Upgrades that is 
So, I got this BMW E90 328 xDrive with 6-speed manual in December 2019. I was looking specifically E90 with N52 (last naturally aspirated I6 engine that BMW had). I had several criteria:
1. Must be manual.
2. Must have below 100k.
3. LCI (updated, so not older than 2009).
4. No iDrive.
5. HiD lights.
6. Sports package.
7. xDrive bcs. I would take it to ski.
So, after looking for a year since I got rid of X5 for Sienna, I found one in DC with 84,000 miles, flew there, and drove it back in two days to CO.
The first purchase was 16" wheels with Continental VikingCointact 7 snow tires running 205/55 R16.
Then in April, once COVID shut down everything, I embarked on an audio upgrade. That was the first thing as base audio that came with was blah:
1. Kenwood head unit.
2. Pioneer shallow subwoofers below front seats in encolusures that had BMW subwoofers.
3. 6 1/2 Pioneer speakers in the rear shelf instead of 4" speakers.
4. 4" mid and 1 1/2" tweeters in front doors (MB Quart mid, Pioneer tweeters).
5. JL Audio amp pushing regular speakers.
6. Pioneer amp pushing Subwoofers.
Old shelf speakers:
New shelf speakers:
Old vs. new subwoofer:
New Subwoofer in place:
So, the audio worked excellent! The reason why I went Kenwood HU is that it has a rear USB line that is 5ft long, so I ran it to the glove compartment to hook up iPod. I only use a physical connection as it is much better than Bluetooth.
Also, it has 6 5V outputs for amplifiers.
After that, next project was oil cooler. I had issues with oil temperature while I was tracking. Altitude is unforgiving and I know people who come from Texas with turbo engines on BMWs here to track, and regardless that they have oil coolers and it works in TX heat, here it is not sufficient. I did not want to go brick-style heat exchanger. I wanted radiator type that is found on N54/55 turbo models with a sport package. It is overkill for naturally aspirated N52, BUT, it has a thermostat that opens at 110c, so no problems warming up oil. Luckily, N51/52/53/54/55 engines share same oil filter housing and models with heat exchanger or thermostat just have opening on other side where you attach heat exchanger or thermostat that has two lines going in and out:
Oil filter housing with thermostat attached and lines going in and out:
The actual cooler is in the wheel well. Air goes through front where there is duct for brake cooling. Then duct separates to line for brakes and line that attaches to the radiator:
Oil cooler worked perfectly. Absolutely no oil temperature issues (I was running up to 300f when limp mode would kick in). It is sooo efficient, that I ran a 70-minute session at 102f at 5,100ft altitude and did not go over 255f.
Than suspension upgrades came:
1. Bilstein B6 struts and shocks. B6 are normal height and track rated (B8 are for lower vehicles). The reason I did not want to lower car is that it is my daily, I take kids to school, work, ski etc.
2. Front I had to go regular control arms etc. because it is xDrive. On RWD you can go M3 control arms that have bearing-style bushings. I just refreshed the front with all arms, sway bar bushings, toe rods, strut mounts etc.
3. Rear I had more options. Upper and lower wishbones can be from M3. They are forged aluminum and have bearing-style bushings. They also increase camber. I used Monroe upper and lower shock mounts. DUe to E90 coming with RFT, they use some kind of sponge to absorb RFT harshness. Since I ditched RFT, I wanted stiffer mounts and Monroe ($9 per wheel) is considered among the BMW crowd as the best upgrade.
4. Rear subframe bushings were replaced with Polyurethane performance ones from Powerflex which are stiffer than M3 ones.
5. Rear diff bushings are from M3. Polyurethane bushings in the rear diff. apparently, create whining noise.
Rear suspension:
After suspension, it was time for an engine.
First was air box. the US air box comes with two air filters. One is regular that you replace. Another one is charcoal which is integrated to meet CARB requirements. A popular upgrade is going European box, which has a mushroom-style filter inside a different box and no charcoal filter.
But, that box is like $300 for used and $400+ for new. But, I called my brother and he found one on a jank yard in Bosnia for $20, and sent it here for $40! Ha!!! Also, I replaced the intake hose with Turner one. That eliminates the resonator and provides crispier sound:
New air box with blue Turner intake hose:
So, I got this BMW E90 328 xDrive with 6-speed manual in December 2019. I was looking specifically E90 with N52 (last naturally aspirated I6 engine that BMW had). I had several criteria:
1. Must be manual.
2. Must have below 100k.
3. LCI (updated, so not older than 2009).
4. No iDrive.
5. HiD lights.
6. Sports package.
7. xDrive bcs. I would take it to ski.
So, after looking for a year since I got rid of X5 for Sienna, I found one in DC with 84,000 miles, flew there, and drove it back in two days to CO.
The first purchase was 16" wheels with Continental VikingCointact 7 snow tires running 205/55 R16.
Then in April, once COVID shut down everything, I embarked on an audio upgrade. That was the first thing as base audio that came with was blah:
1. Kenwood head unit.
2. Pioneer shallow subwoofers below front seats in encolusures that had BMW subwoofers.
3. 6 1/2 Pioneer speakers in the rear shelf instead of 4" speakers.
4. 4" mid and 1 1/2" tweeters in front doors (MB Quart mid, Pioneer tweeters).
5. JL Audio amp pushing regular speakers.
6. Pioneer amp pushing Subwoofers.
Old shelf speakers:
New shelf speakers:
Old vs. new subwoofer:
New Subwoofer in place:
So, the audio worked excellent! The reason why I went Kenwood HU is that it has a rear USB line that is 5ft long, so I ran it to the glove compartment to hook up iPod. I only use a physical connection as it is much better than Bluetooth.
Also, it has 6 5V outputs for amplifiers.
After that, next project was oil cooler. I had issues with oil temperature while I was tracking. Altitude is unforgiving and I know people who come from Texas with turbo engines on BMWs here to track, and regardless that they have oil coolers and it works in TX heat, here it is not sufficient. I did not want to go brick-style heat exchanger. I wanted radiator type that is found on N54/55 turbo models with a sport package. It is overkill for naturally aspirated N52, BUT, it has a thermostat that opens at 110c, so no problems warming up oil. Luckily, N51/52/53/54/55 engines share same oil filter housing and models with heat exchanger or thermostat just have opening on other side where you attach heat exchanger or thermostat that has two lines going in and out:
Oil filter housing with thermostat attached and lines going in and out:
The actual cooler is in the wheel well. Air goes through front where there is duct for brake cooling. Then duct separates to line for brakes and line that attaches to the radiator:
Oil cooler worked perfectly. Absolutely no oil temperature issues (I was running up to 300f when limp mode would kick in). It is sooo efficient, that I ran a 70-minute session at 102f at 5,100ft altitude and did not go over 255f.
Than suspension upgrades came:
1. Bilstein B6 struts and shocks. B6 are normal height and track rated (B8 are for lower vehicles). The reason I did not want to lower car is that it is my daily, I take kids to school, work, ski etc.
2. Front I had to go regular control arms etc. because it is xDrive. On RWD you can go M3 control arms that have bearing-style bushings. I just refreshed the front with all arms, sway bar bushings, toe rods, strut mounts etc.
3. Rear I had more options. Upper and lower wishbones can be from M3. They are forged aluminum and have bearing-style bushings. They also increase camber. I used Monroe upper and lower shock mounts. DUe to E90 coming with RFT, they use some kind of sponge to absorb RFT harshness. Since I ditched RFT, I wanted stiffer mounts and Monroe ($9 per wheel) is considered among the BMW crowd as the best upgrade.
4. Rear subframe bushings were replaced with Polyurethane performance ones from Powerflex which are stiffer than M3 ones.
5. Rear diff bushings are from M3. Polyurethane bushings in the rear diff. apparently, create whining noise.
Rear suspension:
After suspension, it was time for an engine.
First was air box. the US air box comes with two air filters. One is regular that you replace. Another one is charcoal which is integrated to meet CARB requirements. A popular upgrade is going European box, which has a mushroom-style filter inside a different box and no charcoal filter.
But, that box is like $300 for used and $400+ for new. But, I called my brother and he found one on a jank yard in Bosnia for $20, and sent it here for $40! Ha!!! Also, I replaced the intake hose with Turner one. That eliminates the resonator and provides crispier sound:
New air box with blue Turner intake hose:
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