Preturbo 335i Strange Results

[rudypoochris]

Hey Guys,

I have been reading up on WAI for a while and finally decided to take the plunge. I wanted to make more power, but my stock turbos are already far off the compressor map. I decided on pre turbo hoping to get more efficiency out of them. I settled on a mechanical setup as these are supposedly going to have smaller droplet size. I just got this built and running and my results were not really what I expected.

Base setup before meth/water:

1. 2008 335i N54 Coupe
   
2. Compression 10:1 with direct injection running 50-50 E85/91 mix
   
3. Boost set to 17.5 psi (stock is 7.5 or so) so way off the map making 430whp
   
4. After market intercooler and tune, no other modifications (stock DPs, fully catted)
   
5. Currently limiting boost to save turbos. I am NOT octane limited at this time and could probably hit 19-20psi without losing significant timing
   
6. Turbo Tout is probably in the 350F range
   

Adding meth/water:


I went with a Wannaspeed mechanical kit that uses air mix nozzles. I modified it quite a bit. Two nozzles one in each cone filter injecting into 60mm stock plastic intake tubes which have bends and such for about 2 feet before entering the turbos. The 50% meth/water mix is driven from a trunk mount tank with a check valve on the air line (not progressive). Flow is measured using an Aquamist sensor with 100-1500ml/min scale (half graph is 750ml/min or so). Preturbo meth is triggered by boost switch at probably 8psi (just setup last night).


Pictures:







Just to clarify, none of the ports below are for charge pipe injection. That is all boost air to the tank or meth nozzles.










First Results:


I ran the car with and without the meth water running last night. I used the exact same map and ran within 5 minutes of each other. On the no meth run I was going downhill, on the meth run I was going up hill. Ambient was 55F the no meth run started at 59F and the meth run at 69F IAT.The intercooler is heat soaking way quicker with meth on presumably since the specific heat of the meth air mix is much greater than air only. Usually I see IATs no more than 10F above ambient. After one pull with meth I was at 25+ over.


No meth:





Meth:



Note the faster rising IAT, identical PWM (wastegate duty), and surprisingly reduce timing at start of run (fluke?).

The curve to look at specifically (at least I believe) is "PWM". PWM refers to the duty cycle of the wastegate as controlled by the car. More PWM means the wastegate is held more shut. You can see PWM spike during spool up and rise as the RPMs increase and the turbo is working harder to supply the required boost. In both logs, PWM is nearly identical. That is to say despite pouring 600-700 ml/min of meth water into the intake, the amount of work the compressor is doing has not dropped. I thought it would since the WA mix should be sucking up heat during compression leading to more air out of the compressor per turn (higher efficiency).

Am I thinking about this wrong? Am I set up wrong? Should I try biasing more water or more meth? Maybe the mix has completely atomized before the compressor due to my long intake tract? Do I need more flow?

Thanks guys,

Chris