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      05-17-2020, 09:53 PM   #1
D CHOI
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Catted DP with 100 octane

I have the fabspeed HJS 200 cell DP and it's throwing the CEL due to wear with unleaded 100 octane mix. I usually mix 3ish gallons of 100 with 91 to get 93 octane. One time I ran full 100 octane. Now overtime it caused the CEL.

I plan to just keep the catted DP long term and turn off cat monitoring with the bm3 tune. I'm not sure if it's safe long term to keep using the unleaded 100 octane mix with 91 and on rare occasions use full 100 octane.

I was told by one of the fabspeed reps concern is running high octane fuel is melting the cores and causing a blockage. If that's the case it can be catastrophic.

Anyone have knowledge about this?
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      05-17-2020, 11:49 PM   #2
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High octane tend to protect the cats because combustion is cooler with higher timing.

All cats wear, stock one included. Fuel is in play but octane is not why.

It's matter of how the tune and you push it.
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      05-17-2020, 11:58 PM   #3
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Quote:
Originally Posted by SeanWRT View Post
High octane tend to protect the cats because combustion is cooler with higher timing.

All cats wear, stock one included. Fuel is in play but octane is not why.

It's matter of how the tune and you push it.
Combustion is only cooler at higher ignition timing if boost is lowered as well. If the tune targets higher ignition timing because the octane is now sufficient and keeps boost where it is then the combustion temperature rises. You can only have the latter if you specifically tune the car to be biased on ignition timing over boost.
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      05-18-2020, 12:07 AM   #4
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I've been on the BM3 stage 2 93 tune so mixing the 100 octane is a must. I have west coast 91 so it's bad 91. Hence why BM3 offers ACN 91 map.

I just hope using the cat long term will not cause anything bad to happen as I don't want to switch to catless even tho my cat is going bad.

The 100 octane is like crack lol and hard to go back to bad 91 after u use it. Car just runs better especially at higher RPMS. I wished 93 octane is offered here but not possible due to government laws
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      05-18-2020, 12:23 AM   #5
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Quote:
Originally Posted by D CHOI View Post
I've been on the BM3 stage 2 93 tune so mixing the 100 octane is a must. I have west coast 91 so it's bad 91. Hence why BM3 offers ACN 91 map.

I just hope using the cat long term will not cause anything bad to happen as I don't want to switch to catless even tho my cat is going bad.

The 100 octane is like crack lol and hard to go back to bad 91 after u use it. Car just runs better especially at higher RPMS. I wished 93 octane is offered here but not possible due to government laws
Yeah that sucks you can't get better gas, I don't know if vegas has ethanol, but if it does that would be a better solution.

I can't comment if your cat will melt or not, but just take it easy on the car and run a more conservative tune.
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      05-18-2020, 01:27 AM   #6
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Quote:
Originally Posted by F87source View Post
Yeah that sucks you can't get better gas, I don't know if vegas has ethanol, but if it does that would be a better solution.

I can't comment if your cat will melt or not, but just take it easy on the car and run a more conservative tune.
Yea we do have E85 and bm3 offers the E30 map. To get the true E85 map u have to reach out to bm3 and pay a premium. Only problem with E85 mix is u need exact mixture where as it's fine to overfill with 100 octane. I would need to get an octane gauge if I were to go E30 map route.
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      05-18-2020, 01:34 AM   #7
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Quote:
Originally Posted by D CHOI View Post
Yea we do have E85 and bm3 offers the E30 map. To get the true E85 map u have to reach out to bm3 and pay a premium. Only problem with E85 mix is u need exact mixture where as it's fine to overfill with 100 octane. I would need to get an octane gauge if I were to go E30 map route.
You could also use an e85 tester kit ($20 and you can use it as many times as you want) to test e85 content at the pump. Based on that you can calculated how much e85 and pump gas you need to mix. Then do so in a large fuel jug and measure one more time with the e85 tester. That will give you a large barrel of fuel that can be used multiple times.
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      05-19-2020, 12:17 PM   #8
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Quote:
Originally Posted by F87source View Post
Combustion is only cooler at higher ignition timing if boost is lowered as well. If the tune targets higher ignition timing because the octane is now sufficient and keeps boost where it is then the combustion temperature rises. You can only have the latter if you specifically tune the car to be biased on ignition timing over boost.
No.
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      05-19-2020, 02:18 PM   #9
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Quote:
Originally Posted by SeanWRT View Post
No.
... Do you realize higher octane fuels do not have evaporative cooling effects like ethanol? So they don't make the cylinder temps decrease.

Do you also realize the car is mainly tuned to pull timing and not boost when the car knocks. So if a higher octane fuel is used and knock is eliminated the car will target a higher timing curve at the same boost?

Did you also know how increased timing works? It means the combustion mixture is ignited further from top dead center allowing the combustion to expand while also being compressed by the upward motion of the position further increasing pressure. What does increased pressure result in? Higher cylinder temps. This combined with the fact that boost pressure did not change means temperatures will increase.

If you drop boost while targeting for more timing this will result in cooler temps, because higher boost pressure contributes to higher temps than higher ignition timing.


I understand what your trying to say because that's how your tune is setup, but you have to explain for op who is using an ots map that is not designed like yours to favor temps for racing as opposed to making peak power safely.


Also a great example why you're wrong is tuning an NA car, if you increase timing the cylinder temps increase as seen with am egt sensor. If you increase octane to a race fuel and continue to increase timing temps will follow. Its clear physics the more you increase compression the more pressure you have which correlates to more temperature, no getting around that Shawn.........
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Last edited by F87source; 05-19-2020 at 02:23 PM..
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