Pinging on 87

[Grumpy Bear]

3 hours ago, dvzzz said:

@Grumpy Bear thank you. I found one interesting fact today while trying to troubleshoot.

 I just went for a long drive and logged again. While logs shows few KR events, up to 4 degrees. There was no audible pinging, same tank of fuel, same load, same route. What was different - the outside temperature, it is finally cold in NC, outside temp was ~42. I could not hear a single pinging event, before it was very audible almost all the time. What sensors might be to blame here? I thought maybe active shutters on Tahoe do not open fully but temp gauge does not show overheating ever. Is MAF also a temp sensor?

 

You can try what Jim posted in the video but it is not abnormal to see spark r-e-t-a-r-d events. It can not find the edge with out stepping over it. it is a continuous process. On any given day mine will pull up to 7 degrees of KR. 

[pokismoki]

i would think having a 12:1 CR would dictate common sense of running 91 or higher octane.. the MPG increase is a no brainer IMO

[CamGTP]

The 12:1 isn't that high though. Mazda for example makes a 14:1 compression ratio 2.0 and 2.5 engine (North America is 13:1 I think) that is designed to run on 87 octane. The direct injection is a big reason why they can do that. My dad owned one and it got 42-44mpg in the summer time with a 6 speed manual, running different grades of fuel never made it any worse or better.

 

Heck, even Ford with the newest 5.0 on the market runs 12:1 compression and has 87 listed as the fuel grade. In any application running 91+ would let it work at the best of it's abilities.

[M1ck3y]

I knock on 94 octane. looking forward to seeing what happens with e85; which actually is e85 (at least last time it was checked). Downside is there's only the one independent station that sells it where I am, so it cost's as much 87.

 

The stupid thing is there's a massive refinery that produces ethanol (for fuel) a few hr's away.  

[pokismoki]

2 hours ago, CamGTP said:

The 12:1 isn't that high though. Mazda for example makes a 14:1 compression ratio 2.0 and 2.5 engine (North America is 13:1 I think) that is designed to run on 87 octane. The direct injection is a big reason why they can do that. My dad owned one and it got 42-44mpg in the summer time with a 6 speed manual, running different grades of fuel never made it any worse or better.

 

Heck, even Ford with the newest 5.0 on the market runs 12:1 compression and has 87 listed as the fuel grade. In any application running 91+ would let it work at the best of it's abilities.

we're talking pushrod motor in a 5500lbs truck. i suggest doing a basic MPG recording for a month, run the numbers and you'll find 91 or 92 octane is cheaper per gallon compared to 87 fuel

 

those are impressive numbers for the lighter weight Mazda , but it also would benefit at a higher octane.. I believe Mazda uses a different combustion strategy , is that also using the otto cycle combustion on their motor? 

 

hey Smokey Unic  got 50mpg on the iron duke Fiero back in the 1980's on 87 octane..