Stage anything HVTB is worthless. The gains are negligible. Map out the intake cfm and you see its not a restriction on basically stock L36 N/A motor. These aren't V8's...

A P-log is a great investment because the front bank cylinders heat up like crazy, but I thought Rick already had one?

1.8 rockers sure, but to be honest unless you absolutly want to stay N/A then in the long run for all the mods you listed it would be cheaper to top swap... Plus you would make almost double the power of the mods listed.

The 3in dp won't hurt anything, I love the fuel efficency arguement when it comes to modding. If you drive normal the gas mileage isn't going to plummet.

I had better gas mileage driving around normal on my car when it was turbo than when I had a CAI, Exhaust and PCM. (Oh the good old days lol).

In fact I think modding your car helps fuel economy because you know how much of a hit it is every time you go WOT so you tend to less + if your making power more chance for things to break, replacing tires every couple months because you rip em up all the way throuugh 80mph isn't fun. So I don't believe the fan boy fuel economy argument at all.

Some people say oh it lost bottom end when really you gained alot more top end and probably litle on the low end so in comparrision it seems like you "lost" bottom end when really you didn't. Butt dyno's lie.

What I know (forgot his username) but there was a guy on CGP who dyno'd his car with stock dp, 2.5 dp, and 3in dp N/A. and he NEVER lost low end power in fact he even saw gains! on the 3in. AND he saw good gains throughout the mid-high band. Its not a blanket arguement its proven by fact and statisits. SO sure there will be odd ball motors that MAY lose low end on the 3in but to be honest it has yet to come up BACKED up by dyno proof to say anything otherwise than you gain power with a 3in dp. Plus he's doing a cat anyways.

[EDIT] I'm not arguing im just proving a point and bringing some life to this

I hate having to go back to find the same thread 100 times. I'll do my best. There is plenty of good dyno data that backs up the claim that a 3" DP is best for N/A of boosted setups.

Edit: Pretty much x2 to what Chris said. (I need to read the entire thread before posting)

Edit #2: http://www.clubgp.com/newforum/tm.asp?m=...Check=490016607

Read Wizbangs posts. That guy has forgotten more about the 3800 than all of us know combined.

I fully believe that modding will increase fuel economy...up to a point. There is always a threshold where the mods aim more for all out power at the expense of efficiency. The teams that race at LeMans fight this battle to the Nth degree since they are given an allotment of fuel to run 24hrs. You can make all the power you care to, but if the car is too thirsty and you run out, then you lose.

Some people might say that a drop of 2mpg is no big deal,or that is was worth it for the power, but that gets back to personal choice. For me, I'm always looking for the mod that delivers both increased power in the useable range where most of my driving is done, and a bump in the fuel numbers.

I'll be the first to admit that Wizbang's test data is very compelling. The only thing I find slightly off-putting is the chart system. Most charts I've seen before show HP numbers at a given rpm, and torque is shown on a seperate curve. His chart shows HP based on mph, and I assume the throttle was dropped off after 75.8 mph. I realize there are limits to what a chassis dyno reads, but all of the pulls started at 35mph, and the complaints about the loss of low end torque involve off-idle up to that speed.

I couldnt get the link you posted to work (could be problem with the plant network since I'm on the job right now) so I had just gone over to clubgp and done a search for posts by Wizbang.

Do you know of any other data he may have posted? I have to admit the guy does sound like he knows his cookies, and I'm close to being sold on the idea. His explanations on scavenging with manifolds vs headers makes perfect sense, but there was one other post about ZZP making a dyno pull on car making 381hp thru a Borla 2.5 set-up (they didnt specify if they meant cat-back or d/p)which was pretty impressive.

Rick, I know you must feel like a ping-pong ball, but this is how research goes. Corey and Chris both make strong cases, and I agree the "butt dyno" can be misleading, but numbers at the pump dont lie either. They are just as subjective to variables as track times, but given repeated tracking they are just as telling.

Here's another strange wrinkle. As I mentioned, Wizbang defintely sounds like he is no dummy to be sure, and I noticed a couple of comments on the ClubGP thread where it said he had worked closely with ZZ Performance. The following quote come directly from the ZZP page for downpipes...

"2.5 inch downpipes are designed for naturally aspirated applications where no loss in low end torque is desired. They can also be used in supercharge applications when the lowest possible cost is important. They come with interlock flex standard."

Now the question would be, is ZZP pandering to a myth, and promoting misinformation for the sake of a sale?...or do they have some real world experience and data to support their suggestion?
I think an email to ZZP is in order to see what they will say...which I am preparing to send in just a minute.

I got a response from ZZPerformance today. Below is my email followed by ZZ's response.
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ZZP,
I'm sure you have probably heard this question countless times (and probably tired of it) but a message board friend of mine in TN and I are both in the market for a downpipe. His car is a GP and mine is a Bonneville both equipped with the L36 engine.

The debate over a 2.5 vs 3in d/p has raged for who knows how long. There are so many threads see-sawing the point its mind-boggling. A member of ClubGP,screen name "Wizbang" makes a strong arguement for a 3in and shows wheel dyno data on HP output, but no figures on torque. Your very own page lists the 2.5 unit for n/a engines and even budget L67 applications.

I was hoping you might be able to provide some hard data of the merits of the 2.5 vs 3in so we both can make an informed decision.

Thanks very much in advance,
-Timmy
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If you guys are both naturally aspirated, go with the 2.5” pipe…it is the only way to go on an NA car…the 3” is just overkill and will affect low end torque. I don’t have numbers to back it up, but I have driven 1000 3800 cars…trust me, get the 2.5” J

-Steve

ZZPerformance.com
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I would have liked some hard data to be sure, but I would think this guys experience (been modding 3800s for over a decade) has to count for as much as one other guy. ZZ will make their money no matter which pipe you buy, so I dont think the response is profit oriented.

Well since the 3" is more expensive if it was profit driven they would be pushing you toward the 3".

Nope, no headers of any flavor are installed, nor was I really considering it. although yall are making it that much harder for me to stay away from such. darn it.

Looks like I need to revisit the data and re-research the two i.d. pipes. can we still agree that a h/f cat and u-bend del is still the way to go? or have I missed that new data, as well? god, Ive been away too long...

gentlemen, I sure thank you for all your research and leads. this'll make it easier for me to launch from.

my intent with the GP build is to free up what I can without digging too far into the car. more power and more efficiency doing bolt-ons is what Im intending. Im more than sure theres more that I can do by diggin deep into the mill and reengineer whats already there, or balance and blueprint after polishing and porting and making sure the plugs are indexed and...but thats simply too much for my goals with the GP. quick, efficient, sexy, reliable, able to stop on a dime, giving back a quarter in change. that camaro, on the other hand...muahahaha...LOL