RXBeetle

I have a T04B with a 1.0 A/R and an O trim turbine.
The Compressor is an .70 A/R S trim T04B (this doesn't really matter since it's goin bye bye)
I have 2 questions that I just don't have the experience to make a good informed decision. Searching has and reading other posts hasn't really confirmed one way or another either so I figured this would be the place to ask.

1. Is the turbine sufficient to support ~300 whp on a streetported NA block? (high compression) I will have plenty of wastegate to flow the excess exhaust and will not be running high boost.

2. Which is a better compressor for my needs, a T04B H trim or a T04E 60 trim.

The engine is a streetported (intake and exhaust, no diffusers) '86 13b. The engine is going in my Beetle behind a Porsche 901 transaxle that won't take much more than 300hp. The goal is not to go hp crazy but to have as much usable power as possible over the rev range. The higher compression ratio NA rotors make me want the T04E since it is a more efficient compressor and will make less heat and hopefully allow me to get my power with less boost. The H trim is a smaller wheel which makes it tempting for a fast spool.
What do the pros think? I'm on the fence here.

bobybeach

The compressor option is not an issue. id stick with a large trim to4b since you already have a to4b cover and backing plate. The t04e is not a superior wheel over the t04b option, its just different not better.
Your real concern here is the small o trim turbine. Since you are using high compression rotors you can afford to go bigger turbine. The o trim will probably flow more than the stock ht18 Mazda turbine, but in my opinion this is more the area for concern not the compressor side.
I have seen an o trim to4b 1.00ar run on a turbo block 13b about 10years ago with definite power gains over stock, so it does work but is too small of a turbine to be considered upgrade over stock especially when using high compression.

The other thing to note is that a large wastegate wont help free things up. Since the turbine is so small a large valve will not be needed to control boost. In fact a 38mm will probably be plenty when matched with the o trim turbine.

In your application you will get more power with less boost if you use a larger turbine. The to4e compressor do have better efficiency at high boost levels over the t04b, but you will need to run aprox 18psi before you could measure any difference.
Since you will be running low boost with low compressor flow you will have better results with the lighter faster spooling t04b wheels.

RXBeetle

"id stick with a large trim to4b since you already have a to4b cover and backing plate."
I can't run a different trim compressor with the cover I have now... It's an S trim that is on it now has an inducer with a diameter of 1.904" and the compressor housing matches that. The H trim has an inducer of 2.298 and won't fit in the same compressor housing.

"The t04e is not a superior wheel over the t04b option, its just different not better."
The 60 trim T04E has a higher peak efficiency through out the boost range. Compare the compressor maps at 1.7 pressure ratio (10 psi). The T04E will match the H trim T04B efficiency (74%) all the way from 17 to 34 lb/min of flow. The T04B H trim will only hit 74% from 24 to 30 lb/min.

My impression is that it doesn't take much exhaust flow to spool a turbine and get get 10psi out of a compressor so I don't need a huge turbine. Wastegate flow reduces flow to the turbine so it seems to me that since I will be running low boost it would be important to have as much bypass flow as possible to prevent boost creep.

If I'm wrong on any of this please correct me, I'm just tryin to get the facts.

bobybeach

You will only need to high flow the compressor cover if you go with the to4b wheel. This is no big deal any turbo shop can machine it to fit a v trim or h trim wheel. its much cheaper than buying a new to4e cover, backing plate and wheel.

I always think compressor maps can be a confusing tool because you need to assume a conversion of hp to lbs/min. then assume static flow vs. boost. But even with constant psi the flow rate will change dramatically with engine rpm.
even with reading from 17-34lbs/min at 10psi will probably only reflect efficiency at an rpm range of 4000rpm-7000rpm at wot. I think a 13b will consume aprox 40lbs/min at 8000rpm with a boost pressure of 10psi

Also the compressor map I’m looking at shows the 60 trim to4e falling to 65%-68% at 35lbs/min at 10psi just like the h trim t04b at 65%-70% at 35lbs.
So i think there will be marginal if any gains from the 60trim to4e wheel over the t04b at those psi and lbs/min levels. But the to4b option will cost less and will have slightly better response also.

Your rite it wont take much to spool a t04b or to4e to 10psi, so that’s why you can afford to go with a much larger turbine that does not need to be so boost response and restrictive on exhaust flow. large turbine size is the secret to big power levels with minimum boost.

At the end of the day it will work going with the t04e but I think it will be wasted effort and finace changing it to to4e spec and leaving the restrictive o trim turbine.