Results in! 4.8L w/ Magnum 76 Exhaust Pressure Test
Sep 28, 2012 | 01:39 AM
#1
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From: Charleston, SC
Results in! 4.8L w/ Magnum 76 Exhaust Pressure Test
Well i've had the itch to do this test so I finally stepped and knocked it out. I did the best I could so I hope it's useful to others in picking out the proper turbo for their setup.
Before I go on, I want to first say I'm very happy with what I have done performance wise with my Magnum turbo. That said, i'm just has happy to remove it for something better suited for my application.
I made a video showing the tonights testing with Go-Pro mounted on gauges. It did pretty well, but it was night time so it is what it is.
My test setup had a pressure drop of 4-5 psi at 50psi. This is likely from the 10 feet of hose required from cross-over pipe to pillar. Posted results in video did not include correction but I WILL include it in the posted numbers for those who don't watch the clip.
Test sample was from 3 runs that all had close to identical feedback. I can't confirm RPM, but all pulls was above 3500 before going to WOT and ending slighty above 6000.
From the camera on Average (corrected):
5 PSI Boost = 17 PSI Exhaust
10PSI Boost = 29 PSI Exhaust
15PSI Boost = 41 PSI Exhaust
18PSI Boost = 54 PSI Exhaust
21PSI Boost = 55 PSI Exhaust
Notice a nearly 3-1 Exh/Boost ratio from start to finish.
I then tested a 65 Wet shot, I turned boost down to counter boost spike to maintain a max of 21psi. Results showed little no gain in back pressure on the smaller nitrous shot that was triggered at 4000RPMS.
Conclusion, my truck never really picked up MPH at the track above 16-17PSI. Even at 20-21psi, MPH was nearly identical supporting the turbine wheel is past it's efficiency. I had to install a stiffer wastegate spring to make 18+psi possible, but this is a bad choice with this turbo.
While the BP seems high, i've read a lot of factory cars have BP of 2.5-3/1 for fast response and street manners. So this isn't horrible, but it is on the high side for a gear head looking for power.
In my "opinion". If your looking to make MAX power on this turbo on a 4.8L, keep it at or below 15psi with a upgraded cam engine. On a 5.3L, expect it to be a few PSI lower, 6.0 even lower.
Happy Boostin guys!! I will run the same test on my new BL475r within the next few weeks.
Video of testing, recommend watching in 720HD to see gauges:
Magnum 76mm/Q-Trim Exh Pressure Test on 4.8L - YouTube
Before I go on, I want to first say I'm very happy with what I have done performance wise with my Magnum turbo. That said, i'm just has happy to remove it for something better suited for my application.
I made a video showing the tonights testing with Go-Pro mounted on gauges. It did pretty well, but it was night time so it is what it is.
My test setup had a pressure drop of 4-5 psi at 50psi. This is likely from the 10 feet of hose required from cross-over pipe to pillar. Posted results in video did not include correction but I WILL include it in the posted numbers for those who don't watch the clip.
Test sample was from 3 runs that all had close to identical feedback. I can't confirm RPM, but all pulls was above 3500 before going to WOT and ending slighty above 6000.
From the camera on Average (corrected):
5 PSI Boost = 17 PSI Exhaust
10PSI Boost = 29 PSI Exhaust
15PSI Boost = 41 PSI Exhaust
18PSI Boost = 54 PSI Exhaust
21PSI Boost = 55 PSI Exhaust
Notice a nearly 3-1 Exh/Boost ratio from start to finish.
I then tested a 65 Wet shot, I turned boost down to counter boost spike to maintain a max of 21psi. Results showed little no gain in back pressure on the smaller nitrous shot that was triggered at 4000RPMS.
Conclusion, my truck never really picked up MPH at the track above 16-17PSI. Even at 20-21psi, MPH was nearly identical supporting the turbine wheel is past it's efficiency. I had to install a stiffer wastegate spring to make 18+psi possible, but this is a bad choice with this turbo.
While the BP seems high, i've read a lot of factory cars have BP of 2.5-3/1 for fast response and street manners. So this isn't horrible, but it is on the high side for a gear head looking for power.
In my "opinion". If your looking to make MAX power on this turbo on a 4.8L, keep it at or below 15psi with a upgraded cam engine. On a 5.3L, expect it to be a few PSI lower, 6.0 even lower.
Happy Boostin guys!! I will run the same test on my new BL475r within the next few weeks.
Video of testing, recommend watching in 720HD to see gauges:
Magnum 76mm/Q-Trim Exh Pressure Test on 4.8L - YouTube
Last edited by foose04; Sep 28, 2012 at 03:52 AM.
Sep 28, 2012 | 05:18 AM
#5
ME: Ya see honey, I MUST upgrade!
WIFE: WHAT!?!?!?! More money on that red head!!!!???
WIFE: "storms out of room "
ME: "takes advantage of quiet time to research new turbos"
Conclusion: Its all your fault Rob! LOL
WIFE: WHAT!?!?!?! More money on that red head!!!!???
WIFE: "storms out of room "
ME: "takes advantage of quiet time to research new turbos"
Conclusion: Its all your fault Rob! LOL
Sep 28, 2012 | 08:13 AM
#7
Did you do this test through the full exhaust or with the cut out open? I wonder if a larger exhaust pipe would help reduce the back pressure any. I know that small turbine wheel can only flow so much though.
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Sep 28, 2012 | 01:07 PM
#10
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From: Charleston, SC
Ahh, glad to hear I could help you get some alone time for research.Since you already have a good flowing downpipe (your 3.5"), i'd switch over to the billet PTE 76mm. It's a direct fit and all you need is a 3" to 2.5" to connect your intercooler pipe to turbo. My downpipe sucked, so since I was going from scrap I just went 4" BW style.
black00chev, it was with the cutout open.