Exhuast testing Round 2 - HKS vs Buschur
Feb 20, 2007, 06:52 PM
#77
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With a car running weak octane fuel, often tuning is a dicey compromise between knock and power
I like to send out every car with as close to zero - if not zero knock counts
Sometimes its a stuggle to balance timing, MIVEC, and a/f and reach a desired power level and dance away from knock
There is no doubt that with the more free flowing Buschur exhuast the car was noticeably more knock free based upon knock count data - and this while making more power
Feb 20, 2007, 06:57 PM
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David - a lot of guys have tried to buy that V Band Buller muffler
Honestly, I really enjoy doing this testing. The customers enjoy it and the guys at The Shop enjoy it and I am not going to stop testing anytime soon.
PS - anyone who is interested in doing a few day "road test" with the Buschur unit - customer of mine or not - I will be lending this unit out to anyone who wants to drive around with it on their car for a few days and see if it passes the wife test and keeps your neighbors happy etc. The charge is FREE. You can take it home and install it yourself or pay the shop a few bucks to R & R it. You will have to leave a depoist but you are welcome to test drive it as much as you want.
Al
Feb 20, 2007, 07:05 PM
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That is exactly the case...you hit the nail on the head. Al even said in the initial post that the car was knock happy.
The ECU pulls timing due to knock, which could also affect AFRs. If this was tuned by Al, the low and high maps were most likely set the same, so the decrease in octane number wouldn't cause the low maps to be used at all, though.
Even if the HKS exhaust had 3 counts of knock more than the Buschur exhaust, that could be a 1* difference in timing, which can be roughly equal to 10 HP.
Al, don't get me wrong....I, too, applaud you for doing the testing. But, if the testing conditions aren't the same from one test to the next, then it isn't a comparison. It seems like you always try to sway the results the way you want them...that's why people are always arguing with you.
I can take a car that's knocking and dyno it, then put a sticker on the bumper and retune for no knock and gain 20 whp. Does that mean that the sticker made 20 whp? Come on already. If you really wanted a test between the two exhausts you would have tuned the HKS exhaust pefectly, dynoed, then put on the Buschur and tuned that exhaust, if any additional tuning was needed, then compare.
Eric
The ECU pulls timing due to knock, which could also affect AFRs. If this was tuned by Al, the low and high maps were most likely set the same, so the decrease in octane number wouldn't cause the low maps to be used at all, though.
Even if the HKS exhaust had 3 counts of knock more than the Buschur exhaust, that could be a 1* difference in timing, which can be roughly equal to 10 HP.
Al, don't get me wrong....I, too, applaud you for doing the testing. But, if the testing conditions aren't the same from one test to the next, then it isn't a comparison. It seems like you always try to sway the results the way you want them...that's why people are always arguing with you.
I can take a car that's knocking and dyno it, then put a sticker on the bumper and retune for no knock and gain 20 whp. Does that mean that the sticker made 20 whp? Come on already. If you really wanted a test between the two exhausts you would have tuned the HKS exhaust pefectly, dynoed, then put on the Buschur and tuned that exhaust, if any additional tuning was needed, then compare.
Eric
Car was tuned to 1 or less knock counts through power band with HKS unit but it took time and effort to get it there
With the addition of the Buschur unit it went so lean up top that it started knocking even more
I re-adjusted the a/f tables to achive the same exact a/f target with the Buschur Exhuast
At that point knock was at zero through the power band
thereafter
I did back to back pulls with the customers original Jestr tuned map and with my map for 4 full dyno pulls - just for my own information
I noted the jestr map was knocking less severely with the buschur exhuast than with the HKS unit. (note it was made for the HKS unit but the knock was severe - more than 6 - 7 through the power band and pulling 2 - 3 degrees of timing).
I hope this further clarifies some of the testing procedures
I try to do as fair a test as I can as I am interested in accuarte results myself
Feb 20, 2007, 07:19 PM
#82
What I did for a fair comparision was to tailor the a/f curves to be idential between the two units
When the Buschur unit was first put in it was a bit leaner on the top end
I dialed in the a/f tables 100% the same and the same timing to try and make as close a comparision as possible
You can see the a/f curves and they are nearly 100% identical
I think the reason why I did this was becuase the power was so close between the two the gain / or loss could have been explained by tuning alone - which is why I wanted the tuning to be identical
The near 9 whp gain in power in the Buschur unit up top required a increase in fuel
I hope that explains why we did a lot of pulls on this car
AL
When the Buschur unit was first put in it was a bit leaner on the top end
I dialed in the a/f tables 100% the same and the same timing to try and make as close a comparision as possible
You can see the a/f curves and they are nearly 100% identical
I think the reason why I did this was becuase the power was so close between the two the gain / or loss could have been explained by tuning alone - which is why I wanted the tuning to be identical
The near 9 whp gain in power in the Buschur unit up top required a increase in fuel
I hope that explains why we did a lot of pulls on this car
AL
Fair enough. Was just curious.
Feb 20, 2007, 10:54 PM
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Im not a big fan of BR. His exhust seems to be the best from what I have read over the past few months. Im thinking of gettin a BR TBE...still thinking....
Feb 20, 2007, 11:27 PM
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Glad to see the HKS makes good numbers beacause it is what I got
but it is damn heavy compared to other exhausts and more expensive. If I can do it all over again I would have went all out with a greddy ti or go inexpensive with buschur/ams.
but it is damn heavy compared to other exhausts and more expensive. If I can do it all over again I would have went all out with a greddy ti or go inexpensive with buschur/ams.
Feb 21, 2007, 08:25 AM
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The exhausts look almost identical. The only explanation for the horsepower loss or gains would be due to turbulence cause by the resonators or tuning. At these power levels I don't think a couple mm's make that much of a difference. Science not magic.
Feb 21, 2007, 09:15 AM
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And according to the HKS USA website the Hi-Power muffler is a 75mm so that means it does not decrease in diameter like some say. The only restriction is the resonator I would think and the slight power loss seems reasonable for a resonator of this size. The tubing is 2.953". Do you really think that makes a difference over 3"? No. And the neckdown, as I said, is so slight and small it is barely noticeable.
I am just happy I can keep mine now with a clear conscience and continue to put Buschur stuff under the hood and get this thing up to a stage 4 car this spring.
I am just happy I can keep mine now with a clear conscience and continue to put Buschur stuff under the hood and get this thing up to a stage 4 car this spring.
Feb 21, 2007, 09:37 AM
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David Bushur tested the difference between 2.5" and 3" downpipe mated to a 3" catback already. The difference as I remember 2whp. I suspect the rest of the difference here is due to the extra resonator and tuning.
For me, when picking an exhaust how loud it is vs performance gains plays an important role. I would gladly loose 5hp for half the noise and make up for that power loss elsewhere...
For me, when picking an exhaust how loud it is vs performance gains plays an important role. I would gladly loose 5hp for half the noise and make up for that power loss elsewhere...