Different fuel quality in E-mix - what has to be considered?

[EmPeEs6]

A short question to all E-experts:

Apart from any knock issues - what (if so) has to be done/adjusted if you switch to a minor fuel quality in your E-mix, without having to encounter a power loss?

E.g. if you run 25% E85 in conjunction with 75% 93 gasoline (and adjusted maf cal) and switch to 91 fuel (maybe with a slightly higher E85 ratio of up to 30%), what has to be adjusted in the tune (assuming that the maf calibration for 25% can be reused):
ignition timing?
fuel injection amount?
...

The reason why I ask is that I just switched from 95 to 93 and now observe a substantial power loss.

I just want to ensure that this effect is not tune related.

[chaser27]

Originally Posted by EmPeEs6 A short question to all E-experts: Apart from any knock issues - what (if so) has to be done/adjusted if you switch to a minor fuel quality in your E-mix, without having to encounter a power loss? E.g. if you run 25% E85 in conjunction with 75% 93 gasoline (and adjusted maf cal) and switch to 91 fuel (maybe with a slightly higher E85 ratio of up to 30%), what has to be adjusted in the tune (assuming that the maf calibration for 25% can be reused): ignition timing? fuel injection amount? ... The reason why I ask is that I just switched from 95 to 93 and now observe a substantial power loss. I just want to ensure that this effect is not tune related.

With small amounts of variation in E, you will be fine assuming your MAF cal was good and timing table wasn't pushed to the absolute limit.

How do you know you are experiencing a "substancial power loss"? Is it just how it feels? This time of year, temps can swing back and forth and have a dramatic affect on power. Are you getting alot of KR?

[EmPeEs6]

Power loss with respect to comparable (similar iat, same road...) VD-graphs.

Although a compression and leakdown test was alright, boost is slightly higher (0.5-1 psi) and maf/load isn't lower either, VD calculates 10-20 hp less than before, which is somehow strange since the tune didn't change...

[chaser27]

Originally Posted by EmPeEs6 Power loss with respect to comparable (similar iat, same road...) VD-graphs. Although a compression and leakdown test was alright, boost is slightly higher (0.5-1 psi) and maf/load isn't lower either, VD calculates 10-20 hp less than before, which is somehow strange since the tune didn't change...

Same road? Uphill/downhill will change it. So will weight. VDyno calculates power based on how long it takes you to accelerate.

[EmPeEs6]

OK: same road, same direction, same starting point, same car weight ;-)

[Enki]

If you're running WMI as well, that alone should cover any missed timing you'd lose out from your effective octane dropping.

[EmPeEs6]

I guess the slightly higher E85-ratio compensates for the lower fuel quality, at least I do not get more knock than before (just occasional and less than 1). The influence of the wmi system should not have changed. It keeps idc below 100 (max is set to 110) and lowers my maximum bat by at least 15°C.

[Enki]

There's more than one person running 87/89 in combination with the corn without issues at around 30% mix I think

[EmPeEs6]

Originally Posted by Enki There's more than one person running 87/89 in combination with the corn without issues at around 30% mix I think

Well, that might be, but depending on the hardware settings fuel quality does matter, at least as long as you stay below a certain E85 ratio (50%?).
I run 27 psi and 20° of timing up top on a GT28 turbo with catted downpipe - this is much more "critical" than 20 psi and 12° on some catless GT30/GT35 turbo system with similar power output ;-)

[Enki]

If you're at 30-35% and drop to 25-28% I don't think it will matter in the slightest as far as knock prevention goes.

[Tokay444]

Does octane equal quality?

[EmPeEs6]

Originally Posted by Tokay444 Does octane equal quality?

Of course you're right, but the actual "fuel quality" did change as well since I switched from the best "premium" gasoline available to ordinary 93 from a noname gas station.
Moreover I'm not sure if octane/knock-resistance is the ony power relevant criteria, even if it is for sure the most important one...

[MSP6]

Octane doesn't "make" power, it allows for power. I was running 50/50 on 87 octane before switching to full E. I'd wager it's something else, temp, humidity, engine oil degradation etc. AFAIK 10hp is well within VD's error range regardless.

[Enki]

Ambient temps or head/tail wind could account for that as well.

[EmPeEs6]

Originally Posted by Enki Ambient temps or head/tail wind could account for that as well.

Of course, and because of that I always just compare log runs with almost identical measurement conditions!
BTW: I always do at least 3 subsequent runs to account for any "outliers" - and I do a lot of test runs for each tune!