socalrotor

iTrader: (1)

IIRC he only would use mazda oem on the higher end buildups. I can find out later today.

boost_its_what_for_dinner

sweet thats what landers used in my build

TweakGames

iTrader: (3)

Sooooo here after all my reading I am starting to see some ..... weird results...

Personally for me I am looking for something that will spool as fast as possible, but put down 300-350 pretty easily. I hear that a stage one isnt spooling very good, and then I hear that a stage 4 is spooling at around 3500... I know he has a monster port, but "boost its whats for dinner" has a street port also. I know not all engines are the same, but could someone possibly explain what is going on?

I want to try and get my 7 to have a wide predictable power range, and I like the steady flat torque curve on the stage two.

Bryan, do you have any more dyno graphs that show boost, levels and have a detailed setup of what each engines (porting and exhaust).

Thanks.

BLUE TII

iTrader: (9)

There are so many factors that affect turbo spool up! I will try to cover some that I think are at play here.

The people that are running the stage 4 turbos typically have more mods that help a turbo spool in the first place.

The bigger, more free flowing the exhaust the better for spool- period, the end

For example, I run 3.5" for the 1st ~5 feet from turbo and the RB 3" rear section from there; full boost 15psi in 5th ~3,300rpm.

When I run the full RB 3" system I get full boost ~3,800rpm.

When I run the RB 2.5" downpipe/presilencer to 3.5" single exhaust it does not make full boost at any rpm. It is choked down to ~12psi even if you remove the wastegate (external).

Obviously, exhaust is a big one for spool.

Next is intake pressure drop before the turbo. The less the better! The stock AFM and intake duct is restrictive enough to noticeably hurt spool.

TID mod really helps spool up when using stock AFM, but it will be even better without AFM.

I guess I could toss an AFM on in front of my turbo to test out how much spool is affected, but it won't fit with my 9" air filter. Yep, 9" long cone airfilter from a turbo diesel application is available because they also know how much pressure drop before the turbo affects spool.

Next is intake pressure drop between the turbo outlet and the intake ports. Way back in the '80s Grassroots Motorsports did a project TII and they found the stock top mount IC has a pressure drop of over 1psi at stock 6 psi boost!

The TB mod is another way to decrease pressure drop as is manifold porting/swapping (I run 3rd gen TB and UIM for instance).

Little things like flaring and knife edging the lips of your intake tubes, decreasing the number of bends in your IC piping (I have one ~6" radius 90 deg and one 15 deg bend) as well as length of piping (about 2 feet on mine) will help a little as well.

Remember just a psi more boost (power) at 3,000rpm is really going to help bring the full boost threshold down in rpm as turbos spool exponentially- so every little bit DOES help.

Then, porting is a big one. A good streetport is making more power than stock ports before the turbo is fully spooled and that means more exhaust energy to spool the turbo.


Last of all I will talk about the turbo as it has some impact on spool up as well.

The larger compressor wheels will move more air at a lower rpm than the smaller ones. This can make for better spool up IF it takes the same amount of exhaust energy to get the turbo rpm up to the same point as the smaller turbo. More exhaust energy is avialable with a bigger exhaust of course...

If you have that big compressor wheel coupled to the small stock exhaust wheel (especially if that stock wheel is clipped reducing efficiency) there is the chance it will hurt spool up as the same amount of energy (or less clipped) is available to drive the compressor but the larger compressor wheel has more mass and drag.

This is not always the case though as I can think of one Australian's hybrid that used the stock exhaust wheel and a big compressor on a custom tubular manifold and a 4" exhaust and it spooled awsome.

When you have a larger exhaust wheel coupled to the compressor wheel (BNR stage 4) the exhaust has a longer lever arm (wheel diameter) for leverage to spool up the turbo faster. This works great if you have a large pressure differential between turbo and exhaust (big exhaust) and not so well if you have a smaller pressure differential as the added mass of the larger wheel(s) has to be overcome.

Next point is, the higher the pressure differential between sides of the turbine the better the spool up, but the higher the pressure between the turbo and the exhaust ports the worse the spool as exhaust will dillute the intake charge during our overlap phase (both ports open) decreasing engine output.

For instance, with my set up (high overlap porting) an unclipped "P" trim exhaust wheel spools up worse than the clipped one because even though it is more efficient it flows less causing more exhaust pressure, causing more intake dillution. However, when I put the stock exhaust wheel in the turbo housing for the "P" trim wheel (like 1/2" gap for exhaust to bypass the exhaust wheel) it still spools up amazingly well because even though it is horribly inefficient there is more flow available to drive the turbo.

Last of all the disclaimer. None of this info is based on any scientific study I have done; it is based on my own experiences and trial and error.

However, if you copied my set up exactly you would have the same results, so whether I have the reasons why it helps spool right or not it would seem silly to me to argue that the mods listed above will not help spool up.

Stupid long post over.

TweakGames

iTrader: (3)

that is a very nice post thank you. So the main thing would be the bigger the exhaust the better, the lower the restriction before and after the turbo the better, and the more power the engine makes to begin with, the better.

I love how my stock turbo (s4) is spooled up around 2.5 in any gear other then first. I think I would be able to accept 3,500 if it held it all way to redline.

My current build is a street ported 13b-RE, with ported FD housings. With that and a 3.5 or 4 inch exhaust+down pipe (if I can figure out a way to make it fit) you don't think I will have any boost complaints? I will be looking for a new/better intercooler since the one I have right now for my v-mount might not be the best for lag. (semi small)

So when you say that you have a high overlap porting does that mean some sort of bridge port? I don't quite understand what a clipped or unclipped or p trim means. Could someone go into slightly more detail on that?

Thanks.

BLUE TII

iTrader: (9)

The S4 versus S5 turbo is something I didn't even get into.

The stock S4 turbo with the dual scroll actuator working can make full (stock) boost around 2,000rpm, but that is only 6psi boost.

Try to use S4 twin scroll to make 15psi as low as possible and you get into a situation where the flow is so compromised by the primary scroll .4 AR and tiny volume that even if you make the boost it is so inefficient you are making less power than if you were making less boost with both scrolls open- or even better with the S5 divided dual scroll turbo.

A prime example of this effect is to look at a big single turbo that doesn't get full boost until 4,000-5,000rpm but would make the same 100RWHP at 3,000rpm as that stock turbo. At 3,000 rpm the flow of the big turbo is raising the volumetric efficiency enough to overcome the much lower boost.

Check out lots of dyno graphs of different set-ups. In the 400RWHP and below range if it doesn't make 100RWHP by 3,000rpm it is an inefficient set up. The only set ups I have seen that make more (120RWHP @3,000rpm) are the FD sequential turbos with mods for better spool/flow.

Much above 400RWHP the lag is typically so bad it starts to impact power at 3,000rpm, but isn't it interesting that decent single set ups from stock to 400RWHP will all make 100RWHP by 3,000rpm but very few can make more?

____________


Like if you built the S4 turbo you have into a Stage 4? I have no idea, the 400RWHP S4 stage 4 that GuitarJunkie built up similar to yours got full boost incredibly late (like 5,000rpm?).

In that case I would complain that it was WAAAY laggy.

My own S5 stage 4 set up took lots of work to stop boost creeping past 20psi by 3,000rpm.

In that case I was complaining I couldn't drive it without fear of blowing it up.

So, yeah- there is always room for complaints

--------------------

It is a large street port that has earlier opening intake and later closing exhaust as well. At 1,000rpm idle it has a distinct lope in the idle but ony gets brapy like a brige if the tuning is off a bit.

Full boost before 3,500rpm but the ports don't really come on until 5,000rpm and you get a huge hit of power then. But a lot of that is from the late intake closing as well.

"P" trim is the size of the T04 exhaust wheel it is much larger diameter than stock. Clipped is when the curved vane rear section of exhaust wheel is back cut to make it flow more. It is typically attributed to more lag, but more top end power.

RX7 13B 4 UR AZZ

iTrader: (8)

Large Street or bridge and a gt35r or gt4088r and be done with

boost_its_what_for_dinner

fuel has alot to do with spool also

i have a very rich fuel map in the low rpmsw and it takes a few to spool(3500-4k) but when it there it screams like a banshee... but i have rtek 2.0 and afm still i cant tune it very fine due to crappy rpm increments

idle is very hard to tune and you cant adjust fuel above 6600 as far as i know?

so im looking into a microtech now so i can optimize my whole set up and im going to get a custom 3.5 in dp made for the stage 4 that is coming soon after tax return.

JWteknix

iTrader: (2)

exactly y i am in the process of hooking up my pfc so i can see what this thing will really do then i shall go even bigger and keep this as a daily

TweakGames

iTrader: (3)

so... what is the advantage, ( other then external wastegate) to going something like gt35r instead of a stage4 hybrid? If people are getting boost before 4k... and still making 400 hp...

BLUE TII

iTrader: (9)

I dunno, I have a 60mm external WG on my BNR stage 4 as well.

The advantage the GT35R has is it is made for a piston engines that runs 20psi from the factory and 25-35psi in a performance application and so is more efficient at high boost.

If you want to put race gas in your car and turn up the boost GT35R will make more power than a 60-1. The 60-1 has a broad map that really matches the rotary, but is not good at high boost.

Also, there is more to turbo response than just when you hit full boost.

Before I ported out my hybrid's manifold and turbo runners to stop the boost creep I had it was much more responsive. There were several stop signs that I couldn't pull away from without wheelspin, it was twitchy responsive on the freeway and had more boost from 2,000-3,000rpm even though max boost was reached at the same rpm or even later. It felt like a higher displacement engine rather than a turbo engine to me.

Of course it has more top end now even without boost creep.

If there is an advantage to a GT35R at pump gas boost levels it would be in this kind of response, but honestly from what I have seen on this forum it looks like GT35R is less responsive down low than even my current set up.

For my next turbo I would like to do a stock S5 hybrid with the BB T04S center section (60-1 wheel) and T04B comp housing. I would avoid porting the runners out to stop boost creep by finding a better wastegate(s) position.

It might have a little less top end than what I have now, but that would make it easier to race.

htkingswood

Has anybody done this modification? I am having trouble holding boost with my BNR stage 3. The car hits 14psi and leaks down to 10psi.

I have a 3" dump, twin 2.5" into a high flow cat (new) with twin racing beat mufflers, 1750cc secondary injectors, microtech LT8 ECU, Walbro intank pump, Sard fuel regulator, ARC top mount, Twin MSD CDI's, Greddy L10 spark plugs, MSD wires and Water injection. The engine has perfect comp.

My car dynoed at 220rwhp The tuner said in must be my acuator
Bryan told me the car should be making an easy 300rwhp on 10psi, he suggested a few things which we'll try.

I'm taking the car to the legendary Rice Racing for a final tune but because he lives a distance from me I want to sort out why my local tuner can't get more than 220rwhp. It's doing my head in

Any help would be apprieciated. Happy holidays to everyone

TweakGames

iTrader: (3)

Ok, I would rather have the higher displacement engine feeling than a smaller engine/big turbo peeky feeling.

What is your setup again? Stage 4 correct? If you do upgrade to a different turbo I would gladly buy yours if it makes boost that early and feel like a higher displacement engine.


Also when you says 60-1, is that the compressor side on the stage 4?

Is this something bnr can do? or something someone would have to build themselves?

BLUE TII

iTrader: (9)

Yeah, higher displacement feel would be much better for the Auto-X I like to do, but along with this response came boost creep for me.

Unfortunately, my current set up now feels like a big peaky turbo (despite the very early boost) in part because of the ported manifold and runners on the turbo which removed the S4 velocity stack shape and in part because I have a huge late closing (70 deg) ports so there is reversion at lower rpms.

My next engine will close earlier, I will keep the port volume down and I will try to find a way to stop the boost creep without porting out the stock manfold's velocity stacks.

Yep, S5 BNR stage 4 with 60mm external WG. It doesn't feel like higher displacement engine now, but I will try to get it back to that.

Even ported like this it had boost creep


Until I ported the manifold and runners larger like this




It will probably be a long time still before I get rid of this turbo.

Yes, the BNR Stage 4 uses the 60-1 compressor wheel in a T04B .60 AR compressor housing and the T04S uses a 60-1 comp wheel in a .70 AR comp housing.

BLUE TII

iTrader: (9)

Found a pic of my BNR Stage 4 all together




I am sure Bryan (BNR) could build this BB 60-1 hybrid for you, but I bet he will recommend that you just get a full T4 frame turbo, manifold, etc.

This stock hybrid using ball bearing 60-1 center housing would have great potential, but there would be lots of quirks and fabrication involved to get it working right.

I would ask him bore the stock exhaust housing to accept the T04 center housing and exhaust wheel and work the rest out on my own because it is fun for me.

To have him (or anyone) do the whole project would cost too much because of all the time involved.

Hmmm, a BB T04S on a 3rd gen cast divided manifold with a small .80 AR T4 exhaust housing would be pretty similar for response and power potential. It is just that the wastegate size and location is terrible on these cast manifolds.

Node

iTrader: (1)

damn fine piece of work ian. ive gone insane as of late and the new fc is on the backburner again but i have my first gen now

junito1

put a TII on thats first gen.

siguy2k

iTrader: (3)

Well after reading through all the pages i think i am leaning towards the stage 4? I have turbovert s5 and am just trying to keep it as simple as possible and put down around 380rwhp which seems very possible with that turbo. A few questions are there any modifications needed to bolt it on and make it work? All the oil feeds are stock? My motor is streetported, 3in turboback, corksport fmic, i plan on getting a power fc and probly 1600cc secondaries. Thanks

jacobcartmill

iTrader: (6)

blue TII, you spent way too much time and money on an upgraded stock turbo.

htkingswood

Sorry to change the topic. I would like to know if anyone using BNR's has had trouble making boost. My stage 3 won't boost more than 10psi. It's doing head in, someone please reply as I'm running out of options. Thanks

BLUE TII

iTrader: (9)

Others with the Stage 3 have had a problem where exhaust backpressure forces the wastegate off its seat so you cannot build enough boost.

People have fixed this by simply adding an additional spring to the WG spring or putting an turnbuckle on the WG rod to pretension it more against the seat.

A less restrictive turbo back system will help as well. If I run a 2.5" RB downpipe/presilencer to 3 1/2" catback my Stage 4 cannot achieve full boost. If it is 3" turbo back full boost is nearly 4,000rpm. With my 3 1/2" system full boost is 3,300rpm.

The big compressor makes the turbo very sensitive to exhaust backpressure.

htkingswood

Thanks BLUE TII, The rod has a turn buckle and the spring only netted an extra 2psi. My exhaust is 3" into twin 2.5" and very little rescriction. Bryan has been helpful, I'm going to try a few things he suggested. Bill Nabham from Mazsport is going to muck around with it next week. He is trying to source a high boost diapham. I'll post the dyno figures once I'm making boost. The goal is 18psi with Rice Racing Water Injection. Rice is pushing for 20psi and buckets of water I'm confident 18psi with get me to 300 rwhp.

boost_its_what_for_dinner

^^^18 psi should be closer to 350..

boostin_7

So what boost pressure have people found to be the limit of the stage 1 b4 she starts making more heat than power??

blmcquig

iTrader: (15)

well, i talked to Brian at BNR today, and he recomended the stage II for me. i do a lot of autocrossing, highway pulls, and some track days, so i needed everything to mesh well together. im shooting for 315rwhp, so we'll see what happens.
does anyone know what size the inlet for the stage II is? I think Brian said 3", but im not sure if i heard him correctly.
also, anyone who has ordered from him recently, how long did it take to get your turbo back?
looking forward to being another satisfied BNR customer.