Given the 997.2 is a returnless system, if I add a couple gal of E98, how do I ensure the fuel in the tank is mixed properly?

In my GTR it's a return based system so it will automatically mix it all up.

What's the shape of the fuel tank in the 997.2 and are there a bunch of weird chambers where fuel may not be mixed properly?

 

First you'll need the tune adjusted for it, otherwise you'll run lean and set of fuel trim codes among other possible nasties.

Once reflashed and filled up let the car idle or cruise around for 10mins should be good. We actually ran a test with an ethanol analyzer on the BMWs to monitor ethanol concentration just before the HPFP and ~10 minutes seemed to be a safe time after filling up to get going with it.

Dzenno@PTF

 

Ok thanks Dzenno. But is the shape of the fuel tank in the BMW similar to the 997.2? I'm worried about weird zigzag chambers etc.

2 gal of it in a 16.6 gal tank - closed loop should take care of it no problem I would think? I know it's not absolutely sure but at least we can datalog with Cobb and make sure?

 

Also I wouldn't be doing it to try to get an E20 tune for extra boost/timing/power. It's just for say, a super hot day and you're going road racing on a Cobb OTS or custom tune and you want to get your knock values down.

 

Very different tanks and to be honest I've never had a chance to look in there myself but SRM can provide input there.

AP is your friend for sure and always be logging Watch your STFTs, Rail (HPFP) pressure and knock. AP's 6 gauge layout with peak recall helps.

 

Dzenno, thanks for answering technical questions on the forums. You're one of the very few that do (or maybe it's b/c others are incapable).

Get that fuel system going and let's turn up the 997.2!

 

I'm used to sharing info out there coming from the BMW world. In this neck of woods though for the past 2 years its like pulling teeth to get some data sharing happening with people. Hoping that'll change soon and others will join in.

We'll start with the bucket change first and see where we get. Then the rail will be added. Good times finally for the .2s!

Dzenno

 

Should mix quite rapidly.

If you are talking about a Turbo it has a split tank, well, a tank with two basins, one on each side of the front diff and relies upon siphon jets one in each basin to pick the fuel up and supply the pump. The siphon jets spew the fuel and stir it up. There is also some excess fuel expelled by the fuel pump with the intent of washing fuel over it to help keep it cool and this works to keep the gasoline mixed up/blended too.

 

Bingo. The venturi jets do a great job of mixing everything up. With the DI BMWs, it's very easy to see when the E85 mixture reaches the combustion chamber as dynamic timing rises a large amount (if mapped for such anyway) almost instantly when it happens. I used to use my JB4 with gauge commands and put timing on the oil temp gauge in the cluster. A couple stabs of the throttle until I saw timing ramp up from around 5 deg to 13-14 and off I went. It usually took no more than 5 minutes for the fuel in the lines to be burnt and the good stuff from the tank to reach the injector.

 

DI BMWs have the venturis as well from the factory that are there to keep the bucket full. I recall some guys way back playing around in there and removing them due to tight fit only to have fuel starvation issues shortly after and going back to putting the venturi back on.

Dzenno