I've been doing my due diligence for upgrading my Turbo in the future. I'm pretty sure I'm not looking for the absolute most power, but am intrigued by the MPI system providing more fuel headroom and the added benefit of keeping the valves and ports clean. The question that's been in my mind, is if the MPI system only activated under full throttle conditions or if it is always supplementing the direct injection system? For me, I'd likely be fine with only a HPFP / Turbo / Tune for my power goals, but having a safety net for fueling as well as valve cleanliness is compelling. thanks
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MPI question
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jimlloyd40
Autocross Champion
- Location
- Phoenix
- Car(s)
- 2018 SE DSG
It's a supplement to the DI injectors. Not just full throttle. You wouldn't get the HPFP if you go MPI. Only the LPFP. But MPI adds so much to the cost for parts and a tune it's not worth the cost to keep the valves somewhat cleaner. You can do many carbon cleanings for what MPI costs. If you want to go above the 500 HP level I would get it then.
Do they actually use the port injectors below a specific RPM/load threshold though?
Ideally they'd use port at idle and very low load, and transition gradually to DI beyond that; however the MPI kits include fairly large injectors that I suspect wouldn't idle better than the DI system (despite the advantages to port injection at low load).
You can go with a Euro rail and injectors and run them that way. That's how the OEM ones run. You won't really get benefit at high load/rpm
You COULD run Euro MPI for port cleaning AND run an upgraded HPFP for high load fuel.
Right, but the OEM port injectors on Euro cars are ~125cc, vs the ~1,000cc port injectors on US spec MPI retrofit kits.
I admit, I don't know the right answer but expected it to be the added port injectors to be activated at a higher load/RPM to supplement the DI system.
If consensus is they utilize the Euro OEM approach, then they have to recalibrate significantly more, and try to get relatively large port injectors to idle smoothly (when idle was already sorted in the OEM US spec calibration). Surprises me they would take that approach, but again I'm not terribly familiar with tuning MK7's.
You can have the car tuned however you like, though most people using them with big injectors run DI-only at low RPM and gradually shift fuel to MPI depending on airflow/torque. DI-only combustion provides significant advantages in terms of spool-up for larger turbos. No one does PI-only at load without DI plugs, you'd burn up the injectors without fuel flowing.
If you wanted to replicate the european setup there's no reason you couldn't, but I wouldn't bother with an upgraded HPFP and small port injectors given larger injectors are generally a more reliable way to add overhead than aftermarket HPFP pistons (or at least as reliable as any MPI setup would be, large or small).
The OEM logic is for the port injectors to be used during low load operation. You could get Euro manifold with euro injectors and run it that way if you wanted. Not sure it's worth it because the current VWs in europe no longer have port injection.
jimlloyd40
Autocross Champion
- Location
- Phoenix
- Car(s)
- 2018 SE DSG
I saw a post recently that had pictures of a Euro one and the valves looked pretty terrible.
I think we're talking past one another. I've not advocated for any approach and certainly not implementing Euro injectors in a US spec car.
I'm not getting my car tuned, I'm not the OP.
The OP comment: ". . .if the MPI system only activated under full throttle conditions or if it is always supplementing the direct injection system?"
I assumed it wasn't always supplementing, but a response made it unclear. My comments beyond that were a thought experiment on ideal conditions vs what tuners would easily implement and likely muddied the water... My fault, and carry on.
Sorry, had to go back and confirm; OEM implementations do exactly this, at idle and very low load.
You can pause at 2:51 to see the table that I'd love to see for the MK7. It would definitively answer the question.
The best explanation I've seen is here, under factory behavior: https://ecutek.atlassian.net/wiki/spaces/SUPPORT/pages/378765322/EA888+Multi-Port+Injection
I don't know about Ford as that video references. Would be nice to see a factory EU calibration, I'll have to dig one up.
I don't know about Ford as that video references. Would be nice to see a factory EU calibration, I'll have to dig one up.
Excellent link, thank you.
Also saw the note that confirmed the MK7 requires flow through the DI system for exactly the reason you referenced, good call. Interesting that varies across platforms.
Wonder no more.....
Without digging deeper, there may be a different set of idle tables. But looks like they are active in a very narrow window in light load operation between 66 and 132 ft-lb, once coolant is above at least 71*F In these conditions, MPI is accounting for 50-60% of overall mass fuel flow. (There is a separate 'max' table with values of 0.50 that I didn't post)
From a stock ROW Golf R/Audi S3 file