MAF to SD

[Innkeepr]

Here is my dilemma.

I spoke with a reputable builder while attending the Pittsburgh "World of Wheels", one builders 05 Wagon has the same engine build I am interested in.
We purchased a new EJ257 (2008) and are chamber matching the 2.0 heads. During the technical banter he asked if I was going to convert to Speed Density ?

My tuner, has a lot of experience building MS pros and has installed them in Honda's and Toyota's.
My 04 WRX was tuned via Taxtric. He has suggested going to a SD set up in the FFR.

Has anyone converted to SD ? Have you found any benefit or is it just a waste of time and money ?
The only thing that really peaked my interest was adding wheel sensors to the MS Pro to get traction control.

Thanks for the input.
"E"

[BC Huselton]

Here is my dilemma.

I spoke with a reputable builder while attending the Pittsburgh "World of Wheels", one builders 05 Wagon has the same engine build I am interested in.
We purchased a new EJ257 (2008) and are chamber matching the 2.0 heads. During the technical banter he asked if I was going to convert to Speed Density ?

My tuner, has a lot of experience building MS pros and has installed them in Honda's and Toyota's.
My 04 WRX was tuned via Taxtric. He has suggested going to a SD set up in the FFR.

Has anyone converted to SD ? Have you found any benefit or is it just a waste of time and money ?
The only thing that really peaked my interest was adding wheel sensors to the MS Pro to get traction control.

Thanks for the input.
"E"

You can read about it by google "Subaru Speed Density" Cobb set up. You can also talk to Brian at I Wire he makes the plugs to support SD Hybrid which uses both MAF and IAT in a Cobb Pro Tune. You do need to run a constant wideband O2 sensor with a dash gauge to pay attention to A/F data.
All the Cobb pro tuners I talked with said they would go the SD / Hybrid route. I am using an I Wire Harness, and Turbo Time in Apex NC, to do the base load and then the Dyno Tune. It is has been available from Cobb since 2012, and there are plenty of Competent Pro Cobb tuners using it. It is not costing me anymore money for SD vs. Total MAF only and if you prefer to switch out of SD you can default back to MAF only without issues. You do need to get the O2 full time which is added money. I do not know how many other owners are actually running it...so your inquiry is a good one.

BC

[Hindsight]

Most people go to speed density because at a certain power level, around 400WHP or just shy (especially in cold weather), you max out the mass air flow sensor (it supplies it's max 5 volts before your power peak so it will tell the ECU less air is coming in than it really is, causing a lean condition). The fix is to go with a larger MAF housing, and have a tuner recalibrate the ECU to adjust for this, but the issue here is that larger MAF housings will not have as much "resolution" at lower RPMs and under cruise conditions, so they won't be quite as accurate. There is also the fact that a MAF housing itself can be considered a restriction in the intake but I don't think that matters too much, especially on a turbo car.

Another reason people go to speed density is to be able to use a blow-off valve that vents to atmosphere instead of a bypass valve that redirects the already-measured air to the turbo intake, behind the MAF.

You'll get a lot of different opinions on MAF vs SD, but my concern with moving to SD is that changes in altitude, air temp, and humidity levels will all impact the volumetric efficiency of the engine. Some of those can be accounted for with sensors, but humidity, for example, can't, and even the ones that can, can still be off a little bit - enough to cause the car to run poorly. I feel MAF is safer but if you go with SD, ensure you get a really, REALLY good tuner who knows what they are doing and will support you down the road if any issues arise.

[BC Huselton]

You also might want to talk with known engine builders and experienced racers. Top Speed Motorsports In GA, Mike Adams recommends it to their customers. Hindsight knows Mike and has actually used their shop, I believe. I was told the Hybrid tune adding the IAT to the process, addresses the VE potential issues. However, more owners with direct personal experience will certainly help us get better data. I will ask Turbo Time about it and report back. They are running and crewing 4 cars in a March event. So we should be able to see about their experience. I will report back.

[Rob T]

Paul ar yimisport switched to speed density on my R. The cold air intake is in the passenger area and the impact at different speeds was a concern. Two track days in with a 320 rwhp tune on 91 octane. The power and torque curve are awesome. I posted a video on my build page a few weeks ago.

[taco20]

Hey I went SD because I have an open blow off valve. I also moved the intake air temp sensor after the inner cooler so the ECU could read the cooler temp. One benefit I found was by removing the MAF was I could make my own intake tube without worrying about installing the sensor. So now I have my filter in the opening on the pass side behind the door. I track my car most of the time but have had no issues on the street with drive ability no matter the temp outside. My car was tuned in FL and I live in VA and have had no issues.

[Innkeepr]

WOW - you guys are quick !

We were originally going to put the 207 crank and new rods into the 257 (destroker) with the 205 heads. The builder said something along the lines of " thats not really good on the street, more of a track app ".
I am aware of the Cobb - When I looked at it it says "2006-14 WRX" - I do not have an ECU at this time, my donor was a 04 NA Auto car. That's why I was looking at the MS3 Pro set up.

I will inquire more from the shop, the car on display was a 257 hybrid with 500+ AWHP with an e85 tune. I am not looking at that extreme, and feel 300ish is more than enough.
I didnt inquire as to the ECU - but will.
As I am starting without a stock ECU - I am looking at cost of the Cobb, and ECU vs the MS3. I think its going to be comparable, when adding in the sensors.

[BC Huselton]

WOW - you guys are quick !

We were originally going to put the 207 crank and new rods into the 257 (destroker) with the 205 heads. The builder said something along the lines of " thats not really good on the street, more of a track app ".
I am aware of the Cobb - When I looked at it it says "2006-14 WRX" - I do not have an ECU at this time, my donor was a 04 NA Auto car. That's why I was looking at the MS3 Pro set up.

I will inquire more from the shop, the car on display was a 257 hybrid with 500+ AWHP with an e85 tune. I am not looking at that extreme, and feel 300ish is more than enough.
I didnt inquire as to the ECU - but will.
As I am starting without a stock ECU - I am looking at cost of the Cobb, and ECU vs the MS3. I think its going to be comparable, when adding in the sensors.

Just a "Heads Up!" For the Street, building a car that has OBDII is a plus in some States for registration. And, what Cobb makes available now for tuning is far more user friendly than "Any" stand alone ECU. IMO. If you ever decide to sell your car, having Cobb with the access port is far more "Peace of Mind" to the buyer...vs, "Oh, What do I have here for a ECU, and where can I go to get support." I have been through this, with a move between States and it lead to the prospects of Divorcing my 818. I am back to "Speed Dating" with a new SD Hybrid tune coming soon.

[alpine227]

I am running MS3 on the native trigger wheels speed density, i have constant barrometric correction as well. Simple tuning with tuner studio and every tuning shop I have talked to can tune it as the principal's of tuning are the same across ecu brands once you strap it to a Dyno.

[SixStar]

Keep in mind too that iWire sells a PnP SD hybrid harness, best of both worlds - https://www.iwireservices.com/produc...-adapter-02-07

[Sgt.Gator]

I've had both The Cobb Hybrid and full SD. I prefer the SD setup for all the already stated reasons in a race car. The Hybrid may be better on the street.
I'll add one more. I've lost two races near the finish when my IC pipe either started leaking or completely popped off. With a MAF/Hybrid tune, the engine starts running slower and slower, popping and snorting, you can make it maybe half a lap and back into the pits, then it won't start at all. Or you don't make it to the pits at all and your race is over.
One time this happened on the very last lap of a 30-minute race when I was almost a full lap ahead! It was raining hard and cold, which is Subaru love when you're in an AWD Subaru and the two guys chasing you are in Mustang FR500s. I came to a stop and watched them go by.. I was sick!
With an SD tune, the engine keeps running, albeit with a major boost leak and less power, but it keeps running. With a MAF and a boost leak, your ECU has conniptions.