How much will I gain with results
11-01-2014, 12:26 PM
#21
I see where you guys are getting at where if the car picked up efficiency and put the same amount of fuel in, then yes it would run lean. Correct. But what I am getting at more, is that you are running off of pure MAF at 4000rpm and above (Taking that you aren't tuned in speed density), so, if the engine was more efficient, it would pull in slightly more air. So your car may have hit new MAF cells that maybe were not hit in previous tuning, so they could be off. Which could result in this rich condition. Hell some tuners even sometimes put this in tunes as a safety measure to ensure the car would not go lean, if it ever were to hit higher airflow values.
But regardless like I said before, the car was tuned before. So if we fixed this rich condition, and in effect the car picked up power, how would that not be because of the benefit of new exhaust? Where else would it have got this new power from?
But regardless like I said before, the car was tuned before. So if we fixed this rich condition, and in effect the car picked up power, how would that not be because of the benefit of new exhaust? Where else would it have got this new power from?
11-01-2014, 12:34 PM
#22
Capable of flowing more and actually flowing more are two different things. Larger pipes doesn't always equal more power or more flow. I'm surprised you haven't seen a no gain in power with too large of tubes before because it has been well documented by every major automotive performance publication and every major exhaust performance brand. Here's one that losses substantial power under the curve.. Here's another with losses under the curve too.
Here's more links. Sanderson Headers. Headers By Ed.
Here's more links. Sanderson Headers. Headers By Ed.
11-02-2014, 02:23 AM
#23
TECH Addict
I see where you guys are getting at where if the car picked up efficiency and put the same amount of fuel in, then yes it would run lean. Correct. But what I am getting at more, is that you are running off of pure MAF at 4000rpm and above (Taking that you aren't tuned in speed density), so, if the engine was more efficient, it would pull in slightly more air. So your car may have hit new MAF cells that maybe were not hit in previous tuning, so they could be off. Which could result in this rich condition. Hell some tuners even sometimes put this in tunes as a safety measure to ensure the car would not go lean, if it ever were to hit higher airflow values.
But regardless like I said before, the car was tuned before. So if we fixed this rich condition, and in effect the car picked up power, how would that not be because of the benefit of new exhaust? Where else would it have got this new power from?
But regardless like I said before, the car was tuned before. So if we fixed this rich condition, and in effect the car picked up power, how would that not be because of the benefit of new exhaust? Where else would it have got this new power from?
Basically, if it is a MAF tune and all he changed was the exhaust, the MAF will not need adjusted again in the tune. In MAF mode, if there is less air moving through the engine it'll fuel less. It only cares about MAP and IAT to target AFR's. It doesn't look at RPMs. So it doesn't know that the engine is moving less air because it doesn't know it's RPMs.
In SD mode it doesn't know actual air intake and it uses the MAP, RPM, and IAT to calibrate the fueling.
The benefit of the new exhaust is less back pressure. It's pumping losses have been reduced, therefore the engine is more efficient at making power per drop of fuel (BSFC). So it doesn't NEED to flow more air because it has less resistance through the exhaust primaries.
So it lost exhaust scavenging, but gained efficiency, ending at the same power (maybe even a couple horsepower more). In the end, on this build, it was worth it IMO. He lost little low end torque, gained efficiency, and lost no high end power. But, it'll only gain exhaust gas velocities from here with future mods. So it'll show it's worth in the future with larger power gains than the 1-3/4" headers would've put out; especially since it only cost dyno time.
11-03-2014, 10:02 PM
#24
Uhhh, incorrect. Under WOT it is in open loop relying on a power enrichment and using the VE table to calculate incoming air. No MAF, No stock o2 sensors, straight up PE and VE.
What ever is in the stoich setting of the tune will get divided by the PE multiplier.
When PE multiplier is set to 1.148 it will shoot for 12.8afr assuming stoich is set to 14.7
14.7 / 1.148 = 12.8
VE is then adjusted to correct the actual airflow the motor is seeing through the MAP and RPM range.
I do agree that getting AFR in line could increase the power seen.
11-04-2014, 09:36 AM
#25
Uhhh, incorrect. Under WOT it is in open loop relying on a power enrichment and using the VE table to calculate incoming air. No MAF, No stock o2 sensors, straight up PE and VE.
What ever is in the stoich setting of the tune will get divided by the PE multiplier.
When PE multiplier is set to 1.148 it will shoot for 12.8afr assuming stoich is set to 14.7
14.7 / 1.148 = 12.8
VE is then adjusted to correct the actual airflow the motor is seeing through the MAP and RPM range.
I do agree that getting AFR in line could increase the power seen.
What ever is in the stoich setting of the tune will get divided by the PE multiplier.
When PE multiplier is set to 1.148 it will shoot for 12.8afr assuming stoich is set to 14.7
14.7 / 1.148 = 12.8
VE is then adjusted to correct the actual airflow the motor is seeing through the MAP and RPM range.
I do agree that getting AFR in line could increase the power seen.
Plus the car sounds much better from the old exhaust setup. I am going back to the dyno in a few weeks with the 150 shot and purchased HP tuners and a wide band so we will see exactly what leaning her out does
11-04-2014, 10:19 AM
#26
Uhhh, incorrect. Under WOT it is in open loop relying on a power enrichment and using the VE table to calculate incoming air. No MAF, No stock o2 sensors, straight up PE and VE.
What ever is in the stoich setting of the tune will get divided by the PE multiplier.
When PE multiplier is set to 1.148 it will shoot for 12.8afr assuming stoich is set to 14.7
14.7 / 1.148 = 12.8
VE is then adjusted to correct the actual airflow the motor is seeing through the MAP and RPM range.
I do agree that getting AFR in line could increase the power seen.
What ever is in the stoich setting of the tune will get divided by the PE multiplier.
When PE multiplier is set to 1.148 it will shoot for 12.8afr assuming stoich is set to 14.7
14.7 / 1.148 = 12.8
VE is then adjusted to correct the actual airflow the motor is seeing through the MAP and RPM range.
I do agree that getting AFR in line could increase the power seen.
However since he is SD then then pe is referenced with ve. The PE doesnt care which table is being used its just an equation for proper fueling.
I agree though that without correcting afr the results are not valid
11-05-2014, 08:43 AM
#27
I wrote that response before the op stated he was in SD. The PE table is just a multiplier as you stated and will reference whatever table from the tune its told to. I assume (because the op never stated differently) that he ran a maf in which case above 4000 at wot the PE would be jiving with the maf table to get proper fueling not the ve. The O2's are ignored because its open loop but the maf is referenced normally for wot assuming no SD tune
However since he is SD then then pe is referenced with ve. The PE doesnt care which table is being used its just an equation for proper fueling.
I agree though that without correcting afr the results are not valid
However since he is SD then then pe is referenced with ve. The PE doesnt care which table is being used its just an equation for proper fueling.
I agree though that without correcting afr the results are not valid
11-05-2014, 06:58 PM
#28
Trust me, my degree is mechanical engineering and fluid systems. I understand very well what they did. I'm merely stating in order to get a fair comparison the af needs to be corrected. There's sinply too many variable to say they may or may not et better the truth is that no one knows
11-06-2014, 09:31 AM
#29
Trust me, my degree is mechanical engineering and fluid systems. I understand very well what they did. I'm merely stating in order to get a fair comparison the af needs to be corrected. There's sinply too many variable to say they may or may not et better the truth is that no one knows
We will know for sure in a couple weeks though and what it does with a 150 shot to boot.
11-06-2014, 06:37 PM
#30
TECH Addict
I think the 1-7/8 will shine more than the 1-3/4 on the juice.
01-15-2015, 01:33 PM
#31
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Always interesting thread!
Wonder why any of our experieced sponsors havent never join the conversation.
I have experienced twice the power loss from going to bigger primary. Last time was when i changed stock manifolds to 1 7/8 in a stock LS1. I can feel the loss of torq but its not dynoed.
First time was when i did trackracing pretty seriously few years a go and did alot developemet to that race engine. I notice that in a 1800cc engine 2mm primary diameter grow i lost 10hp/10Nm. Length was all the same. At the dyno it went rich and it never came up when we corrected it, so i changed back to smaller primary. The bigger isnt always better. My LS1 street car what i have now, i really respect power under curve, so in a street use i think 1 3/4 is a best average shoot for every small cubic LS street engine.
Wonder why any of our experieced sponsors havent never join the conversation.
I have experienced twice the power loss from going to bigger primary. Last time was when i changed stock manifolds to 1 7/8 in a stock LS1. I can feel the loss of torq but its not dynoed.
First time was when i did trackracing pretty seriously few years a go and did alot developemet to that race engine. I notice that in a 1800cc engine 2mm primary diameter grow i lost 10hp/10Nm. Length was all the same. At the dyno it went rich and it never came up when we corrected it, so i changed back to smaller primary. The bigger isnt always better. My LS1 street car what i have now, i really respect power under curve, so in a street use i think 1 3/4 is a best average shoot for every small cubic LS street engine.