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Discussion Starter · #1 ·
I was just curious if anyone had seen legitimate tests on octane improvement from the variety of octane boosters out there?

The extra cost of premium over low grade unleaded made me wonder if it would be cheaper to buy a booster for the low octane gas.



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There is no difference in the caloric content of gasoline based upon octane rating. Octane rating indicates a scale of resistance to auto ignition, (aka detonation).

If you need a higher octane fuel your motor will tell you. It signals a death rattle before the pistons fail. If you hear that rattle get off the gas and pull over and note temp of outside air and coolant temp (other factors that vary going down the road from place to place is humidity).

Things that do not change with time or place are factors such as static compression and dynamic compression which are built into the engine. Ignition timing is another variable but hopefully you constrained the curve to a point that is safely below detonation. Final variable as to detonation is how you are driving because the load on the engine is the other big variable.

I am a mechanical engineer. I was taught if it ain't broke don't fix it save your money for things that make a difference. I built three high compression max effort engines and tried to run them on the street. I was running just below 13.7 static compression and it needed 104 octane to run (it was never happy at 104 and finally switched to 110 octane). Extremely expensive, limits were and how far you can drive and the gas goes bad in weeks once unsealed. Not worth the effort.

Big Dave
 

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Discussion Starter · #3 ·
I thought I asked a simple question but I don't disagree that all of that good info from you is good stuff for others to know.

For the record, I do occasionally get dieseling when I turn the key off.
Timing was of course checked for both initial and full.

The real question is about cost.
With premium being 60 to 70 cents per gallon higher than 87 octane, then on a 20 gallon fill we are looking at $12-$14 extra.

That kind of money could potentially buy enough of a good octane booster to use with 87 octane.

30 years ago I would buy a product that had high levels of MMT and it worked well for me. These days I do not no who's got the good stuff.








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Run on (dieseling) is a indication of the throttle blades not fully closing to THROTTLE the engine (the way you kill a diesel engine). This could be due to a sticking choke cam, a radical cam that requires more air at idle than can fit through the idle circuits in your carb, or just a bad tune up (too lean).

Your carb can handle more air even if it is a two barrel Rochester. In the case of the Rochester 2G you have to physically modify the carb with drill bits and trial and error. This is why the Holley and Weber carb systems are so popular; they are far easier to modify with parts bought from Holley or Weber (no drilling so it is reversible and trial and error time is reduced).

This was a real issue in the mid eighties when the factory was forced to go far to lean at idle to pass an annually more restrictive emission regimen. The factory solution was an external solenoid that bolted to the Rochester QuadraJet that fully closed the throttle blades when the ignition was turned off.

Dieseling is hard on the alternator because the engine frequently reverses the direction of rotation; blowing the diodes in the inverter that converts AC to DC current.

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I just started having this issue the car ran great and wouldn't do that before but does it sometimes now. I have a edelbrock carb on it though. I tried using sea foam to see if it would help but still does it some times. I looked up potential causes and carbon build up was said to be one possibility and can be cleaned out by pouring small amounts of water in the carb and the steam would remove it.
 

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I just started having this issue the car ran great and wouldn't do that before but does it sometimes now. I have a edelbrock carb on it though. I tried using sea foam to see if it would help but still does it some times. I looked up potential causes and carbon build up was said to be one possibility and can be cleaned out by pouring small amounts of water in the carb and the steam would remove it.
not something I would EVER do.

pour water into an engine? even small amounts? and how's it going to turn into steam? the manifold ain't that hot
 

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Discussion Starter · #7 · (Edited)
I've done it but that was long ago before we have the chemical availability that we have now.. It's a tried and true old school method that even got new life when turbo's started getting more factory attention years back.
We're talking about a very minor trickle from a straw, or like a spray bottle.stream. They've even got Meth/water injection kits not just for the cleaning effect but the cool-down effect.
Shoot, I THINK I even saw a Hot Rod Engine Master episode about the water-meth ratio effectiveness!
Yep - >>> "Engine Masters" Water-Meth Injection: Is It Cooler Than the Intercooler?? (TV Episode 2021) - IMDb


Combustion temperatures are 2800 degrees Farenheit or more so more than enough to steam the very small amount of water we're talking about.

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I've done it but that was long ago before we have the chemical availability that we have now.. It's a tried and true old school method that even got new life when turbo's started getting more factory attention years back.
We're talking about a very minor trickle from a straw, or like a spray bottle.stream. They've even got Meth/water injection kits not just for the cleaning effect but the cool-down effect.
Shoot, I THINK I even saw a Hot Rod Engine Master episode about the water-meth ratio effectiveness!
Yep - >>> "Engine Masters" Water-Meth Injection: Is It Cooler Than the Intercooler?? (TV Episode 2021) - IMDb


Combustion temperatures are 2800 degrees Farenheit or more so more than enough to steam the very small amount of water we're talking about.

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I've seen a guy at the dragstrip using water injection for the cooling effect, but that's a far cry from "pouring small amounts of water in the carb"
 
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