Akrapovic exhuast + APR DP + S2 Flash

[SITH7]

So I recently had the infamous Akrapovic titanium exhaust installed which forced a modification to the APR downpipe for fitment...Tell me I'm crazy and my car didn't just get slower!?

Listen, I get it. The back-pressure is now gone which will feel like a loss of torque but I legit feel like the car is more sluggish. I asked my local APR guys if there was a modification to the stage-2 tune for exhaust or even magically this specific one - nothing. Help me out here guys, I really tried resisting posting this but I just got walked by an M5 on a roll that I would have normally annihilated.

I was scratching my head after and as I took the off ramp and caught a couple of red lights to analyze the responsiveness of the car, it just feels flat out...flat.

Not sure if my signature is up to date but:

16, S7. APR S2, Akrapovic, APR DP, Autotech Hi-Flow Fuel pumps, 100 octane map, roc-euro intake, 034 mounts, sways, upgraded plugs etc. HRE p104.

Thanks in advance!

[R3.]

That stinks ! Hopefully it's just your butt Dyno.


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[pez81]

That stinks ! Hopefully it's just your butt Dyno.


Sent from my iPhone using Audizine (http://r.tapatalk.com/byo?rid=87676)Stock M5? Tuned he would walk you but stock not likely. Have you dyno'd your car?

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[sciblades]

Our cars are terrible from a roll, it has to do with the gearing. Also all M vehicles are amazing from a roll.

Take your car to the drag strip and run it see what times you get.

Also autotech fuel pumps might be failing any check engine lights?

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[Ze_Nardo6]

Why did you upgrade the fuel pumps? It's unnecessary with these cars and may be the issue here

[IowaRS7]

Have you double checked which tune is active?

Back pressure has little to no impact on a turbo car. The exhaust is a source of restriction in a turbo car as the exhaust is actively being forced out of the turbo. General goal is to open up the exhaust as much as possible to allow the turbos to obtain maximum efficiency. Changing the restriction of the exhaust can change the boost profile some, can impact EGTs and impact A/F ratio. If you had a restrictive stock exhaust, your ECU had likely adjusted fuel and timing accordingly. Making a change to the exhaust would result in the ECU needing to readjust. You are also likely pushing your stock cooling system to some degree. Check to validate which tune is active, allow some time for the ECU to readjust, then if things still do not feel good, log some data to see if you are hitting proper boost levels, watch temp levels and EGT if possible.

[SITH7]

APR S2 100 map is active.

I added the fuel pumps as I run E85 without issues (lets debate this in another thread lol) - however, I'm open to relative comments about performance.

Cooling, probably is maxed. At the time, oil temp was 221 - its hot here in S. Florida, even at 11pm :/

I've been looking at the AMS cooling system but wasn't sure if it was worth the adjustment?

The M looked stock with maybe upgraded exhaust. Our cars do fall flat on a roll as the system won't allow for brake boosting (it shuts the car down).

Butt dyno, says slow lol. It seemed to leap forward previously.

Last dyno was prior to exhaust but all else and TQ was 605ish to the wheels and power 580's to the wheels. I need to run it again.

Modding the downpipe to fit doesn't affect performance? It has a very clean, straight journey to the back of the car. So flow is def not hindered.

[Ze_Nardo6]

APR S2 100 map is active.

I added the fuel pumps as I run E85 without issues (lets debate this in another thread lol) - however, I'm open to relative comments about performance.

Cooling, probably is maxed. At the time, oil temp was 221 - its hot here in S. Florida, even at 11pm :/

I've been looking at the AMS cooling system but wasn't sure if it was worth the adjustment?

The M looked stock with maybe upgraded exhaust. Our cars do fall flat on a roll as the system won't allow for brake boosting (it shuts the car down).

Butt dyno, says slow lol. It seemed to leap forward previously.

Last dyno was prior to exhaust but all else and TQ was 605ish to the wheels and power 580's to the wheels. I need to run it again.

Modding the downpipe to fit doesn't affect performance? It has a very clean, straight journey to the back of the car. So flow is def not hindered.

If you're running e85, that makes sense. Would love to discuss in another thread. I'm a huge fan of the corn gas.

Iowa is certainly right regarding your cooling. I know it's hot as hell where you are (just like Houston where I am) and the stock cooling in our cars is sh*t, for lack of a better description. I threw my car on the dyno when it was only stage 1 and 93F outside and it was losing power on the top end from heatsoak (evidenced by other pulls on cooler days, same dyno). Cooling is an absolute must for the S6/7 cars if in a southern climate and stage 2

I'm stage 2 now and the car gets one pull before it loses tremendous power. Cooling is my next move, I'm going AMS

[cobrario]

Back pressure has little to no impact on a turbo car. The exhaust is a source of restriction in a turbo car as the exhaust is actively being forced out of the turbo. General goal is to open up the exhaust as much as possible to allow the turbos to obtain maximum efficiency. Changing the restriction of the exhaust can change the boost profile some, can impact EGTs and impact A/F ratio. If you had a restrictive stock exhaust, your ECU had likely adjusted fuel and timing accordingly. Making a change to the exhaust would result in the ECU needing to readjust. You are also likely pushing your stock cooling system to some degree. Check to validate which tune is active, allow some time for the ECU to readjust, then if things still do not feel good, log some data to see if you are hitting proper boost levels, watch temp levels and EGT if possible.

I just can't agree with this statement- exhaust science is way more complicated than to just make a blanket statement like that. I found a great article that goes over the broad strokes of exhaust theory but putting on bigger pipes is certainly not the generic answer to making more power in an engine like ours and to say it may not cause drivability issues I don't feel is correct. I'm not saying the Ak is causing his issue, I just don't agree with the core statement you made. Sorry if I sound like a jerk- here is the link I found, some good info there [:D]

https://forums.mightycarmods.com/forum/technical/tech-talk/3416-backpressure-the-myth-and-why-it-s-wrong

[IowaRS7]

I just can't agree with this statement- exhaust science is way more complicated than to just make a blanket statement like that. I found a great article that goes over the broad strokes of exhaust theory but putting on bigger pipes is certainly not the generic answer to making more power in an engine like ours and to say it may not cause drivability issues I don't feel is correct. I'm not saying the Ak is causing his issue, I just don't agree with the core statement you made. Sorry if I sound like a jerk- here is the link I found, some good info there [:D]

https://forums.mightycarmods.com/forum/technical/tech-talk/3416-backpressure-the-myth-and-why-it-s-wrong

Did you read the information you linked? It agreed with my statement, on a turbo car the exhaust tuning is just not the same as on a naturally aspirated car. Completely different beasts.

[SITH7]

And just to make sure we're clear -- Not faults, no codes, no CEL's.

[IowaRS7]

If the exhaust has allowed the turbos to be more efficient, I would first monitor to see if your fueling system is able to meet the demands, especially given some modifications to the system. Is the tune specifically setup for E85? I thought E85, while it can make some serious power, requires a fair amount of additional fueling.

[cobrario]

Did you read the information you linked? It agreed with my statement, on a turbo car the exhaust tuning is just not the same as on a naturally aspirated car. Completely different beasts.

Yup- just saying that I disagree that backpressure has no bearing on a turbo car, that's just not possible. But we can agree to disagree[cool]

[IowaRS7]

Yup- just saying that I disagree that backpressure has no bearing on a turbo car, that's just not possible. But we can agree to disagree[cool]

Remember the exhaust on a turbo car is not directly hooked up to headers and the cylinder head like a NA car, the exhaust is hooked up to the turbo. The turbo itself regulates the exhaust flow. The turbo outlet is important, the rest of the exhaust is more for sound control and emissions regulations. In Iowa we have no emissions regulations, so I could literally dump the exhaust straight to the ground wide open and be legal [:)] but it would be loud as hell and I wouldn't do that.

Like the intake and other aspects of tuning the motor, the exhaust can impact how the engine performs if it is restrictive. To me it sounds like the addition of the AK exhaust may have allowed the turbos to flow more volume and may have challenged another variable such as fueling or cooling, which could result in those systems needing tweaked now to achieve desired results.

OP, you noted modification of the DPs, do you still have the CATs installed or did you remove them? Just wondering if there was a major restriction point removed in the exhaust as typically catbacks on turbo cars impact weight and exhaust note moreso than actual exhaust flow capacity.

[XLR8 Craig]

The exhaust addition has not cause any adverse effects on the way the car makes its power. It is heat related or fuel related. I am sure the heat in Florida is not helping, but B8 S4 guys were experiencing similar with Ethanol mixtures and the race gas file with AT fuel pumps.

I recommend getting a flex fuel sensor hooked up so you cna control fuel quality and ethanol rating to verify you're always runnning what you think you're running.

[SITH7]

Aside from jacking the car up, Im pretty sure the APR DP, relocates the CAT closer to front, however the modification, removes the majority of the DP in favor of the AK exhaust and put the CAT in its original spot (I may have that reversed, and going off memory). It was a concern and might possibly affect the tune, but figured a CEL would be caused if there was an issue with ratios?

I agree the combo would need some adjusting tuning, which would force a custom dyno tune vs APR's - unless they want to come play with it, but seems they have their hands full with RS7-P tune issues.

Prior to the exhaust install, the fuel ratios were spot on and octane was stable at 100-103 with no timing pulls. Added note, I am running full E85 no mix except for the additive of ACES IV, which I always use liberally as an extra ounce cant hurt.

Butt dyno wise, the car feels sluggish compared to what it used to. Feels like a long wind up vs the eager machine it was prior. Heat could be an issue, I'm above my knowledge base as this level to be honest and of course have sought the wisdom of you fellow brothers and sisters.

[Ze_Nardo6]

I don't think the APR cats are moved up close to stock position with your modification of the exhaust. Reason I assume this is because the cat location of the APR pipes is much further removed from the engine bay as opposed to stock. They may have moved them slightly closer to the engine, but couldn't have been much.

My 1000 mile diagnosis is your cooling, and perhaps something to do with running full e85. I believe you're the only person successfully doing so, which obviously doesn't mean its the issue but introduces more unknowns. Do you have a vagcom to record temps and if boost/timing is being pulled?

[SITH7]

I do have a vagcom and was previously running stats through the APR module. Ill give that a shot.

Aside from cooling, do you suggest going back to 93 fully and moving the tune down to 93 as well? I see your point, but whats odd is how is was so much more active before, make sense? Feel free to call me crazy! lol

[Ze_Nardo6]

I do have a vagcom and was previously running stats through the APR module. Ill give that a shot.

Aside from cooling, do you suggest going back to 93 fully and moving the tune down to 93 as well? I see your point, but whats odd is how is was so much more active before, make sense? Feel free to call me crazy! lol

That would be a good starting point to rule out the e85 as any part of the problem. I would switch to 93 map and run through a couple full tanks to see how the car behaves. Remember though, the 93 file obviously generates less power than the e85 and its respective race file.

[SITH7]

yes but its not crazy.10lbs of AWT and 22 AWP - in theory (according to APR site with basic S2 setup).

Cooling is on the way, and always wanted to do bigger turbos but my fear the tranny would snap. Im just butt hurt over losing so bad to this plain M lol.

[NardoRS7]

Who tuned you for E85 and what additional hardware did you need for it?

[IowaRS7]

Typically, when you open up the intake and/or exhaust, without changing anything else, you loose some low end torque but gain on the big end, all depends on tuning though. Its possible you are feeling a delay in boost and some low end torque loss due to the changes, and depending on where you were are at with RPMs on a roll race you could be seeing a negative impact. Might need to keep rpms a little higher going into roll races now. Still best to log some data to see if anything is going on as heating and fueling issues would simply make that worse.

APR DPs move the CAT from the engine bay to much closer to the catback area under the car. I would be interested to know what was actually modified to fit the Akra in.

[MadAboutCars]

Make sure you reset your 01 Engine faults even if none are showing. This will clear the engine adaptations and allow the car to re-adapt to the new exhaust/fuel etc.

[widebodyfx]

I'm assuming no cuts were made on the Akra which is titanium up to their forward resonators.

The modded APR pipes I had were essentiall stock APR uppers, with the link pipe that mates to mid pipe of the stock exhaust config so it should look something like this.

https://uploads.tapatalk-cdn.com/20170722/44df2f0ff7405a21c7dcc0c0a425af3d.jpghttps://uploads.tapatalk-cdn.com/20170722/ec216c2bfe26474dab055ce19b06a96b.jpghttps://uploads.tapatalk-cdn.com/20170722/83664b99e85731b378ebee18173d25cd.jpg


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[jsmonet]

I just can't agree with this statement- exhaust science is way more complicated than to just make a blanket statement like that. I found a great article that goes over the broad strokes of exhaust theory but putting on bigger pipes is certainly not the generic answer to making more power in an engine like ours and to say it may not cause drivability issues I don't feel is correct. I'm not saying the Ak is causing his issue, I just don't agree with the core statement you made. Sorry if I sound like a jerk- here is the link I found, some good info there [:D]

https://forums.mightycarmods.com/forum/technical/tech-talk/3416-backpressure-the-myth-and-why-it-s-wrong

backpressure definitely has bearing on turbo cars.

removing it entirely makes the motor happy, allows it to run freely, spool faster--unfettered by backpressure. When you have turbos, your one primary goal is to let it breathe. The freer it flow, the earlier it spools--obviously within mechanical limits.

This is why I couldn't really wrap my head around why the akra exhaust would have a mechanical, negative influence on the car. It doesn't make much sense unless something increased backpressure or the condition is being observed before the car warms up. Moving the cats downstream, removing them entirely, means the car heats up a lot slower. Since it seems like all these issues are being controlled for, it's a mystery, but not one solved by looking at the exhaust. That's a red herring

[RedS-line]

better flowing exhaust means you trade a few torque down low for a few hp up top, happened to me in my a4, hated it since the 2.0t has a lousy top end anyway.

[jsmonet]

That motor must have sucked all kinds of ass because I did that with my wrx and it gained everywhere, no problem. Then again, that was turboback + tune, just like what I ran on my sti with the same positive results everywhere.

[lapsandwich]

That motor must have sucked all kinds of ass because I did that with my wrx and it gained everywhere, no problem. Then again, that was turboback + tune, just like what I ran on my sti with the same positive results everywhere.

Your opening sentence made me laugh out loud. All kinds of ass indeed. In regards too the original post, No turbocharged engine is going to suffer from bigger exhaust. The turbine flange could be welded to one of the stacks off the titanic. It's still not going to lose performance. I gained like 40 whp from 3" downpipes alone, on a Completely stock tune. I'm going to go ahead a rule that issue out for you. I'd start looking at your fuel mixtures/ e85.

[ryanlada]

This is my understanding as well. The turbo exhaust housing is waaayyy more restrictive than any n/a car exhaust manifold. Only concern I'm aware of is if the exhaust restriction somehow plays a part in boost control. As long as the ECU can manage the boost level on its own you can make the exhaust as big as you like.

[RSLRS71]

Remember the exhaust on a turbo car is not directly hooked up to headers and the cylinder head like a NA car, the exhaust is hooked up to the turbo. The turbo itself regulates the exhaust flow. The turbo outlet is important, the rest of the exhaust is more for sound control and emissions regulations. In Iowa we have no emissions regulations, so I could literally dump the exhaust straight to the ground wide open and be legal [:)] but it would be loud as hell and I wouldn't do that.

Like the intake and other aspects of tuning the motor, the exhaust can impact how the engine performs if it is restrictive. To me it sounds like the addition of the AK exhaust may have allowed the turbos to flow more volume and may have challenged another variable such as fueling or cooling, which could result in those systems needing tweaked now to achieve desired results.

OP, you noted modification of the DPs, do you still have the CATs installed or did you remove them? Just wondering if there was a major restriction point removed in the exhaust as typically catbacks on turbo cars impact weight and exhaust note moreso than actual exhaust flow capacity.

Im with you on this one...