Big problem... I just helped my dad install a magnaflow cb and a stage 2 jet chip on his 300 srt-8. Wow what a difference...it was fast before, now its crazy. He already had an k&N intake which didnt do much but everything just seems to work so well together its incredible... Previously if we raced on the street it was always to close to call and we always run out of room. Now there is no way im even gonna try to keep up, we need to fix this!!!! My problem is that it seems nomatter what we do to the goats it only adds a couple of hp and everything i do to the srt8 adds 20+ hp. Between intake exhaust and chip his putting down about 50-60 more hp for 1500 bucks. So far i have a kn intake and im not very happy with it and this afternoon in a jealous rage i orderd a corsa sport cb and a slp underdrive pulley. I know its not gonna do a whole lot but i only had about a grand to spend right now and i dont want to install headers myself so i will have to pay someone when that time comes. Anyway after i install my next two mods next week do you think i will be able to keep up and if not what should i do next and how much should will it cost. Thanks for the help, i just dont want the goat to get his butt wooped.

Here is my recommendation...get a quality dyno tune. The general concensus (I don't know what year GTO you have) for an '05 GTO is that you will pick up between 25 Hp and 30 Hp. Speaking with a local tuner, I was told that with LT headers, catted mid-pipes, aftermarket cat-back, K&N cold air induction, underdrive pulley, and tune there was a least one GTO that was putting down 383 RWHP. The way that I figure it, that is approximately 440 Hp at the flywheel. Overall, I suspect that you would be very happy.

-K

57hp frictional loss through the drivetrain???? That sounds kinda steepish. lol.

57hp frictional loss through the drivetrain???? That sounds kinda steepish. lol.

Did I do my math wrong? I was assuming a 15% loss.

-K

Well, assuming the dyno run was pulled in direct (4th in a manual or 3rd in the 4L60 with the converter locked up) I'd highly doubt you'd lose 57hp in the 90 degree turn in the diff. Maybe 10-20 at the most. But probably less than 20.

The BEST way to calculate true hp is using a formula that includes TIME as one of the variables. Because after all, hp is truly a measurment of how much work can be done in a given amount of time. My grandpa always said, "you can run a saw mill with an alarm clock...just not very fast" lol.

Somewhere in my scribblings...I have the formula for calculating hp using the weight of your car, the 1/4 mile ET and the trap speed. It's amazingly accurate. I'll look for it.

cool. 2 questions.. what should i expect to pay to have lt headers installed and how do i go about finding a good tuner locally. I dont know of any shops near by and i dont want to hand my baby to a stranger. I live near Reading PA if that helps.

if your wanting cheap performance a catback exhaust was not the way to go on a GTO. Stick with your other exhaust mods, headers, and an X pipe will give decent gains.

Well, assuming the dyno run was pulled in direct (4th in a manual or 3rd in the 4L60 with the converter locked up) I'd highly doubt you'd lose 57hp in the 90 degree turn in the diff. Maybe 10-20 at the most. But probably less than 20.

Consider this and see if you can tell me the flaw in my logic. The stock '05 GTO produces 400 Hp at the flywheel. When dynoed this same vehicle puts down somewhere in the neighborhood of 340 RWHP. This number obviously varies from one GTO to the next, but I believe the number to be reasonable. With this serving as our basis, that is a 60 Hp differential. This differential corresponds to drivetrain losses of 15% (assuming a manual transmission...20% for an automatic). So if we assume that the drivetrain losses remain constant, we can say that a car that puts down 383 RWHP should be producing approximately 383 x 1.15 = 440.45 Hp. Is my understanding flawed?

-K

cool. 2 questions.. what should i expect to pay to have lt headers installed and how do i go about finding a good tuner locally. I dont know of any shops near by and i dont want to hand my baby to a stranger. I live near Reading PA if that helps.
Since I had long tube headers installed recently, I can tell you that I paid $350. As far as a local tuner, check out the following:

http://www.ls1tech.com/forums/sponsors.php

You simply input your zipcode and the distance you would be willing to drive to have the goat tuned. I believe that the results will be an ls1tech sponsor, so there may be a tuner or two (or three) that might not be listed. However, I think that those tuners listed would be considered reputable.

-K

Somewhere in my scribblings...I have the formula for calculating hp using the weight of your car, the 1/4 mile ET and the trap speed. It's amazingly accurate. I'll look for it.

I have not spent any time trying to figure out the math behind this online utility, but I think this is compareable to what you are talking about:

http://www.speedworldmotorplex.com/calc.htm

-K

if your wanting cheap performance a catback exhaust was not the way to go on a GTO. Stick with your other exhaust mods, headers, and an X pipe will give decent gains.

Agreed! Rather than replacing the stock catback, you money is better spent elsewhere if you are interested in making power. My opinion is that the catback replacement is good for changing the sound of the car. That does not mean that no performance gains are realized. Instead, it means that no significant performance gains come from replacing the stock catback.

After having thought about this a little, I have had an epiphany. If one make and model vehicle benefits more from a single specific modification than another, and we assume that the aftermarket part is basically the same for both vehicles, it is safe to assume that the vehicle benefitting more is not optimized as well as the vehicle that does not gain as much from the implementation of the modification in question. This is of couse relative to the system (i.e., exhaust, fuel delivery, air intake) impacted by the modification. I should note that this is only a theory and should not be considered absolute. After all, there is always an exception to the rule. Thanks for entertaining my late night/early morning boredom. ;)

-K

P.S. No animals were hurt as the result of this thought process.

La Phantom, Thanks for the info. How do you like your kooks headers? Also did you by them yourself or did you get them from the shop who installed them. I am having trouble finding them for a good price, the main reason i got the catback first. I found the corsa for $820 including tax and shipping!!!! The kooks are around 1200 everywhere i checked is this accurate? Thanks again, oh and by the way you are right on with your last statement, my dads factory exhaust looked like garbage and the first thing i said after lookin under the goat is that i wont get nearly what he got from the same mod and the stage 2 jet chip is doing what a custom tune would do to the goat maybe not as good but for $250 you cant beat it...I guess its good to know our cars come from the factory with good parts but at the same token it sucks that you have to dump big money into makin smaller gains, oh well its only money!!!!

I can't believe how expensive these headers are. I wonder if anyone has ever tried to fit up a set of F-body L/Ts for an LS motor (on a GTO)? You can pick THEM up, second hand, all day long on ebay for just a few hundred bucks.

I purchased my Kooks LT header from one of the sponsors of this site, T Byrne Motorsports (http://www.tbyrnemotorsports.com). In addition to to the headers I purchased the catted mid-pipes. The headers were sent to Jet Hot to receive the Sterling Jet Hot 1300 coating. This, plus shipping, cost $1,485. I should note that T Byrne was running a special at the time of my purchase. So your cost research appears to be accurate.

Overall, I love the Kooks headers. They are of a very high quality relative to their construction. I can feel the performance gain from these bad boys in the seat of my pants and I love the way they sound at WOT. I would definitely recommend the Kooks headers and T Byrne as a vendor. Going this route, it would be difficult to go wrong.

Owning a GTO does have its advantages, but there are plenty little things that could be fixed, such as the gear shift, rear end, 2-piece driveshaft, etc. Considering limited funds, I think that the following mods would be a good starting place, before introducing more intrusive mods:

CAI
LT's
Dyno Tune
Underdrive Pulley (optional)-K

Here's a link to a good HP calculator. Works pretty good.


http://www.dsm.org/tools/calchp.htm

Since I had long tube headers installed recently, I can tell you that I paid $350. As far as a local tuner, check out the following:

http://www.ls1tech.com/forums/sponsors.php

You simply input your zipcode and the distance you would be willing to drive to have the goat tuned. I believe that the results will be an ls1tech sponsor, so there may be a tuner or two (or three) that might not be listed. However, I think that those tuners listed would be considered reputable.


I tried this for kicks and I get ONE within 200 miles of me.

I think I live in the performance mod desert of the United States. (I'm sure I could find someone in St. Louis which is about 100 miles from me if I looked hard.) :)

If your in a desert, I must be on another planet. I had none within 300 miles and 2 within 400 miles.

Consider this and see if you can tell me the flaw in my logic. The stock '05 GTO produces 400 Hp at the flywheel. When dynoed this same vehicle puts down somewhere in the neighborhood of 340 RWHP.

I had the opportunity to dyno a 2005 GTO that remained completely stock. It was an A4, LS2 GTO rated at 400HP (crank). Alright Run one put 362 HP to the wheels. Run two put 356 to the wheels. Another person did run one where I did run two. Run onew yielded a 9.5% loss through drivetrain. Run two yielded a 11% loss through drivetrain. Keep in mind the car tested was equipped with an automatic transmission. A manual transmission would have even less loss (5 to 8%).

we can say that a car that puts down 383 RWHP should be producing approximately 383 x 1.15 = 440.45 Hp. Is my understanding flawed?

Your wrong. You took 115% of 383, not 15% off of the unknown number(450.588). It's simple algebra:

383/x = 85/100
cross multiply (38300 = 85x)
isolate (38300/85 = x)
x = 450.588
440 at the crank with a 15% loss through drivetrain would be 374 at the wheels.

Keep in mind that you feel torque, not horsepower. Torque is what moves the car, horsepower is what keeps the momentum. Up your torque, increase the punch you feel on acceleration. You also will get up to speed quicker.

dclaw_fantum, you are right regarding my math. However, the numbers I have seen as being typical for a 100% stock, manual transmission GTO is around 340 RWHP, and 320 RWHP for an automatic. I cannot confirm these, as I have not had my goat on a dyno. :D

-K

15% loss with a manual trans in a new car is a little much. 10% would still be on the high side of the normal drivetrain loss. But, the power the engine produces is affected by altitude, temperature, wear, intake (air) flow, exhaust flow, reversion, etc.
I'm willing to go out on a limb and say that these "normal" dyno's you speak of had K&N or Airhog type filters. Which do allow more air into the intake manifold. But if the head and exhaust don't flow any better, you won't flow more air through the head. Which is why, even with the vastly better breathe-ability of these filters, you will usually experience a loss in power and torque, no a gain. A cat-back will help to increase flow in the exhaust, but not nearly enough and not before the cats. Your best bolt-on gains will be seen in high-flow cats, headers, and chipping the ECM.