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    • VTT N54 GC Lite turbo Flex Fuel testing with 2008 335xi on 91 octane, E30, and E50

      Hey guys wanted to share some results. This car belongs to a customer who brought in his 2008 335xi for turbos and a lot of maintenance work. His goal was usable power on a VERY basic set up, he even wanted to keep the stock catted downpipes (we advise/advised against it, but agreed to it).


      Once we got everything installed and working, we got the car on the dyno for some tuning using MHD. We started with a base map Justin (V8bait) had given us quite a while ago ran it through the FF map creator and made the changes required. We ended up with about 6 revisions for this particular tune. Most of those revisions were due to finding errors in the map on things like cold start (no fault of Justin's, just being an old bin it needed some love). Once we switched over to ACN91 (garbage fuel), we did 3 more revisions reducing timing to keep corrections reasonable.

      We started tuning on E30 added enough E85 to get E50, then using Pro-Tool and the prime fuel pump function we drained the tank as much as we could. Our ACN 91 has about 10% Ethanol in it we have tested it and found up to 15% at times. Using the prime function you can never get all the fuel out. We ended up with the sensor bouncing between about 15-17% ethanol.

      Mods are as follows:
      2008 335XI 6MT
      Stock motor
      Stock head
      Stock intake manifold
      VTT GC Lites
      VTT Aluminum outlet
      VTT stock location Silicone inlets
      VTT DCI
      5" intercooler
      NGK plugs gapped to .20"
      Delphi coils
      VTT Crankcase breather
      Spec 3+ Clutch
      3.5 bar map sensor
      PFS Single Shot bucketed LPFP
      STOCK HPFP with 80K on it
      No fueling aids of any kind
      Motiv Flex Fuel with V8bait base map
      XDF with HPFP tables
      X-delete used for dyno

      Dyno numbers were as follows with a minimum of 3 runs on each fuel type

      ACN 91:
      Best run 463.23WHP/513.51WTQ
      Average of all 4 runs 456.17WHP/512.26WTQ

      E30:
      Best run: 523.03WHP/531.05WTQ
      Average of all 3 runs 519.49WHP/534.71WTQ

      E50:
      Best run 548.08WHP/566.16WTQ
      Average of all 3 runs 547.08WHP/568.46

      Spool is as always insane on the GC lites, 500WTQ and full spool by 3K on the dyno will equate to full spool by about 2700 on the street. With the XI turned back on this car will be a rocket.

      No changes were made to boost or timing between the E30, and E50 runs; we let flex do its magic and interpolate between the two tables to get us what we needed. As you can see on E50 the HPFP is maxed, it is just enough to provide clean runs, but we recommended to the customer if he plans to run E50 he needs a shotgun or PI.

      Flex is pretty cool seeing the power differences with no tuning changes. For ACN 91 we actually did go back in and drop timing almost 4 degreesin the base table, despite that it ended up making more power because it cleaned up the corrections. ACN91 really does not like much over 4 degrees past20 psi.

      All in all for stock catted downpipes, no fueling aids, and a basic real-world flex set up, over 460WHP, and 500WTQ on garbage ACN 91 is quite solid. On 93 with timing bumped back up into normal range 500WHP on pump gas would most likely be accessible.

      We can't wait to get it back to the customer!

      Best ACN91



      All ACN91



      All E30



      All E50



      All Runs


      This article was originally published in forum thread: VTT GC Lite Flex Fuel - ACN91 / E30 / E50 started by Chris@VargasTurboTech View original post
      Comments 12 Comments
      1. Carl Morris's Avatar
        Carl Morris -
        This is my car, just a couple of extra details:

        Actually, car is a 2008.

        I don't recall being advised against the stock DPs, but I know the tradeoffs and am concerned about getting through emissions in CA. Right now I've still got Wyoming plates on it and could run anything, but being cautious here. Having said that I was pleasantly surprised that things went as well as they did through the stock downpipes. If I get confident I don't need them later I'll definitely ditch them.

        I think the reason for this base map was that I needed a non-locked map because I may make a few changes myself in the future and also I want to be able to do things like make a valet map, etc. I have a lot of Cobb ATR experience but none with MHD yet and wanted to take the map the car was delivered with and make whatever I want from there. So locked maps would be useless to me.

        Tony was great about sending datalogs for me to review so I could feel confident that it was close to where I wanted to be. I didn't want to take delivery with a tune that generated a lot of knock events and I appreciate the time taken to help get to that point.

        Lastly, I just realized I've been confusing my E50 hp and torque numbers and need to correct the numbers I've been telling people :-). Anyway, it's been a good experience working with Tony on this. The car itself isn't really "worth" putting this kind of money into, but when I compare to the 50k I need to get into something I might like more it seemed like a good idea for a daily driver for the next few years. And I may just hang onto it forever as my last manual transmission car.
      1. Chris@VargasTurboTech's Avatar
        Chris@VargasTurboTech -
        Hey Carl, fixed the year. I think you're going to love the car. I really like this platform at/around this power level, it has good longevity and is a hoot to drive with some semblance of reliability. Add a few hundred more hp and it's a full time job keeping it all happy. My personal car is also a 6MT, 130k on it now, no reason to sell, it's not worth anything and I still really enjoy driving it. Enjoy 'er!

        Chris
      1. Tony@VargasTurboTech's Avatar
        Tony@VargasTurboTech -
        Hey Carl,

        In our initial email when you said you wanted to possibly do downpipes only if it would pass smog I believe I said we do not recommend stock downpipes due to the restictive nature. Either way we are very pleased with the results. The car is running solid! We appreciate your business!
      1. Sticky's Avatar
        Sticky -
        Going to promote this to the front page but need an image to go with it.

        I assume no objections to this one?

        Click here to enlarge
      1. Chris@VargasTurboTech's Avatar
        Chris@VargasTurboTech -
        That's fine Joe!
      1. vrsixxxxxx's Avatar
        vrsixxxxxx -
        Very nice....my gc 2.0 on order cant wait to see what they do. Any recommendations on tuners? I have PI going in too and stock ecu so currently on mhd.
      1. langsbr's Avatar
        langsbr -
        Great numbers on ACN91. I may have missed it but how much boost was each dyno run at?
      1. Carl Morris's Avatar
        Carl Morris -
        The logs I saw showed around 20psi on the straight ACN91 testing. This was immediately after E85 mix testing so ethanol was still around 17% according to the sensor (ACN91 supposedly should read around 15%). The load target was set to 150.
      1. Carl Morris's Avatar
        Carl Morris -
        Just to update this, everything is going well. I got to spend a lot of quality time with the car last week and a dozen or so iterations of the maps while running ~E40. Especially in this colder weather I find myself tuning to the HPFP as much as anything else. When it's cold 23psi is about the limit at peak VE if I want to stay above 1000psi of rail pressure.

        Speaking of which I had an epiphany about fuel stuff. I'm used to old school electric fuel pump with return. Horsepower limited but not torque limited at the motor. I couldn't figure out why I kept hitting the HPFP limit at the torque peak instead of the horsepower peak. Then I realized...DUH...it's engine driven. So in theory in can support twice as much horsepower at 7000rpm as it does at 3500rpm. So there are two separate types of limits to watch for since there are two different types of fuel pumps in the system. Live and learn. But it means no giant turbo car midrange torque peak unless I spring for more HPFP or secondary port FI/meth. Feels more like a LS than a turbo car above 3500rpm when you tune for flat torque.

        I can see the possibility that I may make more power at E30 than at E50 before this is finished. It's really nice to work on something that easily hits whatever boost target you set (under 30psi anyway) at any rpm.

        Side note, I had Tony set the xDelete on sport when I left his shop. That's been fun but I'm really eating tires in 1st and 2nd gear with it. I need to get my license/cabling figured on that and use the fronts a little harder. Traction is really limited in low gears when the boost comes on, even with AWD.
      1. Carl Morris's Avatar
        Carl Morris -
        Side note, if @V8Bait is still on here I'd like to pick your brain a little...no problem paying a consulting fee.
      1. Sticky's Avatar
        Sticky -
        Click here to enlarge Originally Posted by Carl Morris Click here to enlarge
        Traction is really limited in low gears when the boost comes on, even with AWD.
        Really? You're spinning all four even in second? That's impressive.
      1. Carl Morris's Avatar
        Carl Morris -
        Click here to enlarge Originally Posted by Sticky Click here to enlarge
        Really? You're spinning all four even in second? That's impressive.
        No, spinning the rears while the fronts pull a bit too lazily. The xDelete sport mode only locks the diff/clutch about 50%. Works extremely well for pulling hard in a corner, oversteers a bit instead of understeers but the fronts keep pulling the way you are steering so you don't get too far out of line if you stay on the power even if the rears are spinning. But for max acceleration in 1st or 2nd it's just not enough help from the front. I have the good Michelin all seasons but they are a couple of years old now on the standard sport package 162s. With really sticky tires it might not be an issue.