jdgleason
Active member
Basically, there is a point where a turbo can only push so much air, no matter how hard its driven. The map refers to those pressures and ratios... I think lol
someone should try it
- Thread starter Dzchey21
- Start date
Basically, there is a point where a turbo can only push so much air, no matter how hard its driven. The map refers to those pressures and ratios... I think lol
Erikclaw
Active member
So basically keeping it in its efficiency range?
Powerstroke Cowboy
Well-known member
No it should not.. thit is air density and volume that you get from air being compressed. The bigger turbo flow a certian amount of CFM at a certian amount of PSI. (Well they should.) So if you take a Bigger turbo and feed the smaller factory turbos you are getting more air density and that means more oxygen in the same space.
its hard to for me to put into words, what i have in my head, sorry!!!
Erikclaw
Active member
So you are basically compressing the air twice and making more dense. So at the same CFM if the air is more dense you are theoretically flowing more air but not needing a bigger opening to flow it through.
Powerstroke Cowboy
Well-known member
Yes it does. But with the bigger turbo you could make the same amount of boost. But have more air and oxygen so it will burn cooler.
But with the second (eerrr third
) turbo you will keep the factory turbos like dustin said in there intended MAP. When a turbo goes out of it intended range it will superheat the air. So if you can keep them in there range AND feed them with another turbo, you should be better off..
JAP
In the Brig (Banned)
Yeah, my idea sucks. LOL That would never work.
Powerstroke Cowboy
Well-known member
Almost....
whae you feed the smaller turbo with a bigger turbo you compressing the air going to the smaller turbo. so the air going to the smaller turbo is more dense, and has more oxygen in it. Then the smaller one compresses it more so it is even more dense and has a even higher oxygen level. You are not realy moving any more CFM to the engine, you are just feeding denser air that is packed with more oxygen..
the engine can only take so much air per cycle. so you would not be moving more air just densor air with more oxygen in it..
jdgleason
Active member
Exactly right?
Erikclaw
Active member
That is what I was thinking, just didn't express it well.
Your thinking about it wrong i think.
As a single turbo trying to make 50psi of boost.
14.7 absolute + 50 psi of boost = 64.7/14.7= a pressure ratio of 4.40
look at this compressor map, note that 4.40 puts the pressure ratio very high on the map, if not out of the map completely
I used this map for an example because its a similar compressor map to a stock low pressure turbo
Now high altitude people... it only gets worse
11.7 absolute ( 6000ft) + 50 psi of boost = 61.7/11.7= 5.27 pressure ratio!!! thats way out of the map
Now if you take that same truck making 50 psi of boost, and say make the low pressure make 30 psi of the total boost you have now made the pressure ratio much better
14.7+30psi of boost= 44.7/14.7= 3.04 PR alot better in the map, and you are still able to make 50 psi of total boost which is needed to make x amount of hp,
The high pressure is now being fed 44.7 absolute pressure into the inlet of the turbo, outlet pressure is say 50 psi total
44.7+20=66.7 since the pressure going in is 44.7 you divide it by that number so your pressure ratio is 1.44 which is way low, in most cases low pressure boost is probably half of total boost so the numbers will actually be closer to each other, say 2.5pr each turbo, i know this is gunna get confusing, charles is much better at explaining it
DO the same with tripple compounds, and it only gets better because the required amount of boost from each turbo goes down, say even at 50 psi of boost
jdgleason
Active member
See without the bigger opening though is where I think heat would come into play... its a fine line
Powerstroke Cowboy
Well-known member
Yeah, my idea sucks. LOL That would never work.
complicated mess aint it!!! LOL
If i remember right. the smaller turbo cuts out after a certian PSI and the bigger one takes over??
Correct me if i am wrong here dustin..
jdgleason
Active member
Ok... its getting clearer. I guess I am just not 100% certain on where the stockers would be at that point. Seeing that map and following the math really helped. Thanks.
jdgleason
Active member
What do you mean by cuts out?
Na, basically the computer wants to see a certain amount of drive pressure, the vanes close in the turbo making more back pressure and boost from the high pressure turbo, once the pressure rises the vanes open and more of the exhaust energy is diverted to the low pressure, basically just kicks the high pressure in faster to get things moving first, once things get moving the exhaust is a little more free flowing.
the problem is there is no maps for the stock turbos, but i can tell you if a stock truck only hits 32 psi of boost, the stock turbos really arent working hard at that level
Since the stock turbos dont have a map enhancment groove i bet the pressure ratio capability for the stock turbos isnt all that great, i bet 3.0 is pretty high for stock turbos, so 50psi of boost probably has both turbos working on the edge of the map, or out of the map, and that tiny little 3 inch inlet on the stock turbo is just begging for air to be forced into it LOL
Erikclaw
Active member
Your thinking about it wrong i think.
As a single turbo trying to make 50psi of boost.
14.7 absolute + 50 psi of boost = 64.7/14.7= a pressure ratio of 4.40
look at this compressor map, note that 4.40 puts the pressure ratio very high on the map, if not out of the map completely
I used this map for an example because its a similar compressor map to a stock low pressure turbo
Now high altitude people... it only gets worse
11.7 absolute ( 6000ft) + 50 psi of boost = 61.7/11.7= 5.27 pressure ratio!!! thats way out of the map
Now if you take that same truck making 50 psi of boost, and say make the low pressure make 30 psi of the total boost you have now made the pressure ratio much better
14.7+30psi of boost= 44.7/14.7= 3.04 PR alot better in the map, and you are still able to make 50 psi of total boost which is needed to make x amount of hp,
The high pressure is now being fed 44.7 absolute pressure into the inlet of the turbo, outlet pressure is say 50 psi total
44.7+20=66.7 since the pressure going in is 44.7 you divide it by that number so your pressure ratio is 1.44 which is way low, in most cases low pressure boost is probably half of total boost so the numbers will actually be closer to each other, say 2.5pr each turbo, i know this is gunna get confusing, charles is much better at explaining it
DO the same with tripple compounds, and it only gets better because the required amount of boost from each turbo goes down, say even at 50 psi of boost
So am I correct in assuming that the bigger atmospheric would say make 30psi of the total of 50psi and the smaller stock turbos would make the other 20psi? So that way all turbos are with in the map and you could make a higher total boost # but keeping everything within the map of each turbo?
Powerstroke Cowboy
Well-known member
I Think I said that wrong. the little turbo is feed by the bigger one. BUT after a certian point when the bigger turbo hit a certian amount of boost it skips the smaller one and blow right to the engine..
Correct me if i am wrong please dustin
I think I am all wet LOL
I should have kept my mouth closed..
Thats the thing is it probably wouldnt continue to make 50 psi of total boost, (almost impossible to gate it that low i bet) so now you would be talking in the neighborhood of 75 psi, keep in mind this type of tripple turbo set up would be more geared for people needed to make big boost numbers to make power, a good flowing set of twins may only require say 65 psi to accomplish the same thing, but for a guy running bone stock heads with valve springs and push rods, this may be the way to get that extra air in the engine
jdgleason
Active member
Lol im sure thats not how it was designed haha but hey! I get what you mean though, I think I may be underestimating flow through the stockers.
Thats the idea, and how most try to model turbo setups.
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