3.0i Header Options

[crystalworks]

This should illustrate m52/m54 eBay header install.

https://youtu.be/Cc3DxEE-0pc

[e39_touring]

Everything bolted up perfectly, and I'm enjoying about 10% better mpg and what feels about the same increase in power.

It is tight in there, but I found room to use the 2 wrench/nut combo when screwing the studs back in. I used a combination wrench and a 1/4 ratchet with shallow and deep sockets depending on where I was working. Also, some were easier to get at from the top while others were easier to reach from underneath.

One other key is to buy two regular (non-locking) M7 nuts to screw the studs in. That way, when the stud is in, you can back one nut off slightly and unscrew both with your fingers.

[Bdc101]

Originally Posted by e39_touring

Everything bolted up perfectly, and I'm enjoying about 10% better mpg and what feels about the same increase in power.

Do you have data to back that up? Nothing about intake and exhaust mods should ever change MPG in gasoline engines. Power yes, mpg no. That's not absolutely always the case, but it's so rare that I'm always skeptical unless there are fuel logs showing it to be the case. (Not dash readings)

[e39_touring]

Originally Posted by Bdc101

Do you have data to back that up? Nothing about intake and exhaust mods should ever change MPG in gasoline engines. Power yes, mpg no. That's not absolutely always the case, but it's so rare that I'm always skeptical unless there are fuel logs showing it to be the case. (Not dash readings)

The trip computer is VERY accurate. Afterall, your ecu knows EXACTLY how much fuel it is injecting into the engine at any given time and how many miles since reset. By the trip computer, I could never do better than just shy of 21 mpg on highway trips, and now I'm getting just shy of 24 mpg on the same routes.

Intake and exhaust mods can very well change the efficiency. Ever hear of pumping losses? Think maintaining 600 deg temperatures in a catalytic converter is done without expending any energy? You often hear that an inefficient exhaust system only costs 2 or 3 hp or such and such, but when the vehicle only requires 20 to 30 hp to maintain it's speed on level ground, there's your 10%.

[Fifty150hs]

Originally Posted by e39_touring

The trip computer is VERY accurate. Afterall, your ecu knows EXACTLY how much fuel it is injecting into the engine at any given time and how many miles since reset. By the trip computer, I could never do better than just shy of 21 mpg on highway trips, and now I'm getting just shy of 24 mpg on the same routes.

Intake and exhaust mods can very well change the efficiency. Ever hear of pumping losses? Think maintaining 600 deg temperatures in a catalytic converter is done without expending any energy? You often hear that an inefficient exhaust system only costs 2 or 3 hp or such and such, but when the vehicle only requires 20 to 30 hp to maintain it's speed on level ground, there's your 10%.

I disagree. The trip computer is not accurate in my experience. I log all of my fuel ups and track my mileage. My OBD consistently over reports mileage by .4 miles per gallon. The ECU does know exactly how much fuel it's putting in the engine, but I don't think that is how the OBD calculates MPG. In fact, my scanner has a function that allows you to adjust the reporting accuracy of the OBD. Unfortunately, it only works in liters not gallons. I haven't been able to figure out how to make the adjustment correctly. The adjustments I tried only made it worse, so I went back to "neutral".

[lo_jack]

I got mine bolted to the head, but I'm still vband flanging my new cats to the end of my headers. If I can't figure out a good way to get from the cats to the stock x pipe, I might have to cut that out as well and put in a borla.

I figured out something interesting...no E53 exhaust manifold gasket has 12 holes per gasket in it. That means if you want to put OEM gaskets on headers for the sleeper look, you would have to drill press the gaskets carefully. Also, the gaskets that come with ebay headers look suspect, so you can use E36 328i gaskets, which are MLS gaskets with all 24 holes. No heat shields though. If you wanted to (I thought about this but did not have the patience) you could chop down the OEM E53 gaskets and mount them outside the headers.

Getting the nuts on with the heat shields on is terrible, though, if anyone is wondering.

[andrewwynn]

Less restriction will give you less power loss means more power to the ground vs heat loss. This will mean better mpg but 10% not likely at all. If that was possible all the X5 would have high mpg headers.

[Bdc101]

On gasoline engines, you restrict them using the throttle. If you open up the exhaust, the engine will pump more air/fuel mixture at any given throttle position. But when cruising (ie not at WOT) you will just compensate by opening the throttle less than before. The throttle is called a restrictor plate for this reason. There's generally no efficiency gain to intake/exhaust mods because of this. Power gains, though, are obvious.



Diesel engines, that is not the case.

[andrewwynn]

The efficiency gains will therefore only really present at wot. The gain will therefore go more toward faster 0-60 than farther range. Power is energy/time. If you don't use the energy quickly (higher power) it will mean more time to consume or higher mpg

[Bdc101]

Power is energy per unit time. Efficiency is energy out divided by energy in. Higher power does not mean higher efficiency. It's true that you might see higher efficiency at WOT, but nobody drives at WOT all the time, so it won't make a difference.


Meanwhile the rest of Xoutpost thinks "nobody drives at WOT all the time? Challenge accepted..."