murlo26

iTrader: (9)

I was going to say i am 500 bucks richer! Had to try

Bugermass

Have you tried it yet?

tephra

iTrader: (6)

if someone has some spare dyno time it would be good to see

especially if they have an EGT probe

crispeed

The sad part is many believe if there is not any knock then no damage is being done from running lean afr's. You're correct about these threads popping up ever so often.
I know of a certain tuner that's running 12.8 afr's at 14-17psi and he swares that no damage is being done because there's no knock on his logs. Poor guy learned the hard way that burnt valves and butted piston rings are not from knock!

tephra

iTrader: (6)

forgetting about fuel quality for a second:

if your not knocking and your EGT is reasonable then yes you can run that lean...

before saying any more I would like to see some facts about EGT's at various AFR's - as per Bryan I like DATA hehe

crispeed

Ever seen a knock sensor capture pre-ignition?
Egt's are not only effected by afr's. Ignition timing and load just to name a few have a greater affect on egt's than afr's. Every application is different so egt data will differ a lot. The fuel you're using also effect egt's. You can't really compare egt's from another application. Not even going to get into the differences in the measurement devices and their position in the exhaust system use to capture egt's.

tephra

iTrader: (6)

yeah but i'm pretty sure a piston doesn't care what fuel type your running, just what the temp is

tephra

iTrader: (6)

and yes - the knock sensor could pick up a pre-ignition event, I am not sure if Mitsu have coded our's to do so (ie window from before spark)...

crispeed

Actually it does because it's not only the piston you gotta worry about. The piston-to-wall clearances and rings are adjusted for the level of power output. The fuel you're using also have a great affect on those build specs. Once piston sealing is compromised then everything goes downhill form there. Oil contamination does wonders for breaking down fuel. It's also greatly effects the egt's and afr's your're recording. Tuning two strokes is just one example where you cannot rely on afr and knock recording equipment. Egt's play a more important role there.

crispeed

If that was the case Mitsubishi would be the only manufacturer that would not ever have to offer warranty for their motors.

tephra

iTrader: (6)

pre-ignition and knock isn't the only thing that kills engines

and detection is different to prevention

tephra

iTrader: (6)

anways, back on topic...

I think we can all agree that this thread basically revolves around running 11:1 vs 12.5:1

richer = safer?
leaner = cleaner + more power but at what cost?

is it realistic to run 12.5:1 AFR's on a daily driver using pump??

forgetting about fuel quality and mixture perfection, what about EGT's? Is there anything else we need to consider?

this is for pump fuel (91 or 93oct) and based on the Evo engine (4g63 or 4b11) for those that want to argue about AFR's on other engines/fuels...

criptballer

iTrader: (3)

wow what a great read. you two just made me purchase two tuning books from amazon! LOL!

tephra

iTrader: (6)

well when you get the answer let us know hehe

Bugermass

Ask the guys who drive cobalts, hhrs, skys, and ions.. From the factory those engines run in the 13s under boost.

It depends greatly on the material that the pistons are made off and how well the engine components transfer heat to the cylinder walls and head..

Our sales guy has a stock 1JZ swapped SC300 that runs on Q16, his AFRs are at 13.0 at 24PSI of boost and hes been running with no issues.. Our shop race car (900+ HP RSX) runs 13.0 - 13.4 AFRs with no issues.. Now granted the shop car is built, but the 1J is completely stock..

Our old shop race car was 11.5:1 compression motor with 28PSI of boost running 13.0 all the way down the track.. Never had an issue with pistons or valves.


http://www.youtube.com/watch?v=pWsXy6qYmQA RSX

http://www.youtube.com/user/Bugermass#p/u/6/qFuv-DyWjRk Old shop car.