Tuning Twins

SHughes said:
what are yo trying to accomplish? sounds like a really great tow rig for all those gassers you have. :Cheer:
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Tow slash fun dd. Wanting a solid 550 to 650 that's dd, tow, fun. I am almost there just need a tad bigger injector.

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so what's you question??

sorry, went back a read it again. I think I would just worry about drive pressure, it doesn't seem like you would have any problems unless you really push it too hard. But witha DP gauge you can see if you need to open the wastegate to keep DP in check, you clearly have EGT's under control (same while towing ??)
 
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SHughes said:
so what's you question??

sorry, went back a read it again. I think I would just worry about drive pressure, it doesn't seem like you would have any problems unless you really push it too hard. But witha DP gauge you can see if you need to open the wastegate to keep DP in check, you clearly have EGT's under control (same while towing ??)
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Yes they are the same while towing. I will have the dp gauge shortly and will know after that.

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Big Blue24 said:
In my opinion, a 71mm Aurora 5000 primary is not " a lot larger" than a 60mm He351 secondary.

I'm running an HT4B 83mm primary with my He351 60mm secondary. I'm still tuning but last night during a really, really short highway WOT run, 75psi total, 55psi in the cold pipe between the HT4B and He351 inlet.... I'd say the ported factory wastegate is bypassing plenty of exhaust drive pressure..... I'm still tuning-in the gate but the plan is to get total boost in the 85 psi range with 50psi coming from the HT4B and then the He351 stepping it up to 85 psi at the intake manifold. I know it's not a lot of pressure ratio for the secondary He351, but with the dense air charge coming from the HT4B, I don't want to overwork it to where it's prone to failure.
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I will remove the "A Lot Larger" verbiage.. :poke: I thought the HE351 is 58mm?
 
ok finally got some gauges on. everything is hooked up but the drive pressure. gotta get a filter first. this is what its running boost wise right now and you guys tell me what you think

manifold boost = 65 psi
primary boost = 28 psi
secondary boost = ?
presure ratio = ?

wastegate is completly pinched shut so wastegate is not opening at all yet the primary is still making almost 30?
 
also, how are you guys calculating the psi of the secondary charger? having a brain fart right now. i am seeing 28 from the cold pipe in between chargers and 65 total at the manifold. how do i calculate the boost the secondary is making?
 
so taking the math from the first post of this thread. i am getting

primary pressure ratio of 2.90
secondary pressure ratio of 1.86


is this telling me the primary is doing all the work or the secondary is doing all the work.
 
inline6power said:
also, how are you guys calculating the psi of the secondary charger? having a brain fart right now. i am seeing 28 from the cold pipe in between chargers and 65 total at the manifold. how do i calculate the boost the secondary is making?
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Well if you have 65 total and 28 is coming from the primary then the secondary must be making 65-28 = 37. Right?
 
I would also set the wastegate to keep the secondary at 30-35. I mean 37 is not too bad, but as soon as you get bigger injectors it will change. What do you think?
 
Well I think you may be wrong. Look at the first post of the thread. Primary making 20psi and total at 77. No way his secondary is making 57psi and pressure ratios are the same at 2.6

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inline6power said:
so taking the math from the first post of this thread. i am getting

primary pressure ratio of 2.90
secondary pressure ratio of 1.86


is this telling me the primary is doing all the work or the secondary is doing all the work.
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means your small charger would be making around 12 psi if it was compounding the atmosphere. at around 3200 your asking it to flow a whopping 544 cfm or around 37 lbs per minute,(assuming 80% VE, ) I didn't read back to see what small turbo you are running but you could get away with smaller than stock with those pressures, well at least on the compressor side.

In my opinion the primary is right where is should be, need to spin the little guy faster.
 
gs1000 said:
means your small charger would be making around 12 psi if it was compounding the atmosphere. at around 3200 your asking it to flow a whopping 544 cfm or around 37 lbs per minute,(assuming 80% VE, ) I didn't read back to see what small turbo you are running but you could get away with smaller than stock with those pressures, well at least on the compressor side.

In my opinion the primary is right where is should be, need to spin the little guy faster.
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How can I spin the secondary harder if i already have the wastegate completely shut?


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smaller turbine housing? smaller turbo, more fuel?

seems crazy to me that your secondary's contribution is so small with no wastegating around it.
 
gs1000 said:
smaller turbine housing? smaller turbo, more fuel?

seems crazy to me that your secondary's contribution is so small with no wastegating around it.
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I agree. I have a pair of vice grips that are completely pinching the wastegate line off yet the primary is still doing alot of the eork. Unless those stupid brass pop offs are not working and they are relieving pressure

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inline6power said:
I agree. I have a pair of vice grips that are completely pinching the wastegate line off yet the primary is still doing alot of the eork. Unless those stupid brass pop offs are not working and they are relieving pressure

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ok then, so it is internally gated, yes? if so the spring holding the wastegate closed is most likely set for much lower drive pressure then it is seeing with compounds and drive pressure alone is opening up that wastegate.

at least that is my opinion.

when you say pop offs do you mean like blow off valves, if so I would get rid of those at least temporarily for testing.
 
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gs1000 said:
ok then, so it is internally gated, yes? if so the spring holding the wastegate closed is most likely set for much lower drive pressure then it is seeing with compounds and drive pressure alone is opening up that wastegate.

at least that is my opinion.

when you say pop offs do you mean like blow off valves, if so I would get rid of those at least temporarily for testing.
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Yeah its those brass blow off valves that come in the kit that go in the intercooler charge pipe. Yes top turbo is internally gated. Just not sure what to try from this point

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You are essentially at sea level so we will use 14.7psi as atmospheric pressure.

To figure out how much work each charger is doing, you need to convert to pressure ratio's first. So the formula is (atmospheric pressure + gauge pressure) / atmospheric pressure

65psi gauge overall boost is = (14.7+65psi)/14.7 = ~5.42
28psi gauge primary boost is = (14.7+28psi)/14.7 = ~2.91

So we now divide overall PR by primary PR, and then convert back
5.42 / 2.91 = 1.86

Secondary PR = ~1.86PR So using the above formula just in reverse
1.86 * 14.7 - 14.7 = 12.68psi so call it 13psi.

So currently your primary charger is doing more work then your secondary. This could happen do to a number of things, as was suggested the two things to try if you are worried about it, would be:

-Take out those silly brass pop off valves, all they do is cause boost leaks that over speed chargers.

-Mechanically tie the gate closed on the secondary, to make sure drive pressure isn't blowing it open.
 
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