ARMA Speed 130i exhaust manifold fitted to 125i

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///MBan
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ARMA Speed 130i exhaust manifold fitted to 125i

Post by ///MBan » Sat Jul 18, 2015 4:46 am

Part 1: The manifolds

A while ago I was reading about the great results N52B30 owners were achieving with aftermarket exhaust manifolds, notably Super Sprint and Active Autowerke on North American 128is.

So, an aftermarket exhaust manifold and a tune afterward sounded pretty good to me. The problem was, my car is an Australian-delivered right hand drive model which means the AA and SS manifolds won’t fit due to the steering linkages being in the way.

Therefore, I had to look for other options. I tried to find a shop that was willing to build a custom set of manifolds but several I contacted didn’t follow through with a price and one which ticked the boxes for quality and experience had a very high price ($4,000 +). Therefore, an off-the-shelf option was my preference.

After some good advice from 1Addicts 128i owners, I looked at 130i exhaust manifolds as 125i and 130i apparently have the same factory manifolds. With that information in hand, my searching turned up the following: Schmiedmann; Mapleridge (E90 forum member, not an actual shop); ARMA Speed; and Racelook.
In the end I chose the ARMA manifolds because the quality looked good and they apparently fitted well (according to a babyBMW.net member). With a 20% discount they came to $1,440 US.

I’m no expert but my observations once the manifolds arrived were:
- Nice welds.
- Some tight bends on the front manifold.
- Primary tube diameter = 37 mm (1 and a 1/2 inches)
- Post collector tube diameter = 61 mm (2 and 2/5 inches), reducing to 51 mm (2 inches) at the flange.
- What I thought were ‘expansion chambers’ actually have a honeycomb lining around the inside which I think makes that unlikely?
- Mounting points for the post-cat oxygen sensors have extensions on the inside with what I think is a small piece of catalyst mesh at the end. I believe this is to help trick the sensors into seeing a catalytic converter and preventing a Check Engine Light (CEL).
- Come with all gaskets, bolts and nuts.
- Also come with a little electronic module that plugs into the OBD2 port to cancel a CEL (which I didn’t install).

A few pictures are included below.

Image

Image

Image


Part 2: Installation

The Australian 125i (and maybe European cars?) don’t have secondary cats – see the diagram below:

Image

The exhaust shop recommended that if my purpose was to keep the car legal, I should use two cats in the new system so it is a like-for-like swap in removing the cats integral to the exhaust manifolds. The end configuration was:
Twin 2 inch pipes from the exhaust manifold to two Magnaflow cats (200 cell), merging into a single 2.5 inch pipe then through a Magnaflow 4 inch resonator and joining to the factory piping after that. Essentially I replaced everything from the exhaust manifolds to the stock resonator (inclusive).

The exhaust manifolds were sent for ceramic coating and then the whole lot was put together. The exhaust shop said the manifolds fitted perfectly, giving a second tick to the ARMA header quality and confirming 130i / 125i cross-compatibility.

Sound-wise, the new system isn’t too much louder with a nice burble and slightly gravely sound through the mid-range and a pop on the overrun between 2,500 and 3,500 RPM building to a metallic buzz above that. No drone and no overly obvious bark either. I can really hear the point that the exhaust valve opens now. It’s like a whoosh and sudden change in pitch.

After a couple of hundred km a CEL has come up on the instrument panel. I don’t like the idea of installing the ARMA electronic module when I intend to get a tune which can cancel the CEL anyway. Still tossing up what to do on that front but if I can find a good way to mount the module without putting holes in the interior, I might do it.

Part 3: Results

I wasn’t expecting really big power gains because: 1) the pipework on the front manifold is a bit convoluted (in comparison to SS and AA) to get around the steering components; and 2) my system hasn’t reduced the total number of cats, unlike most of the North American guys I’ve seen who effectively go from 4 cats to 2 when installing the SS and AA manifolds. Even still, I was pretty disappointed with the results.

Before (red line) and after (blue line) as measured on a DynoDynamics in Shootout mode.

Image


A 3% increase in peak power is small enough to put down to day-to-day dyno variation. However, the after header AFR drops slightly later at the top of the rev range – right where the small hp increase is – so I suspect there is a very small gain. You’ll notice the AFR drops sharply just above 5,700 RPM. Does anyone know why the AFR would drop like that? In TheAxiom’s N52B30 dyno thread on the E90 forum I saw a couple of other cars that had the same funny AFR curve but I didn’t see any explanation.

All in all, a very disappointing result. While I like the exhaust note, I could have achieved the same thing by just replacing the rear muffler section and saved myself a bunch of cash.

Has anyone seen an independent before and after dyno of the AFE headers? In effect, these provide a similar setup to mine. AFE claim an ‘astounding’ 16hp but quoting a hp figure alone is almost meaningless. Of course, the AFE headers aren’t compatible with RHD cars so they’re not actually an option but the comparison would be useful.

I’d also be interested to see what gains the SS or AA manifolds give when high flow cats are added back in to replace the factory cats built into the headers (i.e. for some North American guys, still ending up with 4 cats in total). In theory, they should still give a greater gain than what I saw with the ‘shorty’ ARMA headers but real life and theory don’t always agree.


Cheers
Michael

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Re: ARMA Speed 130i exhaust manifold fitted to 125i

Post by Producethis » Sat Jul 18, 2015 6:45 am

Sounds like a disappointing process :( ... bolt a supercharger on ;) that exhaust might come into its own with that on and probably satisfy your need for power

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Re: ARMA Speed 130i exhaust manifold fitted to 125i

Post by THETYRANT » Sat Jul 18, 2015 6:51 am

Interesting reading, is that dyno run after a remap?

Can you post up afr graph ? Ignore this I just looked at graph properly and seen other trace is afr :) needs mapping to lean that out bit :D

Ian
Last edited by THETYRANT on Sat Jul 18, 2015 8:23 am, edited 1 time in total.
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Re: ARMA Speed 130i exhaust manifold fitted to 125i

Post by rob180bhp » Sat Jul 18, 2015 7:34 am

Unfortunately gains from a manifold change is always going to be minor, unless the old unit was very restrictive

Do it because you want to but no point search for power from N/A engine it just isnt worth thd gains



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Re: RE: Re: ARMA Speed 130i exhaust manifold fitted to 125i

Post by Producethis » Sat Jul 18, 2015 7:44 am

rob180bhp wrote:Unfortunately gains from a manifold change is always going to be minor, unless the old unit was very restrictive

Do it because you want to but no point search for power from N/A engine it just isnt worth thd gains



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I'd be happy with nearly 400bhp from an n/a car

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Re: RE: Re: RE: Re: ARMA Speed 130i exhaust manifold fitted to 125i

Post by rob180bhp » Sat Jul 18, 2015 7:51 am

Producethis wrote:
rob180bhp wrote:Unfortunately gains from a manifold change is always going to be minor, unless the old unit was very restrictive

Do it because you want to but no point search for power from N/A engine it just isnt worth thd gains



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I'd be happy with nearly 400bhp from an n/a car

Ahem - http://www.babybmw.net/viewtopic.php?t=75502" onclick="window.open(this.href);return false;

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But its not naturally aspirated lol



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Re: ARMA Speed 130i exhaust manifold fitted to 125i

Post by Producethis » Sat Jul 18, 2015 7:52 am

It was lol, I'm sure the 130 map for the 125 has more the 180 bhp anyway?

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Re: ARMA Speed 130i exhaust manifold fitted to 125i

Post by rob180bhp » Sat Jul 18, 2015 7:55 am

No he hit 390 with supercharger kit

No NA 130/125 will ever hit that power with just a map etc its not possible

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Re: ARMA Speed 130i exhaust manifold fitted to 125i

Post by Producethis » Sat Jul 18, 2015 7:56 am

I know that, but doesn't the 130 na run more than 180 bhp? If so why is this 125 not running it?

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Re: ARMA Speed 130i exhaust manifold fitted to 125i

Post by marco_polo » Sat Jul 18, 2015 8:10 am

It does sound like it's time for a 130i remap, assuming you have the DISA inlet? Have you spoken to Evolve, who can supply remote remap kits?


The AFR drops to help prevent detonation, on mine it drops around 4,000rev/min. The extra fuel is used a bit like an in-cylinder coolant, it's only 14.7:1 in the first place to keep the hippies / catalytic converters happy.
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Re: ARMA Speed 130i exhaust manifold fitted to 125i

Post by jonwilli » Sat Jul 18, 2015 8:19 am

Sorry to hear that. As said above have you had the car remapped and do the Aussie 125i have the 130i intake manifold? The gains seem really low for an exhaust manifold and map, especially if you're getting the OEM 130i map which should get you 260bhp without the exhaust changes. I am running the ARMA headers and full SS exhaust and I would agree the gains are small but would have thought (from the butt dyno) much more than your dyno shows. I think the SS exhaust also has 200 cell cats but has slightly larger diameter (70mm) main pipework. I will hopefully have a dyno for my car in the current set up in the next four or five weeks. The DMS map (optimistically) quotes 294bhp and I would say the exhaust and manifold has added 5 or 10bhp at the top end. I would hope the dyno shows about 290bhp which I think is about 247 whp. Have you found the car revs more urgently from about 4 to 4.5k revs? I think most of the improvements, other than aural, that I found with the full exhaust have been towards to top end of the revs which I guess is what you'd expect.

Like you I am really happy with the sound my exhaust and manifolds make but as said in my build thread and in the 130i manifold thread I think the manifolds and cats are only really worth upgrading if you are determined to supercharge a 130/125i. This is to give longevity to the cats and stop engine warning lights coming on in the future.
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Re: ARMA Speed 130i exhaust manifold fitted to 125i

Post by rob180bhp » Sat Jul 18, 2015 8:51 am

Im sure the 130 is circa 270bhp?

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Re: ARMA Speed 130i exhaust manifold fitted to 125i

Post by jonwilli » Sat Jul 18, 2015 8:56 am

Just to manage expectations this is the Supersprint dyno for standard 130i versus a 130i with full Supersprint exhaust including LHD headers (no map) from their website. Supersprint only claim a 6bhp increase from stock, but they are known to be conservative. I have read a lot the 1Addict posts on exhaust manifolds and I think the large gains that members quote are difficult to just attribute to the headers. I hope a remap and 130i intake manifold (if you haven't got one) gets the gains and result you are after....

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Re: ARMA Speed 130i exhaust manifold fitted to 125i

Post by ///MBan » Sat Jul 18, 2015 9:10 am

A couple of points:

1. My car is a 125i (160kW stock) which has the 3-stage intake manifold but is de-tuned; and
2. It hasn't been remapped yet.

A remap is definitely on the cards next but from what I've read, both Active Autowerke (AA) and Evolve have tunes that are optimised for cars with aftermarket headers so I decided to do the headers first. For example, AA claim their headers alone add 15hp (or something) and then their tune will add an extra 9hp even if the car in question has already been tuned with their software. Hopefully that makes sense.

I'm planning on speaking to Evolve next year... Supposed to space my modifications out so I have a self-imposed schedule.

As for a supercharger; that is honestly too much money and power for what I use this car for. I specifically stayed away from forced induction this time 'round and I'm going to stay N/A all the way.

Throttle response does seem sharper and the car seems to rev more eagerly but because neither of these observations can be tested subjectively, I'm little reluctant to make any claims.

Thanks for the dyno jonwilli. I wouldn't mind so much about only gaining 6 hp if I saw gains right across the rev range like the SS chart shows, but my gain is pretty much only above 6,000 rpm.

I think you're right about the big gains others have seen with the SS and AA manifolds - something else is contributing. To me, deleting a pair of cats seems the most likely reason.

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Re: ARMA Speed 130i exhaust manifold fitted to 125i

Post by jonwilli » Sat Jul 18, 2015 3:09 pm

///MBan wrote: I wouldn't mind so much about only gaining 6 hp if I saw gains right across the rev range like the SS chart shows, but my gain is pretty much only above 6,000 rpm.
I think that's pretty normal for an exhaust upgrade on an NA engine. I guess you only see the gains once the exhaust gas volume reaches a flow where the OEM design is a limiting factor. Have a look at the Supersprint E46 M3 dynos, 10bhp for the race exhaust and cats with OEM headers, an extra 9bhp on top with their headers....the power curve only really exceeds the OEM exhaust from 6,000 rpm. The Supersprint M3 set up is €7,000 for 15 to 20bhp and considered one of the best aftermarket exhausts out there.
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