Gas Weirdness?

[70rr-brian]

OK, normally I run BP or Shell premium (93 octane) gas in a Roadrunner with the following:

383/496 Stroker
4.310 Bore
4.250 Stroke
Edelbrock RPM Perf heads
NGK V Power plugs
MSD Ignition (Pro billet dist, 6al, 8223 coil)
Stock Mechanical Fuel Pump
Edelbrock dual plane intake
850 QuickFuel Carb
dur @ .050 I-254 E-260 (comp cam)
1 7/8th" TTI headers
2.5" dual exhaust
Timing 36 @ 3500
10.5 compression

It puts out 555hp with 611lbs of torque.

This car is not a trailor queen and sees about 200 miles per week give or take.

Recently, my old lady bit#hing about the gas prices, wanted me to switch to Speedway/SuperAmerica gas because she has so many points built up that I could get like 50 cents off per gallon for like 10 full tanks worth of gas. Against my better judgement I decided to play along and give it a try. What the hell its $100 of savings.... And a lot less pianful on the ears.

I have been through 4 tanks so far. To be honest I haven't noticed any performance hits and just took all the plugs out to inspect them and they are the poster children for the perfect plug condition.

Here's the reason I started to get concerned.... The back bumper all around and above the exhaust is speckled with gas droplets... I am assuming gas droplets, if you try to wipe them off the chrome bumper it smears just like gas would and it smells like gas.

It doesn't smoke at all and the exhaust scent doesnt smell like its running rich and the plugs are absolutely perfect....

This motor has about 4k miles on it and runs like a scalded dog even with the new gas in it but I have NEVER seen any crap like that before without additonal evidence of it running rich.

Any ideas?

 

[Mopar To Ya]

Assuming there never were any droplets there from other fuels, you would think it isn't related to your gas brand change. If the deposits are hanging around for more than a few seconds without evaporating, my guess is the droplets are oil getting pulled into to the low-pressure "void" around the bumper as you go down the road. There would be other factors effecting this outside the car like atmosheric pressure, due point, etc. I am not familiar with the fuel you switched to but I wonder if it is washing the cylinders when the motor is cold more than your old brand and oil drops are condensing on the bumper more than before. I would think any engine/fuel combo could do this if you fired up and drove off with a fairly cold motor. Any 500 cuber with forged pistons must throw out quite a plume warming up (you usually just don't see it). It would be inmteresting to have some IR probe numbers off the headers from one fuel to the other. Did you change to a synthetic oil? Doesn't sound like a problem other than the mess. My experience with most any CDI style ignition is once the engine is warm, your plugs would probably burn well enough to run on a can of polyurethane (almost). I fog my engine each winter and install old junk plugs for storage. When I look at my NGKs after fogging (it won't stall, I have to shut it off) they look great too. This is an intersting one, I'll be curious to see what more you here.

 

[Cranky]

Did you actually look at the back of the car when you were burning the other gas? The droplets are usually caused from moisture in the exhaust system and happens when going from dead cold to hot over a period of several minutes and driving it shortly after startup.

 

[70rr-brian]

You are correct in assuming that this problem didn't happen with the BP and/or Shell gas. I know this because I wash the car once per week if it needs it or not. I would have noticed it. This is a solid roller motor. I don't normally let it idle for extended periods. But not having a choke on it I do let it get to about 150 degrees before I take out. So I guess on first start there is some extended idling. But I don't lose any sleep over this since the oil pressure is 50+ at idle upon first start.

I am not running anything special in so far as oil is concerned. I just use conventional 20w50 Valvoline and that hasn't changed.

One other thing I have noticed is... If I just idle the car the droplets never really appear. It must be happening under normal driving or WOT conditions. After a 10-20 mile ride is when I notice them. But at no point do I notice any black plumes of smoke coming from the tail pipe.

But Cranky you are right, there is some condensation that will inevitably come out when it is warming up intially after sitting over night or a day or two. That has always been the case living here in the humidity belt but until the fuel change I have never noticed this speckling before.

 

[Cranky]

I ran Shell gas in my /6 Belvedere with a straight pipe and used to start it up in the shop and then hit the button to open the door until I noticed it was splattering the door. I always parked it inside and very close to the door so it didn't take up anymore room than it needed....made nice looking splatter art on it lol

 

[green1]

Keep lowering the octane til it pings, then go back up. Higher octane burns slower, and will even slow you down.

 

[67 B-body]

I'm with Cranky. However, if you take all the bits and pieces that comprise Gasoline, look at the periodic table removing the components that burn,,, your left with H2O..... A good complete combustion always results in this. I'm probably telling you everything you already know, but maybe others reading do not.
BTW, I dont think you will slow down with higher octane levels! At least nothing available for purchase.... The burn of fuel and expansion of gases wont take any longer than the time of stroke unless your ign timing is way late! I would bet that the engine wouldnt even run at the needed retarded timing to accomplish this.
Anyhow,,, good luck tracking things down!

 

[70rr-brian]

Well I am performing an experiment at the moment. I ran the last of the 4th tank out, wiped down the bumper and put Shell gas back in it. The short drive home I didn't notice any speckling. I will take the car out tomorrow and terrorize the streets to see if any speckling is there.

I am just wondering if it is the result of some kind of detergent/additive or higher ethanol content in that gas that is causing this. But I will know tomorrow for sure if this is related to that particular fuel or not.