Why so much timing with my Blown LS3?
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On The Tree
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Why so much timing with my Blown LS3? Alright ive asked this question to so many people lately and still cant get a good answer. I have an LS3 with a Maggie on top that is taking 28* of timing running URT. What makes the engine take this much timing and only make 650rwhp? I have a 9.5:1 CR and the cam numbers are (215/247 .629/.656 121 CL
Any help understanding this would be appreciated
Any help understanding this would be appreciated
RWHP is respectable. However, with that much exhaust duration combined with a 121° LSA, your dynamic compression ratio is prolly in the 7's. With a DCR that low, it'll take more timing, not to mention you're leaving a lot on the table.
Thats about rite, i used 27 degrees @ 20psi on pump gas running straight methanol injection, made 880 whp and 941 rwt on my previous build with pro charger d1sc 9" bottom pulley and 4" top, with a 402 stroker using the same compresion
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On The Tree
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Just seems high to me and im trying not to tear it up. I guess i could start looking at the end of the plugs after each run to try and see exactly whats going on. Im hitting a wall with this engine and power and at this point have an idea on which way to go, but not 100% confident in it. New cam, heads and maybe a 102 TB and i should break out some more power, but im not sure that will give me much more or where i want to be. Also i know heat soak is killing this positive displacement, so thats another thing ive got to tackle in order to keep the power to the ground.
Intake duration and ICL determine DCR.
28* is IMO way to much for a boosted motor even on race gas especially a power adder like a roots that pretty much super heats the intake air coming into the motor.
I'd be around 18*-20* on race gas with a set-up like that and 12-14* on pump gas.
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On The Tree
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Cam Specs are: 215/247 .629/.656 121 CL
IMO its way too much also, but why is it taking so much is what i dont understand. What can be done to lower it without losing power? When its set at 18-21 the car just doesnt make the power
IMO its way too much also, but why is it taking so much is what i dont understand. What can be done to lower it without losing power? When its set at 18-21 the car just doesnt make the power
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No I didn't, I'll go back and do some more research though. Doesn't make any sense, if you were to leave the exhaust valve off the seat completely, there would zero compression, so it must figure in somehow. Anyway, I see it's not an inputted "spec" in the calculators...
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Verdad Gallardo But the intake valve close event has everything to do with compression.
The compression stroke happens when the intake valve is closing. When and where that intake valve closes determines how much pressure is captured in the combustion event. Adding intake duration makes the intake valve close later thus reducing DCR and reducing intake duration makes it close earlier thus trapping more cylinder pressure in the cylinder earlier as the piston rises up in the bore on the compression stroke.
When you advance or retard the ICL it advances or retards that IVC event along with all the other valve events.
Exhaust valve open and close happen after the compression stroke therefore not having any effect on compression.
Hope that makes sense.
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On The Tree
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Yes sir you are correct. I will try and find out what the ICL is on this cam, but do you think having this cam is keeping me from gaining power after adding so much timing?
Launching!
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From: CAIRNS QLD AUST
Wow, that cam is going to want to push the motor to 7200. 5800-7200 is where it pulls best last time I ran a cam like it in a KB boosted 2010 Camaro. Power is in your blower, Pulley it, cog it, port it, Big MAF, Big TB. The same cam on a 115 LSA +2 would do much better. Methanol injection is always a plus with a roots....
I would advance it at least 4 degrees if not closer to 6 degrees.
And yes if it were on a 116+3 I would like the valve events much better.
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From: Norn Iron
If the ICL is 121 straight up with the 121 lsa then yes it is KILLING every bit of cylinder pressure that the 215 intake lobe would give you.
I would advance it at least 4 degrees if not closer to 6 degrees.
And yes if it were on a 116+3 I would like the valve events much better.
I would advance it at least 4 degrees if not closer to 6 degrees.
And yes if it were on a 116+3 I would like the valve events much better.
Just interested as I have the GT9 in mine now
I certainly cant throw timing at mine like this guy is doing though.
I'd almost query if the numbers he is quoting are correct, and they should be verified with a timing light.
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From: Norn Iron
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On The Tree
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Ive given the cam specs to multiple engine builders and all say ditch the cam and go for a more specific one for my build instead of an "off the shelf" one. It may not be the exact problem, but it still needs to be changed in my opinion
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From: Norn Iron
GT9 cam works great. Given the number of profiles available for the LS platform, all profiles can be considered "off the shelf".
But it would take an incredibly bad profile to no produce results in an LS. The GT9 is a good camshaft and has been proven in different engines. I'm certainly very pleased with it in mine.
It idles super smooth, it revs and makes good power.
Maybe try a different tuner, and as said, verify 100% the timing you think you have, you are actually seeing at the plug.
But it would take an incredibly bad profile to no produce results in an LS. The GT9 is a good camshaft and has been proven in different engines. I'm certainly very pleased with it in mine.
It idles super smooth, it revs and makes good power.
Maybe try a different tuner, and as said, verify 100% the timing you think you have, you are actually seeing at the plug.