Hi All!

Hoping to get your insight on whether switching to SD is the right choice for me. We are finishing up my engine setup and now at the final phase of tuning. Desmond is recommending that I switch to SD and swapping to 4 bar?

I've done as much reading as I can about this but I'm not really sure this is the right way to go for my setup. My build was based around reliability (as reliable as possible) and consistency rather that MAX POWA... I chose the smaller 55mm stock frame/manifold setup with a target of 450hp for reliability and simplicity. My hope has been to just get to event and run it with little to no messing around with tuning or adjustments outside of suspension/alignment. I don't really care about winning and the goal is to have as little down time as possible for mechanical issues.

It seems to me that switching to SD could create issues when going from sea level to high elevation. Also, from what I've read it sounds like low speed and part throttle is affected negatively? I have no intent of switching to stand alone. I want to keep the setup and car as simple as possible to try and maximize seat time over trying to win plastic trophies.

 

To me the car runs much better overall on the MAF on the stock ECU.
Driven, tuned and rode on many different setups and nothing beats how it drives on the MAF.
My current setup is similar, FP green on 25lbs and after doing an SD tune and spending a lot of time trying to get it to drive like stock I decided to just go back to MAF and immediately the car was soo much smoother.

Only benefit I see of SD on the stock ECU is if you blow a coupler then it’ll still drive ok.
But at 25lbs it’s just not something that happens to me so moot point as far as I’m concerned.
Also the 4Bar MAPs are not reliable.
I run the OEM 3Bar of an Evo X, that’s good up to 31/32lbs which for me is more then I need. And OEM reliability.

 

I also switched my car from MAF to SD, stock turbo and ECU. In the 10 years I owned my car, it has only broken down twice. Both was due to a faulty OMNI 4 Bar, which was replaced free of charge. Symptoms prior to failure was the car bucking at low RPM. I believe it was some electrical contact issue within the part itself that was supposedly resolved. Have not had that issue in over 5 years but I rarely drive my car. If it ain't broke, leave it alone.

 

For reliabilty, get an MHI-18k. the AGT stuff is ....meh. And doesn't perform well per wheel size.

SD runs very well, requires a proper tune and you have to let the car warm up before driving away. If you do cams you pretty much need to do SD.

The MAF works until the screen gets sucked into the turbo. Or a decent set of cams cause too much reversion and it won't idle.

 

If you want trouble free with AC, stay with MAF or get a tuner to guarantee he can make it work troublefree. I'm sure some can, but 2 "reputable" shops near me CAN'T. I made more progress with it than they did.
I also had omnibar 4bar sensor issue. I cant see any real advantage comparing MAF vs SD, but I autox more, just basic 450hp setup. maybe MAF is harder to find as backup?

 

I've already replaced my Omni 4 bar once due to no start back in 2015, now i'm having some low speed bucking issues and i think you just solved it for me. Did Omni replace it for you? Otherwise i think i'll go with an Evo X MAP sensor since i'm still under 30psi on my Evo 8

 

Yes, both times they replaced it free of charge. It's been over 5 years so not sure if that is still the case.

 

Agreed with you on all these points. I would also like to add that the Evo X MAP 3 bar sensor is the most reliable MAP sensor you can run on Evo 4-9.

The purpose of SD tuning is to properly tune the car when the MAF becomes a restriction in air flow going into the turbo. For example, a larger ID air intake or full frame turbo. There are many threads showing the reliability of SD tuning at different elevations. Ask other tuners or DP about it.

 

Barometric pressure changes impact startup at substantially different elevations.

At WOT it shouldn't make that much difference. The SD calculations use the temperature and pressure in the intake manifold to calculate fueling, which are post-turbo and therefore not exposed to the atmosphere.

If you're tuned at a high elevation and you drive the car to a much lower elevation it will start hitting new cells in the VE table that you could never hit a higher altitude. That can cause problems if the tuner never adjusted cells outside of the observed range during testing.

Different elevations can technically change the VE slightly because the exhaust side is pumping into a lower absolute atmospheric pressure. If you're going from 14.7psia at sea level to 12.2psia at 5000ft you have 2.5 psi less pressure on the outlet of the exhaust. For our turbo cars, exhaust manifold pressure is so high already that this shouldn't matter very much.

With standalones you can add an exhaust manifold pressure sensor to account for this. The speed density calculations can use the difference between pressure at the intake ports and exhaust ports, rather than relying on the intake manifold pressure alone. On our turbocharged cars this would barely change with elevation, though.

So as long as you can get startup tuned properly, I wouldn't worry about it. That said, there's nothing wrong with a good MAF tune as long as you're not having problems with the MAF sensor due to cams or different aftermarket intake pipes. I think a lot of the praise for SD over MAF on stock-ish cars comes from people who are basically going from poor MAF tunes to good SD tunes.

 

I am in this seat to make a decision as well.

my current build is HTA71 with a stock evo 9 head and evo 9 built block.

i Was thinking to go gsc s2 cams for a little more juice but now I am rethinking this based on this thread.

might be better to stay stock cams since I’m running MAF intake.


It will be a street car and I don’t drag race.

 

Stock frame turbo on a 2.0L gets R1 cams.

 

Thanks for the advice.

I was happy with my oem power. But since I am rebuilding the block the builder suggested some cams for the head.

I’ll read up on R1 literature here. I was advised get gsc s2.

there are a few guys on the forum running HTA71 with gsc2 making good power.

thanks I’ll get to reading !

 

R1 is very close to the S2 for lift, but shorter duration. Helps with faster spool and better mid range.
With a stock frame turbo and stock intake manifold, it's the perfect pairing.

 

MAF will work well with this cam too?

 

Idk, you should move to speed density any ways. The MAF housing is a restriction.