GT30Rs w/ 403ci LS2 - Can't make LOW boost?
11-08-2007, 09:33 PM
#21
Staging Lane
iTrader: (1)
Join Date: Nov 2006
Location: Las Vegas
Posts: 59
Likes: 0
Received 0 Likes
on
0 Posts
OK I have a APS kit on my GTO it is a early kit not like the new kits my kit came with GT2871Rs. APS modifies the internal wastegate it is bored out I am unsure of the diameter but I believe the bore size is around 32 to 34mm and they will easily maintain 6psi. I had to buy some Forge actuators with stiff springs to get the boost up to 15psi since they relieved the boost so fast. I am on a forged 364 LS2 now and have standard GT3071Rs and the lowest boost I have seen is 10psi but this has been a non issue to me since I have my boost set to 18psi.
Bottom line APS bored out the exhaust hsg to allow stock engines to maintain safe boost levels but when trying to push more boost or run larger displacement this creates a issue of not being able to crank the boost up higher. In your case it sounds like that is exactly what you need but you probably will have a hard time making over 12psi. I realize you ae not using a APS kit but I feel the info I provided is accurate in your case.
Just out of curiousity why are you wanting to run such low boost on a built engine?
Les
Bottom line APS bored out the exhaust hsg to allow stock engines to maintain safe boost levels but when trying to push more boost or run larger displacement this creates a issue of not being able to crank the boost up higher. In your case it sounds like that is exactly what you need but you probably will have a hard time making over 12psi. I realize you ae not using a APS kit but I feel the info I provided is accurate in your case.
Just out of curiousity why are you wanting to run such low boost on a built engine?
Les
11-08-2007, 11:39 PM
#22
Teching In
Thread Starter
iTrader: (1)
Join Date: Oct 2007
Location: Palo Alto, CA
Posts: 21
Likes: 0
Received 0 Likes
on
0 Posts
GGK - I'm going to have the pipes dropped tomorrow for a comparison dyno. I'd expect the boost to increase so it'll be hard to tell exactly what we gain.. I'm expecting ~20-25rw for the additional pound of boost of maybe 20hp for the restriction from the cats. If it's >50hp then maybe they are causing a problem.
Loboost - The low boost target isn't needed, I just wanted the range (ie. 6psi - 12psi) so I could dial in the speed based boost control to maximize traction for the street. We'll also be preloading the springs and trying to make high boost (~16psi) for a 104 octane tune. We'll see Friday how that turns out. The plan was maximum flexibility.. wanting to run 6psi on the springs (which should be the traction limit in 1st), then rolling up the boost as speed increases. If I drive it at 9.5psi/590rw and it feels planted, you're right, 6psi is a moot point.
Onfire - I'll check the boost signal for the wastegates to see if it's manifold or compressor and confirm that we're all good at 6psi for the reference signal. If that checks out (I'm pretty sure it will) we'll wire the gates open and see what happens.
Thanks again for the input, it's much appreciated.
Loboost - The low boost target isn't needed, I just wanted the range (ie. 6psi - 12psi) so I could dial in the speed based boost control to maximize traction for the street. We'll also be preloading the springs and trying to make high boost (~16psi) for a 104 octane tune. We'll see Friday how that turns out. The plan was maximum flexibility.. wanting to run 6psi on the springs (which should be the traction limit in 1st), then rolling up the boost as speed increases. If I drive it at 9.5psi/590rw and it feels planted, you're right, 6psi is a moot point.
Onfire - I'll check the boost signal for the wastegates to see if it's manifold or compressor and confirm that we're all good at 6psi for the reference signal. If that checks out (I'm pretty sure it will) we'll wire the gates open and see what happens.
Thanks again for the input, it's much appreciated.
Last edited by LS2TT; 11-08-2007 at 11:53 PM.
