the whole way it would pretty much be impossible to get into a race. SO i'm not too worried about that.

Originally Posted by BCNUL8R
I’d be less worried about the cost of meth and more concerned with the fact the lower octane you run as a primary fuel the more you rely on the meth. If the meth fails you’ve got less cushion than you had with 93 regardless of what safe guards you have in place.
this is true too but the way i've always done it is not rely on the meth but rather have it as an extra cushion. I always pay attention to my afr's out of habit anyways. But I get what you are saying.



I want to point out the fact that lately I've seen bags on the premium pump nozzle more than usual....so regardless, using regular is an option i'd like to have. i knew I'd get some negative comments, this is the internet....what else could I expect. However, the few that understand where I'm coming from, thx.
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Old Apr 28, 2021 | 11:20 AM
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If you are only using meth as a cushion, and don't want a failure when its not spraying and youre running 87, then I would plan to run single digit timing.
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Old Apr 28, 2021 | 11:27 AM
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We all have to choose where we cut spending. That’s why I said IMO that octane isn’t where I’d cut spending on a boosted build.

I probably make less than most here. I started out homeless when I left home due to an abusive step dad as a teenager. Yet I don’t have a credit card, only buy with cash I have including all our vehicles. I owe around 15g on my house as our only family debt.

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Old Apr 28, 2021 | 12:01 PM
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Tune for 87 (read plugs) and see how far you can go w/o wmi then add wmi and tune to aid in some additional pwr. I would not expect 93 performance without significant increase in meth content. What WM % are you using?
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Old Apr 28, 2021 | 12:33 PM
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Originally Posted by LetsTurboSomething
Water/meth is good for about 20-25 octane points when it's 60% water. I run 90 with water/meth, what's another 3? You're still probably getting over 110 no matter what.
Its not.
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Old Apr 28, 2021 | 12:42 PM
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You can run 87 with boost in an ideal combination/tune. 4-cylinders run 18-20 PSI with 87 from the factory and are reliable with extended warranties while running normal engine temps around 215-230.
Modern bikes can run 5-8 PSI on 93 octane despite being 12:1 compression.
Running low boost on a V8 on 87 octane, even without an intercooler, isn't at all outside of the realm of possibility.
You just need to understand that you can't run as much boost, or make as much power.

Something to remember: 87 octane that contains 10% ethanol is using the worst, garbage byproduct gasoline as the base. Stuff that often can't be sold on its own otherwise.
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