E85, Boost and Ignition Timing
 

I've made the switch to E85 and I'm loving it so far. I've basically just done the scaling part (scaled DI and port injectors) similar to the how-to provided by @mad_sb. It worked very well, and the trims were pretty much dead on without any further adjustment (so far, we'll see again on the next tank). I also leaned out the target open loop afr slightly. i plan to bump the boost to 10-12psi until it's on the dyno.

I will use a dyno to tune the ignition timing for the sake of not running past MBT and blowing up the engine. My ignition map is currently the same as the 93 tune, running around 12 degrees at peak torque and 16-17 at max rpm. I've read lots of different opinions and reviewed lots of logs and the information is all over the place on where to go from here. The general consensus seems to be that E85 likes a bit more timing up top, and maybe a tiny bit more around peak torque but not much. Also most seem to agree that E85 likes more timing in the low-load cruise sections.

So how much timing are you guys on boost with E85 actually running? It'd be very interesting to get an idea of where we're all finding MBT. I'll post my results as soon as i can get on the dyno, but that won't be for a few more weeks.

On a side note, the 'tip in knock' that i was reporting earlier is still every bit as present and behaving exactly the same with the E85, and i can't hear it with det cans, so I'm considering it false knock from now on. Seems reasonable?

The "tip in knock" you are reporting is definitely from knock. I did a lot of research into this with the Innovate Supercharger kit, and under quick throttle blips with the Innovate Supercharger it generates enough boost to cause it to knock.

Now on turbo vehicles I have not seen this quite as drastic, but it still seems to be there. Do you have any more videos of the noise you are hearing know versus before? Also any logs to review?

Sorry I am not up to speed on whether you are running a turbo or supercharger.

Cheers,
William Knose

it's a gtx2867r. there is no audible sound of knock, even with electronic det cans attached to the block. it does seem too repeatable to be false knock though. it's always -1, and shows up as a -0.7 or -0.35 in flkc sometimes.

Do you have any logs? Is it only right after throttle blips? What are the A/F ratios doing and the ignition advance doing? RPm specific or everywhere?

Sorry for all the questions, but just trying to understand a little more of what is going on.

absolutely... i have months worth of logs :). i can send them to you if you'd like to look at them. basically i get a consistent -1 fbkc every time i get into the throttle more than a tiny bit. if i'm just lightly cruising on the highway it doesn't happen, but if i give just enough so that i'm not quite in boost but you can hear the turbo starting to spin up and hold it there, it'll happen. if i stay on the gas through it, it'll be gone by around 3.5krpm.

it's been driving me nuts since i started tuning the car. i keep thinking it's false knock but i know better, i'm just convincing myself it is lol. it was way worse on my original tune, getting -2's and -3's, but yet i've taken timing out of the offending areas to no avail trying to get rid of the -1's. i've also tried tuning the tip-in enrichment, which i havent done a great job of yet. that's my next area of exploration lol.

thanks for your input, always appreciated :cheers:

Make an account on my website, and I can upgrade your account to allow for support tickets. Then you can send logs over there for review.

I went through similar things with the Innovate Supercharger tune, which ended up being a little worse, as when you blipped the throttle it would actually boost 3-5 psi, which made it even worse on the knock correction.

Cheers,
William Knose

Fantastic, will do.

On a side note... what AFR's are you guys targeting under boost? i've read some crazy things, like running leaner around 12:1 or so can not only be safe but actually reduce the likelihood of knock. currently i'm running 11.4:1 (roughly, hovers from 11.2-11.5). Note this question is for anyone running E85 on boost, not just delicioustuning.

I have seen many post about tip in knock, but nobody has posted exactly what it is or vaguely what causes it. It sounds to me like partial load induced knocking. Is that accurate?

pretty much. it's just a small knock event that happens any time load ramps up quickly. fbkc usually picks it up, and you'll see it in the flkc after a while as small negative corrections.

It is a very minimal amount of knock if you are only seeing -1 but if it always happens in the same place it is definitely signs that the engine may not be knocking but definitely on the edge at these specific points. The question is how bad is that or is the -1 enough to say the engine is fine. The only reason I bring that point up, is the stock vehicle has plenty of knock corrections, so tough to say what is really serious and what is not when the OEM map is worse than I would prefer to see.

that's my problem exactly. i'm torn over whether or not to care about it lol.

E85 knocks on the rich side Pump gas knocks on the lean side. If it were me, I would be shooting for 11.8 on a good wideband on E85.

As for the tip in issue, don't rule out the possibility of an anomaly in the knock detection code... evo's suffered for many years due to the way the knock buffer worked...

I still see -1 in the feedback correction NA on E90+ Also rom raider has more of the tip in enrichment tables now... need to see some logs of the afr etc during the events, you could also be crossing the point where the port injectors shut off creating a momentary lean spot as it transitions to direct only....

Well the only reason why I would like to know if it is really a problem or not is because I have managed to remove this problem all together (so no knock correction at all) but it took EcuTeK RaceROM custom mapping to do so.

I did spend quite a bit of time trying to make it happen without EcuTeK RaceROM, but had similar problems to everyone else. With the twin screw Innovate Supercharger that makes boost just revving it, I am sure you could only imagine how much correction that was seeing.

But if it not really a problem, then do I need those custom maps? But the custom maps are helping since there is no knock correction. So the question remains is it really a problem or not on boosted applications? Let me look into this a little more.

I see a bit of this myself, typically on the freeway. Not sure if it's the same thing being discussed here, but usually around -0.7 on partial throttle if I ride the point the turbo begins to spool. Really the only time I ever see it.