The Carb Cheater

[63 Sprint]

Yesterday, before filling up with fuel the A/F ratio was pretty much dead on after going one jet size smaller. An issue came up right after filling up with fuel. The A/F ratio leaned out too 15.2 to 15.7. Typically, this is considered too lean for these engines to operate safely.

Later yesterday evening, a member here pointed out that the ethanol content
at the pump is not controlled well and can vary a great amount.

My fix was, I reverted back to one jet size larger to get the A/F ratio in check.

About a year and a half ago. I worked on a friend’s car. The car felt slightly sluggish and check engine light was on. Hooked up the scanner and did a diagnostic check. It turned out that the ethanol content was very high. I believe it was almost 30%. The cars fuel tank was near 1/4 full. So we filled the car with ethanol free fuel. And in a few minutes the problem was corrected. The code was cleared and check engine light went off.

The gas station my friend fills up at doesn’t sell E-85 so, mistakenly filling with E-85 is ruled out. It looks like the problem emanates from the fuel depots. I guess mistakes can be made. Unfortunately, we are the ones that suffer if engine or fuel system damage is done and it can’t be proven that it was a result of bad fuel during a fillup.

This morning I was thinking back and there was talk on this forum about a device called The Carb Cheater. I’m wondering if anyone has tried one. The person that makes these, mentioned that it is not a fix for a poor running engine. It’s designed for getting the most out a carb’d engine that is already tuned pretty well.

The Carb Cheater

Helping people tune their carburetors

thecarbcheater.com

https://thecarbcheater.com/Install.php

 

[Kritas]

I think it's a very interesting idea. I've considered an AFR but am holding off buying one for now while I focus on other aspects of my restoration. I could use something to take some of the guesswork out of tuning my carb. The Carb Cheater is on my radar, but I need some more data from owners before jumping in.

 

[rocklord]

The Carb Cheater works by adding air to the intake. It cannot decrease the amount of air going through the carb.

 

[comet6]

.

 

[rocklord]

A feedback carb, pwm solenoid, and o2 sensor.. seems like someone could make an affordable module to drive it. Quadrajet had tps and solenoid built in.

The creator of the Carb Cheater did make an ECU/module. By adjusting the vacuum leak, the Carb Cheater can adjust the AFR from rich to 14.7.

 

[Frank]

The idea is valid, and would help in 63Sprint's situation of a lean-jetted carb vs changes in fuel or atmospheric conditions. All carbs need leaning when altitude increases also.

When I visualize a controlled raw-air bleed into the intake on an engine under load, my immediate consideration is where is this air being added? Unless it's dispensed centrally with some engineering behind it, the overall AFR may read ok, but a few cylinders may be fuel starved to the point of damage.

Need to muse on this some more, but the first distribution design that comes to mind looks something like a NOS spray bar designed for air. Just dumping raw air into, say, an unused intake port is risky at best, for safe even fuel distribution IMO.

 

[comet6]

.

 

[PSIG]

The A/F ratio leaned out too 15.2 to 15.7. Typically, this is considered too lean for these engines to operate safely.

Actually, max economy and coolest burn is in the low to mid-16:1 range for this engine design and typical pump gas fuel blends. Lean is fine, but does not get the economy without complimentary ignition timing, which also reduces heat. I custom-tune for efficiency (power, economy, emissions, etc), with special emphasis on economy, and find this value repeatedly.

The carb Cheater has been discussed extensively on other forums, and it actually does what it claims, but is very limited in doing that job. It can help a power tune to squeak more economy (with vacuum timing adjustments) by leaning (only), towards a programmed AFR, under certain conditions. That's fine.

As a comparison, you can use a DIY-style aftermarket EFI controller under $100 and a WBO2 to do not only that, but also adjust the ignition timing to match, and even add fuel - all in one little box, through one program in a laptop or your phone for easy adjustment. And, they can sense the actual ethanol % and adjust fuel and timing for it automatically. But, it means getting deeper into it for greater gains. Pros and cons to everything. What do you want or need?

 

[Frank]

a DIY-style aftermarket EFI controller under $100

Where do I procure this?

 

[PSIG]

I disagree with 16:1 range.

Happy to discuss it. I just follow the tuning data. If you disagree (and I see you do), start the thread if you like.
[EDIT] I see you edited your post. The peak economy gasoline AFRs for our engine designs is not a part of the controller or $100 comments. They are separate discussions, and only examples of other options with other abilities.

Where do I procure this?

Many competitive and open sources. A couple examples of firmwares that many types and styles of controllers are using for inexpensive hardware ECMs are Speeduino, and at the other extreme RusEFI, and others. Here is one example of a minimal unit capable of doing everything I mentioned: NO2C. If that doesn't quite fit your vision or needs, there are only a few dozen other variations from others to choose from.

 

[Frank]

Many competitive and open sources. A couple examples of firmwares that many types and styles of controllers are using for inexpensive hardware ECMs are Speeduino, and at the other extreme RusEFI, and others. Here is one example of a minimal unit capable of doing everything I mentioned: NO2C. If that doesn't quite fit your vision or needs, there are only a few dozen other variations from others to choose from.

Thanks!

 

[wsa111]

Actually, max economy and coolest burn is in the low to mid-16:1 range for this engine design and typical pump gas fuel blends. Lean is fine, but does not get the economy without complimentary ignition timing, which also reduces heat. I custom-tune for efficiency (power, economy, emissions, etc), with special emphasis on economy, and find this value repeatedly.

The carb Cheater has been discussed extensively on other forums, and it actually does what it claims, but is very limited in doing that job. It can help a power tune to squeak more economy (with vacuum timing adjustments) by leaning (only), towards a programmed AFR, under certain conditions. That's fine.

As a comparison, you can use a DIY-style aftermarket EFI controller under $100 and a WBO2 to do not only that, but also adjust the ignition timing to match, and even add fuel - all in one little box, through one program in a laptop or your phone for easy adjustment. And, they can sense the actual ethanol % and adjust fuel and timing for it automatically. But, it means getting deeper into it for greater gains. Pros and cons to everything. What do you want or need?

What vehicle & engine combination are you refering to?

 

[InlineDave87]

So since thunderhead 289 came up with this product i have been following it to see its practical applications. Other guys with thier own youtube channels have purchased it and reported back that the engine runs better. One has even tested it going up mountains and changing elevations, something carbs were known to be weak at, and said they noticed that their car or truck handled the elevation change without a hiccup.
Others i have seen have reported that it has help improve their economy some. Maybe a couple of mpg. I believe this controlled vacuum leak that goes right under the carb corrects the vacuum signal to the cab and there for draws less fuel to your desired afr when it is slightly rich. I also like the feature that you can kill the ignition to your distributor as a form of antitheft device.
Im hoping to buy a couple of them and test out a few other possible applications, but its going to take me some time to do so.

 

[Kritas]

PSIG, it's a very interesting topic and I encourage you to start a thread on it. I'm learning from the discussion.

 

[Frank]

Ok, let’s stay on the topic, “The Carb Cheater”

Thanks

I looked at Luke's site for the carb cheater. + a couple of videos. The kit does supply a carb to intake spacer with the ported air supply to operate the device. Nice.

 

[sixtseventwo4d]

Removed per request of senior advisors

 

[comet6]

removed

 

[MechRick]

Some older Hondas used the air bleed method for closed loop fuel control. The mentioned Q-Jet (and most others) use solenoids that vary the fuel level around the jets to change the fuel mixture. I doubt a performance difference would be noticeable if the carb is close to start with. Where I see a possible benefit is eeking some problematic vehicles through emissions testing.

The problem with running a carb (and more important, a carb intake) at stoiciometric air/fuel ratios is fuel distribution (or in this case, the lack of it). Factory carbs typically run a bit fat (13.7:1-ish) to insure the leanest cylinder stays safely rich at moderate throttles to keep from burning pistons and exhaust valves. Run that setup at stoich and there's that possibility. Inline engines are more prone to this.

For instance, if your wideband O2 sensor is showing 14.7:1 while you are cruising down the street, it's very likely you have a few cylinders at, say, 13.9:1 and a few at 15.5:1. The O2 reads the average.

That's why I've taken the position that when you are tired of that carb, go straight to port injection. You will thank me.

I don't agree that AFR's of 16:1 are cooler. Every engine I've ever played with will ping when lean, and that's caused by heat.

 

[PSIG]

The Carb Cheater's claim-to-fame is the ability to hold closer to target fueling, with controlled incremental bypassing of air into the manifold to lean the current mixture, per your programmed target values, referencing a wide-band O2 sensor. This should allow maintenance of a target AFR much closer under varying but fairly stable conditions than a traditional carburetor tune to the same values. It is active Lambda control, reactive to current conditions. Very simple but cool concept, and possibly quite useful to certain users in certain conditions.

While the common rebuttal is that we should just tune our carbs leaner or properly to best power and best economy in the first place, thereby covering all the needs; the CC has the capability (I have not tested CC, but am very familiar with the process) to maintain that tune closer with that responsive adjustment of air. This would indicate the most to gain is by users with large changes in conditions, from fuel grade, blend, altitude, temperatures, etc under fairly stable conditions (typically cruise). Stable, as the response is delayed after combustion (so it is limited in quickly-changing conditions), and the stepper motor idle air valve from '70s-'80s GM EFI is relatively slow to adjust airflow.

All good. It is important to recognize the function is only from a presumably richer tune, and leaning to a target value. This means tuning to achieve a tune incrementally rich for any conditions, so the CC can add air to lean to the target. It also means tuning to find what that target should be for your car, engine, fuel, etc, and the ignition timing to support that AFR safely. It could be helpful to many, to learn some principles, concepts and examples of methods to safely and accurately find what those values could be, and why.

I thought this thread was a very appropriate place to discuss tuning of exactly that nature, as required for safe and effective use of various devices such as the Carb Cheater, EFI, or carburetors, and the advantages to each for users to choose. Some think not. That's fine, but I did not come here to wade-in and preach to those that don't want to hear it. I've done this type of work for decades, so that's not me, although I do try to 'pay it forward'. If someone wants to discuss tuning topics, then show the interest by starting the thread. Thanks!
Sorry deleted by accident.

 

[Frank]

The Carb Cheater's claim-to-fame is the ability to hold closer to target fueling, with controlled incremental bypassing of air into the manifold to lean the current mixture, per your programmed target values, referencing a wide-band O2 sensor. This should allow maintenance of a target AFR much closer under varying but fairly stable conditions than a traditional carburetor tune to the same values. It is active Lambda control, reactive to current conditions. Very simple but cool concept, and possibly quite useful to certain users in certain conditions.

While the common rebuttal is that we should just tune our carbs leaner or properly to best power and best economy in the first place, thereby covering all the needs; the CC has the capability (I have not tested CC, but am very familiar with the process) to maintain that tune closer with that responsive adjustment of air. This would indicate the most to gain is by users with large changes in conditions, from fuel grade, blend, altitude, temperatures, etc under fairly stable conditions (typically cruise). Stable, as the response is delayed after combustion (so it is limited in quickly-changing conditions), and the stepper motor idle air valve from '70s-'80s GM EFI is relatively slow to adjust airflow.

All good. It is important to recognize the function is only from a presumably richer tune, and leaning to a target value. This means tuning to achieve a tune incrementally rich for any conditions, so the CC can add air to lean to the target. It also means tuning to find what that target should be for your car, engine, fuel, etc, and the ignition timing to support that AFR safely. It could be helpful to many, to learn some principles, concepts and examples of methods to safely and accurately find what those values could be, and why.

I thought this thread was a very appropriate place to discuss tuning of exactly that nature, as required for safe and effective use of various devices such as the Carb Cheater, EFI, or carburetors, and the advantages to each for users to choose. Some think not. That's fine, but I did not come here to wade-in and preach to those that don't want to hear it. I've done this type of work for decades, so that's not me, although I do try to 'pay it forward'. If someone wants to discuss tuning topics, then show the interest by starting the thread. Thanks!

Carbs are always rich on decel. If this device adds air then, it's helpful. As you know, small changes in air density from temperature and atmospheric pressure have an effect of several % on metering. Today here, for example, the air is almost 10% denser than it has been for the last 7 months. My carb vehicle has 2" more vacuum at light cruise than in July. Summer lean-limit jetting must be enriched now for winter. This device would help fill the gaps, or "soften the edges" when richer jetting is left in service, assuming it does what it says. This device is not a solution for one who is not carb- wise, it's a fine-tune tweak to "soften" some of a carbs inherent rich-spikes, as you have pointed out. Not planning to buy one, but the principle is solid.