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Discussion Starter #41
That's
Only thing left is the turbos. Will Viren test them for you?
I know a lot of people have good luck with the Ching Chong turbos but I would try the Borg s366 and not look back. If everything else checks out what else could it be?
That's the point I'm at. These have a .96 a/r on the exhaust, I believe he makes a .84 ar housing, I wonder if that would be worth a shot? When I purchased them he had said they work great on 5.3 and 6 l ls engines, but after talking to some friends they said you really can't compare an ls to a sbc in terms of flow, which I really never thought about.
 

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Engine is an engine. If they make similar base power they will make similar numbers on boost. Ls heads are better, so it takes abigger 23 deg head to be more equivalent. At the same boost those turbos should be making the same or similar power regardless of how quickly they spool. Once spooled it shouldnt matter imo. Ar housing i dont think will change peak. It almost seems like they just do not flow
 

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I would look at the cam again. You did a head and turbo change. Sounds like the velocity is down on the heads from the bigger flow. Something else to look at how did it do going the way on timing? It may have better chamber in the new heads.
 

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Discussion Starter #45
I would look at the cam again. You did a head and turbo change. Sounds like the velocity is down on the heads from the bigger flow. Something else to look at how did it do going the way on timing? It may have better chamber in the new heads.
According to brodix it has the same combustion chamber, tuner apparently went up to 29°, but was weird that it didn't gain power for every 2° we added, we started at 25°. Stopped when the annealing mark was in the center of the ground strap. Maybe the answer is to hit it with more timing initially, and start pulling it out once it reaches 4 psi? I believe at wot before it transitions to boost it has 32° in it, and he pulls it right away. I'm thinking about putting 38° in it at that point, but unsure if it would help
 

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Discussion Starter #46
I don't have them
Do you have the old turbos and could you swap with the current plumbing?
I don't have them anymore, I pulled the car apart 3.5 years ago, and they were t3 flange. Im currently t4 flange
 

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Discussion Starter #47
Engine is an engine. If they make similar base power they will make similar numbers on boost. Ls heads are better, so it takes abigger 23 deg head to be more equivalent. At the same boost those turbos should be making the same or similar power regardless of how quickly they spool. Once spooled it shouldnt matter imo. Ar housing i dont think will change peak. It almost seems like they just do not flow
It's not reaching 14 psi until 5800 on the dyno.
 

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Yes
According to brodix it has the same combustion chamber, tuner apparently went up to 29°, but was weird that it didn't gain power for every 2° we added, we started at 25°. Stopped when the annealing mark was in the center of the ground strap. Maybe the answer is to hit it with more timing initially, and start pulling it out once it reaches 4 psi? I believe at wot before it transitions to boost it has 32° in it, and he pulls it right away. I'm thinking about putting 38° in it at that point, but unsure if it would help
keep na timing in it til 4-5 psi
 

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So trying to figure this out, just had the car on the dyno, and the new engine combination is off by 200 hp, at 14 psi from the old combination, and should've made more than the old combination. 383 sbc, twin vs racing 66/67 billet wheel, .84 t4 flange, air to air intercooler, Holley 4500 super sniper (efi throttle body), brodix Dragonslayer heads, 9.2:1 compression, basically the same short block and cam from the old combination. Things that the old combination had: brodix track one heads, cx racing 61 mm/.84 t3 exhaust housings, fitech 1200 pa(and also a qft blow thru 750, power output was within 20 hp between the pair). Power output with the old combination was 820 rwhp, at 15 psi. Power output with new combination, 620 hp, at 14 psi. New combination didn't see full boost until 5800 rpm, old combination was all in by 3500 rpm. Timing on both was set on the dyno starting at 26°, and final timing was 31° on both, using power output and the annealing mark on the ground strap, and using 112 octane. Old combination would gain 40 hp for every 2° put back in it, new combination didn't really see any gains (very minimal) from adding timing, but mark moved on the ground strap with addition of timing. Both engines ran 11.5 on wideband (Holley on one bank, Dyno on other bank, both within.1). Pulled all the plugs, everything is firing, all look normal, no evidence of misfiring. Ignition system is the same, msd pro billet, msd 6 digital programmable (the holley is running the timing, and the msd box has everything zeroed out), new pickup in the distributor, rotor phased, new cap and rotor and wires installed, new coil installed. So far I've also checked spring pressure on the new heads, air tested the system for leaks, verified cam timing, checked compression (160 psi cranking, same as old engine) no blowby out the valve covers, no oil burning, etc. So what gives with this? Sorry for the long post.
Have you looked at the valve seat on your waste gates. Similar situation. Bigger turbo but was loose boost through wastegate valve stems
 

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Keep your timing in till around 4-5 psi, add fuel before you pull timing. Have you played with the fueling to see what it wanted? My twins are pretty close to yours just a hair bigger and when I was on 116 last year I picked up 2 tenths in the 1/8 going from 11.5 to 11.8. Plugs looked good. Maybe try to go .2-.3 both ways and see what it wants. It may want a little bit more fuel with the better heads.
 

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With the numbers you have given you should be needing around 46 lbs/min per turbo to make about 950hp. The turbos you have now are going to flow a fair amount more than that. Try going back to your original turbos and I bet you are going to see the power pick up and the boost come on quite a bit sooner.
 

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My tun
my tuner thinks that the turbos are too big, but they are only 66/67 twins. Viren says that he sells a bunch of them for 5.3's/ls engine, and they light off at 3500. I would think a 383 sbc should be able to use them. I just talked to the dyno operator as well, and said that it's making 14 psi at 5800, so shouldn't the power jump at that point and match at least what I had? He said no, that power on a Dyno just doesn't go up in a straight line, that it's a ramp that builds. But I just don't get how these turbos can work on a 5.3, but not a 383?
I had these turbos on my big bore 347 with .91 housing and it made [email protected]# boost. I did have twins too. I could get 10# on the brake in1.5 seconds and would hit 22# .75 seconds later. There is something wrong with you combo.
 

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I had these turbos on my big bore 347 with .91 housing and it made 7500# boost. I did have twins too. I could get 10# on the brake in1.5 seconds and would hit 22# .75 seconds later. There is something wrong with you combo.
Wow! That's a lot!
 
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