I remember reading or hearing that the BNR Turbo has a 400hp limit based on limitations of the exhaust side. Ignoring the complexities of a blanket statement of max supported HP for anything, Is this limit because of the Hitachi turbine housing or the Mazda turbo manifold? I'm running a custom turbo manifold keeping the twin scroll of the S5 BNR turbo that I have implemented in my build.

I guess in some ways I see the theoretical 400hp max as a sort of fail safe. My fuel and ignition system can (in theory) cover me to 500hp. which was done as overhead. Not as a goal. If removing the stock turbo manifold with a more efficient manifold if that changes the dynamics.

Any insight ?

 

Fr9m 2001-2014 I found there is a lot one can do to the S5 exhaust side to make it flow more if you feel that is a bottleneck on your set-up.

Is your BNR hybrid bored for a larger "S" trim or "P" trim exhaust wheel?
The larger exhaust wheels flow more and when you bore the exhaust housing it makes the exhaust scroll slots a bit wider too.

I went further and ported the slots wider for more flow. Any enlargement will hurt turbo response a bit and in widening tje slots you are mak8ng a divergent A/R which is less efficient as well.

I was trying to stop boost creep, so I ported the manifold and turbo exhaust housing up to the wastegates and made the WG passages larger and favorable shape for exhaust flow.

This was because even with 60mm external WG I still had boost creep. Again, this impacted turbo response, but it helped boost creep and 8ncreased total system exhaust flow.

In the end, for me it was the T04B 60-1 compressor in the little HiFi compressor cover that limited my power.

Mine did 345rwhp at 10psi creeping to 11psi.
It made 385rwhp at cranked up to 14psi.

On race gas I cranked it up to 18psi by overfueling and retarding timing to overspeed the turbo since the turbo was maxed. I did it to gain more midrange and eeked out like 5hp more peak power as well.

If you put the larger T04 compressor on it you will get 10% more flow. That wont fit stock TII manifold and iTII lower intake, but maybe it will fit yours.

2014 I went with a EFR 7670 (same compressor wheel dimensions) kit I pieced together and made 420rwhp/420rwtq and much better response.

So, IDK how much effort and time you want to put into S5 stock hybrid.

 

i don't know but the way you would find out is with pre-turbo back pressure. there will just be some point where its too high to make power. your manifold is probably better than the factory one, so i'd expect little more hp there

i might have some actual numbers soon. i made the fittings to hook a gauge up to the EGR passage, but it has turned out that if you block the EGR passage, it doesn't work so well... will have to try the ACV passage

 

I had the big "P" trim exhaust wheel.

The copper gasket for turbo blew out racing, so I ported the stock multi layer stainless one and it worked well.

 

Bryan had a customer that had the larger T04(E?S?) Compressor cover on his hybrid because it was on a cosmo (lower intake manifild clearance).

It did made over 400rwhp as expected (manufacturer literature states T04B HiFi cover flows 90% of the fullsize compressor cover).

 

This is what I have: the revised one size fits all BNR S5 Turbo and the manifold below.

 

Oh, that is a new spec for the BNR.

That smaller compressor wheel is a better match for the stock exhaust side.


i would think 400rwhp is going to be the lmit of the compressor based off the 54mm/71mm dimensions.

 

honestly, I was shooting for 300-350 at the wheels. Thing is this is not a dedicated race car, so I'm not chasing the same power band and peak power someone who is drag racing or road racing. According to my data-logs and Howard Colman's formulas, I think I'm at 235hp at 5psi with an AFR of 11:1. either that or its 260hp. 50% duty cycle on ID 1050x for the secondaries, but data log reported 700cc flow. (primaries are ID1050x as well) Either way not bad for a six port 13b.

 

Following thread.

Also a 6 port turbo here with s5 NA rotors and stock engine porting, I am running an older BNR stage 3 picked up with low mileage on a stock OEM S5 turbo manifold and have gotten to the point where I am tuned and running 11-12 psi on ethanol. I have had some creeps to the 14 psi range even with my Mac valve setup to the best of my knowledge.

looking forward to more discussion for these particular setups.

-M

 

I have kept the aux ports functional. Triggered by boost, tps and rpm. Yes, I’m sure I’m leaving peak power on the table not going four port. I had access to a six port and decided to go for it. Once again I bring up my data logs. Did some pulls. Realized that there is a built in timer. I knew I slowed down at 60. So I’m about 0-60 in 5 seconds at this time. I also wasn’t flogging on it. Still a bit nervous. I would like to be in the mid fours for a 0-60. Perhaps low 13s in the 1/4 on street tires and a non drag suspension.

 

Is the A/R on that turbine housing known?
.

 

.70 a/r

 

.70 is compressor housing.

Stock S5 turbo exhaust housing is 1.00A/R

 

Im using a port matched Turbo II lower intake and mated it to my 6 port keg. Removed the 5th and 6th port sleeves and left them empty. Looking back i'd like to have the inserts from Atkins for smoother airflow in those additional ports because I feel like there some turbulence happening under boost but i cant be certain. I'm sure by you keeping your ports functional you have better low end response and torque before you begin to build boost. Fun stuff!

-M

 

I did use the Atkins aux port inserts. Other highlights is the Pineapple Racing streetport, and the Racing Beat lightweight steel flywheel. I run out of gearing pretty quick. My alignment is a bit off, so past 60mph the car becomes sentient. I’m all I’m pleased with Atkins sleeves. Not sure if it added power, but the engine is smooth.

 

thanks, I remember that now

even at that value given the small size of the OE turbo the peak flow capacity rating is going to be the limiting factor. Which is why the aforementioned 60mm external wastegate that’s more suitable for a 20B is not going to solve anything, let alone a smaller IWG. Honestly surprised it can get anywhere near 400 whp.

hey there little guy …

 

1.0A/R T25 size volute is the same as T3, T4, T6 1.0AR volute.

Its the exhaust wheel and what is between the volute and the engine that is going determine flow.

If your turbo manifold included a T4 turbo volute cut to mate up to the T25 volute where the cross section is the same it would flow same as a T4 housing with the same exhaust wheel.

 

the last 30 years of turbo technology proves otherwise, you’re stuck in a rut of inaccurate assumptions and generalizations
.

 

Please educate me and correct my assumptions and generalizations.

How has the definition of A/R changed over the last 30 years?

 

In all honesty I think that perhaps we both mistook what the other was trying to say, which I was thinking this before making that last comment but went ahead and let if fly any way

but to address your question, A/R is only a dimensional relationship between two values and what those values are really matters as much or more than the relationship

consider this:

if A = 6.00 and R = 6.0, then A/R = 1.0

if A = 3.00 and R = 3.0, then A/R = 1.0

However, can you readily recognize that the flow potential between them is not going to be the same? In reality, there’s more at play that just impeller size. How many years does the Garrett G-series have to be out before certain things become more apparent?

Because when you’re talking about flow, the flow channel itself (the scroll interior) can define how much flow is going to get through and at what resulting back pressure. As you noted, as a general theory the diameter of the impeller size can potentially allow for higher flow than a smaller one *all else being equal*. The question is, are they equal in ever other regard? In the case of the Garret G-series; obviously not.

Further, if a turbine housing with a smallish scroll designed for a lower output level is designed such that it can be machined out to fit a larger impeller, then the circumference length opening from the scroll does become longer and potentially allow more flow area to the impeller. Yet if the scroll interior cavity itself isn’t really sized for that higher flow level then it may not necessarily allow for as much flow relative to back pressure. It’s the equivalent of a pipe diameter vs length vs flow rate that defines this.

Because typically a turbine housing made for a larger impeller is going to have a bigger scroll; resulting from a larger area on a larger radius. So even if two turbine housings both have a 1.00 A/R, the flow potential through them relative to pressure isn’t necessarily going to be the same.

So we know people have hit 400 whp on this setup, but my initial conclusion was that the emap likely wasn’t looking too healthy. That’s all I was really eluding to in the first reply that you then replied to followed by my counter-reply. However, not being as familiar with this particular setup as you are I may have misunderstood the particulars of the turbine housing being used and then am possibly in error on my assessment. At which point I defer to your experience on it.
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