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Thread: Mixing fuel to get 93 octane
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07-28-2011, 11:52 AM #16
Aces?
24 Skater w/ 300 Promaxes "99 Problems"
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07-28-2011, 12:10 PM #17
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07-28-2011, 04:03 PM #18
It's been a while since I've used race gas in things but as I recall many of the high octane race gases are oxygenated to produce more power. These fuels required a jet change or EFI tune in order to not run lean. Avgas is not oxygenated in that manner. So, yes running large concentrations of oxygenated high octane race gas in an engine not tuned for it could conceivably lead to a lean seizure. There are many different types of race gas with many different formulations. Which one you were running I don't know. Someone on here will probably chime in and tell me that's wrong as there seems to be a lot of disagreement about gas, octane, mixing, formulas, oil ratios, oil brand etc. but that's the way I remember it. Often if you research the race gas fuel suppliers they will tell you what fuels are oxygenated and some will discuss necessary jet or EFI tuning changes when running these fuels. Other suppliers just assume that if you run race gas, you already know what you are doing.
Last edited by keane; 07-28-2011 at 04:09 PM.
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07-28-2011, 04:15 PM #19
My question is why would anyone want to run anything higher than 93 in a 120 psi compression engine? Even 93 is a push. High octane in a low compression engine results in only about 75% of the fuel being utilized for energy. What do you think the unburnt fuel does to the recipricating mass when compressed and not burn't?
Bud Conner "Heathen" "Defending Our Constitution"
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07-28-2011, 04:27 PM #20
I think the first guy that initiated the thread was trying to mix 87 - 91 octane with something else to get 93 (just to be safe) And it sounds like native 2 was overzealously mixing 110 with 89 to be on the safe side. I know my Bridgeport manual only calls for 89 but I run 91 because I don't trust the gas stations quality of gas, and my 280 calls for 92 (which isn't available in Maine) so I mix to get 93 just to be on the safe side. I generally try to be one or two points higher than that required for any performance engine because having too low of octance can be disastrous. I agree with you, higher octane than necessary is not a good thing.
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07-28-2011, 04:38 PM #21Banned
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The gas station man where my cabin is sells 93 no ethanol,and it was gonna be his last tank full because he can no longer find it (sucks)any how he just told me that 87 octane is usally 89 because thats the way it is,must be a way to cover themselves..
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07-29-2011, 05:14 AM #22
Last edited by Markus; 07-29-2011 at 06:49 AM.
Markus' Performance Boating Links:
www.toastedmarshmallow.com/performance
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07-29-2011, 07:06 PM #23
Only where they are afraid of being caught by the law ... elsewhere its just market driven.
Maryland checks periodically, most states do not. There is about 10% non-compliance in MD where it is checked and they are fined for not meeting grade ... how good do you think compliance is where they are not being checked on?
To Markus: If there was no economic incentive, why would they risk being fined?
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07-29-2011, 08:25 PM #24Markus' Performance Boating Links:
www.toastedmarshmallow.com/performance
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07-30-2011, 09:52 AM #25
Its on all grades, including 87 being deficient some times
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09-30-2013, 11:17 PM #26
Okay so I've been doing some seraching on here and I'm bringing up this old thread. I recently converted my 200 EFI setup to 280's. Went from oil injection to pre-mix. At the time I refueled my 200's were on the boat and I topped off twin 50gal tanks with 90 rec fuel. Pulled the motors off with about 32 gal of the 90 left in each tank. So I switched over to pre-mix and now I just want to make sure I have al my ducks in a row.
Added the proper amount of Penzoil Full Synthetic Oil to the tanks at a ratio of 40:1. Also added 18 gals on 100LL to each tank, which according to the formula listed above, created a mixture of approximately 93.6 octane. My 280's are bone stock and have actually never been rebuilt. I know they are due for rebuilds (135hrs) so I'm not pushing them too hard until I have the $$ to get them done. I have read about 30 pages of info on Aces for boosting octane, but I'm not 100% convinced that it works in that aspect. Apparently it helps reduce engine wear which could be very beneficial. But my goal is to run non-ethanol fuel at the right octane to avoid any issues with detonation or ethanol deterioration issues with fuel tanks and fuel lines. Peter at Skater says my tanks are okay based on the year, but again, I'm not 100% convinced. I know the ethanol destroys fuel components, and that is why I'm trying to avoid it. I have a station near me that sells 90rec, 100LL, and 110 Race fuels. My only concern is if I take the boat somewhere not near home and need to refuel with the pumps on the water. I have to do a recent compression check, but last one I was told was 155psi across the board. I ran the boat this weekend on the mix I posted above and didn't have any issues. Not trying to play with compression numbers or any of that to squeeze out every MPH, just looking to go as fast as Mercury Racing designed these motors to go, safely, and avoid a grenade. Thanks.2004 Deep Impact 36 Triple 300 Verados
1998 Donzi 35 ZFC Triple 300 Verados FOR SALE
1989 24ft Skater, Twin Diamond Marine 280's with Diamond Tuners, 34p Cleavers. A few pieces of JL Audio equipment.- SOLD
1988 18ft Talon- SOLD
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10-01-2013, 06:17 AM #27
tony97gt Thanks for pulling up this thread--Lots of good info. Good luck with your new power! Great lookin rig!!! Gary
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10-01-2013, 10:04 PM #282004 Deep Impact 36 Triple 300 Verados
1998 Donzi 35 ZFC Triple 300 Verados FOR SALE
1989 24ft Skater, Twin Diamond Marine 280's with Diamond Tuners, 34p Cleavers. A few pieces of JL Audio equipment.- SOLD
1988 18ft Talon- SOLD
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10-01-2013, 11:22 PM #29
Just to clear some things up for myself, since this thread has touched on a few different situations as far as required octane and fuel oil ratios, I have a Mercury Catalog from 1997 with all 2.5 models of High Performance engines and it shows mixing 32:1 for S3000 requiring race fuel, 32:1 for SSS120 requiring 92 octane leaded or unleaded, 32:1 for F1 requiring RACE FUEL, 32:1 for XR2 requiring 92 octane leaded or unleaded, 32:1 for 2.5 SS Drag requiring 92 octane unleaded only, 32:1 for 2.5 Offshore EFI RACE requiring 92 octane unleaded only, For all PROMAX Motors it only says 89 octane Minimum and Variable oil injection, then it gets into the 2.5 EFI 260s with peak HP @ 7500 RPMs, which is what I have, and calls for 32:1 92octane leaded or unleaded. So my question is why do some of them require unleaded only but other can be used with both leaded and unleaded? And why would any one run 40:1 in any 260 or 280? I have an even older catalog like this one that is a few years older that I cant find at this time but I seem to remember it showing a reference to 100LL for some of the engines in it. Not really waiting on any certain response but I felt like adding this in.
The evidence of poor quality lingers much longer than the success of meeting a budget.
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10-02-2013, 05:54 AM #30
I could be wrong but I believe I read somewhere that the 32:1 is for ROS models. I was told by Diamond that I should run no leaner than 40:1 so I'm running that. I have consumer ecu boxes and I'm actually not revving over 5500-6000 rpm on my 280's until they get a rebuild. I don't have an explanation for leader vs unleaded, only read in the manual that unleaded is preferred because leaded can leave heavy exhaust deposits.
2004 Deep Impact 36 Triple 300 Verados
1998 Donzi 35 ZFC Triple 300 Verados FOR SALE
1989 24ft Skater, Twin Diamond Marine 280's with Diamond Tuners, 34p Cleavers. A few pieces of JL Audio equipment.- SOLD
1988 18ft Talon- SOLD