Freddie_1016

Hey guys new to the forum here. Long time BMW M(multiple S63 platform cars) guy just getting into the AMG scene. Recently purchased a 2016 GTS. Noticed that the car had Renntech BOVs on it but everything else seemed stock. Car drives great on test drives. Was informed after purchase that the car has stage 2 tune on it. This is kind of confusing because the car has stock DP on it. I did some research(spoke to the tuner shop who confirmed VIN was tuned at their shop) and confirmed that it was indeed tuned stage 2 catless. The car feels sluggish on the top end though so I took it to another reputable tuner who works on TONS of these cars and did great work on my M6s in the past. We did a couple of pulls on the street and confirmed it’s more sluggish than it should be on a stage 2. We find that the wastegate is stuck at 50%. Thought maybe there’s an exhaust valve stuck causing boost reduction. No codes present. For anything. Then we start looking at the timing table and discover we have a problem. the car is at -1 to 1.5 degrees of timing at anything over 5k rpm. My guy says that should be much higher(5-7 degrees depending on the car. Some up to 9) My question is this: is the ecm possibly pulling timing due to the car not having downpipes when the tune is for a catless setup? Is there anything else that could be causing retardation at high rpm other than an insufficient tune file. Both tuners I’m referencing at very well known and reputable shops.

UCIMBZ

Hi and welcome. The stock pipes on these cars are pretty much wide open all the way. Having the cats shouldn't effect anything but the noise level. And valves are way up high and having DPs doesn't effect their function. I'd focus on the software. Although it is possible that the seller put the original pipes back on so he can pass the car.

Freddie_1016

So this raises another question. I’ve heard mixed reviews on DP for these cars. On my M platforms they are almost a must. On this car I hear you HAVE to have them for anything stage 2 and higher. Or you only need to do sec cat delete. Or they need the back pressure from the first cat. I’m kind of lost there as to what I should do. I did speak to the previous owner and he said that the car never had downpipes because he didn’t want the exhaust smell so he just had a really hot tune created that could run on factory DP. Maybe that’s the issue? Maybe they pulled timing in the map to reduce egt to save the cats and turbos? Thoughts?

Runs 10s

I know on my 2020 GTC whenever you go above a “stage one “type tune, and in many cases advised even for that, they also recommend a modified transmission controller. I honestly have no idea if that can affect it but it’s possible that it may be having some effect.

I know on my 2020 it is impossible to turn the traction control entirely off, except in the “Dyno” mode that my AMG specialist at my Mercedes dealer showed me how to enter. As usual, it’s a “secret “setting that you have to go to that is even beyond the double tap double off traction control button strokes. Unfortunately, in Dyno mode, if you have your foot on the brake, as my application would be in my drag racing start line protocol, you can only rev the engine to about 1200 RPM and the ability to pre-rev it up to 5500 RPM, as you can do in some of the other settings, is prevented.

Of course when you think about it if the car is going to be on the Dyno,, someone would not have their foot on the brake in which case it does allow it to be revved all the way to the electronic ignition cut off. However, you will also lose some of the functions of the antiskid brakes although the main function still works, The dash shows the electronic stability control function quote may not be available” the traction control does go off (Although I think, still not completely), and you also lose the rear steering function on the GTC. Obviously, these will all be preferred if you have the car on the dyno , so they at least seem logical.

I honestly believe the reason all this occurs is for protecting the transmission as even the owners manual mentions about the transmission overheat warning message may come on after several brisk runs of any type In any performance activity. I have yet to have this warning come on, but of course my car in my drag racing scenario normally has time to cool down between individual runs, although I have done a couple back to backs with no problem noted. I’ve also never had this problem on any track days at Sebring or Daytona. I’ve talked to a previous owner of a 18 GTS, and he said on his car he was able to turn the traction control off enough to be able to do good burnout “driver controlled “ decent 60 foot times. This appears to be the sole limiting factor on 60 foot times (THE best measuring stick of you start for you not drag racers) , it does keep them very consistent no matter what setting I do leave the line. I might add that the only reason I included that comment is because I was chastised by some members when I did a similar post who insisted I was misquoting and that I meant “0 to 60 times” as they were very obviously not familiar with drag racing. I have utilized every combination shown either in the owners manual or on this message board as well as the AMG tech at my Mercedes dealer, who is also a drag racer and an AMG car user. He essentially told me that AMG has put severe software programming in the engine computer that for as far as any “racing“ is involved, it most adversely affects your ability to turn off all of the limiting or “safety“ features of the last update of the 2020 to 22s. Of course, completely turning off the traction control is available on this last series of Rs, Blacks, and Professional models So while my car will probably last a lot more miles than I’ll ever have it, in unmodified form it’ll probably never be able to get into the mid tens.

I guess one “consequential benefit” of this is that I won’t have to use drag radials, even though I wish I had a clear and present need for them obviously.

I hope you’re able to resolve your problem and find out it’s because, as we all know, the real strength of these cars is mid range when the turbos get spinning.

UCIMBZ

On these engines the back pressure is not a factor.

Freddie_1016

So I should be able to run a proper Stage 2 map without installing catless downpipes? What if I swap turbos? I want to go with Pure 900 upgrades. If I go that route can I still run factory DP or will I have to go catless at that point

UCIMBZ

Most (almost all) tuners advise that you get the most benefit of a "Stage Two" with DPs. Having said that not having DPs shouldn't cause a reverse effect. With new turbos you gotta follow the manf's recommendation on DPs. What I know about the exhaust system on these cars that they are very little to none restrictive.