GDI Angles and DI:PI ratios discussion OFT

[Nah]

Just like the title says,

Why does changing your GDI angles increase responsiveness, what changes would you recommend for different setups. For example, Stock, el or JDL uel header, e85.

The best Total DI:PI table data for the different setups to complement your GDI angles.

And any other custom tables to further complement our tunes that may differ from the stickies we already have.

Awesome, thank you

[Nah]

I know there's information prior to this thread but if anyone would like to share their setups and explain why you made the changes for positive results that'd be awesome thanks. I like testing as much as possible

[steve99]

Originally Posted by Nah

I know there's information prior to this thread but if anyone would like to share their setups and explain why you made the changes for positive results that'd be awesome thanks. I like testing as much as possible

assume you have seen here

http://www.ft86club.com/forums/showthread.php?t=71506

unfortunately changing stuff like pi/di and gdi angles is a complex subject and you likely need dyno time to see any effects.

one of the most relivant posts

http://www.ft86club.com/forums/showp...2&postcount=17


ie best to leave that stuff alone unless you have a specific reason for change like larger port injectors or your running boost on E85 and you maxing out DI.

OFT guys did make some changes to GDI angles, shiv has years of experience, best run with what he has done.

The port injection is also their for cleaning benefit to intake valves and intake ports. full DI engines have problems with carbon buildup on intake valves / ports

[Nah]

Yup very good posts... I guess I want numbers.. In one of your threads, you suggested we make a change in the 0.2 load area of those total injection ratio tables to 0.

What does that do?
What would happen if I made the value .1, .5, or 3.5?

Originally Posted by steve99

assume you have seen here

http://www.ft86club.com/forums/showthread.php?t=71506

unfortunately changing stuff like pi/di and gdi angles is a complex subject and you likely need dyno time to see any effects.

one of the most relivant posts

http://www.ft86club.com/forums/showp...2&postcount=17


ie best to leave that stuff alone unless you have a specific reason for change like larger port injectors or your running boost on E85 and you maxing out DI.

OFT guys did make some changes to GDI angles, shiv has years of experience, best run with what he has done.

The port injection is also their for cleaning benefit to intake valves and intake ports. full DI engines have problems with carbon buildup on intake valves / ports

[steve99]

Originally Posted by Nah

Yup very good posts... I guess I want numbers.. In one of your threads, you suggested we make a change in the 0.2 load area of those total injection ratio tables to 0.

What does that do?
What would happen if I made the value .1, .5, or 3.5?

That was just idle stability, we found better way is to adjist idle timing compensation tables.

most people that mess with pi\di end up finding it does very little and just end up using stock pi di tables unless you have changed something like bigger port injectors

[Nah]

oh my idle is a little bouncy in the fl heat, do you have any suggestions on what to Change for a stabile idle and take off?

Originally Posted by steve99

That was just idle stability, we found better way is to adjist idle timing compensation tables.

most people that mess with pi\di end up finding it does very little and just end up using stock pi di tables unless you have changed something like bigger port injectors

[steve99]

copy the idle compensation tables out of waynos tunes he posted up here

use standard pi\di

[Xero-Limit]

The PI/DI ratio should be left stock on NA cars. We've found 0 gains by going DI only--the PI actually doesn't hurt power/knock until a very high percentage. For FI and bigger injectors you have to adjust these to balance out the ratio in order to prevent injecting into the spark with DI. This varies greatly depending on the cam timing and ignition advance. At this point is where you need to start tweaking the actual DI angle where you start to fire. In theory, you want the DI to finish injecting just as the piston is coming up to TDC and the spark is about to go off. The closer you get to that point the more power you make--but also the greater the risk of knock. So it is a very careful balance. On the BRZ it makes little difference because of port injection. It helps to homogenize the mixture and you don't get the stratified effect. On the WRX and DI only vehicles this is much more critical. Screw it up and you can blow the DI seals a lot quicker and you'll get some uncomfortable misfires. You'll also find a much greater instance of motor failures despite similar bottom ends.

[Nah]

Awesome this info definitely enlightened me. Appreciate it.

So on our platform... While tuning with romraider.. What are the benefits of dialing in both port injection and direct injection? Jamesm on that video says to dial in both... Would I even need to and how would I if I use a MAF scaling tool.

Thank you.

Originally Posted by moto-mike

The PI/DI ratio should be left stock on NA cars. We've found 0 gains by going DI only--the PI actually doesn't hurt power/knock until a very high percentage. For FI and bigger injectors you have to adjust these to balance out the ratio in order to prevent injecting into the spark with DI. This varies greatly depending on the cam timing and ignition advance. At this point is where you need to start tweaking the actual DI angle where you start to fire. In theory, you want the DI to finish injecting just as the piston is coming up to TDC and the spark is about to go off. The closer you get to that point the more power you make--but also the greater the risk of knock. So it is a very careful balance. On the BRZ it makes little difference because of port injection. It helps to homogenize the mixture and you don't get the stratified effect. On the WRX and DI only vehicles this is much more critical. Screw it up and you can blow the DI seals a lot quicker and you'll get some uncomfortable misfires. You'll also find a much greater instance of motor failures despite similar bottom ends.

[freerunner]

Originally Posted by Nah

What are the benefits of dialing in both port injection and direct injection? Jamesm on that video says to dial in both...

On my car with stock calibration the amount of PI was too high, actually caused the car to run too rich.
Running in closed-loop ECU (AFR target = 14.7) detects too rich combustion and compensates with a positive fuel trim ending with LTFT going up.
Problem is there are load ranges where more or less PI is added or even none at all.
So LTFTs will go up or down, depending on the amount of load put on the engine:
Just an example: MAF cell target at 2.0V could be spot on under very light loads but off under moderate/high loads.

Like jamesm already said, you're going to chase your tail if PI injects different amounts of fuel than DI while scaling your MAF sensor.

I noticed that wayno took care of that in his latest A01G example revision (found out that he ended up with quite a similar PI injector scalar I came up with - gladly because I was not really sure if I headed into the right direction with the result I got).

[Wayno]

Changing the port scalar only changed the LTFT, it doesn't change the AFR.
X% more scalar with -X% more LTFT = exactly the same AFR.

The change is ONLY for better AFR's before the ECU has adapted, no other reason. It's NOT to change the AFR.

Originally Posted by freerunner

On my car with stock calibration the amount of PI was too high, actually caused the car to run too rich.
Running in closed-loop ECU (AFR target = 14.7) detects too rich combustion and compensates with a positive fuel trim ending with LTFT going up.
Problem is there are load ranges where more or less PI is added or even none at all.
So LTFTs will go up or down, depending on the amount of load put on the engine:
Just an example: MAF cell target at 2.0V could be spot on under very light loads but off under moderate/high loads.

Like jamesm already said, you're going to chase your tail if PI injects different amounts of fuel than DI while scaling your MAF sensor.

I noticed that wayno took care of that in his latest A01G example revision (found out that he ended up with quite a similar PI injector scalar I came up with - gladly because I was not really sure if I headed into the right direction with the result I got).

[Nah]

Quick question, how have you been able to fix ltft at idle without touching the maf curve? Currently dialing in the D.I. system, I've been using GDI pressure multiplier tables to dial the D.I system in. It works really well but, at idle nothing ever happens? lol hope that makes sense... thank you!

Originally Posted by Wayno

Changing the port scalar only changed the LTFT, it doesn't change the AFR.
X% more scalar with -X% more LTFT = exactly the same AFR.

The change is ONLY for better AFR's before the ECU has adapted, no other reason. It's NOT to change the AFR.

[steve99]

Originally Posted by Nah

Quick question, how have you been able to fix ltft at idle without touching the maf curve? Currently dialing in the D.I. system, I've been using GDI pressure multiplier tables to dial the D.I system in. It works really well but, at idle nothing ever happens? lol hope that makes sense... thank you!

When the ecu is using both injection systems like at idle you just changing balance between the ststems, the ecu will still target same afr the ltft may change very slightly as the ecu targets the same afr using a different balance in the pi and di systems.

The other thing your fighting at idle is the maf temp compensation due widly varing temps of intake air at idle. this make ltft drift more at idle.

when your running purly on say di system like in mid rpm ranges then you will see more change in lft when you change the di pressure targets.

i would not mess with this stuff, especially on a NA car with stock injectors.

get you maf scaling correct, may then try the maf temp compensation to get that a bit better.

and only when thats sorted maybe adjust just the port injector scaler usually down a few percent to balance pi\di, but its really not necessary on stock system

dont try and fix ltft with pi\di balance alone

[Nah]

Well, what I did was this... I maxed out my DI then reduced or added fuel... Got a clean pattern and smooth fuel curve where LTFT would be very close to 0. so I dialed in my MAF to that curve... Then I added PI did the same thing. Dialed it in then adjusted MAF at the very end to ensure everything is still smooth. This method worked better than just scaling my MAF... Honestly downshifts and cruising power dramatically increased however Whether my system is messed up or not please let me know... For NA it worked great and was a very straightforward process. gonna try it on e85 next.

Originally Posted by steve99

When the ecu is using both injection systems like at idle you just changing balance between the ststems, the ecu will still target same afr the ltft may change very slightly as the ecu targets the same afr using a different balance in the pi and di systems.

The other thing your fighting at idle is the maf temp compensation due widly varing temps of intake air at idle. this make ltft drift more at idle.

when your running purly on say di system like in mid rpm ranges then you will see more change in lft when you change the di pressure targets.

i would not mess with this stuff, especially on a NA car with stock injectors.

get you maf scaling correct, may then try the maf temp compensation to get that a bit better.

and only when thats sorted maybe adjust just the port injector scaler usually down a few percent to balance pi\di, but its really not necessary on stock system

dont try and fix ltft with pi\di balance alone