Questions on full power mode

[Don in VT]

Hi All,

We have been driving the new to us ZR more now and we thought the car was running just fine in the off power mode. The ZR started OK and idled OK bit was not as smooth as the L98. Today for the first time we switched it to the full power mode and it was like night and day. It started first few spins of the starter the idle was much improved and the smoothness of the motor was much better. I am guessing here but could the improvements be because ot better fuel distribution with both injectors working. Are both injectors the same pounds delivery ? Just for our info, what is the pounds rating of the primary and secondary injectors ?

Anyway it is running great in the power mode.

Regards.

Don and Cherry

[Kb7tif]

http://www.corvetteactioncenter.com/...0/002/article/


Here is some intersting and required reading for your car.

[Don in VT]

Thank you for the reply. I am printing the link as we speak. I don't know what I would do without all the help you and others have giving. It is priceless.

Regards,


Don and Cherry

[Aurora40]

Unless you mat the throttle, the engine operates exactly the same regardless of power key setting. The two sets of injectors are not firing at idle or cruising.

It's strange you would notice a night and day difference in starting or idling based on that?

[Don in VT]

Hi Bob,

I don't have an answer for why it appeared to be better but it did. From what you are saying it would seem better to just keep the key in the power mode and just drive like normal with very little penalty. Where can I get more info on the real world operation of the non power and full power mode?

Any info, links or whatever would be appreciated.

Many thanks for the help so far.

Best Regards,

Don

[Aurora40]

Yes, most of us never turn off the full power mode. There is no reason to, except to artificially limit the power.

The previous link explains it well. But basically, at low throttle, one intake runner and injector per cylinder are functioning. Past a throttle/rpm threshold, the secondary intake runners open and the secondary injectors begin to fire as well, and the car really rips.

Keeping the key off prevents this from happening. Staying out of the throttle also prevents this from happening. So unless someone is borrowing your car, there is no reason to keep the key turned off.

[Aurora40]

http://aurora40.dyndns.org/Hometown/...dTrack1989.pdf

On page 11 there's a technical analysis that explains in magazine talk how things work. It's pretty accurate.

[Paul Workman]

At the GTG at Bowling Green for the 20th anniversary of the ZR-1, there was a bull session at the end where a variety of topics were discussed with GM engineers and marketing ppl and us (of course).

From the mouth of Dave McLellan, the engineer in charge of the ZR-1/LT5 project, (in short) told us the "power key" was no more than a gimmick so the ZR-1 could pass the drive-by noise test requirement for California and other places. The LT5 at WOT would not meet the noise requirements, with the secondaries open. What to do??

How about locking out the secondaries?

GM convinced the test and evaluation ppl that the switch in "normal" position was all anyone in their right mind (Dave's words) would need in normal driving. They sold the concept, with the switch in "NORMAL" it passed with room to spare, and that is how the switch came to be.

Later, officials insisted that the Normal be a default whenever the engine was re-started. So, after 1990 (not sure which MY) the mode goes back to NORMAL until the driver selects FULL, where it is then latched.

If your ECM chip is stock, then I would be at a loss to say why there would be any difference in cranking and idle regardless of the switch position. My thought would be along the lines of flogging that puppy - the LT5 loves it, and you'll be rewarded with much smoother starts, smoother idle, etc. (The stock chip tends to run a bit rich and the LT5 will load up a bit. And, it is common for the LT5 to have a bit more blow-by than engines not having open deck designs. Some oil fouling is to be expected: Again a good blast now and then will do wonders, and as Dave McLellan says, "It (the LT5) will thank you for it!")

P.

[Z51JEFF]

How is it possible that anybody could buy one of these cars........and NOT hit the power key first time out.And 91 was the first year that got the low power default.Simple chip change fixed that.

[John Boothby]

I keep Full Power on all the time. Works great. Last road trip: 26.66 mpg with air on at avg 75mph! Great part is, when you need it you got it!!