Changing hotside from .82 to 1.05
 

Hi everyone, Been a long time since I posted.
The turbo is a PT6266 Vband in and out .82AR. Thinking of changing to the THV5S turbine housing which is 1.05AR.
What would be the effects on performance?
How about the tune?

Reading my own post, I think I may not have given enough info for someone to be able to formulate a reply.


The car is a 94 FD, The Turbo kit from A-Spec was installed going on 5 years ago. At that time it had a mild street port, and we were expecting close to 500whp. The tuner was only able to get about 400whp, and said it "seemed restricted". About 2 years ago it needed some body work and we took it to Speed 1. While there, we had Dave touch up the tune to try to improve the injector staging event (still sucks). While on the dyno the engine laid down, broken apex seal and dented rotor. So they went through the engine, put in lightened TII rotors, and and much more aggressive port job. So now it gets to 425whp. Dave says it "seems restricted".

The owner of the car and I have had discussions about what could be changed, And I feel the .82 AR turbine housing seems to be the likely culprit. I was looking at T4 housings to see if maybe I could make it fit with the shorty manifold. Then I saw that Precision now offers a 1.05 ar v-band housing.

So, can anyone give me some advice on what kind of improvement (or not) switching to a 1.05 AR housing would give?
And how much of a difference it would make with the tune? Would it likely need more or less fuel? Ignition timing?

How much boost you are running?
Water injection? What fuel?
The bigger rear end will help, but if you are running too much boost for pump gas it will detonate.
I know someone more knowledgeable will chime in.

Pump gas(93 octane) 50/50 water/methanol injection. 18psi.

Scouring through many build posts it seems that people with .82ish turbine housings get 400-420whp or so, and with 1.05 it's closer to 500. Everything was done to support 500+, except the .82 A/R

The 1.05 will definitely help. Good luck, man.

Is that 0.82 a T3?

Either way it should help out. Precision usually sizes their turbines on the small size compared to BW. So you have a turbo with a relatively small sized turbine with a small a/r on an engine that needs to breathe..

PTE 6266

• Turbine Wheel Exducer: 66mm
• Turbine Wheel Inducer: 74.17mm

BW S362

• Turbine Wheel Exducer: 68mm
• Turbine Wheel Inducer: 76

.82 on a rotary??

You will like the larger exhaust housing, in the same way that Captain Hiller liked the alien ship from Area 51 in Independence Day.

you have a flow restricted system that will be an engine killer if run long enough.

Strokercharged asks the right question... is it a T3?

according to the catalog Precision only makes the .82 in a T3

a T3 should never never be anywhere near a 13B-REW as it has only 4.14 sq inches of inlet V a T4 at 5.5.

your motor is breathing thru a straw. i bet your back pressure at 18 is way more than 40 psi and your egts are probably 2000 F.

"Dave" is spot on... the system is restricted

please review the "System Design Sections" of my site

http://www.colemanprecisionrotaries....em-design.html


you need to do whatever you can to remove the T3 flange and replace it w a T4.

Precision T4 hotside options are .84, 1.0, 1.15 and 1.32. pick the 1.0 for your purposes. you will think you have a different engine in the car.

what size wastegate/s?

what is the I D of the runners on your manifold?

with a proper setup and tune the 6266 will make 550 rotary rwhp.

The Turbine housing is the .82 V-band in/out, which I understand is considered in the T3 family.
The 1.05 A/R housing (THV5S) that we are looking at is supposed to be a bolt on replacement.
The manifold/kit was built by Sean at A-Spec. The primary tubes are very short, and about 2"dia.
Wastegate is a single PT 46mm unit. I expect as the exhaust housing flow capacity is increased, the size of the wastegate will need to go up at some point.

Switching to a T4 would require major rework/replacement of the manifold, and just going to this 1.05 housing could be done in an afternoon. How much of an improvement do you think that would be? And by freeing up the hot side, what changes would I expect to have to do to the tune on the Haltech PS1000?

Here's a couple pics from when Sean was building it.

https://cimg8.ibsrv.net/gimg/www.rx7...723d7c7ba2.jpg
https://cimg0.ibsrv.net/gimg/www.rx7...af5fd0f13d.jpg

looks like a 3 inch I D on the V band in the picture. Precision lists a four bolt T3 discharge flange and a 5 bolt (for a Ford internal WG) as well as a T3 V band. they do not disclose the I D of the T 3 V band hotside. if it is 3 inches, which would mate with your manifold, that would give you plenty of area... 7.07 sq inches. this does not change the fact that the hotside is a T3. i am sure you know that a 1.0 T3 and a 1.0 T4 are vastly different as to flow. the number relates the radius to the diameter. you are probably O K with giving the larger T3 a go as it is your most simple and inexpensive possible fix.

i built a twin turbo (Garrett TO4E 44) manifold and ran it for four years, 10,000 miles. i had T3 hotsides. i started w .83 and ended up with 1.05s... but there were two... one for each rotor. i found a fair amount of backpressure with two .83s and less w the 1.05s. each had it's own 3 inch downpipe.

if you feel up to it i would be interested in the actual I D of your runners and the I D of the inlet on your hotside. if either of these is small it does change the situation as to max flow. i also suggest that you add a 1/4 Mica shield between your hotside housing and the motor as a turbo blanket won't get it done since your hotside is close to the runners. turbo blankets lower underhood temps but do not significantly impact the massive heat (1800 F) from the housing. Mica eliminates heat radiation.

The inlet flange is 2.063"id (as per specs found on PTE website) and the down pipe is 3".

Right now I'm just gathering info. And it sounds like the best course of action would be a full T4 setup. But we may in fact go the 1.05 housing route. I'm thinking I'm going to put a pressure tap in the manifold first, so I can check the back pressure (map/emap pressure ratio).

As far as heat management I already installed a stainless heatshield on the turbine, and an inconel heatshield on the LIM.

here's a picture
https://cimg2.ibsrv.net/gimg/www.rx7...fd0b99344c.jpg

good catch on the site...

the (total) intake area into your hotside housing is 3.33 square inches.

each (single) 13B-REW exhaust port is 3.04.

as mentioned, the entirely inadequate rectangular T3 has 4.14 and a divided T4 is the rotary friendly fit at 5.5.

given the intake area and the need for lots more flow (around 30%) to make the same power as a piston engine as well as approx 200+F (higher than piston) exhaust gas temp i would be inclined to roll up my sleeves. your engine will thank you.

before getting into manifold modding i would make sure the I D of the runners is at least 2.0 inches. numerous manifolds were made of 1 1/2 pipe which is 1.90 O D but 1.61 I D. the 2.04 inch area puts the brakes on flow at 400 rw rotary hp causing higher EGTs, significant backpressure and a clamp on power.. sort of O K, back in the day, for the 370 rwhp GT35s but not a fit for modern turbos.

you mentioned tune w a proper hotside versus what you have. of course tune is very important to get right and i applaud you for using AI... what will happen is you will find your motor will be visiting areas of your map previously not logged. earlier spool and higher rpm. you will be decreasing backpressure and also losing exhaust being swept into the next intake stroke. look at a current log and make sure adjoining areas to what has been logged contain injector ontimes similar to what has been logged.

you are going to be shocked going to a T4.

BTW, i did a comparison between a .91 and 1.0 Borg Warner hotside last year. (SX-E 62). i was surprised how little difference although the 1.0 came out on top for me. the .91 made very good power at 8850, not a lot of power drop off from peak torque at 6450. EGTs were lower by 60 F w the 1.0 and backpressure dropped 15%. spool seemed the same.

i have a mild street ported REW with a GENII 6266 .84 T4 hotside.... we ran out of turbo at 16PSI @ 393whp. same issue. i just purchased the 1.00 T4 Divided and will be installing that soon.

I'm still trying to decide whether to go with the 1.05 v-band housing, or go ahead and upgrade to a T4 divided housing and matching manifold.

Once you get that housing changed, let me know what differences it makes to the tune.

V-Band is always the way to go.

How is the 1.00 working out for you?

i've been too busy to install it and get it re-tuned, sorry :(

WHAT! Too busy.......?

I'm still plotting this upgrade, and am definitely interested in your results.

Hopefully you'll find time.

unfortunately it probably wont be until November

regardless, i can guarantee you that 1.05 hotside should give you the results you're looking for. really its all going to come down to how much you're willing to sacrifice spool time.

What is funny is, RICE RACING used to say that larger ARs would actually decrease spool time because the engine could breathe better.

He was a big fan of 1.32s on street ports.

I wonder if there is a threshold where a bigger AR would spool faster?

in general, if a part, like a turbine housing is way too big or way too small, taking a step closer to the ideal size will probably help everywhere. once you get closer to the optimal size though, then you will start to see it act like you would expect.

for example, lets just say that the optimal turbine housing is a 1.32, and the .82 is way too small. putting the 1.0 on there is still small, but it is a better fit than the .82, so it is possible that it will spool better. another example is like a stock FC turbo, its so undersized that you can switch to a full T4 and not really loose any spool...

My line of thinking follows yours. It's possible for the turbine housing to be so restrictive, that it hurts spool.

I'm waiting for an opportunity to actually measure backpressure with this .82 housing. The discussion with the owner is leaning more towards a T4 divided upgrade. but we're not there yet.

Still need input on how this change will affect the tune.

On the other hand, the original exhaust manifold looks like it would be great for someone who wants 350rwp on a small turbo. For instace, one could re-flanged it for used Inycar efr 7163 v-band and reflanged the wastegate for a 60mm one.

Problem is, not many FD owners want 350rwhp single turbo since it is so easy to make that with the stock twins.

But, it could be run on stock fuel system and rom tuned ecu up to ~14psi which would be cool.

You should check if that manifold will fit a small turbo in an rew swapped rx8, because it looks like it would.

It seems to me that there are too many generalisations made about what flange/pipe size is ideal without considering how much flow has to go through it.
Firstly the difference between a T3 and T4 turbine housing is only in the size of the entrance to the housing. The rest of the housing, where it necks down to form the volute is identical either way. So IMO, a T4 is only justified when the pipes going to it are too large to get an efficient transition down to a T3. In a high hp 13B , that would always be the case so I guess the point is moot.
Also , when considering size of pipes to the turbine, surely the method of wastegating is relevant as is the turbine size and AR. An internally wastegated turbo must need larger pipes to the turbine than an externally wastegated setup would. A larger turbine must also benefit from larger pipes, as would a turbine with a larger AR.

It seems that the T3 and T4 nomenclature does cause a certain confusion.

I think way back when, T3 and T4 designated certain frame sizes, but now you can get a lot of different turbos of varying frame sizes with whatever mounting flange you want. So then it comes down to packaging, and optimizing flow configuration into the the turbo and wastegate. In my instance, having a 2" id v-band flange makes it necessary to abruptly merge the two exhaust streams at the flange. I'm still not certain just how much restriction this causes, because the .82AR housing is really restrictive. The thought of leaving the manifold as is and upping the AR to 1.05 is very appealing, but would that then reveal the restriction at the manifold merge?

Now that I've really examined the issue, It's clear that the twin scroll configuration has benefits beyond just flow. as outlined in the SAE paper from Mazda about the T2 twin scroll this certainly can't be discounted. But how big is the gain?

If you think of the exhaust as a static flow, then it would be easy to view the merge as a huge restriction. But, the flow from each rotor is pulsed, and as such the velocity through the merge at different times may actually contribute to some scavenging effect. And if that's the case, the gains from going to a twin scroll may be less significant.

This would all be a lot easier if we didn't have to leave the air pump in place for visual inspection. As it is, even the current configuration doesn't have much room to spare. So I'm not even certain I can make a twin scroll T4 fit without losing the air pump. My friend, the owner of the car, seems to leaning more towards T4, so at some point I may be elbows deep in my first turbo manifold build.

Then there's the tune.....

Just wanna throw this out there since it's somewhat relevant...

T3 Turbine Housings/Exhaust Manifolds can be ported to a T4. There's a short porting guide on Full-Race Motorsports.

Essentially, lay the T4 exhaust gasket on whatever side you need, bolt it in (or just tape), and gasket match. You're welcome, now you have T4.

I don't think the V-band flange wouldn't be a good candidate.

Huh? I'm referring to converting a T3 to T4 by means of porting. They use the same bolt pattern and material on the turbine housing (and usually manifolds) can account for this without issue. More flow = less backpressure = safer power.

I'm just talking about this:

https://cimg9.ibsrv.net/gimg/www.rx7...451755d54c.png
https://cimg1.ibsrv.net/gimg/www.rx7...5c73cfe43f.png
https://cimg2.ibsrv.net/gimg/www.rx7...b70931e944.png

Yeah, but the manifold he has is actually a T2/T25 with 2" ID V-band (rated T3 because it flows as much as standard rectangular open volute T3).

Question is, can two 2" runners merged int 2" V-band support enough flow to warrant switching to 1.05AR housing.

I say, it will be an improvement over the 0.82AR.
However, even more improvement will be had with a manifold/flange more suited to his power goals.

Ideally though one would run 2.5" tapering to 2" runners merging into whatever flange gives you the same area as two 2" diameter pipes. If you can avoid it you dont want to try to merge and increase velocity with smaller diameter in the same short lenght of flange area. Better to increase velocity gradually in runner taper and then turbo volute and merge as cleanly as space allows as well (high angle collector with low turbulence).

But the fab work is undeniably gorgeous and the design elegant. Id be of a mind to just go with whatever your man who is doimg the work has planned and see how it goes.
Just going off my uneducated intuition, it looks like it would be amazing as a low(ish) boost, super fast spooling beast that will still flow up top given the massive wastegat priority.

Look to what HKS used for their T04Z kit as it is sizwd for the power you want.

Early T4 divided and later T4 V-band
https://cimg8.ibsrv.net/gimg/www.rx7...cc6af60a4b.jpg
https://cimg7.ibsrv.net/gimg/www.rx7...41be3eaab4.jpg
https://cimg5.ibsrv.net/gimg/www.rx7...21eeb8cfcf.jpg

I assume you are talking about the current setup from the photo above. I agree it's beautiful. Very direct energy transfer, compact, as you said, "elegant". But really, the spool is not as quick as you'd expect, and it just won't get much past 400rwhp.

I've been searching intently for examples of T4 fitments that would allow for the retention of the air pump, and have recently "discovered" the HKS T04Z setup you posted. It looks to me like this is "proof of concept". The T04Z is a similarly sized turbo to the PT6266, and it looks to fit in the required space. I think the wastegate priority looks less than optimal and doesn't really provide for the isolation of the exhaust pulses for the true twin scroll effect.

I think a shorty T4 manifold like this that implements a wastegate design similar to what Howard Coleman uses on his setup may do the trick. But the proof would be in the pudding.

the HKS V band is for the T51, which actually did fit with the airpump, and was even CARB legal.

the HKS To4S manifold is the cast divided one, and it also for sure fits with the air pump.

the HKS To4Z manifold is the flanges stainless, and the kit doesn't use the air pump, but its probably really close. Manifold is short, because short is better

https://cimg4.ibsrv.net/gimg/www.rx7...7903c553a7.jpg
https://cimg8.ibsrv.net/gimg/www.rx7...d9c915e0fa.jpg


Wastegate placement/priority is a compromise.

Above is the FD T04Z manifold I used on my FC when I switched to the EFR 7670 turbo. I modified it for the two 45mm wastegates and changed the WG inlet angle for higher priority. Issue I then had was that when the wastegates were cracked open the flow and pressure of the exhaust would push them open further in the high rpm and boost would drop.

Woyld have had to plumb boost to the top of the actuators to get the boost flat. Interestingly, when I pulled the WG line off the actuators altogether the exhaust pressure alone wasnt high enough to push crack the wastegates open.

I believe the HKS T04Z came with 3 different stainless manifolds over time.
Divided T04 with square flange wastegate, divided T04 with V- band wastegate and V-band T04Z with V-band wastegate. I have seen posted pictures of all three from members who have the T04Z kit.

Thinking in terms of static pressure, it's easy to simplify the dynamics of an exhaust stream in our mind. But we need to realize how much kinetic energy is involved. The static pressure was acting on the surface of the wastegate valve only until the valve opened and the exhaust started moving. Then the even greater kinetic energy of that high velocity flow took over and the spring couldn't overcome it.

Exactly, wastegate placement/priority is a highly dynamic situation. Different set-ups will want different variations of WG size, position and priority to reach their goals.

As I learned coming from a set-up with same size turbo as the efr 7670 with a single 60mm single wastegate where could not fix boost creep until I ported the manifold and turbo bigger to reduce exhaust velocity. Then I kind of overshot on WG priority on the EFR because I was so afraid of boost creep.

I've been searching so hard, my head is numb!

So, Turblown has pictures of a T4 IWG turbo mounted to an engine with the air pump on it. Their "shorty" manifold moves the Turbo farther forward, but it still has clearance.

Now I have reasonable confidence that this configuration is doable.

The attention now turns to the wastegate.

Typically with a twinscroll setup, a dual wastegate setup is used. However I’m thinking of going with a single wastegate that has a divider all the way to the valve.

I found posts by Blue TII that highlight his attempt at this arrangement. He used a modified turbine housing that had a IWG, and converted it to EWG. This was a very forward thinking project. Unfortunately there were problems with the divider. I think this was more due to his unique configuration. I have seen a couple instances of this configuration with tubular style manifolds, with only one other reported failure (that I found), and I think that manifold did not look like it was constructed well.

Then it comes down to, what size? I see that Howard Coleman is using a 60mm gate. But his manifold, by his own description, is not designed with wastegate flow as a priority.

The wastegate we are currently using is a 46mm Precision Turbo unit. It has controlled boost well, except when the set screws came out that hold the valve stem to the diaphragm. Because the divider splits the area in half, even more when you account for the area of the divider itself, I was concerned it might need to be bigger. But when I draw up the opening and measure the area, each of the sides are about 43% the area of one side of the divided T4 flange. The EFR internal wastegate looks small comparatively. As long as I make a good flow path, I think the 46mm will do the job.

Opinions?

waste gate sizing is tough!

it depends on the flow of the engine, and flow of the turbo, and the boost you want to run, and then manifold design is a factor too..

for instance a stock FD has a perfectly adequate wastegate, but when you add flow (full exhaust), and try to keep boost the same, suddenly the wastegate isn't adequate, and needs to be bigger. however if you wanted to run higher boost (.6 to .8) then the wastegate is fine again.

There used to be the concept of "free floating" turbos, where there wasn't a wastegate at all. Your boost was determined by the exhaust housing.

It's technically the most efficient way to do turbocharging, but not the best way in terms of engine response.

That turbine is still a T4 , T3 has a different bolt pattern to that. However , for some reason B/W don't port some turbine housings out to the full T4 opening sizes and leave the end user to do it for themselves.
Found this note on one resellers website :

That's my exact point. You can CONVERT a T3 Turbine Housing (as pictured in what I posted) to a T4. You also quoted my text written on Full-Race Motorsports. Awesome. :icon_tup:

Ok ..gotya ... It's just that , the way I read your first post made it sound like T3 and T4 have the same bolt pattern ...which they don't.

It's official
The T4 divided upgrade is underway!
https://cimg4.ibsrv.net/gimg/www.rx7...a73822d4e2.jpg
The manifold build thread will follow soon

excited to see the numbers.

i still haven't upgraded to my 1.00

But,
but, I was waiting for you...

Got my first real blast with the T4 divided 1.0 housing, only 11psi on the spring, Captain Hiller would spit on that alien junk....

just linking the manifold construction thread for easy continuance:

https://www.rx7club.com/single-turbo...hings-1143222/

you did a great job 👏 a dyno update would be nice to see.

​​​​​​.

just did a run today and have some data to share.

https://imagizer.imageshack.com/v2/1...924/OnD3PF.png
the data point is the last prior to a TPS downtick. as you can see i am at 20 psi and my EMP/EMAP is 24.9 at 6457 rpm with my EFR 9180. up to 5687 i had more boost than backpressure. there are many factors that influence EMP. intake and exhaust ports, turbo manifold (big influence) and hotside system which includes divided or V band (big deal on a 2 rotor rotary), turbine wheel size, configuration, material, hotside housing and exhaust. for many, the hotside housing and turbo selection are easiest to effect.

i did a back to back comparo in 2018 (up to 9000 rpm) using a BW SXE 62 between the .91 and 1.0. i was surprised how little difference there was as the .91 made very good power at 8800! EGT was 60 F lower with the 1.0.

i will probably be buying a G35 1050 after i finish w my 9180 and will look forward to comparing it to my present turbo.