Absurd exhaust system proposal for e53 X5 3.0i M54 // headers back for under $1,250?

[workingonit]

It seems that the M54B30 engine was made for a balance of torque and horsepower, using higher compression to offset the undersquare design (stroke greater than the bore). I've seldom had a "stroker" engine before, and my favored engine type is "oversquare" (piston diameter greater than the length of stroke), so I'm just saying that just adding headers is an expensive exercise on a semi-stock engine with tight exhaust parameters.

My Chevy race engines were high compression, large bore, short stroke (except for using longer rods on some), and high-lift cammed. My penultimate 427 engine, barely streetable, used 2" headers (3/4 length tubes), and a collector with swing-away exhaust pipes, where I could easily substitute collector extensions in a few minutes (even better if I had a place to detach and leave my pipes and mufflers behind). That engine was good for sub-12 second 1/4 miles, and lasted for quite awhile. Then it blew when the #4 con rod vaporized.

When I replaced it with another 427, it became too race-specific for the street, and it was a real challenge to work on...especially due to the 2.5" header primary tubes. I had to index my plugs, so I had to struggle to get past the large tubes (finally resorting to partially removing them), rerouting oil cooler lines and filter for clearance, and using fire-proof matting under my seat (and over the flexplate blanket) to be able to survive the high heat given off by the large full-length headers/collectors/extensions just under me. Sure, the massive exhaust was warranted, and it made more power than the earlier exhaust system, but it was a pure race motor, after all. I'd never had changed it, if it was just for a small % gain.

I plugged some numbers I found into an exhaust sizing calculator, and found out exactly how restrictive the M54B30 exhaust is...designed for balanced torque/power. Looks to me like it's comparable to using "peanut port" cylinder heads on my race engine (I used massive "square port" Brodix heads, opened even more by Reher-Morrison CNC-machining); I would've retained most of the torque, but lost most of the top-end horsepower that wins races.

If it's power you want, get bigger cam(s), valves, ports enlarged on the head, or if you just want the sound of power, then use by-passes, remove the central muffler (replace with an X-pipe, too), and forget the expensive header. Too much money spent & too many problems often accompany such a change, IMHO.

[bcredliner]

Originally Posted by IkirisTheX5

I wouldn't add headers unless they were a name brand that lists gains. It doesn't mean the claims will be accurate but that is why they build headers. The gain with the right exhaust isn't much. As an example the Dinan free flow muffler for a 3.0, when it was available, increased the HP by 5 at 6500 RPMs and TQ 4 also at 6500 RPMs.

Also bcredliner: the headers I was interested in are definitely not manufactured by a name brand, but from what they claim and I’ve read they are pretty good knock offs of the Supersorint E46 M54 headers which are equal length and claim to increase power by 20hp on a 330i. Yes, there are fitment issues regarding the O2 sensors and bolting up to stock exhaust, but those are the same complaints I hear about the $1,200 authentic ones as well and can be worked around fairly easily. Everyone says they bolt up to to the head just fine, which if they didn’t would obviously be a deal breaker. In summary, they sound kind of annoying, but effective and at 1/10th the price of the genuine ones still very tempting to try.

The gains on a 330i are not transferable to the M54 engine.

[bcredliner]

Originally Posted by IkirisTheX5

I like the way you think and electric exhaust cutouts are about as absurd as any exhaust mod I could think of. Do you happen to have them on yours or know anyone with a 3.0 X5 who has had them installed?

I’m a little confused on what your recommended placement is… you said: “install electric cutoffs equal length from the exhaust manifolds and past the first O2 sensor” —— I think it’s the O2 sensor part that’s tripping me up; aren’t those in the manifold? Maybe a better question to ask is if I delete the resonator at the same time should these come before the x-pipe?

In terms of performance, it’s funny but I couldn’t find much in way of definitive numbers for hp gains with cutouts, besides some guy with a 500hp Challenger who dyno tested it with cutouts open and closed and he reports a +10hp gain with them open.

I already have a “short ram induction” exposed cone style filter installed on her. It’s not one of the fancy aFe or Dinan ones but I’m sure it gets the job done all the same. I didn’t notice a particular increase in power from it until about 3500 rpm but that could also be just wishful thinking on my part. Sounds nice though.

Anyhow, thanks for the cutout advice. I am seriously considering it now! (Would just love to find another X5 owner who has already done it though.)

I installed QTP oval remote controlled exhaust cutouts. I have made many mods to my engine and sorely needed less back pressure. My goal was performance but the sound is amazing.

I don't remember anyone here that has installed cutouts on a 3.0 but I am certain they can be. It would be necessary to cut a hole in the exhaust pipes and weld the cutouts in place. I had a shop do the cutting and welding and I ran the wires and installed the control in the center console. Removing the resonators is more work than the muffler and easier to correct if you don't like the sound.

Location of O2 sensors. https://www.pelicanparts.com/BMW/tec...eplacement.htm

X pipe would be after the cutouts and before the resonators if you keep them. Most believe the X pipe is best. Note that the X pipe tends to produce a lower tone and the Y pipe tends to make it sound raspier and higher pitched. They both scavenge the exhaust, the X a little more than the Y.

When I do mods I do a value equation. What do I gain in performance per dollar spent? I suggest you calculate the costs of options you would like to consider and see what wins based on value. In the case of exhaust changes the gain won't be much whatever you do so the sound you want is part of the value.

The low restriction filter helps some. More if it draws colder air from outside the engine bay. Cooler air is more dense, engines love it. Any gain would be at higher RPMs when there is a greater demand for air. So after 3500 is likely when you would benefit the most. The key to getting the most out of low restriction filters is once you have made the change look for the next restriction before the air gets to the engine. As an example, Dinan is a complete system. Airbox to get only air from outside, the low restriction filter, a larger air intake tube, a larger diameter MAF and throttle body. That eliminates the air volume being throttled down anywhere. Coupled with the Dinan exhaust assures you are getting the max gain. Dinan also offered a matched tune.

[nick325xit 5spd]

Originally Posted by bcredliner

The gains on a 330i are not transferable to the M54 engine.

I'm trying to understand what you mean by this? It's the same engine.

[bcredliner]

Originally Posted by workingonit

It seems that the M54B30 engine was made for a balance of torque and horsepower, using higher compression to offset the undersquare design (stroke greater than the bore). I've seldom had a "stroker" engine before, and my favored engine type is "oversquare" (piston diameter greater than the length of stroke), so I'm just saying that just adding headers is an expensive exercise on a semi-stock engine with tight exhaust parameters.

My Chevy race engines were high compression, large bore, short stroke (except for using longer rods on some), and high-lift cammed. My penultimate 427 engine, barely streetable, used 2" headers (3/4 length tubes), and a collector with swing-away exhaust pipes, where I could easily substitute collector extensions in a few minutes (even better if I had a place to detach and leave my pipes and mufflers behind). That engine was good for sub-12 second 1/4 miles, and lasted for quite awhile. Then it blew when the #4 con rod vaporized.

When I replaced it with another 427, it became too race-specific for the street, and it was a real challenge to work on...especially due to the 2.5" header primary tubes. I had to index my plugs, so I had to struggle to get past the large tubes (finally resorting to partially removing them), rerouting oil cooler lines and filter for clearance, and using fire-proof matting under my seat (and over the flexplate blanket) to be able to survive the high heat given off by the large full-length headers/collectors/extensions just under me. Sure, the massive exhaust was warranted, and it made more power than the earlier exhaust system, but it was a pure race motor, after all. I'd never had changed it, if it was just for a small % gain.

I plugged some numbers I found into an exhaust sizing calculator, and found out exactly how restrictive the M54B30 exhaust is...designed for balanced torque/power. Looks to me like it's comparable to using "peanut port" cylinder heads on my race engine (I used massive "square port" Brodix heads, opened even more by Reher-Morrison CNC-machining); I would've retained most of the torque, but lost most of the top-end horsepower that wins races.

If it's power you want, get bigger cam(s), valves, ports enlarged on the head, or if you just want the sound of power, then use by-passes, remove the central muffler (replace with an X-pipe, too), and forget the expensive header. Too much money spent & too many problems often accompany such a change, IMHO.

I used to race corvettes. We started with small blocks and then went to an L88 big block largely because of the huge torque. It was beneficial both for road and drag racing.

My point about making sure you don't negatively impact torque, moreover choose what increases torque the most and will certainly also increase HP is because of the weight of an X5. if one is only concerned with performance on the street the first 60 feet will most likely determine a win or a loss.

[bcredliner]

Originally Posted by nick325xit 5spd

I'm trying to understand what you mean by this? It's the same engine.

Sorry, I read it wrong, I was thinking of 335 turbo engine. Gains usually have a direct correlation to beginning TQ/HP. However that depends on how restrictive the stock components were.

[nick325xit 5spd]

Originally Posted by bcredliner

Sorry, I read it wrong, I was thinking of 335 turbo engine. Gains usually have a direct correlation to beginning TQ/HP. However that depends on how restrictive the stock components were.

Stock manifolds and cats are pretty restrictive. There's a bunch of power on the table.

Now, whether it's worth the effort is another question.

[IkirisTheX5]

Well, you guys convinced me… …and truth be told I was never really setting out to build a sleeper AMG E63 killer (it seems the only way to truly make a m54 competition worthy is forced induction and that’s an expense and headache 🤕 I’m not willing to invest in), but the sound is very important to me so I decided to forego the headers for the moment and (after some pretty exhaustive research) decided to go in on a pair of BadlanzHPE SS electric exhaust cutouts - they have excellent reviews, strong materials, manufactured in the US, reasonably priced and a 5 year warranty. Along with those I ordered a pair of Cherry Bomb M-80’s, a stainless stamped x-pipe to replace the resonator, and finally - the cherry on top - my faux M3 quad 3.5” tips. I’m pretty sure I’ll get all the sound I was hoping for with this setup, and it’s plenty absurd to keep me entertained for awhile, although I’m already bracing myself to be underwhelmed in terms of any performance gains.

Thanks again for your input guys; it definitely pointed me in the right direction. I’m hoping for install to happen mid-next week. I’ll throw up a link with a before/after video of the sound and you guys can judge whether it was worth all the goofy trouble!

[bcredliner]

Good decision! If possible, a before and after video of the change would be great to hear. Revs, acceleration from zero and full throttle drive by.

[Happy]

Originally Posted by IkirisTheX5

it seems the only way to truly make a m54 completion worthy is forced induction and that’s an expense and headache

Very true! It is the only way to gain more power.

Expense, yes. Headache, no! The sweet sound of an M54 purring, is music to my ears.