Hello,

I am getting ready to purchase the Borg Warner S256 extended tip turbo, but I have seen it comes with 1 of 2 turbine wheels.

There is a 69.5MM IND Dia and 61.5MM EXD Dia or a 74MM IND Dia and 64MM EXD Dia. I will be getting it with the Bullseye Mitsubishi bolt on housing, which is a .55 AR housing.

I just want some opinions on which wheel you guys would go with and whether or not the larger wheel is even worth it in this situation. I would like to see some vendor responses as well.

ExtremePSI has the option to choose either wheel on their site and they are listed that way on bullseye's site as well.

Josh

What are your goals?

The bigger turbine wheel is more laggy, but provides more hp per psi of boost. Ideally, to match a compressor wheel to an turbine wheel their diameters must be w/in 10% of each other; the closer to the same diameter the better. This rule of thumb more favors the larger wheel. If you're leaning to the 550 hp end of the compressor rating then I'd look at the bigger wheel. If you're leaning toward the other end, then. . .I'd get a cheaper turbo .

The turbine housing can flow enough for the compressor, regardless. The Exducer diameter affects the flow of a turbine housing as much as A/R and nozzle area.

Blowing open the wastegate would be the problem here. A larger wheel lowers pressure in the turbine houisng and minimizes this symptom. Going external is ideal, but a larger turbine wheel and a GOOD wastegate actuator and/or extending the wastegate arm (not talking about actuator arm, of course) to create more leverage has helped me.

I was running the smaller wheel in the bolt-on housing, saw 30+psi before 4k and ran 11.9 @ 119 on pump at 27psi. Bear in mind that the small wheel is about the size of a P trim. I think it's a better match for a 2.0 than the big wheel.

Why is there such little input about these turbos? I entered the bullseye turbo giveaway and am one of 39 finalists, but either way, win or lose, I'm probably getting an S258. It is kind of a turn off that besides Steve's S256 I haven't heard anything about them being used on DSMs.

I already have an Tial external wastegate and O2 housing for it on the way. As a matter of fact everything is ordered for the swap except the turbo. I am running E85 and hope to max this turbo out. I am trying to go for efficiency and a properly matched up turbo for a 2.0. Steve I have read your posts on DSMLink forums and seen your logs already. At this altitude (6000FT) a lot of turbos fall out of their compressor maps easily. I am also trying to figure out how that would apply with the turbine options of this turbo. I am leaning towards the larger wheel right now.

Josh

Steve93Talon said:

I was running the smaller wheel in the bolt-on housing, saw 30+psi before 4k and ran 11.9 @ 119 on pump at 27psi. Bear in mind that the small wheel is about the size of a P trim. I think it's a better match for a 2.0 than the big wheel.

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I think you have that backwards the larger one is the size of a p trim which is a 74mm/64.5mm wheel. I would get the largest turbine wheel you can get with you getting a bolton turbine. The better your hotside flows the less boost it will take to make the same power.

I have a S258 and i like it. spool is fast still im getting 17 psi by 3400rpm. With a huge FMIC and 3 inch intercooler piping and a stock bottom end low compression. The turbo is very loud on the comperssor side that is the most noticeble thing compared to a garett.

93AWDTalon1 said:

I think you have that backwards the larger one is the size of a p trim which is a 74mm/64.5mm wheel. I would get the largest turbine wheel you can get with you getting a bolton turbine. The better your hotside flows the less boost it will take to make the same power.

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Yea I agree here:

Turbine Wheels
Millimeters to Inches conversions

Blade shape affects flow and spool as well, however. But, I was still under the impression that these turbos are well built and the wheels are well matched. Thus a wheel that would flow more than a p-trim would be improper for a 550hp max compressor.

TurboAnything said:

I have a S258 and i like it. spool is fast still im getting 17 psi by 3400rpm. With a huge FMIC and 3 inch intercooler piping and a stock bottom end low compression. The turbo is very loud on the comperssor side that is the most noticeble thing compared to a garett.

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Which turbine wheel do you run?

dsm-onster said:

Blade shape affects flow and spool as well, however. But, I was still under the impression that these turbos are well built and the wheels are well matched. Thus a wheel that would flow more than a p-trim would be improper for a 550hp max compressor.

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I may agree with that if this had a T3 turbine but with a bolton housing with a std a/r you want to get most flow you can get from the turbine wheel to make up somewhat for the small a/r.

You see that is where I am stuck. Which wheel would be better in this bolton housing. The larger wheel will obstruct flow more, but will its gain be enough to counteract that in this housing? I know there has to be a formula for figuring this out. Then again, why would they even offer this wheel if it do not work with the housing. Whatever version I get. I certainly have the supporting mods and tuning experience and help to find out what it can do. I will post back results. I have been running an EVO 3 to the ragged edge.

Josh

93AWDTalon1 said:

I may agree with that if this had a T3 turbine but with a bolton housing with a std a/r you want to get most flow you can get from the turbine wheel to make up somewhat for the small a/r.

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A small a/r number for one brand turbine housing may denote a totally different volute volume than another manufacturer. Also nozzle width has a large impact on flow/spool. And this changes from one brand to another. A BEP .55 a/r housing flows a bit different than a pte .63 a/r housing. And has been proven to flow quite well. I'd dare say better than the LARGER a/r pte.

Straight from the first sticky in this very forum by Brian Wilson of Forced Performance: Part II: Turbine Housing A/R

I don't think the turbine housing is a bottle neck. I DO think going w/ the larger turbine has much more affect than "somewhat" on flow of the whole turbine. For example: a t3 stage 2 wheel is found on a stock turbo coup, volvo, gn, 280zx. This is often accompanied by the .63 a/r housing. I've never seen one of these turbos go higher than 320 hp. and thats w/ the GN running the larger stock t4 compressor. Now swap in a t3 stage 3 turbine and that same .63 a/r housing can flow up to 450 hp easily. I've seen it do much more.

AWDer said:

You see that is where I am stuck. Which wheel would be better in this bolton housing. The larger wheel will obstruct flow more, but will its gain be enough to counteract that in this housing? I know there has to be a formula for figuring this out. Then again, why would they even offer this wheel if it do not work with the housing. Whatever version I get. I certainly have the supporting mods and tuning experience and help to find out what it can do. I will post back results. I have been running an EVO 3 to the ragged edge.

Josh

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A larger turbine wheel will do the opposite of getting in the way of the flow. This is one reason for the lag but better flow.

I've heard some good things about the BW turbos in the BEP housing. I've heard good things about the BEP housing itself. And I've seen the BEP housing flow well for t3 stage 3 wheels, t3 stage 5 wheels, and o & p trim wheels. Mine does just fine for 450 or so hp. The achilles heel of the housing is running an internal gate and running enough flow to blow open the large flapper. Like I said, I've seen a BEP housing around a larger diameter wheel flow just fine. I'm sure the larger wheel flows more than my t3 stage 3 and this wheel does good in my BEP housing. The blowing open thing is not because the exhaust manifold pressure is too high (which would suppose a poor flowing housing/turbine), but because the hole is too big. It is meant to be a universal housing, so aspects are overbuilt.

Sorry it took me so long to see this guys

The S256 is only available in the 64/74 combination in the bolt up dsm housing. The other size is for a housing that is used on john deere's and has been used on some indian motorcycles. It is not available so I guess that pretty much makes up your mind

Wayne

Sounds like the larger turbine wheel is the way to go. Problem solved. TurboAnything, how do you like the S258. It has a slightly narrower compressor map, which is bad for us high altitude guys, but it has a 2mm larger compressor inducer and it looks to be about 3 more lbs/min of air.

Edit: You posted while I was. I wonder why ExtremePSI has both listed in the bolton.

Here comes a stupid question. Is the turbine housing for external sealed and setup for a manifold mounted wastegate or open for a O2 housing mounted external wastegate.

AWDer said:

Here comes a stupid question. Is the turbine housing for external sealed and setup for a manifold mounted wastegate or open for a O2 housing mounted external wastegate.

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Extreme PSI must have copied the chart on their website because it does list both. I attribute that to bullseye's website because it is not a very good site for info about their products. I guess that is what we are for though

I have an S256 in stock still on special right now. They normally ship with an open wastegate hole set up for the o2 mounted wastegate but for an extra $25 they will weld in a puck so you can run a manifold mounted o2.

I have an O2 mounted external, so the open setup is perfect. What is your opinion on the S258 and in comparison to the S256? I am looking at buying it today or tomorrow.

AWDer said:

I have an O2 mounted external, so the open setup is perfect. What is your opinion on the S258 and in comparison to the S256? I am looking at buying it today or tomorrow.

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The S256 supports 300-550 HP
The S258 supports 350-600 HP

Most people who have street driven cars like the S256 but the S258 is just a little bit bigger for that extra 50hp. Depends what you wanna do. Street driven and not looking for over 550 I would take the S256 for quickest spool time.

Somewhat on topic, somewhat off: Would anyone care to estimate the 2.0l pump gas HP of the 256net (non-extended tip) on an average tune? Something a little more specific than ~300-500?

It depends on how much boost you plan to run, your current mods, and how well your tune is. That is just the power range that bullseye recommends to run them in. The extended tip will outflow the non extended tip by 6-8 lbs/min above 15psi.

By the way Jon I saw you got that turbo today, how do you like to looks of it? I think you will like how it performs a little better than the vtrim.

Wayne

On a side note I am glad this thread got started because there IS such a lack of information on these turbos especially in the dsm community. These are some awesome performing turbos and I know they will catch on quickly when a few people get some miles on them. I am almost done swapping my FP3065 with a Bullseye S362 and I am gonna try and get a good comparison of those also.

What size housing are you using in the comparison for the S362?

wt71gas said:

The S256 supports 300-550 HP
The S258 supports 350-600 HP

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Something else to consider - The S258 also uses the larger S300 style compressor housing with 2.75" outlet. The 256 housing will clear the waterpipe and has a 2" outlet. Bullseye will soon be shipping a 258 with the 256 style comp. housing though.

I am going to be using the BEP bolt on housing with the S362. There is only one option on wheels for that to in the bolt up.

here take a look at the two turbine wheels i have them posted already http://www.dsmtuners.com/forums/showthread.php?t=205478&page=6 this is a smaller turbine in a 64/74 housing