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04’ 325i with manual 5 speed
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Discussion Starter · #1 ·
Alright, I recently switched over to the dark side and picked myself up an 04’ 325i (with manual trans) for cheap and I’ve been fairly happy so far, just trying to patch up the oil and coolant seeping from every orafice. But after driving for a week I’ve found myself looking for a little more power. I’ve looked all over for a good forum with some advice to squeeze some extra power, but I can’t find anything within the last decade. So anyone got any good ways to get some more get up and go without breaking the bank (or buying an M3 or 330i)
 

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‘89, ‘03 and ‘98 E39
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443 Posts
I can’t help you with mods, I do suggest:

New VANOS seals
Check age of 02 sensors
See how dirty the injector tips are
Make sure spark plugs are fresh
Consider new coils if they are old, may not make any difference

Also, yeah, it’s not a drag racer but I have fun with mine because I have the engine running the way it should and I installed stiff shocks/struts (B6). The car is very responsive, quick/light on its feet, precise, and fun to drive. Even though it’s not “fast” I still do everything faster than most everyone around me on the streets. My favorite is a green arrow left turn onto a divided highway. I’m well into 2nd gear and pulling some g’s at WOT leaving everyone in my dust.
 

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2004 325i automagic
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^ +1

It's not going to be a drag racer ... if the engine is running right (no vacuum leaks, good O2 sensors, etc.), then all you can really do is swap in a rear diff from an auto car, which will raise rpms on the highway though, or ultimately forced induction of some kind (supercharger or turbo). You could also swap in a 3 liter engine (or get a 330i) which will give you almost 40 more hp.

What are your fuel trims? Vacuum leaks and such can drain a surprising amount of power, so focusing on refreshing things can pay dividends.
 

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04’ 325i with manual 5 speed
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17 Posts
Discussion Starter · #4 ·
I can’t help you with mods, I do suggest:

New VANOS seals
Check age of 02 sensors
See how dirty the injector tips are
Make sure spark plugs are fresh
Consider new coils if they are old, may not make any difference

Also, yeah, it’s not a drag racer but I have fun with mine because I have the engine running the way it should and I installed stiff shocks/struts (B6). The car is very responsive, quick/light on its feet, precise, and fun to drive. Even though it’s not “fast” I still do everything faster than most everyone around me on the streets. My favorite is a green arrow left turn onto a divided highway. I’m well into 2nd gear and pulling some g’s at WOT leaving everyone in my dust.
Thanks for the recommendations mate! I think this is exactly what I need, It’s been throwing a code for advanced exhaust timing or something of that nature and I kind of assumed that it was due to a vanos problem, I’ll definitely be doing this soon.
 

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04’ 325i with manual 5 speed
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17 Posts
Discussion Starter · #5 ·
^ +1

It's not going to be a drag racer ... if the engine is running right (no vacuum leaks, good O2 sensors, etc.), then all you can really do is swap in a rear diff from an auto car, which will raise rpms on the highway though, or ultimately forced induction of some kind (supercharger or turbo). You could also swap in a 3 liter engine (or get a 330i) which will give you almost 40 more hp.

What are your fuel trims? Vacuum leaks and such can drain a surprising amount of power, so focusing on refreshing things can pay dividends.
I’m not sure about the fuel trims but there’s no vacuum leaks, I think @89325iguy was spot on with the vanos seal problem, I’m reseal everything and maybe throw in some new solenoids. I haven’t heard about switching the diff from an auto, is it just a shorter final gear or what?
 

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2004 325i automagic
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I’m not sure about the fuel trims but there’s no vacuum leaks, I think @89325iguy was spot on with the vanos seal problem, I’m reseal everything and maybe throw in some new solenoids. I haven’t heard about switching the diff from an auto, is it just a shorter final gear or what?
Do the vanos seals, but hold off on the solenoids unless you know they are problematic. They are pricey, and not the most common issue to justify changing them just because.

As for the auto rear diff, yes they have shorter gear and will get to higher revs (and thus more power) quicker than the manual rear diffs. It gives the appearance of more power so to speak. You will lose out when cruising on the highway though as the engine will be at higher revs.

I'm not recommending it necessarily, just pointing it out. You would need to be mindful of possible compatibility issues between the diff flanges relative to driveshaft and cv joint flanges, since there are differences.

Something to look into, plenty of info on this, especially on the auto to manual transmission swap threads.
 

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2002 BMW E46 330i
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571 Posts
Arguably the cheapest way to get a little extra power is some tuning. Now I know to many tuning is this scary thing with a high chance of bending rods or shattering pistons, but all it requires is a laptop and a obd2 usb cable. The software to tune is free and there’s lots of community support to give you advice if you wanna go down that route. Also it’s kinda addicting and once you get into it, you’ll never get out and it will overtake your willpower.


Sent from my iPhone using E46Fanatics
 

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04’ 325i with manual 5 speed
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17 Posts
Discussion Starter · #12 ·
Do the vanos seals, but hold off on the solenoids unless you know they are problematic. They are pricey, and not the most common issue to justify changing them just because.

As for the auto rear diff, yes they have shorter gear and will get to higher revs (and thus more power) quicker than the manual rear diffs. It gives the appearance of more power so to speak. You will lose out when cruising on the highway though as the engine will be at higher revs.

I'm not recommending it necessarily, just pointing it out. You would need to be mindful of possible compatibility issues between the diff flanges relative to driveshaft and cv joint flanges, since there are differences.

Something to look into, plenty of info on this, especially on the auto to manual transmission swap threads.
Hey, I’m doing the research on the VANOS seals now, but I’m not sure who to buy them from, I don’t want to get shafted with some bad seals and be back to square one. Any recommendations on a good site/manufacturer
 

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2004 325i automagic
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3,861 Posts
I went with Beisan Systems. They originally developed the replacement vanos seals and put a lot of effort into finding a good replacement seal compound. They have a good reputation.
 

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E30M3 Race F10 535 R1150Rt M Coupe
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I went with Beisan Systems. They originally developed the replacement vanos seals and put a lot of effort into finding a good replacement seal compound. They have a good reputation.
The original. And his instructions are great, so support him.
 

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04’ 325i with manual 5 speed
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17 Posts
Discussion Starter · #15 ·
I went with Beisan Systems. They originally developed the replacement vanos seals and put a lot of effort into finding a good replacement seal compound. They have a good reputation.
Do you by any chance remember where you got them from? Like what website, because I’ve seen their products on a few websites that were a little seedy to say the least and I don’t really have getting my credit card information stolen in the agenda this week
 

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Super Moderator
2004 325i automagic
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3,861 Posts
Do you by any chance remember where you got them from? Like what website, because I’ve seen their products on a few websites that were a little seedy to say the least and I don’t really have getting my credit card information stolen in the agenda this week
Order direct from his website:


He also has a very detailed DIY writeup of the whole process. Remember to be aware of the reverse threaded screws ... you DO NOT want to turn those the wrong way.

The 50s Kid on YouTube also has a great how to video.
 
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