cal30_sniper

iTrader: (6)

I've searched quite a bit on this topic, and come up with some conflicting answers. Hoping I can get some clarification here.

In short, I have an '02 LQ4 short block, PRC Stage 2.5 LS6 heads, 1-3/4" long tube headers, and I'm planning on running a mid 220 to low 230 duration cam through about a 2800rpm stall. I'm looking to build as much mid range power as possible, with somewhere around 420rwhp up top.

I currently have a 92mm Fast Big Mouth throttle body, and LS3 42lb injectors with an LS2/LS3 fuel rail. Would I be better served picking up an LS2 intake, having it ported, and putting the injectors, rail, and throttle body I already have on it (with some injector height adapters), or should I sell it all and pick up an LS6 intake and throttle body with equivalent LS1/LS6 style injectors (or the LS3 injectors with height adapters)?

I'm REALLY trying to optimize some low end torque with gains in the 2500-5000rpm range. I daily drive/cruise this car, and it might not ever even see a strip. It does see an autocross track every now and then.

Or should I just go big, buy a Fast 102, and put my rail, injectors, and 92mm TB on it?

Looking forward to the advice,

-cal30sniper

00SlvrSS

To be honest with it depends on how much money you're really wanting to spend. A Fast 102 is a bit much for what you're looking for. The 102 is really a top end type intake. Why bottle neck it with a 92mm tb? The cheaper route would be to go with a Fast 92 42 lb injectors with LS1 fuel rails. You would retain mid range torque with 92 intake better than a 102 and also expect a little more power up top than you're expecting. Good solid build you have going there.

Rise of the Phoenix

iTrader: (27)

Here are a few similar threads that contain some good information.

https://ls1tech.com/forums/generatio...ifold-ls1.html

https://ls1tech.com/forums/generatio...s2-intake.html

https://ls1tech.com/forums/generatio...-manifold.html

cal30_sniper

iTrader: (6)

I agree on the 102/102mm setup being too much. However, I think most of that "too much" would come from a 102mm TB, not the intake itself. The intake is only going to flow the amount of air that the TB lets past it. With a smaller cam and a 6.0L, I really think the 102mm TB would be too sluggish on throttle response. However, the faster response rate of a 92mm TB might work out pretty good for a drivable combo.

I also agree that the 92mm/92mm FAST combo is the absolute best out there. However, its also quite expensive, and requires me finding new rails and injectors. Honestly, I may just save another month and go that route anyways. However, if I could get most of the benefit of the unported FAST by using a ported LS2 intake with my current injectors and rails, then I'd be making a significant shortcut both in cost and parts hunting to go with the ported LS2.


Thanks for the links. 1st and 2nd thread I've already read, along with all the links inside them. Hadn't seen the 3rd thread yet, but I've read all the links, and the banter in its is mostly repeated "i read this somewhere else" from a lot of people that are more interested in arguing than answering technical questions.

It's been very well established that the LS2 suffers from poor construction. The question that hasn't been answered is, what about the construction limits the flow. Is it:
a) rough edges in the unwelded pieces inside that disrupt the flow via turbulence, etc.
or
b) the unsealed areas are leaking port to port, reducing the amount of air that can be drawn into the cylinder due to cross flow and screwing up port pressure waves.

I'm actually fairly versed in intake design. It was my specialty as an undergrad, including a lot of work with Ricardo Wave and 3D printing of intake plenums and runners. As a graduate student, I spent most of my time focused on wall induced turbulent flow. If the problem lies in rough edges creating turbulence and reversion, then porting should solve virtually all of them. In this case, I believe you will see a ported LS2 intake outflowing an LS6, simply due to its larger plenum volume and throttle opening. However, if the problem lies in cross-runner leaking, you're really screwing up the dynamics that intake runner technology is based on. In that case, nothing short of fully sealing up the ports is going to work.

From what I've seen, I tend to believe that the problem lies more in rough edges than cross-cylinder leaking. If that's the case, my heads, cam, exhaust 6.0L should respond better to the ported LS2 and Fast 92 TB setup than a factory LS6/78mm setup. With the LS6, I think the TB might start to be the limiting factor at that point. Not to mention, I'd have to get new rails, injector, and throttle body to run an LS6 setup, since I already have the accessories for an LS2 intake.

Simply put, I've yet to see a single comparison between an LS6 intake and a ported LS2 intake. There are plenty of stock LS6 vs LS2 comparisons, which is guaranteed to go towards the LS6. However, that's not really a budget minded comparison, as the ported LS2 and stock LS6 work out to being about the same price for someone starting from scratch. The question then, which one performs better without spending double the $$$ to step up to a Fast 92mm?

00SlvrSS

Well the ls6 intake is the better intake stock for stock. That's already been proven. And yes, the passage leakageis a big issue when it comes to performance and reliability. Yes the ls2 intake is cheaper, but if you're willing to do the work to fix the issues then go for it. But if you were to get it taken apart fix the problems and weld it back by someone, you can look forward to spend extra $$ there. Don't forget the throttle cable bracket and map extension if you don't already have them. But I would say go for the Fast to resolve the issue and sale the current setup without worries. IMO... Good luck with the build.

redbird555

iTrader: (14)

The 102 is no more of a top end intake than the 92. Its just a better design all around it loses nothing to the 92 and gains it all up top. if the op is in the market for an intake and has the money the 102 is the best option. with stock cubes the 102 tb becomes the problem. a 92 or using the fast 102 with the "hump" in the body to help velocity will be just fine.
Bold quoted for truth....

The problem is that you cant really port an ls2 without major work. The problem with it is inside the plenum itself because of its cheap sonic welded construction. When ported by a company they will see a few more whp than an ls6 but its negligible especially if you port the snout of the ls6 to 85mm and it costs 370 to have done. Imo its either a FAST or ls6.

99Bluz28

iTrader: (35)

Another option:

IMO, if you don't mind running a heavier aluminum intake manifold and the words Heat Soak don't make you tremble in fear, then get a BBK SSI intake manifold. It can be used for up to a 85mm tb without any porting needed, and on average make more power and cost less that the LS6 intake.