I have an accel dfi gen 7 system and I have a starting issue with it.

When it's cold I start it and it dies. I start it again and it dies. The third time I start it away it goes and it runs and idles fine.

When it's hot (as in 180-200 deg.) and I start it the idle hunts up and down. It is a surge from about 200 to 700 then back to 200 and back to 700 RPM.

I am a little bit confused as to what to try as far as fixing this goes. I have the starting fuel, afterstart fuel, afterstart decay. What is the sequence of operation as to when the ecm looks at these tables and what suggestions do you have as far as what to try changing. When does the decay modifier table come into effect?????


I'm new at tuning fuel injection and would like some pointers.

Thanks,
Justin

 

Are you using a wideband o2 ? Have you set your VE tables yet ? What is your timing at those map pressures around where your car is idling at ? If your car is hunting for an idle when hot what is your idle spark control set at ?

To start off when you first crank it and it dies, how long is it running for ? Is it stumbling then dying ? or is it running for 5-10 seconds then dying ?

 

 

The base VE tables are tuned correctly as far as I know. The system was put on by a dyno shop and initially tuned by them. The idle thing has been a problem since the day I picked it up. I could take it back and have them fix it, but I would like to fix it myself so that I can learn about it.

I am not using a wideband O2.

My ignition idle control is set at the follow at 151.25 deg. and 189.5 deg. engine temp. (setting are the same for both)

First number is the difference in actual idle speed to target idle engine speed. The next is the amount of timing added or subtracted.

-160 = 6.5
-120 = 5.25
-80 = 4.0
-40 = 2.75
0 = 0
40 = -2.75
80 = -4.0
120 = -5.25

At idle right after startup when warm with map at 47-50% total advance is 26.5-27.5.

On a little longer datalog (2 minutes) MAP was up and down between 42% and 46% and total advance was between 19 and 24 degrees.

Initial startup I would say it stumbles then dies. It probably runs for 1 second max. The third time when it does finally run it takes about a second for it to get up to idle. It doesn't fire right up to idle speed, it starts slow then moves up.

-Justin

 

Justin, before I go further I'll tell you my experience. A few months ago I didn't even know which way was lean and which way was rich when it came to air/fuel ratios Now, I am very familiar with the gen7 and almost know how to get every desired result out of it when it comes to starting, afrs, smooth idle etc etc.

What I can also tell you for sure though, is there is WAY more satisfaction doing the tuning yourself. Sure there are pros out there, but I would rely on them if a) you have a big wallet and b) to do more of the fine tuning and wot tuning. or c) you find someone who is knows the Gen 7 throughaly and can tune your car 100% withouth making you re-mortgage your house. ( i couldn't find any - the only accel reccomended tuner in Canada todl me the car will want 10.5 afr at wot... I hung up )

The way I think, is that the car is Mine, and if I wanted to try every thing I possibly could think of to get it to run the way I want, I can. And my time is free (sort of). I'd be pretty upset because of how picky I am if I had to take my car to a tuner every time something bothered me, and not to forget - broke) . I don't know of any competent tuners anywhere in Canada near me that know how to tune this sytem from scratch so I really had no choice but I can honestly say it's not very hard at all.

you need to get a wideband 02. if you go with the accel unit it is plug and play. Plug it in and it shows you the actual afr and correction. its all simple from there. if you do decide to go that route I'm more than willing to help in any way I can. iron out the VE tables using overlay. Set the afr where you want it. I'm still figuring out exactly how to determine where the best timing is, but after that it's all fine tuning.

 

On a more direct and helpful note, can you provide any basic details of the motor ? do you have the cam card ? if so you should be able to figure out the injector timing from there. i chased that one for a long time where it was set to 360 degrees when it wanted to be at 630 degrees.

I have a hard time believing they could have set your VE tables without using a wideband but hey I don't know everything. if you hve a wideband all you have to do is use the autocal feature, or just datalog and just drive, and then use the wideband correction as a multiplier to get your VE exactly where it needs to be. AFter that all you do is set your afr and it's automatically done.

With regards to your start-up, it almost sounds like your injector timing is off. Mine was and i had very sloppy response and startup. if not then are you smelling fuel (from exhaust) ? Sounds like maybe not enough ? Also check your timing curve vs ECT (engine coolant), you want more advance when the car is colder.

I'm not sure how big your cam is, but my Idle control is set to 2.5 degrees as maximum variance and my idle error is usually <100. I know yours is hunting quite bad but I don't know how big your cam is and/or if there's anything else in the combination that can cause this. Since yours is hunting from 200-700 I wouldn't worry about this just yet, I'd think this tabel is for ironing out <100-200 rpms at idle to keep it smooth.
(edit) also for idle do you have an IAC on the car ? the IAC settings can play a big part in idle quality. You can dampen the inputs the IAC recieves so it wont move too fast and make a larger cammed motor hunt for a smooth idle.
Also what is your target Idle set to ? Minimum IAC and maximum? how about the IAC at startup ? you can tell it where you want the IAC motor before you even start the car to help fire it up.
Perhaps to see if its a choking issue open the throttle slightly with your foot and fire it up. If it fires up much easier than your IAC or throttle blades may need to be opened up more for startup.

if you like shoot me a pm or email at psychowette@hotmail.com or keep posting here. Would love to try and help as much as I can.

 

I will post my cam card when I get home from work. It's not that radical.

Can I send you a copy of my data file to look over?

I will look a little bit deeper into some of what you said when I get home from work tonight.

Thanks,
Justin

 

Justin i don't need the cam card. I know some people like to keep it a lil secret so i didn't mean to just ask for it. Go into your fuel, target injector timing, then press f-1. it will tell you which #s to use to get your target injector timing close. I believe it is the intake valve closing angle after bottom dead center (or ATDC i forget). Feel free to send me any of your tables/files.

I still suggest investing in the wideband. It is the only thing that allowed me to know what i was doing.

 

I will check into that Target Injector timing.

My cam is a .467 lift intake, .494 lift exhaust, adv. duration 278 intake and 294 exhaust. There are no secrets regarding my motor. I built it myself and it's a nice setup. Making 310 hp and 390 torque at the wheels the day I took it home from the dyno shop so I'm relatively proud of it. I think there's more in it if I would go to a roller cam. (it's a hydraulic flat right now) I think the bigger cubes of the 406 could stand more cam.

I am considering the wideband option. Do you run the knock sensor too?

I am going to get on my other computer and send you my data file. If you wouldn't mind you could look it over and see if anything jumps out at you.

I really appreciate you taking some time to help me out. There's not much for resources to learn these accel systems out there. More to come later.


Thanks,
Justin

 

This target injector timing has me a little bit confused.

The number I enter in calmap is the degrees that coincide with the start of the inject cycle. I am supposed to enter that as the crankshaft degrees at BDC (540) plus the intake valve closing degrees. My intake valve closing is 41 degrees ABDC, so 581 total crankshaft degrees. Why would I start the injector timing after the intake valve is closed? Is it that it injects behind the intake valve where the fuel sits and waits, then all gets sucked in as once when the intake valve opens so as to prevent mixture deficiencies cause by varied air flow past the valve? I mean, I was always under the idea that fuel injection was supposed to inject directly in front of the intake valve when it opens and directly fill the cylinder.

Any help with this one? I hope this isn't too dumb of a question, but I've always been a carburetor kind of guy and this is my first fuel injection tuning so please be patient.

-Justin

 

Justin that's exactly what I was wondering. You have it right on though, add the 520 to the closing angle and thats a number to start with. Reason being is I was told when the valve is closed, the injector fires it then at the back of the hot valve and it helps mix it when the valve opens. I'm sure someone else can explain it better but its along those lines. i can tell you that my target injector timing is set at 630 degrees right now. the accel tech told me to try varying that number up and down 90 degrees, and said watch your wideband o2 and where it runs richer should be the ideal target timing.

I really do suggest getting a wideband. You can leve it in and it will tell you ALL the time how the car is running and at what air fuel. you can see how rich or lean it is at startup, deccel accel etc etc. People told me I needed one and I didn't think it was necessary at first but I was so lost until I plugged it in.

Going to check your files right now...