Why were some characters banned? Because more fuel = more power.
#66
Former Vendor
iTrader: (31)
Join Date: Nov 2006
Location: Sunnyvale, CA
Posts: 15,442
Total Cats: 2,104
Am I missing something here?
If I set the timing to MBT-2* at 12.0:1, then that's essentially optimized. If I then decrease AFR to 11.6:1 by adding fuel, and the power goes up by 5whp, can either one of you explain to me how I could have somehow altered the timing at 12.0:1 in order to get that 5whp gain without adding the additional fuel?
I know MBT is different at 11.6:1, but it's irrelevant. I believe that MBT increases as AFR decreases (richer = slower flame front = more advance required to maintain peak pressure @10*ATDC), but let's look at both possibilities:
1. MBT is higher at 11.6:1, which means that I should have added timing to get closer to it, which would have increased power further
2. MBT is lower at 11.6:1, which means that I should have decreased timing to get closer to it, which would have increased power further.
I don't know why you guys think there's some trick to the idea that adding fuel increases power.
If I set the timing to MBT-2* at 12.0:1, then that's essentially optimized. If I then decrease AFR to 11.6:1 by adding fuel, and the power goes up by 5whp, can either one of you explain to me how I could have somehow altered the timing at 12.0:1 in order to get that 5whp gain without adding the additional fuel?
I know MBT is different at 11.6:1, but it's irrelevant. I believe that MBT increases as AFR decreases (richer = slower flame front = more advance required to maintain peak pressure @10*ATDC), but let's look at both possibilities:
1. MBT is higher at 11.6:1, which means that I should have added timing to get closer to it, which would have increased power further
2. MBT is lower at 11.6:1, which means that I should have decreased timing to get closer to it, which would have increased power further.
I don't know why you guys think there's some trick to the idea that adding fuel increases power.
#67
DEI liberal femininity
iTrader: (8)
Join Date: Jun 2005
Location: Fake Virginia
Posts: 19,338
Total Cats: 574
I guess I'm just confused where all the extra fuel is going. I get that you need more than stoichiometric for best power because not all of the fuel is available for the combustion process, but is this a high boost issue? does the fuel condense so much that you need more to get to the point where power is maximised?
#68
Elite Member
iTrader: (2)
Join Date: Jan 2007
Location: Los Angeles, CA
Posts: 8,682
Total Cats: 130
11.6 to 12.0 is not that big a difference. That is a 3.4% difference in the amount of fuel.
I know you're reporting the the data as recorded Andrew, but that small a percentage difference could be within the margin of error for the AFR sensor or the calibration. Also, I don't mean to be a dick, but 5hp is not a huge amount. For a 350hp pull, that is a 2% power increase. That is small enough as well to be caused by a change in humidity/temp/trims/even tire pressure blah blah. Or something like a .2psi difference in the amount of boost.
I know you're reporting the the data as recorded Andrew, but that small a percentage difference could be within the margin of error for the AFR sensor or the calibration. Also, I don't mean to be a dick, but 5hp is not a huge amount. For a 350hp pull, that is a 2% power increase. That is small enough as well to be caused by a change in humidity/temp/trims/even tire pressure blah blah. Or something like a .2psi difference in the amount of boost.
#69
Former Vendor
iTrader: (31)
Join Date: Nov 2006
Location: Sunnyvale, CA
Posts: 15,442
Total Cats: 2,104
I guess I'm just confused where all the extra fuel is going. I get that you need more than stoichiometric for best power because not all of the fuel is available for the combustion process, but is this a high boost issue? does the fuel condense so much that you need more to get to the point where power is maximised?
I don't mean to be a dick, but are you ******* trolling?
#70
Elite Member
iTrader: (2)
Join Date: Jan 2007
Location: Los Angeles, CA
Posts: 8,682
Total Cats: 130
So your suggestion is that even though I manually enriched the VE table to alter the AFRs, what really happened was that the VE table alterations had no effect, the AFR gauge suddenly swung 3.5% richer, and the dyno read 5whp higher, all due to margin of error?
I don't mean to be a dick, but are you ******* trolling?
And yes, lots of things can happen between pulls.
#74
DEI liberal femininity
iTrader: (8)
Join Date: Jun 2005
Location: Fake Virginia
Posts: 19,338
Total Cats: 574
Andrew: When you make counterintuitive discoveries that most people aren't comfortable with, you have to expect you'll be explaining them to some serious skeptics and dummies.
Just be glad it's us and not sjmarcy.
#76
Supporting Vendor
iTrader: (33)
Join Date: Jul 2006
Location: atlanta-ish
Posts: 12,659
Total Cats: 134
I still think that the extra fuel slowed down the combustion, and all things being equal (which they rarely ever are), less fuel and less timing would have made the same power. Was your air temp the same on both pulls? Was correction the same on both pulls?
There is another explanation though. The wideband calibration could be slightly off on the lean side.
I think the big picture lesson is that if you use the dyno to just hit a target AFR, you're doing it wrong.
#77
Elite Member
iTrader: (2)
Join Date: Jan 2007
Location: Los Angeles, CA
Posts: 8,682
Total Cats: 130
Haha, you were a little tough on our boy Fae (so I snipped that out), but there is some merit in what he said. A couple ponies can be within margin of error on a dyno. If you're talking about just a little difference, you do need to take multiple pulls to verify.
I still think that the extra fuel slowed down the combustion, and all things being equal (which they rarely ever are), less fuel and less timing would have made the same power. Was your air temp the same on both pulls? Was correction the same on both pulls?
There is another explanation though. The wideband calibration could be slightly off on the lean side.
I think the big picture lesson is that if you use the dyno to just hit a target AFR, you're doing it wrong.
I still think that the extra fuel slowed down the combustion, and all things being equal (which they rarely ever are), less fuel and less timing would have made the same power. Was your air temp the same on both pulls? Was correction the same on both pulls?
There is another explanation though. The wideband calibration could be slightly off on the lean side.
I think the big picture lesson is that if you use the dyno to just hit a target AFR, you're doing it wrong.
Yes that is what I have been saying.
FWIW my car made like 15hp more going from 11.5 to 12:1