Another ? about FRA mod
#1
Launching!
Thread Starter
Join Date: Apr 2005
Location: Wausau, WI
Posts: 253
Likes: 0
Received 0 Likes
on
0 Posts
Another ? about FRA mod
Is it possible to get worse gas mileage cuz of this mod? Maybe its cuz it allows the hot air coming off the radiator directly in the intake?
#2
TECH Enthusiast
iTrader: (18)
Join Date: Nov 2004
Location: Salado, TX
Posts: 603
Likes: 0
Received 0 Likes
on
0 Posts
I think I actually get a little bit better gas mileage with my FRA. Hot air should also improve your gas mileage. Hot air=less oxygen therefore you need less fuel to get the right mixture.
#6
11 Second Club
Originally Posted by rollinna65
Hot air=less oxygen content, therefore your car dumps less gas to get the desired a/f ratio.
That's the way I see it anyway.
That's the way I see it anyway.
Trust me, you don't want your intake air to be hotter.
And before someone asks, the reason people often get worse mileage in the winter is because the car spends more time cold, in open loop, running rich and inefficiently.
#7
TECH Addict
Originally Posted by blkZ28spt
Hot air, less oxygen. Less oxygen, less efficiency. The engine will have to work harder/spin faster, and that hurts gas mileage.
Trust me, you don't want your intake air to be hotter.
And before someone asks, the reason people often get worse mileage in the winter is because the car spends more time cold, in open loop, running rich and inefficiently.
Trust me, you don't want your intake air to be hotter.
And before someone asks, the reason people often get worse mileage in the winter is because the car spends more time cold, in open loop, running rich and inefficiently.
Except for the bold bit, but thats a different reason.
Originally Posted by Roger Bywater, ex Senior Development Engineer at Jaguar Cars
The rule about air temperature is simple, cool for power (maximum charge density), hot for economy (minimum charge density to reduce losses due to throttling).
Trending Topics
#9
I asked my mechanic about the EGR and he said it lowers combustion chamber temps, like throwing ash on a fire (I really didn't understand that either). So I assumed it wasn't there for polution reasons but to help detenation from occuring. To be honest I'm still confused.
#10
11 Second Club
Originally Posted by 300bhp/ton
In every sense of the word the above information is WRONG!
Except for the bold bit, but thats a different reason.
Except for the bold bit, but thats a different reason.
What is the source of this quote?
#11
TECH Enthusiast
iTrader: (18)
Join Date: Nov 2004
Location: Salado, TX
Posts: 603
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by rednecks70
I asked my mechanic about the EGR and he said it lowers combustion chamber temps, like throwing ash on a fire (I really didn't understand that either). So I assumed it wasn't there for polution reasons but to help detenation from occuring. To be honest I'm still confused.
#12
TECH Addict
Originally Posted by blkZ28spt
So what are throttling losses, and why are they so large that reducing them with hot/thin air improves mileage?
What is the source of this quote?
What is the source of this quote?
AJ6 Engineering
However, I'll be honest there is a thread of truth in your claim, but for slightly different reasons. It just depends on how you view it. In terms of pure engine efficiency the colder the intake air the bigger the bang and thus more fuel is required so the engine will become less economical. Also when an engine is cold, an intake of hot or hotter air can be a benefit and help the engine run better and more economical, hence hot water is pumped thru the TB. Some older cars would also have an air intake from over the exhaust manifold for similar result.
But as you pointed out, hotter intake air (due to reduced charge density, the particles are futher a part) reduces power. If you have less power you may drive harder to maintain the same performance, thus increasing fuel consumption.
However if the engine was kept at a constant rpm (say running at 55mph non stop for 3 hours on a level gradiant) then the engine would be more fuel efficent with warmer intake temperatures.
#13
TECH Addict
Originally Posted by CHEVYXTREME_00
The EGR recycles the unused gas in your exhuast making it cleaner so less pollution.
Exhaust Gas Recirculating Valves
What are they? What do they do? How do they fail??
EGR Valves have been around for a long time. Way back in 1972 GM used them in an attempt to reduce emissions of oxides of nitrogen (NOx) which were a major cause of air pollution, mainly photochemical smog, that kind of smog which is formed when strong sunlight shines down on the exhaust gasses we puke out of our tailpipes by the billions of cubic feet a day.
A short chemistry lesson is in order here. It was discovered way back when, that high combustion chamber peak temperatures (the really short duration high temperatures near the end of the combustion process) caused oxygen and nitrogen to combine chemically and form these oxides of nitrogen mentioned above. Most of the anti-pollution devices of the day did a pretty good job of reducing the other bad by-products of combustion, namely excessive hydrocarbons and carbon monoxide, however they tended to induce the formation of oxides of nitrogen. Something had to be done else we would all die of smog diseases.
The automotive engineers figured that they needed to do something to lower the peak combustion temperatures which only occurred under certain high load driving conditions. They figured they could do so at the expense of power and fuel economy but what the heck, ya can't have everything! If they could only add something to the combustion chamber that would act like sort of a fire extinguisher to cool the combustion temperatures that would do it.
So they invented a way to allow some very inert gas to get back into the combustion chamber only when needed. They needed a source of this gas - it wasn't air, cuz that contains oxygen and nitrogen which caused the problem in the first place. So they chose carbon dioxide. Where to get a supply of carbon dioxide . . . ??? Hmmmm, how about the exhaust system? That is mainly carbon dioxide and water (plus a zillion other noxious chemicals) Suppose we allow some of the exhaust gas to get back into the intake manifold under strict control and only when we need it? That would cool the combustion chamber and prevent the formation of the NoX. Maybe we should call it recirculated exhaust gas (REG??). But a guy named Reginald voted no cuz he didn't want his name associated with a car part, so they called it exhaust gas recirculation (EGR) since there was nobody around with that name.
Now we understand why it is there. And we understand what it does. So what can go wrong with it and what are the symptoms??
It's really pretty simple - it can be open when it isn't supposed to be, or it can be closed when it is supposed to be open. Not rocket science, but it is science. If it is open when it is not supposed to be open, at idle for instance, It will act like one monster vacuum leak and the engine will not idle or will idle really roughly. If it doesn't open when it is supposed to open you will probably experience a symptom of "pinging" or "knocking" since the combustion chamber temperature will be higher than normal (one of the main causes of pinging in an engine).
There are a zillion different types of EGR valves some of which work strictly on vacuum, and some which work on a combination of vacuum and pressure. Some have electronic controls, some have mechanical controls. I won't go into detail here about all the different types but suffice it to say that most can be checked by looking inside to see if the plunger shaft is stuck open or doesn't move when the engine is revved up (after it is warmed up). Replacement is probably the easiest part since most are held in by two small bolts and have a vacuum line connected to it. The hard part is whipping out your Visa card to pay for it since most of them will drain your reserves in a hurry!
What are they? What do they do? How do they fail??
EGR Valves have been around for a long time. Way back in 1972 GM used them in an attempt to reduce emissions of oxides of nitrogen (NOx) which were a major cause of air pollution, mainly photochemical smog, that kind of smog which is formed when strong sunlight shines down on the exhaust gasses we puke out of our tailpipes by the billions of cubic feet a day.
A short chemistry lesson is in order here. It was discovered way back when, that high combustion chamber peak temperatures (the really short duration high temperatures near the end of the combustion process) caused oxygen and nitrogen to combine chemically and form these oxides of nitrogen mentioned above. Most of the anti-pollution devices of the day did a pretty good job of reducing the other bad by-products of combustion, namely excessive hydrocarbons and carbon monoxide, however they tended to induce the formation of oxides of nitrogen. Something had to be done else we would all die of smog diseases.
The automotive engineers figured that they needed to do something to lower the peak combustion temperatures which only occurred under certain high load driving conditions. They figured they could do so at the expense of power and fuel economy but what the heck, ya can't have everything! If they could only add something to the combustion chamber that would act like sort of a fire extinguisher to cool the combustion temperatures that would do it.
So they invented a way to allow some very inert gas to get back into the combustion chamber only when needed. They needed a source of this gas - it wasn't air, cuz that contains oxygen and nitrogen which caused the problem in the first place. So they chose carbon dioxide. Where to get a supply of carbon dioxide . . . ??? Hmmmm, how about the exhaust system? That is mainly carbon dioxide and water (plus a zillion other noxious chemicals) Suppose we allow some of the exhaust gas to get back into the intake manifold under strict control and only when we need it? That would cool the combustion chamber and prevent the formation of the NoX. Maybe we should call it recirculated exhaust gas (REG??). But a guy named Reginald voted no cuz he didn't want his name associated with a car part, so they called it exhaust gas recirculation (EGR) since there was nobody around with that name.
Now we understand why it is there. And we understand what it does. So what can go wrong with it and what are the symptoms??
It's really pretty simple - it can be open when it isn't supposed to be, or it can be closed when it is supposed to be open. Not rocket science, but it is science. If it is open when it is not supposed to be open, at idle for instance, It will act like one monster vacuum leak and the engine will not idle or will idle really roughly. If it doesn't open when it is supposed to open you will probably experience a symptom of "pinging" or "knocking" since the combustion chamber temperature will be higher than normal (one of the main causes of pinging in an engine).
There are a zillion different types of EGR valves some of which work strictly on vacuum, and some which work on a combination of vacuum and pressure. Some have electronic controls, some have mechanical controls. I won't go into detail here about all the different types but suffice it to say that most can be checked by looking inside to see if the plunger shaft is stuck open or doesn't move when the engine is revved up (after it is warmed up). Replacement is probably the easiest part since most are held in by two small bolts and have a vacuum line connected to it. The hard part is whipping out your Visa card to pay for it since most of them will drain your reserves in a hurry!
#14
12 Second Club
iTrader: (1)
Join Date: May 2005
Location: Bradenton, FL
Posts: 684
Likes: 0
Received 0 Likes
on
0 Posts
Ok. That being said. FRA does bring in cooler air, and increases power.
Warmer air CAN increase fuel economy.
All in all, the added air flow from FRA seems to increase fuel economy on the HWY for most people.
Bottom line, just do it.
Warmer air CAN increase fuel economy.
All in all, the added air flow from FRA seems to increase fuel economy on the HWY for most people.
Bottom line, just do it.
#15
11 Second Club
Without having read that link yet, here's my problem with understanding.
Take the car at a constant speed/rpm, let's say using cruise control. I don't see the oxygen intake being based solely upon the density of the intake air. It is going to require a certain amount of power to sustain that speed, correct? If the air is more dense (colder), wouldn't the throttle simply open less than it would if the air was less dense (hotter)? Why doesn't the throttle simply open as far as it needs in order to produce the power needed to maintain speed?
Take the car at a constant speed/rpm, let's say using cruise control. I don't see the oxygen intake being based solely upon the density of the intake air. It is going to require a certain amount of power to sustain that speed, correct? If the air is more dense (colder), wouldn't the throttle simply open less than it would if the air was less dense (hotter)? Why doesn't the throttle simply open as far as it needs in order to produce the power needed to maintain speed?