Cavalli Turbo......

[96Mustang460cid]

If you assume both turbos are too much alike, then yes, you've built a strawman and your contentions are correct. The garden and fire hose analogy is specifically for pointing out this kind of discrepancy.

I originally corrected a post (quoted below, for reference) that erroneously used the water hose analogy...which I corrected with my original post in this thread.

18psi of water spraying from a garden hose versus 18psi coming from a fire hose; what one is putting more water on the ground?

Take two compressor maps for similar, but one larger than the other, turbos. At identical pressure ratios the mass flow can vary substantially while staying in the same efficiency island. Or, more realistically...pushing the stock EB turbo to higher mass flow forces it outside of any good islands, so it just superheats the air. A larger turbo allows the same pressure ratio, yet can supply the required airflow while maintaining high efficiency.

I understand and agree about pushing a small turbo past its efficiency island. I felt that some were implying (the water hose analogy) that a larger turbo, disregarding other factors, will always push more air into an engine with the same boost setting. While that can most definitely be true, I feel the statement should be qualified. It would not be difficult to create conditions where each of our arguments are true. For most gearheads, though, you'd most likely be right more often than myself.

I think the biggest question is how far has the OEM turbo been pushed before the owner "upgrades" his turbo? If a guy upgrades his 97% stock combo w/ stock boost levels, I would be shocked to see a magic 75 hp increase with the new turbo...given everything else was left the same. If a guy is already pushing the limits of the OEM turbo and still desires more power, his combo is a much better candidate for the upgraded turbo and he'll obviously gain a lot more from the turbo upgrade.

You're obviously knowledgeable about this topic and I, admittedly, am just an amateur gearhead. Nevertheless, I've seen too many people purchase 'upgrades' that fail to yield the desired results because it was not a good fit for the combo. I'm not trying to split hairs on this subject, but I also don't want people thinking a turbo swap on a mostly stock engine will yield x,xxx,xxx hp increase. I'm not implying people and/or companies intentionally mislead consumers. Instead, I felt the topic should be qualified for the sake of the less knowledgeable.

Hmm...just to be clear, the wastegate is controlling turbine speed and has nothing to do directly w/ 'bypassing excess air' as you keep stating. Again, mass flow will be higher from the larger compressor than the smaller at identical output pressures.

energy in * efficiency = energy out

Respectfully, I disagree. How does the wastegate control turbine speed? By bypassing excess air (aka: energy) around the turbine wheel. Once you reach your desired boost level, the wastegate opens and bypasses 'just' enough air to maintain the desire boost. As engine conditions change, the WG also adjust how much air its bypassing and, therefore, controls boost.

This is why you have different sizes of WG. Generally speaking, a large turbo on a small engine or reducing boost levels on the same engine requires more WG capacity to effectively bypass enough air and control boost. Otherwise, you start getting boost creep.

It's been enjoyable and I hope other readers get something out of it. Herr, don't dumb it down too much. Some people want to understand at a deeper level. I encourage you to not deprive the thirsty ones .

Have a good day!
Michael

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[96Mustang460cid]

The dyno graphs compares a Hellion twin turbo system. The only difference between the two combos is the size of the turbo.

Source: http://www.mustang6g.com/forums/showthread.php?t=17969

Red line = twin 55mm turbos
Blue line = twin 62mm or 64mm turbos (I forget what size, exactly)

Top graph = horsepower
Middle graph = torque
Bottom graph = boost

This example shows exactly what I'm trying to say. Once both turbos are spooled up, the power curves are almost identical. In this example, the larger turbo, compared to the smaller turbo, is not flowing any more air into the engine before the wastegate opens. Depending on your goals, the smaller turbos may be a better fit and run faster at the track.

Have a good day!
Michael

 

[DanFish]

The dyno graphs compares a Hellion twin turbo system. The only difference between the two combos is the size of the turbo.

Source: http://www.mustang6g.com/forums/showthread.php?t=17969

Red line = twin 55mm turbos
Blue line = twin 62mm or 64mm turbos (I forget what size, exactly)

Top graph = horsepower
Middle graph = torque
Bottom graph = boost

This example shows exactly what I'm trying to say. Once both turbos are spooled up, the power curves are almost identical. In this example, the larger turbo, compared to the smaller turbo, is not flowing any more air into the engine before the wastegate opens. Depending on your goals, the smaller turbos may be a better fit and run faster at the track.

Have a good day!
Michael

You are definitely correct. But once you imcrease the boost the 62/64 will produce more power. The 55s are only good up to 800 HP.

 

[96Mustang460cid]

You are definitely correct. But once you imcrease the boost the 62/64 will produce more power. The 55s are only good up to 800 HP.

Yes, Dan, you're right. If your goal is 800 hp or less, the 55mm turbos are great. If your goal is much above 800 hp, you'll benefit from the larger turbo...at the expense of lost midrange (aka: spool). You can see the boost dropping off on the 55mm combo in the upper RPM.

Have a good day!
Michael

 

[KazyMedic]

Yes, Dan, you're right. If your goal is 800 hp or less, the 55mm turbos are great. If your goal is much above 800 hp, you'll benefit from the larger turbo...at the expense of lost midrange (aka: spool). You can see the boost dropping off on the 55mm combo in the upper RPM.

Have a good day!
Michael

+1, but a single 6262 on 2.3L engine should still see full boost at 3400 RPM.

 

[greg hazlett]

+1, but a single 6262 on 2.3L engine should still see full boost at 3400 RPM.[/QUOT

Isn't that a really big turbo for only 2.3 liters? I would think the lag would be really bad on that and the 2.3 does not have a lot of power/rpm to be coming out of the hole to get into the power band?

 

[KazyMedic]

+1, but a single 6262 on 2.3L engine should still see full boost at 3400 RPM.[/QUOT

Isn't that a really big turbo for only 2.3 liters? I would think the lag would be really bad on that and the 2.3 does not have a lot of power/rpm to be coming out of the hole to get into the power band?

I know that a lot of people on the evo X platform were seeing the results I was speculating with the 6262. Not only that, but that turbo lag will save your rods some stress in the long run. That being said, I think the 6262 would be a drag application. A 5858 would be sweet for road racing.

Edit: That was with the bored 2.3 4B11T

 

[MAPerformance]

I know that a lot of people on the evo X platform were seeing the results I was speculating with the 6262. Not only that, but that turbo lag will save your rods some stress in the long run. That being said, I think the 6262 would be a drag application. A 5858 would be sweet for road racing.

Edit: That was with the bored 2.3 4B11T

A 6262 doesn't event spool until 4500 on a built 89mmx94mm 4b11t EVO X. Evo x's are our bread and butter. The 5858 on the EBM spools at 3700 at 25psi, I could get it to spool a hair faster with some ethanol.

Results are in my phase 2 thread in my signature, and on the previous page.

 

[96Mustang460cid]

Here's how I think about it:

If two of the turbos work on a 5.0 liter engine, one turbo should work well on a 2.5 liter engine. If the twin setup is slightly large on a 5.0, it'll be a bit more oversized for the 2.3...and vice versa.

Have a good day!
Michael

 

[bigspoondude]

A 6262 doesn't event spool until 4500 on a built 89mmx94mm 4b11t EVO X. Evo x's are our bread and butter. The 5858 on the EBM spools at 3700 at 25psi, I could get it to spool a hair faster with some ethanol.

Results are in my phase 2 thread in my signature, and on the previous page.

What's the powerband look like with the 5862 behind the stock turbo? ;)

 

[Herr_Poopschitz]

Respectfully, I disagree. How does the wastegate control turbine speed? By bypassing excess air (aka: energy) around the turbine wheel. Once you reach your desired boost level, the wastegate opens and bypasses 'just' enough air to maintain the desire boost. As engine conditions change, the WG also adjust how much air its bypassing and, therefore, controls boost.

Ah...semantics. I think of 'air' as cold side...usually use 'exhaust' for hot side.

 

[KazyMedic]

A 6262 doesn't event spool until 4500 on a built 89mmx94mm 4b11t EVO X. Evo x's are our bread and butter. The 5858 on the EBM spools at 3700 at 25psi, I could get it to spool a hair faster with some ethanol.

Results are in my phase 2 thread in my signature, and on the previous page.

You had 2.3 4b11t?

 

[MAPerformance]

You had 2.3 4b11t?

I've had basically every displacement for the 4B11T. We built a few custom 2.5L's even for some guys looking to make big power. Our engine and turbo kit is currently on the highest horsepower EVO X to date. (2.4L and our T4 kit with 71mm PTE turbo.)

 

[Billy1]

Now if we could only get the Ecoboost exhaust to sound deep like a modified Evo 8,9 or 10

 

[MAPerformance]

Now if we could only get the Ecoboost exhaust to sound deep like a modified Evo 8,9 or 10

Sounds much better with upgraded turbo, some videos in my signature!

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