fnbrowning

My 2002 CETA: Direct-Flo Airlid SLP Smooth Bellows • Brian Green Ram Air System • Bo White Ported Throttle Body
NGK TR55-IX {Iridium} Plugs • SLP Underdrive Pulley • LS2 Chain
180 Thermostat • TSP Ported Oil Pump • Dynatech SuperMAXX Header System
Comp Cams Custom Grind (220/224 .532/.535 114) • Comp Cams 915 Springs and Pushrods • Custom PCM programming

The car was programmed by a reputable man in St. Louis that does a lot of LSX cars.
When the programming was done, the car was filled with 93 octane premium gas.
Also, gas in St. Louis contains 10% ethanol.

I drove the car to L.A. last week. The best premium could find out west was 91 octane.

Everything was fine, until I left Kingman, AZ

Almost immediately upon leaving Kingman and entering the highway on a grade, the engine began to ping. I could reduce the detonation by varying the throttle, but it was very hard to accelerate to the speed limit without detonation. I thought I got a bad tank of gas, and stopped at the next town, and bought some octane boost. I looked at the NOS brand Octane Booster. Expensive! It contained a main ingredient called Methylcyclopentadienyl manganese tricarbonyl. {Called MMT }There was a NAPA octane boost with the same ingredient that was ˝ the price, so I bought that and put 2 bottles in the tank.

The detonation was somewhat reduced, but not nearly gone. I don’t think octane boosts with MMT are all that effective

On the L.A. freeways the car did great. But they are largely flat, and of course, at sea-level air pressure.

But driving back, the detonation was back also. I could almost eliminate the detonation with 104 brand octane boost, 104 seems to have a better formulation that doesn’t use MMT, and it eliminated everything but a slight ping problem. I still got a slight rattle for short times even on mild hills.

The symptoms showed up most often when the car was cruising in higher gears and going up slight hills, when the cylinder pressures where higher due to engine load. Also when the throttle was changed quickly.

My AutoTap showed intake temp 96 degrees F, water temp 194 degrees, and about 31.5 degrees of total advance, and when the knock sensor heard the rattle, it backed the timing down to ~22 degrees. That didn't totally eliminate the ping. Like, the PCM could not totally deal with the detonation.

My LTFT and STFT were just slightly negative in Utah, and Colorado.


Previously, I’ve filled up on 92 octane gas in St. Louis during the summer, and never had a problem.

My questions: I didn’t think that the total timing was that radical that the car couldn’t run on western 91 octane gas, and I don’t understand why the PCM couldn’t deal with the detonation.

What should I do so I can take my car outside of Missouri on vacation trips?
Do I need to carry an octane boost with me??

Finally, since I had to travel over a thousand miles with some type of occasional detonation, I wonder if I hurt my engine, and how would I be able to tell without disassembling the engine?

PlatnumStatuz

iTrader: (6)

I'd get a wbo2 on it and see if you're not going lean.

Slowhawk

iTrader: (12)

If your car is tuned to max power at high elevation it will ping at sea level. Ussually high DA will take more timing before detanation.

Eurospec2

iTrader: (2)

Also wondering if you might be tuned in speed density?

fnbrowning

The car was tuned in St. Louis, average = 250ft above sea level.
When the programming was done, the car was filled with 93 octane premium gas, and in St. Louis contains gas contains 10% ethanol.

Not programmed in speed density.

fnbrowning

I hear west coast gasoline is not so much the octane, but the oxygenated additives and other additives that make it much more prone to spark knock. Throw in the altitude when I crossed the high desert, and had this significant performance issue.

What about these ideas?

Is there such as programming point called "low octane tables?"
Can someone reduce my low octane tables by an additional amount in the event that I do go to California again?

OR

If am driving on low-octane "premium" gasoline in another state,
What If I reduced my timing down to 22 degrees? That would remove about 10 degrees of timing across the board permanently?.
Then the knock sensors will keep me in a safe range as they are allowed to remove up to 15 degrees of timing.
How much power do you loose going from 32 to 22 degrees timing?

Eurospec2

iTrader: (2)

Im no expert, but in my experience 32 degrees of timing is really pushing the high side to start with.

Losing 10 degrees of timing will be a huge power loss.

There is a low octane table, its possible that your tuner copied your high octane table onto your low octane, that would cause alot of knock if the fuel isnt any good id imagine.

VinceTrifecta

I've seen this time and time again... People move out to Seattle from other places, and end up needing their cars retuned because they have a big problem with detonation.

With LSx motors, around here, we frequently end up *removing* timing to increase power because the factory map causes up to 7 degrees of knock retard at WOT.

Recently, a customer ordered custom programming for their 5.3L V8 truck, and they live at 4500 feet. We had to increase the amount of timing advance by several degrees to get a power increase.

The elevation can have a lot to do with it, but I have also heard the quality of the gasoline on the west coast isn't the same as other parts of the country.

PlatnumStatuz

iTrader: (6)

I agree

Definately worth taking a look at the low octane table and see what the values are.

Hope you didn't do any damage to your engine. Doesn't take much detonation to f stuff up. How's it running now? Might be worth doing a leak down test on it maybe catch a cracked ring land before it completely breaks off and does more damage. Don't wanna be giving you these kinda scenarios but its the reality when the engine goes through that.

fnbrowning

I will have my tuner do that. We were already going to look at the WOT fuel because it was too rich on the last dyno run

The car is running fine. Regarding the engine damage, well, I never drove it pinging continuously. This was more a transitional thing on hills or throttle changes. No full-power with detonation happening.

AND I did supplement the gas with octane boost to reduce the detonation as soon as it was evident something was awry.