I'm currently tuning for the GASOLINE CALIBRATED A/F ratio of 12.3:1. With the cold weather we've been having here in the midwest I actually saw my first knock since switching to E85. I'm running 31 psi peak tapering to ~26 psi and saw 3 counts of knock near peak boost. This was at:
4000 RPM
Boost of 30.6 psi
Gas Equiv. A/F ratio of 12.3:1
ignition timing of 5 deg
according to Data Log Lab 463 lb-ft of torque

-Paul

 

you know that make sinces, its just like tuning on race gas..

 

LOL, thats great. Only a 3 count since your E85 journey began.

I gotta get that Data log lab familiarized.

So I never reported my results on mixing the E85 for octane increase without ECU change.

VIII, with TBE, MBC, ECU flash for 93oct and 23psi. with 1 gal E85 in 6 of 91oct the boost turned down to 20psi. The car liked it. With the boost up it wanted to knock at boost peak.

IX stock, did'nt like it. Started knocking hard about 4k.

 

The reason you got some knock is its probably winter blend E85 which is a little more gas than 15%.

 

Every time I see you talk about your E-85 results, it makes me want to convert my car tomorrow.

That's just awesome to say the least.


Eric

 

I believe I've been on winter blend since I converted as the average highs here were under 40F when I started. With it being below 10F last night my boost was hitting a bit higher which I think was a likely cause.

-Paul

 

Hmm, good observation.
And the cold dense air also would increase his boost on the same adjustment?

Next time I'm by the E85 station here I'll ask when they swich mixes. (If they know or at least give me a phone #)
Its probley later here in Las Vegas then in the midwest though.

I did want to ask what dutey cycles are you running with the 1000cc injectores? You still run the Walbro 255 pump right?
Thanks

 

The Duty Cycles are interesting. In the pull I did last night I passed 100% IDC at 6700 RPM. At that point my boost was at 25.7 psi and my A/F ratios were at a gasoline calibrated value of 12.2. The attached graph shows the pull. Everything except the IDC is scaled to the left axis.

 

Wow, maybe you needed the 1200 or even 1600's unless you can lean it out more without issue. You have your injectors scaled to 550?
Actually if it doesn't lean out over a LONG hard 5th gear pull your probley OK.
I ran one of my subies like that and it would only lean out enough to cause knock if I was going about 150mph. Basicly maxing the car out for a long time I could see the AFR's gradually go up point by point.

 

I think I may try a twin fuel pump setup and see if that lowers the duty cycle. My current issue is that the Full Blown setup is a little pricey and I can't send my fuel pump housing to Buschur because my Evo is my daily driver. I've been looking into modifying my own fuel pump housing to hold two Walbros. If I'm looking at things correctly I should be able to do the full modification for ~$50-$75 (I already have an extra Walbro). I'm very anxious to see if that type of modification will help.

-Paul

 

i don't believe NV gets winter blend, some states do like in the midwest and east coast

 

Thats what I did on my subie. The twins didn't work for whatever reason so I bought the Walbro modified from BR. That has worked fine so far.

 

I could just about guarantee that your single walbro is losing fuel pressure up top and a twin pump will lower your duty cycles. I just did some quick math and proved that you are most likely compensating for you fuel pump not keeping upwith a 1:1 rise in fuel pressure and therefore have to run larger pulsewidths (duty cycles) for your injectors.

The only reason I can't guarantee this is because I don't know what the white rabbit turbo is actually capable of flowing...I have never seen it's compressor map. But, I checked two ways and both ways suggest that you are losing pressure.

Keep reading for the long boring math:

1. To get a rough estimate of how much mass airflow you were pushing you can use the equation for airflow through an engine:

airflow through engine (CFM)= rpm*cid*ve*PR/3456

6700*122*.9*2.75/3456=585 CFM
585*.0756=44.2 lb/min

There are a few assumptions in this equation, like standard temperature for the CFM to lb.min conversion and .9 VE, but roughly, at that RPM and boost, you should be flowing around 44 lb/min mass airflow through your 2.0 L engine. I think that falls in line with what the white rabbit is capable of, so that makes sense.

2. Now, we can see how much mass airflow maxing out 1000cc injectors would indicate:

desnsities at 60F
ethanol 49.3 lb/ft^3 = 1.74*10^-03 lb/cc
gasoline 42.5 = 1.5*10^-3lb/cc
e85= 1.704*10^-03 lb/cc

1000cc injectors at 100% duty cycle =
4000cc E85 = 4000*1.704*10^-3 = 6.816 lb E85

You said that you were running at a gasoline calibrated AFR of 12.3, so in lambda that is 12.3/14.7=.8367

Stoich for E85 is ~9.765
Your true AFR for E-85 was (12.3/14.7)*9.765= 8.17

So, to find how much mass airflow this AFR indicates, just multipy your AFR by mass of fuel:
8.17*6.816=55.7 lb/min mass airflow


So, I highly doubt that the white rabbit can flow 55-56 lb/min of air, that's well past a 50-trim, a 20gLT and most gt 30s, like the 3076. And this was at 6700 RPM to say the least.

Also, the fact that this 55.7 lb.min was much larger than the quick estimate of around 44lb/min of airflow at that point, that is showing me that your fuel pump is losing pressure and to feed enough fuel into the engine you must compensate with larger than normal injector pulsewidths for that mass airflow, and thus the reason why you need such large injectors.

So, to sum it all up, I think you would definitely benefit from a dual pump setup. I think you could easily drop your duty cycles (using a little math again) for your 1000cc injectors to more around 80% at this same RPM and airflow.


Eric

 

I forgot when he started his E85 tuning. Winterblend E85 can actually be 30% gas to fuel (E70). If for instance he started on the last bit of actual E85 whatever station had and they start mixing in the E70 then the tune starts to alter rather fast.

Cold air doesnt increase boost, but the density at the same boost level is what can cause an issue. Summer tunes can quickly be too lean because of more available oxygen.

 

^-^ +1,

Only problem is we don't have no stinking stations in georgia yet (there are a few, maybee 5 but only one is open to the public and it like 50 miles from me).