Gas additive to stop percolation-boiling point

[Gary C.]

During the FI Road Tour at stop overs there were several discussions about fuel additives to aid with gas percolation problems. Only problem we had was after stop and go traffic while going through small towns on the Road Tour in a '57 FI Corvette when leaving town and accelerating there was some hesitation-slight bucking until about 1500 RPM. Hesitation disappeared after car was going and fresh air was again moving into the engine.

Some of the Road Tour members were using Marvel Mystery Oil (kerosene base), diesel fuel or additive sold by Podell in the fuel.

Have searched lots of forums and results were mixed.

Question - short of Aviation Gas, is there any additive that will curb gas percolation?

Appreciate your input. Thanks in advance. Gary....

[Jerry G.]

Re: Gas additive to stop percolation-boiling point

The short answer is no there are no additives that I'm aware of the will help with this percolation problem. The Ave gas or racing fuel are refined differently. They are a different "cut" out of the barrel of oil and have a different partial pressure and boiling points. it's a problem with todays fuel. Elevation also affects this problem. I live at over 5000 feet and racing fuel has worked best for me.

[Duke W.]

Re: Gas additive to stop percolation-boiling point

Like in the case of motor oil and coolant there are no magic fuel elixirs.

Percolation problems are the result of current gasoline distillation curves, which have more components, including ethanol with boiling points around 170 F. No additive will change this - only a change is the distillation curve will have an effect. Avgas and race gas are blended with fewer components in this range.

About all you can do is figure out a way to keep the spider and fuel meter cooler. At low load the fuel spends more time in the fuel meter bowl and spider before it gets to the engine, so it has more time to absorb heat, and the same applies to hot soak after shutdown.

Modern EFI systems pump more fuel through the rail than the engine can consume and the excess is routed back to the tank. This essentially functions as a fuel cooling system. Some recent vintage cars even have fuel coolers that route the fuel through a small heat exchanger that receives cold liquid freon when the AC is on. The above plus constant fuel rail pressure of at least about 40 psi prevent percolation problems in modern engines.

Duke

[Gary C.]

Re: Gas additive to stop percolation-boiling point

Any ideas on how to cool the fuel line and fuel meter? It would be tough to put something between the spyder and the intake. Problem wasn't too bad as temp on Road Tour was between 85-90 degrees. Assume percolation will get worse with higher temps in the 90-100 degree range. Tying to think ahead about driving to St.Louis next summer for Flight Judging at the Convention.

Appreciate your input. Thanks, Gary....

[Duke W.]

Re: Gas additive to stop percolation-boiling point

There have been some schemes, but I'll leave it up to the FI guys to discuss them and the results.

Duke

[Clem Z.]

that is why i laught when corvette owners with

40/50 year old fuel systems think they are going to run like they did back in the 50s and 60s.the new FI cars do not even have the return line for the fuel in the engine compartment because of the heat. they use a very complicated system in the tank.

[Denny J.]

Re: Gas additive to stop percolation-boiling point

I'm not a FI guy but to me rather than trying to cool the fuel,Why not try to get the heat out of the engine bay.I have have seen boys with ICE bags to cool it down,the FI unit also driving with the hood open.To me thats no air movement.I would look to the front of the car.Sorry I will step out also.Denny72

[John D.]

Re: Gas additive to stop percolation-boiling point

Gary, Chuck Berge drove to the National in CA to VA a few years ago in his 57 FI car with a '4520 unit on it. He told me he had NO problems with perculation. Chuck clams he used wooden clothes pins on the two fuel lines going from the engine fuel pump to the fuel meter. I believe he said they were 4" apart. If you want to know any other info contact him.
Old Marvel Mystery oil seems to help a little. How did the fellows on the road tour do that used it??? Notice that when Rick Alshire got to Marlborough he put 3 gallons of good racing fuel in his tanker that Dick Capello got him. That was for his PV.
AS far as answering the rest go to the archives as we talked a lot about this problem this past summer. It's only going to get worse-not better. Now All I see is commercials pushing corn fuel and I just cringe. Going to be thousands of FI's out there that are going to need work if they use it. Pumps will start leaking, o'rings will start leaking, axle link grommet will swell up like donut, main diaphargm may not like it. Etc. etc. Good thing I don't have to start now and do another 40 year tour of duty. Course we are coming up with some parts now made from viton that will cure most of the problems that ethanol is going to cause. In the SW corner of PA I never saw so much field corn being planted. I mean it's everywhere. Good luck, John
By the way do you have the one piece gasket between the base plate and the FI? Hopefully. Barry Holmes if you are looking in please help Gary and tell him your invention. John

[John D.]

Re: Gas additive to stop percolation-boiling point

Barry Holmes has a friend who has commercial hi-tech insulation. He described it to me over the phone and said it resembled fiberglass matting. Anyhow Barry got some and jammed it between the base plate and the one piece gasket on his 62 and he said he has had ZERO problems with 93 octane. THis is on his 62. So maybe Barry can help you from here. I have been thinking of getting this stuff and offering it to everyone-but that wouldn't be fair as it's his idea. But if I were him I would be selling a kit for sure. WOn't work on the midyears though. But maybe it would with some kind of brainstorm.
Just remembered. COntact Brian Futo Gary. Old Brian came up with a similar approach with some success. He lives in the dessert you know so if it works in AZ it will work in TX. Course nothing would work up here right now. Weather is the pits. Hi-humidity and supposed to be in the 90's all week. Take the hood off as Dennis Clark said-could have been Clupper though-take the hood off and you won't have any problems. One thing we all forget. This old system is crude. Just like Clem said. I mean it's the ABC's and thats it. If I had a nickel for every call about this........... John

Gary-want to have some real fun with your car. Put some aviation fuel in it.

[Verle R.]

Re: Gas additive to stop percolation-boiling point

John,

A significant challenge with the E85 alcohol fuels will be configuring the FI unit to deliver significantly more volume of fuel. About 30% less energy in the same volume of alcohol so you will have to richen E85 up about 25% over gasoline. That is after you address all the items you mentioned.

25% richer (less fuel mileage)....is E85 at least 25% cheaper than gasoline?

How much would it cost without government subsidies?

Some studies find more petroleum is consumed in producing a gallon of ethanol than the ethanol produces.

But remember, it is great! Politicians say so.

Verle

[Clem Z.]

since the oil pump heats up the oil in the engine

does the pressure pump in the FI do the same thing?

[Clem Z.]

i hit the post button too soon

what i wanted to post is how about using a small power steering cooler in the line between the engine mechanical pump and the FI float bowl to cool the fuel before it get to the gear pump

[Gary C.]

Re: i hit the post button too soon

Clem, good idea about adding the cooling finned line. However, need to keep stock for Flight Judging. Had thought of using rubber hose to cover lines and then wrap with "hot rod" foil insulation available to swap meets. Used the "hot rod" foil insulation on the floor of my '64 to cut the heat and it worked good. Thank you for your inputs. Gary....

[John D.]

Re: Gas additive to stop percolation-boiling point

HI Verle, Gads I wasn't referring to the E85 stuff. Just the 10% crap being added to our favorite fuels without us knowing. Yes I know it's supposed to be labeled on the tanks. I can remember going to the BG and running on fumes the way back until I hit the IN line to feel up with non ethanol in my tow vehicle.
See you made it back in one piece. How did the fuel car run on the road tour??? John

[Verle R.]

Re: Gas additive to stop percolation-boiling point

The car ran fine as far as it went.

I left it in Carlisle, flew home and will fly back to take it to Corvettes at Carlisle. See you there.

Verle