We finally got some dyno time for the 335i at CarbConn in Kirkland WA. The tune still isn’t done, but, it is the current state of where we are at. There is still a problem with the knock pulling timing, so the timing and boost are set low for now.
[STX 71R for FA20 Performance Performance Hypothesis [Pre-Test]]
The OEM style twin scroll turbine housing is restrictive for turbos larger than the OEM unit and our STX 67 JB turbo.
This means for our big turbos, exhaust back pressure ratios can get well beyond 2:1 that is efficient for a JB CHRA.
If you are going 5:1 or 7:1 makes it hard to build power and it wears out the journal bearings and especially the thrust bearing.
Tuners that have a good strategy to manage this backpressure can make good power with the larger STX 67+ and 71 turbos, but if they didn’t, sometimes our customers would be disappointed.
The main point of that post was that a BB CHRA actually solves all of these problems:
The CHRA can stay efficient even if the pressure ratios are 5+:1
This means, it will be a lot easier for all tuners to build power with the BB version of our turbo.
The turbo will just make more power under the curve in general
The the thrust bearing is more durable, so the CHRA will stand up to more punishment.
[STX 71R for FA20 Test Results]
We set out to actually prove if the BB version of the STX 71 would perform as well as we had hypothesized, and solve the issues we had with the JB CHRA on the larger turbos. The short version is that yes, the SteamSpeed STX 71R BB Turbo for FA20 did exactly what we thought it would. It was a lot more efficient that the JB version of a similar size; therefore, it made more power everywhere. I suspect that tuners all over will be having an easier time getting results their customers want.
Here is the dyno result. 470 whp on E50 and 410 on 91 octane pump gas, and not measured on this chart, a ton more response everywhere. Note: this is at high altitude in Utah.
[Technical Notes From Jessie at FNP]
Jessie: “Hey, First let’s go over what we saw, liked and disliked with the unit.
It’s big, if the new unit has a clearance for the oil pan and obviously ships with hardware we are good. Obviously as the prototype it is going to have clearance issues, and fitment issues. There were literally no other issues noted from Luke on install.”
SteamSpeed: This will actually be a non-issue for retail units. We have actually already resolved all fitment issues on our production 71R. The production model has a modified turbine housing with a cutout to clear the OEM oil sump without modifying it. We also designed and manufactured custom studs that we include with the 71R install kit. This is how the retail unit will work:
Sounds epic. Do yourself a favor a crack open the boost nipple when running. The ball bearing turbo sounds incredibly mean at idle. With a catless exhaust it should sound great out the tail pipe. Think diesel turbo, screaming at idle.
Response, Response, Response. This turbo is incredibly responsive compared to the previous version. Transitions in and out of boost are much quicker.
More linear boost curve via WGDC input. What do I mean? Check out this boost profile compared to WGDC on the old vs new turbo. The new unit is much MUCH more linear with interrupt cycle. This tells us the effects of back-pressure are far less of an issue with this upgraded unit. You can also see the old turbo have more “Creep” under the curve. The new unit doesn’t not do this. The compare for RPM isn’t valid, as the previous tests were done in 4th, the current in 3rd.
67+ JB WGDC
71R BB WGDC
Makes more boost in the upper RPM’s. This also is a direct causation from the upgraded cartridge. It seems to be able to operate at higher levels of back-pressure with ease.
Red JB vs Yellow BB
Less oscillation of MRP than the outgoing cartridge. Just one of those anecdotal observations, normally we see much greater fluctuations in boost on the FA20 with our incredibly fast sample rates. This unit fluctuated much less, the average was 18% realized lower fluctuations. This is a great indication of how much more air is being delivered.
Much more efficient flow from the turbo. Check out the new vs old charge air temps!
New unit held much better boost. From 1.9bar avg on the old unit at redline on 100% interrupt, to 2.3bar avg.
Output: Was increased by 12.35% over the older unit. This was also impressive as the turbo could have easily generated around 8% additional output, but the owner of the test vehicle was very specific to “Take it easy”. Based on the airflow averages and their changes, I’d say this observation is fairly precise.
Check out these airflow differences: Old Turbo 229 average max, New over 300! (it was 309 average when extrapolated up). That is an increase of 35%. Same intake, and injector scalings were used on both turbos. Compared to the stock turbo this is over 56% increase in flow!
Well, hope this helps you guys. I poured over all the data and these were the things that popped out at me.
In that iteration, it made ~360 whp at PRE facility on pump gas. For comparison, the SteamSpeed STX 71 on a 2015 STI made about 420 whp on the same day. With that turbo it was rewarding to push the car, and if you kept the revs up, you could keep it in boost, but realistically it was a 4.5k+ RPM turbo on a stock EJ207.
We would manufacture small batches of this turbo, and we would sell them all out before we could install one in Domino, but we able to finally get one installed. It has the smaller 67mm compressor which should make it more responsive, but the “+” means that it still has a GTX30 spec turbine which is a little better suited for a 2.5l. I think a GTX29 size wheel would be perfect for the EJ207. Next update to the turbo we can make the change. 🙂
The STX 67 wheel did get us close to 4k RPM, but it still feels big. In fact, doing pulls, it feels similar to the 71; however, everywhere else, it is night and day. The BB CHRA is super responsive. Going on and off the petal, the turbo is a lot more responsive. It could also be related to the fact that we went to speed density from a MAF based tune.
What is the final result? It made about 10 whp less with a 4 psi more boost. Not a bad trade off.
The turbo still feels a little big. Andy at FTW thought going to a top mount could give back about 500 RPM of spool. It would probably be best for our usage of the car, but for vanity reasons we like having the huge FMIC. We could just go to a 2.5l displacement, but it seems like it goes against the spirit of the ej207 swap.
Where do you think we should take the build next? Let us know what you think.
Here is a good dyno result of a SteamSpeed STX 67 on pump gas done at Bren Tuning with a before and after, green being before, and red being after. Obviously there are gains everywhere. You can see their post on NASIOC here. The short of it, the customer go a 85+ WHP and 70+ WTQ gain on pump gas!
Here is a standard STX 67 for 2015+ WRX tune at COBB Surgeline. Unfortunately it does not have the before plot, but it was a 60 whp gain on pump gas. This car had a 3″ turbo back, intake, and front mount intercooler. It was tuned at COBB Surgeline. We have to give these guys at COBB Surgeline props. This customer was initially impacted by the wastegate flapper defect a few units had from the first production batch. The guys at COBB took the time to correctly diagnose the wastegate problem.
SteamSpeed STX 67+ for 2015+ WRX
Here is a nice dyno plot comparing a fully modified 2015 WRX without the SteamSpeed turbo [green], then with the SteamSpeed STX 67+ [red]. This with some ethanol blend, around 50%. This was tuned in Utah at FNP by Jessie. It looks like about a 100+ WHP gain and 65 WTQ.
PRE recently did a test that pitted lots of Subaru stock location turbos against one another. This is what the plot of our smaller Steam STX 67 looked like against a Forced Performance HTA 71. The STX 67 basically made power sooner, had better low down power, and made 10-25 whp across the entire rev band.
We have been able to compile our initial flow testing on our Steam STX 71 turbocharger, and we have to admit, our expectations have been exceeded. We didn’t expect the STX 71 design to out flow the Garrett GTX3071R, but that is just what happened. It turns out the original STX 71 design was actually quite good from the get go. Don’t worry. This testing is just a baseline. We intend to make it even better.
Just as a refresher, this is what the compressor map lines mean.
Here is the Steam STX 71’s compressor map. As yo can see, it has a max flow of a whopping 59.5 lbs/min.
How does the Steam STX 71 compare to the Garrett GTX3071R? See for your self. The STX 71 actually out flows the GTX3071R by at least a few lbs/min.
Here is the turbine section map for our Steam STX 71 turbocharger in our version Subaru WRX STI single scroll turbine housing. It is mildly ported and 8 cm^2 in Mitsubishi speak or 0.55 A/R in Garrett speak. The both measure the “size” of the scroll. Bigger means the housing can flow more generally speaking.
How does our Subaru turbine housing flow compared to the Garrett T3 housing for a GT30 turbo? It actually flows quite well for being “smaller” than a 0.63 A/R T3 housing. We attribute this to our signature 9-blade high flow turbine design.
We have been asked many times by our customers, what is the difference between Blouch Turbo’s 20G-XT-R and our Steam STX 20-R. We put together this little table to help you know that the differences are. As far as we can tell, the biggest difference is that Blouch’s BB 20G costs almost $300 more than the Steam STX BB 20G. What do you get for paying $300 more? We can’t think of anything either.