XFI tune issue..Inj. dc spike in first gear...tune and log file enclosed

[STP]

I'm working on turbo Buick with an XFI 2.0 system and cannot find where the issue is in this tune. Hopefully one of the FAST hotshots here can have a look and give me an idea of whats going on. At the hit the inj dc shoots up to 100% and I get around 5* of knock with O2 correction...Once the car shifts to second, I get no knock whatsoever and around 80% inj dc WITHOUT the addition of alky. In the neighborhood of 17-18psi with 17* of timing. This on a 109 iron headed stroker with 65lb injectors, pump 93 octane, and a single nozzle alky setup. The car comes up fast and spins the drag radials pretty good through 2nd gear. Things I've tried are: raised MAPvs.AE fuel...didn't help at all turned alky off and revised the VE table...no change according to the logs...the VE is fairly close until I get the spike in the inj. dc...Then it starts dumping fuel in and pulling timing. I don't believe the car is really pinging as I have yet to hear it...How do I get this spike out of it?? Is tire spin causing it or possibly the gear change???

 

[STP]

Ok, I'm having issues uploading the log and gct...Any suggestions??

 

[STP]

Lets try this...

 

[kidglok]

im looking at your gct, were u running alky in the tune you posted?

 

[turbobitt]

My guess is that there is a fuel pressure issue. Looking at the log, I would think that you are almost out of injector. Looks like the DC% stabilizizes at 85+ percent. It appears to have a lot of correction when ramping into boost. Coincidently the knock retard is happening near the higher correction levels.

Allan G.

 

[STP]

No alky on that log..Previously, the tune had alky supplementing it, but I took the alky out of the equation when I saw a problem. The car should run 17-18psi on 17* of timing without the alky, so I turned the alky off to help isolate the problem.

 

[STP]

My guess is that there is a fuel pressure issue. Looking at the log, I would think that you are almost out of injector. Looks like the DC% stabilizizes at 85+ percent. It appears to have a lot of correction when ramping into boost. Coincidently the knock retard is happening near the higher correction levels.

Allan G.

The car does come up fast.. I was surprised to see any knock whatsoever with the tune being so conservative. Thought for sure raising the MAPvsAE would take care of the correction but it made no difference whatsoever.

 

[turbobitt]

The car does come up fast.. I was surprised to see any knock whatsoever with the tune being so conservative. Thought for sure raising the MAPvsAE would take care of the correction but it made no difference whatsoever.

Looking at your tune, the map Vs. AE threshold in the Map AE parameters menu is 110 KPA so won't affect that area anyway. Looks like a mechanical issue to me. like the fuel pressure is not keeping up with the boost.

Allan G.

 

[STP]

Hrm...I'm not sure how to fix that then if the pump and injector sustains it after the hit.

 

[norbs]

Without logging fuel psi your guessing, I would say the FP regualtor is leaking internally fuel /vacuum. Check FP with vac hose on and off at idle

 

[STP]

Alright...So tonight I made a couple pulls on the car. Ran the fuel psi gauge out to where I could watch it and cranked the fuel pressure up to 45psi base with line on. Also turned the boost down to 14....No difference in the inj dc spike whatsoever. Fuel pressure is constant and rises with boost. I had in the neighborhood of 65psi according to the gauge. Next pull I unplugged the knock sensor just to see if something in the program was adding fuel once knock was detected whether it be real knock or false. Again, no change in the inj dc spike. What confuses me is why only in first gear, on the hit, does it get knock, pull timing, and spike the inj dc. Then it levels out...I considered possibly tire spin was causing false knock, but the quick pull without the knock sensor ruled that out. I'm at a loss....Should I try raising the MAP AE parameter limit from 110 to say 220 and run the MAPvsAE table up?

A little more info on the package...

109 stroker
Champion irons
206/206 billet roller
Limit 45A turbo
Tial 44mm gate
60# inj
single intank Aeromotive pump
stock lines
adj Accufab regulator
2004r w/ nl PTC converter

 

[STP]

Norbs, the regulator appears to be functioning properly....I get fuel psi drop once i reconnect vac to it. Also appear to be getting adequate fuel psi rise per lb of boost.

 

[norbs]

Norbs, the regulator appears to be functioning properly....I get fuel psi drop once i reconnect vac to it. Also appear to be getting adequate fuel psi rise per lb of boost.

Ok, that is good to know at least. What is the exact make and part number of the injectors

 

[turbobitt]

In your cal file, you have 65# injectors in the fuel calc parameters.

I'm guessing your just out of injector but I'm surprised you get the spike at 14# boost since your log in the aboce post has injector DC in the 73% range.
Edit - also spends a lot of time over 80% when it levels out. Still think its out of injector.
Allan G.

 

[norbs]

Some of the 65's are rated at 58 psi that is why I asked for more detail

 

[STP]

Some of the 65's are rated at 58 psi that is why I asked for more detail

I did not know that Norbs...Will check on that. I figured the car to be on the edge with the current size inj and single intank when leaned on...But not at 17/18psi?? In all the datalogs I have looked at over the years, I've never seen a inj dc spike like this and then level out. On the second pull last night, I backed the boost down to 14psi and still got a 83% spike in duty cycle although the spike wasn't quite as prominent...It leveled out in the 70% range. I may try turning the alky back on and run the initial setting way up in the box and see if that helps the spike. Trying not to beat on the car too much till I figure out whats up...Thx for the suggestions guys.

Edit...107961 is the number on the injector, Norbs. A quick search shows them as Mototron 60's..Which 60's are you referring that are actually 58's?

 

[turbobitt]

Edit...107961 is the number on the injector, Norbs. A quick search shows them as Mototron 60's..Which 60's are you referring that are actually 58's?

Why do you have 65 lb/hr in your fuel calc parameters ?

Allan G.

 

[Chuck Leeper]

Send me the injs, and we'll remove any ? as to how they work, and the flow rate......

 

[STP]

I caught that too Allan...changed it last night.

Chuck, I've already considered sending them to you. Let you know.

 

[turbobitt]

I caught that too Allan...changed it last night.

Chuck, I've already considered sending them to you. Let you know.

OK, Was getting confused if they were 65's and your were calling them 60's or whatever. MAy not make much difference in the fuel calcs but would be better to have it match as close as possible.

Allan G.