Premium gas, or?

[Pbrown]

Originally Posted by Emerald025

will it hurt if my idiot husband filled mine up with regular unleaded gas? I'm pissed!

LMFAO. Wouldn't recommend it over time but at least it wasn't diesel. Then you'd have real problems. As for punishment, should send him out to buy your feminine products this month.

[humfrz]

hmmmm.......I always thought that the engine "ping" sound was caused by the piston skirt slapping up against the cylinder wall.

An engine "knock" sound was usually caused by the piston rod (bearing) slapping on the crankshaft rod journal.

But hey, I'm not a mechanic .... anymore ....... ever since they took away the carburetors and distributors .....

Anyway, @Emerald025, just tell your husband that a fine piece of jewlery just might take your mind off the situation .....

humfrz

[Tromatic]

Originally Posted by ae86stunt

Whats it caused by?

Main bearing and journal bearings becoming loose, Duo to detonation.

I am a mechanic. But dont take my advise.

Since you are incorrect about knock, not taking your advice seems like a good idea.

"What is engine knock? Its when Internal parts, (Rods, Crank Shaft) SLAP the side of the Engine housing."

Con-rods "slapping" the case due to low-octane gas. Good one.

[Allch Chcar]

Originally Posted by Sleeperz

Mazda Sky engine 13:1 runs 87 octane.


He calls the 14:1 CR "groundbreaking," though it's a lesser 13:1 in U.S. engines to accommodate our 87-octane regular gas. A "breakthrough" combination of technologies – including direct multi-hole injection, dual VVT, new-design pistons, a unique 4-2-1 exhaust system, shorter combustion duration and delayed ignition during start-up – prevents knock.

What is groundbreaking is how the engine has a typical output with peak torque at 4k RPMs and peak power at a modest 6k RPMs. Most engines that use that high of compression either require high octane and/or extremely high cam profiles. The Prius engines use 13:1 static compression ratio but they make far less than 100BHP per liter. The drawback is that the early '12-'13 MZ3 Skyactiv without the 4-2-1 header does take a hit below 4k RPMs. The CX-5 has the Skyactiv headers while the '12-'13 MZ3 uses traditional headers.



Too much compression can actually hurt power and torque as pre-ignition becomes an issue. Economy engines will typically run pig rich at high RPM/load anyway, to protect the engine. But it's not uncommon for a regular tuned engine to run better on midgrade or even Premium. What with VVT and VCT being commonplace.

Originally Posted by ae86stunt

Whats it caused by?

Main bearing and journal bearings becoming loose, Duo to detonation.

I am a mechanic. But dont take my advise.

So you're actually a technician?

They are probably talking about the specific sound. Pinging sounds a bit different from rod knock. Hammering vs popcorn popping. Pinging can cause bearings to wear out but you typically don't get rod knock until after pinging or detonation.

Originally Posted by bestwheelbase

Detonation can be a cause (not the only one). But the cars are designed to not have catastrophic failure due to one street driven tank of 87, right?

91 AKI is recommended but 91 AKI is required. So no, a tank of sub-Premium could result in long term damage or possibly void the warranty in the event of catastrophic failure. All it would take is sending out a sample of the fuel to confirm.


Note that 100 RON(94-95 AKI) is more commonly available overseas than it is here. Whereas we have places like Cali and the thirteen states that follow CARB where 91 AKI is the only Premium available.

[Tromatic]

Originally Posted by ae86stunt

Thats fine dude. Its funny tho... I have been a certified mechanic for a decade.
I hate to say this but. People like you are making my FRS Payment, Mortgage, Supporting my family...
Thanks.

This thread is about octane and knock. Are you really going to tell us again about your "expertise" in the same sentence you tell us that octane related "knock" is the con-rod's and crankshaft bashing the block? I know any number of people who are "certified". Odd how that is no guarantee of competence.

[SloS14]

Originally Posted by humfrz

hmmmm.......I always thought that the engine "ping" sound was caused by the piston skirt slapping up against the cylinder wall.

An engine "knock" sound was usually caused by the piston rod (bearing) slapping on the crankshaft rod journal.

[Tromatic]

Originally Posted by ae86stunt

Obviously you did not read my post's thorough enough.

Fiarly sure I did. You are the one who told us knock (AKA "detonation") was con rod's and crankshafts hitting the engine block.

[DeeezNuuuts83]

Originally Posted by Allch Chcar

What is groundbreaking is how the engine has a typical output with peak torque at 4k RPMs and peak power at a modest 6k RPMs. Most engines that use that high of compression either require high octane and/or extremely high cam profiles. The Prius engines use 13:1 static compression ratio but they make far less than 100BHP per liter. The drawback is that the early '12-'13 MZ3 Skyactiv without the 4-2-1 header does take a hit below 4k RPMs. The CX-5 has the Skyactiv headers while the '12-'13 MZ3 uses traditional headers.

I remember reading about that. I assume that the 2014 has the proper Skyactiv headers, correct? I think it had something to do with how the headers wouldn't fit in the engine bay of the previous model, so hopefully Mazda fixed it, though the hp and torque figures are about the same as before, so I'm not sure.

[strat61caster]

Originally Posted by ae86stunt

What is engine knock? Its when Internal parts, (Rods, Crank Shaft) SLAP the side of the Engine housing.

Originally Posted by ae86stunt

It is the Certified truth, from a certified mechanic.

I am now terrified to bring any vehicle to a 'certified' mechanic. You clarified yourself in a later post so no need for an argument. I agree completely with this post: http://www.ft86club.com/forums/showp...&postcount=109

Terminology pisses more people off on car forums than pissing on the car.

[DeeezNuuuts83]

Try to look for the certified master technicians, if I have my terms right.

[Muaddib]

The bare minimum would be 91 AKI. But i did notice that i get better performance with 94 octane. Mileage wise i get better mileage with Shell 91 octane.

[Allch Chcar]

Originally Posted by DeeezNuuuts83

I remember reading about that. I assume that the 2014 has the proper Skyactiv headers, correct? I think it had something to do with how the headers wouldn't fit in the engine bay of the previous model, so hopefully Mazda fixed it, though the hp and torque figures are about the same as before, so I'm not sure.

Yup, and the CX-5 had enough room for the new headers from the get go. Mazda3 had to wait two years for the new chassis. The peak numbers aren't what is important for a DD, it's the low RPM operation that can make or break an otherwise good car. As it affects not just acceleration but throttle response.

Originally Posted by DeeezNuuuts83

Try to look for the certified master technicians, if I have my terms right.

Master tech isn't really that special. The problem is good techs are either underpaid, overworked, or work in crappy conditions with terrible managers. Every mechanic/tech I've talked to drives a POS car and recommends finding another job. They usually have to buy their own tools if they make decent money and management pays them a fraction of the total hourly rate. I've seen dealerships charge $60-$100 for hourly work but the techs might make $12-$15 if they're lucky.

Dealerships hire a lot of newbies from the schools so they're causing it if anything.

[DeeezNuuuts83]

Is there anything above master tech?

[Allch Chcar]

Originally Posted by DeeezNuuuts83

Is there anything above master tech?

No, not really.