In-Depth testing of 60mm Dual vs. 70mm Single
01-11-2011, 08:17 AM
#52
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Originally Posted by Disgustipated,Jan 11 2011, 03:44 AM
I will also add this bit of anecdotal evidence:
At a recent dyno session I went to, a guy with an '07 S2000 and some of the best mods you can get (Mugen intake, Toda header, T1r 70mm test pipe, T1R-EM Ti 70mm single exhaust, carbon cooling plate, Hondata IMG) put down 213 whp with the Toda Flashpro pre-tune.
My friend's '06 S2000 ( with just 75mm HKS exhaust, 70mm testpipe, PLM header, AEM V2 CAI) put down 213whp on the same dyno, same day, around the same time... with no Flashpro tune.
Either his engine is stronger from the factory or his "inferior" parts somehow worked out better, I don't know. But after he took off his 75mm exhaust and sold it to me, replacing it with his 70mm Greddy SE Dual, he complained of losing power and said that his 75mm HKS is the reason he put down such great number.
But his car with cheaper/"inferior" parts (not to mention less of them) put down the same numbers as a Flashpro pre-tuned S2K. While the Toda header tune doesn't produce a lot of top end whp, I'm sure it gives at least a little bit.
Anyways, if he can put down such great numbers, notice a difference between the 75mm and 70mm dual... not to mention the fact that I instantly felt gains as soon as I bolted on the 75mm exhaust (despite it being quieter than my old 70mm dual)... with all of that in mind, it's hard to really even begin to think that 3" exhausts don't make big power over the gimped 60mm stock, and even slightly smaller 70mm exhausts.
Just sayin'...
At a recent dyno session I went to, a guy with an '07 S2000 and some of the best mods you can get (Mugen intake, Toda header, T1r 70mm test pipe, T1R-EM Ti 70mm single exhaust, carbon cooling plate, Hondata IMG) put down 213 whp with the Toda Flashpro pre-tune.
My friend's '06 S2000 ( with just 75mm HKS exhaust, 70mm testpipe, PLM header, AEM V2 CAI) put down 213whp on the same dyno, same day, around the same time... with no Flashpro tune.
Either his engine is stronger from the factory or his "inferior" parts somehow worked out better, I don't know. But after he took off his 75mm exhaust and sold it to me, replacing it with his 70mm Greddy SE Dual, he complained of losing power and said that his 75mm HKS is the reason he put down such great number.
But his car with cheaper/"inferior" parts (not to mention less of them) put down the same numbers as a Flashpro pre-tuned S2K. While the Toda header tune doesn't produce a lot of top end whp, I'm sure it gives at least a little bit.
Anyways, if he can put down such great numbers, notice a difference between the 75mm and 70mm dual... not to mention the fact that I instantly felt gains as soon as I bolted on the 75mm exhaust (despite it being quieter than my old 70mm dual)... with all of that in mind, it's hard to really even begin to think that 3" exhausts don't make big power over the gimped 60mm stock, and even slightly smaller 70mm exhausts.
Just sayin'...So it seems clear that there is enough variance in the '06+ fuel systems that some run lean and others run rich. My guess is that the 2 you mention were probably running pretty close to the same AFR's that day despite the 2 different tunes. There is very little difference in timing in the upper RPMs, so AFR is the only thing that would impact peak dyno numbers between the 2. As for the "quality" of the mods on those cars, I don't think there's enough difference between the components you mentioned to make a difference in peak dyno numbers. However, I'd bet that there was a HUGE difference in midrange between them.
If I would have taken my car to the club dyno day with ONLY the 60mm test pipe and the Toda calibration, I still would have made higher dyno numbers than the other 2 '06 AP2s with intake, header, 70mm TP, 70mm exhaust, and FlashPro tunes.
It's also possible that the '07 wasn't fully broken in (less miles), had low tire pressure, excessive rear toe, poor valve adjustment, or a dirty air filter, etc....
01-11-2011, 08:21 AM
#53
Originally Posted by gernby,Jan 11 2011, 06:25 PM
Whether you put value in a software dyno, or not, you can't argue with the AFRs. If you swap out an exhaust, and it doesn't cause a change in AFR, then it DID NOT CHANGE POWER.
The results from the softdyno are at least for me more valuable than a test on a dyno in a closed room. Even with a big blower - the windstream is not really close to reality.
If a Test is made with always the same circumstances and at the same temperatures the comparison is reliable. And we all put parts on the car to get more power that can be felt during driving. I don't buy a part for a lot of money that makes power only within the tolerances of a dyno. With all it's correction factors....
01-11-2011, 08:29 AM
#54
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first of all, thanks for taking the time and doing this research. Appreciate the data.
Would it be possible for you to borrow someone 70mm test pipe and test it out?
When I put on the 70mm exhaust on my car, it made significant improvement throughout the whole powerband which is demonstrated on the softdyno and the edyno software.
I did the logs all within a 3-4 hours period. Did a few logs with stock exhaust. Install the exhaust and did a few logs after. This was done at the same stretch of road.
The mod on the car is injen cai intake and test pipe (70mm). The only change was the exhaust.
Would it be possible for you to borrow someone 70mm test pipe and test it out?
When I put on the 70mm exhaust on my car, it made significant improvement throughout the whole powerband which is demonstrated on the softdyno and the edyno software.
I did the logs all within a 3-4 hours period. Did a few logs with stock exhaust. Install the exhaust and did a few logs after. This was done at the same stretch of road.
The mod on the car is injen cai intake and test pipe (70mm). The only change was the exhaust.
01-11-2011, 08:30 AM
#55
I gotta say, gernby...while your science seems somewhat sound in testing...70+mm exhausts aren't going away anytime soon. When it comes to N/A tuning, I'd just get the biggest exhaust that my ears could stand and be done with it. In the long run, a few horses here or there isn't going to make a huge difference.
01-11-2011, 10:07 AM
#57
Originally Posted by gernby,Jan 11 2011, 08:25 AM
I'm disappointed that the 70mm made no gains, but you can't argue with facts. Whether you put value in a software dyno, or not, you can't argue with the AFRs. If you swap out an exhaust, and it doesn't cause a change in AFR, then it DID NOT CHANGE POWER.
Then when I put the 70mm on it was about in the 13's on the stock ECU no VAFC needed
Maybe the piping size doesn't matter but the stock system comes restrictive at higher RPM's ~ 8000+ ? that would maybe explain the conflicting results
01-11-2011, 10:42 AM
#58
Originally Posted by gernby,Jan 11 2011, 08:20 AM
You've already made your biased remarks in several threads, but you seem to ONLY limit your contribution to those biased remarks. It's clear that you make money in some way from a conventional dyno. I believe you either own one, and have to sell time on it, or you sell them.
You didn't even reply about the questions I had regarding your first post in this thread. I'm sure you're a knowledgeable tuner, so why won't you explain your assumption that the 70mm exhaust made no gains because of ignition timing? Why won't you explain how it is that I got very obvious and significant changes in AFR and torque from my PWJDM intake, 60mm test pipe, and T1R header, but NOTHING AT ALL from a 70mm exhaust? I tested each of them individually as well with all stock components, and in combinations with each other. The 70mm exhaust is the ONLY part I've tested that shows virtually no change.
I've never "worked" on a dyno, but I've paid for many, many dyno runs at multiple shops, and have been right there when they were performed. I've never had a run where the car wasn't pulling high IAT's, and the AFR curves have always fluctuated.
You ask me to trust you? Why?
You didn't even reply about the questions I had regarding your first post in this thread. I'm sure you're a knowledgeable tuner, so why won't you explain your assumption that the 70mm exhaust made no gains because of ignition timing? Why won't you explain how it is that I got very obvious and significant changes in AFR and torque from my PWJDM intake, 60mm test pipe, and T1R header, but NOTHING AT ALL from a 70mm exhaust? I tested each of them individually as well with all stock components, and in combinations with each other. The 70mm exhaust is the ONLY part I've tested that shows virtually no change.
I've never "worked" on a dyno, but I've paid for many, many dyno runs at multiple shops, and have been right there when they were performed. I've never had a run where the car wasn't pulling high IAT's, and the AFR curves have always fluctuated.
You ask me to trust you? Why?
i wouldn't really say that i'm biased because i actually do both. but after working on the dyno, it has become my personal preference.
as far as gains and the 70mm exhaust go, like everyone else has said on this thread you're bottle necking the 70mm exhaust right from the get go with the 60mm testpipe.
it's same principle as the silencer. it's a bottle neck right smack in the middle of the path of the exhaust flow.
as far as ignition timing goes, in your case i doubt there would've been any gain from more ignition timing. but like i said there probably would've been gains from leaning it out some as i saw those minor gains in the mid range in that one spot where it leaned out.
as far as the iat's go, if they're high, then give it some between passes to let those intake temps fall. adding a intake manifold gasket helps big time. and it's not that the afr's fluctuate. i mean they will depending on how your fuel comp table are setup for iat. but remember that the hot air isn't as dense as cold air. that alone will rob power.
and you don't have to trust me lol. rent the dyno for an hour and experiment some and see it for yourself.
01-11-2011, 11:40 AM
#59
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The AP1's all ran much richer than the '06+ AP2's I've datalogged. My brother's 100% stock '06 had AFR's up in the 14's too.
I have a Hondata IMG, and I think it works well. However, there is a fundamental design flaw in the DBW AP2's regarding the temp compensations. The IAT sensor is in the intake instead of the intake manifold. Since the intake cools down WAY faster than the intake manifold, the AFR's fluctuate much more from heat soak. As I said, My AFR ran very rich on all 3 of my pulls even though my IAT sensor showed the temp drop quickly.
Regarding b.r.i.a.n's response, I think the fact that you are renting instead of owning is pretty irrelivant. You make income from the conventional dyno, and software dynos threaten that income.
On another note, I have 2 new developments that give some favor to the 70mm exhaust. I did some more dyno pulls today with the 70mm exhaust and OEM header, since the weather is much better. The conditions aren't as similar to my previous tests as I'd like them to be, but good enough. Basically, the barometric pressure is considerably higher than usual AND it's considerably colder than usual (mid 20's). However, it's not so humid, and there's no wind.
The results show that the 70 mm exhaust leans out more in the midrange than it did with the T1R, and the torque gain in the midrange is bigger too in the same RPM range. This actually feels more significant than it looks on the graph, since the "surge" that comes as the high cam "comes into its own" is stretched forward by a few hundred RPMs. Basically, it's significantly smoother even though VTEC still engages at the same RPM. The slight dip in power at around 3400 RPMs is due to my trying out an earlier VTEC engagement. I actually did adjust the fuel tables, since they were more out of whack than before.
Here is today's 70mm test (green) compared to a test with the modified exhaust 2 weeks ago. Both graphs include SAE compensation + a compensation for a change in rear tire diameter.
The other development, which I think is more significant is that I realized that my testing of the modified exhaust was flawed. When I modified the exhaust last year, I did NOT expect it to make any significant gains. When my initial testing showed gains, I actually ignored them, and thought they were just testing error. Then I tested some more, and decided that the gains were real. However, the soft dyno wasn't as "mature" at that time.
When I did my tests a few weeks ago of everything, I may have stacked the decks against the retest of the exhaust. Basically, I derived a sequence of installs / uninstalls and tests that would reduce the amount of install / uninstall time while also giving me all the combinations of parts for tests. The test of the exhaust was at the 2nd half of the sequence, while the OEM catalytic converter was in place.
So to make a long story short, the reason why I didn't see any gains from the modified exhaust might have been due to the presence of the OEM cat. When it didn't make a change, I decided to not even bother testing the exhaust by itself any further. Maybe it did make gains, and those gains are just making the gains from the 70mm look smaller!
I will try to swap the non-modified AP2 exhaust back on before the owner comes to pick it up.
I have a Hondata IMG, and I think it works well. However, there is a fundamental design flaw in the DBW AP2's regarding the temp compensations. The IAT sensor is in the intake instead of the intake manifold. Since the intake cools down WAY faster than the intake manifold, the AFR's fluctuate much more from heat soak. As I said, My AFR ran very rich on all 3 of my pulls even though my IAT sensor showed the temp drop quickly.
Regarding b.r.i.a.n's response, I think the fact that you are renting instead of owning is pretty irrelivant. You make income from the conventional dyno, and software dynos threaten that income.
On another note, I have 2 new developments that give some favor to the 70mm exhaust. I did some more dyno pulls today with the 70mm exhaust and OEM header, since the weather is much better. The conditions aren't as similar to my previous tests as I'd like them to be, but good enough. Basically, the barometric pressure is considerably higher than usual AND it's considerably colder than usual (mid 20's). However, it's not so humid, and there's no wind.
The results show that the 70 mm exhaust leans out more in the midrange than it did with the T1R, and the torque gain in the midrange is bigger too in the same RPM range. This actually feels more significant than it looks on the graph, since the "surge" that comes as the high cam "comes into its own" is stretched forward by a few hundred RPMs. Basically, it's significantly smoother even though VTEC still engages at the same RPM. The slight dip in power at around 3400 RPMs is due to my trying out an earlier VTEC engagement. I actually did adjust the fuel tables, since they were more out of whack than before.
Here is today's 70mm test (green) compared to a test with the modified exhaust 2 weeks ago. Both graphs include SAE compensation + a compensation for a change in rear tire diameter.
The other development, which I think is more significant is that I realized that my testing of the modified exhaust was flawed. When I modified the exhaust last year, I did NOT expect it to make any significant gains. When my initial testing showed gains, I actually ignored them, and thought they were just testing error. Then I tested some more, and decided that the gains were real. However, the soft dyno wasn't as "mature" at that time.
When I did my tests a few weeks ago of everything, I may have stacked the decks against the retest of the exhaust. Basically, I derived a sequence of installs / uninstalls and tests that would reduce the amount of install / uninstall time while also giving me all the combinations of parts for tests. The test of the exhaust was at the 2nd half of the sequence, while the OEM catalytic converter was in place.
So to make a long story short, the reason why I didn't see any gains from the modified exhaust might have been due to the presence of the OEM cat. When it didn't make a change, I decided to not even bother testing the exhaust by itself any further. Maybe it did make gains, and those gains are just making the gains from the 70mm look smaller!
I will try to swap the non-modified AP2 exhaust back on before the owner comes to pick it up.
01-11-2011, 07:20 PM
#60
Registered User
Originally Posted by gernby,Jan 11 2011, 08:32 AM
What is your guarantee? Free breakfast?
I agree that it is intuitive that a bigger pipe will flow more. However, there's also the resonance / harmonics that impact flow. You need to remember that my test pipe is larger than the output of both of my headers. The inner diameter is 3mm larger than the output of my stock header. Why wouldn't the header be the bottle neck? Are you saying that you need to have a 70 mm collector mated to a 70 mm test pipe, which is mated to a 70 mm exhaust before you'll get ANY increase over the stock muffler?
I agree that it is intuitive that a bigger pipe will flow more. However, there's also the resonance / harmonics that impact flow. You need to remember that my test pipe is larger than the output of both of my headers. The inner diameter is 3mm larger than the output of my stock header. Why wouldn't the header be the bottle neck? Are you saying that you need to have a 70 mm collector mated to a 70 mm test pipe, which is mated to a 70 mm exhaust before you'll get ANY increase over the stock muffler?
A header is designed for ideal scavenging at a desired RPM range. I've read that the collector is actually the most crucial part of the whole header; with length, diameter and taper being factors. After the scavenging that takes place in the collector, their is ZERO opportunity for the exhaust pulses to increase velocity. This makes the whole exhaust system a restriction.
Go check out all of the other Honda motors making big gains EVERYWHERE with 3" exhausts or when they run open header. Be prepared to be amazed. This should work for any motor. Sense a motor is a motor, just different variables.