2Lucky2tha7

iTrader: (3)

I understand that this can be like comparing apples to oranges here, but in terms of finding a somewhat comparable volute opening, what size t3 a/r would compare to a p-trim 1.00 a/r t4? Would a 1.22 a/r t3 be good enough? I'm asking because the BW s200sxe (s257) has turbine housing options that use a t4 flange but have t3 volute runners. It also uses a smaller 70/61.5mm turbine wheel as opposed to a t4 p-trim turbine wheel that is sized at 74/65mm (I was originally looking for something around a 60-1). I'm still trying to determine if I can reliably use a Borgwarner S257 for a longterm street application on a ported block.
Thanks.

BLUE TII

iTrader: (9)

A/R is the same through the range of various flange size turbo exhaust housings since it is a ratio of exhaust area to radius.

If you take a T6 1.00AR turbo and cut the exhaust entry down to where you can weld a T3 flange on it it is now functionally the same as a 1.00AR T3 turbo.

Now in reality, the 1.00AR T6 housing was probably set-up for a larger exhaust wheel so you would have to bore the T3 1.00AR T3 housing to fit the larger exhaust wheel to get the same flow through it as the T6 1.00AR housing.

-------------------
Your turbo manifold primary tube and turbo flange dictate whether you will use a T6, T4, T3, T2 flanged and in extreme cases can affect ultimate flow enough to limit the total exhaust flow of the turbo.
Example: you wouldn't put a stock S5 TII T25 sized exhaust manifold on with a T6 sized turbo trying to make 600rwhp.
-------------------

There is some leeway on manifold primary tube sizing with rotaries.
Recently Turblown has really shown this by using a smaller than usual for rotary 1.5" nominal pipe size runner manifold (typically rotary T4 turbo uses 2" nominal pipe size).

Better spool is realized with smaller runner diameter and for this change at least the smaller size does not seem to impact top end flow on T4 sized turbos (maybe it would on T6 sized?).

BLUE TII

iTrader: (9)

So...

I didn't answer your question at all, because in your application you are trying to figure out what the smaller exhaust wheel in a larger A/R housing will equal the larger exhaust wheel in a 1.00AR housing.

This chart from BW should help you figure that out. It lists exhaust wheel major diameter first and then exhaust housing A/R.

BLUE TII

iTrader: (9)

See how important exhaust wheel size is!

edit- included relevant exhaust wheel sizes and matches below after a quick google search on P-trim specs.

BLUE TII

iTrader: (9)

So, sadly according to the BW chart-

the smaller 70mm/61mm exhaust wheel you have in any housing available will not match the flow potential of the 74.22mm/64.6mm P trim exhaust wheel in the 1.00AR housing.

Unless BW did something to really increase the flow of the turbine wheel compared to the P-trim wheel (like leave a fin or two out).

But the 70mm exhaust wheel in the 1.22AR exhaust housing gets you to the same flow as the 74mm exhaust wheel in the 0.92AR exhaust housing which is probably good enough.

BLUE TII

iTrader: (9)

My experience with my 1.05AR T4 EFR 7670 on my TII is the smallish 57mm/74mm compressor wheel's 64lbs/min airflow is going to limit top end power more so than the 70mm exhaust wheel or housing AR (within reason).

Once you hit ~450rwhp on the compressor it has no more flow to give on a rotary. That will happen around 20psi and 6,000rpm.

So, I would say the compressor is the real limit on top end power with that turbo.

BLUE TII

iTrader: (9)

Also, I went from P-trim 60-1 that you first selected to my EFR 7670 so let me know if you have some comparison questions related to the two.

My p-trim 60-1 was in stock S5 TII T25 sized 1.00AR exhaust housing with stock manifold and turbo entry up to 60mm external WG ported to T4 size and the smaller HiFi compressor cover taking ~ 10% flow off the peak lbs/min flow.

To give you an idea on the crazy turbo/housings/manifold combinations possible...

2Lucky2tha7

iTrader: (3)

Thanks Blue TII, your help is greatly appreciated! Originally the block was ported for a higher horsepower range (originally 450rwhp), but that has since changed over time, so getting a good turbo match makes it harder. The goal is really to have a great street setup in the 300 - 350 rwhp range with hopefully a wide, use-able powerband, so maxxing out the turbo (near or above 400rwhp) is not a concern. I just don't want to have too much back pressure and if it falls off a bit after 7k rpms would be tolerable (unless a larger sized t3 volute A/R housing would help). And the forum member lOOkatme advised me that since the air is thinner up here in Colorado at 6,000' and up, that exhaust velocity(?) is diminished as opposed to down at sea level, so I should be able to get away with the smaller turbine wheel that the S257 has. So with that in mind, do you think I could make the s257 work reliably and being decently matched to this setup? And if so, should I stick with a 1.00 housing, or use the 1.22 housing that FullRace recommends on their website? I plan on opening up the port runners (but only where the turbine flange meets the turbo manifold) on the turbine housing entrance flange so as to match the t4 sized manifold and thus lower the possibility of any extra backpressure/turbulence where they meet. Again, with that being said, what's your take on all this?
Thanks again.

2Lucky2tha7

iTrader: (3)

I went back and JUST noticed the last sentence here and that helps greatly and I think would be good enough. I was also first set on getting a BW s360 with a 0.8+ turbine housing (again, comparing apples to oranges here), but have since chosen not to go that route for several reasons (even though it's a great turbo. it just doesn't suit my goals and instead overshoots them). So getting something equivalent to a p-trim with a 0.92AR would be good enough I'm thinking.

BLUE TII

iTrader: (9)

300 - 350 rwhp range with hopefully a wide, use-able powerband

This is the most important info when choosing the exhaust housing.

Since you aren't trying to max out the compressor flow, I wouldn't use that largest 1.22AR exhaust housing.

I personally would use something in the 0.90AR to 1.00AR for those goals with that turbo and 12-17psi boost.

Even a 0.80 to 0.90 exhaust housing you would just be trading more response for a little top end power (not that much top end power at the 300rwhp level, but you might not make 350rwhp at that altitude on that lower pump gas boost).
----------

And yes, I think it is a really good turbo for the application.

I would take it over the 60-1 at the altitude you are at because the 60-1 is most efficient at really low pressure ratios (14psi at sea level) and the 76mm BW is most efficient at higher pressure ratios (22psi at seal level).

BW Engineer Kurt Henderson says its 1-2% turbo speed increase every 1,000ft elevation change. Colorado mean elevation is 6,800ft..

If you look at the 60-1 compressor map you are already at the top of the peak efficiency island at PR 2 or 14.7psi and ~92,000rpm. That would shoot up up to 96,000rpm at 1% speed increase and midway through next lower efficiency island already. 2% speed increase and you are at 102,000rpm and midway though the 3rd efficiency island.

Not the worst, but we are calculating for only 14.7psi gauge boost.

If you look at 76mm BW compressor map you are just below the lower tip of the peak efficiency island at PR 2 or 14.7psi and ~80,000rpm at sea level. Either 1% or 2% speed increase from 6,800ft elevation will get you into the peak efficiency island.

This is a gross simplification, because it doesn't plot the engine airflow requirements per rpm.
But it does show how the 57mm/76mm BW compressor wheels higher PR efficiency is a liability at low boost at sea level compared to the 57mm/76mm 60-1 compressor but an asset for low boost at 6,800ft elevation.

Edit- lost my starting point on the math.

BLUE TII

iTrader: (9)

T04B 60-1 Compressor map (57mm/76mm)-



EFR 7670/S257 FMW Compressor map (57mm/76mm)-

lastphaseofthis

iTrader: (8)

it seems to me the latter would have a wider area to be in boost, and the former to have a smaller rpm window of boost. which is exactly what is observed in the real world, is it not?

Tuning4life

iTrader: (2)

for altitude.

You can run a smaller exhaust turbine wheel side if you want at higher altitudes because you still have the same mass air flow out of the turbo. the issue is the compressor side can't move the same amount of air as sea level. so when you run a 15-18PSI boost level your mass air flow (WHP) is a lot lower at altitude than sea level. you push the turbo harder but you have the same mass air flow as lower pressures at sea level. same goes for a fuel system. you can run a 500WHP fuel system on a much larger turbo up here than you could at sea level.

so running a smallish turbine wheel at altitude isn't a huge deal since the compressor won't be able to really push the air flow as it could at sea level. back pressure issues aren't as big of an issue up here as sea level.

If you want to run a 57mm compressor wheel run a billet wheel with a anti-surge housing to extend the efficiency of the turbo as far to the right (more air flow) as possible.

The difficult part about your engine is its ported, and this typically means you have more air flow up top and a smaller compressor wheel is going to have a tough time keeping up.

Tuning4life

iTrader: (2)

I added the efr 7670 at sea level, at 8000 ft above sea level for 17PSI.

the efr 8374 also at 17PSI at 8000 ft. a much better fit.

2Lucky2tha7

iTrader: (3)

To throw a curve ball at the PR aspect of it all (and sorry for complicating matters, but this is why I've been asking for advice) - when I did the math, a PR of 2.00 is only 10 psi up here, and thus a PR of 2.8 is 18 psi up here. I figured this by following this formula:
Current Atmosphere PSI + desired boost PSI ÷ Current Atmosphere (minus) 1 PSI for pressure differential = Pressure Ratio.
Sea level = 14.7 psi atmospheric pressure
6000' elevation = 11.78 psi atmospheric pressure
So.....
(11.78+10) ÷ (11.78 - 1.00) = 2.02 P.R. (10 psi)
and:
(11.78+18) ÷ (11.78 - 1.00) = 2.78 P.R. (18 psi)

Then, BlueTII, you pointed out the extra 1% - 2% turbo shaft speed increase for every 1000' increase in elevation.
I know this all shifts where I would be at on the compressor map. So I figure I'd be between at the most between 2.00 PR up to 3.00 PR (this will shift up towards there when driving up near 10k elevation, or I could just turn the boost down). The tricky thing too is that up here when you see 18 psi on the boost gauge, the ecu is only seeing 15 psi of absolute pressure. So, 13 - 18 psi on the gauge is really only 10 - 15 psi according to my ecu (Megasquirt 2).
So, this is where it got confusing for me.
So, in conclusion (and from my understanding), if I were at sea level and wanted to run...say 12 - 16 psi, I would have to run 15 - 19 psi up here. Not only that, but at a given boost level up here....say...15 psi... the turbo would be spinning anywhere from 6% - 12% faster at that given PR on the compressor map.
Am I following this correctly? And if I can avoid the top end from dropping off, I'd like to. But like I said before, I'd like a wide powerband. Just want to make sure I can size this turbo as best I can given the circumstances.
Everyone's help here is greatly appreciated as well as I'm sure could help anyone else who comes across this thread when trying to size a turbo for higher altitudes.

lastphaseofthis

iTrader: (8)

that has nothing to do with your altitude and everything to do with how you have your gauge vs your pressure sensor plumbed. you should have your pressure sensor and gauge plumbed to a tee going to the same nipple on the intake manifold AFTER the throttle body.
have a boost gauge post turbo pre intercooler and have the gauge in the stock location will cause you discrepancy

this goes to show how you can pick the right turbo and get all the good advice on it, but if you hook up the lines wrong it will never be right...

2Lucky2tha7

iTrader: (3)

That's not even the case, so please don't assume. It's because the boost gauge is relative to AMBIENT pressure and thus sees RELATIVE pressure, but the ecu is seeing ABSOLUTE pressure. I know, because I set it this way. And there's no problem with the lines as they have the same source - which is sourced from in between both barrels at the base of the 51 IDF throttle body where it meets the weber manifold so as to minimize pulsing. And yes, it's after the butterflies. So when my Autometer vacuum/boost gauge is reading '0' up here, it's really reading 11.78 psi of absolute pressure. But when your boost gauge down there reads '0', it's really seeing 14.7 psi of absolute pressure. In both cases, it reads '0'. This is because it's a gauge that reads pressure and vacuum that's RELATIVE to current atmospheric conditions. The Megasquirt II is seeing absolute pressure on the other hand, and hence the difference. Absolute pressure matters because it helps to reference it in terms of pressures at sea level. For example, when one does a compression test on any engine up here, the numbers you get will be significantly lower than at sea level - so if your engine has a compression reading of 115 psi at sea level, up here it will read just a tad over 96 psi. That's a 19 psi loss right off the bat.
It was messing with me at first when I drove out here from eastern PA over 4 years ago, that when I got to Denver, I had to be boosting at 3 psi on my boost gauge just to keep it at the '0' vacuum/pressure mark on my ECU via my laptop. I have since changed it so as to reference it more easily, but I still use a gauge setting for absolute pressure so I can reference it to sea level. So, since combustion chamber pressures are lower up here, one can get away with running higher boost to compensate (which is generally the atmospheric pressure difference - so close to 3 psi higher at my altitide.) This may sound confusing (as it was for me for quite a while up here), but it eventually made sense. It's also why I've been asking for advice in trying to properly size a turbo for up here because I know there's more factors involved than what I was previously accustomed to and I could use all the expert advice I can get.

Tuning4life

iTrader: (2)

you are right. what we have is a MAP sensor. MAP = Manifold Absolute Pressure.


Absolute pressure = Ambient pressure + Boost pressure. My car is the same exact way as yours for reading 3PSI lower absolute when I tune.


so when doing calculations and what you are finding is exactly what I have experienced, tuned for, and why I chose my turbo.


so you have the turbo, you have an intake filter, and intercooler/piping.


You have an ambient at about 11.5 to 12PSI around 6000ish ft above sea level (I live in Colorado springs and live at 6,500FT on the westside).


you have pressure losses across the intake filter and intercooler, call them 2-3PSI in total.


so when you want to run 15PSI, the turbo will be running at 18PSI to get you that 15PSI with the losses before the motor.


so here it is.


PR = 18 + 12 = (30)/12 = 2.5 pressure ratio for 15PSI manifold boost pressure.


you run 18 and its at 2.75 pressure ratio. run the car at an 10.5 ambient pressure at 18PSI it then is 3 pressure ratio for 18PSI boost pressure. thin air makes the car work double as you move up in elevation.


The people at sea level are lucky as hell.


I recommended the larger 62MM compressor wheel to get you where you want to be, I almost ran a 67mm compressor wheel just to be safe I was still in the efficiency range. (efr 9174)


Problem with larger compressor wheels is they are slower to spool up, especially with less mass air flow, on top of that they are easier to surge if you do get them to spool up.


When you do finally run the turbo and it emits hotter air temps because it is working harder, you also have less mass air flow to cool any heat exchanger with, less mass air flow for radiator, intercooler, and oil coolers. so you need to overbuild these to cool everything down. I opted for a dual 25 row oil coolers, V-mount ducted radiator and intercooler and I placed a HUGE air filter in the mouth of the bumper for cold air and lower pressure drop across it (it also filters the air better with the lower pressure drop across it).


On top of it all, your raised your VE of your engine at high rpms. this will want a larger turbo...especially at higher elevations. I am running a 62mm compressor and it does just fine. I have run my turbo to 17PSI and it seems to do well. I am still curious how the 9174 would fair out here or if it would surge.

2Lucky2tha7

iTrader: (3)

Tuning4life, thanks for the input and advice and it's good to get feedback from the forum members who live out this way as well. I originally missed where you mentioned the 8374 being a better fit, and you made a great point about how all the heat exchangers are affected up here. Not only that, but the fact of having a higher VE at high rpms.
However, what I neglected to mention in this thread were the other factors in why I was trying to go this route, hence trying to figure out the best size A/R to go with for an s257 that I was back and forth about getting (which does have a billet wheel and ported shroud btw and rated at 64 lb/min). Granted, the block is ported and that definitely affects everything, but I'm dealing with several limitations.

These limitations regard:
-Budget (like $800, so the EFR's are out of the question),
-The current drivetrain (it's a widebody 1st gen '79 rx7),
-And the current t4 sized turbo manifold that's restricted to a 38mm wastegate size - so no oversized turbo.
Not only that, but to fit a BW s300 series turbo would require a new (most likely custom) manifold since it's a 1st gen) and a larger wastegate. But that obviously drives up cost significantly. And even if I were to try and work with what I have somehow, an s300 series turbo would hit the framerail - whereas an s200 series would clear it. The plan was to take a step back and work with what we've got.

When it was first bought a long ways back, it was running a Turbonetics T04B with a very similarly ported block, and it pulled hard from 3500 - redline and was about 300 at the wheels - and that was great in this car. But that turbo needed replacing anyway and an old BW T04B replaced it and was a step down from the Turbonetics. But that turbo didn't do well at all at altitude and didn't last either. So, I've been trying to figure out what turbo would fit the best given my circumstances. I do think that a high flow/ low boost turbo would work best - one that would be good for 350 rwhp or so and with a similar powerband to what it once had. The trouble is that high altitude conditions change all that. Secondly, as BlueTII posted up and pointed out, the 60-1 is at it's peak efficiency at 2.0 PR - or 10 psi up here (with minor losses in mind. It might even be more like 9 psi). And a 62-1 is just slightly better. I was also hoping to go with a newer/current tech turbo that could run more efficiently and spool up alot better than what my old BW T04B was spooling at up here - which was somewhere around 4300-4500 rpms in 3rd or 4th gear which was pitiful. And I didn't want to go with too big a compressor wheel because not only is spoolup up here been pathetic for me, but it would require a larger wastegate and hence a new manifold and that all drives up cost which can't be afforded at this time due to the turbo not being the only thing that's going to be taken care of.
And this is why I have yet to settle on which turbo to get yet.

That all being said, I feel stumped and like I'm headed back to square one now and not sure what to go with at this point. Granted there are alot of great turbos out there nowadays, but what would be my best bet with a ceiling of $800?
I'm open to suggestions (with the above factors in mind please).

Tuning4life

iTrader: (2)

There are some factors that won't be known till it is tried, but a 64lb turbo at sea level is really a lot less here and if you are hitting 64lbs of flow you are at the limit of the turbocharger.






64lbs at sea level is not 64lbs at altitude.






I would say run a garret turbocharger with a 62mm wheel with journal bearing. you could probably find one used as well. I think the compressor housing is smaller on these units and it should fit. run a GT3582R or something like that...or the GTX model.




Running a 57mm with the ported engine at altitude doesn't seem like a good fit IMO. I know you are worried about spool up, but if you have a good manifold it should be fine.

2Lucky2tha7

iTrader: (3)

You make excellent points and I'm keeping them in mind. And just for the sake of the process of elimination, the s257 has the same compressor setup that Speedjunkie had with his efr 7670. It's similar, just not with the added benefits of the EFR series and he seemed to love that turbo when I read about it on the forum. Perhaps I could just run lower boost overall and possibly have a relatively fast spooling turbo that may get me in the sub 300 rwhp range?
I also forgot - and just remembered today - that since I am soo used to working with later model 13B blocks, that I failed to remember that these older (74-78) 13B blocks have a 7500 rpm redline as opposed to 8500 rpms for the later model 13B blocks due to a heavier rotating assembly that limits higher rpms. So if a particular turbo could get me up to 7000 rpms, that would work just fine.
I have been searching around for even a used turbo for the last 2-3 months now, but I've come up emptyhanded up until now. As for, say, a GT3582, they are all a t3 format from what I've seen - and even if a t4 housing could be bought, they appear to cost a good amount. Outside of that, the only other viable options I've come across would be the Precision entry (E) level series as they also have a billet compressor wheel (but no anti surge housing) - but I'm not sure how relaible one of those would be as opposed to a BorgWarner or Garrett turbo...

Tuning4life

iTrader: (2)

I am friends with speedjunkie. I rode in EFR 7670 car and it is a great set up. His set up is also a stock port engine, and he is switching to en EFR 8374 and I will see which set up he likes more. He is going with a 3.5" downpipe and a little more restrictive exhaust system but I see the 8374 performing great.


Stock ports are great at spooling up a turbo and give some up top, I prefer the stock ports actually, with a ported engine the flow up top is a big difference and throwing on a smaller sized turbo is going to give it a work out. when you drive the car you probably won't notice it, it would only be noticeable from switching to a larger turbo how much you lose on top end at altitude.

2Lucky2tha7

iTrader: (3)

I wasn't aware he was using stock porting at the time. You're right, that does change things. (I just don't want a larger journal bearing turbo to spool up too late at altitude for being a sub 300rwhp street car). Not easy to match with large intake ports. It's also running a 3" exhaust with just 2 inline mufflers.
I did find a TDX61 for sale in my budget ($750). Brand new too, just never installed as the owner sold the car. However, it has a divided 1.15 A/R housing and looks to get full spool by 4500 rpms according to some dyno graphs that Turblown posted up a ways back. Up here I would expect it to be like 5000 rpms. So like a 5k - 7.5k powerband :/
I'd prefer possibly around a 3.5k - 7.5k powerband.
Perhaps if I could find a 1.00 A/R housing for it? But if one costs over $200, that puts me at the cost of a new one anyway :/ Then again, there's the limiting factor of the 38mm wastegate size and not sure if it will boost spike with it. Don't want to get near 400rwhp either as the current drivetrain won't handle that either.
I can say this though - if I were at sea level, the old Turbonetics T04B with an undivided 0.96 A/R tangential housing (not sure of the details though, but the lettering on the compressor housing was in red from what I remember). The car had a great powerband with this porting - full spool (or atleast you felt it suddenly pull hard) by 3.5k and held all the way to redline without tapering off. Ran somewhere between 12 - 14 psi.
But that can't apply up here though. But for reference sake, I'd like to have something close to what it was before or better.
(Within budget though).

WANKfactor

iTrader: (1)

MAMBA Ball Bearing GTX Turbocharger 4" Anti Surge GT3582R + .86 T4 3" V-Band Hsg

BLUE TII

iTrader: (9)

^^^ or roll the dice on a China-charger.

The high altitude will really put it to the test!