boost is boost? turbos compare

[cjridert1]

Looking into getting a 50 trim, but probably will only be pushing ~20psi. I have a 16g now that pushes this - is there any advantage to running a 50/20g outside of not overrunning its efficiency and heating up the intake air? lbs/min would still be the same for 20psi or not?

Thanks guys

 

[gob4sho89]

...I put on an AGP L2R turbo on my car and changed nothing else, and was pulling harder at 10psi then I was at 18psi falling off to 16psi on my t25... I did not even touch my tune... Boost is definatly not boost.........

 

[Twistaye]

Okay, I think what he's saying is that:
If a B16G is holding 20 PSI steadily with X amount of heat/efficiency
Then won't a 20G with X (the same) amount of heat/efficiency flow the same amount of air at 20 PSI?

I personally don't think so, a 20G turbine is larger than a 16G turbine, now this increased diameter will increase the amount of air that can flow. At 20 PSI the 20G will flow more air, now what I think he's saying is that if the 20g didn't flow more "efficiently/cooler" wouldn't the air flow be the same? I get what you're saying, but I don't think so. The 20G will continue to flow more air than a 16g even at the same temps/efficiency because the 20g will be more efficient regardless due to the fact that it has a larger turbine and it's packing more air into the cylinders because it can suck more air.

Now, when stating that, it seems that the efficiency is better, so if the efficiency was the same, they would theoretically flow the same amount of air. Which I can see, but it doesn't justify a larger turbo pulling the same amount of air as a smaller turbo at the same PSI due to the fact that the larger turbo can pull that much more air in. Say a B16G is pulling 40LB/Min @ 20 PSI and a 20G is pulling 45 LB/Min at 20 PSI, it's still pulling 5LB/Min more than the B16G (but is this because it's more efficient/has more condensed air?).

Okay, after confusing myself horribly I think I understand what he's saying.. If a larger turbo (i.e. 20G) isn't flowing more efficient (condensing the air) then couldn't a B16G flow the same amount of air at the same PSI? I would say no, because the fact is the 20G is going to be more efficient because it can pull that much more air in at once. So at 10 PSI you could get the same amount of air flow as a B16G at 16 psi. So I don't think boost is just boost.. (Note, all the numbers in this are theoretical and not based on any facts or numbers that I pulled, but if you want me to go further in depth I'm sure I can look at some charts and pull out some numbers)

Sorry if I'm confusing anyone, or if I'm totally wrong, it sounded good in my head^^. Hope it helps, if not then just ignore me !

 

[Black_Bullet]

Okay, I think what he's saying is that:
If a B16G is holding 20 PSI steadily with X amount of heat/efficiency
Then won't a 20G with X (the same) amount of heat/efficiency flow the same amount of air at 20 PSI?

I personally don't think so, a 20G turbine is larger than a 16G turbine, now this increased diameter will increase the amount of air that can flow. At 20 PSI the 20G will flow more air, now what I think he's saying is that if the 20g didn't flow more "efficiently/cooler" wouldn't the air flow be the same? I get what you're saying, but I don't think so. The 20G will continue to flow more air than a 16g even at the same temps/efficiency because the 20g will be more efficient regardless due to the fact that it has a larger turbine and it's packing more air into the cylinders because it can suck more air.

Now, when stating that, it seems that the efficiency is better, so if the efficiency was the same, they would theoretically flow the same amount of air. Which I can see, but it doesn't justify a larger turbo pulling the same amount of air as a smaller turbo at the same PSI due to the fact that the larger turbo can pull that much more air in. Say a B16G is pulling 40LB/Min @ 20 PSI and a 20G is pulling 45 LB/Min at 20 PSI, it's still pulling 5LB/Min more than the B16G (but is this because it's more efficient/has more condensed air?).

Okay, after confusing myself horribly I think I understand what he's saying.. If a larger turbo (i.e. 20G) isn't flowing more efficient (condensing the air) then couldn't a B16G flow the same amount of air at the same PSI? I would say no, because the fact is the 20G is going to be more efficient because it can pull that much more air in at once. So at 10 PSI you could get the same amount of air flow as a B16G at 16 psi. So I don't think boost is just boost.. (Note, all the numbers in this are theoretical and not based on any facts or numbers that I pulled, but if you want me to go further in depth I'm sure I can look at some charts and pull out some numbers)

Sorry if I'm confusing anyone, or if I'm totally wrong, it sounded good in my head^^. Hope it helps, if not then just ignore me !

I can see where this would make sense , but like i said, the gain in air flow from a bigger turbo is when you are running higher boost levels at higher rpms.

If only 20 psi truely is the set goal for the OP then a EVO316g will be fine, plus youd have faster spool up.

A bigger turbo would more so help someone like me; with a pressure drop before i even hit 6500 rpms while having the power band of aftermarket camshafts.. Meaning im already running up against the flow limits of my turbo ( e316g) ; and putting a bigger turbo would dramatically improve my boost holding to redline to really use my powerband. But if i werent running as much boost ( currently seeing 23-25psi) then i wouldnt find it worth it to spend the money for anything larger than what i have if say i only wanted 20 psi and under.

Cooler air temps allowing more aggressive timing adv or leaner AFRs is the main reason a slightly bigger turbo
taken thru the same power band, could produce more power than the smaller turbo could at only 20psi...

If you look at a lot of dyno graphs, at a low psi like that, the bigger 50trim, or 20g or whatever were comparing with, though it will make a tad bit more power up top, there could definitly be a lot of torque lose down low when coming from a evo316g.

You have to weigh cost, and worth, and what your car will be used for.
Bigger turbos only shine in high rpm at high boost period....

 

[bastarddsm]

generally speakin boost is boost. but there are limitations gob4sho is an example. however refering to the original poster, replacing a 16g with a 50trim will not net him any appriciable power gains, all else being equal. if i had less important things to do after work, i would calculate it out. in the mean time i suggest you read up on how to properly size a turbo, and we'll talk.

 

[Twistaye]

I can see where this would make sense , but like i said, the gain in air flow from a bigger turbo is when you are running higher boost levels at higher rpms.

If 20 psi truely is the set goal for the OP then a 16g will be fine, plus youd have faster spool up.

A bigger turbo would more so help someone like me running enough boost (23-25psi)
that when i approach 6500 rpms; i see a dramatic pressure lose, meaning im running up towards the flow limits of my turbo ( e316g).

Cooler air temps allowing more aggressive timing adv or leaner AFRs is the only way a slightly bigger turbo
taken thru the same power band, could produce more power than the smaller turbo could at only 20psi...

If you look at a lot of dyno graphs, at a low psi like that, the bigger 50trim, or 20g or whatever were comparing with, though it will make a tad bit more power up top, there could definitly be a bit of torque lose down low when coming from a evo316g.

You have to weigh cost, and worth, and what your car will be used for.
Bigger turbos only shine in high rpm at high boost period....

I agree with you 100%, bigger turbo's shine at higher RPMs, I was just stating theoretically a bigger turbo at the same PSI should be able to push more air. While torque and spool will be sacrificed, at 20 PSI there should be a noticeable difference between the smaller and larger turbo. Hence boost is not boost, even though boost is boost, haha confusing ain't it? But yes you're correct that bigger turbo's shine in the upper RPM ^^.

 

[daren_p]

DAREN,

yes. A turbo can only move as much air as the engine will let it. Granted a 3065 will be more efficient and will not heat the air as much, so the lbs/min will rise...some, but the CFM will stay very much unchanged. Where you see the big gains is having a 16 maxxed out that wont hold 20psi to redline, then switching to a 3065, and running 20psi, where it won't even break a sweat.

FYI the numbers i used were theoretical.

You are forgetting one major factor here, the turbine housing & wheel on the 3065 is alot better flowing then the 16g used in my example. Remember the old example that a motor is basically a big air pump, you remove some exhaust restriction & inturn allow more air in.

 

[dsm-onster]

Absolutely. I have submitted concrete evidence in that a 50-trim sized turbo at 20psi flows 2lbs/min (20ish hp) more than a 16g at 2psi more boost (22psi) and cooler ambient temps with no change in any other variable. The small 16g was absolutely not maxed out as the compressor map shows at least 38 lbs/min flow potential (400crank hp) and I logged 35.8 lbs/min maximum.

The compressor is simply a supply of air. Mr. Peepers is so right to say that there is SO much more to a turbo than a compressor.

Compressor efficiency is a moot point concerning heating up the aircharge. All the heat of a compressor at 60% efficiency is removed from a 75% efficienct intercooler, which any properly sized ebay FMIC can achieve.

The efficiency however tells us how much exhaust energy has to be used to turn the compressor at such an rpm. Thus how much gases have to be bottlenecked intothe turbine instead of freeflowed out the wastegate. An efficient compressor lets the turbine do less work and thus the turbine can be wastegated more allowing more flow out the tailpipe. More out means more can come in. More in means more flow and horsepower. A small 16g can flow to it's limit easier than a big 16g because the turbine needs less energy to spin the more efficient turbine. More exhaust flow is wastegated and the exhaust manifold pressure is kept lower, allowing higher overall VE and MUCH faster boost response. More gases are wastegated allowing more power per psi. REMEMBER, compressor efficiency assists in boost response (similar to spool speed). An efficient compressor yields higher boost earlier because the turbine needs to do less work to spin it at the rpm neccesary to achieve that pressure.

Thus, the small 16g makes more power at it's limit than the big 16g at the same boost. Many contend that the efficency heats the intake up, But they fail to see that infact the small 16g is wastegating more gases and allowing more flow out the tail pipe. . . The small 16g is the perfect marriage of a td05h turbine and a G-style compressor, IMHO. . . What the big 16g offers over the small: simply more flow. The small 16g may acheive more hp per psi, but the big 16g flows enough to overcome the difference and then a little more. The big 16g leaves more flow on the table and holds a higher boost to redline after the small has reached it's limit.

Back on the subject, my holset bep h1c flows as well as a 50-trim on the hotside and cold side. It has at least the same efficiency compressor. It actually has a very much more efficient compressor. So boost response is PHINOMINAL. Less energy is needed to make a certain boost pressure. More exhaust gases are wastegated to generate the same boost. VE goes up vs. a td05h hotside. The turbine itself is larger. So it can actually "net" or capture more exhaust gases to do work (just not quite as fast, hence lag). Thus at the same boost, You can see about a 4lb/min difference in flow.

An efficient turbine is AT LEAST as important as an efficient compressor. If the turbine can convert more exhaust energy into rotation, then the compressor doesn't have to use so little rotational energy to convert into pressure.

 

[steelzeus]

does anyone have the compressor maps for each one of the turbos to compare?

 

[dsm-onster]

Big Collection of Compressor Maps