Turbo sizing numbers

[encasemyheart]

http://www.turbofast.com.au/FlowTO4E.html

I was doing calculations on the TO4E turbo and what trim to use, I did my calculations and plotted out numbers for the KA24 on the 50 trim, 54 trim, 57 trim and 60 trim. I made 2 lines, one for my psi when I get the turbo on (12psi) and one for after the rebuild (18psi)

Here are my results:

Boost 12psi 18psi

60 trim 3800 4550

57 trim 3250 4300

54 trim 3450 3750

50 trim 3200 3400

These numbers are the different trims, above is the psi they were measured at, and the 4 digit number is the theoretical rpm the turbo should be fully spooled up at.

I was under the assumption that the larger trim #, the larger wheel. This seems to be correct except for one thing. At 18 psi it is pretty linear, the larger the trim, the slower it will take to spool. At 12psi the 57 trim spools alot better than the 60 trim, but WORSE than the 54 trim,a nd only very slightly worse than the 50 trim. How can a much larger trim spool up quicker/the same as than the 2 trims below it?

I'm assuming the wheels have different characteristics, they are not just smaller versions of one another, or my calculations are wrong. But I triple checked the calculations. Can someone please explain this?

BTW I realize the turbos will spool differently based on alot of things, but this should be a fairly rough idea of spool time with no exhaust restriction and equal length manifold non ball bearing.

If my findings are correct, it would seem the to4e 57 trim would be the correct choice, good spool at 12psi for street and decent spool at 18psi for race applications. They are all in good efficiency ranges too, mostly 76%.

[C-Kwik]

How did you get to those figures using just the compressor maps? Spool is affected much more by turbine size than by compressor size. Especially when you are comparing turbos that have the same major diameter(with the exception of the 50 trim which is ever so slightly larger). Certainly, a larger trim compressor will spool a little slower, but that's nothing to do with the mapping. It has to do with the heavier rotational mass of the larger trim wheel. But keep in mind there is only a small difference in weight from one trim to the next. My personal choice from those you listed is the 50 Trim. It can support a rather broad range of boost for a KA and for most of the boost range it will be in the 78% efficiency range at most boost levels. The KA will reach near the middle of the peak efficiency island on a 57 Trim near redline, which means it's not making full use of the available efficiency.

When looking at compressor maps, you are looking at efficiency. Nothing else. There's no easy way of calculating spool up characteristics. You leave that mostly up to other people's experiences and perhaps some technical knowledge from the turbo manufacturer.

[encasemyheart]

Ahhh...thanks alot, I was under the impression (from what a couple people have said) that the point derived from the CFM and boost pressure which meets at the surge limit was the spool characteristic.

And also you're saying it's not just getting into the efficiency island, but closer to the top? I'll keep that in mind and look over everything again.

You would really recommend a to4e 50 trim for 18+psi?

Thanks alot.

[WDRacing]

I believe the 50 trim is just starting to become inefficient towards 20 psi, But you'll benefit from the greater efficiency throughout the rpm band.

WD

[djtodd]

Yeah the turbine a/r is going to have the most effect on spool from what I''ve read.

Also, the 50trim is better suited(more efficient) with the stage III wheel and the 60 trim is better suited with the stage V wheel.

[encasemyheart]

Thanks, in that case I am going to go with a 50 trim stage 3 wheel. I guess I'll go with .63 A/R, that setup should support 400+whp fairly efficiently right?

[matt0941]

encasemyheart, I am also going with a T3/T04E (assuming you are going hybrid that is) with the 50 trim and .68 A/R ratio. Am I incorrect about the .68 A/R ratio because I thought that it was that, and the next option being .83 A/R. Unless you are getting that custom fabricated that is.

[encasemyheart]

No, just buying it, the place I am looking at has the t3/to4e 50 trim stage 3 wheel with .63 A/R for $549.

By definition it is possible for any A/R to be present, it just depends on a few variables. There are some that are more common than others, it really depends on what shop actually makes the turbo, the shop I am looking at makes A/R of .63, .70, .83, .84, .96, 1.04 most commonly. They can of course make special turbos of any ratio however.

BTW what boost are you planning on running?

[C-Kwik]

I believe the 50 trim is just starting to become inefficient towards 20 psi, But you'll benefit from the greater efficiency throughout the rpm band.

WD

Actually the 78% efficiency island reaches up slightly above 23 psi, but even then, you'll still be at a very acceptable 76%. I'd say you're probably okay anywhere above 70%. And if you look at the 50 Trim map, just about everything is above 70% ad moderate to high boost levels until you get into higher flow rates where it starts to drop in efficiency quite quickly...though I doubt the KA will flowing that high at the respective boost levels.

[C-Kwik]

Yeah the turbine a/r is going to have the most effect on spool from what I''ve read.

Also, the 50trim is better suited(more efficient) with the stage III wheel and the 60 trim is better suited with the stage V wheel.

You'll find that overall turbine wheel size will have a more drastic effect on spool charactieristics than A/R. I see A/R as more of a fine-tuning spec.

And turbine trim does not affect compressor efficiency. Only the spool-up and turbine flow capabilities. Deciding which turbine and/or compressor to go with comes down to your HP, response and boost goals. Fitment is also a consideration, but all else aside, there is not set-in-stone most efficient turbo spec.

[hannibal]

When you're choosing a turbo,1) do you want the end of the boost line (at full boost and approaching redline) to be in the middle of the peak efficiency island OR2) do you want it to end at the right edge of the island?

With option 1, you're spending more total time in the peak efficiency island. I can't think of any positives in using #2. C-Kwik, can you shed some light on this??

Thanks,Jay

BTW, yall have inspired me today. I've read so much good stuff on here, I feel like a 4 yr old about to pee in his pants.

[king_johnthegreat]

You may find that the 50 trim comp. wheel is maxxed out at 410hp. To find the peak hp output of a given comp. wheel, multiply the #/min of flow by 10. That is the max for that comp. wheel, not at the tires. So you would not really see 400+ hp with that turbo on a dyno.John

[C-Kwik]

My Turbonetics compressor map for the 50 Trim says it has a flow rate of 47 lbs per minute. I've never seen that calculation before, but I would assume it's more of an estimate. The problem I have with it though that is I've mapped out each ot the T04E compressors and none of them come close to reaching the max CFM of the turbos. Yet we have seen KA's with 350 Hp at the wheels at only 15 psi. And my best guesstimate puts max airflow at 15 psi on a KA near 30 Lbs/min. And 47 lbs/min occurs at approximately 23 psi. But the max airflow on a KA will be around 36 lbs/min. Though, while Ray Hall's turbo calc's puts the KA at approx 393 HP with 23 PSI, it seems to underrate it at 15 psi. So my opinion would be that at 23 psi, we may see more than 400 HP from a KA on a T04E 50.

[harry]

No, just buying it, the place I am looking at has the t3/to4e 50 trim stage 3 wheel with .63 A/R for $549.

hey where are you getting that for $549

[matt0941]

I am assuming he is talking about this: http://store.yahoo.com/cheaptu....html

Do any T3/T04E's have water jacket cooled center sections that you guys have ever seen? For those unaware: Water cooled jackets are an addition to the oil cooled center sections of turbines to prevent from oil coking, not that it happens that often but water jackets have additional benefits as well.

[d240t2]

Yes, my T3/T04E has a water cooled center section. Turbonetics also lists it in their catalog.