Jneal's truck 71mm cheetah injectors, stock internals
http://www.youtube.com/watch?v=A_dV2fzITiU&feature=channel_page
http://www.youtube.com/watch?v=A_dV2fzITiU&feature=channel_page
Twins vs. Large Single and reliablilty?
- Thread starter Alligator
- Start date
With the right tuning any charger(s) can run 1:1 It still is effected by housings and restrictions IMO
Pat can you expand on the 80% v/s 64% a bit more, not sure I'm following and go ahead and explain the math I'll try and muddle through it. Thanks.
My understanding of the "sweet spot" is when can tune your truck and turbos (twins that is) so the boost and drive pressure increase at or close to a 1to1 ratio. That doesn't necessarly mean you will have the highest boost, in fact I guarantee you won't, but it runs much cooler and overall boost is way more efficient when the drive pressure and boost are similiar.
All air compressors are less than 100% efficient. That means you spend more energy driving them than the energy stored in the compressed air. Where does the "lost" energy go? In a turbocharger, it becomes heat which is passed into the air it's compressing.
The best turbo compressors are 80% efficient, give or take. If you must compress the air twice, it would be 80% x 80% or 64% peak efficiency.
But let's say you want 75psi air. No single compressor we have access to is more than perhaps 50% efficient at that pressure, probably lower. But you could target a compound setup at 75psi and be 64%.
Pat wouldnt the 2nd stage of compression be more efficiant since the charge has already been compressed by the 1st turbo making the 2nd turbo do less effort?
:exactly:
The only way you could be more efficient than the lesser turbo is by the other one being over 100% efficient....which can't happen
Since we are multiplying by less than 1 (.8 for 80%) we will always end up with a lesser number
for thoes who tow with twins and consider there truck streetable how does it work out?? to much heat?? any down falls??
So 64% of 75 pounds is 48 pounds of air so in order to get 48 pounds of air out of a single that is 80% efficient, you only have to make 60 pounds of boost.
I can reasonably understand why twins are quicker but not faster in the 1/4 mile. It depends on the maps obviously. But if I understand right at the same amount of air PSI, the single is more efficient and "should" put down the bigger number hp wise, but the twin will have more boost available at a given lower rpm. Now how to calculate the maps when you twin things. I wish I was smarter.
I can reasonably understand why twins are quicker but not faster in the 1/4 mile. It depends on the maps obviously. But if I understand right at the same amount of air PSI, the single is more efficient and "should" put down the bigger number hp wise, but the twin will have more boost available at a given lower rpm. Now how to calculate the maps when you twin things. I wish I was smarter.
So 64% of 75 pounds is 48 pounds of air so in order to get 48 pounds of air out of a single that is 80% efficient, you only have to make 60 pounds of boost.
I can reasonably understand why twins are quicker but not faster in the 1/4 mile. It depends on the maps obviously. But if I understand right at the same amount of air PSI, the single is more efficient and "should" put down the bigger number hp wise, but the twin will have more boost available at a given lower rpm. Now how to calculate the maps when you twin things. I wish I was smarter.
Effiency % is not directly related to PSI but rather to energy
To simplify it. You want you low pressure turbo to flow about 1 1/2 to 2 times as much air as your high pressure one. There is a lot of room for error and waste gates allow you to to be even further off with your turbo selection. If your low pressure turbo is too small you can just open up the gate on that turbo. If the high pressure turbo is too small and over spinning you can open up the gate on that one. Altho to large of a low pressure turbo will cause it to be laggy. (you will lite your high pressure one and then have to contine to work on liting the low pressure one) Also remember to work with PSIA when doing math and then subtract 15 for the actual boost after all math is done
If you put 15PSI out of your low pressure turbo (2:1 p/r) that is 30PSIA Then run your high pressure turbo at a 2:1 p/r and you will have 60PSIA. Then subtact 15 to convert PSIA to PSI of boost and you end up with 45 PSI while running both turbos at a very low p/r to keep them much closer to their "sweet spot" To make 45PSI with a single you would have to run the turbo at a 4:1 p/r 15X4=60PSIA -15=45PSI of boost
Comments are just makin me excited and about to make me want to call MPI
Just do it! You wont regret it.
I would but my right foot tends to get heavy and I dont have the cash for an engine build....... and dunno if I have the restraint to detune lol. I may live vicariously through you for a few more months hahaha.
I take it you are loving yours so far?