5.3l 7876 1st dyno
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Teching In
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5.3l 7876 1st dyno 1st time Dyno for my winter build here. Vs7876. 5.3l with summit pro forged Pistons. Gen 4 rods. Btr stage 2 turbo cam. Prc 220 cnc head. Th400. 3400 stall precision converter. 9 inch with 3.50 gear. 28 tire. Huron speed kit. Made 555whp. At 12ish lbs. 14 degrees. Would creep up to 14 and try to go on after 6k. Only ran to 6400. Not trying to really rpm and push too hard. Had plenty of fuel. Afr was 11.7 to 12.3. does this sound pretty typical? I felt it'd make a little more. But I also didn't want to push anymore due to manual boost controller and I couldn't make it sit at anything over 12lbs. 44mm wastegate. Stock tb and ls6 intake. I'm wondering if that could be a little restrictive? Also. I'm trying to wrap my head around boost pressures. Would a larger...or more efficient turbo make more hp at same boost? This is a basic cast journal bearing unit. Theoretically it should right? I'm happy atm. 550 on the street messing around is a good bit and most don't understand that.
https://vm.tiktok.com/TTPdh475PC/
https://vm.tiktok.com/TTPdh475PC/
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Joined: Sep 2013
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From: Mechanicsburg, PA
What fuel are you running? What transmission? That seems about right for an unlocked auto with that timing and boost. Maybe a little soft, but each dyno can give different results. Did you confirm timing with a piston stop? Many are off a little. 6400 rpm is nothing. Run it to 7000 and look at the power curve to see if it's still making good power. What is your wastegate placement? I'd think a 44mm should be able to control boost. That 78/75 is a restriction and back pressure may be an issue for you. TB and intake should not be a restriction. A larger turbo would be more efficient at a given boost level. And yes, 550 wheel is about where the average driver can get in trouble quickly on the street.
Thread Starter
Teching In
Joined: Feb 2019
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What fuel are you running? What transmission? That seems about right for an unlocked auto with that timing and boost. Maybe a little soft, but each dyno can give different results. Did you confirm timing with a piston stop? Many are off a little. 6400 rpm is nothing. Run it to 7000 and look at the power curve to see if it's still making good power. What is your wastegate placement? I'd think a 44mm should be able to control boost. That 78/75 is a restriction and back pressure may be an issue for you. TB and intake should not be a restriction. A larger turbo would be more efficient at a given boost level. And yes, 550 wheel is about where the average driver can get in trouble quickly on the street.
Thanks. Yea it's on 93 pump. Th400 trans. I did confirm cam timing. Stock rod bolts scare me..wish I'd have went just to aftermaket rod honestly. It didn't fall off at 6400 just kinda flattened. And yes. It's a .95ar I thought it may be my limit. Maybe I'll do an upgrade there. It's fun as hell ATM though. Curious what it'll run now. As far as placement of wastegate. It's a Huron non AC kit. Supposed to be better placement. Thanks again.
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Joined: Sep 2013
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From: Mechanicsburg, PA
Try to find an LS that broke a rod bolt. Extremely rare. You'll probably break a rod first. Many here spin them to 8000. Did you confirm ignition timing? Some cranks have been known to be off. It's a long shot, but worth checking. Depending on which VS 78/75 you have, it may be close to it's limit. You have good flowing heads, so it may happen at a lower boost/restriction pressure.
1st time Dyno for my winter build here. Vs7876. 5.3l with summit pro forged Pistons. Gen 4 rods. Btr stage 2 turbo cam. Prc 220 cnc head. Th400. 3400 stall precision converter. 9 inch with 3.50 gear. 28 tire. Huron speed kit. Made 555whp. At 12ish lbs. 14 degrees. Would creep up to 14 and try to go on after 6k. Only ran to 6400. Not trying to really rpm and push too hard. Had plenty of fuel. Afr was 11.7 to 12.3. does this sound pretty typical? I felt it'd make a little more. But I also didn't want to push anymore due to manual boost controller and I couldn't make it sit at anything over 12lbs. 44mm wastegate. Stock tb and ls6 intake. I'm wondering if that could be a little restrictive? Also. I'm trying to wrap my head around boost pressures. Would a larger...or more efficient turbo make more hp at same boost? This is a basic cast journal bearing unit. Theoretically it should right? I'm happy atm. 550 on the street messing around is a good bit and most don't understand that.
https://vm.tiktok.com/TTPdh475PC/
https://vm.tiktok.com/TTPdh475PC/
Thread Starter
Teching In
Joined: Feb 2019
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yea i'm well aware of dynos just being tuning tools.. but man it looks better to have a bigger number 
like i said, i'm happy with it. i degree'd the cam and everything on build. i'm thinking it's just that i got the smaller exhaust side and that's whats doing it. it's making good power and i'm sure it'll be able to do more. the dyno/tuner even lol'd when i said i'd used stock rod bolts.. he didnt' even have much faith in them. this is my first "high hp" build so.
like i said, i'm happy with it. i degree'd the cam and everything on build. i'm thinking it's just that i got the smaller exhaust side and that's whats doing it. it's making good power and i'm sure it'll be able to do more. the dyno/tuner even lol'd when i said i'd used stock rod bolts.. he didnt' even have much faith in them. this is my first "high hp" build so. Nothing I'd sweat I mean th400 so unlocked converter and pump gas are a few things that will keep the power number down a bit (could be a lower reading one idk). You didn't say what compression ratio the engine is, but if it's higher it could work against you some on just straight pump gas. Just go have some fun with it.
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Before discussing optimizing the combo, I'd like to try to run some math. I'd be curious if you guys would agree with the below or what changes you'd make.
Cammed 5.3, call it 450 crank hp
15 psi is double atmosphere, so we'll say 12/15 is .80
450 x .80 = 360
450 + 360 = 810
810 divided by .80 = 648rwhp (.80 is drivetrain loss, unlocked converter).
Cammed 5.3, call it 450 crank hp
15 psi is double atmosphere, so we'll say 12/15 is .80
450 x .80 = 360
450 + 360 = 810
810 divided by .80 = 648rwhp (.80 is drivetrain loss, unlocked converter).
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Teching In
Joined: Feb 2019
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Before discussing optimizing the combo, I'd like to try to run some math. I'd be curious if you guys would agree with the below or what changes you'd make.
Cammed 5.3, call it 450 crank hp
15 psi is double atmosphere, so we'll say 12/15 is .80
450 x .80 = 360
450 + 360 = 810
810 divided by .80 = 648rwhp (.80 is drivetrain loss, unlocked converter).
Cammed 5.3, call it 450 crank hp
15 psi is double atmosphere, so we'll say 12/15 is .80
450 x .80 = 360
450 + 360 = 810
810 divided by .80 = 648rwhp (.80 is drivetrain loss, unlocked converter).
Was the HP curve getting pretty flat at 6400 or still increasing?
Now I know some tuners who would run more timing at that boost level.
A/A intercooler?
What is your exhaust setup? When you made 12 lbs was that with C02 or just off spring?
Now I know some tuners who would run more timing at that boost level.
A/A intercooler?
What is your exhaust setup? When you made 12 lbs was that with C02 or just off spring?
Your afr is too lean. 11.8:1, 93 pump gas, 10.4 compression, 11-12 degrees timing, 11-12psi….I broke a piston. Stock bottom end ls6. My recommendation is run 11.5:1 afr or richer on pump gas. It seemed to pull harder when it was fatter anyways. Same turbo you have too.
now I have a 5.3 and I’m on alot more boost. But I did swap out the housing for a 1.25 ar housing. It’s makes more power now at every boost level and has more power out of boost. The lag added was not much.
My advice to you is like I said above, fatten it up and add a small shot of washer fluid. A 5gph nozzle from McMaster carr, pre turbo, using your washer pump, will help carry you a few psi higher
now I have a 5.3 and I’m on alot more boost. But I did swap out the housing for a 1.25 ar housing. It’s makes more power now at every boost level and has more power out of boost. The lag added was not much.
My advice to you is like I said above, fatten it up and add a small shot of washer fluid. A 5gph nozzle from McMaster carr, pre turbo, using your washer pump, will help carry you a few psi higher
Thread Starter
Teching In
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It was pretty flat. I have air to air. Intake temps were 90 at end of pull. I only have a manual boost controller.
Thread Starter
Teching In
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I didn't mention before but I'm at 9.3 ish compression. I don't have a meth setup ATM. But I may do. I was hoping for more with less kinda thing with this setup. That's why the math had me confused. I know it doesn't always work like that in real world. And dynos are different. I am honestly curious about back pressure now because I realize boost isn't cylinder pressure. I hoped that having better flowing heads would help me hit my goal with less boost. But it seems I have a restriction that's keeping me from that. Only thing I can figure is the exhaust side. Hell I dunno lol. Maybe I'm just overthinking. A CO2 setup may be in future too. I couldn't make it keep from creeping when I tried to add a little. So pulls weren't the most consistent. Thanks for responses all.
They say every point increase in compression is worth 2-4% more total horsepower.
.3 x 648 = 19.44 = 628.56 rwhp.
Other guys suggesting adding fuel, I don't see that increasing power for you but you could go for it. But adding some timing would add some noticeable power. If you dyno again, you could throw in fresh plugs and make a pull and see where the timing mark is on the strap. All the sharp guys tell me we should be tuning off plugs.
.3 x 648 = 19.44 = 628.56 rwhp.
Other guys suggesting adding fuel, I don't see that increasing power for you but you could go for it. But adding some timing would add some noticeable power. If you dyno again, you could throw in fresh plugs and make a pull and see where the timing mark is on the strap. All the sharp guys tell me we should be tuning off plugs.
Last edited by Pro Stock John; Jan 30, 2022 at 10:48 PM.
Thread Starter
Teching In
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Yea man. I really just went to do a few pulls and make sure it made X power. Next time I'll try to have more time and maybe do plug change. I would've been more concerned if it made 300hp lol..I know I'm ballpark where It should theoretically be so that's ok for now. I really want to see what it'll run now. It for sure feels strong.
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From: Mechanicsburg, PA
Yea man. I really just went to do a few pulls and make sure it made X power. Next time I'll try to have more time and maybe do plug change. I would've been more concerned if it made 300hp lol..I know I'm ballpark where It should theoretically be so that's ok for now. I really want to see what it'll run now. It for sure feels strong.
My combo, 5.3, budget Summit forged pistons, gen 4 rods, 209/220 cam, 799 heads, VS 78/75 turbo, LS6 intake, made right at 500 @ 6K, 10 lbs, thru a 4L80E trans, 3.50 rear, 26.5 tire. I run 93 fuel, no IC'er, but 50/50 spray. Yea, I thought be cool to see it hit 600, you know, because everyone is making 700 on 8 lbs boost. My AFR's were in the 11's, timing was 15 or 16, would have to go back and look at the logs. A larger cam would prob bump the power up, same with boost, but I wanted it a little conservative. I couldn't get a good plug reading for some reason, I suspect a little more timing might have showed something. Car weighs 3720 with me, 76 AMC Hornet, very tame on the streets, which it was built for.
Richard Holdener just had a vid on U Tube, 3 diff boosted combos, and showed how they reacted to timing. Was def interesting how much power he picked up as timing increased, up to a safe level.
Few years back I ran a guy who dynoed 200HP more than my car made, I beat him, lol.
Richard Holdener just had a vid on U Tube, 3 diff boosted combos, and showed how they reacted to timing. Was def interesting how much power he picked up as timing increased, up to a safe level.
Few years back I ran a guy who dynoed 200HP more than my car made, I beat him, lol.
Thread Starter
Teching In
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My combo, 5.3, budget Summit forged pistons, gen 4 rods, 209/220 cam, 799 heads, VS 78/75 turbo, LS6 intake, made right at 500 @ 6K, 10 lbs, thru a 4L80E trans, 3.50 rear, 26.5 tire. I run 93 fuel, no IC'er, but 50/50 spray. Yea, I thought be cool to see it hit 600, you know, because everyone is making 700 on 8 lbs boost. My AFR's were in the 11's, timing was 15 or 16, would have to go back and look at the logs. A larger cam would prob bump the power up, same with boost, but I wanted it a little conservative. I couldn't get a good plug reading for some reason, I suspect a little more timing might have showed something. Car weighs 3720 with me, 76 AMC Hornet, very tame on the streets, which it was built for.
Richard Holdener just had a vid on U Tube, 3 diff boosted combos, and showed how they reacted to timing. Was def interesting how much power he picked up as timing increased, up to a safe level.
Few years back I ran a guy who dynoed 200HP more than my car made, I beat him, lol.
Richard Holdener just had a vid on U Tube, 3 diff boosted combos, and showed how they reacted to timing. Was def interesting how much power he picked up as timing increased, up to a safe level.
Few years back I ran a guy who dynoed 200HP more than my car made, I beat him, lol.
Awesome. My car is about 3750 me in it. I didn't change timing. Should have to see what it'd do but had limited time and was ok with this being my start point. Waiting for winter gets done so can see wth it'll run.
Before discussing optimizing the combo, I'd like to try to run some math. I'd be curious if you guys would agree with the below or what changes you'd make.
Cammed 5.3, call it 450 crank hp
15 psi is double atmosphere, so we'll say 12/15 is .80
450 x .80 = 360
450 + 360 = 810
810 divided by .80 = 648rwhp (.80 is drivetrain loss, unlocked converter).
Cammed 5.3, call it 450 crank hp
15 psi is double atmosphere, so we'll say 12/15 is .80
450 x .80 = 360
450 + 360 = 810
810 divided by .80 = 648rwhp (.80 is drivetrain loss, unlocked converter).
^^^ OP try with lower numbers maybe your results make more sense then?
Maybe some of you guys could share what plug readings you like to see, mark at the curve etc. I'd get a few sets of them if you were to go back to the dyno, and read the plugs.
Maybe some of you guys could share what plug readings you like to see, mark at the curve etc. I'd get a few sets of them if you were to go back to the dyno, and read the plugs.