Timing retard question

[shadow88]

I went to the track this past friday and the car ran well below it's usual performance level. Previos best of 12.33@120, best Friday night of 14.2@101. Some changes were made so I wasn't expecting anything better than higher 12's.

How much timing can a stock smec pull once it starts to see a high enough knock sensor voltage?

Can the knock sensor pick up valvetrain noise and generate a voltage?

Last question. This one is a weird one. Last years' STATIC fuel pressure setting was 44 psi to acheive mid 11's a/f ratio. This year 34 psi get put the a/f ratios in the 10's Is there a way to calibrate an AEM wideband?

thanks in advance, I'm a little stumped by these issues and it's these issues keeping me from going to sdac this year

[Ondonti]

keeping "some changes were made" vague doesn't really help...Could be a million things to an uninformed reader.

[Juggy]

jaim when i had my fueling issues, (40 psi fuel on 25psi boost...basically 1/2 the fuel i should have had as my static was suppose to be 55psi +1 psi for each boost) the car ran like a bag of crap, so i disconnected the knock sensor and ran 12.0s @ 115 knockin all the way down the track.....if i pluuged the knock sensor in id be lucky to run a 13....

i like to dampen my knock sensors with a little teflon tape. they can sure pick up valvetrain noise...

the AEM sensor has a "free air" calibration. if its reading a steady 10.5 then i may suspect the wideband sensor is on its way out...

[Ondonti]

I went out for a ride in an 800whp 2jz to do some tuning and the AEM wideband sensor obviously was going bad as nothing we changed seemed to work. Ruined my fun that night.

You can always do a hard pull and cut the motor while in load and do a plug read. see if its really as rich as your wideband says. Look for signs of knock too.

[shadow88]

Some changes were made in this case means using a 50hp jet for the nitrous rather than 80hp and I never bumped the base ignition timing past 8* rather than last times 10*. Just to be specific. That's why I wasn't expecting as much out of the car.

The thing shouldn't be knocking due to conservative ignition timng and the use of 109 octane fuel. I'm thinking it's picking up valvetrain noise (there's quite a bit) so I'm wondering how far back it can pull timing.

My wideband at rest with key on engine off is 14.7 and it always has been.

[cordes]

I think the cal can pull 15* of timing out. You can use a scanner to monitor knock voltage to see where you are at and then compare that to the knock threshold table in a stock cal. You can always adjust the cal to match the actual knock values your car is making if you want.

[shadow88]

I just got my scanner back so I'll be out later this evening to see how much if any timing is being pulled. Man, I hope it's just that. Thank you guys, I'll let you know.

[shadow88]

Last night I set the fuel pressure to 44 psi static becuase richer is safer and I went for a hard drive. a/f stayed 10.0 under wot and stumbled badly between shifts and belched out lots of black smoke. Verified. it is too rich.

Set the fuel pressure to 33 psi and the wideband read a leanest reading of 10.9 and no stumble and no black smoke. Also knock retard was pulling 4-6 degrees of timing out. It felt quicker and didn't stumble between shifts. Not quite as fast as it used to feel, but better than belching black smoke.

I'm at a loss for my sudden lack of fuel requirements. The car's running well and I'll get into the spray and race fuel a little later in the week if it doens't rain.

Thank you for your help so far guys.