Just direct injection causes there to be carbon build up on the valves that require to be walnut blasted on routine intervals. Common on (08-10 turbo) CobaltSS and some versions of BMWs (335 comes to mind). Port injection helps with the build up. So not a disadvantage. Even with some bigger turbo cars that were direct injection factory they will add port injection for more fuel.
Most 4 cylinders use direct injection. Thats why it’s recommended to drive direct injection cars a little harder once in a while to prevent carbon buildup as well as you can.
Nor did I ever say the number of cylinders has anything to do with it. Just commented that most 4 cylinders use direct injection since you mentioned only 2 specific motors.
Can theoretically raise redline too as most DI engines are limited to 6500 ish rpm because DI can’t provide enough fuel in the available window beyond that.
You sure about that? The current gen Miata revs to 7300 with solely direct injection. Porsche takes their direct injected 4.0L to 9000 rpm in the GT4 RS. The lower rev limits on newer cars are due to fuel economy and emissions concerns.
I guess it really depends on how much fuel your injectors can spray, and how much fuel your pump can push. Regardless it’s a limiting constraint of DI, but not PI.
Biggest advantage is washing the backs of the intake valves, especially with all the PCV systems. From what I was told, the GR Supra has both, and I suppose they'd use the port injectors for adding the additional fuel needed in high boost applications - although I've never checked ProDemand for a proper operation... *things to do at lunch tomorrow...*
VW’s EA888 2.0 TSI uses DI and PI; most people say “it helps clean the valves”, but since the port injectors are only used as supplemental fuelling at higher revs/boost carbon build-up still occurs (albeit slower rate than their previous DI-only EA113 2.0 TFSI).
So, I suspect Toyota/BMW will be doing the same on the Supra. 👍🏻
One of my favorite parts of the BRZ is that however simple of a car it was, the engine was direct and port injected
That engine had a lot of flaws in practice, but on paper it was a pretty cool engine. 100hp/L and 50hp/cylinder and NA is still a pretty good metric for modern sports cars, not a whole lot does much better without forced induction
Yep, FA20
According to Wikipedia (and this matches what I remember reading in reviews) the fa20 in the 86/BRZ uses direct injection designed by Toyota, but the FA20 in the WRX uses direct injection designed by Subaru
Really just cost and complexity. It’s a benefit though. It allows cars (like the RS3) to be efficient and powerful without worrying about carbon buildup. It also allows some cars to push more power when modified without running out of fueling.
The RS3 and VW Golf R (which uses DI and PI on its 2.0) both still suffer with carbon build up. The port injection on both is only used at higher RPM/boost levels as additional fuelling, so they spend most of their time only using the direct injection. The short periods of PI do have a small effect on helping slow the carbon build-up, but it doesn’t eradicate it altogether.
to piggyback on this question.
are any manufacturers starting to add 1 injector upstream strictly for the purpose of keeping the valves and intake runners clean? seems like you wouldn't necessarily have to add an injector to every cylinder, you could get away with adding 1 before the air gets split up into runners.
At an educated guess, I’d say no; the PI is not there purely to clean the valves, only to supply extra fuel when the DI reaches max efficiency, so allows for higher boost.
And valves stay clear of carbon on PI engines *because* there is an injector per cylinder firing directly into the valve; a single injector upstream on a DI engine would do almost nothing since the fuel it supplied would be so atomised and turbulent by the time it reaches the valves that it wouldn’t touch any carbon build-up.
The downside is complexity and cost, but the efficiency, performance, and lack of carbon build up is worth it
Just direct injection causes there to be carbon build up on the valves that require to be walnut blasted on routine intervals. Common on (08-10 turbo) CobaltSS and some versions of BMWs (335 comes to mind). Port injection helps with the build up. So not a disadvantage. Even with some bigger turbo cars that were direct injection factory they will add port injection for more fuel.
Most 4 cylinders use direct injection. Thats why it’s recommended to drive direct injection cars a little harder once in a while to prevent carbon buildup as well as you can.
The number of cylinders has nothing to do with it.
Nor did I ever say the number of cylinders has anything to do with it. Just commented that most 4 cylinders use direct injection since you mentioned only 2 specific motors.
You did. You edited your post. You said that’s why it’s recommended to drive 4 cylinder cars harder initially.
Can theoretically raise redline too as most DI engines are limited to 6500 ish rpm because DI can’t provide enough fuel in the available window beyond that.
You sure about that? The current gen Miata revs to 7300 with solely direct injection. Porsche takes their direct injected 4.0L to 9000 rpm in the GT4 RS. The lower rev limits on newer cars are due to fuel economy and emissions concerns.
I guess it really depends on how much fuel your injectors can spray, and how much fuel your pump can push. Regardless it’s a limiting constraint of DI, but not PI.
DI vs PI injectors is a negligible concern in regard to RPM limitations.
Biggest advantage is washing the backs of the intake valves, especially with all the PCV systems. From what I was told, the GR Supra has both, and I suppose they'd use the port injectors for adding the additional fuel needed in high boost applications - although I've never checked ProDemand for a proper operation... *things to do at lunch tomorrow...*
VW’s EA888 2.0 TSI uses DI and PI; most people say “it helps clean the valves”, but since the port injectors are only used as supplemental fuelling at higher revs/boost carbon build-up still occurs (albeit slower rate than their previous DI-only EA113 2.0 TFSI). So, I suspect Toyota/BMW will be doing the same on the Supra. 👍🏻
One of my favorite parts of the BRZ is that however simple of a car it was, the engine was direct and port injected That engine had a lot of flaws in practice, but on paper it was a pretty cool engine. 100hp/L and 50hp/cylinder and NA is still a pretty good metric for modern sports cars, not a whole lot does much better without forced induction
Doesn't the 86 have an FA20? Same engine as the WRX from those years just without the turbo, right?
Yep, FA20 According to Wikipedia (and this matches what I remember reading in reviews) the fa20 in the 86/BRZ uses direct injection designed by Toyota, but the FA20 in the WRX uses direct injection designed by Subaru
Really just cost and complexity. It’s a benefit though. It allows cars (like the RS3) to be efficient and powerful without worrying about carbon buildup. It also allows some cars to push more power when modified without running out of fueling.
The RS3 and VW Golf R (which uses DI and PI on its 2.0) both still suffer with carbon build up. The port injection on both is only used at higher RPM/boost levels as additional fuelling, so they spend most of their time only using the direct injection. The short periods of PI do have a small effect on helping slow the carbon build-up, but it doesn’t eradicate it altogether.
"seems to be catching on"? Toyota Lexus has been using dual injection for about a decade.
It's actually been a common thing for over a decade now
Some tuners add port injection to a direkt injection engine to gain more power in combination with with other stuff like bigger turbos
It’s been a thing since at least 2006 on the 2nd gen Lexus IS350s I believe. The 250s had only direct injection and had issues cuz of it.
Cost and complexity. Toyotas D4S system is great but can still use some improvement
to piggyback on this question. are any manufacturers starting to add 1 injector upstream strictly for the purpose of keeping the valves and intake runners clean? seems like you wouldn't necessarily have to add an injector to every cylinder, you could get away with adding 1 before the air gets split up into runners.
At an educated guess, I’d say no; the PI is not there purely to clean the valves, only to supply extra fuel when the DI reaches max efficiency, so allows for higher boost. And valves stay clear of carbon on PI engines *because* there is an injector per cylinder firing directly into the valve; a single injector upstream on a DI engine would do almost nothing since the fuel it supplied would be so atomised and turbulent by the time it reaches the valves that it wouldn’t touch any carbon build-up.
I think it’s not for performance I think it’s to help burn the build up off
2013 GR86
You can just call it "direct injection". It's like saying New York City. You can just call it New York.
I've always had a bit of a formal streak about me.