Sorry if this is a repost, couldn't find any appropiate threads on this topic. Recently, I filled up with Sunoco 93 octane pump gas and there was a sticker on the pump reading "10% ethanol". At my local Hess station there was also a sticker on the pump reading "Contains Ethanol". I was just tuned by Shiv last week with 93 octane pump gas with no Ethanol.

If I start running the gas / ethanol mix with my tune, will I have any ill effects?

Any input would be appreciated. I'm running XEDE 1+

Thanks
-Mike

 

There are about to switch some places down here. My understanding, from what I have read, is that it is still 93 octane gas. Ethanol is more likely to absorb water. So, don't fill up when they (the gas station) is being filled up and the water in the tanks is being stirred up. Also, don't buy from small mom and pop shops that the gas sits for long times. Other than that, should make the EVO go the same.

 

The effect will largely be determined by how aggressive your current tune is. I've run 10% ethanol for as long as I've owned my car. Of course this also means that I've been tuned for 10% ethanol content.

I would think that it's unlikely to be a big deal to go from 100% gasoline to a 90/10 gas/ethanol mix. HOWEVER, if your existing tune is already on the ragged edge (read: aggressive timing, aggressive AFR [ >11.3:1 ]), then going to 10% ethanol might not be a wise idea.

If you have the SMART system, then it will, of course, keep you safe (assuming your wideband sensor is calibrated and working ). It would also allow you to datalog a couple of WOT runs and make adjustments to your tune as needed.

l8r)

 

Would SMART really keep you safe? The stoich mixture for ethanol is different than straight petrol....

 

Yes, SMART should keep you safe - assuming a calibrated and properly working wideband sensor.

The Bosch wideband sensor measures actual AFR in terms of lambda. The sensor will always give a lambda of 1 at the actual stoich ratio.

So, for example, if you are tuned for an AFR of 11.0:1 on 100% gasoline, this would translate to a (rounded ) lambda value of .75 (11.0/14.7) . The SMART system does not actually tune for the AFR number, it tunes for a voltage reading coming from the LC-1, which is generated from the measured lambda value. In contrast, the AFR numbers that we all see on AFR gauges are actually calculated based on an assumed stoich ratio and the lambda value.

So, knowing this, if you add some ethanol into the mix, then at a 10% mixture, the stoich value changes to ~14.13:1 and the wideband sensor will report a lambda of 1 at a 14.13:1 AFR. Since the SMART system is actually tuning for .75 lambda, it will end up targeting an AFR of 10.59 (14.13 * .75).

Now to confuse things even more ... if you had the XD-1 gauge it would still display an AFR of 11.0:1 ... why? Because it is calculating its values off an assumed stoich ratio of 14.7.

This is also why you can use a wideband to simply tune for your target AFR when you are spraying alky. When the stoich ratio changes, the lambda values will automatically keep up.

l8r)

 

So what you're saying is that the target A/F percentage in the exhaust flow is the same regardless of the fuel you're running?

So if for petrol the target a/f is 14.7:1, that is the ratio of air to fuel entering the engine, but the lambda reading in the exhaust is 1, and with ethanol the target ratio is 9:1, and the O2 reading in the exhaust is still 1? I don't see how that works, but that is how I'm understanding it....

 

^ yes, you got it.

Optimal power has been shown to be made at similar lambda values for gasoline, ethanol and methanol. There are some minor differences in terms of optimal AFR and bigger differences in terms of how much timing advance you can run between the fuels, but in terms of going from 100% gasoline to a 90/10 mix, those are negligible.

Some further reading: http://www.innovatemotorsports.com/resources/news3.php
and: http://www.innovatemotorsports.com/f...ead.php?t=3175

l8r)

 

Sweet, thanks man

 

Thanks for the great information. I feel better now. You would think if they are cutting the gas with Ethanol the prices would reflect it.

Thanks
-Mike

 

It is reflected in the greater profit margin.

l8r)