Low boost & black smoke with ATT

[Slim Shady]

I think Buddy has a valid point also, residual pressure in the exhaust affects volume in a manner of speaking. The volume affected is the amount of residual exhaust left in the cylinder which displaces the potential for the new air charge. If Buddy's math is correct then we have added 5 percent more fresh air that was previously exhaust gas which was not expelled. Add 5 percent more fresh air and at a higher density because of lower temperature (air molecules are packed closer together when cold) then we are seeing some efficiency gains. Most people see a fuel mileage increase of between 1 to 3 MPG, this fact has been established by most of the ATT owners. My fuel mileage also has increased ( at a smaller rate ) when towing.

Most people don't and wont care about the reason why the A-Team Turbo works: just that it works, and that is no BS.

 

[buddy]

Thanks, yeah I was taking into account the 0.037 litres of volume left in the 22:1 compression ratio cylinder when the piston is at TDC. The less we compress that to push it out the port the less dense it is when it expands back into the cylinder during intake stroke.

The aftermarket claims of twice the flow at the same boost I have seen on lots of turbos and its always bothered me, since it is not really true, unless you also swap your engine for one that is twice as big or runs twice as many RPMs.

Imagine if you put the ATT on a 6.5L Gas engine that ran twice as many RPM, it is the same volume, but exchanges air twice as much. That is what the turbos flow rating is meant for, what its capacity is.

 

[SmithvilleD]

Definitely right to also consider the amount of residual exhaust left in the cylinder at exhaust stroke TDC (clearance volume). The mass/weight/lbs of that residual exhaust, not volume. Volume defines the space that mass is contained in.

The reason I started with air-charge density, is to describe what's going on, without the term "airflow" confusing the issue. People seem to have different interpretations of what "airflow" means.

A career turbo engineer guy explained it to me this way:

Don't confuse air-charge density with airflow. Forced induction increases air-charge density, not airflow. The airflow through an engine remains the same whether or not it is turbocharged. The power increase comes from the increase in air-charge density.

 

[Slim Shady]

Definitely right to also consider the amount of residual exhaust left in the cylinder at exhaust stroke TDC (clearance volume). The mass/weight/lbs of that residual exhaust, not volume. Volume defines the space that mass is contained in.

The reason I started with air-charge density, is to describe what's going on, without the term "airflow" confusing the issue. People seem to have different interpretations of what "airflow" means.

A career turbo engineer guy explained it to me this way:

Don't confuse air-charge density with airflow. Forced induction increases air-charge density, not airflow. The airflow through an engine remains the same whether or not it is turbocharged. The power increase comes from the increase in air-charge density.

Understood, I was not trying to make my explanation to technical.

 

[buddy]

The air filter/ram air/turbos/exhaust/mufflers etc for the longest time have been sorely misrepresented in advertisement from aftermarkets across all segments.

In the case of flow (CFM), volume is key. Although when you argue mass air flow then density important. But yes to determine the amount of available volume for air to flow to the density of the remaining exhaust and how it expands and compresses in the dynamic cylinder environment was taken into account.

I have always made the point that the flow claims are inaccurate. Which is relevant to the earlier discussion that because someone added an ATT they may need to upgrade their air induction. At only about 5% more flow I do not think there should be an issue unless there was an existent restriction when the GMx turbo was on. And thus the ATT doesnt have that hidden cost. 94-95 year intakes should be upgraded for any turbo.

Now for anyone looking, if you dont have a 4" exhaust already, I woud make that investment before an ATT and see if the GMx would then meet your needs, because youll need it to get the most benefit from the ATT anyway.

 

[Matt Bachand]

As always, turbo chargers are exponential upon themselves, so the 5% gain on one stroke, combined with the again reduction in backpressure, and the new 5% gain based on the old 5% gain I think the gain ends up beuing alot more than 5% overall.

 

[buddy]

The 5% gain takes into account all those factors. And it is only a 5% CFM gain, cant get any more than that.

because the turbo will transfer less heat and you may have lower IATs then your Mass Air Flow will also go up. So in that way you will see compounded gains.