F85 Rotors on my F15? Exhaust upgrade necessary?

[papadooks]

Working on building up a tuned / full bolt on f15 n55 (s35i). Already have a bm3 stage 1 going, and I'm shocked by the improvement it has offered. Next steps are going to be picking up ER charge pipes and downpipe, drop in filter, and one step colder plugs. My buddy is insistent that I should upgrade my brakes and exhaust right away, and I'm looking for guidance on how to make this car a monster without breaking the bank.

On the brakes:

My buddy told me that with larger rotors and new/better brake pads, my oem calipers should be just fine (plus we'll powder coat them to add a little something to the aesthetic). On an older make-your-own-MPBK knockoff thread, someone posted that F85 rotors fit the F15 just fine. For my budget brake upgrade, I'm thinking about picking up OEM F85 rotors, but I have no idea if my oem calipers will fit on there or if I'll need something larger. Alternatively, is there a larger-than-oem rotor I can go to that is reasonably priced (say, under $150 each) and will improve braking performance adequately?

On the exhaust:

Is it necessary? All of my research on here seems to tell me that people usually just do the charge pipes and down pipes, and maybe add an MPE if they want something loud, but that exhaust upgrade isn't improving performance. My buddy insists that an upgraded exhaust is a must to make sure the car is breathing correctly. Plan is to go to a stage 2 tune once I've got the bolt-ons in place.

That also reminds me, BM3 suggests you should add an HPFP if you want to use their stage 2++ OTS tune. Is an HPFP necessary with a stock turbo?


Appreciate any help yall can offer. Have done a lot of reading on this forum and thought I had it mostly figured out until my buddy weighed in.

[RED_Y_]

For brakes I would recommend you check this thread out first:
https://f15.bimmerpost.com/forums/sh....php?t=1464952

[papadooks]

Originally Posted by RED_Y_

For brakes I would recommend you check this thread out first:
https://f15.bimmerpost.com/forums/sh....php?t=1464952

Thank you my friend! I did read that one.

[beattiecj]

Just adding bigger rotors won’t make any difference if you’re still using the same 1 pot caliper same braking surface, plus I don’t see how that would fit. Just do the e70 m or 6pot upgrade.

The stock exhaust I believe is 3 inch stainless hard to beat unless you want louder exhaust, I’d stick with your current plan.

HPFP not sure, I’d look at common N55 upgrades people have done on other cars with the n55.

Glad to hear the BM3 stage 1 makes a huge difference going to do that soon.

Upgrade the charge pipes to aluminum and plugs you’ll have a solid reliable ride. At some point you’ll get too deep and wish you just got a 50i lol.

[papadooks]

Originally Posted by beattiecj

Just adding bigger rotors won’t make any difference if you’re still using the same 1 pot caliper same braking surface, plus I don’t see how that would fit. Just do the e70 m or 6pot upgrade.

The stock exhaust I believe is 3 inch stainless hard to beat unless you want louder exhaust, I’d stick with your current plan.

HPFP not sure, I’d look at common N55 upgrades people have done on other cars with the n55.

Glad to hear the BM3 stage 1 makes a huge difference going to do that soon.

Upgrade the charge pipes to aluminum and plugs you’ll have a solid reliable ride. At some point you’ll get too deep and wish you just got a 50i lol.

Appreciate the advice. ER charge pipes and catless downpipe are on my list. I’m not looking to make it particularly loud, but I do want to maximize the performance (on a budget since I’m not trying to get too deep hah). I like the current sound and I understand it will get throatier with the catless dp. I’m cool with that but not trying to crank the volume to an obnoxious level.

You will not regret the BM3 tune. Car already feels like a new machine at stage 1. Also, once you buy it, make sure you perform the transmission tune as well. I wasn’t even aware of it when I bought it, so it was a nice surprise. Makes for faster and smoother shifting.

[dentprotony@gmail.com]

Probably best option all around, i am actually finalizing a 370mm rear rotor redesign, so this will be much bigger brake set up and rotors will still cost a fraction of the mkit. Also lighter as well.

[papadooks]

Originally Posted by dentprotony@gmail.com

Probably best option all around, i am actually finalizing a 370mm rear rotor redesign, so this will be much bigger brake set up and rotors will still cost a fraction of the mkit. Also lighter as well.

You’re the man. You were already on my radar too. I have your brake kit thread bookmarked already. Was hoping to find a more budget (but obviously less capable) alternative to your kit, but I may yet be circling back to you soon brother.

[dentprotony@gmail.com]

Originally Posted by papadooks

You’re the man. You were already on my radar too. I have your brake kit thread bookmarked already. Was hoping to find a more budget (but obviously less capable) alternative to your kit, but I may yet be circling back to you soon brother.

50i rotors are largest without going to full ///M, but they are heavy. 50i calipers are largest stock, or you can use g05 calipers but you have to space them out and thats kinda sketchy in my book. Otherwise thats about it. You can also find front f10 m5 calipers on ebay and get f10 m5 rotors, i can supply brackets to make all these work together

[Maverik259]

I would immediately stop listening to your “buddy.” You can’t change the size of the rotor without changing the caliper as well. That’s red flag #1.
As far as exhaust. Not gonna get you far with that i6. Certainly not necessary. Removing cats and resonator will free up some flow but you’re not gonna need too and the MPE is NOT loud by any means.

[papadooks]

“Thanks”

[sukhk527]

You should take a look at my build thread, it’ll answer a lot for the questions you’re asking about building a 35i. But on the note of brakes, no the f85 rotors are not a simple plug and play on a 35i two piston rotor , not even a little bit.

Your options include bolting on a 50i front brake setup, doing a Brembo upgrade like I did from dentprotony@gmail.com or the MPBBK from BMW. A few other off the shelf options like Brembo GT BBK and R1 concepts and so on as well.

[papadooks]

Originally Posted by sukhk527

You should take a look at my build thread, it’ll answer a lot for the questions you’re asking about building a 35i. But on the note of brakes, no the f85 rotors are not a simple plug and play on a 35i two piston rotor , not even a little bit.

Your options include bolting on a 50i front brake setup, doing a Brembo upgrade like I did from dentprotony@gmail.com or the MPBBK from BMW. A few other off the shelf options like Brembo GT BBK and R1 concepts and so on as well.

Thank you. I actually read your whole thread a couple of weeks ago. You ultimately went all the way and upgraded the turbo too right? I just recently found a great deal on eBay for a Wagner evo3 kit with charge pipes, so I ordered that. Gonna pick up an ER catless DP soon and get it all added in. Still on the fence between doing the dentprotony upgrade or wheels first. I guess safety suggests I should do the brakes first. But I’m still on stock 19s with pirelli runflats

[///d]

Originally Posted by papadooks

I guess safety suggests I should do the brakes first. But I’m still on stock 19s with pirelli runflats

What about the stock brakes makes you feel they are going to be unsafe?

Theres 2 reasons to upgrade your brakes;

1) aesthetics

or

2) you're going to run it on the track

Yes you can get better feel from upgraded brakes, but when it comes to safety your stockers are more than enough.

[sukhk527]

Originally Posted by papadooks

Thank you. I actually read your whole thread a couple of weeks ago. You ultimately went all the way and upgraded the turbo too right? I just recently found a great deal on eBay for a Wagner evo3 kit with charge pipes, so I ordered that. Gonna pick up an ER catless DP soon and get it all added in. Still on the fence between doing the dentprotony upgrade or wheels first. I guess safety suggests I should do the brakes first. But I’m still on stock 19s with pirelli runflats

Awesome, hopefully the info was helpful.

Tony’s front brakes will clear 19’s with a spacer, same for the MPBK. I ran spacers on my stock style 449’s for a while, worked out great. The reason I did Tony’s kit was because once I started chasing times, I realized this thing was massively under braked.

And yes, upgraded turbo, full fuel system including high pressure fuel pump, low pressure fuel pump, and injectors have all been upgraded too. Let me know if you have questions, I’ve been through it and then some lol.

[papadooks]

Originally Posted by ///d

What about the stock brakes makes you feel they are going to be unsafe?

Theres 2 reasons to upgrade your brakes;

1) aesthetics

or

2) you're going to run it on the track

Yes you can get better feel from upgraded brakes, but when it comes to safety your stockers are more than enough.

Thanks, man. Appreciate the feedback. The aesthetics are certainly a big part of it, but I was more so worried that the stock brakes would just be inadequate if I manage to get the car pushing north of 400hp, which I realize I’m still a ways from. So I’m happy to hear the stock brakes are adequate. Maybe I’ll do wheels first the and get some nice looking black 21s (I’m in a white m-sport) to replace the stock silver 19s

[papadooks]

Originally Posted by sukhk527

Awesome, hopefully the info was helpful.

Tony’s front brakes will clear 19’s with a spacer, same for the MPBK. I ran spacers on my stock style 449’s for a while, worked out great. The reason I did Tony’s kit was because once I started chasing times, I realized this thing was massively under braked.

And yes, upgraded turbo, full fuel system including high pressure fuel pump, low pressure fuel pump, and injectors have all been upgraded too. Let me know if you have questions, I’ve been through it and then some lol.

Ahhhh yes. I remember your build better now. You even went through two different aftermarket HPFPs, right? How’s the car doing these days? Still happy with the choice of turbo (mosselman, right)?

Coilovers, hpfp, and turbo upgrade are on my longer term to do list

[sukhk527]

Originally Posted by papadooks

Ahhhh yes. I remember your build better now. You even went through two different aftermarket HPFPs, right? How’s the car doing these days? Still happy with the choice of turbo (mosselman, right)?

Coilovers, hpfp, and turbo upgrade are on my longer term to do list

Very happy with the turbo, it’s been on for almost a year and held up great. And regarding the hpfp, yep. Started with a Dorch Stage 1 when we found my stock one failing prematurely on stock turbo then went to a Nostrum Stage 2 with the Mosselman to run full E85. Zero complaints on this setup.

[papadooks]

Originally Posted by sukhk527

Very happy with the turbo, it’s been on for almost a year and held up great. And regarding the hpfp, yep. Started with a Dorch Stage 1 when we found my stock one failing prematurely on stock turbo then went to a Nostrum Stage 2 with the Mosselman to run full E85. Zero complaints on this setup.

Is the HPFP upgrade necessary if you upgrade your turbo, or only if you want to upgrade the turbo and/or run E30+?

[sukhk527]

Originally Posted by papadooks

Is the HPFP upgrade necessary if you upgrade your turbo, or only if you want to upgrade the turbo and/or run E30+?

Only really needed if you plan on running ethanol. Although even on pump 93 you’ll be able to add 1-2psi more boost because you’ll have more fuel to throw at it.

[papadooks]

Originally Posted by sukhk527

Only really needed if you plan on running ethanol. Although even on pump 93 you’ll be able to add 1-2psi more boost because you’ll have more fuel to throw at it.

That makes sense $/psi ratio is real high though haha.

Also, turns out that great intercooler deal I found was Chinese knockoff garbage haha. Back to the drawing board.

[sukhk527]

Originally Posted by papadooks

That makes sense $/psi ratio is real high though haha.

Also, turns out that great intercooler deal I found was Chinese knockoff garbage haha. Back to the drawing board.

I’ve honestly had a great experience with my VRSF one, and even some tuners who have looked at my data logs have been impressed with its capabilities for what it is. A few of us have been running it for some time.

My recommendation for the connections to the intercooler with upgraded charge pipes would be a heavy duty vanjen clamp on each side. Reduces risk of them popping off under high boost.

[///d]

Originally Posted by papadooks

I was more so worried that the stock brakes would just be inadequate if I manage to get the car pushing north of 400hp, which I realize I’m still a ways from.

HP has nothing to do with brakes, but weight does. Brakes are designed to be able to stop "x" amount of weight within "y" distance from "z" speed. More HP just means you can get to speed faster (and maybe go even faster yet).

Where performance brakes come into play is when you're trying to scrub a lot of speed in the shortest amount of distance multiple times while maintaining consistent bite and resisting brake fade, like while on the race track. Performance brakes will have a more consistent feel and resist heat better, which means less likely to get brake fade from hard or repeated hard braking. But the stopping power (weight they are rated to stop) is still based on the vehicle because too much braking power (brakes for a heavy vehicle used on a light vehicle ) is just as bad as not enough (brakes for a light vehicle use on a heavy vehicle). So, M performance brakes are still rated to stop the same amount of weight in the same amount of distance as your stock brakes, they just better resist heat/fade and have a better, more consistent feel.

Long story short, your stock brakes are plenty adequate on the street even with higher horsepower (unless you're driving at high speeds like an asshat, in which case it's more likely some other aspect of the vehicle (or driver) that will cause issues far before the brakes will.)

I'd put more thought into suspension/chassis and proper wheels/tires before worrying about brakes. Those will have much more impact on how the vehicle performs with higher power.