[JonD]

There is a LOT of info going on here in power loss from headers that I can’t believe is being put out there... real world butt dyno vs. rollers? I’m sorry what... :shrug:

[7speed]

Originally Posted by Umbriel

Agreed! I'll be there as soon as it opens back up to see where I am from stock which is 12.20 @ 114 mph. I expect to be 11.70 @ 119 now.

On stock tires 1/4 mi with same 60ft as my previous runs, I gained .2 and 3-4 mph with my tsp 1 7/8 w/cats .
Before that from rotofab only to tune and "e85" similar 60ft, I gained .4 and 5mph

[Laststandard]

Originally Posted by oldman

With 1 and 7/8 header the engine produced no power (as in can't move the car) between 850 rpm and 1200 rpm till I put cats in the car. With 2" just off the cuff it would be 850 to 1450 RPM (going by increase in tube volume), that is um 80 percent of my DD performance, also know as "goes down the street".

Sounds like you had a tune issue more than anything else.

[Umbriel]

Originally Posted by 7speed

On stock tires 1/4 mi with same 60ft as my previous runs, I gained .2 and 3-4 mph with my tsp 1 7/8 w/cats .
Before that from rotofab only to tune and "e85" similar 60ft, I gained .4 and 5mph

So I should be right on with that .5 and 5 mph guess. Thanks.

[7speed]

Originally Posted by Umbriel

So I should be right on with that .5 and 5 mph guess. Thanks.

Forgot to mention I did get a retune once headers went on.

Hopefully I get another .5 and 5mph when I get cam installed this Feb

[Umbriel]

Originally Posted by 7speed

Forgot to mention I did get a retune once headers went on.

Hopefully I get another .5 and 5mph when I get cam installed this Feb

I would think so, maybe even more honestly.

[oldman]

Originally Posted by JonD

There is a LOT of info going on here in power loss from headers that I can’t believe is being put out there... real world butt dyno vs. rollers? I’m sorry what... :shrug:

Dude, I'm talking part throttle driving, how is that going to show on a dyno?????

[RobbyBeefcake87]

Seems like some of the posts yesterday regarding cats and m6 cars got deleted. Anyone else experienced issues without cats on an m6 car running stock TB and IM? Not an msd.

[oldman]

Originally Posted by Umbriel

Odd I have 2 inch headers and have none of those issues, I even have the stock plug wires still on there *gasp*

Sounds like the ported MSD is the majority of the problem with your issues honestly.

Do you have a M6? Cause with the cats... all works fine and dandy. The autos have a AFM valve for low speed backpressure and / or the auto are not as sensitive to low speed flow.

[oldman]

Originally Posted by RobbyBeefcake87

Seems like some of the posts yesterday regarding cats and m6 cars got deleted. Anyone else experienced issues without cats on an m6 car running stock TB and IM? Not an msd.

I've only heard of this on an M6, and it is not only with LT, even CA and the full deletes have a strange harmonic. Some experience knock retard, I have not. But there is a low speed harmonic at low throttle settings say at 1200 RPM with ANY primary cat delete.

[CompleteStreet]

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[6spdhyperblue]

I haven’t noticed any part throttle loss with cat deletes or catless 2” LTHs on a m6 I’ve driven. Definitely strange

[Umbriel]

Originally Posted by Nicul15

I haven’t noticed any part throttle loss with cat deletes or catless 2” LTHs on a m6 I’ve driven. Definitely strange

His problem is definitely MSD and/or tune related. Needing back pressure to run properly is a myth.

https://vpexhaust.com/exhaust-back-pressure-a-myth/

[RobbyBeefcake87]

Originally Posted by Umbriel

His problem is definitely MSD and/or tune related. Needing back pressure to run properly is a myth.

https://vpexhaust.com/exhaust-back-pressure-a-myth/

This is what I was thinking, but I could be wrong. Is a tune necessary with CA cat delete pipes? I like them because they bolt on without cutting or welding and have o2 sensors. I'm just looking for tuneless bolt ons at the moment.