So I finally got HP Tuners for my own and with my wideband installed I plan to tune my car late this summer into early fall. Almost 100° weather is not good to tune in. After heat soaking the other day my IAT2's were at around 165 degrees with an IAT of around 115. So won't be tuning crap till it's cooler weather. I'll be retuning my factory tune since my LTFT's are at +14 counts all around the board and I get a PO171 with my modded airbox from time to time.

I have searched to no end without any definitive information so I am trying to figure out which exhaust mod should be first. I know the LSJ responds well to exhaust mods and I am torn between a 3" downpipe with a 200 cell cat and 2.5" exit to bolt to the factory exhaust or should I go with a shorty header first since my factory cat is in good working order. I know the factory cat is a big restriction so I am leaning more towards the downpipe vs the header but I would like a bit more input as to which would be a better mod at first.

And in case anyone is wondering my Baby has 147k on the clock. I know I should probably do some maintenance on her first like a water pump and a full timing chain kit but I am thirsty for more power after driving it for 2 years.

 

subd to prevent incorrect information given to OP.

 

So your car is stock? Maybe before buying exhaust parts and tuning you should look into a stage kit. Zzp or whatever. Then after that look into exhaust mods and start tuning.

You could find a stage 2 kit for pretty cheap used and it's a good jump in power. Just my opinion.

But if your definitely looking For exhaust mods look into the zzp midlegth combo or long tube combo. Then you'd have both a header and dp.
If you have a budget hard choice. I would probably say downpipe

 

OP it all depends on your goals as far as exhaust goes. As far as headers go, I'd recommend either zzp's, or ottp's header. For exhaust I'd stick with the same. For pipe diameter on the exhaust, unless you plan on pushing the m62 or going TVS I'd stick with a 2.5" exhaust.

 

Here's an exhaust setup that will support 300+ whp....

Ported stock or GMPP manifold, 3" catless downpipe, quality 2.5" catback exhaust.

 

I contemplated going with a stage kit for a long time but I'm not too sure how long my factory clutch would hold a large power increase such as a stage kit. It is the original clutch with 147k miles on it AFAIK. Still holds good though and doesn't slip at all.

I want a little bit more growl than stock but not to raspy, hence not going cat-less. I plan to stick with ZZP's items unless after I get a DP I might try a badmab header possibly.

Also one of these days I plan to maybe try porting my stock manifold myself or at least smooth out the casting possibly. My wife doesn't mind me getting tools since that means one day I can fix things with them .

 

I'm catless and have no rasp... thats why I mention "quality" 2.5" catback.

Dont waste your money on a Badmab header, they are china garbage, and have smaller primaries than the stock mani.

Stick with ZZP if you dont want to follow the setup I provided for you.

My exact setup is GMPP ported manifold, ZZP 3" catless downpipe, 2.5" Corsa Touring exhaust. Zero rasp, zero drone, deep and mean at wot.

 

I would suggest not to get a Zzp cat back because the muffler and resonator they use aren't as great flowing and Zoomer(Zzp) has posted here their lives exhaust isn't much good last 275 HP. They use Maganflow and many complaints of the resonator failing/rattling and muffler packing blowing out and getting louder.

If budget is keeping from doing a lot at once I'd go in this order for your exhaust which I feel is s better choice to start then a stage kit.

-cat back=muffler and resonator flow the least cfm
-down pipe= cat is next in line for flow
-exhaust manifold=last least restrictive

Or cat back then mid length or long tube combo.

Staged posted great info. We also were just discussing this in another thread in this section where someone just dynoed.

 

the stock manifold is good to 350hp get rid of the muffler its the biggest restriction and there are 56765956753963596739563956735 exhaust threads on here use google

 

I plan on retaining my stock cat back. Just replacing either the DP or the header one.

I was just curious which would be a better bang for the buck upgrade between the header and DP and I tried to search but I never could find the answer I was really looking for, even after doing a google site search. With all the responses I've gotten I think it's best to keep the stock manifold and just get a higher flowing DP, and I have also read that the stock muffler is the highest restriction in the LSJ exhaust but I just don't want to give up the quiet drive around the city lol.

Thanks for all the help guys.

 

On my car I went with a zzp shorty header first, can't say it made huge power gains, or really any at all .I'm sure it helped slightly but how much I don't really know. I do like it though, as it did make some sound difference and you can put the stock heatsheild back onto it .Then I went to a zzp 3" catted downpipe with 2.5" exit for the stock catback. There definitely seemed to be a larger gain there .The car makes a good noise, you'll be able to tell it's modded, but with the stock catback it's still very quiet while cruising and low throttle applications .Can only really tell it's modded when you really step on it. I really like the setup.

I then went with a piece together stage "2". 60s, 2.8 and zzp canned tune .120k stock clutch, feels like it makes good power, idles great and is a blast to drive .I don't think going with a stage kit will hurt your clutch, but I don't know how much farther you'd want to go after that without at least looking at the gmpp clutch, my next mod when money allows. As well as mounts and control arm bushings.

Just my .02 cents.

 

SSfamilywagon, if not the zzp exhaust what do you suggest? Custom? Muffler and resonator brand choices? Size, if more than likely staying m62? Just curious.

 

http://www.trubendz.com/products/05-...magnaflow.html
^^^ for ballers on a budget.

Your best bang for the buck will be a cat-less DP but it will be noisy, that is the trade off

 

Using Borla S type and up,, Dynomax, Corsa or even the new Flowmaster Dbx units are good flowing.

Stock piping size is fine really. You could budget build by just replacing the resonator/muffler using stock piping.

Borla has a full cat back, Gm performance one is great, Ottp offers catbacks with your choice of mufflers

 

Is the gmpp still in production? What do you think about that link above, possibly with a resonator added? And with the budget build you mention of keeping the stock piping, would you have a new bend made for over the axle to eliminate that reduction? I'm guessing doing that would negate the whole budget idea .Those trubendz systems look decent, but I think you'd definitely want an added resonator to reduce drone/further decrease noise. I know most people don't want their balts to sound raspy/ricey. Wish the borla setup wasn't like 700$, or that was the price on it last time I was searching around.

 

Catless DP and ported stock manifold is good for 300whp with a GMPP cat-back, you don't need a large exhaust on these cars unless you are going for big power, the stock muffler is restrictive but the piping is fine and the downpipe is by far the worst part of the system stock.

As for the tuning, forget tuning for power in the heat but get your MAF dialed in now, which will correct your fuel trims, and teach you a lot. Once you've got the MAF scaled accurately, then max power tuning is just setting desired A/F and being done. Get your histograms setup right for maf error % and the rest of the tuning is fairly simple on an LSJ.

 

Lots of good info, but all the power you'll gain won't be any fun when you have a timing failure and grenade that engine that's been bringing you smiles for so long. I'd at a minimum replace the tensioners/guides/chains if your sprockets are in good shape, then worry about power.

 

They aren't making any new Gmmp exhaust but may be able to find one still lying around at a dealer somewhere. That's take a good parts guy knowing how to look in the computer correctly. Seen some used ones pop up every now and then.

Italian Joe hit the nail on the head. Like I said, muffler is worst flowing, dp is next. Piping size is addeqtue for m62. Big numbers step it up. 2.5 piping flows enough for close to 500 whp.

Tru bendz is a great option for a budget exhaust. Used them twice before just for the piping. Fit great. Unfortunately the Borla they offer isn't Borla's best unit, but definitely will be docile and flow enough for an m62

Agreed about Borla cat back price. Wish it was cheaper or I'd own it now. But you get great quality and warranty. I decided to build my own Borla cat back and when all said and done I'll have spent $300 for new mufflers and used piping.

 

The timing chain its self is not a failure point on these cars...

I agree about the guide bolts and tensioner though.

 

I plan to get the trims dialed in this fall. Right now here in northern Alabama it's been upper 90's with humidity high enough it feels like trying to breath under water. I still have to wire my lc-1 into the ac pressure sensor and setup hp tuners to convert that voltage to afr. Ive just been too lazy to do it because of the heat.

I have already replaced the tensioner within the last year and I would like to install new guides, chain, and water pump. My car still has the dex-cool coolant and I want to flush and refill that but I know with 147k I should probably do water pump as well with it. Again just have to find time to do it since it is my only vehicle.

All in all there is a ton of things I need or would like to do to keep it on the road as long as possible. All suspension bushings are OE, and I've had to replace the front sway arm bushing because they were non existent. I can only imagine what the front CAB's must be like. Going to need tires soon as well as an alignment.

 

good info in this thread. I'm not surprised considering the quality members in here. Now hopefully mr. bill stays out.

OP - check your IC pump as well. it seems to be working or your IAT2s would be 200+ but its work checking since its a failure item. Mine went at like 50k.

 

I know the IC pump works because I rebuilt it. It wasn't working for who knows how long before I checked it one day and noticed no coolant flowing. So I tore the motor down and filed some brushes to fit the brush holders and soldered those in. Works like a charm now.

 

good stuff