Exhaust question

[97redstreak]

Hey guys, gotta a couple of questions, wanted to get some input.

I recently bought my first 3800. It's a 97 GTP, and the motor threw a rod or main bearing and screwed my block up two weeks after I got it.
I bought an L32 out of a 2006 to replace it.

Here's my questions:

As I'm sure ya'll know, things like headers are expensive so I'm pacing my upgrades.

I would like to do CAI, 3.4, 180ts.

I would also like to do exhaust, but I am wondering- should I run 3" all the way back, and get a 3" down pipe for now? or should I do a 3" DP and stock from there back for now. Or should I do 3"DP and catback etc. Just wondering what you guys would suggest. I just dropped 2k on the engine, and I'm a bit limited on funds for now. I don't want to spend more than 5-600 for now, hopefully that's including the TS, CAI, one range colder, and the 3.4" pulley.

Also, will these basic mods necessitate getting my PCM reprogrammed?

So what would you all recommend? Or should I do things in a different order, different parts, etc.

Let me know what ya'll think.

Thanks,

Adam

[fastech]

Originally Posted by 97redstreak

Hey guys, gotta a couple of questions, wanted to get some input.

I recently bought my first 3800. It's a 97 GTP, and the motor threw a rod or main bearing and screwed my block up two weeks after I got it.
I bought an L32 out of a 2006 to replace it.

Here's my questions:

As I'm sure ya'll know, things like headers are expensive so I'm pacing my upgrades.

I would like to do CAI, 3.4, 180ts.

I would also like to do exhaust, but I am wondering- should I run 3" all the way back, and get a 3" down pipe for now? or should I do a 3" DP and stock from there back for now. Or should I do 3"DP and catback etc. Just wondering what you guys would suggest. I just dropped 2k on the engine, and I'm a bit limited on funds for now. I don't want to spend more than 5-600 for now, hopefully that's including the TS, CAI, one range colder, and the 3.4" pulley.

Also, will these basic mods necessitate getting my PCM reprogrammed?

So what would you all recommend? Or should I do things in a different order, different parts, etc.

Let me know what ya'll think.

Thanks,

Adam

For now just do the 3"DP and a high flow cat. Worry about the rest later. Do the CAI, 180, and the pulley. Yes as always, at some point you are going to want to rewrite your PCM to get the most out of your mods.

[Louvered97GTP]

Originally Posted by fastech

For now just do the 3"DP and a high flow cat. Worry about the rest later. Do the CAI, 180, and the pulley. Yes as always, at some point you are going to want to rewrite your PCM to get the most out of your mods.

DP, pulley and PCM would be my suggestion. the car is still restricted by the stock exhaust manifolds anyways, so you won't be expelling more volume, just more velocity out of your exhaust. Larger flow cat and larger 3" cat back will only make you loose torque for the amount of beginning mods you are doing. Maybe get a used 99GTP throttle body from Ed Morad for an inexpensive increase in throttle response and have that tuned to your new PCM.
Scan guage should be a top priority so you can begin to see how your mods will affect your car.
Billy, do correct me if my observations on the exhaust are off base.

[fastech]

Does this model not have the constrictive u-bend or the undersized downpipe? I don't know for certain. Here is the info from another vendor:

Stock downpipes are double-walled tubing with an inside diameter of just over two inches. Following the restrictive downpipe section, the stock unit subjects the exhaust gases to the choking effects of the catalytic converter. After the cat, it flattens out into a section dubbed the infamous "U-Bend," which is a section of pipe crushed into a "U" shape by GM in order to fit a rear O2 sensor. This section has less volume than the same length of 2" pipe, and approaches the volume of a 1.75" pipe with the rear O2 sensor in place! Our downpipe eliminates all of the aforementioned problems! Gains of over 15HP have been seen, along with a substantial drop in knock. Most users can drop a pulley size and/or eliminate 5-7 degrees of knock. This part can typically be installed in under an hour

[97redstreak]

I'm not sure if my 97 has the u-bend or not. I'm guessing I should make that disappear no matter what?

Getting a 99GTP throttle body-is that still recommended if I'm swapping to a 06' 3.8? What's the difference in 97, 99, and 06 TB's?

For my DP, should I run a 3"DP with stock cat? Or get 3" with inline highflow cat? Should I go with something like a ZZP 3"-tapered-to-2.5"-with cat? How much torque/hp can I expect to lose by doing either, if I stay with stock from cat/dp back?

Also, for my PCM... I'm somewhat skeptical about buying/sending mine to get it reprogrammed, as every car isn't cookie cutter. Should I try and find a tuner, or trust that telling someone like Intense my mod will get it done how it needs to be done?

What size pulley would you recommend for the mods I listed?(CAI, 180ts, plugs, 3"DP, HF-cat, possibly PCM) 3.25? 3.3? 3.4? 3.6?

I know I'm asking a lot of questions, but like I said, I'm new to the 3800's and just wanna do this right the first time! I did it with my truck, figured I'd do it with my GTP too!

Thanks for the input guys.

BTW, if you wanna check out my truck, it' here.
Big Black Bitch: 2005 Chevrolet Silverado 2500HD Duramax 4x4- Cummin Stroke This!! - Dallas, Texas

[Louvered97GTP]

Hey Billy, I'd forgotten about the U-bend. You would know better than I would obviously, so don't you think a high flow cat won't really be needed until he gets ported heads and gets headers? I mean, if he opens up the exhaust too big too early, he will gain top end but the exhaust scavenging will loose low end toruqe, making the car appear more slughish for everyday driving. I mean, especially when we first start moding, we all like to feel the power gains down low where we mostly spend our time while daily driving the cars.

Adam, 97 and 98 TB are more restrictive design. 99+ flow better. Personally I think I remember hearing the 99 is the preferred so that's why i mention that year. The MAF will not interchange from your 97 to a 99 however. These are only suggestions if it's cheaper upgrade for the time being, otherwise might as well hold out for an aftermarket or vendor supplied TB if the cost difference is marginal. I had en extra 99TB lying around and installed in on my 97, different maf table had to be tuned into PCM and was much pleased with results. 06TB is a drive by wire setup is it not? Which would make it non compatible I believe.
I believe a 3.25 is too small. 3.5 or maybe 3.4 will fly. Rememebr, you are increasing air into your engine with smaller pulley, but you still bottleneck increased flow at the stock heads and exhaust manifolds.
Hopefully others will chime in to get more opinions.

[97redstreak]

Steve - thanks for the input. Yes, the 06TB is drive-by-wire. I purchased a TB adapted plate from ZZP. Any idea if the adapter would let me run a 99TB? I guess I'd still need to get my PCM updated if I did that, yes?

Ultimately, in a year or so, I'd like to try and get my car running mid-high 12's. Are the mods that I'm starting with a good enough place to start as far as supporting mod's? I understand about waiting on 3"exhaust till I start with rockers, cams, etc. I'm just hoping to make it a bit quicker.

Btw, have you got any data/numbers as far as a L32 swap into my L67 car? Just curious in the difference between the two. Any idea what my car "should-ish" run by dropping the L32 and adding the mods that I'm starting with?

[fastech]

Yo man what's happening? The '97 does have a u-bend and the '06 does have the constricted downpipe and "LEV" catalytic converter. If you can use the 97 D.P. and cat. that will help. Take the U-bent out. If your running a seriesIII ('04 and up - '06) you may want to stay with the 3.5 until you get the exhaust opened up and a PCM tuner. My '05 is virtually the same as an '06 and my 3.4 is a bit much without serious tuning.
As you mentioned, I don't want to slam any PCM vendors but there seems to be an awful lot of problems with those "cookie cutters", my vote is get your own HPT and tweak only what you want and only how much you want.
For the record, my year model didnt come with a u-bend so I neglected the exhaust till last because after all, just how much difference could it make? Well, I tell you it had a synergistic effect with the blower or something because it really woke up the upper end without loosing mid or low range. As a matter of fact I think it helped them as well.

[Louvered97GTP]

Adam, In light of Billy's new post, I would follow his advice and use a hi flow catalytic after all. He has more experience than I do so I wanted to make sure.
There's ported hi flow TB's for $200.00 and northstar kits for $290 or so. If you will be upgrading TB's look into these as well. It might just save you money down the road to just make this swap now, rather then spend the money again after to upgrade again. It all depends on your intended build and finances.
Oh and yes. you need an updated PCM to run different TB's. The vendors need to load custom MAF tables specific to the new TB.