Flex fuel with EFI, what CR to go?

[IhmeJanneFIN]

As title says, has anyone experimented with flex fuel or even plain E85 on these old oilboilers with EFI and what CR people have used?

I know that with E85 I could run OEM or even higher than stock CR and still run high boost, but petrol would like the lower CR better with boost.

Powerwise I will be making the most power with E85 & high boost and propably would drive quite much with it near home, as my nearest petrol station has it. But I will also be running pump gas with when I go touring with the bike, so that I could go further between gas stations.

As I am currently building my new engine to my turbo teapot (GSF based 1216 with oem busa pistons and Maxpeeding rods), I will be running EFI on it (Maxxecu btw) with big enough injectors so I have the possibility to run full flex fuel with it and three different boost maps which would all take acount the amount of E85 in the system.

With different height spacers and heads (I have two different DOT heads and -92 GSXR shim head to choose from) I could achieve CR between 8,5-10:1 if my calculations and data entry to CR calculator are correct.

With 8,5:1 CR would propably be best for plain pump gas and high boost, but would it be too low for E85?

Something near 10:1 I think would be too much for pump gas on even low boost levels, but would be totally fine with E85.

So is the in between say 9-9,5:1 the way to go with flex fuel?

What do you guys think would be a good CR to go? Any opinios and more information on the topic are welcomed.

 

Edited February 3 by IhmeJanneFIN

[Blower1]

I had 11:1 CR on my supercharged 1327cc EFE and E85 & flexfuel. The boost was 0.8 bar and water injection in to the supercharger.

Now it´s 10:1CR 1360cc and run mostly with 98 gasoline and same boost as before and water injection.

Both fuels working fine, but engine feels a bit crispier with 98 gasoline than with E85.

Engine runs cooler with E85.

[IhmeJanneFIN]

29 minutes ago, Blower1 said:

I had 11:1 CR on my supercharged 1327cc EFE and E85 & flexfuel. The boost was 0.8 bar and water injection in to the supercharger.

Now it´s 10:1CR 1360cc and run mostly with 98 gasoline and same boost as before and water injection.

Both fuels working fine, but engine feels a bit crispier with 98 gasoline than with E85.

Engine runs cooler with E85.

Good to hear, so I am now tempted to go something like 9,5:1 CR now with a DOT head. I am also planning on running charge cooling, but I will try the air to water method to see if that would work for me. I don't have any room for an air-air intercooler at the front as I am running full fairing and dual oil coolers with high mounted turbo for gravity drain. But I do have room for a radiator at the back under the seat and should be able to fit a charge cooling element inside the plenum (still working on that though).

[Arttu]

I have currently about 11:1 compression ratio on my air cooled GSX. I have boosted it up to 1.2 bar on E85 without issues. I have water injection for charge cooling but I have run it also without water on dyno and haven't noticed any issues. So it's more for peace of mind I would say. I have also full flex fuel setup but I haven't run this engine version on gasoline yet.

Before the latest engine rebuild the compression was about 10.5:1 and that I run on gasoline too. Boost on gasoline was limited to 0.5-0.6, lowest that my internal waste gate allows.

So in your case I would probably aim for 9.5-10:1 compression. That should allow moderate boost on gasoline, especially if you use charge cooling. And on E85 it should be good for over 1.5 bar.

[IhmeJanneFIN]

10 hours ago, Arttu said:

I have currently about 11:1 compression ratio on my air cooled GSX. I have boosted it up to 1.2 bar on E85 without issues. I have water injection for charge cooling but I have run it also without water on dyno and haven't noticed any issues. So it's more for peace of mind I would say. I have also full flex fuel setup but I haven't run this engine version on gasoline yet.

Before the latest engine rebuild the compression was about 10.5:1 and that I run on gasoline too. Boost on gasoline was limited to 0.5-0.6, lowest that my internal waste gate allows.

So in your case I would probably aim for 9.5-10:1 compression. That should allow moderate boost on gasoline, especially if you use charge cooling. And on E85 it should be good for over 1.5 bar.

Excellent info as usual Arttu, this is reassuring me to continue my engine build how I have thought to go.

I currently have three springs to my external wastegate, 0,2 bar, 0,5 bar and 0,7 bar, so I will try to use the 0,5 bar as the base and run gasoline with only that and use my 3 port boost controller to achieve higher boost with E85.

If my preliminary calcultions are good I can achieve the 9,5-10:1 CR with my 750F DOT head and correct heigth spacer and still have about less than 1 mm squish. Still have to do the dry build, but as family man garage time is quite limited, so everything takes ages to finish .

It's funny though, here we are three finnish guys talking about flex fuel in english But this is very good info for all bike builders, so it is good to have this talk here

[Blubber]

2 hours ago, IhmeJanneFIN said:

 

It's funny though, here we are three finnish guys talking about flex fuel in english But this is very good info for all bike builders, so it is good to have this talk here

Would a sauna be a better place for this conversation? 

 

 

[IhmeJanneFIN]

1 hour ago, Blubber said:

Would a sauna be a better place for this conversation? 

 

 

Even better with few beers in sauna. Thats how the wild ideas appear to us Finns

[Fredrik_Steen]

Since you use EFI i would say go for compression and if necessary drop the ignition timing some degrees when pushing high boost on pump fuel.

Edited February 4 by Fredrik_Steen