Replacement turbo

[buddy]

The tune is the major cause of more air pull, this advice is good for anyone that gets a performance PCM. The stock 94-96 air boxes are crap for air flow and not all aftermarket filters are created equal. You do get a little more air flow from ATT, but when you ditch stock PCM constraints can run so much more boost reliably.

 

[Turbine Doc]

Been running Amsoil nano airfilter in mine for almost 2 years now, works well, check with Wrecker aka Oil Geek to see specs on the filter

 

[Matt Bachand]

Been running Amsoil nano airfilter in mine for almost 2 years now, works well, check with Wrecker aka Oil Geek to see specs on the filter

I think I'm gonna ditch the K&N and order up one of these bad boys myself. Wrecker if your reading this PM me with the proper filter n cost. I have the 97+ Large airbox, but dont' want the filter thats too big.

 

[guybb3]

I think I'm gonna ditch the K&N and order up one of these bad boys myself. Wrecker if your reading this PM me with the proper filter n cost. I have the 97+ Large airbox, but dont' want the filter thats too big.

I bought a few things from him, including the air filter you're looking to get, Matt. I talked to him on the phone and what a great guy to deal with.

 

[DieselCash]

I bought a few things from him, including the air filter you're looking to get, Matt. I talked to him on the phone and what a great guy to deal with.

:iagree:

 

[NoDak]

I haven't tried either of these, but I am very curious...

http://www.r2cperformance.com/index.html

http://www.amsoil.com/products/ea_filters/EaA.aspx

 

[Detroit Dan]

I went back to a stock paper filter after running K&N for years. I just read so much negative stuff about them, apparently their flow gains are at the expense of filtration. Just looked at the Amsoil air filter, and while the technology looks impressive, and I can believe it filters better, all they talk about is efficiency, rather than flow. Maybe it does flow better, but I'd need to see it. If I'm going to drop that kind of money on a filter, I want to see it not only filter better but put more air in the engine. And I would like to be sure my turbo isn't going to suck it down it's throat.

 

[Detroit Dan]

The tune is the major cause of more air pull, this advice is good for anyone that gets a performance PCM. You do get a little more air flow from ATT, but when you ditch stock PCM constraints can run so much more boost reliably.

The ATT is only a little more air flow? The thing is at least 50% bigger than my old turbo, I would have thought it was more than a little. It was more than a little improvement towing, with same programming.

 

[Matt Bachand]

The ATT is only a little more air flow? The thing is at least 50% bigger than my old turbo, I would have thought it was more than a little. It was more than a little improvement towing, with same programming.

DD, I believe he meant with a stock tune.

Once you have a new reflash in there, the increased fuel table allows the ATT to really spool up...

Now, my friend, you have a LOT more air flow required.

 

[NVW]

Matt, I think Dan was referring to stock tune, he had the turbo before and just got the tune.

 

[Matt Bachand]

Matt, I think Dan was referring to stock tune, he had the turbo before and just got the tune.

Then he's probably feeling the effects of less backpressure too.

Gotcha, just re-read it. Its gotta use quite a bit of air more than GM-X, however, its probably 'little' in comparison to a Chipped out ATT's Air Demands??:sheephump:

 

[buddy]

The ATT is only a little more air flow? The thing is at least 50% bigger than my old turbo, I would have thought it was more than a little. It was more than a little improvement towing, with same programming.

I tried to bust this myth of twice the flow at half the pressure before, but it was another thread.

In general it is impossible to flow more air at an equivalent or lower pressure, unless you increase the volume of the system, like by increasing RPM, or larger engine, etc....

The cam closes both valves during compression so its a closed system. The only way the larger turbo flows more air is by reducing backpressure which reduces the volume of the residual exhaust gases left after the exhaust stroke. Thats because it closes the valve before TDC and so there is exhaust compressed to the amount of backpressure still in the cylinder that will expand within the cylinder during intake stroke. So with ATT then there is a little, ~5% max at high boost, more volume in the cylinder for air to occupy during intake stroke. Thats because ATT has low backpressure requirement between engine and turbo to create 15psi, but GMX starts requiring more and more backpressure when it goes beyond 10psi, and at 15psi it needs like 28psi backpressure, versus the 19psi backpressure the ATT would need to make 15psi boost.

This is another way the larger turbo helps, the turbo is less parasitic to power. The more backpressure it has to create, the more work the cylinder has to do the push it out. So you lose less power with larger turbo.

You must also first realize there is a difference between flow and mass. Flow is a value based on volume, and a given volume can have less or more mass. So a larger turbo also helps by increasing air mass in the amounts of volume it does provide. This is because the turbo transfers less heat to the intake air, so it is cooler, and more dense (more mass for a given volume). So without increasing flow at all, you can double air mass by cutting temperature in half. This is also what intercoolers do for you.

And finally, just because a turbo might say its rated to put out 7000 CFM at 10psi or something like that does not mean at 10psi it is flowing 7000 CFM. It just means its capable of it, if your volume demand is that high. you could have it set up to pressurize to 10psi while cruising at 55mph empty at 1500rpms. And its not hard to see you could also have it set up to pressurize to 10psi under load at 3000rpm, but obviously you are using twice as much air flow when you fill the cylinders twice as many times in the same period of time, under the same amount of boost. Our engine can only accept so much air, 6.5 litres (in ideal world) per crank, so at 4000rpm thats about 1000 CFM it can accept, but youre still using a turbo capable of outputting 7000 CFM at the same pressure. So if our engine was 7 times larger, or was a gasser race engine that went to 15000 rpm, then it could still supply it 10psi without much trouble and sustain it without exponentially raising the required backpressure.

 

[GJF]

Our engine can only accept so much air, 6.5 litres (in ideal world) per crank, so at 4000rpm thats about 1000 CFM it can accept, but youre still using a turbo capable of outputting 7000 CFM at the same pressure.

This is true in a N/A engine. AIR COMPRESSES which in turn is the whole concept of forced induction...... Under N/A condition the volume of air able to be filed into a given cylinder is dependant on the efficiency of the intake, ports of the cylinder including the valves being regulated by the given camshaft profile. If the above components average out to be 60% efficient then the cylinder can only be filed 60% of it's capacity. The addition of higher flowing intakes, ported and flowed cylinder heads and more aggressive camshafts will allow a higher percentage of efficiency to the cylinders.

Now add a turbo or a supercharger, and the cylinder will meet or exceed the volume capacity of the cylinder by forcefully pumping air into the cylinder. Adding Higher flowing intakes ported and flowed cylinder heads and even a more aggressive cam profile will improve the cylinders fill rate, by trying to improve the intake efficiency for a given compressor (turbo or supercharger). Will allow even further power output as long as the compressor is able to provide more volume without excessive heat buildup allowing the volume of air to exceed the "area volume" of a given cylinder.

So bottom line is displacement is not the deciding factor when forced induction is used nor is a given displacement the limit of air volume able to be pumped into it's capacity.

 

[Matt Bachand]

I tried to bust this myth of twice the flow at half the pressure before, but it was another thread.

In general it is impossible to flow more air at an equivalent or lower pressure, unless you increase the volume of the system, like by increasing RPM, or larger engine, etc....
.

Compressing air would be raising pressure. Perhaps you missed this.

 

[buddy]

Compressing air would be raising pressure. Perhaps you missed this.

YES, YES, but there is not more flow when one turbo pushes 10 psi vs another turbo pushing 10psi regardless of how large the turbo is. You cannot flow more air at the same or lower pressure, you have to increase pressure to increase flow through the system. Except as noted with exhaust efficiency.

 

[buddy]

This is true in a N/A engine. AIR COMPRESSES which in turn is the whole concept of forced induction......

Yeah, that is true, I messed that up a little while typing. Theoretically even though its compressed its still the same volume through the cylinder, and youve just increased the mass. The engine still flows only 1000CFM, but the turbo is pushing 2000 CFM to push twice atmospheric pressure. What went in does come out, just its more dense when it goes in the engine.

 

[GJF]

He is correct stating that "In general it is impossible to flow more air at an equivalent or lower pressure"

But..... instead of stating "unless you increase the volume of the system, like by increasing RPM, or larger engine, ect...."

Should have been ......."unless the pyhsical size of the compressor itself (which in turn would increase the overall volume)"

By increasing the size of the compressor in turn increases the volume able to be pumped into a given area which is then governed by the efficiency of the entire inlet tract.

 

[buddy]

Should have been ......."unless the pyhsical size of the compressor itself (which in turn would increase the overall volume)"

By increasing the size of the compressor in turn increases the volume able to be pumped into a given area which is then governed by the efficiency of the entire inlet tract.

Nope, compressor size does not matter in terms of flow, pressure is what matters. larger compressor at same pressure is not flowing any more air than smaller compressor.

Compressor size matters only to efficiency and potential pressure. So a larger compressor could pressureize more air, but then youre talking about running 15+ psi of boost, when you may have only been running the stock turbo at 15 and below.

The amount of air that can be pumped into any given space, is based on volume and pressure.

 

[GJF]

Yes, It is the same volume displacement wise. And no, the volume is greater just compressed into the same given area. Yes, pressure will be greater in the area but not from the compressor.

 

[Turbine Doc]

I tried to bust this myth of twice the flow at half the pressure before, but it was another thread.

In general it is impossible to flow more air at an equivalent or lower pressure, unless you increase the volume of the system, like by increasing RPM, or larger engine, etc....

.

Buddy,

Not a myth, possibly a difference of how we view the same data let's focus on the etc.

Since you didn't like my air compressor analogy before lets look at it slightly differently.

Removing all other dynamics (2) pails 1 gallon and 2 gallon, going into (2) receivers both at atmospheric pressure dumped at exact time, which one has more fluid in it>

The 2nd receiver has 1 gallon more in it, both at same pressure when admitted, same goes with the ATT bigger/more efficient wheel is the bigger pail putting in more fluid.

Say for simplicity the GM-X turbo is a 1.5 gallon pail, and the ATT is a 2 gallon pail with each rotation, at each turn there is still a .5 gallon delivery improvement with the ATT at same conditions.

Now I know you have issue with the claim of 2x delivery at same speed, that I can agree with you is a subjective statement and probably incorrect, to know with certainty what the real dynamic flow delta is we need some device for measuring air flow.

If it's only 1.5x, I'll take that as it is still an .5x or even if just .25x improvement and engine isn't struggling as hard to get it, it's all good.

What I can say there is more reserve boost available with the ATT past 1500rpm it happens more quickly with the ATT, than with my GM-X when cruising @ 70 mph my ATT does it with 1.5-2psi vs 2-4 psi required from the GM turbo.

IMO that would lend one to be able to say the ATT does more with less, that is gauge data driven, so it has to have some value as a good data point, is saying 2x more correct probably not, but by boost gauge it could appear that way and lead to discussions right or wrong it is 2x delivery, bottom line there is more delivery with the ATT at whatever final volumetric amount delta exists.

The rest of the stuff you cite is important to speed/efficiency at which the pails fill under restrictions imposed by dynamics of engine operations, if not the case why would we even need different sized turbos for different operating envelopes.