GeneralDisorder

iTrader: (1)

LB9 with 1.6 rockers. I've got 24lb injectors and high volume pump so fueling isn't an issue. I'll be bolting on Don's headers and y-pipe and hooking that up catless to my flowmaster axle back.

What changes am I likely to need to make to my $6E tune when I bolt these on? And what gains am I likely to see?

I've searched but didn't come up with much.

Anyone have rough numbers for performance increase? I keep reading the stock y-pipe is terrible but I don't see any test numbers.

GD

ULTM8Z

Id use your BLMs as a gauge. If the headers are doing something requiring fueling changes, it's likely to show up in your BLMs. You'd have to have an accurate baseline ahead of time though.

GeneralDisorder

iTrader: (1)

Yes I will do that for sure but I don't expect BLM's to be much affected since those are locked out to 128 in PE mode. I doubt the exhaust is going to result in many changes to the idle and mid range. I'll be using my wideband for PE.

I'm more curious what gains people are seeing from the headers and y-pipe. I keep hearing the y-pipe is terrible, etc. I will do some volumetric efficiency calculations to estimate crank HP after I make the swap and check the tune.

GD

ULTM8Z

Yeah I was referring to part throttle. BLM changes could be an indicator of better scavenging.

Other than that, yeah you'll have to use your WB to play around with PE. If you knew what your AFRs were before, it'd be interesting to see if it gets leaner due to headers.

GeneralDisorder

iTrader: (1)

Being a MAF car I'm curious to see if it can basically compensate on its own. They were factory crazy rich. Mine was in the neighborhood of 10.5:1 in PE. I leaned it out but it didn't seem to make more power even at 12.

GD

RBob

iTrader: (1)

That is done on purpose to put out the cat-con. Otherwise they can turn into a blast furnace.

Don't forget to increase the maximum airflow allowed table.

RBob.

ULTM8Z

My car seems to like about 12.7:1. I notice something when going from 12 to about 12.7-13:1.

GeneralDisorder

iTrader: (1)

I'm so used to tuning turbo cars and I was being careful. Plus I am trying to figure out why I get some knock counts around 4500+ RPM. If certainly seems to be fake knock. When I put the headers on I'll try going leaner.

GD

GeneralDisorder

iTrader: (1)

So adding more fuel richens the mixture, cooling the exhaust gas temps?

I've seen cats glow red from misfires which is basically a bunch of unburned fuel. And thats why the OBD-II cars will flash the CEL for misfires because it will destroy a cat quickly.... I guess it's a balancing act and they tuned it for a specific target converter temp?

No matter I'm taking the converter out. So I won't have that problem. A procharger 383 (going in later) isn't going to work out with a converter I'm pretty sure.

Doing the headers now for tuning fun and because exhaust needs replaced anyway. Also get the fitment figured out so the 383 install goes that much smoother. Also curious what improvements it will actually make on a stock LB9. I'll be sure to post my numbers.

GD

ULTM8Z

It may lean out by itself a little due to improved scavenging...