[AmuroRay]

Someone requested an Exhaust only dyno

[435gc]

Great post.

Thanks.

Interesting that the midpipe gave the highest gains. Wouldn't have thought.

[n55david]

Originally Posted by 435gc

Great post.

Thanks.

Interesting that the midpipe gave the highest gains. Wouldn't have thought.

yeah I don't buy it. it's basically a resonator delete... nope

[thejeremyman9]

Originally Posted by Phantom10R

yeah I don't buy it. it's basically a resonator delete... nope

Yeah, me either, especially with stock DP. There's no way the exhaust is restricting more than the cat in the OEM DP.

[n55david]

Originally Posted by thejeremyman9

Yeah, me either, especially with stock DP. There's no way the exhaust is restricting more than the cat in the OEM DP.

Exactly!

[AmuroRay]

Originally Posted by thejeremyman9

Yeah, me either, especially with stock DP. There's no way the exhaust is restricting more than the cat in the OEM DP.

You know, we used to say the same thing about N/A cars with the stock header in place. I actually think this is believable.

[mike@x-ph.com]

Interesting result

Im mostly impressed by the extra power the AWE midpipe is making after 5000 RPM

Until we get a third-party dyno, there is no reason to discredit AWE. Especially that it has no history of inflating gains

[thejeremyman9]

The first chart doesn't show when the runs were done or the correction factor used on each.

The 2nd chart shows that other mods were installed on test vehicle (although kept equal between runs), the runs were a week apart, and a higher correction factor was used on the exhaust run.

First chart shows significant gains up top but 2nd chart shows almost no gains up top? So somehow AFE exhaust is supposedly making +27 wtq but no gains in HP in upper RPM?

It's too difficult to test something like an exhaust and not account any difference to just natural variability between runs due to the engine temps, air temps, timing corrections, etc. If you have ever watched the kies video on dynoing mods to post power gains, he talks about the same thing (i.e., manufacturers report gains as the highest HP run of 3 done post-mod compared to the lowest hp run of 3 pre-mod). If they had datalogs of the runs shown it would be easier to see if there is any influence of other factors. If you look at my virtual dyno thread you can see a massive difference between two pulls with literally no changes except for a bunch of timing corrections in one of them.

https://f30.bimmerpost.com/forums/sh....php?t=1710794

[n55david]

Originally Posted by thejeremyman9

The first chart doesn't show when the runs were done or the correction factor used on each.

The 2nd chart shows that other mods were installed on test vehicle (although kept equal between runs), the runs were a week apart, and a higher correction factor was used on the exhaust run.

First chart shows significant gains up top but 2nd chart shows almost no gains up top? So somehow AFE exhaust is supposedly making +27 wtq but no gains in HP in upper RPM?

It's too difficult to test something like an exhaust and not account any difference to just natural variability between runs due to the engine temps, air temps, timing corrections, etc. If you have ever watched the kies video on dynoing mods to post power gains, he talks about the same thing (i.e., manufacturers report gains as the highest HP run of 3 done post-mod compared to the lowest hp run of 3 pre-mod). If they had datalogs of the runs shown it would be easier to see if there is any influence of other factors. If you look at my virtual dyno thread you can see a massive difference between two pulls with literally no changes except for a bunch of timing corrections in one of them.

https://f30.bimmerpost.com/forums/sh....php?t=1710794

what you said plus..

it's pretty common for shops to use the lowest dyno results as the baseline and whatever to highest is as the after. its really easy to make a 5hp average gain look like 12hp etc. I used to do this for customers who wouldn't be happy with realistic numbers or for people who wanted to see big numbers in general.

these graphs are honestly worthless. I wish I still worked at a place where I could dyno whenever I wanted.

[AmuroRay]

Damn, tough crowd - but I will say it's normal to see larger gains on the lower end of the rpm range when we are speaking about the exhausts - something something exhaust gas flow, back pressure blah blah blah (I'm being dismissive about it because I'm too lazy to research Turbo cam timing and exhaust gas theory)

Here is another:



You'll note the same 10whp peak gains in the low end as with the AWE and AFE.

[AmuroRay]

Originally Posted by Phantom10R

what you said plus..

it's pretty common for shops to use the lowest dyno results as the baseline and whatever to highest is as the after. its really easy to make a 5hp average gain look like 12hp etc. I used to do this for customers who wouldn't be happy with realistic numbers or for people who wanted to see big numbers in general.

these graphs are honestly worthless. I wish I still worked at a place where I could dyno whenever I wanted.

110% this. They'll use the worst of 3 runs and baseline it against the best of the after runs, after the oil is warmed up. Either way, I'm not saying there will be 10WHP gains, but I absolutely believe there will be gains.

If I could do it on my N/A car, I have no doubts it would be apparent on this platform.

[thejeremyman9]

Bottom line is that these "gains" are all in the noise and natural variability IMO, especially without datalogs to corroborate or try and eliminate other variables. You can lose/gain 10-20 whp just from IATs, timing corrections, oil temp, etc.

Let's also not forget stock tune is load-based...

[AmuroRay]

Originally Posted by thejeremyman9

Bottom line is that these "gains" are all in the noise and natural variability IMO, especially without datalogs to corroborate or try and eliminate other variables. You can lose/gain 10-20 whp just from IATs, timing corrections, oil temp, etc.

Let's also not forget stock tune is load-based...

True, but how do we explain the measurable increase in power replacing the stock downpipe? If anything, the lack of gains on the top end are entirely due to the stock tune.

Hard to say - but $600 is steep for MAYBE 10whp, it will be the last thing I do.

[AmuroRay]

Revisiting this - I think there is something to this.
I'm pretty sure the F8X M has the same camshafts, and basically the same head ports (IE headflow) that the N55 has. One of the weaknesses of the N55 head as always been the total airflow, especially from the exhaust, which I think is around 155-160CFM.
https://s3.bimmerfile.com.s3.amazona...S55-Engine.pdf



The Stock F8X M cars do see a benefit from an single exhaust upgrade:


If the M4, with a similar powerlevel and flow (though, admittedly their turbos flow more) can gain this much, how much could a N55 gain - especially with a PS2 or larger? Keep in mind, the F8X midpipe exhaust is on the STOCK downpipe.

There was also this test on a Supra (original 2JZGTE)
https://www.motortrend.com/how-to/mo...ust-test-tech/

Here a large turbo supra even gained at the 300whp region (all the way up to 700whp) by upping the exhaust diameter. If CG Percision can't come through, custom would be the way to go - cut off a cheap downpipe's flange and connect it to a 3.5" outlet - connect to a 3.5" exhaust

I was looking into doing something like this, and I was trying to scoop up the Dinan M240 midpipe (3.25") but I can't find a used one to hack up...

I just think the potential is there .

[XutvJet]

Originally Posted by thejeremyman9

Bottom line is that these "gains" are all in the noise and natural variability IMO, especially without datalogs to corroborate or try and eliminate other variables. You can lose/gain 10-20 whp just from IATs, timing corrections, oil temp, etc.

Let's also not forget stock tune is load-based...

^This guy knows what's going. I've been modding and dynoing cars for decades. This is exactly that we're seeing here with these exhaust dynos.

I'll also add that turbo motor dyno numbers can be quite variable between runs compared to an naturally aspirated car. "Gains" of 10whp/10twq are likely not gains, but rather motor variance, especially in late model motors that have all sorts of safeguards and controls. For it to be a gain, it needs to be repeatable. At least three runs should show an increase over the best pre-mod dyno. Simple as that.

Dynojet data is by the most reliable in terms of gauging gains. This is because the dyno data is not easily manipulated by the operator and the way the dyno measures power is incredibly simple. Brake-based dynos like a Mustang dyno are great for true load-based tuning where you manipulate load to create road-like conditions like grades and such. It's by far the best dyno to tune on. A brake dyno IS NOT a good dyno to measure gains with though because the operator can manipulate the load, thus the gains/losses.

Lastly, gains are all about where they occur in the powerband. Gains that elevate the powerband will be measurable under the timing lights. A gain across 2000rpms or less won't do squat. A gain of 10whp/wtq across the powerband in a 3,500lb car might drop 1/4 mile ET by 0.1 seconds and maybe add 1mph in trap speed. Point being, you won't feel much. Ask me how I know this.

[thejeremyman9]

Originally Posted by XutvJet

Lastly, gains are all about where they occur in the powerband. Gains that elevate the powerband will be measurable under the timing lights. A gain across 2000rpms or less won't do squat. A gain of 10whp/wtq across the powerband in a 3,500lb car might drop 1/4 mile ET by 0.1 seconds and maybe add 1mph in trap speed. Point being, you won't feel much. Ask me how I know this.

Yup, and in most cases people are fixated on peak power number, which is much less relevant than area under the curve. This is especially true if you make peak power at/near redline (although that's not necessarily true for the N55 on stock turbo).

I consider the exhaust discussion similar to the intake one - sure, there is probably some flow efficiency to be gained relative to the stock system (from a physics standpoint it makes sense) but in terms of how much this actually translates into power gain is debatable, especially for stock turbo. So i consider them both noise mods, rather than bolt-on power mods, even if there is some potential there. As such, and "FBO" generally doesnt include intake or exhaust.

[AmuroRay]

10whp here and there eventually adds up to real power. I’ve been on the dyno a few times (read: frequently) in my N/A cars - I’ve yet to do so in my M235i. Dynojets are great for precision, not total accuracy.

You can run on one dynojet - and go to another and pretty much get the same numbers. I harp on IC efficiency because it’s one of the few variables you can control to get consistent power. And judging from the countless (read: a LOT) of dynos I’ve poured over, and logs - saying a repeatable 10whp is ‘variance’ or noise.

For my intake - there is a consistent noticeable bump in torque, which - noise or not, it’s there. For the exhaust - in theory it would aid in torque (which is great for the drag racers out there - torque is what helps your launch) but for me, I’m looking gain that last bit over 6000RPM. I’m not concerned with 5whp peak at 5700rpm - I want 10-25whp gains at 67000rpm.

According to my VD logs, I hold over 360whp near redline while most people are doing 330whp or less just from an inlet and DV:

[harkes]

Originally Posted by AmuroRay

10whp here and there eventually adds up to real power. I’ve been on the dyno a few times (read: frequently) in my N/A cars - I’ve yet to do so in my M235i. Dynojets are great for precision, not total accuracy.

You can run on one dynojet - and go to another and pretty much get the same numbers. I harp on IC efficiency because it’s one of the few variables you can control to get consistent power. And judging from the countless (read: a LOT) of dynos I’ve poured over, and logs - saying a repeatable 10whp is ‘variance’ or noise.

For my intake - there is a consistent noticeable bump in torque, which - noise or not, it’s there. For the exhaust - in theory it would aid in torque (which is great for the drag racers out there - torque is what helps your launch) but for me, I’m looking gain that last bit over 6000RPM. I’m not concerned with 5whp peak at 5700rpm - I want 10-25whp gains at 67000rpm.

According to my VD logs, I hold over 360whp near redline while most people are doing 330whp or less just from an inlet and DV:

Your car is making 370whp on stock tune?

[AmuroRay]

Originally Posted by harkes

Your car is making 370whp on stock tune?

? I have a StageFP tune.

[XutvJet]

Originally Posted by AmuroRay

For my intake - there is a consistent noticeable bump in torque, which - noise or not, it’s there. For the exhaust - in theory it would aid in torque (which is great for the drag racers out there - torque is what helps your launch) but for me, I’m looking gain that last bit over 6000RPM. I’m not concerned with 5whp peak at 5700rpm - I want 10-25whp gains at 67000rpm.

Without a real dyno, you really can't assume that your N55 is actually carrying most of the power to redline. I see this all the time in with Virtual Dyno plots. The numbers might be close to that of a Dynojet, but I question the overall power curve, especially beyond 6500rpms. It takes something more than intakes and DV work to change the shape of a powerband.

FYI, gaining 10-25 whp power from 6400-7000rpms isn't going to do much unless you plan on doing most of your racing in 4th, 5th, and 6th assuming you're a 6MT. In order to make use of that extra power, you need to extend the redline.

Back in the early 2000s I had a modded 96 Maxima 5MT (3000lb car in stock form). With the precats removed, I got that thing to go 14.6@95mph with 2.1 60 foots. It did 170whp and 190wtq on the Dynojet. Power peaked at 5600rpms and then fell like an anvil. Power at the 6600rpm fuel cut was 130whp. I then acquired a variable runner intake manifold from the overseas Maxima/I30. This setup allowed the VQ30 to breath far better above 5000rpms because of the longer secondary runners. The Maxima made 195whp@6400rpms and 190wtq. The motor lost about 5-10whp/wtq from 4000-5000rpms but gained a massive 60whp at 6400rpms compared to stock. Power held straight to fuel cut. I was convinced the car would go low 14s at 100mph. I went to the track and the car ran 14.6@96mph consistently with the same 2.1 60 foots under better conditions too! Same ET and only 1mph improvement. How could that be? Turns out that gaining a big power from 5600-6600rpms and a minor drop in power in the mid range and no change in the 6600rpm redline/fuel cut resulted in no real change in 1/4 mile ET or mph. I then did a Jim Wolf ECU flash and extended the redline 7200rpms. The tune also added a little bit of power in the mid range. The new dyno showed the same 195whp@6400rpms with power gradually falling off around 6600rpms and plummeting after 6800rpms. Power lost in the mid range was restored. I went back to the track. All shifts I took to the 7200rpm fuel cut. The car ran consistent 14.2s@99-100mph in the same conditions as before. If I didn't shift at right at fuel cut, the car got slower.

The point to all of this is that gaining power in the upper rpms often requires other changes in order to really see measurable acceleration results. A 100whp gain from 6500-7000rpms with a N55 would hardly make a difference in the 1/4 mile because of how long the car is actually accelerating in that range through the gears. Not until the taller gears (4th+) is the motor actually spending much time in that narrow range.

[AmuroRay]

I was a HUGE Nissan head back in the day - however I had the weaker, uglier, slower cousin- the KA powered Altima. FBO the car - including a JWT ecu, still header, and JWT Cams - stock 2” exhaust when everyone knew 3” was the ticket - and an automatic that I spliced the transmission line to increase pressure when I hit a switch, leading to faster shifts.

I was sure I was going to stay N/A forever, the the VQ was going to be my engine. Maybe a 2001 VQ30DEK maxima with a Variable manifold, because the stock manifold, as you mentioned, fell off

Or maybe a G35c with a Revup motor, or a HR? I like high rpm linear power bands. A JWT cammed HR with a 8000RPM redline, long tube headers and a Motordyne XYZ midpipe - solid 350whp plus

I’m not looking for a drag racer - I just want to build my car for fun. When I was at PBIR, I ran the stock tune (first time out) and loved the linear feel. One the street, torque is king, but it’s boring when the car starts wheezing past 6000rpm - I have to short shift the long straights if I drove it like that. It’s not fun was winding the car out to 6700rpm and feeling the car fall on its face because it has the torque curve of a dump truck. If people are looking for acceleration, they’ll need to look at final drive ratios / it will mechanically increase torque multiplication and actually make you a lot quicker - it’s why the 8AT is quicker than the manual, and M2 quicker than the M235i.

After I went to bed last night, I already knew this wouldn’t work. I realized the M4 exhaust in question had secondaries - so part of the gain was their removal. The second part was that if the majority of gains are down low, it’s just because there is efficiency gains to be had there just like with the intake. There aren’t going to be a lot of high end gains due to the turbo size.

Perhaps their will be gains in the mid and top end with an optimized tune to take advantage of the lower egts, but it still likely isn’t worth a whole lot.

[AmuroRay]

Also, you were slower because your average power was less - you don’t really have those issues in a boosted car.