Plx A/f Up And Running

[JD1964]

Here's the initial reading. This is full throttle 3rd gear at about 5000 rpm. Looks like the 19s are leaving me lean. I have the Kirban adj reg so I'm gonna bump pressure 2lbs and check again. I'll update later because I have other obligations that take precedence.

 

[smkshw]

looks good,single right?.....if you get a chance take a pic little farther away?,i want to run a single also....

 

[7991LXnSHO]

Isn't 14.7 what you are looking for as ideal? This looks pretty close.

 

[JD1964]

looks good,single right?.....if you get a chance take a pic little farther away?,i want to run a single also....

Yes, single. I mounted is lower. When you look at the car from the side, you cant even see it. It hides behind the mirror when viewed from the side of the car.

 

[RacEoHolic330]

That's quite lean at WOT. I assume you're naturally aspirated. You should be looking to get into the 13.0 range.

 

[JD1964]

Isn't 14.7 what you are looking for as ideal? This looks pretty close.

I thought mid 12's A/F is the target WOT mixture.

 

[smkshw]

Yes, single. I mounted is lower. When you look at the car from the side, you cant even see it. It hides behind the mirror when viewed from the side of the car.

exactly how my car will look!....awsome thanks...looks great...!

 

[Bullitt347]

12.5:1 is considered ideal N/A WOT. ...........as a rule of thumb. Each engine responds differently and fuel quality comes into play as well. At 12.5:1 A/F you will be safe from a A/F standpoint. The engine may make more power at leaner settings though, but run the risk of problems if the fuel quality changes or an injector decides to not work perfectly. Also depending on your fuel pump, raising the pressure is not going to fix the A/F issue. It is proven that as fuel pressure rises, fuel volume goes down. Just read the spec's on any fuel pump, free flow volume is always higher than the volume at a specified pressure. Example: a 155lph fuel pump flows 155lph at around 40 psi (I think) If the pump has to build 50psi of pressure, the volume of the pump will go down to around 130lph (again a quick guess) . So be careful of thinking a fuel pressure change is going to fix a lean issue. Your 2 psi adjustment is probably not going to make a significant change either way.

 

[7991LXnSHO]

12.5:1 is considered ideal N/A WOT. ...........as a rule of thumb. Each engine responds differently and fuel quality comes into play as well. At 12.5:1 A/F you will be safe from a A/F standpoint.

Thanks for the knowledge! I figured you would shoot for stoichiometric combustion, not safely rich.

 

[madspeed]

14.6 is perfect at idle, should be 12.5 WOT as mentioned

 

[JD1964]

My fuel pressure experiment yields the following.

I first went to 45psi vacuum line off at idle. Reconnect vacuum, test drove and got 13.4 A/F WOT.

Next I went to 50psi vacuum line off at idle. Reconnect vacuum, test drove and got 12.7 A/F WOT.

In both cases, the A/F does not go full rich right away at WOT. It gradually creeps richer. It's most rich (the numbers above) at RPM's above 4500.

I dont know if this is weird or not but in all cases, 39psi, 45psi, 50psi, the idle and cruise A/F remains in the mid 14's.

 

[madspeed]

Idle and cruise rpms are decent. Ive got mine running 14.6 at idle and a bit leaner at 15.2 at part throttle cruise.

12.5 is my WOT, but I am boosted. You could be a bit leaner if still n/a. I'd be looking to be 11.7 or so WOT

 

[madspeed]

I first went to 45psi vacuum line off at idle. Reconnect vacuum, test drove and got 13.4 A/F WOT.

Next I went to 50psi vacuum line off at idle. Reconnect vacuum, test drove and got 12.7 A/F WOT.

In both cases, the A/F go full rich right away at WOT. It gradually creeps richer. It's most rich (the numbers above) at RPM's above 4500.

Not following you saying it goes full rich then creeps richer...

 

[Gearbanger 101]

So....details, parts and cost?

 

[madspeed]

For the PLX??

 

[madspeed]

http://www.amazon.com/gp/aw/d/B008LTPGOM?pc_redir=1396175002&robot_redir=1

$200 bux gets you the touch screen multi gauge, the solenoid module/controller and a Bosch wideband oxygen sensor. It can display several different sensors at once with digital readouts and graphs.

I also have the boost solenoid hooked up and can toggle between then simply by touching the screen. Love mine....

 

[JD1964]

Not following you saying it goes full rich then creeps richer...

Sorry, typo. Meant to say does not go full rich right away at WOT.

I went back and corrected my original statement. Thanks for pointing that out.

 

[JD1964]

So if I have to go 50 psi to get 12.7 A/F at WOT, doesn't this mean my current setup should really have 24lb injectors instead of 19's which I currently have?

 

[madspeed]

List your full setup please

 

[JD1964]

List your full setup please

5spd - 3.73 - K&N element - 70mm Marquis MAF - Explorer 65mm TB & intake - Summit 65mm spacer - mildly ported GT40 heads - TFS valve springs - stock HO cam - Crane 1.7 roller rockers - Kirban reg - 19lb - MSD coil - PLX wideband o2 - Summit UD pulleys - Flex-a-lite AL rad w/Black Magic elec fan - 3G alt - shorty headers - x pipe - Flowmaster American Thunder