550whp — do I really need a full exhaust? Or are dps and 335is muffler good enough?
- Thread starter drunkentrader
- Start date
I will go on to mention(I may be repeating myself) that the small AR creates HUGE backpressure on stock frame turbos or cast stock frame turbos. BP kills turbos faster than anything else, period. Even faster than overspinning(ECU catches it to a degree causing limp mode preventing in more overspinning). The small AR is great for spool. Not for top end or high HP as discussed above.
Vendors have basically lied for years saying you can make 700whp on stock frames with nothing to worry about. They did this for marketing reasons and to sell turbos. Now when people go and try and do it you get failures left and right because of VERY high BP because of how damn small the AR is. You end up with a turbo that has extremely dangerous BP and it outputs VERY hot AITs into the induction piping/intercooler. This is why stock frame twins make so much more on E85 vs pump. They need a very high AKI to produce decent numbers. This is also why they spool up faster than a equally sized single turbo because the single turbo does not have a dangerously small AR. It's physics. Same amount of exhaust gases different ARs and wheel sizes. Thus 'they' went and had new castings made with larger ARs to reduce BP but this also reduces spool. It is not possible to have the same size wheels, increase AR, and have identical spool as the smaller AR but the marketing of the turbo manufacturers will tell you different because well, sales.
Now you could install a ST and achieve 1:1 backpressure and on 93 make more whp than stock frame style twins can on E85. You just have a large turbo the will be laggy in comparison to the twins. Now add 100% E85 to that ST and watch it walk twins on the highway all day long. Again it's give or take you can't have your cake and eat it too. Like the video I posted above says: want a great motor for drag racing only that lives at 7-10k only? Just like that GTR in the video mind you. I hope you don't mind the horrible spool because all you want it the most top end possible. This is the opposite of what you would want for a track car or for autoX or even daily driver.
At the end of the day wheel size and AR will mainly determine the max HP and lag/spool the various turbos will produce on the n54.
Glowing white hot:
Those are stock 10Ts. Imagine the same stock frame but with 20Ts pushing 3x the HP as stock through the same SMALL AR.
So how does this all go back to the stock exhaust you might be asking? Well the stock exhaust is not the restriction you should be most focused on. It's the restriction in your turbo(s).
Again, any factual data showing the stock e9x exhaust is a restriction at 550whp would be welcome.
Also feel free to read on regarding this topic here:
www.spoolstreet.com
To end it:
https://www.n54tech.com/forums/showthread.php?t=36154
That is on the 135i, which has a pretty bad exhaust. The 335i e90 that I have has no cats, just stock resonator and muffler. We tested that vs open dp and saw no gains at all with 800whp+
Payam and BMS don't sell exhausts for the n54. They have nothing to gain by lying about this one way or the other. They are also the most reputable vendor this platform has BY FAR. No drama. Just posts results and sells product.
Vendors have basically lied for years saying you can make 700whp on stock frames with nothing to worry about. They did this for marketing reasons and to sell turbos. Now when people go and try and do it you get failures left and right because of VERY high BP because of how damn small the AR is. You end up with a turbo that has extremely dangerous BP and it outputs VERY hot AITs into the induction piping/intercooler. This is why stock frame twins make so much more on E85 vs pump. They need a very high AKI to produce decent numbers. This is also why they spool up faster than a equally sized single turbo because the single turbo does not have a dangerously small AR. It's physics. Same amount of exhaust gases different ARs and wheel sizes. Thus 'they' went and had new castings made with larger ARs to reduce BP but this also reduces spool. It is not possible to have the same size wheels, increase AR, and have identical spool as the smaller AR but the marketing of the turbo manufacturers will tell you different because well, sales.
Now you could install a ST and achieve 1:1 backpressure and on 93 make more whp than stock frame style twins can on E85. You just have a large turbo the will be laggy in comparison to the twins. Now add 100% E85 to that ST and watch it walk twins on the highway all day long. Again it's give or take you can't have your cake and eat it too. Like the video I posted above says: want a great motor for drag racing only that lives at 7-10k only? Just like that GTR in the video mind you. I hope you don't mind the horrible spool because all you want it the most top end possible. This is the opposite of what you would want for a track car or for autoX or even daily driver.
At the end of the day wheel size and AR will mainly determine the max HP and lag/spool the various turbos will produce on the n54.
Glowing white hot:
Those are stock 10Ts. Imagine the same stock frame but with 20Ts pushing 3x the HP as stock through the same SMALL AR.
So how does this all go back to the stock exhaust you might be asking? Well the stock exhaust is not the restriction you should be most focused on. It's the restriction in your turbo(s).
Again, any factual data showing the stock e9x exhaust is a restriction at 550whp would be welcome.
Also feel free to read on regarding this topic here:
Stock exhaust system capacity with upgraded DP's
Hi Guys I have a question I have struggled to find the answer on by searching this forum. How much HP (or exhaust flow) can the stock exhaust system handle with just a 3” catless DP upgrade before the backpressure would cause problems for the turbos or other equipment? The reason for my...
www.spoolstreet.com
To end it:
https://www.n54tech.com/forums/showthread.php?t=36154
| I believe Terry dynoed with his cut out set up and saw a 27 whp gain. |
That is on the 135i, which has a pretty bad exhaust. The 335i e90 that I have has no cats, just stock resonator and muffler. We tested that vs open dp and saw no gains at all with 800whp+
Payam and BMS don't sell exhausts for the n54. They have nothing to gain by lying about this one way or the other. They are also the most reputable vendor this platform has BY FAR. No drama. Just posts results and sells product.
Are there any turbos besides BW EFR that have gamma titanium turbine wheels? That seem to me to the way to have your cake and eat it too. Bigger turbine and housing for more top end power, but with half the density of inconel you don't have the huge gain in rotating mass with the bigger wheel (compared to a standard inconel turbine) so still have a responsive turbo.
That saying always got to me “can’t have your cake an eat it too” why the ffffff not lol
For reference here is my exhaust…since it’s down while I make a career out of doing this dang clutch an turbo swap…hindsight I should of staggered the resonators it would of fit cleaner…an makes no comments on my globular welding skills probably 20 years since I welded.
For reference here is my exhaust…since it’s down while I make a career out of doing this dang clutch an turbo swap…hindsight I should of staggered the resonators it would of fit cleaner…an makes no comments on my globular welding skills probably 20 years since I welded.
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I'm running a single turbo 6266 .82 AR with stock exhaust. Obviously I don't have cats because of the single turbo. I did this mainly because I wanted it to be as quietly as possible. (That being said, with the cats deleted, my cold start is still decently loud.) With the open dump pipe, i don't think the stock exhaust matters as much once I'm in full boost? I was also told the stock exhaust wasn't as restrictive as people say, which is why i kept it.
I'm with Torgus on this. I don't believe the stock exhaust is a restriction below 700 whp. I plan on building my own 3.5 exhaust over the winter just to see how it sounds (I've got a VRSF street muffler to use.) The problem is I don't want mine to be louder than stock, at all. The best part of my car is how quiet it is. Granted, if it picks up 50whp with a 3.5 vs stock, I'll suffer with it being louder.
While I can't hook at all, from 40 rolls at the track it's pretty decent. I am able to beat 10.0 cars consistently - it surprises the hell out of all the big supercharged v8s lol. Best trap is 135. I know roll racing isn't the most popular, but my car isn't and won't ever be setup to cut a 1.5 60ft. Doing a 40 roll eliminates the launch and results in the same trap speed you'd get if you did a 1.6 60ft.
While I can't hook at all, from 40 rolls at the track it's pretty decent. I am able to beat 10.0 cars consistently - it surprises the hell out of all the big supercharged v8s lol. Best trap is 135. I know roll racing isn't the most popular, but my car isn't and won't ever be setup to cut a 1.5 60ft. Doing a 40 roll eliminates the launch and results in the same trap speed you'd get if you did a 1.6 60ft.
What is your plan on the exhaust about the sound level? Straight pipe to the muffler probably won´t do it
I was hoping a resonator and maybe a helmholtz tube would be enough. People say the street exhaust is quiet, but I have no direct experience.What is your plan on the exhaust about the sound level? Straight pipe to the muffler probably won´t do it
The Street exhaust normally is a straight pipe to the muffler and is fairly quiet. A resonator would help clean up the tone.
I have this exhaust setup on my car and it sounds very similar to stock exhaust with downpipes. If you run the street exhaust without a vibrant resonator, it will drone at low rpms. After adding the 3.5 inch vibrant resonator, it got rid of the drone and it sounds really good especially with bigger turbos.
This is a great post, was wondering how bad the stock turbos were in regard to back pressure. Good to know for VANOS. What do you think the back pressure ratio is for stocks? 2:1+?I will go on to mention(I may be repeating myself) that the small AR creates HUGE backpressure on stock frame turbos or cast stock frame turbos. BP kills turbos faster than anything else, period. Even faster than overspinning(ECU catches it to a degree causing limp mode preventing in more overspinning). The small AR is great for spool. Not for top end or high HP as discussed above.
Vendors have basically lied for years saying you can make 700whp on stock frames with nothing to worry about. They did this for marketing reasons and to sell turbos. Now when people go and try and do it you get failures left and right because of VERY high BP because of how damn small the AR is. You end up with a turbo that has extremely dangerous BP and it outputs VERY hot AITs into the induction piping/intercooler. This is why stock frame twins make so much more on E85 vs pump. They need a very high AKI to produce decent numbers. This is also why they spool up faster than a equally sized single turbo because the single turbo does not have a dangerously small AR. It's physics. Same amount of exhaust gases different ARs and wheel sizes. Thus 'they' went and had new castings made with larger ARs to reduce BP but this also reduces spool. It is not possible to have the same size wheels, increase AR, and have identical spool as the smaller AR but the marketing of the turbo manufacturers will tell you different because well, sales.
Now you could install a ST and achieve 1:1 backpressure and on 93 make more whp than stock frame style twins can on E85. You just have a large turbo the will be laggy in comparison to the twins. Now add 100% E85 to that ST and watch it walk twins on the highway all day long. Again it's give or take you can't have your cake and eat it too. Like the video I posted above says: want a great motor for drag racing only that lives at 7-10k only? Just like that GTR in the video mind you. I hope you don't mind the horrible spool because all you want it the most top end possible. This is the opposite of what you would want for a track car or for autoX or even daily driver.
At the end of the day wheel size and AR will mainly determine the max HP and lag/spool the various turbos will produce on the n54.
Glowing white hot:
Those are stock 10Ts. Imagine the same stock frame but with 20Ts pushing 3x the HP as stock through the same SMALL AR.
So how does this all go back to the stock exhaust you might be asking? Well the stock exhaust is not the restriction you should be most focused on. It's the restriction in your turbo(s).
Again, any factual data showing the stock e9x exhaust is a restriction at 550whp would be welcome.
Also feel free to read on regarding this topic here:
Stock exhaust system capacity with upgraded DP's
Hi Guys I have a question I have struggled to find the answer on by searching this forum. How much HP (or exhaust flow) can the stock exhaust system handle with just a 3” catless DP upgrade before the backpressure would cause problems for the turbos or other equipment? The reason for my...
To end it:
https://www.n54tech.com/forums/showthread.php?t=36154
I believe Terry dynoed with his cut out set up and saw a 27 whp gain.
That is on the 135i, which has a pretty bad exhaust. The 335i e90 that I have has no cats, just stock resonator and muffler. We tested that vs open dp and saw no gains at all with 800whp+
Payam and BMS don't sell exhausts for the n54. They have nothing to gain by lying about this one way or the other. They are also the most reputable vendor this platform has BY FAR. No drama. Just posts results and sells product.
In my experience the street was much louder than I expected. The RB GF's seem to produce a raspier exhaust note. I had a lot of rasp with them and later added a borla XR1 inline to clean up the sounds drone. After that it sounded great. I also tried agency power, very raspy.
If anyone is looking for a quiet aftermarket exhaust look into Milltek. Very to no drone and a nice tone. Not too much louder than factory catback.
How much louder is the street exhaust with the XR1 now? I have a street muffler and am going to build my own 3.5 single exhaust and was planning to use a vibrant 3.5 ultra quiet resonator and was wondering how it would compare. I've used the Borla Pro XS mufflers before and they are very quiet, but haven't use the XR1 before.
I think the vibrant resonator will do the trick. I think the XR1 and the vibrant resonator would yield similar results. Here are some before and after vids. I do think the turbos change the exhaust tone because many people say the street has no rasp
. Drone was bad without the additional resonator.Before
After
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