1 Slow WS6

iTrader: (1)

1 3/4 tsp to 1 7/8 tsp headers with the edition of a 3 to 4 flowmaster merge on the y pipe. Made the same power but it ran a little richer.
Same dyno and run conditions were almost identical.

redbird555

iTrader: (14)

i dont mean to be a dick but this doesnt prove a damn thing. its been well documented larger headers pick up power.... bring the afr up to where the old one is and you will make more power no doubt. until that happens this comparison doesnt mean a thing

HCI2000SS

iTrader: (2)

I will personally say that the FM merge helped my car (regardless of a dyno number) gain a noticable amount of power. The merge in my Pacesetter ORY was the worst I've ever seen

1 Slow WS6

iTrader: (1)

This was from a conversation I had with my tuner tonight...

Feel free to quote me. It's a prefect example of a combo not needing the additional airflow where you increased the pipe size. It's the same as putting a larger throttle body on a motor that can't benefit from it. It doesn't mean it's going to automatically make more power. Even if you leaned it out it will not pick up substantially and what it does pickup you can't automatically attribute to the headers.

redbird555

iTrader: (14)

My advice is get a new tuner. Why didnt he retune afr? Installing a new part and not correcting afr makes comparisons useless. Thats like putting headers on a car in the 1st place and saying they only picked up 10 hp because leaning out the afr wouldnt increase power.

Bolt on cars including my cam only one pick up power all the time with 1-7/8 headers. With 510whp and a 383 no doubt you will pickup power with a better tune. Your afr looks to be around 12.3 and the other is around 13. 13-13.2:1 is best power 12.5 is borderline rich. I'd be willing to bet there's 10 hp there no problem. Its simply not an apples to apples thing if you dont correct the tune. I dont see how correcting the afr to what is was before would make the gains unattributable if anything that evens the playing field and thus would actually show the benefits of the larger primaries.

hrcslam

I agree the tune needs to be adjusted. But VE took a hit. If this is a MAF tune, it'll work it's self out. If SD it wont.

What I got from this is that the larger headers reduced VE. Same amount of fuel going in, but less air. So the smaller headers had better velocities, therefore better scavenging.

Leaning it out will help a bit, but it's still moving less air.

It's been well documented that larger headers don't always mean more horsepower. In many cases you can lose power, especially at lower engine RPMs due to lower exhaust gas velocities.

1 Slow WS6

iTrader: (1)

He wasn't there when I did this and he even pulled some fuel on the original tune to keep it safer. Either way I feel it would be just as close with maybe a few extra ponies with a retune. Believe me I wanted to see a gain myself. I asked when the motor was first built and put on the dyno if 1 7/8 would help and he said probably not but as usual the curiosity got the better of me, as it always does. In the end the headers didn't hurt me but didn't help. The AFR heads have a great exhaust velocity already and the bigger primary wasn't needed. On a head with a not so high exhaust velocity it probably would have helped. The 1 7/8 in the end would be a wash compared to the 1 3/4.

1 Slow WS6

iTrader: (1)

That's along the lines of what I was thinking.

MikeWS6

So just changing to bigger headers doesnt always pick up power? I still have the little 1 3/4's.

hrcslam

It really depends on your current build. At your power you likely won't pick up anything with larger primaries. I was looking for 1-5/8" primaries for my build, but I found a great deal on ceramic plated 1-3/4". The 1-5/8 LT's would've been custom and way too much money to justify.

redbird555

iTrader: (14)

the engine isnt moving less air.... the header are just capable of flowing more. 1-7/8" headers arent large enough to cause a big drop in velocity. i gained 10-12hp throughout with my swap and that was on a stock ls6 long block.

plenty of people gain power with larger headers, in fact this is the first time ive seen them not. However i still dont see how all of you are taking this as gospel. He dropped from 13.0 afr to ~12.3 thats a huge difference in terms of power. the maf will not make up for that change. the engine is now moving more air so it will throw the calibration off a bit. the ve table isnt used at wot so that has nothing to do with the dyno graph

93camaro_zzz

iTrader: (13)

Your tuner is dead wrong. If you leaned it out to where it should be, and it picked up power, it would be 100% from the benefit of the additional exhaust flow.

slow trap

iTrader: (22)

you guys are also forgetting he also changed to a better merge which everyone claims is so special. even if it gets leaned out and picks up 10 or more rw,how much was from the bigger primaries and how much was from the better merge ? more often than not, real world gains on a mild build it's a wash. just my $.02

MikeWS6

Thats what I was thinking. If I go the Procharger route the bigger pipes would help more.

redbird555

iTrader: (14)

ya this one got me lol... if he puts the afr back to where it was how could that not be a direct correlation to the additional exhaust flow.

also he changed the merge to a large one. if he had the normal tsp one on there the merge was already pretty good. people bitch about the pacesetter or old kooks merge which were just shitty.

hrcslam

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.

hrcslam

If he's pulling fuel to lean it out, it's moving less air. He can lean it out and gain some power back, but it won't be a lot of power he'll gain. There's more going on here, but the jist of it is it's moving less air.

To make more power you either need to increase efficiency or use more fuel and air. It looks like he's using less fuel and air, but increased efficiency and will end up where he left off with nothing but money lost in the process.

1 Slow WS6

iTrader: (1)

My tuner is Ed Hutchings you should talk to him, maybe then you will understand whats going on here. I put the merge on to get rid of the rasp the car had which it did.


It is moving less air you are correct again sir! The 1 3/4 obviously had better scavenging effect which would also help pull air into the cylinder. If the 1 7/8 were better at scavenging it would have leaned it out, it did not. I am gonna get it retuned but its not gonna help as much as some think and no money lost except for the dyno

hrcslam

Well that's always a good thing. With no real loss in power, it allows you to grow without hurting you in future mods. Plus now you know your engine is more efficient.

93camaro_zzz

iTrader: (13)

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?