Late model engines overfueling at WOT

[4vpc]

I see a lot of folks around here on the more major roads pulling away from the lights at WOT or near, and rarely is there smoke.

That's a strange place you live if people drive like that all the time, do you live on a race circuit or drag strip maybe?
As alluded to above the ECU will overfuel the engine as intake temps rise above the norm to protect the engine, if they don't then it won't.

[Morgo]

Ha,my -93 Camry V6 will go to AFR 9,5 at WOT and at least no one has commented about black smoke.Diluting the Russian 95 octane with E85 leans the mixture for noticeably more power (but Russian cost 0,60€ compared to domestic E85 about 1 €..)

[cv67]

02 truck gets a lot on WOT but its due to massive carbon buildip from miles and babying it. Over time noticed its lost power backsides of the valves must be caked up bad.

[n2xlr8n]

The factory programmed USDM Subaru turbo engines are typically found to be in the 10.2-10.5:1 AFR range...pig rich, but no black smoke.

Look at any late model Hyundai Veloster tailpipe- one can clearly see they are pig rich.

It's the new Black

I'm not convinced that just looking into the pipe and seeing it look black means that its rich at all when running on unleaded. A properly jetted engine will make surfaces exposed to the exhaust either white or black, no in between. Where the surfaces are cooler, black, hotter white. Look into the exhaust port, I bet it has walls that are black yet the valve itself will be white or maybe have a very slight tan tint. The header pipe will be black up by the head where its cooled but then turn white as it gets farther away from the cooling system. Tail pipes and end of the collectors, black.

Sorry, Dave- I mis-spoke. I agree; seeing is not the same as WBO2.

Look at any Hyundai Veloster rear valance and one can clearly see they are pig rich

On a serious note, I've datalogged thousands of miles on the stock EJ ecus in Subarus- my statement stands.

[user-23911]

Ha,my -93 Camry V6 will go to AFR 9,5 at WOT and at least no one has commented about black smoke.Diluting the Russian 95 octane with E85 leans the mixture for noticeably more power (but Russian cost 0,60€ compared to domestic E85 about 1 €..)

Your WB will be reading wrong as they all do.

You don't get 9.5 AFR without smoke.

[DaveMcLain]

The factory programmed USDM Subaru turbo engines are typically found to be in the 10.2-10.5:1 AFR range...pig rich, but no black smoke.

Look at any late model Hyundai Veloster tailpipe- one can clearly see they are pig rich.

It's the new Black

I'm not convinced that just looking into the pipe and seeing it look black means that its rich at all when running on unleaded. A properly jetted engine will make surfaces exposed to the exhaust either white or black, no in between. Where the surfaces are cooler, black, hotter white. Look into the exhaust port, I bet it has walls that are black yet the valve itself will be white or maybe have a very slight tan tint. The header pipe will be black up by the head where its cooled but then turn white as it gets farther away from the cooling system. Tail pipes and end of the collectors, black.

Sorry, Dave- I mis-spoke. I agree; seeing is not the same as WBO2.

Look at any Hyundai Veloster rear valance and one can clearly see they are pig rich

On a serious note, I've datalogged thousands of miles on the stock EJ ecus in Subarus- my statement stands.

So from what you're saying if you pulled the pipe off of the engine after some hard running the exhaust valve would also look mostly black? That's certainly possible.

[modok]

I see a lot of folks around here on the more major roads pulling away from the lights at WOT or near, and rarely is there smoke.

That's a strange place you live if people drive like that all the time, do you live on a race circuit or drag strip maybe?
As alluded to above the ECU will overfuel the engine as intake temps rise above the norm to protect the engine, if they don't then it won't.

I live in colorado springs.
Sorry i did not remember,location is unlisted on this forum.

[MadBill]

More altitude equals more throttle... (and for carburetted cars, more chance of black smoke.)

[MadBill]

Back in the day, GM vehicles destined for certain high altitude locations were equipped with specific p.n. leaner carbs.

[modok]

It could go either way with altitude depending on how they structured the fuel equations and so forth.
The question really made me wonder, but then I realized...it would be no secret.
Besides legal pot and altitude, we also have steep hills and virtually no law enforcement, no emissions tests.

Perhaps the very HIGH performance vehicles would be more prone to this?

[Belgian1979]

There is no use at overfueling at WOT. At WOT, unless too high static CR or incorrect ignition timing to begin with, you have less chance of knock. In fact too much fuel creates less power.
In a turbo engine you would regularly see 11/1 AFR due to the fuel being used as a means to cool the combustion chamber and prevent the onset of knock.

[Truckedup]

The vintage air cooled 4 stroke motorcycles I race are over routinely over fueled as insurance against detonation and seizure....I got daring and leaned out the WOT mixture looking for more power and found it. For the 1-1/2 mile land speed racing, nothing melted......The competition thinks I have special speed secrets...

[peejay]

There is no use at overfueling at WOT. At WOT, unless too high static CR or incorrect ignition timing to begin with, you have less chance of knock. In fact too much fuel creates less power.
In a turbo engine you would regularly see 11/1 AFR due to the fuel being used as a means to cool the combustion chamber and prevent the onset of knock.

Production engines typically do have compression ratios higher than what would be best for WOT, in order to gain more efficiency at idle and part throttle. Engines spend 99-100% of their lives at idle ad part throttle.

They aren't terribly concerned about losing a few percent power at WOT as much as they are concerned about keeping the catalysts from melting down (100,000-150,000 mile warranty, required). There are some new engines that don't go into PE *at all* because they are able to keep the engine and catalysts sufficiently cool via other means. This is quite a trick because modern practice is to attach the catalysts directly to the head, or turbocharger outlet, in order to maximize the heat they get to minimize the time required for them to light off. Once the cat is lit off, exhaust is typically cleaner than the air going IN to the engine, so the only way to make cars "cleaner" is to light the cat off more quickly.

I see modern gasoline engined cars blowing soot most mornings. My morning commute has me take a curving uphill on-ramp to our friendly local Interstate, and the merge is uphill, and the road after the merge is uphill. You go balls-out, or you block traffic. Most people choose to block traffic, some bolt the throttle to the floor and race to get out of everyones' way. That's when you see a little soot blown out the pipes, if you're paying attention.

My new car has only 8.5:1 compression because Volvo designed it to operate at WOT and 15 pounds of boost basically forever. To this end, it does NOT have a close coupled cat, and cold economy is horrifically bad in their attempts to get it to light off quickly. On the other hand, I can accelerate up that onramp, through the curve, and be traveling at over 80mph by the time I can start to see the traffic I will have to merge into My previous record is 70mph in a car with much better power/weight, but no all wheel drive or active handling...

[Keith Morganstein]

My ford mod v8 with OBD1 would push a bit of black smoke when first going to WOT, then clear up. Engine/car was abnormally fast for what it was.

[chimpvalet]

If it's a matter of a brief puff of soot upon going WOT isn't that just blowing residuals out of the muffler and tailpipe, rather than mapped enrichment?