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  1. #51
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    1 out of 1 members liked this post. Yes Reputation No
    Click here to enlarge Originally Posted by rudypoochris Click here to enlarge
    Turbo speed goes up with more boost, better intercooler, and the use of meth. Basically anything that reduces pressure drop, increases boost, or increase charge density after the turbo will result in more turbo speed since the turbo now has to fulfill more air mass. So better intercooler is harder on the turbos.
    I have to disagree. A centri compressor is a like a voltage source, if you reduce the resistance in the circuit, the circuit will require less voltage to produce the same current. The use of meth before the compressor will reduce rotor speed because it causes the turbo to 'feel' dense air and hence only needs to produce a lower pressure ratio to obtain the same boost level.

    A lower pressure drop intercooler will result in lower turbine speed.

    Anything that reduces pressure drop will reduce turbine speed.

    Increasing boost but nothing else, will increase turbine speed though, so that is correct.
    Last edited by DBFIU; 12-01-2012 at 04:39 PM.
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  2. #52
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    Click here to enlarge Originally Posted by DBFIU Click here to enlarge
    I have to disagree. A centri compressor is a like a voltage source, if you reduce the resistance in the circuit, the circuit will require less voltage to produce the same current. The use of meth before the compressor will reduce rotor speed because it causes the turbo to 'feel' dense air and hence only needs to produce a lower pressure ratio to obtain the same boost level.

    A lower pressure drop intercooler will result in lower turbine speed.

    Anything that reduces pressure drop will reduce turbine speed.

    Increasing boost but nothing else, will increase turbine speed though, so that is correct.
    Sorry I meant temperature drop from better intercooler. Lower backpressure from the intercooler is a good thing, but typically the higher temp drop negates the benefit which can be seen by increased PWM after upgrading the IC. As far as meth goes, I was referring to its use in its standard application on this platform. 99% of people use meth post turbo here which means turbo load will go up to hit the same boost target. You know this is how people are using it the vast majority of the time here, my post was written in the context of this platform and how people are using these systems. That is to say the use of meth POST IC (like 99% of people here using meth run it) drives up turbo speed. Is that better???

  3. #53
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    Click here to enlarge Originally Posted by DBFIU Click here to enlarge
    Blades touching housings can occur even when there is no overspeed, due to imbalance, FOD, oil starvation etc... So it is hard to say what exactly caused that, it may be overspeed or it may not.

    You cant say with all certainty that if the blades touched the housings that it was overspeed, many things can cause that. If you have data logs of the failure event, maybe we can know more about this failure.
    You're doing it again. This information is from the manufacture and depicts failures caused by overspeed. Can these types of failures be caused by other things such as defects and improper handling, YES. Were they in this case, NO. I don't get what's so difficult about this. Could these issues be caused by overspeed? If yes, and the manufacturer stated this as the reason, what basis are you doubting this on? This is no different than a timing belt manufacturer showing snapped timing belts that failed from not being changed regularly. Could the timing belt have snapped due to some other reason: sure, did it: no. This is altogether a pointless argument, failures can happen for different reasons, the point is that these failures can be and are in this case a direct result of overspeed.

  4. #54
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    Click here to enlarge Originally Posted by E90Company Click here to enlarge
    Depends on your RPM. 20psi at 3000 is wayy different than 20psi at 6000
    Yes to the engine they are very different, to the turbo, engine RPM is (for lack of a huge discussion) moot once the turbo has been spooled, the wastegate controlled by the DME or otherwise keeps the shaft speed in check by bypassing exhaust gasses around the turbine to keep it the proper speed / boost. The turbo is seeing extra heat at higher RPM's but as far as overspeed, you can overspeed a turbo just as easily at 4000 RPM as you can at 6000 RPM if the wastegate is not bypassing enough exhaust gasses to slow the wheel, ie boost is set too high. The notion that boost is tapered to save the tubo's is not correct, its tapered because the high compression N54 engine can't handle all that boost as power builds in stock form, its done to keep the DME from pulling timing as it nears a knock condition aka getting ready to break something.

  5. #55
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    Click here to enlarge Originally Posted by rudypoochris Click here to enlarge
    Turbo speed goes up with more boost, better intercooler, and the use of meth. Basically anything that reduces pressure drop, increases boost, or increase charge density after the turbo will result in more turbo speed since the turbo now has to fulfill more air mass. So better intercooler is harder on the turbos.
    I guess I've been thinking about this incorrectly. I was thinking a better intercooler would make things easier on turbos. Reason being is if you have inefficient intercooler, you would have a higher pressure drop through it. So running a tune at 16psi with 2 psi pressure drop through the intercooler would result in a net of 14 psi boost. A more efficient intercooler design with say .5 psi pressure drop could run lower boost overall (14.5 psi) and net the same power. Is my thinking incorrect?

  6. #56
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    Click here to enlarge Originally Posted by VargasTurboTech Click here to enlarge
    Yes to the engine they are very different, to the turbo, engine RPM is (for lack of a huge discussion) moot once the turbo has been spooled, the wastegate controlled by the DME or otherwise keeps the shaft speed in check by bypassing exhaust gasses around the turbine to keep it the proper speed / boost. The turbo is seeing extra heat at higher RPM's but as far as overspeed, you can overspeed a turbo just as easily at 4000 RPM as you can at 6000 RPM if the wastegate is not bypassing enough exhaust gasses to slow the wheel, ie boost is set too high. The notion that boost is tapered to save the tubo's is not correct, its tapered because the high compression N54 engine can't handle all that boost as power builds in stock form, its done to keep the DME from pulling timing as it nears a knock condition aka getting ready to break something.
    Its kind of both actually. With E85 and meth you are no longer octane limited. That is to say you can run much more boost without knocking. In this case the boost is curtailed up top to reduce the amount of flow they need to generate. The stock turbos simply cannot generate 22psi at the flow rate demanded by 7000rpms where as they can at 4000rpm. They will be spinning to fast and the flow will be choked. In the typical case of 91 or 93 octane only, you are correct, boost is lowered so that timing is not affected.

  7. #57
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    Click here to enlarge Originally Posted by eric84405 Click here to enlarge
    I guess I've been thinking about this incorrectly. I was thinking a better intercooler would make things easier on turbos. Reason being is if you have inefficient intercooler, you would have a higher pressure drop through it. So running a tune at 16psi with 2 psi pressure drop through the intercooler would result in a net of 14 psi boost. A more efficient intercooler design with say .5 psi pressure drop could run lower boost overall (14.5 psi) and net the same power. Is my thinking incorrect?
    You are correct.
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  8. #58
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    Click here to enlarge Originally Posted by eric84405 Click here to enlarge
    I guess I've been thinking about this incorrectly. I was thinking a better intercooler would make things easier on turbos. Reason being is if you have inefficient intercooler, you would have a higher pressure drop through it. So running a tune at 16psi with 2 psi pressure drop through the intercooler would result in a net of 14 psi boost. A more efficient intercooler design with say .5 psi pressure drop could run lower boost overall (14.5 psi) and net the same power. Is my thinking incorrect?
    Your thinking is correct, but I cant confirm specific boost numbers since it will vary. I too was thinking about it the way you were when I got my intercooler. Lower pressure drop means easier on turbos. The reality is that by the end of 3rd on the stock IC I was seeing 40F+ above ambient. Now I see 5F over ambient. So while my pressure drop may have gone down a psi or two, the volume of air the turbos need to supply went up significantly. Further more, that volume has pushed the turbos even farther off the edge of the map, which is a slippery slope. Long story short the better intercooler does make 20whp more at the same boost target, but it also drove WGDC up. Could you turn boost down by some amount and get your original HP with slightly less WGDC or better? Yes probably, but that is a tricky one since at lower RPM the stock IC heat soak wasn't as bad as at high RPM. You'd have to adjust the boost curve essentially.

  9. #59
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    Click here to enlarge Originally Posted by DBFIU Click here to enlarge
    You are correct.
    I will be joining you on the preturbo meth bandwagon btw. Click here to enlarge I want to see what I an coax out of these stock turbos without increasing shaft speed (I will start by monitoring WGDC, but I may have to get a turbine out temp reading to approximate it).

  10. #60
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    Thanks for the info, I have much to learn! I had not considered WGDC would go up. I was thinking with less heat soak and cooler air being denser that there were essentially no downsides. As usual, there is no free lunch!

  11. #61
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    Click here to enlarge Originally Posted by rudypoochris Click here to enlarge
    Its kind of both actually. With E85 and meth you are no longer octane limited. That is to say you can run much more boost without knocking. In this case the boost is curtailed up top to reduce the amount of flow they need to generate. The stock turbos simply cannot generate 22psi at the flow rate demanded by 7000rpms where as they can at 4000rpm. They will be spinning to fast and the flow will be choked. In the typical case of 91 or 93 octane only, you are correct, boost is lowered so that timing is not affected.
    Agree 100%, if we are talking flow rates and not just strictly RPM of the turbocharger then yes, I see both sides.

  12. #62
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    Click here to enlarge Originally Posted by nitehawk Click here to enlarge
    Does it make sense that turbos spin less with cooler temps to hit the same level of boost, due to the denser air mass? Hitting 22psi in 90F ambient would require a higher WGDC (making them spin faster) compared to when it is 32F outside right? Just thinking out loud here...
    Click here to enlarge Originally Posted by DBFIU Click here to enlarge
    Yes that is exactly right. If you look at the compressor map, the x axis is corrected flow which is non-dimensional mass flow (takes out ambient temperature from the equation).

    So playing with inlet temps is huge for compressor efficiency and mass flow.

    Think of it like this, lets say you built a compressor shaped exactly like the stock N54, and you could theoretically spin it to 300k RPM without it exploding, would it flow more? The answer is no, there is a limit to the mass flow, and it is geometrically constrained because of the compressor and scroll, eventually, you just cannot move more air no matter how fast you spin it.

    So keeping rotor speed down is always always a plus, and that can be done by various means, pre turbo meth and lowering ambient temps being one way...
    Hmmm, I think looking at the compressor map higher mass flow (lower temp) at same PR would result in faster turbo speed. BUT with lower temp ambient pressure increases, lowering PR. And I believe more dense fluid increases efficiency... air "sticks" (tech term) to the blades better.

  13. #63
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    Click here to enlarge Originally Posted by rudypoochris Click here to enlarge
    I will be joining you on the preturbo meth bandwagon btw. Click here to enlarge I want to see what I an coax out of these stock turbos without increasing shaft speed (I will start by monitoring WGDC, but I may have to get a turbine out temp reading to approximate it).
    pre turbo meth was the best mod i ever did to the car, you can actually see WGDC go down drastically which means turbine speed is reduced. Try using the mcmaster M1 nozzles first, mount them in the filters, I have a thread floating around somewhere with pictures, just be sure you reach full atomization before the compressor or else, you know what happens.
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  14. #64
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    Click here to enlarge Originally Posted by DBFIU Click here to enlarge
    pre turbo meth was the best mod i ever did to the car, you can actually see WGDC go down drastically which means turbine speed is reduced. Try using the mcmaster M1 nozzles first, mount them in the filters, I have a thread floating around somewhere with pictures, just be sure you reach full atomization before the compressor or else, you know what happens.
    I have been reading a lot and have seen your setup. I am going with a 50-50 mix and two CM5s (300cc/min each). I will be running no post turbo meth since I calculated this flow to be about the max ideal for this engine. After a baseline I can experiment with diff nozzles. I suspect 50-50 is the way to go since yes, it will make for worse atomization, but it will allow for more volume since meth and water reach max saturation points independently. I am sure I will hit you up with Qs once data rolls in.

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    Click here to enlarge Originally Posted by DBFIU Click here to enlarge
    pre turbo meth was the best mod i ever did to the car, you can actually see WGDC go down drastically which means turbine speed is reduced. Try using the mcmaster M1 nozzles first, mount them in the filters, I have a thread floating around somewhere with pictures, just be sure you reach full atomization before the compressor or else, you know what happens.
    I cant find the M1 nozzles on McMaster. I did find fogging and misting nozzles though. What do you think of the CM nozzles? Did you do any research into which one is better?

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