Air Fuel a NA motor

[PKFIRE]

Can you get an accurate airfuel reading just free reving a carborated v8 with a wideband? I've always had to tune the air/fuel under load with a boosted car.

[Mista Bone]

Nope, has to be loaded...

You might barely get into the main fuel circuits just free revving.

Harley riders think they can tune jets just by free revving though....

[redfirepearlgt]

Nope, has to be loaded...

You might barely get into the main fuel circuits just free revving.

Harley riders think they can tune jets just by free revving though....

So that's what they're doing. I just thought they were trying to hear themselves. LOL!

[mustang8998]

I've known guys who would make a pass and stop on the return road, then pull plugs to read them. The claim was, that the return to the pits could possibly lead to false readings.

[IWRBB]

I've known guys who would make a pass and stop on the return road, then pull plugs to read them. The claim was, that the return to the pits could possibly lead to false readings.

Just the coasting/idling at the end of the run will affect them. I've read you have to pretty much turn the ignition off as soon as you lift from WOT to get correct plug readings. Of course, that's people with a tune that's already close, trying to get it perfect under load. If the engine is massively rich or lean, the plugs will show it.

[Mista Bone]

Also looking at the heat stripe on the ground electrode, and the carbon on the threads.

http://i107.photobucket.com/albums/m307/bonespec/Honda/D16Z6/N2O%20tuneup/85shot2.jpg

[timdsellers]

Hard to read the plugs relative to your over all tune since idling can cause load up which fouls the plugs or even too lean and burnt plugs. Just dont idle to long before reading them. But even then lots of guys let their car idle while tuning and overall messing around which affects how the plugs look. So your WOT tune could be great but idle and mid range tune may be fouling your plugs.

[PKFIRE]

He has a pulling truck with a 515 Chevy big block turning 9000 plus rpm. I told him he probably needs a load on the motor to get a true reading. When he brought it to the engine dyno he was running 15.1:1 on a fuel that 13.5:1 was stoich. I was said that was a no-no and he needed to monitor that. I don't want him to grenade this motor since he has a lot of time and money invested in it. The motor should make 1000hp NA but he has it in a pulling truck and I have no idea where he would test and tune the thing. I still can't believe they only usually get one pass during an event. I'll stick to drag racing.

[timdsellers]

Yep, he needs a wideband and maybe some data logging(if he wants to get fancy!)while under a load of course.

[Mista Bone]

15:1 on a dyno is bad news.

Race gas I assume? I know a lot of pullers run alky...