tuning questiion

[LGAFF]

Car is pulling 4-5 degrees timing over 4k blms at 128 and o2 at 920-940, thoughts or other things I need to check? False knock?

[LGAFF]

I think it goes to 128 BLM at WOT????

[XfireZ51]

Lee,

You really need to put a scantool on it first of all. Secondly, BLMs lock at 128 when you go into PE mode. The O2 sensor reading at WOT is not accurate. Its rich, which it should be but the resolution of a narrow-band O2 isn't usable for determining AFR at WOT. You need to get a WB O2 like a Zeitronix or Innovate.
Frankly, the most expedient thing to do is get the car on a dyno and let's thrash it there. Everything else is just speculative. We don't know if the part throttle or WOT fueling and timing are causing the issue. And you won't unless its ON THE DYNO.

[XfireZ51]

Lee,

Have you pulled plugs and checked for specks in the porcelain? That would confirm detonation.
You may want to try a colder plug.

[LGAFF]

I pulled a plug today, the strap looked fine, but the base looked pretty white, if our cars like slightly rich, I am guessing I am too lean...

[XfireZ51]

Originally Posted by LGAFF

I pulled a plug today, the strap looked fine, but the base looked pretty white, if our cars like slightly rich, I am guessing I am too lean...

Which plugs are u using? Heat range?

[LGAFF]

NGK BKR5EIX-11

Heat range is a 5/6; gap is .044

[LGAFF]

These plugs have 3K miles on them

[XfireZ51]

Get a set of BKR7. Just buy the standard plug and gap to .035". I use 6s in mine. I can see black specks on the ceramic w your pics, so it's detonating and the straps look like heat range is a bit too hot. One other thing is to do plug cuts. Cut the threaded portion of the plug off and let's see what bottom of ceramic looks like. That tells the story of WOT.

[Hib Halverson]

First, I'd not assume you have a problem with false knock until you conclusively rule-out detonation.

Second, unless you subject your LT5 to frequent engine starts without warm-up, you're using a plug that's too hot for an LT5 and running too hot a plug at WOT, make the engine more prone to detonation. Unless the engine sees a lot of starts without warm-ups, you need to run either an NGK 7, a Denso 22 or, if you're familiar with the old ACDelco numbering system, an AC 1 spark plug. FYI, the original LT5 plug was the FR41LS, but that was changed just before introduction for the 1990 model year to the FR2LS because of concerns about pre-delivery fouling.

Now, false knock...it is true that the LT5 can have problems with that and such problems can be aggravated with the installation of headers, but again, I'd not assume false knock until you determine the engine is not detonating.

It was suggested earlier that you acquire a scan tester which takes data. That's a wise purchase. If you see 5-deg KR near peak torque, in warm or even 75° weather, your coolant temp is in the 190s, and your running 91-oct gas, it's probably legitimate detonation.

One way to gain info on whether or not the engine is detonating is to increase your octane just a bit by adding a little 100-octane unleaded racing gas to get the octane of the fuel to 95-96. If you up the octane a bit and the KR either is significantly less or goes away, you had actual detonation and not false KR.

Do not run straight 100-octane unleaded as that often prevents the engine controls from passing the knock sensor test and when the engine can't do that, it sets a code.

You can find blending charts for 91, 92 and 93 octane at http://www.rockettbrand.com/techsupp...taneblend.html

Good luck!