Evo16g or 18g

[laserspeeddemon]

Remember, the inducer is the chief determinent of compressor airflow potential. The inducer provides the fan shape that pulls in the air to be compressed. The exducer (major diameter), no matter how larger, can only flow what the inducer provides. The inducer is the only portion of the compressor wheel exposed to the atmosphere.

There is a miniscule difference to the naked eye between the small16g inducer and the big16g inducer, yet it flows about 3 lb/min more.

You make a great arguement. It seams very logical. But is is simply not the case that the total diameter of the compressor determines airflow.

I threw the exducer measurements in to put all facts on the table. It's simple logic to know that something can flow only as much as whats in front of it.

Even by your point the difference in the small 16g vs big 16g is 0.06" (or 1.5mm) only yielded 3 lb/min. So an inducer that is only 0.01" (or 0.2mm) bigger would yeild 15% gain. 15% of 3 lb/min that's less then half a lb/min or only about 5-10 cfm. Thats like 4 horsepower if that.

I know the flow numbers are not exactly the same, I just stated they are damn close. From my rough head math they flow around 7 cfm differences. Thats damn close in my book.

 

[dsm-onster]

I threw the exducer measurements in to put all facts on the table. It's simple logic to know that something can flow only as much as whats in front of it.

Even by your point the difference in the small 16g vs big 16g is 0.06" (or 1.5mm) only yielded 3 lb/min. So an inducer that is only 0.01" (or 0.2mm) bigger would yeild 15% gain. 15% of 3 lb/min that's less then half a lb/min or only about 5-10 cfm. Thats like 4 horsepower if that.

I know the flow numbers are not exactly the same, I just stated they are damn close. From my rough head math they flow around 7 cfm differences. Thats damn close in my book.

15% gain of 3 lbs/min or 15% gain of total flow of the compressor. Still, you're only taking into account the linear increase in diameter of the inducers. You're not considering the area increase of the blades at the inducer. This is not a linear increase with respect to inducer diameter increases. You make excellent points. But again, .01" difference is significant in the world of turbos. The 20G wheel has around a 9% larger inducer than an evo3 16g wheel, w/ the same diameter exducer. However, it has been proven to flow 100 or so whp more in airflow!

The general blade shape remains the same between the evo3 16g, 18g, and 20g. Yet, the area difference between the inducer portions of the blades vary significantly. The 18G is about in the middle (between the evo3 and the 20g) with respect to a linear diameter measurement of the inducer, a little biased to the 20g diameter. But, calculating the area of each blade at the inducer, you will see that it grabs much more air than one would suspect. There's proof of an 18g compressor pushing 450whp worth of air! No evo3 16g powered STROKER has ever done that.

I understand if you do, but I don't want to agree to disagree, personally. I appreciate your opinion and enjoy a constructive debate w/ an intelligent person . This is certainly 'on topic', too.

 

[laserspeeddemon]

Horsepower numbers are the worst way to measure turbos, even if you try to rationalize it with respect to flow. Simply because you can alter the numbers with outside variables, everything from software (a good tune) to hardware changes (larger exhaust, intake, etc) will effect the numbers. Even if keep everything is the same the dynos vary measurements. And if you use the same dyno with the same car, the numbers will change depending on time of day and region (temperature, humidity). Perfect example; lets take a Big 16g. I have never seen a vendor rate the 16 family (execpt the TD05HR-16g turbos) more then 380 whp. You've never seen anyone come close to 450 on a EVO III 16g, but I have. A local guy here ran his small 16g to 387.xwhp on a 2g GS-T. I actually ended looking like a fool because I called BS, and he showed me his sheet and video. Obviously, I felt pretty dumb. Another member on here 90tsiawd (granted his is another wiseman) has pulled 413.4 AWHP from his Galant with a big 16g.

I only trust flow numbers, which is where our debate continues. I have yet to see a compressor map that is obviously labeled as a EVO III 16g compressor map. You also can't relate a 20g to a 16g, because not only are we changing compressor wheels there, you are also changing compressor housings. So that would be changing multiple variables on one argument. But looking at the inducer of the 20g turbo, it is 2.07" which is no longer talking about a difference of thousandths, but a difference of tenths. (Big 16g, 1.89"/EVO III 16g , 1.90"/20g 2.07"). That is quite literally 10 times the difference (or 1000% difference, not to be confused with ACTUAL size cause that would be a 2000" inducer).

Even if you use the case of the 18g vs. 16g variants, the 18g has a 1.98" inducer vs. the EVO III 16g 1.90" inducer. The difference is 0.08". This is a bigger margin of difference then the Small 16g and the EVO III 16g (which is 0.07"). Also all these turbos have the same sized compressor exducer, turbine inducer, and turbine exducer (except the small 16g).

I made Excel Spread a long time ago, when I was looking at upgrading the turbo. I had since added stats like linked compressor maps, estimated spool (for a moderately tuned 2.0L), even vendors with the best price. But alas, it was lost when my computer crashed a few months ago. Here is a small recreation of that same sheet using the same source.

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Now looking at the marginally difference in the inducer wheel sizes vs flow. For every 0.1" there is about a difference in flow of 65ish cfm. So if we again do rough math. Then each 0.01" is only about 6.5 cfm

BTW I love intellectual debates as well. I consider them fist fights of the mind. UFC style agruing.

 

[dsm-onster]

Horsepower numbers are the worst way to measure turbos, even if you try to rationalize it with respect to flow. Simply because you can alter the numbers with outside variables, everything from software (a good tune) to hardware changes (larger exhaust, intake, etc) will effect the numbers. Even if keep everything is the same the dynos vary measurements. And if you use the same dyno with the same car, the numbers will change depending on time of day and region (temperature, humidity). Perfect example; lets take a Big 16g. I have never seen a vendor rate the 16 family (execpt the TD05HR-16g turbos) more then 380 whp. You've never seen anyone come close to 450 on a EVO III 16g, but I have. A local guy here ran his small 16g to 387.xwhp on a 2g GS-T. I actually ended looking like a fool because I called BS, and he showed me his sheet and video. Obviously, I felt pretty dumb. Another member on here 90tsiawd (granted his is another wiseman) has pulled 413.4 AWHP from his Galant with a big 16g.

I only trust flow numbers, which is where our debate continues. I have yet to see a compressor map that is obviously labeled as a EVO III 16g compressor map. You also can't relate a 20g to a 16g, because not only are we changing compressor wheels there, you are also changing compressor housings. So that would be changing multiple variables on one argument. But looking at the inducer of the 20g turbo, it is 2.07" which is no longer talking about a difference of thousandths, but a difference of tenths. (Big 16g, 1.89"/EVO III 16g , 1.90"/20g 2.07"). That is quite literally 10 times the difference (or 1000% difference, not to be confused with ACTUAL size cause that would be a 2000" inducer).

Even if you use the case of the 18g vs. 16g variants, the 18g has a 1.98" inducer vs. the EVO III 16g 1.90" inducer. The difference is 0.08". This is a bigger margin of difference then the Small 16g and the EVO III 16g (which is 0.07"). Also all these turbos have the same sized compressor exducer, turbine inducer, and turbine exducer (except the small 16g).

I made Excel Spread a long time ago, when I was looking at upgrading the turbo. I had since added stats like linked compressor maps, estimated spool (for a moderately tuned 2.0L), even vendors with the best price. But alas, it was lost when my computer crashed a few months ago. Here is a small recreation of that same sheet using the same source.

I concede that looking at hp numbers to rationalized airflow capacity can be obscure considering a/f ratio and timing adjustments, as well as compression ratio. The only problem with your spread sheet is that we've all seen the turbos mentioned outflow those cfm numbers. So MHI has obviously been conservative. Has MHI been equally conservative (percentage-wize) across the board? Or has it underestimated one turbo more than another? I agree that a 20g in a proper td06h housing uses a different housing than the tdo5h turbos so a comparison needs to be done w/ the same housing. Was your cfm number you've listed for the 20g in a td06h compressor cover? Stealth316.com uses an approxmation symbol beside the 18g airflow. I've not seen MHIs actual assesment of airflow potential. . . Is one available? As well, since there is no map of an evo3 16g from MHI floating around we have no rated airflow of that compressor either.

Now looking at the marginally difference in the inducer wheel sizes vs flow. For every 0.1" there is about a difference in flow of 65ish cfm. So if we again do rough math. Then each 0.01" is only about 6.5 cfm

I'm not following you. There is a .09" difference in the inducer diameters between the Big16G, 18G, and 20G. And there is a 50cfm difference between the Big16G, 18G, and 20G. Every .09" seams to add 50 cfm. That is a significant difference. The big16g is about .01" different. I can see how an evo3 16g and a big 16g can choke marginally different. But we're talking about .1" difference that the 18g has over the big 16g, and .09" difference the 18g has over the evo3 16g.

EDIT: AH! I see why we are disagreeing. I keep mentioning 0.01" is a big difference in the turbo relm. But, I've been discussing the 18g vs. evo3 16g which I consider to be around .1" different at the inducer. . . I am sorry I didn't catch myself earlier. YES! 0.01" is not much different, but 0.1" will yield significantly more airflow.

BTW, I like to look at choke to find out how a compressor really sizes up. Especially since so many completely wring out turbos like the evo3 16g. One compressor may deviate from good efficiency but can still displace a great amount of air. While another may run efficient right up to choke, but still have a narrow map.

. . . Let's go out and tinker w/ our DSMs now .