Catless Downpipes

[S800vxr]

I am thinking of fitting a set having had the car mapped however I get conflicting reports regarding them being any good. Some folk are saying I will lose low end response and torque whilst the WWW seems to say different.
What's the general consensus and experience from here guys...?

BTW - 2013/4 F13 M6 in the UK.

[shahin]

Originally Posted by S800vxr

I am thinking of fitting a set having had the car mapped however I get conflicting reports regarding them being any good. Some folk are saying I will lose low end response and torque whilst the WWW seems to say different.
What's the general consensus and experience from here guys...?

BTW - 2013/4 F13 M6 in the UK.

You will feel defiantly the added power and torque.
Along with a lot nice exhaust note.
You will need an ECU tune or you will get check engine light all the time.
And the ECU tune will also give you good added power.
If you don't want any of the headaches, just get the high glow Catted DP, no need for ECU tune.
U will have a little less power than catless and also quieter.

Cheers

[chask]

I have been wondering about this too - how much extra power do you get with cat-less over the race cat DP. Not sure if I will ever do anything like this but the thought of having more power on tap should I ever need it is appealing. Right now I'm leaning towards staying stock (mostly worrying about warranty issues - it's a very expensive engine and drivetrain) but who knows what the future might hold. I kind of lean towards a race CAT to get the freer flow but still retain emissions capability. Since I don't intend to race I'm not sure I need that last extra 'umph' the cat-less would provide. But that's just me. You will definitely get better flow with nothing there.

I think it was M6Beast who had a small amount of CAT material stuck near the after CAT sensor on his DP. He claimed it was like the cat-less DP in performance without generating the CELs; or maybe they went away after a while. M6Beast is the one who makes the MSR intake pipes that are supposed to work so exceptionally well. Anyway, this might be another option if you've got someone willing to work with you on it. M6Beast sure is going fast in his - sub 11 quarters (I think it's 10.7). Mighty quick for a roughly 4500 pound car.

[bigbrian]

If you are simply bolting on catless DPs w/o a tune you are not going to get additional power out of them. The exhaust will sound a lot better but that is about it.

Brian

[chask]

Originally Posted by bigbrian

If you are simply bolting on catless DPs w/o a tune you are not going to get additional power out of them. The exhaust will sound a lot better but that is about it.

Brian

I would not think that the difference in changing DPs would be much (w/ or w/o CAT) without some kind of tune (flash or kit) to boost performance. But I would have thought that the ECU would learn it was freer flowing just a little. Maybe not enough to notice but at least some - couple of hp maybe, and possibly a few more. To see any appreciable difference you'd have to do something to get more air into the engine.

It's getting air into an engine that's tough. Fuel is a liquid and much denser, plus you only need about 1/12th (+/- a bit) as much fuel as you do air (by mass). Getting fuel in is easy in comparison. Then it's getting the burnt stuff out that's the trick. Anything that impedes air going in or coming out is going to cost performance. Everyone around here seems so keen on the exhaust sound. I agree that a good sound is really a nice feature of any exhaust system, but to me it's free flowing that is the key. One that does that well will sound just fine to me.

There's not much you can do to get more air in. You are pretty much limited by the volumetric efficiency of the engine; in other words the mechanical parts on the engine - cam (lift and duration), cam timing (advance/retard off TDC), larger ports and polish and match, intake and exhaust tuning. All of those things are fixed unless you want to get into some engine building, not to mention that they are also already done extremely well on the M6 motor. No, there are only a couple of reasonably viable routes to go. Of the easy ways I can think of, make the air colder is one - water, water/meth, straight meth and/or gasoline injection into the intake system at high boost will help cool things down quite a bit. A bigger and/or more efficient intercooler setup can cool the intake air down too. More boost is another and probably the easiest one of the options - up to a point, you need to watch where you are running on the compressor and turbine maps (don't over drive them or run them in really inefficient areas of operation - too much temperature increase). A bigger turbo can help as well (what you do when you are running them beyond their design capabilities) but generally you are after a lot more air flow and more boost (lots more hp) with this change. This is just trying to gain even more horsepower by pushing a lot more air into the engine at the upper boost and RPM end of things - you need to maintain a sufficient compressor efficiency up there to actually achieve additional air into the engine and/or to keep that air at a decent temperature so that the added boost doesn't cause some self ignition (knock). Sometimes though, if you are not careful about the design and turbo selection (compressor and turbine size and trim, and wg bypass sizing) you can give up a bit of performance and response on the low end with this route. After any of these you really need some kind of a tune to take full advantage of the benefit(s) those mods offer.

What I wonder though is how much does removing the CAT material gain you over having a freer flowing but CATed DP. Let's say you are going to change the DP (maybe other bolt-ons too) and do something for a tune as well. How much does the race CAT DP help and how much more will the CAT-less DP benefit? The CATed DPs are about a grand more than a CAT-less one. That's sure a lot to pay for something that is going to slow you down some but will also not give you any CELs. I am just wondering how much slower.

[S800vxr]

Cheers for the feedback so far. For clarity my cars already mapped to 730hp (dyno' at 728 to be specific) and I'm not really after more power I just feel the HD cats fitted are either restricting spool or causing a restriction which acts as a heat sink when running hard. Emissions and warrentee are not a real concern as I can remove the tune and DPs if needed.

[n0shadowkick]

Hello, I'm curious what mods do you currently have in your m6?

[chask]

Originally Posted by n0shadowkick

Hello, I'm curious what mods do you currently have in your m6?

Me too.

[S800vxr]

Not allot, k&N drop in filters and a serious remap by one of the best companies here in the UK (DMS). I used them due to their rep and the fact one of the main guys has a heavily mapped M5 and a ride in that convinced me.
TBH though dyno results vary and mean not allot. All I know is it's fast and has no limiter speed wise now. My old HSV Holden was SC'ed (heartbeat) with loads more and did about 640hp and the M6 would destroy it totally and I used to think the Holden was fast!

[n0shadowkick]

Very cool. I would say go catless but that's jus me

[michel lane]

Am I reading this right ? Dms can remove the limiter ?

[S800vxr]

DMS can do anything you like TBH. But in answer to your question yes they can remove the limiter. Only blipped mine to 170 so far but it was ripping up to that with no signs of deceleration at all!

[bigbrian]

Any tuner now (via ECU access) can remove the limiter so if DMS isn't in your area you should be able to find someone to remove the limiter.

You are indeed correct in the dyno numbers varying. I asked this question to EuroCharged in Houston, TX. He explained to me it's because of how the dyno machine is setup, what load system is being used, etc, etc. I have not wrapped my head around it all personally so I won't go into detail because I would be blowing smoke. That is why you see some cars fully modded putting down 720whp and other cars (same mods) putting down 640whp on a different dyno. The biggest factor you need to look at is the baseline numbers and the final numbers -- how much of a gain did you car make.

I personally love my catless downpipes. Coupled with the full length Eisenmann Race exhaust I can hear the turbos whining/whistling out the exhaust and it sounds absolutely incredible. One of the biggest compliments on my car is how it sounds. If you are modded out like you are slap them on my man -- you won't regret the sound and the smile it puts on your face!

Brian

[double trouble]

Originally Posted by bigbrian

Any tuner now (via ECU access) can remove the limiter so if DMS isn't in your area you should be able to find someone to remove the limiter.

You are indeed correct in the dyno numbers varying. I asked this question to EuroCharged in Houston, TX. He explained to me it's because of how the dyno machine is setup, what load system is being used, etc, etc. I have not wrapped my head around it all personally so I won't go into detail because I would be blowing smoke. That is why you see some cars fully modded putting down 720whp and other cars (same mods) putting down 640whp on a different dyno. The biggest factor you need to look at is the baseline numbers and the final numbers -- how much of a gain did you car make.

I personally love my catless downpipes. Coupled with the full length Eisenmann Race exhaust I can hear the turbos whining/whistling out the exhaust and it sounds absolutely incredible. One of the biggest compliments on my car is how it sounds. If you are modded out like you are slap them on my man -- you won't regret the sound and the smile it puts on your face!

Brian

Agreed with what Brian says. I personally have the catted version of AMS downpipes, and Eisenmann race exhaust, and it is wicked sounding. If I weren't in a convertible, I would have gone catless. Either way, it sounds KILLER, but the biggest gains will be made via the ECU tuning process, not removal of cats.

Ben

[N.S.A]

Originally Posted by bigbrian

If you are simply bolting on catless DPs w/o a tune you are not going to get additional power out of them. The exhaust will sound a lot better but that is about it.

Brian

How about the catted ams downpipes will that add hp or exhaust sound? Thanks

[bigbrian]

Originally Posted by N.S.A

How about the catted ams downpipes will that add hp or exhaust sound? Thanks

The AMS catted downpipes will add sound but it won't really add any horsepower. When I said "won't really" because you MIGHT get 2-5hp out of it but even that is questionable.

In general high flow (AMS catted) or catless downpipes (straight thru) will allow other modifications to work more efficiently while used in conjunction with the high flow or catless downpipes.

Brian

[BTF13M6]

Originally Posted by double trouble

Agreed with what Brian says. I personally have the catted version of AMS downpipes, and Eisenmann race exhaust, and it is wicked sounding. If I weren't in a convertible, I would have gone catless. Either way, it sounds KILLER, but the biggest gains will be made via the ECU tuning process, not removal of cats.

Ben

Ben,

How much spool sound do you get with the AMS catted DP's?

Ben (too)

[bigbrian]

Originally Posted by N.S.A

Oh I see, good to know man. Thanks for the information man.
Curious to know also, would a catted ams downpipes cause the engine light to go on ?

No, AMS catted DPs will not cause the check engine light to come on.

Brian

[N.S.A]

Originally Posted by bigbrian

No, AMS catted DPs will not cause the check engine light to come on.

Brian

Oh okay perfect THANKS that helps a lot. I just heard one forum member said once his engine light came up with those downpipes

[2007 to 2016 M6 Cab]

How crazy load will just deleting the Cats and putting in super sprint straight pipes be ... Too much for a M6 Cab with roof down?

[bigbrian]

Originally Posted by 2007 to 2016 M6 Cab

How crazy load will just deleting the Cats and putting in super sprint straight pipes be ... Too much for a M6 Cab with roof down?

That would be pretty damn loud! LOL!

Brian

[2007 to 2016 M6 Cab]

You serious or just talkin?
My 2007 M6 cab had the K&N cold air Induction and the eisenmann cat back sport exhaust with the dual oval tips ... Was very nice and respectable for the V10!!!
The 4.4L twin turbo is nice for power ... Exhaust note not so nice ... The turbo's are essentially another muffler.

anyone who had first hand knowledge ... Your opinion Would be nice ... I assume the Arkym exhaust as part of the competition pack is why BMW had done so ... Hate to say it, but my 2015 S63 Amg, and my 2011 S63 Amg had better exhaust note ... Or my 2002 Chevy suburban with borla cat back have a more commanding exhaust note!

If cat delete is like eisenmann race ... Than Arkym it is ...