BULLETSSMOKE

So I recently installed my ZZP header and downpipe with the magnaflow cat that comes with the combo and I thought all was good. Well it wasn't. I took it to the tuner that has been tuning my car for almost a year now and we discover that since my last tune with the GMPP intake and catback ONLY that now with the ZZP header/downpipe/cat combo I have lost 17.12 max HP and gained 2.92 max TQ. Now this is the weirdest thing I've ever seen. His only explanation that he thought might cause it would be that it's a mid-length header that it isn't getting enough backpressure and he says he has tested Cobalts on the extrude honed manifold from the LSJ and that that was the best header with gains he has tested so far. I lost horsepower. This is ridiculous. What should I do, get the extrude honed manifold or call ZZP and bitch them out or what... I'm in a nasty hole....please help.

XM15

Loss of backpressure is the reason for getting a header. There must be something else.

Jimmys2007CobaltSS/C

iTrader: (1)

dont know...when i had my installed and got tuned through hp tuners...my car pull really hard..now since i lost my tuned..through the dealership getting my car fixed...its like dog it doest pull hard anymore...i just need my tune back thats all...

but i cant think of adding performance header and loose hp???

CobaltBurst

im guessing you have a 2.4, if so your really not going to gain much from aheader back pressure is still your friend until you have forced induction or nitrous....

correct me if im wrong

stealthy1ss

iTrader: (1)

Before you bitch out ZZP what combination did you get? There are several combinations and you had control over what you picked.

D4u2s0t

you're tuner doesn't know what he's talking about if he thinks you lost power because you lost backpressure, and the gm manifold is the best gains backpressure = BAD

seriously, i would find a new tuner. of all the aftermarket manifolds, the gm extrude honed is one of the most restrictive, if not THE most restrictive available. maybe it wasn't installed properly or there's a nasty leak somewhere?

yea, what combo did you get?

BULLETSSMOKE

2.5 combo

XM15

Right and wrong. An n/a engine still needs some back pressure (like you pointed out), but the way the factory exhaust manifold is set up, there is some decent power to be gained by replacing it with a header.

Brandon97Z

iTrader: (1)

How's it feel on the ole but dyno? Do you feel like you lost power? wonder if the dyno is calibrated differently then the last time you went.

stealthy1ss

iTrader: (1)

That makes no sense. 1.5" or 1.75" primairies, it sounds like you have a 2.5" dp, and cat or no cat?

D4u2s0t

old myth. engines don't need backpressure. backpressure is bad

BULLETSSMOKE

Its running at 147.65hp and 161.95tq right now and before the header/dp/cat it was 164.77hp/159.03tq
1xMid length header and downpipe combo
Model:1.5 inch high temp paint
Option 1:Magnaflow cat
Option 2:Mild steel downpipe
Option 3:2.5 inch downpipe, bolt in

That's what it says on the receipt.

XM15

Thats weird. I've always heard that an n/a engine needs some backpressure. But like you said, old myth. I can't think of why it would need it, but thats always what I've heard. Stupid pumping losses. lol


I guess the trick is to minimize backpressure while maximizing exhaust gas velocity, right?

BULLETSSMOKE

https://www.zzperformance.com/cobalt...=545&catid=155

Here is EXACTLY what I bought.

D4u2s0t

exactly. it it was only getting rid of backpressure we'd all be buying 5" exhausts

stealthy1ss

iTrader: (1)

I know I am very familiar with the product. What I don't understand is how is it ZZP's fault if the product has no problems with it?

G85 SS

sell zzp and get the extruded and honed manifold.

D4u2s0t

that's taking a BIG step backwards.

it's probably not installed properly. doesn't make sense any other way

HunterKiller89

iTrader: (1)

shoulda gone 1.75 primaries, and maybe ceramic coating. do you have RPMs to go with the numbers? like 147.65hp@XXXRPM and 161.95tq@XXXRPM compared to 164.77hp@XXXRPM/159.03tq@XXXRPM? knowing if your powerband moved at all should help us understand possible problems

BULLETSSMOKE

147.65hp@5800RPM and 161.95tq@3750RPM AND 164.77hp@6200RPM and 159.03tq@5000RPM

I'd rather not have gone 1.75 because thats for more like 3" inch exhaust for like nonstock supercharged Cobalts. IMO

stealthy1ss

iTrader: (1)

Still haven't answered this. Why is it a bad day for ZZP?

BULLETSSMOKE

I meant bad day for my car, forget about it.

D4u2s0t

1.75 is too big for a 2.4 1.5 was the right way to go. but again, make sure it's installed right.

Rangerondubz

Your gonna lose to low end but the top should have gained

Saying that cars dont need back pressure would be the myth.......

Saying that cars dont need back pressure would be the myth.......

D4u2s0t

why does a car need backpressure exactly? it's a myth just like people that think that simply using higher octane gas burns cleaner and give them more power.