Fuel octane booster: additives
#2997016
12/20/21 12:23 PM
12/20/21 12:23 PM
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Joined: Aug 2003
Posts: 8,828 Houston, Tx
hemi68charger
OP
master
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OP
master
Joined: Aug 2003
Posts: 8,828
Houston, Tx
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Hey gang..
Just brought home my Hemi Superbird and did some tuning yesterday. The motor pings under load cruising down the street. At the present time, the timing is set to about 34 degrees total advance at 2500 rpm. In the event I can't get a good combo for the curb idle timing and idle speed setting, I may have to go to additive of the motor has a higher than OEM compression. Not sure what that compression is at this time. What octane additive do you all use? I'm looking for suggestions. I haven't had a need to do that in a long time. I may try the FPO Advance Limiter plate for it so I can get good initial curb timing while maintaining a reasonable total limit, say 30-32?
Cheers, Troy
TroyHouston Mopar Connection Club'69 Charger Daytona 440 - auto - 4.10 Dana (now with 426 hemi) '69 Charger 500 440 - 4speed - 3.54 Dana '70 Road Runner 383 - 4speed - a/c (now with 440)
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Re: Fuel octane booster: additives
[Re: hemi68charger]
#2997026
12/20/21 12:56 PM
12/20/21 12:56 PM
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Joined: May 2019
Posts: 6,250 nowhere
Sniper
master
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master
Joined: May 2019
Posts: 6,250
nowhere
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Most octane boosters are useless unless you are just barely on the cusp of knock. Read the labels, if they say they raise it a number of "points" they mean points as in 0.1. So you'd go from 93.0 to 93.6, if they raise it six points, for example.
Royal Purple's Max Boost claims up to 30 points, so that 93 octane would bump up to 96 octane. It uses MMT There are others that claim it can bump pump gas, I assume premium, to as much as 105 octane.
Basically, the good stuff isn't cheap, the cheap stuff isn't good and the good stuff tends to be "not street legal" for whatever reason. Most likely because they use MMT and the amounts needed to raise pump gas exceeds the EPA's limit and there is some disagreement as to the toxicity of MMT when handling it. It degrades readily when exposed to light, so if it's in a can it's probably got MMT in it.
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Re: Fuel octane booster: additives
[Re: hemi68charger]
#2997037
12/20/21 01:36 PM
12/20/21 01:36 PM
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Joined: Dec 2018
Posts: 88 IL
83hurstguy
member
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member
Joined: Dec 2018
Posts: 88
IL
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Is the vacuum advance hooked up too? How much timing is that adding? Cruising down the street is a prime scenario for vacuum advance plus the fast mechanical curve adding up to a lot of timing.
The second item that few people check is if the balancer/TDC marks are accurate. It's rare that I see them match up, whether rebuilt original dampers or aftermarket.
Last edited by 83hurstguy; 12/20/21 01:37 PM.
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Re: Fuel octane booster: additives
[Re: second 70]
#2997356
12/21/21 05:18 PM
12/21/21 05:18 PM
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Joined: Jan 2011
Posts: 15,867 Central Florida
larrymopar360
Stud Muffin
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Stud Muffin
Joined: Jan 2011
Posts: 15,867
Central Florida
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I've never been able to have vac advance connected on any of my small block Mopars. Three mild cammed Magnum 360's 9.1 compression and making 320hp. Ran great around 32 total timing and vac advanced disconnected. My E58 didn't like it either. Lots of surging could be felt and could never get the timing set to where the vac advance didn't cause some pinging.
Facts are stubborn things.
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Re: Fuel octane booster: additives
[Re: larrymopar360]
#2997369
12/21/21 06:01 PM
12/21/21 06:01 PM
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Joined: Mar 2005
Posts: 1,550 Michigan
Kiddart
pro stock
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pro stock
Joined: Mar 2005
Posts: 1,550
Michigan
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you did not mention what octane you are running now. I have run 93 octane here in Michigan and used this additive from Mancining racing. you can get it all over the usa. it works good but at that time i was going thru gas like bubble gum. ended up just biting the bullet and ran pump swill 110 torco at the local station that had it. the turbo blue worked just fine as well. look into this and see if this can help you out https://race-gas.com
Thank you Kiddart
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Re: Fuel octane booster: additives
[Re: hemienvy]
#2997684
12/22/21 09:07 PM
12/22/21 09:07 PM
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Joined: Nov 2007
Posts: 21,823 Kirkland, Washington
Pacnorthcuda
Too Many Posts
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Too Many Posts
Joined: Nov 2007
Posts: 21,823
Kirkland, Washington
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Under conditions of high manifold vacuum, which would add advance, you are still not building peak cylinder pressures, nowhere near what you would have at WOT. I don't see how vacuum advance could contribute to pinging unless something besides manifold vacuum was activating it. I’ve had a few engines that experienced pinging at part throttle. Easiest check in the world to simply disconnect and drive it. I had to dial back my Mallory made Mopar adjustable vacuum can on my current 440 to avoid it, that was in conjunction with an all in at 2300 rpm mechanical.
Last edited by Pacnorthcuda; 12/22/21 09:10 PM.
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Re: Fuel octane booster: additives
[Re: Pacnorthcuda]
#2997698
12/22/21 10:26 PM
12/22/21 10:26 PM
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Joined: Jul 2011
Posts: 957 Chicago
PurpleBeeper
super stock
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super stock
Joined: Jul 2011
Posts: 957
Chicago
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Tons of great advice here....you can probably tune it where you need it. Maybe double check for vacuum leaks to make sure it's not going lean and cauing the ping.
But to answer your question about octane boosters (a band aid, but you might need one for a little while).... as mentioned correctly, octane boosters that say "adds 5 points" means adds 0.5 octane points (a dirty secret of the octane booster industry}. Xylene and toluene are both very effective and can be bought as paint thinner in hardware stores. Plan on adding a couple gallons to the tank (ballpark guess, it can be calculated). Toluene is 114 octane and xylene is 117 octane
70 Roadrunner convt. street car
440+6, NOS, 4-spd, SS springs
'96 Mustang GT convt. street car
'04 4.6 SOHC, NOS, auto, lowered
"Officer, that button is for short on-ramps"
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