Since we all "know" the gas scale and lambda works out to what it works out we refer to the gas equivalent of AFR. Most dont have a WB that will read alcohol based AFR's so its convenient shorthand I think. I mean if I personally was using a alky WB and saw 9.76 AFR my gut reaction is going to be pig rich and not stoich, where I might see an 8.5 and think "oh sweet I am good" and then really be at 13.0 or something.

I hope that came out in english :lol: {thumbup}

John, yeah, that makes some what sense..... I have use a motec WB where you could change it to alky so lambda is correct. My understanding of lambda is it is 14.7/14.7=1 for gas and A/F/14.7=lambda gas. So if you use lambda for e85 it would have to be corrected, I believe it is something like 10.5:1 off the top of my head, so a lambda of 1 would be 10.5/10.5......... not sure if all that makes sense either... :-) I just wanted to make sure when someone says an A/F of 11.5, they are speaking in terms of a gas WB, in other words Uncorrected.

Maximum Best Torque. Could also mean mimimum best timing. At any given RPM, its the least amount of timing that yields the most torque. It could in concept be applied to any fuel such as 91 oct. In that case, it would simply be the greatest amount of timing below the knock threshold. However, its usually used in the context of a fuel that will not detonate. In that case the mimimum best timing is the least amount of timing that yields the greatest amount of torque. It occurs when the timing is adjusted so that the peak pressure in a combustion event occurs at around 15 deg ATDC. Any more timing and the pressure peak occurs too soon (pushes down too much on piston as the piston rises to TDC), and any less timing and its happening too late to take full advantage of the pressure.

Lambda is what all WBs measure, and it is a universal scale for all fuels. Lambda = 1 is stoich for any fuel. We know that for gasoline, stoich occurs at 14.7:1 AFR, so gasoline AFR = lambda*14.7. For E85, stoich is 9.77:1, so E85 AFR is lambda*9.77.

The easy way to know that we are referring to gasoline AFR when talking about E85, is that the AFR values we are mentioning are on the super lean side on the E85 AFR scale, so it has to be gasoline AFR scale that we are using.

You will never ever see MBT on 91 oct. Trust me I have tried. ;)

Yeah, I only used that example to help clarify when it is possible to reach it. Perhaps, I made it more confusing. :-(

I'm one step away from being done fiddling around at pump gas boost levels.

What I've done thus far with my E85 tune:

1) Lean out the AFR from ~11.4:1 up to about 11.9:1 (gasoline AFRs).

2) Increase the timing between 5000 rpm and 7500 rpm by somewhere between +2 to +4 deg.

Increasing the timing has not caused any more knock, but has had only a mild effect on power. Logs and HP charts are below. The minor increase in power with no increase in knock for a fairly large increases in timing is good evidence that I've reached and probably passed MBT without knock. People have been saying for a while that timing doesn't give much power with E85. I had assumed that this meant more timing would give knock, but now it looks to me that its the real issue is that its easy to pass MBT without knock using relatively low amounts of ign advance. This makes the "high boost" tuning strategy for E85 easy to understand.

I can't say much about AFR yet except that 11.9:1 gasoline AFR with E85 is no problem. I'm curious if a little richer AFR might slow the burn rate a bit and perhaps make a little more power. My final step before upping the boost will be to drop the AFR back down to about 11.3:1 to see what effect it has on power. If no effect, then back to 11.9:1.

E85 "low ign advance" + 11.5:1 AFR datalog
https://www.evolutionm.net/forums/at...hmentid=123330


E85 "low ign advance" + 11.5:1 AFR HP and TQ
https://www.evolutionm.net/forums/at...hmentid=123331


E85 "high ign advance" + 11.9:1 AFR datalog
https://www.evolutionm.net/forums/at...hmentid=123332


E85 "high ign advance" + 11.9:1 AFR HP and TQ
https://www.evolutionm.net/forums/at...hmentid=123333

Going down to 11.3:1 gasoline AFR caused perhaps a small loss in power, so its back to 11.9:1. Time to put new zip ties on all the little hoses and turn up the boost. I am going to start by increasing the boost by 1 psi across the rpm range. Good entertainment for the Labor Day weekend.

Great data, mrfred. It would be nice to make some charts of where you found MBT to be for various loads/RPMs. If someone could do that for an VIIII, that would be cool as well.

Obviously it's going to change depending on many factors and individual cars and setups, but it would be good data to have nonetheless, to know a ballpark estimate.

I think it would be best to be just below MBT, since you don't want to go over, putting undue stress on the pistons and rods.


Eric

Having watched it on the dyno, the ignition table that I posted follows MBT pretty close. We gained 4hp from 4* of timing so back down it went. The VIII will be -1 to +2 at peak boost typically ramp to about 10 or 11 by 6k (assuming something like a stock turbo) and then about 19-20* out the top (8k) from there. Any more than 20 doesnt do a whole lot so it leads me to believe thats about MBT. That was on E85 as well, but has been backed up even on E98.

The car in question with the posted map could have easily been pushed but it wouldnt have made much more and its already 28psi out the top ;)

I went searching the forums for E85 timing maps for IXs. Didn't find much. Here's what I got:

merkzu's E78 timing map:
http://ws.wamnet.com/~gryan/timing.JPG

What where the mods on that 9 mrfred? Seems a bit aggressive timing however I don't know the boost level.

Here is my latest timing table. Yellow squares indicate cells hit during a 3rd gear WOT run with boost peaking at about 24.5 psi and tapering to 20 psi at 7000 rpm. After a bit more testing, I decided to keep the higher timing values from 5500 rpm to 8250 rpm, as they do result in about a 10 whp increase in power compared to when the timing is 1 degree less in those cells. AFR is right at 11.9:1 from 3500 to 7500 rpm. Some runs are knock free while others show random knocksums of 1. All cells to the right of the yellow ones are still untuned. Green cells indicate cells hit during daily driving.

I must say, I really like E85 because of its awesome resistance to detonation and its cooling effect. I feel like my motor has much less chance of getting trashed when I hammer my car with this stuff than with 92 oct.

https://www.evolutionm.net/forums/at...hmentid=123387

I started pushing up the boost this weekend. No problem getting as much boost as I want in the 2500-5000 rpm range, but the best I can get at 6000 rpm is 23.5 psi, and by 7000 rpm, best possible is 20 psi. I suspect that part of the issue is the boost control setup being tapped out, but I think my intake setup is holding things up too. Still on the stock airbox with just a hole cut in the side of the lid. Still have the stock FMIC, but I'll be installing an ETS 3.5" FMIC sometime this coming week. Hoping I can get at least another psi from that. I hate loud intakes, so not sure what I'll do with the intake as the exposed element ones are very loud.