hard start after new injectors

[smokeshow]

Just installed some Siemens Deka 60s in the truck in my sig. Idles fine, runs great, but it takes several seconds to crank up and just barely manages to get going. After that, it acts 100% normal. I can't imagine the starter is liking this extra workout.

I thought it might be the cranking enrichment in the FA Mult Stage 1 vs Time table, so I tried decreasing the ratio since the injectors are larger, but it didn't change anything. It was a bit of a shot in the dark anyway.

Anybody had experience with this issue on a Gen4 engine before? Tune and log of startup is included.

[4evervette]

didnt open ur tune... have u change the injector data ... IFR ,,ofset inj.mpw etc ?!

[DSteck]

As stated... Did you enter all the proper data for the injectors? There are more tables than just flow rate. Did you enter flow rate properly for that matter.?

[IDRIVEAG8GT]

As stated... Did you enter all the proper data for the injectors? There are more tables than just flow rate. Did you enter flow rate properly for that matter.?

+2.

[smokeshow]

Yes, I made changes to the IFR table, short pulse adder, minimum injector pulsewidth, and injector offset. It runs fantastic at idle and any range from there to WOT.

[redheartbeat]

Did you by chance happen to change out the fuel pump when you did the swap to the larger injectors? It sounds like your fuel pressure has bled off and there in none in the fuel lines. Cycle the key a few times and be sure there is fuel rail pressure when you start it and see if you have the same issue. I've seen guys put pumps in that don't hold the fuel pressure after shutoff have the same issue. A simple fix could be a momentary push button to run the pump a few seconds before starting if that is the problem.

[smokeshow]

No, theres pressure in the lines all right. I watched it on my fuel pressure gauge and in the log. It never drops below 58 in the log.

[bpt tunning]

that ifr looks a lot like the factory flex fuel injector data

[smokeshow]

that ifr looks a lot like the factory flex fuel injector data

The IAT modifier table multiplies those values by 2.

[DSteck]

The IAT modifier table multiplies those values by 2.

If you're trying to beat the 63.5 lb/hr flow rate limit of injectors... then what you did doesn't work.

[smokeshow]

If you're trying to beat the 63.5 lb/hr flow rate limit of injectors... then what you did doesn't work.

Really? I got that recommendation from Justin at Blackbear tuning. He definitely knows his stuff and I doubt he'd steer me wrong.

[DSteck]

Everybody always knows their stuff.

[smokeshow]

Everybody always knows their stuff.

Well I am still looking for suggestions from the people that do...

[IDRIVEAG8GT]

I think Steck called it right, and it needs to be re-scaled. However, if it's a hard start, Startup Airflow tables and adjustment of start up timing would be the easy way out of your situation.

[Sherminator]

Or just run injectors that you can properly calibrate for. A 60lb injector is good for what like 800-900hp or more at 58psi. You have is a stock 5.3 with 10psi looking at your sig. can't see that needing those injectors.

[smokeshow]

I think Steck called it right, and it needs to be re-scaled. However, if it's a hard start, Startup Airflow tables and adjustment of start up timing would be the easy way out of your situation.

I've had several people say that, and I'm not discarding your suggestion, but why would I need to make airflow adjustments for just an injector swap? Is that just a simple fix to trick it into thinking its getting less air so it delivers less fuel? Forgive me if thats a dumb question; I haven't done any VE adjusting yet, as this is the first vehicle I have tuned. I did plenty of research before installing the injectors, and wasn't expecting the hard starts. It runs perfect aside from the starting issue.

Or just run injectors that you can properly calibrate for. A 60lb injector is good for what like 800-900hp or more at 58psi. You have is a stock 5.3 with 10psi looking at your sig. can't see that needing those injectors.

Tell that to the 120% IDC with my old 42lb injectors...

[DSteck]

You need to scale the tune. That bullsh*t with setting the IAT vs. Fuel Flow multiplier to 2 doesn't work. Your injectors are passing the 63.5 lb/hr hard coded flow rate limit.

Also, where'd you get the injector data?... Because it's not right for the SD60s, tall or short.

[smokeshow]

You need to scale the tune. That bullsh*t with setting the IAT vs. Fuel Flow multiplier to 2 doesn't work. Your injectors are passing the 63.5 lb/hr hard coded flow rate limit.

Also, where'd you get the injector data?... Because it's not right for the SD60s, tall or short.

Wouldn't it have driveability issues if that multiplier didn't work? Not saying you are wrong, but it runs perfect other than the starting issue. From idle to full boost, AFR is exactly what it was before with the old injectors.

I got the injector data from a spreadsheet calculator, not sure who the author was.

[IDRIVEAG8GT]

Yep. What I suggested is the quick and simple fix because it seems that those injectors in fact, have calibration data equivalent to what a set of 67 Lbers are for Bosch's that were in a CTS-V that I tuned here not too far back. Proportionally, the top part of the offset is way off compared to a fairly close bottom. Anyways, when you recalculate airflow it just holds the throttle body at a different position for more airflow to accommodate your fueling issue.


Steck is going to call me a newb for suggesting this but FIC sells redrilled 60Lb injectors that start life as ZR1 injectors. But the IFR data hardly changes at all compared to a ZR1. That's what I have in the newest addition to the family of Silverado's sitting around my place with a 415 and they are fantastic.

[DSteck]

Steck is going to call me a newb for suggesting this but FIC sells redrilled 60Lb injectors that start life as ZR1 injectors.

Please stop telling people to buy crap. That's exactly what those are. You'd puke if you saw what the flow looks like coming out of redrilled injectors. Some of them just shoot a garden hose looking stream, which is bad.



OP, that multiplier table is cracking your injector flow rate up to 63.5 no matter what, and closed loop is fixing things because fuel delivery is generically close enough.