Not so smooth Idle

[robbz28]

I think the hesitation has something to do with my secondaries. I have them tied open and i bet the computer is not calibrated to run the secondary injectors at all times. Of course when my foot hits the floor they kick in but theres that moment when its a "dry hole" with both runners open but only one injector pumping...of.course over 2k its a non issue because i am guessing the secondaries are engaged by then.

[scottfab]

Originally Posted by robbz28

I think the hesitation has something to do with my secondaries. I have them tied open and i bet the computer is not calibrated to run the secondary injectors at all times. Of course when my foot hits the floor they kick in but theres that moment when its a "dry hole" with both runners open but only one injector pumping...of.course over 2k its a non issue because i am guessing the secondaries are engaged by then.

Yes, I think you're onto it.

[XfireZ51]

Originally Posted by robbz28

I think the hesitation has something to do with my secondaries. I have them tied open and i bet the computer is not calibrated to run the secondary injectors at all times. Of course when my foot hits the floor they kick in but theres that moment when its a "dry hole" with both runners e open but only one injector pumping...of.course over 2k its a non issue because i am guessing the secondaries are engaged by then.

The stock calibration has a .2sec delay for secondary injectors to come on. Probably to give throttle plates time to open. That is changed when secondaries are eliminated.

[robbz28]

.2 seconds huh? Sounds about right...its just over an eyeblink of hesitation...

[Paul Workman]

In my experience, I recall what a difference injectors (Accels) made, far as idle goes. At the same time my plugs were new and my coils were only a couple years old, as were the plug wires.

Back to the injectors: They were NOS at the time I bought the car, and only a couple years old. I didn't realize they were NOS at that time, and the tell-tale resistance readings didn't show up until the eve that Marc was about to dyno tune the thing.

Marc was adding fuel at WOT and the AF mix remained leaner than he wanted. He asked me about the injectors, and I told him they were only a couple years old. He told me they were stock (really news to me at the time!) and recommended 16 Accel replacements.

Once the new injectors were in place, the AF numbers responded immediately to fueling table change inputs, the car ended up with 432 RWHP (stock cams), and the idle was as smooth as a sewing machine (and remains so to this day, two years later!).

All that said, I stand by my position that my scanner was the best $$ I ever spent, far as sorting out over 41 different "goings on" in this, my second C4. And, most importantly, the O2 sensors (which I can tell ya from experience) can also roughen up the idle a little, and the scanner will put a finger on those rascals PDQ. (If you don't have a scanner, take it to AutoZone - or the like - and get a print-out of how everything is working. Being able to see what all is going on is soooooo much better than checking this and checking that, tho I too suspect that plugs, wires, or injectors to be the propblem)

One last thought tho... If you are running sans secondaries, at idle the primary injectors only are running, and the dwell time is "stock". Only after you go to above 1% throttle tip in does the secondary injectors come on, and the dwell time is adjusted to provide proper AFR for two injectors.

P.

[WARP TEN]

Nice to see you have been back on line and hopefully feeling better. I was thinkng about your signature (below) and thought that to commemorate your recent experience you really should add an extra line ahead of the FBI one:

"Personal top end ported & relieved" :-) --Bob

Paul's current sig:
90 #1202
"FBI" top end ported & relieved
Cam timing by "Pete the Greek"
Sans secondaries
Chip & dyno tuning by Haibeck Automotive
SW headers, X-pipe, MF muffs

East Central Region Director

[robbz28]

Originally Posted by Paul Workman

In my experience, I recall what a difference injectors (Accels) made, far as idle goes. At the same time my plugs were new and my coils were only a couple years old, as were the plug wires.

Back to the injectors: They were NOS at the time I bought the car, and only a couple years old. I didn't realize they were NOS at that time, and the tell-tale resistance readings didn't show up until the eve that Marc was about to dyno tune the thing.

Marc was adding fuel at WOT and the AF mix remained leaner than he wanted. He asked me about the injectors, and I told him they were only a couple years old. He told me they were stock (really news to me at the time!) and recommended 16 Accel replacements.

Once the new injectors were in place, the AF numbers responded immediately to fueling table change inputs, the car ended up with 432 RWHP (stock cams), and the idle was as smooth as a sewing machine (and remains so to this day, two years later!).

All that said, I stand by my position that my scanner was the best $$ I ever spent, far as sorting out over 41 different "goings on" in this, my second C4. And, most importantly, the O2 sensors (which I can tell ya from experience) can also roughen up the idle a little, and the scanner will put a finger on those rascals PDQ. (If you don't have a scanner, take it to AutoZone - or the like - and get a print-out of how everything is working. Being able to see what all is going on is soooooo much better than checking this and checking that, tho I too suspect that plugs, wires, or injectors to be the propblem)

One last thought tho... If you are running sans secondaries, at idle the primary injectors only are running, and the dwell time is "stock". Only after you go to above 1% throttle tip in does the secondary injectors come on, and the dwell time is adjusted to provide proper AFR for two injectors.

P.

A scanner is something i would really like...any recommendations? My bro would probably ahare in that expense with me...

[Paul Workman]

Originally Posted by robbz28

A scanner is something i would really like...any recommendations? My bro would probably ahare in that expense with me...

Mine happens to be an AUTOXRAY. Rides nice in the storage box behind the passenger seat. However, a "Netbook" with the proper sofware & connectors might be even better.

The scanner allows for recording data in a stack of registers until an "event" occuures and a button is pushed. Then the previous 10 registers freeze and the next 10 or so are recorded for a post-event comparison/analysys.

This combo of always being there goes a long way toward troubleshooting.

P.

[chriskinzel]

Where would one find 'the proper software and connections' for a net book?

[scottfab]

Originally Posted by chriskinzel

Where would one find 'the proper software and connections' for a net book?

That was a minor typo. I think he meant "notebook" with software based scanner. That's what I have.