[CalAcacian]

Hello everyone,

I know that the first response to this post will be "post logs," but I have so far been unable to capture this issue on a log.

It is an intermittent part throttle stumble from the engine (vibration, lack of power and acceleration) which tends to occur at roughly 2,000-3,000 RPM at decent but not heavy throttle application. Light throttle application does not cause this.

Of note, it has almost always occurred at highway speeds (70ish) and typically in 5th or 6th gear at these RPMs.

I always get out of the throttle as soon as I feel it. Full throttle acceleration does not cause this issue except on one occasion.

This has occurred over a range of ambient temperatures, from low 60's to mid 90's.

My car is currently running the following relevant mods: Dinan intake, CSF intercooler, fabspeed sport cat, full Dinan exhuast. The car is fueled with CA 91 octane fuel and 8oz of boostane per tank.

The car is running the stage 2 93 octane tune, although I have experience this same issue on the ACN91 stage 2 tune as well.

Coincidentally, the car is scheduled to have the oil and spark plugs changed next week at the dealer. I will be asking the dealer to save me the spark plugs so I can look at them to see if there is any obvious damage that could be leading to the issue.

Has anyone experienced this issue or have any idea what could be causing it? Any thoughts are appreciated.

[Wolfman’s Brother]

I think I wouldn’t be comfy running the 93 tune with 91+booster.

I have no data/knowledge to back that up, beyond a convo with the tuner at Bend Calibration that seems to be well respected. I’m running BM3 S293 on non-ethanol 95aki Chevron pump for safety margin, which tells you what a wuss I am with regards to these tunes.

I think the plugs will help.

Beyond that, have you checked to see if it’s throwing/logging any codes? Last chatter I saw referencing breakup or issues with tunes/driveability or startup there were codes involved that were referenced later on.

[CalAcacian]

Originally Posted by Wolfman’s Brother

I think I wouldn’t be comfy running the 93 tune with 91+booster.

I have no data/knowledge to back that up, beyond a convo with the tuner at Bend Calibration that seems to be well respected. I’m running BM3 S293 on non-ethanol 95aki Chevron pump for safety margin, which tells you what a wuss I am with regards to these tunes.

I think the plugs will help.

Beyond that, have you checked to see if it’s throwing/logging any codes? Last chatter I saw referencing breakup or issues with tunes/driveability or startup there were codes involved that were referenced later on.

You may be right, according to Boostane's calculator I should be looking at an end resulting mix at 97 octane (although I take their calculations with a grain of salt). The confusing thing is that even with the same fuel mix, I have see the issue on the 91ACN stage 2 tune as well.

No codes so far, so I am rather confused.

[ZM2]

Hope you get this sorted.

I don't have any tips other than any time I tried running the Race Gas maps they always worked better with actual race gas than putting enough Boostane in the tank to "achieve" the calculated required octane level.

[CalAcacian]

Originally Posted by ZM2

Hope you get this sorted.

I don't have any tips other than any time I tried running the Race Gas maps they always worked better with actual race gas than putting enough Boostane in the tank to "achieve" the calculated required octane level.

Thanks. I am always dubious of the claimed results octane boosters advertise. Unfortunately, the only nearby station that sold 100 octane has shut down. My only other option would be mixing with E85 which I do have relatively nearby.

[ZM2]

Originally Posted by CalAcacian

Thanks. I am always dubious of the claimed results octane boosters advertise. Unfortunately, the only nearby station that sold 100 octane has shut down. My only other option would be mixing with E85 which I do have relatively nearby.

Ahh, interesting. I'd definitely go that route vs Boostane. I've mixed with E85 for several years and the result has always been better than octane booster.

If you're still on the stock HPFP, just keep the mix below 30% and you should be fine. I wonder if the issue will resolve itself simply from the fuel switch.

[CalAcacian]

Originally Posted by ZM2

Ahh, interesting. I'd definitely go that route vs Boostane. I've mixed with E85 for several years and the result has always been better than octane booster.

If you're still on the stock HPFP, just keep the mix below 30% and you should be fine. I wonder if the issue will resolve itself simply from the fuel switch.

I'm going to try that with the next fill up. I'll throw 3.2 gallons of E85 in. That should mix with 91 to make a tank of 93.1 octane at 29% E content if I'm correct about a 13.7 gallon total capacity.

[ZM2]

Originally Posted by CalAcacian

I'm going to try that with the next fill up. I'll throw 3.2 gallons of E85 in. That should mix with 91 to make a tank of 93.1 octane at 29% E content if I'm correct about a 13.7 gallon total capacity.

The math sounds right. Just add the E85 first b/c you'll only be able to put in 13gal of fuel on an empty tank b/c BMW keeps some reserve in the tank.

[ChrisM4]

Originally Posted by CalAcacian

Hello everyone,

I know that the first response to this post will be "post logs," but I have so far been unable to capture this issue on a log.

It is an intermittent part throttle stumble from the engine (vibration, lack of power and acceleration) which tends to occur at roughly 2,000-3,000 RPM at decent but not heavy throttle application. Light throttle application does not cause this.

Of note, it has almost always occurred at highway speeds (70ish) and typically in 5th or 6th gear at these RPMs.

I always get out of the throttle as soon as I feel it. Full throttle acceleration does not cause this issue except on one occasion.

This has occurred over a range of ambient temperatures, from low 60's to mid 90's.

My car is currently running the following relevant mods: Dinan intake, CSF intercooler, fabspeed sport cat, full Dinan exhuast. The car is fueled with CA 91 octane fuel and 8oz of boostane per tank.

The car is running the stage 2 93 octane tune, although I have experience this same issue on the ACN91 stage 2 tune as well.

Coincidentally, the car is scheduled to have the oil and spark plugs changed next week at the dealer. I will be asking the dealer to save me the spark plugs so I can look at them to see if there is any obvious damage that could be leading to the issue.

Has anyone experienced this issue or have any idea what could be causing it? Any thoughts are appreciated.

I wouldn't run 91 plus boostane on the 93 tune. Also I've heard of octane boosters staining/fouling plugs. It sounds like detonation to me but also check for vacuum leaks. (Make sure everything is torqued properly) Vac leaks can also cause stumbling at tip in.

[CalAcacian]

Originally Posted by ChrisM2

I wouldn't run 91 plus boostane on the 93 tune. Also I've heard of octane boosters staining/fouling plugs. It sounds like detonation to me but also check for vacuum leaks. (Make sure everything is torqued properly) Vac leaks can also cause stumbling at tip in.

Yeah, I'm going to use the upcoming spark plug change as an opportunity to restart just running an E30 blend and see how that is.

[VisualEcho]

People still use octane boosters? Wow.

Sorry you're having the issue bro, but I'd definitely stop with the octane boost and flash the 91 map back. In fact, I'd swap to the stock map to see if the issue happens there, as I'm feeling it's not the plugs.

You've checked all your intercooler and charge pipe fittings?

[mike@x-ph.com]

Datalog and send it to PTF

[CalAcacian]

Originally Posted by VisualEcho

People still use octane boosters? Wow.

Sorry you're having the issue bro, but I'd definitely stop with the octane boost and flash the 91 map back. In fact, I'd swap to the stock map to see if the issue happens there, as I'm feeling it's not the plugs.

You've checked all your intercooler and charge pipe fittings?

Yup, intercooler and charge pipe are all firmly connected. It's not a loss of boost issue.

Since I've switched to the E30 blend and tune the issue hasn't presented itself.

I think the issue was with the octane rating leading to the engine detecting knock and killing timing, but I don't have logs to prove it.

[VisualEcho]

Originally Posted by CalAcacian

Yup, intercooler and charge pipe are all firmly connected. It's not a loss of boost issue.

Since I've switched to the E30 blend and tune the issue hasn't presented itself.

I think the issue was with the octane rating leading to the engine detecting knock and killing timing, but I don't have logs to prove it.

I didn't realize the intervention would be that strong. Interesting.

[CalAcacian]

Well, looks like that solved it. Running the 93 tune on juiced up 91 just didn't work. But so far the car is completely happy on the E30 tune.

It's actually faster than before and hasn't broken up once. I'm going to take a look at the plugs when they get pulled out on Wednesday to see if the octane booster had fouled them at all.

Either way, I expect with the oil change and new plugs the car should be very happy.

[ZM2]

Originally Posted by CalAcacian

Well, looks like that solved it. Running the 93 tune on juiced up 91 just didn't work. But so far the car is completely happy on the E30 tune.

It's actually faster than before and hasn't broken up once. I'm going to take a look at the plugs when they get pulled out on Wednesday to see if the octane booster had fouled them at all.

Either way, I expect with the oil change and new plugs the car should be very happy.

My car always ran meh on booster, but has always ran better than stock on E. Love E85!