Datalogging IDCS

[Lofty]

I recently got a manual boost controller. I am having a bit of phantom knock on my logger, whatever that's fine.
I have a JDM Evo engine in my car.

At 14 PSI my IDCs are only at 60%. Is this normal for a stock dsm?

It doesn't seem normal.

No knock under boost. It's healthy and happy at 14 psi.

Any ideas?

 

[viprez586]

If your running a 14b. And it really is a JDM EVO engine like you say. Pretty likely that 60%IDC is good.

I believe the JDM motors came with somewhere around 550cc injectors. Combine that with only 14psi on a 14b...even a 16G...your not flowing that much air. Why complain about low IDC% anyway?

 

[snowborder714]

If you can log airflow, you can use this info to see how close in line you are to the calculations.

Obviously you didn't believe me the other night when I said you were fine

 

[habitatguy187]

Like Viprez said I know alot of the jdm motors come with evo 560s, which will have you running super rich under boost since the 450s are already in the 9s af-wise on a stock car when under boost.

 

[the_mork]

His motor did not come with 560s. It may have come with 510s but I suspect not and even so it would have nothing to do with duty cycle. Duty cycle is calculated off of pulse width and rpm.

Lofty, there is a lot that goes into how much fuel you need. Basically boost is not a good indicator when there are as many variables as there happen to be when trying to figure out fueling. Temperature, barometric pressure, humidity, and other atmospheric conditions will do a lot to change your airflow from one day to the next, on top of that comparing one car to another at the same boost will depend entirely on the VE of the motor. At 14psi with a stock sidemount, stock exhaust, stock intake tube/filter, and stock pipes a car will have significantly less airflow than the one next to it also at 14psi that has opened up a lot of those restrictions. More than anything else it is the guy with a lot of boltons that has to be careful how high the boost goes whereas the stock guy can make a lot of the same power just by turning up the boost more. This is why it is stressed that logging IDC is the only safe way to know how much boost you can have and if there is no way to log it the answer is generally don't go about 14psi. This is also part of the reason why I advocate tuning and injectors before most boltons.

So, want to go fast? Turn up the boost some more. It looks like you can do it but make sure not to go about 80%idc and log often because when it gets cold again you're going to quickly run out of injector. Also taking a single log and seeing 60% idc isn't a whole lot better than useless, do it again and again. Also remember that you're usually going to need more fuel in a fourth gear pull than a second gear pull so make sure you aren't just flying through the power band and thinking you have a lot of headroom.

 

[habitatguy187]

His motor did not come with 560s. It may have come with 510s but I suspect not and even so it would have nothing to do with duty cycle. Duty cycle is calculated off of pulse width and rpm.

I was thinking that evo3 injectors were 560s, my bad. And that's an interesting note about how IDC is calculated, I never thought of that before.

 

[viprez586]

For how much boost he's running on a specific size injector will greatly affect how his IDC%s are being affected. The ECU is going to try to correct for additional boost(or target AFR rather).
I was pushing into upper 80% IDC (w/ 550cc)with my current setup @ around 18-20psi. I swapped in Denso 720cc injectors and my IDC% has dropped to mid 40s still at same boost level and everything.


I was being lazy in my post, sorry for not being more specific.

 

[spooling 1g]

I was thinking that evo3 injectors were 560s, my bad. And that's an interesting note about how IDC is calculated, I never thought of that before.

Evo 3's are 510cc and have a yellow top.Evo 8's are 560cc and have a tan top.but someone correct me if im wrong but i have both sitting here.

 

[1995gsx20g]

i also had evo 8 or 9 (i can't remember) 560cc's and they were pink.

 

[jrohner]

Log MAF Hz to give us an idea of what airflow you're seeing (unless you're using a program that actually shows airflow, then that's better yet).

Also, I'd be very surprised if you actually have an Evo engine in a 1G. You probably don't realize all Evo's are 7-bolt engines -- why would someone go through all the extra work?

 

[the_mork]

For how much boost he's running on a specific size injector will greatly affect how his IDC%s are being affected. The ECU is going to try to correct for additional boost(or target AFR rather).

Only for the sake of being absolutely clear I want to expound upon this a bit. The ecu has no idea how much boost is being run. It has no sensor to determine either absolute or relative pressure in the intake manifold or anywhere else. 2gs have an MDP but it is only 1bar and therefore not capable of reading boost anyway plus it is only used for EGR.

Therefore the difference in IDC is going to be a matter of airflow. You can run 25lbs of boost and if you're still pushing that air through a straw to make 30lbs/min of airflow you're not going to use much of your injector. Now, loosen up some airflow restrictions and still hit your low 30lbs/min figure at 15psi and you'll see the injector duty is the same. Your ecu and your injectors don't care about your turbo, your boost controller, your exhaust, intercooler, or any other part on your car. They care about the factory constants provided within the ecu memory, the MAF readings, the tachometer, and the formula that was programmed to determine when and for how long to fire the injector.

 

[viprez586]

Agreed. Lack on my part of going more in depth and explaining like you did.

 

[Lofty]

The engine and trans code on my car says Galant Vr4 EVO 1
It's a 6 bolt. With the JDM mitsu valvecover.
It had the evo gears in the transmission..... Tim Zimmer can vouch for these as I sold them to him.

 

[clockworktoy]

Another thing that will have an effect on IDC's is fuel pressure, if your runnning a stock pump and say 14psi and your pushing 80% IDC's and switch to a 255 you can drop your IDC's by say 15% because of the added fuel pressure available. I really don't think your running 510's without any type of compensation in the ecu for that ~13% difference in size.