At 7psi Lean on one side v8

[iaksa]

My problem is running lean on one side of V8 under
7psi boost, after 5-6 second at 7psi. Car is running
perfectly in vacuum, first sec in the boost (7psi),
both side running rich. After 5-6 sec one side of v8
going from rich to lean.
Let me give you more info about my set up.
I had '93 sc400 with Richwood kit w/ M90 having
215K on it and I moved kit to another sc400 '93
with 105K miles, running little bit rich as stock !!!.
I replace/install: new plugs (colder with .033), new
wires, dis. caps, dis. rotors, left rear O2 sensor,
cleaned 315cc/min injectors, all -6AN fuel lines -
two fuel Y blocks adapters going to/from fuel rails with two
fuel rail dumpers. On return fuel line Vortech Super
FMU without OEM regulator.
Installed: Greddy fuel press in cabin gauge (100psi),
boost press. gauge, air-fuel LED gauge, catch can.
After installation car start instantly, 1200rpm - cold
and drop at 750rpm - warm. Adjust fuel pressure :
idle at 33psi and without vacuum at 46psi (from SC400 Manual).
I set up no limits (fuel press.) on SFMU under boost,
at 7psi is about 80psi.
Even my old car had bad idle, and new one perfect, I
think my old car pull much better. Old one had perfect
combustion, LED Air/Fuel gauge show all in green at 7psi
with stock injectors and stock plugs, without pinging.
I need definitely to put car on dyno to see what is going on.

May be it is time to change rest of tree O2 sensors, or some
other sensors, what do you think ?

Before that, can somebody give me a clue what else I can do.

Thanks, IAksa

 

[spf_lexus]

I am running 7psi right now and have rising rate regulator WITH stock reg. Did you run into any issues running the fuel return regulator as the only one? Just curious because I was in between leaving/removing the stock one. Also, I noticed you upgraded from 289 to 315cc w/o any form of tuning... what was your idle like? Possibly larger inj. on new engine messing with computer? I always hear about bad idle and rich conditions for larger untuned injectors. Also, you may have a leaky injector o-ring or glitchy injector.

 

[iaksa]

I had only one RR FMU on my first car, it was regulator with only static press. that can be adjusted. I changed with Vortech Super FMU with static, vacuum, boost, bleeding, 2 different springs, 4 different rings and plates. Both of them works similar on my first car. I am having problem with second car without stock regulator.

IAksa.

 

[cjsupra90]

First off, LED AFR gauges are worth jake diddley squate anywhere outside of about 14.3 to 15.3 AFR.. Dont relay on those types of gauges or any narrow band type O2 system... Get Wide Band setups on the car. Unless your having a air flow distabution problem on one side of the motor, I would suspect that your seeing inaccurate AFR's due to inaccurate gauges / Narrow Band sensors...

 

[cjsupra90]

The likely hood of one bank going lean an not the other is very unlikely especially from an electronics standpoint....

Does the motor seem to be miss firing any? A lot of people seem to not understand that a miss fire will show as a lean condition on a A/F Gauge. This is because if a cylinder or cylinders miss fire, then there is a lot more unburnt oxygen pushed out into the exhaust. The O2 see's this oxygen and reports back a leaner voltage so the computer increase fuel if it is using any type of O2 feed back monitoring.. The other thing with this is poeple that try to do tuning themselves that dont have the best ideas as to how to tune an engine see this and start adding fuel. This only make the situation worse.. I have seen this a number of time...

 

[cjsupra90]

Oh, one other thing, are you sure that you do have 315cc injectors and do all the number on the injectors match?

 

[Jake Breyck]

jake diddley squate

Its Jack diddley squat. dont start adding my name into it

 

[sideshow]

like the others said

u have done afew majpor mistakes in order to save money

never even change injector flow unless u plan to retune ecu or fit aftermarket

and also never trust led ari fuel meters

too many people out there boost their 1uzs the worng way

for fuk sake save the money and do it properly

rising rate fuel press regs is also a cheats way or adjusting fuel press for when going boost

personally id save 1g and fit an afternarket ecu or atleast a piggy back SAFC

or some air flow meter signal adjuster

half the bloody problems asked on these forums are due to things being done the dodgey way

u have spent moeny on all other crap which i dont need

all u need since u are only running under 10 psi is
turbo or superchagrer setup
aftermarket ecu or even a SAFC with do for low boost
and fuel system to suit which i think std fuel system will do
u changed yr injectors so that should be plenty

people who buy the very cheap air fuel meters buy these cause they are too tight
they know they will never afford to put their car on the dyno so they spend 50 bucks on one of these and they thing these are so good and accurate they are used on the space shuttle

 

[cjsupra90]

Its Jack diddley squat. dont start adding my name into it

Sorry dude, didn't realize that I didn't put Jack........



On a different note....
Back to the problem at hand..
Something else that I thought of, your using all four O2's from my understanding.. Are you running Cats???? If so, are you sure that you have both guages hooked up and reading the first (primary) O2's and not the one thats reading off (lean) hooked up and reading from a secondary O2?... This would cause a false reading also because of the Cat...

 

[stevechumo]

First, the narrow band A/F gauge can't be depending on. You'll need a wideband A/F gauge. The best and cheap wideband gauge is AEM, which is about $250. It shows the actual Stochoimetric ratio.

Second, stock SC400 injector is about 250 cc/min. Stock LS400 injector is about 225 cc/min. 315 cc/min injectors (probably Supra injectors) in place of 250cc/min is too much for the stock ECU to handle. I think you shouldn't go over 20% larger with stock ECU. It's way too out of range. I'm surprised your car can still idle normally with those big injectors.

Third, if you'd like to save the money on a low boost setup at 7 psi, you don't need an adjustable fuel pressure regulator and 315 cc injectors. You'll need a hi-pressure hi-flow fuel pump 255 lph such as the Walbro and a fixed 12:1 FMU and run stock fuel pressure regulator. I know this setup isn't the best, but that's the proper economy way to boost safely. It's proven and working for low boost. Don't ever boost over 8 psi with this setup. I know some of you gents don't like this setup, but we're in economy recession. :biggrin:

Fourth, get the SAFC II ($300) to tune with the 315 cc injectors. 2-3 hours are the most by the pro tuners. Each tuning hour is around $150 max. Other ECU options would be Split Second, Map-ECU, MapPro. They're all in the same class as the SAFC II. If you go this way, make sure your tuner know how to trick the stock ECU not to relearn when the O2 sensors see the engine running rich.

 

[cjsupra90]

Second, stock SC400 injector is about 250 cc/min. Stock LS400 injector is about 225 cc/min. 315 cc/min injectors (probably Supra injectors) in place of 250cc/min is too much for the stock ECU to handle. I think you shouldn't go over 20% larger with stock ECU. It's way too out of range. I'm surprised your car can still idle normally with those big injectors.

Im pretty positive that that is a misconception about the LS and the SC engines having different injectors. Maybe prior to 92 this is true but I know that 92 and up, they have the same 250cc injectors... I've pulled injectors form 3 different LS's (a 92, 93, and 95) and all of them had the same 23250-50020 denso part number as every SC that I have ever had my hands on..

315's are only 26% larger then the stock 250's and I know a few cars that are running them on stock ECU's without any problems.. Remember, the stock ECU idles in closed loop once up to operating temps and will compensate for the somewhat larger injectors over time. First short term fuel trim tries to compensate then if short term keeps pulling fuel for "X" amount of time, Long term kicks in and pulls fuel so short term can try to return to its normal state of being able to add or pull 5% (usually).. The idle problem usually doesn't start to get noticable until closer to 40% or more larger. This is because ECU's often have a minimum pulse width that they will go down to and once you hit that point, the ECU can no longer pull fuel so you progressively get richer and richer as you go bigger and bigger with the injectors...

 

[iaksa]

First off, LED AFR gauges are worth jake diddley squate anywhere outside of about 14.3 to 15.3 AFR.. Dont relay on those types of gauges or any narrow band type O2 system... Get Wide Band setups on the car. Unless your having a air flow distabution problem on one side of the motor, I would suspect that your seeing inaccurate AFR's due to inaccurate gauges / Narrow Band sensors...

cjsupra90:

I agree about LED AFR, I used it on first car, at least show me something under boost. No miss firing at all, also when one side going lean (for 1-2 sec.) engine running on same way like before, when was rich. Probably it is false reading. I check AFR wire connections, there are connected to 2 after cats O2.
Like I wrote I change one of them-left, probably old one is bad, will check/replace old one too. You may be right about Cats too, car was little but rich as stock. I double check all 8 injectors are Supra 315cc p/n:23250-70080



IAksa

 

[cjsupra90]

cjsupra90:

I agree about LED AFR, I used it on first car, at least show me something under boost. No miss firing at all, also when one side going lean (for 1-2 sec.) engine running on same way like before, when was rich. Probably it is false reading. I check AFR wire connections, there are connected to 2 after cats O2.
Like I wrote I change one of them-left, probably old one is bad, will check/replace old one too. You may be right about Cats too, car was little but rich as stock. I double check all 8 injectors are Supra 315cc p/n:23250-70080



IAksa

NO NO NO, they have to be wired to the sensors befor the cats, not after.. The O2'a after the cats are there to make sure that the cats are working. The AFR's after the cats are going to be totally different then whats comming out of the engine if the cats are working correctly.... The whole point to the cat is to burn off any left over hc's (hydocarbons)... AFR's measured after the cats will allways show leaner then what the real AFR's are comming out of the motor.. This is giving that the cats are there and working correctly.....

 

[iaksa]

NO NO NO, they have to be wired to the sensors befor the cats, not after.. The O2'a after the cats are there to make sure that the cats are working. The AFR's after the cats are going to be totally different then whats comming out of the engine if the cats are working correctly.... The whole point to the cat is to burn off any left over hc's (hydocarbons)... AFR's measured after the cats will allways show leaner then what the real AFR's are comming out of the motor.. This is giving that the cats are there and working correctly.....

Ooops, let me double check if I am taking wires from before or after Cats for AFR's, Thank you very much, good point.

 

[iaksa]

First, the narrow band A/F gauge can't be depending on. You'll need a wideband A/F gauge. The best and cheap wideband gauge is AEM, which is about $250. It shows the actual Stochoimetric ratio.

Second, stock SC400 injector is about 250 cc/min. Stock LS400 injector is about 225 cc/min. 315 cc/min injectors (probably Supra injectors) in place of 250cc/min is too much for the stock ECU to handle. I think you shouldn't go over 20% larger with stock ECU. It's way too out of range. I'm surprised your car can still idle normally with those big injectors.

Third, if you'd like to save the money on a low boost setup at 7 psi, you don't need an adjustable fuel pressure regulator and 315 cc injectors. You'll need a hi-pressure hi-flow fuel pump 255 lph such as the Walbro and a fixed 12:1 FMU and run stock fuel pressure regulator. I know this setup isn't the best, but that's the proper economy way to boost safely. It's proven and working for low boost. Don't ever boost over 8 psi with this setup. I know some of you gents don't like this setup, but we're in economy recession. :biggrin:

Fourth, get the SAFC II ($300) to tune with the 315 cc injectors. 2-3 hours are the most by the pro tuners. Each tuning hour is around $150 max. Other ECU options would be Split Second, Map-ECU, MapPro. They're all in the same class as the SAFC II. If you go this way, make sure your tuner know how to trick the stock ECU not to relearn when the O2 sensors see the engine running rich.

Thanks 'stevechumo' for analyzing my problem and giving my advice for different options. Yes, my car, starts cold without problems, and idling like a stock. One of the reason putting 315cc and expensive $360 SuperFMU was plan to go 12psi with piggy back ECU. The biggest problem and reason going slow was my first installation, had problem finding right people, finally I paid a lot of money for terrible job, so I decided to do by myself as much as I can.


Can I keep everything, just limit fuel press, fix O2 sensor and/or Cats, and have less problems when I go to 12psi ?


What should be max fuel press @7psi with 315cc injectors ?


Thanks

 

[iaksa]

NO NO NO, they have to be wired to the sensors befor the cats, not after.. The O2'a after the cats are there to make sure that the cats are working. The AFR's after the cats are going to be totally different then whats comming out of the engine if the cats are working correctly.... The whole point to the cat is to burn off any left over hc's (hydocarbons)... AFR's measured after the cats will allways show leaner then what the real AFR's are comming out of the motor.. This is giving that the cats are there and working correctly.....

I just check, there are wired to main O2 sensors (left-OX2 and right-OX1) @"check conn." or "Data Link Connector 1" - DLC1, so there are not wired on 'O2 Sub Sensors'

IAksa

 

[cjsupra90]

Well that a little better, still could have a problem with bad O2's or even the gauges themselves... Even something as simple and commen as a small ground offset could be the issue... These are 0 to 1 volt sensors and a .2 volt ground offset is more then enough to cause a drasticly false reading especially when already dealing with an in accurate measuring device...

In all honesty, I wouldn't even bother trying to daignose a suspected problem like you think your having without having a wide band setup on it... My seguestion is to drive the car normally for the time being and get a wide band kit, have a couple of O2 sensor bungs welded on the down pipes right after the flanges (pre cat) and use the wide band to check your AFR's... You dont even need two kits or a dual kit, just one and then check one side then swap the sensor to the other side and just plug off the bung that not being used at the time...

Like I side before, its hard to have one side go lean and not the other. The electronics are set up as such that this is highly unlikely to ever happen...

One other thing, have you actually pulled the plugs and looked to see if they show signs of a lean condition???? And have you heard an pinging of knock especially while under boost??? It not, then I even more highly doubt that your leaning out.... My relitively stock N/A motor will ping at WOT (wide open throttle) if the AFR get any leaner then 14.0:1.. You being under boost and truely leaning out to the yellow lights (assuming) should be knocking like crazy....

 

[sideshow]

like cj supra said check yr plugs

best way to test spark plugs is drive it for around 10 minutes
get everything hot do not idle engine for too long a sthis will dirty up plugs and give u false readings

now when u get close to home give it abit of a hiding
not to hard but good enough to get good clean readings on plugs
u want nice half load not idle load
this way u get correct reading on plugs
as u get 100ms from yr driveway give it abit again and as u back off
switch of enigne and roll to a stop outside yr place
this way yr enigne doesnt have time to idle and give u false readings on the plugs
once u turn of eenigne pull out plugs

if they all look the same and a nice browny black colour then its fine

like everyone says

i would not trust a narrow band meter more than i trust a 2 dollar hooker not to swallow

 

[iaksa]

Thanks cj supra and sideshow,
I will do what you are suggesting with wide band kit and test plugs with half load driving without idling, need to wait for better weather, it is snow, and I have 275 summer tires, not good combination.


Thanks again IAksa