50 or 57 trim

[elpiar]

I decided I will go with t3/t04e turbos. I used to boost my integra and what's popular was 57 trim. Here it's 50 trim (while the displacement is actually larger in KA). I wonder which one is actually has more flow rate?

[S13FX]

Ok brother here is a reply to a similar question that C-Kwik a mod on here has posted.

Quote »As I discussed already, size isn't as important as knowing a turbo's efficiency at given airflow rates. Bigger turbos as a general rule do tend to be more efficient at higher airflow rates, but it's not always the case.

However, running a more effcient turbo for the boost and airflow you're running will provide a cooler charge. This has a few benefits. The obvious one is that cooler air lessens the chances of detonation occuring as Brian already mentioned. Another is a denser charge which equates to more potential power in each combustion cycle. If a specific HP level is the goal here, then itcan be tuned to achieve that goal and run more conservatively on boost by perhaps running a bit higher compression ratios, maybe a bit leaner, and perhaps more timing advance. An added benefit of a cooler charge is that the intercooler is not as burdened. It can free up options to run a smaller I/C, or keep coolong capacity the same and provide more consistent charge air cooling and perhaps keeps a higher ceiling before heatsoak can occur. The latter 2 are quite beneficial if the car is tracked as the conditions are much more harsh for the intercooler on a track than on the street.

Another benefit I touched on already is the turbine side. A more efficient compressor for the given airflow and boost levels will reduce backpressure with any turbine. Match the turbine's peak efficiency areas with the compressors as well and there will be much less backpressure. Reducing backpressure will free up more HP, again, allowing you to run less boost to achieve a given HP rating. It will reduce the load on the bottom end as well. Lastly, lower backpressure means less heat, particularly at the exhaust valves. Hot exhaust valves can become a starting point for detonation. If you can reduce the chances of detonation, you can increase compression, run leaner, and/or advance timing and actually get even more power.

This all being said and going back to the issue of generalizing that bigger turbos flow more air, consider that a large turbo operating at a low boost level that puts it out of a reasonably desirable efficiency level will not perform or flow as well as a small turbo operating within it's peak efficiency areas. Turbo sizing should not put as much attention to larger or smaller as it should towards it's efficiency at the desired boost and airflow levels.

[/quote]

[WDRacing]

The simple answer is that the 50 trim is in it's peak efficiency island for a tad longer then the 57, but the 57 flows a tad more air. Both are excellent choices. If I could get a deal on one but not the other, I'd have no worries at all.

WD

[C-Kwik]

Be weary of looking at peak flow rates of turbos as a way of sizing. It's quite misleading. Just because a compressor is rated at some airflow level, it does not mean the motor could actually reach it. A compressor's peak airflow occurs at a specific boost level. You can see this by looking at a compressor map.



From this map, you can see the peak airflow is at about 43 lb/min. But it only occurs at a pressure ratio of about 2.7. That's pretty much 25 psi. So unless, you plan on running 25 psi, you'll never hit it. But even that is not an indication that the motor can actually flow that much air at that boost pressure. All motors will flow a given amount of air at a given boost pressure and Engine RPM (assume WOT). If a motor can only flow 35 lbs/min of air at it's redline, then the peak airflow rating of a compressor is irrelevant.

It's much more likely, that the peak airflow rating may become more relevant with a turbo that is sized relatively small for the motor. However, if this is the case, then near redline, you'll be operating the turbo in the lower range of it's efficiency at any boost level. If maximizing HP is the goal, then you want to make sure you choose a turbo that maximizes efficiency for the motor you will be using it on, perhaps trying to keep the powerband at or above 70% efficiency. The more, the better.

[C-Kwik]

The simple answer is that the 50 trim is in it's peak efficiency island for a tad longer then the 57, but the 57 flows a tad more air. Both are excellent choices. If I could get a deal on one but not the other, I'd have no worries at all.

WD

Brian, not sure if you realize, but the 50 trim T04E actually flows more than the 57 trim. Not sure why this is, but there must be some aerodynamic properties of the ratio between this major and minor diameter that just seems to work well. The entire compressor map is very untypical as it's broad across both a wide range of airflow and boost levels. And it flows more than what could be considered larger trim turbos.

[nissanfanatic]

Yup.

[WDRacing]

Nope, I always thought the 57 trim had a higher peak flow rate...50 trim FTMFW as usual.

The only thing I like more then the T3/TO4E 50 trim is a TO4R

[TrunkMonkey]

i can't find it, but i could have sworn we had a detailed thread comparing these two trims a while back.

i'm too lazy to plot the maps, but if i remember correctly, the 57 trim is slightly better suited for low boost (under 10psi?). anything beyond that the 50 trim is the obvious choice.

-demetrius

[elpiar]

Brian, not sure if you realize, but the 50 trim T04E actually flows more than the 57 trim. Not sure why this is, but there must be some aerodynamic properties of the ratio between this major and minor diameter that just seems to work well. The entire compressor map is very untypical as it's broad across both a wide range of airflow and boost levels. And it flows more than what could be considered larger trim turbos.

Yes, I remember reading this a while ago. Thanks for the replies guys!!

[C-Kwik]

i can't find it, but i could have sworn we had a detailed thread comparing these two trims a while back.

i'm too lazy to plot the maps, but if i remember correctly, the 57 trim is slightly better suited for low boost (under 10psi?). anything beyond that the 50 trim is the obvious choice.

-demetrius

I'd be curious how that conclusion could be made, but my answer would be the 50 trim is still the better option for lower boost levels over a 57 trim. Take a look at the 50 trim and 57 trim maps posted in this thread. More specifically at the 76% efficiency islands of each. The 50 trim's 76% island reaches down as low as a PR of 1.4. The 57 trim's 76% island only drops down to a PR of just under 1.6. And in fact, at a PR of 1.6, you will peek through the 78% efficiency island with the 50 trim. If you want even more to consider, just follow the 70 % efficiency islands of each and perhaps look at where the lowest points of each map stop.