Starting Isssues w/ S-AFC + Injectors

[mnetwork]

Ever since I put in my injectors my car starts very oddly. Either two things will happen, either it will only take a half a crank, start, and sputter for a sec or two and run fine, or it will take a lot of cranking and then start... I never had this before until I put the injectors in and I've been trying to tune the S-AFC..

 

[olmytsi]

What injectors and what are your afc settings? Make sure the injector wires are plugged in correctly and none of the seals are leaking.

 

[mnetwork]

The wires are plugged correctly, there are no leaks, and my low settings are around -23...

I have PTE 680's and the rest is in my profile..

 

[GVR4592]

Do you have a datalogger? -23 is going to be pretty rich, you should be somewhere around -30 if your fuel pressure is at 43 psi.

 

[thilaksharma]

in my opinion , the SAFC will not be able to help much
## injectors arent small to compensate using SAFC even if u -/+ 100%
680 is a big number

 

[iiiwildfireiii]

Uhm...how would a SAFC not help much? 650cc injectors are 31% bigger than the stock 450's. 680's aren't much bigger. SAFC's have the capability to do +-50%. My settings on my 650's are at -12% at idle. Taking out any more than that and the ECU begins to add fuel. You ever stop to consider that the larger injectors have a lot longer dead time than the stockers?

 

[steve]

(stock injector/new injector) - 1 = correction factor

450/680 - 1 = -0.3382 = -34% assuming no change in base fuel pressure and ignoring any difference in deadtime. Since some injectors flow more than others it's always a good idea to have your injectors flow tested.

Steve

 

[mnetwork]

I tried running at -34 when I first put the injectors in, it was wayyyy to lean... so I upped it..

 

[steve]

Like Breven was saying, since those PTE injectors have a sigificant increase in dead time over a stock 450 you'll be reducing the correction at idle and lower RPMs to make up for the lost time that the injector should be spraying fuel and isn't.

Deadtime errors make a bigger difference at low rpm/low load than at high rpm/high load so as injector pulse widths increase the error is a smaller percentage and the corrections should be closer to the calculated value.

Steve

 

[BeerBaron]

My experience has been different in terms of compensation for injector size with safc. I know they say -33 for pte 650's (680's). but i foud that was way too lean. I was running 650's with vpc and a 16g for a little while, and never really managed to get a good tune on it. i was playing between -30 and -20 and still couldnt get rid of knock and tried going as lean as -35 but that was obviously too lean. I then went to a 2g maf with 550's and ran it with out afc for a while; it still knocked but not as bad. A couple days later i was fed up with it and put my afc2 back in. I figured it was running rich with no compensation so i tried pulling fuel out. Knock got worse i tried going as lean as -10 but that was clearly too lean as my knock cout was 43. As my set up stands now i have a 16g running 20lbs with a 2g maf with a 255 pump, afpr (new fuel filter as well). Currently i am ADDING fuel and have goten knock down to 8-10 counts. My high settings start at +2 at lower rpm and curve up to +5 at higher rpm. I have buddies runing a similar set up and compensate as low as -10 for 550's with a 2g maf. Now i don't have a wideband so i dont know what my a/f is at but i get the least knock with these settings. To me this jsut goes to show that every car is different, and you cant really go by other poeples afc settings. And also for 2g's a wideband is really helpful.

 

[mnetwork]

I still don't know what I should do or check with this problem... I am only having a problem starting the car, not when it is running or idling. I do not have a rough idle or anything like that. Is there anything involving injectors that would cause this issue? It only seems to happen when the car has been sitting for a while... Like over an hour...

 

[iiiwildfireiii]

Well, I don't see an AFPR in your profile and you're running a rewired 190. Possible fuel pressure issues during hot start? What's your coolant temps when you're trying to restart it an hour or so later? Also, do a search for "Hot Start". I swear that there was a big thread about this a while ago, but I don't have time to look for it now. I'll check later too.

 

[mnetwork]

It isn't really a hot starting issue.. it is the issue of starting after it has been sitting for a while. This includes sitting overnight...

And why would I need a FPR for a 190.. this pump does not need one, the 255lph and higher needs one...

 

[dr1ftx3]

mnetwork i'm having the same startup issue. This is right after I put in 16g,580 injectors, 190 fuel pump etc. Before the upgrade it barely turned once, now it takes 3-4 cranks to start up. Its really annoying. =\

 

[steve]

The standard answer for problems starting after sitting and the fuel pump has been replaced is to check the o-ring on the top of the fuel pump and make sure that it's seated correctly.
If you have a fuel pressure gauge you can check to see how quickly the pressure comes up when you turn the fuel pump on. It should be instantainous.

Steve

 

[mnetwork]

Yes, that is a very common issue. If I had just changed my fuel pump at the same time, that would have been the first thing I checked. Any one have ideas on this. It doesn't make any sense to me. The car runs fine, no rough idle, but starts like crap...

 

[mnetwork]

I don't know what to do and I am really confused with this.. I narrowed it down to certain times now.. It doesn't happen on a total cold start (when the car has been sitting over night), and it doesn't happen on a very hot start (car has been sitting for a few min), it only happens on warm starts (when the car has been sitting for like an hour or a few hours)... I don't understand this problem, I would really appreciate some feedback on this..

 

[GVR4592]

What exactly have you done to try and correct it? Do you have a datalogger?

 

[mnetwork]

I have checked all connections, maked sure everything is tight, don't see any gas leaks, and I have tried messing with the s-afc, but the s-afc has nothing to do with starting the car.... Yes, I do have a data logger.