Wouldn't something like Seafoam, sprayed in through the throttle throat and via vacuum line into the intake manifold, then left to soak for a while before startup, affect the carbon buildup on the valves?
I think that with theccomplexity of the DI injectors, it wouldbe wise to run a KNOWN strong injector cleaner (SI-1 seems the strongest in my experience, but I have yet to get permission to use the $1.4mil GCMS at the lab to run a bunch through to see lol).
I know that with my 328Ci, which is using Bosch Gen3 injectors instead of the usual BMW up-sized injectors (the Bosch Gen3 are a huge improvement, with something like 380 percent better atomization, average droplet size 400pct smaller, dispersal evenness improved to within +/-0.02 percent per square mm, 40pct shorter fuel pulses which results in better AFR across the Rev range, and a host of other improvements), for a forced induction application, my tuner was able to squeeze out not only 29rwhp and 18rwtq more than equivalent blower setups using Gen2 injectors, but they're also one of the reasons why I can run a 6krpm motor to over 8.4krpm without a single issue (aside from theoobvious mechanical modifications needed to permit such high engine speed).
The better fuel dispersal and improved DME control over injector timing/pulses also allows for a greater variance in speed/load injector mapping, so muchso that I went from 28.8mpg N/A (268rwhp) to 30.9mpg FI (419rwhp).
Direct injection is nothing more than a way for manufacturers to easily meet CAFE limits, and reduce costs long term, because as my experience has shown me, regular injectors still have plenty of life in them.
Oh, and the ones in the 328 are rated at over 2x the flow rate, which normally results in somewhatrich low load AFR, but it is not the case for these.
I just installed a set of slightly upsized Gen3's in my E46 M3 to go along with the CF CSL Airbox + Tune, Supersprint V1 Stepped Headers, Akrapovic Ti full exhaust (10lb total vs over sixty), VAC superlight UD Pulleys, 190lph fuel pump, BW Crank Bearings, ARP full engine fastener kit, VAC One-Point HG (0.1pt compressioniincrease), and some 296/292 cams. VANOS is running Beisan eeverything, and maintenance is well ahead of schedule.
It was retuned for the new injectors, and in the following time I saw an increase in power on same dyno w same operator and extremely similar conditions, from 336rwhp and 261rwtq to 342rwhp and 267rwtq, with as much as +19rwtq and +15rwhp under the curve.
Even with my data logging showing an average TPS reading 18pct higher (meaning I've been spending a lot more time running it harder, but wouldn't you?), my avg economy on ethanol free 93aki has gone from 24.2mpg to 25.7mpg. Took a trip to see family for Thanksgiving, 400mi each way, and prior Highway economy was around 28.0mpg. Now? 30.3mpg.
For a modification to a performance car, for more performance, and actually to increase fuel, it's sure had a great effect on economy!
I am now convinced that DI has its uses, but they're far from universal and not anywhere near as universal as manufacturers are pushing. In fact, I question the need even for factory turbo (GDI) motors...
