nuclearfishin

With my new GIAC tune and the race program set to run on 110 octane, I need to find the most efficient way to swap gas. Will siphoning the gas get enough out so as to not dilute the 110 gas? Through a search I found other p-models have a drain plug on the tank, is that true for the 997.1tt? Some people mentioned they ran their tanks down until the gauge said less than 5 miles before empty. I always heard that could be rough on the car and you shouldn't do it. The 110 octane is expensive so I want to find the best way to drain the tank and only have to add 2-3 gallons to get me through an event. Any advice would be greatly appreciated. Thanks!

Macster

Wait. You own a 997 Turbo, have a tune, and want to save a few bucks (and risk a nice car fire/garage or house fire) to save a few bucks of race gasoline?

Disconnect the battery. Remove the fuel pump. Siphon the fuel out as far down as you can get the level.

Hope no static spark ignites the fumes.

Man just run the tank down til the low fuel light comes on, then fill up with enough 110 gasoline to get you through the event.

Done.

Igooz

I can't imagine that you would need to run it that low to still get a pretty high "average" octane. If you have 2 gallons (93 oct) left and you add 12 gallons (110) your average will be 108 (assuming linear math)...

wait a minute...you are the mathematician and not me!

Kevin

Please realize that there is ZERO way to siphon the fuel out of this tank down the fill door. You would have to remove the fuel pump/fuel gauge assy.

The fuel system in the 997TT has 2 pumps in a swirl/surge pot that sits above the front diff. Fuel pressure is diverted to two venture lift pumps to suck the fuel out of the two side pods.

I would try to drive the car as far as possible to get most of the fuel used. Try to avoid running out of fuel, and WOT..

Kevin

Please note, that running a few gallons of fuel on a empty tank, can increase your risk fuel starvation with the way that the pumps are plumbed. Anotherwords, the fuel pump is 12 inches above the fuel level in your tank, trying to USE fuel pressure to create the venturi effect to suck the fuel from the two pods. As you launch the car, you put your engine at risk.. I wouldn't track my car with less than a 1/2 tank of fuel! From memory the fuel level has to reach 1/3, to equalize over the two pods and flow into and over the top of the swirl pot... Below that level you are running on full venturi mode...

nuclearfishin

Thanks guys, that's a lot of good info. Unfortunately I can't find 110 unleaded at any of the tracks around here, so I have to buy and haul it in 5 gallon pails which makes the price close to $25 gallon. That won't be a regular habit but a couple times a year it will be fun to run the race gas tune. I guess I was hoping I could drive to the track (approx 100 miles) on 93 octane and then have an easy way to fill up with the pails so I don't have to burn it all getting to the track, but obviously it's not worth risking the engine.

nuclearfishin

Fixed it for you.

Kevin

FYI, I have seen guys empty acetone or paint thinner 1 gallon metal cans and fill and label with race gas. I think that you can squeeze 10 to 12 gallons for the trip.

Igooz

Time to buy a new Dually and an aluminum enclosed trailer...

Macster

Oh that's right. I forgot the Turbo had the two basins with the siphon jets. Looks like it is run the fuel level down and then fill up with race gas.

Macster

If this was Russia that would be a nice recipe for a horrible dash cam video on LiveLeak.