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  #31  
Old 08-23-2013, 07:11 AM
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JRW160 JRW160 is offline
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I don't think a 2002 LTR even has an o2 sensor
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  #32  
Old 08-30-2013, 11:47 AM
Quinten Quinten is offline
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Quote:
Originally Posted by amcmac View Post
How is the FAE any different than a sterndrive in the case of the exhaust routing and back pressures?
That's a good question. :s
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  #33  
Old 08-30-2013, 02:15 PM
FrankSchwab FrankSchwab is offline
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For those who ask whether reducing a pair of 3-4" exhausts to a single, apparently smaller, output adds backpressure, the answer is "Probably".

Can that damage a Small Block Chevy like the OP asked? Certainly not. Think of where that engine was originally designed to go - in a Chevy car or truck with crappy exhaust manifolds, a Cat, and a small single exhaust. How much backpressure do you think it has in that Factory design?

If you want to argue that an FAE might impact the horsepower available at WOT, or increase fuel consumption at a particular performance level due to poor matching of intake/cam/valves/exhaust, fine, keep the arguments there.
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  #34  
Old 08-30-2013, 05:54 PM
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Quote:
Originally Posted by amcmac View Post
How is the FAE any different than a sterndrive in the case of the exhaust routing and back pressures?
The exhaust on a stern drive goes out through the prop and the path is pretty clear of obstructions. One difference is that not all of the cooling water goes out with the exhaust- it usually exits from the water ports near the transom/gimbal.
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  #35  
Old 08-30-2013, 09:00 PM
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Quote:
Originally Posted by FrankSchwab View Post
For those who ask whether reducing a pair of 3-4" exhausts to a single, apparently smaller, output adds backpressure, the answer is "Probably".

Can that damage a Small Block Chevy like the OP asked? Certainly not. Think of where that engine was originally designed to go - in a Chevy car or truck with crappy exhaust manifolds, a Cat, and a small single exhaust. How much backpressure do you think it has in that Factory design?

If you want to argue that an FAE might impact the horsepower available at WOT, or increase fuel consumption at a particular performance level due to poor matching of intake/cam/valves/exhaust, fine, keep the arguments there.
Works fine. Correct Craft has been doing it for years.

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  #36  
Old 08-30-2013, 09:04 PM
maxpower220 maxpower220 is offline
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Go look at any 1990-1997 Chevy or GMC truck. The exhaust with will be a 2.5" single exhaust going through a 3 foot long muffler. Virtually every 5.7 liter chevy engine in a car is exactly that way. No issues with backpressure.

Call Larry Mann at FAE, he has specific numbers on pressures, and any losses of engine power for several models.

The FAE did not spin a bearing or destroy a rod. Bad luck from the factory, too little oil, no oil change, or something else did that.
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  #37  
Old 09-01-2013, 09:36 PM
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Thanks for everyone's input. I feel the same way. The guys at Rambo had never seen a FAE before and seemed eager to jump on it as the source of the problem. Great point mentioned above about the 5.7L chevy's with all the restrictive automotive exhausts.
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  #38  
Old 09-01-2013, 10:18 PM
H2ORidr H2ORidr is offline
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Quote:
Originally Posted by markmcfarland View Post
There is another thread on here that says what this is called. It is something like "the vermillion effect". I know that's not the right word but its something like that.
I may be wrong but I believe it is the venturi affect. http://en.wikipedia.org/wiki/Venturi_effect

We use venturi vacuums in the lab back in my grad school days. Each sink has a nozzle that narrowed down to about 1/4" diameter and attached to the side about 4" up was a side adapter for a hose. You could get some really strong vacuums on that side hose with the water running through the faucet full out.



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  #39  
Old 09-02-2013, 02:27 PM
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FourFourty FourFourty is offline
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Quote:
Originally Posted by j.mccreight@hotmail.com View Post
The only way an ECM can compensate for a difference in air flow is to have a sensor in the trailing edge of said FAE which there is not, therefore the ECM is NOT adjusting for the FAE and only operating only to oem specs.
If back pressures are higher, Manifold absolute pressure will be higher as well. The ECU would compensate for that. With a "Speed Density" fueling system, like our boats have, the MAP sensor measures intake manifold pressure, in order to make fueling adjustments, based on the load, and flow of the engine. If you restrict the exhaust flow, you reduce the efficiency of the "pump", and the inlet side will have a corresponding change in pressures.

Not saying that the corresponding changes will be as "spot on" as the normal parameters on an engine without FAE, however, it does compensate for things like that.

Quote:
Originally Posted by DHPRO View Post
O2 sensors should adjust to account for changes in flow (again, I have no idea how marine sensors differ from cars). Those OEM spec'd boats would be interested to see if they have any diff mapping in the fuel tables or timing as a result. If not, then I'd feel lots more comfortable adding it to mine.
O2 sensors will only make microscopic changes to an engines fueling, and ONLY under a sustained, low throttle, cruising condition. The O2 sensors are ignored, by the ECU, under any kind of load above 1/8-1/4 throttle. They are also ignored at idle. They would not help compensate for an FAE at all.

Same goes in a car engine- You are cruising along at 50mph on a nice straight, flat, highway. Your foot is just barely pressing the throttle, and holding it steady. At this time, the ECU will take a look at your O2 readings (goes into closed loop), and make 1-3% changes in the short term fueling of the engine. As soon as you either let off, or put any kind of load, above 1/4 throttle, the ECU immediately ignores O2 readings (switches to open loop), and uses MAF, (or MAP sensor, depending on fueling type. Some engines run both), Intake air temp, engine temp, RPM, and throttle position, to make adjustments to fueling.

Because of the way boats are used, and how they are constantly under heavier loads, an O2 sensor is ignored 99.9% of the time.

Quote:
Originally Posted by j.mccreight@hotmail.com View Post
How could O2 sensors adjust for added exhaust tubes, changes in flow etc. when they aren't even there (after the FAE). BTW the "sensors" on engines don't compensate for air flow or the like, the characteristic (or flow) of an engine is preprogrammed in the ECM, the only thing an O2 sensor does is measure the amount of Oxygen in the exhaust gases and reports to the ECM then the ECM makes adjustments to the air/ fuel mixture, flow has nothing to do with it.
You are right about the O2 sensor, however, like I said above, they absolutely can compensate for changes in air flow. They absolutely have to, otherwise, you would have to rewrite the ECU, with another program, every time you changed elevation, or even temperature outside....... Not to mention, the flow characteristics, of an engine, change over its lifetime.

Flow has EVERYTHING to do with it. Changes in elevation, outside temperature, engine temperature, backpressures, and intake restrictions (dirty air filter), all effect the FLOW of an engine. They are designed to deal with a wide range of changes. And sure, there is a limit to what it can compensate for, but they leave a pretty healthy cushion.


With all of that said, no way did the FAE take that connecting rod out.....
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  #40  
Old 09-02-2013, 10:23 PM
FrankSchwab FrankSchwab is offline
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Just thought I'd throw in some of the charts from the Fresh Air Exhaust Web site:

Speed with and without FAE:


Back pressure (2 PSI without, 3 PSI with):


So, yes, there is an increase in back pressure at WOT, and it appears a few mph reduction in top speed.
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