Carbs and Gas Smell Options

[ClayPerrine]

Porsche 356 has carbs and a fuel shutoff underneath the dash.
With today’s fuel, I find it best with any carbed engine to turn off the fuel supply while the engine is running and let it suck the carbs dry.

Also, when going to a car show, simply putting tennis balls into the intake stacks helps a TON to keep the hot fuel from evaporating and smelling things up.

Today’s gas has a lot of ethanol. That evaporates really fast.

Rich

(IMG:style_emoticons/default/agree.gif) This is why I use alcohol-free gas

There is a fairly new station near me that sells ethanol free gas. We make sure to fuel the factory six there and nowhere else unless forced to.

But it is only 90 octane, so we have to put in octane boost with each tank. But it is worth it.

[Jamie]

Porsche 356 has carbs and a fuel shutoff underneath the dash.
With today’s fuel, I find it best with any carbed engine to turn off the fuel supply while the engine is running and let it suck the carbs dry.

Also, when going to a car show, simply putting tennis balls into the intake stacks helps a TON to keep the hot fuel from evaporating and smelling things up.

Today’s gas has a lot of ethanol. That evaporates really fast.

Rich

(IMG:style_emoticons/default/agree.gif) This is why I use alcohol-free gas

There is a fairly new station near me that sells ethanol free gas. We make sure to fuel the factory six there and nowhere else unless forced to.

But it is only 90 octane, so we have to put in octane boost with each tank. But it is worth it.

I've been running my 914 on locally available 90 octane no ethanol fuel for some time, but wondering about using it in my new Cayman 718 turbo? How about alternating fill-ups to keep the octane up? (IMG:style_emoticons/default/confused24.gif)

[flipb]

I've been running my 914 on locally available 90 octane no ethanol fuel for some time, but wondering about using it in my new Cayman 718 turbo? How about alternating fill-ups to keep the octane up? (IMG:style_emoticons/default/confused24.gif)

I'm not sure what the advantage would be of putting ethanol-free fuel in a modern car. They're designed for the blended fuels. And being fuel injected, evaporation isn't a concern.

[brant]

I've been running my 914 on locally available 90 octane no ethanol fuel for some time, but wondering about using it in my new Cayman 718 turbo? How about alternating fill-ups to keep the octane up? (IMG:style_emoticons/default/confused24.gif)

I'm not sure what the advantage would be of putting ethanol-free fuel in a modern car. They're designed for the blended fuels. And being fuel injected, evaporation isn't a concern.

Unless storage or length of time is factored in
Pump gas with ethanol has less than a month of shelf life
I heard somewhere it may be under 3 weeks

Ethanol can still gum up injectors
So the frequenc of fresh fuel (how many weeks the car is not driven) can definitely factor in

[mmascari]

By the way, for anyone that cares, the smell of gas was from an actual leak under the tank. It leaked on to a carpet that I had under the car. The carpet was saturated. Luckily no fire. As soon as the leak was fixed I no longer have any gas smell

[Rufus]

“I'm not sure what the advantage would be of putting ethanol-free fuel in a modern car.”

Slightly better mpg due to slightly higher energy content. Whether worth the price difference is questionable depending on how great the difference is.

[GregAmy]

Prooooobably won't make any difference on our fuel economy without wideband feedback?

In a modern car with AFR feedback, the ECU will detect a lean condition due to the presence of ethanol and inject more fuel; our stock D- or L-Jet fuel system is injecting the same mass of fuel regardless what we put in the tank.

I can't offer if "energy content" would be significant, given I don't think any of us are sensitive enough to notice it and make any change in how we drive the car.

For us, ethanol-free would actually slightly reduce emissions (if driven the same) but at the expense of the issues with ethanol being in our older fuel systems.

[Rufus]

My quick search said the difference is slight, but “measurable”. Don’t know if in a lab, on a dyno, or by a consumer.

And more food for thought: Lambda=1.0, stoichometric, is A/F=14.7 for E0; 14.0-14.1 for E10, and 9.8 for E85. The greater the ethanol content, the greater ratio of fuel to air for Lambda = 1.0 which the narrow band O2 sensor seeks to run at.

[Rufus]

Prooooobably won't make any difference on our fuel economy without wideband feedback?

In a modern car with AFR feedback, the ECU will detect a lean condition due to the presence of ethanol and inject more fuel; our stock D- or L-Jet fuel system is injecting the same mass of fuel regardless what we put in the tank.

I can't offer if "energy content" would be significant, given I don't think any of us are sensitive enough to notice it and make any change in how we drive the car.

For us, ethanol-free would actually slightly reduce emissions (if driven the same) but at the expense of the issues with ethanol being in our older fuel systems.

I pretty much agree.

The specific gravity of E85 is .79 vs .72 - .77 for pump gas.

I’m no carb tuning expert. But if E85 has a slightly higher density than pump gas, and I’m thinking right, the A/F ratio with E85 would be slightly higher (leaner) than with E0 at the same carb calibration.

As far as FI with closed loop A/F control using a narrow band O2 goes, the A/F will operate at stoicometric (Lambda = 1.0; the ratio where 100% of both air and fuel are consumed during combustion) for a variety of gas / ethanol blends as long as the fuel system has sufficient authority (range of control adjustment) to meet ECU demand.

[Rufus]

A couple more thoughts to share on venting a 914’s gas tank for use with carbs and without the evaporative emissions control system …

This’s my plan. When I get my /6 up and running, I’ll report back. I hate the smell of gas in the garage.

Below is a photo of what I ran on my ‘67 Vette for years. Tank venting was never a problem, and in the 5 years it was in the garage under bedrooms there was no gas smell. Note the approximate size of the vent hole; 1.5-2mm at most?

A 914’s difference is the tank is under the frunk lid, where there are pathways to the cabin at floor level. Also consider that gas vapors are heavier than air, and sink to the floor.

So I’m stuffing the cut off and deburred big threaded end of a ball (basketball, football, volleyball) inflator inside the vent hose. Will locate it at or before the uppermost point as vapors leave the tank / expansion tank and then travel downwards to where they exit under the car. Hopefully this will lessen vapor escaping thru the vent tube.

And this’s how VW configured the tank vent hose in Bugs of the ‘60’s (pic from The Samba), before evaporative control systems. By using the difference in density of air & fuel vapors as a natural check valve kinda like a kitchen sink drain trap in reverse

[r_towle]

By the way, for anyone that cares, the smell of gas was from an actual leak under the tank. It leaked on to a carpet that I had under the car. The carpet was saturated. Luckily no fire. As soon as the leak was fixed I no longer have any gas smell

Yah, this might have been a different thread if you started with that.

Lol