is it possible to run this lean?

[3.0 GT]

currently, rebuilt 7mgte, turbo back 3 inch exhaust, lex afm, 550cc injectors, intake and 205lph fuel pump and 57trim ct26. when im in boost my zeitronix is showing 20ish afr in BOOST! is this correct? it seems to studder a little bit while boosting but it doesnt seem like my engine would be alive still. i have been boosting up all the time and just got the wideband and i see my afrs are soaring. im boosting 15psi btw. here is the log and tell me if this is correct? my bro has a walbro 255lph pump i am going to try and ill replace to fuel filter too. could my fpr be shitting on me?

 

[IJ.]

If it's missing it's going to show it as a lean condition.

Looks a bit like it's blowing the spark out what's the gap?

 

[3.0 GT]

If it's missing it's going to show it as a lean condition.

Looks a bit like it's blowing the spark out what's the gap?

unfortuantly the gay dual tip platinum ones, i was planning on replacing the wires and plugs but the missing would make it read lean?

 

[IJ.]

Yep.

My 7M had trouble running at cruise after 15:1 and will miss so there's no way the 20:1 on boost is accurate without it burning a piston.

 

[3.0 GT]

ok, i love you. but yeah i was thinking how in the hell is this possible and thought my wideband was poop but it works all the other times. ill try the plug wires(origional toyota 20 yr olds) and some plugs tomorrow. should i go with the autolite coppers and .030 gap? and another question regarding the wideband. i have it hooked up to show the vf and when i first drive the car the vf sits at 0v but if i turn it off then turn it right back on the vf shows 2.2 volts??? and while the car is showing 0v vf's the idle afr is at like 18 and it misses(could be plug/wire related) and when i trun it off then back on so it shows the vf at 2.2v the idle afrs are in the 13's with a steadier idle? wtf

 

[IJ.]

NGK Copper's and start around 26 thou.

sorry don't speak "vf"

 

[3.0 GT]

haha thanks!

 

[TurboStreetCar]

Wideband sensors read oxygen content to gauge air fuel ratio. When a cylinder doesn't fire it exhales a nice breath of unused oxygen witch is observed by the sensor as a lean condition.

VF will usually (in my experience) remain at zero when first started as it operated in open loop for cold start. Open loop appears as (in my experience) 0 volts both on cold start and at WOT, both because theres no correction factor. It runs the engine of pre programmed values. These values are effected by closed loop operation witch is why when using a piggyback you need to do your best to not begin tuning untill the TCCS has switched to open loop operation.

VF is not an indicator of Air fuel ratio, it shows the fuel trim. VF should be ~2.5 volts as thats neutral fuel trim. Fuel trim is based off of feedback from the 02 sensor.

IIRC If VF is above ~2.5 it is adding fuel above that of the pre programed value to richen the mixture, If VF is below ~2.5 it is pulling fuel to lean the mixture.

 

[IJ.]

Dan speaks "VF"

 

[mkIIIman089]

My 7M had trouble running at cruise after 15:1 and will miss

Interesting, been running smooth as butter 16.4:1 closed loop on stock ECU for years now. No power at all (relative to 14.7:1) but smooth as silk...

 

[IJ.]

Interesting, been running smooth as butter 16.4:1 closed loop on stock ECU for years now. No power at all (relative to 14.7:1) but smooth as silk...

Always had a lean miss with mine if I went much under 15:1, might have been Cam timing though, used to run 22:1 on LPG before it did the same.

edit

 

[mkIIIman089]

Very ninja... no idea what it used to be. LOL

 

[TurboStreetCar]

Dan speaks "VF"

Haha, I had the same setup on my zeitronix when I was tuning with the maft gen 2.

 

[IJ.]

Haha, I had the same setup on my zeitronix when I was tuning with the maft gen 2.

Vaginal Flatulance

 

[3.0 GT]

Wideband sensors read oxygen content to gauge air fuel ratio. When a cylinder doesn't fire it exhales a nice breath of unused oxygen witch is observed by the sensor as a lean condition.

VF will usually (in my experience) remain at zero when first started as it operated in open loop for cold start. Open loop appears as (in my experience) 0 volts both on cold start and at WOT, both because theres no correction factor. It runs the engine of pre programmed values. These values are effected by closed loop operation witch is why when using a piggyback you need to do your best to not begin tuning untill the TCCS has switched to open loop operation.

VF is not an indicator of Air fuel ratio, it shows the fuel trim. VF should be ~2.5 volts as thats neutral fuel trim. Fuel trim is based off of feedback from the 02 sensor.

IIRC If VF is above ~2.5 it is adding fuel above that of the pre programed value to richen the mixture, If VF is below ~2.5 it is pulling fuel to lean the mixture.

very good info, my vf is usually sitting at 2.2v which i understand is normal to be slightly different than 2.5v. at idle (after it has been warmed up)the vf shows 2.2 for not adding or subtracting fuel and my idle afr is like 13ish and slowly works its way to 14.7. when im cruising the vf shows the normal range but cruising at 11-12afr. could it be because i recently reset the ecu?

 

[mkIIIman089]

when im cruising the vf shows the normal range but cruising at 11-12afr. could it be because i recently reset the ecu?

Nope.

If it is perfectly steady vf then something is wrong. It will be changing constantly except *maybe* at a perfectly flat, perfectly steady cruise.

 

[TurboStreetCar]

Depends on how long it stays there, The fuel trim is a direct response to the 02 sensor. How long does the A/F stay at 11-12 and VF show 2.2volts? The A/F should not be smooth, it should "bounce" up and down roughly .2-.3 quickly as thats not the proper mixture is attained.

The TCCS will increase fueling untill the 02 sensor switches rich, then it will pull fuel untill the 02 sensor switches lean. This creates the bouncy A/F Plot.

IIRC Each "step" is a certain percentage of trim, Cant remember the number off hand.

You could try checking the 02 sensor as per TSRM: http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?S=FI&P=119

Post up a short steady idle log.

IJ.: :rofl:

 

[3.0 GT]

thanks for the replies, the vf does bounce but only from 2.2v to 2.0v and i dont think that changes what it is determining. and when i go wot or let off the gas it goes to 0. i would post a log but i just pulled the tranny to replace the clutch so when i get it back together ill post up. i couldnt replace my plug wires either because all the local stores are sold out.

 

[CRE]

zy, is your stock O2 sensor plugged in? What you're describing sounds like the TCCS' behavior when it isn't connected. (stays at around 0v, goes up to around 2 when the TCCS adds a bunch more fuel due to some error or odd calculation... does this after warm starts too as a couple MAFT Pro users and myself have noticed and logged).

 

[TurboStreetCar]

thanks for the replies, the vf does bounce but only from 2.2v to 2.0v and i dont think that changes what it is determining. and when i go wot or let off the gas it goes to 0. i would post a log but i just pulled the tranny to replace the clutch so when i get it back together ill post up. i couldnt replace my plug wires either because all the local stores are sold out.

Well the VF might fluctuate a little but more so the Air fuel ratio is what will bounce around .2-3 points normally.

In my experience the VF would go to zero any time the feedback was ignored, such as deceleration fuel cut, open loop operation and things of that nature.

Check the 02 sensor when everything is up and running again as per that link.