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Discussion Starter #1
I have a 318 SE 2003 facelift with some frustrating symptoms.
It feels like the slight loss of power when you have the air con on, also when accelerating from start it seems to bog down. If you do accelerate hard when you change gear there is a massive loss of power but only briefly.
Other symptoms are slight fluctuation on the idle but nothing drastic.
Generally speaking the car drives fine on motorways and has good economy and will tank along at a good speed but anything from start and you really notice power issues.
I have noticed some noise from the mid to rear section of the exhaust but cant imagine that would cause these problems.
I have thought about changing the fuel filter as I dont know its age. Plugs arnt all that old, air filter is recent and so is the oil and filter. Coils are new.
The only other thing that I know that could be an issue is some time ago it had some relays replaced and BMW said there were some fault codes store, namely knock sensor. Could this be relevant as I have never had a fault light.
cheers guys
 

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What gas are you using?
In my e30 318 I noticed a pretty noticeable loss of power with the a/c on. That's just how it is in lower power cars.
 

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Discussion Starter #4
thanks mate but what i was saying was that it feels like the ac is on when its not. i.e. i am getting the same king of power loss even when the ac is off
 

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My brother in law (who has a Bimmer track car and drives an Audi S5 as his daily driver) likes my car but has explained to me that E46's are what is called "Momentum Cars". Not quick off the line, but so well engineered that, when up to speed, handle just as well or better than most high performance cars. When it comes to cars, I tend to believe him. As an aside, I think premium gas just prevents "knock" in high compression engines. It doesn't give it more power. Am I wrong about this?
 

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My brother in law (who has a Bimmer track car and drives an Audi S5 as his daily driver) likes my car but has explained to me that E46's are what is called "Momentum Cars". Not quick off the line, but so well engineered that, when up to speed, handle just as well or better than most high performance cars. When it comes to cars, I tend to believe him. As an aside, I think premium gas just prevents "knock" in high compression engines. It doesn't give it more power. Am I wrong about this?
The cars are tuned to run off of high octane fuel. By running the proper fuel you allow the motor to achieve (or at least have the potential of achieving) its maximum potential.

Using anything less is handicapping the engine before you even leave the driveway.
 

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My brother in law (who has a Bimmer track car and drives an Audi S5 as his daily driver) likes my car but has explained to me that E46's are what is called "Momentum Cars". Not quick off the line, but so well engineered that, when up to speed, handle just as well or better than most high performance cars. When it comes to cars, I tend to believe him. As an aside, I think premium gas just prevents "knock" in high compression engines. It doesn't give it more power. Am I wrong about this?
In order to prevent knock, the ECU will retard the timing, this will cause a loss in power. Mind you it is fairly minor and will only occur if the engine is knocking in the first place. Higher octane fuels better protect against knock than lower octane fuels. The engine may develop full power on low octane fuel, but it will have a higher probability of knocking.
 

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In order to prevent knock, the ECU will retard the timing, this will cause a loss in power. Mind you it is fairly minor and will only occur if the engine is knocking in the first place. Higher octane fuels better protect against knock than lower octane fuels. The engine may develop full power on low octane fuel, but it will have a higher probability of knocking.
That's what I said. Lower octane fuels tend to detonate when highly compressed (hence the "knocking" you hear). Higher octane fuels will not detonate until the spark plug ignites the fuel/air mixture. I would think that retarding the timing would not have anything to do with pre-detonation. I think I will have to look this up and find out for sure 'cause I'm only guessing.:hmm:
 

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Here's the poop about octane rating of gasoline: Octane rating or octane number is a standard measure of the performance of a motor or aviation fuel. The higher the octane number, the more compression the fuel can withstand before detonating. In broad terms, fuels with a higher octane rating are used in high-compression engines that generally have higher performance. Octanes are a family of hydrocarbon that are typical components of gasoline. They are colourless liquids that boil around 125 °C (260 °F). One member of the octane family, isooctane, is used as a reference standard to benchmark the tendency of gasoline, petrol, or benzin fuels to resist self-igniting. Self-ignition leads to inefficiencies (or even engine damage) if it occurs during compression prior to the desired position of the piston in the cylinder as appropriate for valve and ignition timing. The problem of premature ignition is referred to as pre-ignition and also as engine knock, which is a sound that is made when the fuel ignites too early in the compression stroke.

Severe knock causes severe engine damage, such as broken connecting rods, melted pistons, melted or broken valves and other components. The octane rating is a measure of how likely a gasoline or liquid petroleum fuel is to self ignite. The higher the number, the less likely an engine is to pre-ignite and suffer damage.

The most typically used engine management systems found in automobiles today monitor the level of knock that is being produced by the fuel being used. In modern computer controlled engines, the timing of the ignition will be automatically altered by the fuel management system to reduce the pre-ignition to an acceptable level. So I stand corrected. The ECU does adjust the timing to reduce the knock (but doesn't eliminate it).
 

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That's what I said. Lower octane fuels tend to detonate when highly compressed (hence the "knocking" you hear). Higher octane fuels will not detonate until the spark plug ignites the fuel/air mixture. I would think that retarding the timing would not have anything to do with pre-detonation. I think I will have to look this up and find out for sure 'cause I'm only guessing.:hmm:
Pre-detonation and knock are two separate things. Knock is detonation occurring post spark but in front of the flame front travelling through the cylinder, pre-det is the cylinder contents exploding prior to the spark. Pre-detonation will very quickly destroy an engine whereas knock may cause little to no damage.
 

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If its power you need...
install freeflow and get rid of the two rear exhaust silencers. do not touch th one with cables on it. (it houses the catalyst conveter). put twin tail pieces at the end of the exhaust. 318's come with a single tip.

Get rid of the standard airfilter and install a K&N cone filter. its quite easy to DIY. if u can, get a tube that you fit on to the bumper( next to the foglight on the left, if you have a sports bumper). it will feed direct oxygen to the filter.

Get into your car, hit the gas pedal and release clutch quickly and you will hear your tyres screaming! they will leave marks on the road!!!!
 

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^not really sure about the 318 engines. But on the 6 cylinder e46 cars an unprotected cone filter is much less efficient than the stock cold air intake.
 
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