Controlling large Injectors (720cc)

[supraguy31]

Hey you all.

Just wondering that you all are doing out there that are running 680+ size injectors to get them to Idle smooth. Im running Greedy 720cc and once the Idle Drops down below it starts to run pretty rough. I have the FP set to 40psi vacuum line off.

Anything above 800rpms seems to Idle fairly decent so I figured that this would be the Place to go and ask.

Is it because the stock ECU cant control that amount of fuel at Idle. Im running a MAFT Pro but Im sure that doesnt have anything to do with it. At this point Im thinking that Im getting into the relm of Standalone.

Thanks
Robert

 

[figgie]

big injectors of the low impendance variety have pintle bounce at low pulse width.

What is pintle bounce?

best way is to show you.

Paul Yaw over at injector Dynamics.

http://www.injectordynamics.com/ID2000.html

notice the graph, especially at low pulse width. You see a spike around 1.2-1.4 ms. That bounce is what causes the crap idle (sub 1k if you are lucky). Of course you are running 720cc injectors and not 1600cc/min so the problem is not as aggravated as the 1600cc/min injector but the pintle bounce is still there.

There is your answer

 

[suprahero]

Deleted the above post. I skipped the part where you have the Maft Pro. I don't know anything about that since I've never seen one around here.
Can you adjust your fuel using that like you can the AFC?

EDIT: Looks likd Figgie has the answer for you.........good luck.

 

[IJ.]

Made worse when batch fired.

 

[grimreaper]

maft pro is like the afc, just more features. Since we cant chip the stock ecu (yet) id have a standalone installed LONG before i swapped out my 550's...

 

[supraguy31]

That is what I was thinking that the Stock ECU just cant handle it. Looks like Im going to be in the Search for a Standalone that will do the trick.

So Since most standalones have boost control capabilities Im going to put the entire MAFT Pro setup and the HKS EVC IV boost controller up for sale. Hopefully I can get enough to offset some of the cost for a Full Standalone.

 

[figgie]

That is what I was thinking that the Stock ECU just cant handle it. Looks like Im going to be in the Search for a Standalone that will do the trick.

So Since most standalones have boost control capabilities Im going to put the entire MAFT Pro setup and the HKS EVC IV boost controller up for sale. Hopefully I can get enough to offset some of the cost for a Full Standalone.

It is not a function of the TCCS. It is the fuel injectors.

Even with a standalone, idling big injectors is a chore and a half and sometimes, improbable below 1000 rpm. That is related to the pintle bounce caused by the mass of the pintle, also being low impendance causes a surge in current which opens the pintle "hard".

 

[dbsupra90]

i've had precision 680cc for quite a while. had them with a lexus afm and safc, original maft and safc, and the maftpro. all idled very well at stock idle. altho i did have lower bfp (32-36psi).

here is a video w/ the 680cc, maftpro, bfp at 34psi, aeromotive a1000 pump and 800 rpm idle.

http://www.youtube.com/watch?v=gOfq1CzMHWU

 

[supraguy31]

i've had precision 680cc for quite a while. had them with a lexus afm and safc, original maft and safc, and the maftpro. all idled very well at stock idle. altho i did have lower bfp (32-36psi).

here is a video w/ the 680cc, maftpro, bfp at 34psi, aeromotive a1000 pump and 800 rpm idle.

http://www.youtube.com/watch?v=gOfq1CzMHWU

Is that 32-36 Vacuum off or on?

Is Lower FP really a Bad thing if you can get them to Idle Better. Im only having this Problem at Idle, When Im cruising the car runs great. Even when the car is in its cold start stage and at Higher Idle its runs Smooth, Once it Drops down to to where VF starts to read on the MAFT Pro and the Idle Drops to 700rpms or so is when it get somewhat choppy or bumpy...

 

[dbsupra90]

base fuel pressure is always referenced with no vac. i always set bfp by jumpering +B and Fp and the car not running.

do you have after start idle enrichment turned on?

any tuning done on the mpro?

 

[supraguy31]

base fuel pressure is always referenced with no vac. i always set bfp by jumpering +B and Fp and the car not running.

do you have after start idle enrichment turned on?

any tuning done on the mpro?

Ive always heard that you Set the BFP while the car is running. Never heard of setting it by jumping the FP connector. If this is better by all means LMK.

I have Afterstart enrichment but Its set at 0.0 in the MAFT Pro settings. Initial startup of the car is Extremely rich like 10.5 to 11.1 AFs

As far as tuning, there hasnt been much done other than Cruising and A few WOT pulls to get the A/F in the mid 11 Range. She runs great but with the 720s, Im going to have to pull some fuel out at WOT.

 

[sk6471]

i've had precision 680cc for quite a while. had them with a lexus afm and safc, original maft and safc, and the maftpro. all idled very well at stock idle. altho i did have lower bfp (32-36psi).

Are the 680s low impedance?

 

[figgie]

Are the 680s low impedance?

very few "import" injectors are high ohm... very very few.
Those greddy are low ohm.

dbsupra

since the base fuel pressure is not the standard 45 psi. The lower base fuel pressure in essence CHANGES the flow limits of the injector downward.

So those 680cc/min at a base fuel pressure of 36psi will now flow max of 618ish cc/min...Of course forget the atomization portion for now.

 

[grimreaper]

also keep in mind the rising rate fpr. if you set base at 30 psi you'll be right around 60psi at 20psi of boost. VERY critical to map it out when choosing fuel supply. You can easily get into dead head ranges with to much base pressure.

If your not seeing 650rpms (+/- 20 rpms) at idle on a stock tccs, somethings not 100% correct.

I always set it with the car running, higher voltage then just jumping B+ and FP. Depending on where the charge on the battery is at Ive had 2-3 psi difference in base pressure.

 

[TurboStreetCar]

700's here on the 8860, idle is smooth as silk. Still on stock fpr untill spring runs very well.

 

[jetjock]

As long as the system is balanced the stock ECU will run those injectors just fine.

I always set it with the car running, higher voltage then just jumping B+ and FP. Depending on where the charge on the battery is at Ive had 2-3 psi difference in base pressure.

That doesn't make sense...

 

[grimreaper]

i assumed it was the voltage difference. 12v "mod" with a measured 9v at the battery showed a slight bump in pressue when i started the car. Never dug deeper, havent touched fp in quite a while. Ill have to double check that this week then.

 

[bfr1992t]

I have Greddy 720's (base FP 43psi). It idles fine from 500rpm, ~30kpa and up with an AEM EMS. Previously I had no idle issues using the stock TCCS, VPC, and AFC combo with up to 50psi base FP.