Is Direct injection LIMITING Power?

[@hpa101]

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[@hpa101]

Fun fact: OEMs also have examples of engines with both DI and PI from stock, although it is for different reasons than what we are discussing in this specific video. The GT86 tuning example in the Practical Reflash Tuning course is an example of this via the FA20 platform where we run through the 6-step HPA tuning process for it and similar applications - Taz 😎

[@Nathan0A]

Under-reporting the MAF seems like a sub-optimal way to get the two fuel systems running in sync with factory ecu. I would think that intercepting the DI injector signal and cutting the DI duty cycle as port injectors blend in would be a slicker way to keep the rest of ECU logic happy with elevated power figures.

[@SusedatLubo]

It's a good concept running both not only for the intake valve cleaning, but I stumbled upon an article awhile back explaining why car makers use the DI + PI method. Supposedly PI gives better economy and emissions on low rpm, so the engine runs on PI only, at mid rpm it switches to DI and at WOT and high rpm it uses both to compensate for the DI running out of flow. I don't know how true this claim is, but for the intake valve cleaning alone it's a big step up over the first GDI engines which suffered from carbon buildup. P.S. Not only flow, but at very high rpm the time window for DI to spray on the compression stroke is much lower compared to PI which has a much broader time window to spray fuel. Hence why cars with DI only don't tend to rev very high. Possibly other factors as well (friction, efficiency, FI etc.), but this is a major one.

[@jordanarmijhoo5645]

Amazing video. I have a di car and have wondered how people have tackled making much more than stock power

[@M16xblowDRO]

Audis 2.0s come with both port and stock injection, it’s great for tuning

[@daveearnshaw6874]

@@M16xblowDROAudi RS3 used to,but now only has direct injection.

[@toyotafan1234]

I wish manufacturers would've did di like toyota where it has pi and di working together. Pi will keep those valves clean and di will give you the fuel economy needed.

[@manitoublack]

Feels like a 90's hks piggyback solution.

[@ben7020]

The bmw N54 guys use this method a bit, im not sure of their work around for the transmission side of things - torque reduction upshit etc...

[@toyotafan1234]

We use motiv reflex to control pi and either mhd tuning or jb4 in conjunction with the motiv for tuning. If it's an a/t we use xhp tuner to dial in the transmission.

[@D0ntWorryAboutIt]

Mike is an awesome guy! Quality products as well.

[@peedee4065]

Thanks for this very entertaining interview, Taz, and I laughed when you kept saying, let's back off a little bit. Michael alluded to the complexity of it all when it comes to torque calculation, the reduced maf figure sent by the Reflex Plus, and the usage of automatic transmissions. My takeaway is that the tranny is relying on info from the fuel management system. It just all hints at how much engineering and integration into every aspect of a vehicle there is on the part of electronic vehicle management. One aspect I did not understand is the fuel flow to the pi. The factory system uses a manual pump run off the camshaft. Reading between the lines I'm thinking the factory system pressurizes the di to its particular needs. But the pi system is simple pressurized off the fuel pump in the gas tank?

[@Fix_It_Again_Tony]

Usually you upgrade the existing low pressure pump or add a second low pressure pump in the tank to help supply additional volume at the correct pressure for the port injectors.

[@ElPants21]

A traditional electric pump in the fuel tank brings fuel to the stock mechanical high pressure, cam driven pump on the engine, which raises the pressure into the thousands of psi. If I understand right, they just tee into the fuel system BEFORE the mechanical pump.

[@peedee4065]

@@ElPants21 Thank you, that's the impression I got though Michael didn't simply and explicitly say such.

[@wrighty338]

Audi thought this through with 10 injectors on the 07K. 5 DI 5 Port

[@TheBCninja]

New ecoboosts are doing it too. They saw how going only DI sucked.

[@coreyw427]

Many VW Audi engines s as well as Toyota use both

[@DahkaShades]

07k a beast of a engine

[@bingysbackyard]

So the same as some of the factory cars systems like toyotas d4-s

[@hpa101]

Yes and no. OEMs do this for different reasons than the aftermarket, and there are many engines that do come with both from stock. Not the LT1 or LT4 here though - Taz.

[@Sibsko21]

Question, why would you back off the MAF DI curve when having port fuel come in

[@MagzV]

Because the port injection takes over the fuel mass, beyond what the DI needs to provide on its own.

[@Sibsko21]

@@MagzV Why must one fuel system take over the fuel mass. Why can’t the DI deliver its total capacity and the port adds to it?

[@MagzV]

@Sibsko21 Backing off the MAF curve doesn't mean reducing the output of the DI system. It simply means keeping it within its capacity.

[@Sibsko21]

@@MagzV Thanks for explaining, that’s the answer I was looking for

[@arya_amg]

Interesting I always thought direct injection would increase power because of lower cylinder temperature

[@soraaoixxthebluesky]

It does but the problem is you’ll run out of a spraying capacity way too quick for a high performance application. That’s why port assisted injection modification are needed.

[@farncoisbisson7737]

Need both ... direct injection only good for lower rpm numbers.. soon you start getting good air velocity you better spray it in the intake runners for a better fuel atomization.

[@laurean5998]

​@@farncoisbisson7737not true, brian tooley did a dyno test and the direct injection gained almost 10% in power over port injection, even on methanol.

[@MrSamPhoenix]

The real problem is AFM

[@notsogreat123]

Direct injection would be fine if it weren't for EGR !!!

[@reason2gether]

Just switch to all Port injection and be done with it.

[@hpa101]

kzbin.info/www/bejne/rKLKhIJulMiFn9Esi=tgq74XXh7uLAqI9r

[@shootinbruin3614]

@@hpa101 lmao thanks for the throwback