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I am G.O.N.E.
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2,005 Posts
Discussion Starter #1
hey everybody i just purchased a 06 red GTO about 3 weeks ago... i love it!!! its fast comfortable and rides great however there is just one problem...i love modding cars but the thing is i was/am a mustang guy and just got rid of my 99 gt so now i have this gto and had a few questions maybe some of you can help me with? like how much horsepower can the stock engine,tranny and suspension hold (a4) i was planning on doing the following mods.. fast90, udp, electric water pump, cai,heads,cam, full exhaust, and a good tune what would i be putting to the rear wheels?? and what do these things put to the rear wheels stock?? thanks guys ben
 

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The Psycho 10 sec. Goat
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1,968 Posts
First, welcome aboard! Hope you come to appreciate this car as much as most of us do.

Second, a warning. I've run into this with a few "was Mustang, now GTO" owners. Mustangs grow on trees, they fall from the sky like raindrops, they are everywhere. There is an advantage to that in that mod parts are plentiful and cheap. The disadvantage is that, well, everybody has one, so if you build a Mustang you are going to be, well, like hundreds of other Mustang owners in your vicinity.

The GTO is rare. I already see more of the new Solstices on the road than I do GTO's. That means you need to think long and hard before you go hacking on the car. Body parts, trim parts, etc. are expensive and you won't ever be able to go to the local salvage yard and find what you need; odds are there won't be a single GTO there.

That having been said, let the mods begin!! The LS2 really responds well to a cam. My cam only car puts down 404rwhp with bolt ons, cam, and a 3600 stall. The stall 'hides' the real power. I promise you, my engine is making right at 500 flywheel horsepower.

The fast90 intake I didn't bother with. In my opinion, the $/hp ratio is not sufficient to justify. I would consider it if my stock intake didn't flow enough for a particular heads/cam combo, but I would talk with the company making the heads to find out what hit I would take with the stock intake. Some have seen as much as a 15hp gain from porting the stock intake, so that is a reasonable option.

UDP is a no brainer, especially if you are already planning a cam change. You have to pull the crank pulley anyway, and the SLP UDP comes with a new crank bolt. The crank bolt on the LSx engines is torque-to-yield, which means it is one use only. The only difference I've noticed is that the steering wheel requires a little more effort. It is hardly noticeable and I actually like it that way.

The electric water pump I would not recommend unless this is going to be a trailer queen drag racing car. There has been a lot of talk about them over on LS1tech.com. Lots of people have complained about the life the of the electric water pumps. Again, the $/hp ratio is off. It is a rather expensive piece for not a lot of gains and there is a good chance you will have to replace it in about a year, from what I've read.

CAI's are more miss than hit. Regardless of increases in airflow, what really hurts the GTO is high underhood temps. Here is the stock timing/air temp table.

On 90* days I've seen IAT's in excess of 150*. One problem is the air blowing back from the radiator is as hot as a hair dryer and it blows right across the stock MAF pipe. Most CAI do nothing to address this problem. Also, most CAI do not pull in cooler air from outside the engine compartment, so they are not "Cold" as the name implies. Try to find an Over-The-Radiator (OTR) CAI (don't know if the one I saw on here ever actually panned out) or go with the Hardcore intake (see link in sig.) would be my recommendation.

Heads. We benefit tremendously from all the other GM vehicles running the LSx engine. There are a ton of good engine parts out there, including aftermarket heads. It doesn't hurt that the stock head is a good design which responds well to porting, polishing, etc. When considering worked over stock castings, pay attention to your total cost. Once it gets to the $2k range, you may as well step up to the aftermarket castings. AFR has long had the corner on LSx aftermarket heads, but ET Performance released their LSx heads about 6-8 months ago and everyone seems extremely pleased with those. Dart and Edelbrock also recently released some LSx castings, but I haven't heard as much about those. From what I've read, if money is no object, then you probably should be considering the ET heads; they are only a bit more expensive than other aftermarket offerings and they make good power.

Cam. If you are doing heads at the same time, my best recommendation is to get with your head company, discuss with them what you want out of the car. Let them make a head recommendation and a cam profile to go with it. For instance, if I were buying Total Engine Airflow (TEA) Stage 3 LS2/LS6/243 heads, I would definitely be on the phone with them asking about 1) intake manifold, 2) cam choice and 3) Torque Converter (see below). Same with aftermarket heads. If you have a good, reputable speed shop that is going to be doing the work, get with them. Finally, I'd also recommend talking to EDC here on this forum. He really knows his stuff when it comes to heads/valvetrain/intake/exhaust. He does custom cams to meet your needs. I will warn you, though, Ed likes to run high lift (i.e., .600+) even on moderate duration cams. The only downside to this is reduced valvetrain life, AFAIK. I've seen his cams put down some gorgeous power, though.

IF YOU ARE GOING CAM ONLY. I'd really recommend going with something with a 224-228 duration and about .580 lift. Above that you won't see much gain*, because your bumpstick will be outflowing the stock heads. I went with the 232/234 ~.600 stick that I have because I already had the cam. (*there are exceptions to this, there are 6m cars that have put down 450+ rwhp cam only that have big sticks.)

Exhaust -- honestly, especially given that you are looking at heads too, get the Kooks 1 7/8" headers. Kooks headers are excellent quality and you will see a gain over the 1 3/4" headers when you add cam/heads to the mix. Besides, they only cost $10 more than the smaller pipes. I went with off-road pipes as well. Finally, catback I went with Magnaflow based on a friend's car (I liked the sound) and on my tuner's (Formato) recommendation.

Numbers. When I took my car to the dyno the first time I had nitrous, Magnaflow catback, and a stock tune. N/A the car put down 352rwhp/349rwtq, which is 15-20hp more than most stock A4 05-06 LS2 cars I've seen dyno numbers on -at the same dyno-. With UDP, cam, heads, headers, catback, you can easily expect 450-500 rwhp, depending on how mild or wild you go.

Finally, you didn't mention it, but you really need to grab a higher stall torque converter, its good for about half a second off your ET. This is something else that needs to be matched to your cam & heads, so ask your tuner, head builder, cam guy about that as well. Before I built my car, I asked my tuner about all of my mods and I added the Magnaflow based on his recommendation. For my combo he recommended a Yank ss3600. I had to order springs, which I got from Futral to match their cam. While I had them on the phone I asked about TC, they said something in the 3400-3800 range. Then I called Yank and told him what mods I had, what cam, and he recommended the ss3600. When you have multiple people in the business making the same recommendation, you can't really go wrong.

Good luck and enjoy.

Oh yea, durability of the drivetrain. Best example that I have from personal experience is Dbluegoat's car. He's putting down right at 500rwhp. He's usually running 1.5-1.6 60ft times (not impressive for a Mustang, but damn good on these cars) and has run a best of 10.9. He has a LS1 with stock bottom end and a stock drivetrain including stock 4L60E tranny (with aftermarket TC). The 05-06 cars got the upgraded version of that tranny, the 4L65E.
 

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Owns 3 GTO's
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16,515 Posts
I just cannot say anything after that last post. Have fun modding, and welcome to the sight.
 

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I am G.O.N.E.
Joined
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2,005 Posts
Discussion Starter #5
wow!!! i really apprecitate you taking all that time to teach me a few things i really dont want to go over 450rwhp ( wondering if that can be achieved on stock heads??) and what exactly does a stall torque converter do?? and how much do they go for? thanks again
 
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