As soon as the guys from Full-Race get back from SEMA I will be sending them payment for my new Borg Warner S300SX FMW turbo. So far we have been talking about running a divided 0.91 A/R turbine housing with the flat-tip turbine wheel. I am a little concerned though with the EGT's and backpressure that the 0.91 A/R turbine housing might produce and am questioning whether or not the divided 1.00 A/R might be better/safer choice.

A few details about my build...I have a large street ported engine by djseven, will be running dual 44mm Tial MV-R wastegates and have a full 4" exhaust. I have a single stage boost switch water injection system (water only, no meth) and only plan on running 15-16 psi boost and revving somewhere in the 8000-8200rpm range.

There are two reasons that I was originally planning on getting the 0.91 A/R turbine housing...
1) Because of the extra expansion that you get from the exit of the turbine housing to the downpipe when running a 4" exhaust
2) And the fact that the turbine wheel/housing of the borg warner turbo is significantly greater than that of a garrett turbo with a similarly sized compressor wheel.

Guess I am just looking for other opinions from other who have experience with the BW turbos (this will be my first).

 

you have a 4" exhaust... and your running 16lbs of boost. The least of your worries should be the heat and egt's generated from the a/r choice. Go with the 1.00. It'll give you a little more room to grow. If all you want is oober response...go with the 0.91.

 

I guess I also should have specified a couple of other things.

1) This is a track car build so response is important, but reliability is more important. It is the sustained EGT/backpressure that I am worried about. Also, I really don't want/need any more than 450whp for the track for now (though headroom is nice).

2) I am plumbing the wastegates back into the exhaust, so 4" is nice to have for that.

 

you'll be fine with the 1.0. Your egt's may be slightly higher but people wouldn't run 1.15/1.06 exhaust housings if they were worried about egt's. You have water injection/meth and 4" exhaust.. you'll be fine with either choice.

 

The MVR's are overkill; go with the MVS 38's. What compressor wheel are you going to run? You're more than likely going to want to stick with the .91 AR for your boost level. There's no reason to run larger unless you're planning on being in the 6k rpm area and above. For quick spool and on the go driving you'll be happy with the .91 AR.

What are you doing with the car?
Compressor wheel size?

 

This is the exact turbo...

BorgWarner S300SX FMW Turbo - Full-Race.com

and

BorgWarner Turbo S300SX3-62 S362 BILLET (S300) PN: S362FMW

Compressor: 61.4mm inducer, 83.4mm exducer
- (billet 7/7 blade wheel with extended tip technology)

Turbine: 76mm inducer, 68mm exducer
- "Topping this off is the ‘J type’ turbine wheel, 76/68mm, with an advanced design for high flow and fantastic response. It’s bigger than the competitive ‘Q’ trim, yet responds better than the existing 74/65mm wheel"

 

Here's some free advice. Don't get the billet wheel unless you're looking to run high boost. For you I would just get a standard out of the box S362 turbo and save a little money. It's exactly what you need. Also, I would use the standard 3.5" marmon flange and do a 3.5" downpipe. If they can't help you with a full kit let me know. I can have a complete rerouted kit out in 3 weeks tops.

 

I don't see how you come to the conclusion that the standard S362 is the clear choice over the billet wheel except under high boost.

I created this overlayed compressor map of the S300SX and S362 and plotted some sample data on it. The data is plotted at a PR of 2.2...18 psi at the turbo assuming 2 psi of pressure drop through the intercooler, giving 16 psi of manifold pressure.



All points were plotted assuming 2.6L displacement, 90% VE, and 14.7 psi atmospheric pressure. Also, I calculated all mass flows at the manifold pressure of 16 psi...not the turbo pressure of 18 psi. Here is the output that I calculated:



Now as you can see...even at boost under 20psi...the S300SX FMW has slightly better efficiency than the S362 and spends twice as long in the 76% efficiency island. Now couple this with the fact that both turbos have roughly the same peak flow below 20psi, the S300SX has a surge line that is slightly further left than the S362, and (probably most importantly) that the S300SX has the theoretically lighter weight and smaller diameter compressor wheel (giving it a lower moment of inertia which should yield faster spool and transient response) and I believe the ideal choice is the S300SX FMW.

I was hoping that I could see a dyno graph or two of someone else who has used this turbo before purchasing mine, but I do feel that I have done the research to be confident with my decision. If only turbine data was more available, I wouldn't have to rely so much on other's experiences.

 

My basis still stays the same. You actually made me more firm in my conviction. All that negligible performance for twice the price. Too many people have the mentality with their setups to try and "wring water from a rag". Spend that $5-600 you'll save on something that will make more power than the billet wheel.

I'm much more realistic I believe than others when it comes to cost vs benefit when it comes to performance. I'll be dynoing one of our race-cars soon with a bunch of our prototype parts (internal, external) and our turbo using modified off the shelf parts. I hope you make the right choice for your setup

 

Everyone has their own opinion when it comes to what something is worth and it seems that your opinion is clear in this matter. There is no denying that both turbos are a great match for the 13B and I don't think either of us would argue that. I do still believe, however, that the FMW is worth the extra $350-$400 over the standard S362 (not sure where the $500-$600 that you stated comes from) for my application.

The fact that the FMW offers the same flow and better efficiency with a smaller compressor wheel means that spool and boost response will also improve. That alone is worth the extra money to me. Then you can add to that the idea that a higher average compressor efficiency will result in lower charge temperatures and my decision is pretty much made (esp. because it is in the mid-range where it matters).

If I were building the car for drag racing or highway pulls, then I would most likely agree that the FMW isn't worth the extra money. But this is a track car, where slight improvements in transient response, spool characteristics, and charge temps are worth a bit of added cost...to me at least.

 

well if you already knew what turbo you wanted you should've just bought it haha

 

The question wasn't about turbo choice...I decided that months ago. I was merely defending my position as to why I am choosing this turbo.

The reason for this thread (as stated in the title) was to choose a turbine A/R. That is one area that I can't calculate everything and have to rely on other people and their experiences with similar turbos by the same manufacturer to make a decision. Until I do that, it's kind of hard to buy the turbo.

The guys at full-race recommended that I run the 0.91 A/R, but I find my self questioning that recommendation (in all fareness...I'm a skeptic and question almost all recommendations). So, what I am really doing is just looking for some extra input on the matter...hopefully from someone else who has run Borg Warner turbos before and can verify whether or not the smaller turbine a/r is okay since it has a larger turbine wheel.

 

From Sean at A-Spec

I think the .91 will be fine.

 

I just placed the order for my turbo with the 0.91 A/R turbine housing.

I will be monitoring my EGT in each exhaust runner just to make sure that everything looks good.

 

Let us know how you fare wrt EGTs.... I would have probably went with the 1.0 A/R, although the difference between a 0.91 and 1.0 isn't huge numerically.

 

I'll be sure to do that. I will probably be starting a build thread here pretty soon and will post a link to that thread in this thread.

The main reasons that I decided to get the 0.91 A/R were to test out my theories about not needing as large of a turbine A/R on BW turbos compared to Garrett units and because if my EGT's are too high, I can always get a 1.00 A/R housing down the road...but it is hard to do that the other way around with any confidence.

 

A comparison picture between 0.81 and 1.15 T4 A/Rs..... this for a P-trim turbine wheel:

 

You will be just fine. Most people are used to P trim turbine a/rs, your .91 is probably bigger than a 1.15 P trim housing. For example a GT35R 1.06 is like a .84 P trim housing in terms of volume/flow. It should be manageable @ 15psi with a 4" exhaust. Might want to drop the revs a little however.

 

Thanks...that is exactly why I believe that my 0.91 A/R will be sufficient as well.

 

I love this turbo I had mine on my car s366 but I don't know what a/r on it ,when I bought it I didn't ask but I rememberd now .How do I know what size a/r please?

Cheers

 

Got the turbo in a couple of weeks ago. Figured I would snap a few pics and post them here before I really got to work on the car...

 

I'm about to sell my GT35R kit and my roommate is going to build me a manifold and a 4" downpipe with twin 38mm recirculated. This is the turbo I'm very interested in so I'm eager to see your progress.

 

Very sexy...I'm considering the same turbo in 67mm trim for myself.

 

So the S400SX FMW? That's a big turbo. Post a link in this thread whenever you start that project...I'd like to see one of those stuffed in the FD.

 

Will do...I'm eagerly awaiting your results with the 62mm version but I'm pretty much decided on the S467SX FMW.