R-Spec Very Rich @ WOT

[JeffGST]

I understand Hyundai engineers program these motors to run rich, in order to provide a safety cushion for full throttle driving. But to run the motor as rich as they programmed the 5.0L is absolutely ridiculous.

Driving on the highway last night, a car was in my lane going 25 MPH slower than the pace. After passing the car with around 75% throttle, I noticed the black smoke screen that I was creating. The cars behind me basically disappeared behind exhaust fumes. I'm estimating the AFR's must have been in the 9 to 1 ratio for there to be that much unburnt fuel coming out the rear. Now I'm leaning toward adding a few gallons of E85 to the tank, just to get WOT mixture to lean out a bit.

Is this a common complaint from most of you guys. Now I completely understand why I have to polish out exhaust stains from my rear bumper every month.

 

[Ernie3647]

To get better results from responses include year of vehicle.

 

[Mark_888]

I understand Hyundai engineers program these motors to run rich, in order to provide a safety cushion for full throttle driving. But to run the motor as rich as they programmed the 5.0L is absolutely ridiculous.

Driving on the highway last night, a car was in my lane going 25 MPH slower than the pace. After passing the car with around 75% throttle, I noticed the black smoke screen that I was creating. The cars behind me basically disappeared behind exhaust fumes. I'm estimating the AFR's must have been in the 9 to 1 ratio for there to be that much unburnt fuel coming out the rear. Now I'm leaning toward adding a few gallons of E85 to the tank, just to get WOT mixture to lean out a bit.

Is this a common complaint from most of you guys. Now I completely understand why I have to polish out exhaust stains from my rear bumper every month.

I suspect that the smoke is more a result of the GDI system than anything else. Lots of complaints about GDI soot.

Does the owner's manual say you can use E85? If not, I would not second guess them.

What grade of fuel do you use? V8 takes regular or premium (or mid grade obviously). You could experiment with different octane levels to see if that helps.

 

[geops]

I have no black smoke at full-open throttle. Check with a dealer.

 

[amartz]

If it was the first time in a while that you've nailed it, you can expect some soot until you've done a proper Italian tuneup. After that, it should be a lot less.

 

[427435]

Now I'm leaning toward adding a few gallons of E85 to the tank, just to get WOT mixture to lean out a bit.

If E85 is an allowed fuel, using some shouldn't lean things out. The O2 sensor and computer should still give a proper fuel/air ratio.

 

[Mark_888]

E85 is not allowed for the 5.0 V8:

"E85" fuel is an alternative fuel comprised of 85 percent ethanol and 15 percent gasoline, and is manufactured exclusively for use in Flexible Fuel Vehicles. “E85” is not compatible with your vehicle. Use of “E85” will result in poor engine performance and damage to your vehicle's engine and fuel system. HYUNDAI recommends that customers do not use fuel with an ethanol content exceeding 10 percent."​

 

[JeffGST]

To get better results from responses include year of vehicle.

2014 R-Spec with October 2013 build date
91 Octane

Now I understand that Hyundai will obviously not recommend the average uninformed consumer to use Ethanol. But if you have someone with extensive tuning knowledge base that understands the Stoichiometric ratios of gasoline and E85, then mixing a few gallons of ethanol will not harm any gasoline motor. The ECU is more than capable of compensating for 4 gallons of E85 to the 16 gallons of 91 octane.

I already added 4 gallon of E85 and topped the rest off with 91 Octane. The motor ran great considering that it was 106F today. I didn't have a chance to open up the throttle today with all the traffic.

Current Stoich:
4 Gallons of E85 = 9.7 to 1 (20%)
16 Gallons of 91 Octane = 14.7 to 1 (80%)

That averages out to a Stoich of 14.1 to 1. It's only a 4% change in overall stoich, but the motor seems to like it a lot. It will run 4% leaner at full throttle, but since E85 is 105 octane there is a larger safety margain also. There is no change in performance at idle or light throttle since the O2 sensor takes care of that.

I'll update with more full throttle info later.

 

[JeffGST]

If E85 is an allowed fuel, using some shouldn't lean things out. The O2 sensor and computer should still give a proper fuel/air ratio.

O2 sensor is only in control of AFRs during Closed Loop operation, such as idle and part throttle. Any time the driver applies more than half throttle, the ECU goes into Open Loop operation and it ignores the O2 Sensor. The ECU instead uses the programed fuel map to properly flow the correct fuel based off of the airflow sensor readings.

So E85 (20%)/91 (80%) at idle and part throttle will still have normal AFRs since the O2 sensor will compensate. The Open loop map will be leaner since it uses only the fuel map and the airflow sensor to calculate injector duty cycle.

Open Loop is where I see all the black smoke. That is why I am experimenting right now with the E85.

 

[Mark_888]

Now I understand that Hyundai will obviously not recommend the average uninformed consumer to use Ethanol.

Recommend? Let's be more specific. If you damage your engine and Hyundai finds out that you used E85, your engine warranty is null and void.

Although you may have a lot of knowledge of engines in general, you knowledge of this specific GDI engine is not anywhere at the level of Hyundai engineers who advised that:

"“E85” is not compatible with your vehicle. Use of “E85” will result in poor engine performance and damage to your vehicle's engine and fuel system."​

______________________________

Help support this site so it can continue supporting you!

 

[JeffGST]

Although you may have a lot of knowledge of engines in general, you knowledge of this specific GDI engine is not anywhere at the level of Hyundai engineers who advised that:

"“E85” is not compatible with your vehicle. Use of “E85” will result in poor engine performance and damage to your vehicle's engine and fuel system."​

The engineers who wrote that, are advising the public not to run a full tank of E85. This is the only way you could "damage" the GDI motor by causing very lean mixtures throughout the powerband. The ECU will not be able to compensate enough for the additional 35% more fuel flow needed to properly run E85. But adding 4 gallons of E85, to 16 gallons of 91 octane just requires a 4% increase in injector duty cycle. The ECU is more than capable of that.

As for the update on the black smoke issue... it is pretty much gone. The addition Ethanol has leaned out the top end enough to where it is barely noticeable. The top end is clean and just powers through to redline now. I might have to do this all summer. I will need to keep a log in order to keep the E85/91 ratio in order.

 

[qstarweb]

I don't get this at all. The best gasoline to burn is 93 octane (94 if you can get it) with NO ETHANOL, just pure gasoline. You should see the highest "miles to go until empty" with that over any gasoline with ethanol in it.

Dean

 

[PMCErnie]

Wow, the Genesis has been around since late '08 and finally JeffGST has solved Hyundai's problem.

 

[JeffGST]

Wow, the Genesis has been around since late '08 and finally JeffGST has solved Hyundai's problem.

What I have to do next is install a wideband O2 sensor in the exhaust to measure actual AFRs. Find out what AFR Hyundai targets at WOT and then another pass with 20% E85 in the tank. I want to get rid of this black soot permanently.

 

[geops]

Go to your dealer because cloud of black smoke under acceleration is not normal!

 

[bigpapainscotia]

I have black soot ever time a nail the throttle. Plus i have a white 2012 genesis. So i'm always cleaning the back bumber and the trunk area. I guess this is a common problem with the gdi engines.

 

[kg4pto]

From what I understand it is basically par for the course with the GDI system. If you don't give it the old "Italian Tune-Up" every once in a while, it will give you soot.

 

[Turboba6]

Subcribed for the Full Throttle info...This makes Sense, since the Factory has Very Rich Programing to make up for Low octance, etc., In the Mustang world there have been folks that used a few gallons of E85 with the Stock factory tune, and picked up a few MPH in the 1/4....!!

 

[Rey]

All OBD monitored autos, every brand, operate fuel systems in two modes. "Closed Loop" mode is used after initial warmup, cruise and light to moderate acceleration. Closed loop maintains a constant air/fuel ration of 14.5:1 - it may richen slightly on acceleration, but generally maintains 14:5.
On cold start up the car needs a "choke" and reverts to "open loop", which is basically a "fuel dump" of maximum fuel volume. Open loop is a parallel fuel circuit to closed loop. On heavy acceleration the system reverts to open loop and fuel ratio lowers to as low as 9:1, though 10-11:1 is more common. Optimum fuel ratio for max power is roughly 12.8-13:1. Manufacturers do this in part to preserve the motor thinking that an overly rich mixture is safer than a leaner mixture on WOT.
Most, if not all, aftermarket tuners work to modify the open loop system. The closed loop is emission friendly/legal, hard to "crack" and is left alone. If the tuner can modify open loop to lean mixture there is usually a nice hp gain at WOT.
I think JeffGST's mixture of E85 and 91 octane is a clever way to lean fuel ratios at open loop. It would be very interesting to see actual fuel ratios and dyno before and after.

 

[PMCErnie]

Go to your dealer because cloud of black smoke under acceleration is not normal!

Exactly. It does occur, but not routinely. Anybody else, but a "garage expert" would get it checked out.