Need help understanding scan data - ZR-1 Net Registry Forums

QB93Z · 07-18-2009

The last time I was at the drag strip I thought my 1993 ZR-1's performance was lower than usual. I had slower ET's and lower top speed.

A scan I ran during one pass showed 1 instance of knock spark retard which I have seen before.

But the scan also showed Injector Duty Cycle of way over 100%.

Thinking that I may have a fuel supply problem, I changed the fuel filter and tested the fuel pumps using the FSM. Both fuel pumps appear to be working properly. I get 49 psi, steady at WOT.

I recorded another scan yesterday after the fuel filter change. Here is a portion of the scan during a hard acceleration to 100 mph:

Am I right in my understanding that INJ DC being high means the computer is making the injector pulse width longer in order to get enough fuel to the cylinder?

Any ideas on where to look next?

Jim

07-18-2009	#1
QB93Z Join Date: May 2007 Location: Westminster, Maryland Posts: 3,689	Need help understanding scan data The last time I was at the drag strip I thought my 1993 ZR-1's performance was lower than usual. I had slower ET's and lower top speed. A scan I ran during one pass showed 1 instance of knock spark retard which I have seen before. But the scan also showed Injector Duty Cycle of way over 100%. Thinking that I may have a fuel supply problem, I changed the fuel filter and tested the fuel pumps using the FSM. Both fuel pumps appear to be working properly. I get 49 psi, steady at WOT. I recorded another scan yesterday after the fuel filter change. Here is a portion of the scan during a hard acceleration to 100 mph: Am I right in my understanding that INJ DC being high means the computer is making the injector pulse width longer in order to get enough fuel to the cylinder? Any ideas on where to look next? Jim __________________ If it isn't fun, you aren't doing it right! 1990 Black ZR-1 - sold 1993 Quasar Blue ZR-1 1994 Competition Yellow ZR-1 1995 Dark Purple ZR-1 Maryland State Coordinator WAZOO Member