Hi guys,
my mec and I have been trying to solve my FC's problem for over 2 weeks now, but with no good results; today's dyno run confirmed previous reading from a borrowed wideband: I'm running lean big time.
First, my setup:
'87 NA car with '88 TII swap (ECU, AFM, Pressure Sensor still NA, previous owner run with them very good for 7 yrs before rebuilding the engine: after rebuilding, problem started)
MSD 125 fuel pump (still new, used only for 700 miles, the miles the engine ran after the rebuild)
Removed all exhaust restrictions, 2.5" pipe with 2.5" Y in the back
K&N Air filter
running 12psi max boost, dyno run was done at 10 max

What we did so far:
checked voltage at fuel pump: getting 12.5 at idle, when acelerating it goes up to 13.2-13.4
cleaned and checked all 550 stock injectors, they flow perfectly
checked fuel pressure: idle 38-40, with car running it goes up to around 54; chocking the line after the gauge, the pressure will go up to 80
checked TPS, 1 V
checked AFM
checked error codes (none)
checked post 4k signal to secondary injectors: they are getting it
tried with another ECU
tried with another fuel pump (stock one)

None of this solved the problem.
We are really running short of ideas down here; this monday we'll check every fuel line, hoping to find something cloged. What else should we check? Any ideas guys? Also this monday we'll try with 760cc secondary injectors (thx HAILERS for the infos about jumping the resistors pack), but the mec's telling me that the way I'm running lean, they won't make all that much of a difference (I'm running lean even before 4k).

Damn, if someone tells me I have to wax the car to solve this problem I'll do it! Today we were like "Ok.... now what?".....

Somebody suggested me getting an aftermarket FPR; I have read good things about the Aeromotive one (like $150), but can I use it with stock fuel lines?

ANY idea/input is more than welcomed....

 

how lean is lean?

 

VERY lean.... the mec tell's me I should run 12-12.5... the lowest I manage to go is 14.....

 

Uhm... Am I reading that correctly? Please tell me I'm not... You're hitting 17 A/F ratios?! That's way way way too lean. And your max power was 121.8? Something is wrong here, you should be making way more power than that, especially at 10/12 psi of boost. Maybe it's because you're running so lean. I'm surprised your motor hasn't blown yet at those A/F ratios.

 

you need to get something to control your fuel like a apexi afmII fuel controller. This will allow you to adjust your fuel levels to above stock levels. I think stock boost on a s4 is only 6psi so if your hitting 12 you need to richen it up.

 

Yep, those readings are acurate.... checked with 2 different widebands; the car isn't getting hard driven, always below 3-4k; I got only 121hp beacuse I'm running lean and it wasn't revved up (max hp is supposed to be around 6,500); dyno guys stopped the run as soon as they saw that 17 reading....

 

Ah yes, I just realized your revs only went to mid 4000's, ok then that's good.

 

The Non turbo ECU is what would be scareing me... first things first, you need to correct that and get a Turbo AFM.

Either that or go stand alone.

The Non turbo ECU can't relate to boost. Even a N338 ECU from a vert and a Turbo pressure sensor would be better than running a regular non turbo ECU in there.

 

We tried with a turbo (318) AFM, same thing.
I know in Puerto Rico they use the NA ECU for drag races (10 and 9 secs cars) and previous owner ran very well with them for over 7 years; I know it'd be better with TII ECU/Boost Sensor/AFM, but even with the NA it should not run *so* much lean.....

 

No no, you didn;t understand my post... using a N318 AFM will lean out a N326/N327 ECU even further. If anything you need to use a N33X ECU with a N318 AFM and pressure sensor.

See the N32X ECUs run way rich from about 5K RPM and up. The fact that you are going even leaner there suggests that you have way too much boost for the ECU to even keep up with (even with it running way rich up high). Niormally I wouldn't even try 7 lbs of boost on a N32X ECU, and you are running 10+

I am sure that the non Turbo (N32X) ECUs work fine with boost up to a point, but you have exceeded that point with your modifications.

You need to think about a stand alone ECU rather than make the stock factory crap work with that much boost.

 

This is not much help, but on both my turboii's I have a SAFC, stock 550's, and removed fuel over 4000 to the tune of 20 percent plus to get the afr's UP to the mid 11 to 12afr range FROM the middle 10's afr. My car is on the whole stock except for the 21/2 inch downpipe, presilencers and the DynoMax.

I'm saying....I think it's peculiar for you to be running lean when I have to remove 20percent..oh, stock fuel pump here and 13.5 plus volts at the pump.

I've no solution for you. Try another AFM?????? I'd be curious what the output voltage from the afm to the ECU is when your wide open throttle. Maybe I could compare your finding with one of my cars? Oh, I've deliberatly put a non turbo afm on one of my cars at sometime and the afr's were not much different. I would get me a turboii ECU and boost sensor though.

OR...if you had a digital meter that showed pulse width and duty cycle ...it'd be interesting to see what duty cycle the injectors have at full throttle.

 

Looks like Atkinsrotary s/c kit can be used with an N/A ECU and AFM but increasing the Fuel pressure with an aftermarket FPR is a must. They also say that for running higher than 5-6 psi of boost, the injectors have to be upgraded to 720cc. So I would imagine you need both those things at the very least for your set-up. Some sort of AFC would be necessary I would imagine to get some reliability.

 

Thx guys for all the suggestions.

Icemark: I'll try to get ECU/Pressure Sensor/FCD borrowed and see what happen

HAILERS: how do I check the AFM Vdc output? it's a 7 pin conector if I'm not wrong; also, where do I measure the duty cycle of the injectors? At the plug located near the resistor packs?

rxseven: which aftermarket FPR can I use without needing to modify my fuel lines? I'm kinda lost between -6 and -10 line fittings..

So guys, do you think it's more an electronic related problem rather than some clogged line?
thx a lot for the inputs! I'm building up my check list for this coming monday!

 

To measure duty cycle you need a digital meter that has that function. A normal/regular meter won't do. I saw one at RadioShack a few months ago for 50/60 bucks. You put that type meter on DutyCycle and put the neg probe on a good ground and put the positive lead of the meter in the back of the wire at the ECU, with the connector on the ECU. Then start and drive the car while monitoring the meter.

The AFM has an output wire to the ECU. It's pin 2E, a green wire with a blue stripe. With the key to ON and engine not running, the output will be approx 4volts. As you shove/move the flap in the AFM to the open position the voltage will drop...I forget what the voltage is when it is full open. Less than a volt I believe.

In spite of what I read on this site....I find it hard to believe your running lean because of low fuel pressure...when I have to remove twenty percent just to get to the 11/12's afr. Two seperate widebands show this on two seperate cars.

 

To measure duty cycle you need a digital meter that has that function. A normal/regular meter won't do. I saw one at RadioShack a few months ago for 50/60 bucks. You put that type meter on DutyCycle and put the neg probe on a good ground and put the positive lead of the meter in the back of the wire at the ECU, with the connector on the ECU. Then start and drive the car while monitoring the meter.

The AFM has an output wire to the ECU. It's pin 2E, a green wire with a blue stripe. With the key to ON and engine not running, the output will be approx 4volts. As you shove/move the flap in the AFM to the open position the voltage will drop...I forget what the voltage is when it is full open. Less than a volt I believe.

In spite of what I read on this site....I find it hard to believe your running lean because of low fuel pressure...when I have to remove twenty percent just to get to the 11/12's afr. Two seperate widebands show this on two seperate cars.

 

we had the same problem in the cosmo/s5 t2 car, turns out plugging in the fpr solenoid fixed it. now @12psi it has a rich stumble in the midrange....

 

***hecked fuel pressure: idle 38-40, with car running it goes up to around 54; chocking the line after the
gauge, the pressure will go up to 80*******

That got my curiosity up. When did it go to fifty four???? While boosting around 10psi????? That is the only time I ever see my fuel pressure go up close to fifty. You don't mean reving in the driveway and seeing fifty??Do you?

The fpr should be seeing the vacuum/pressue in the intake 99.9 percent of the time. The only time it should be vented to ambient is when starting the car, which results in a higher fuel rail pressure. Once started the rail pressue should go down to approx 28psi (I admit I've never seen lower than approx 31/32 psi at idle).

Under full boost I'll see close to fifty psi in the rails. I put a fuel gauge on my wipers and drive like that to see the gauge. You should do the same to see what your pressure is during boost.

 

Is it possible you have the fpr hose going to the wrong solenoid????/ How about running that hose directly to the intake manifold....as in teeing it off the boost line.....or if you have a series four, connect it to the very, very bottom nipple on the back of the throttle body. That is the only source of vacuum on the back of the throttle body. the other nipples are ambient.

 

good suggestion!

 

A good suggestion inspired from a post from above...someone named 9fc3 or was it j3sfd9 or??? I forget.

 

i dunno either

 

domyalex, the stock fuel lines will be adequate. The stock FPR will maintain a constant pressure differential, about 45-50 psi except at idle, where it's more than that. So if your pump is rated at 90-100 psi, your 54 psi reading is correct and is too rich under vacuum at low rpms as can be seen on the chart around 3700-3800 rpm. You can't raise the fuel pressure beyond that point with the stock FPR so how will the N/A ECU add more fuel under boost? I think that beyond a certain rpm value, the N/A ECU ignores the AFM input anyway. That is the case with the GSL-SE EFI (3000 rpm) so I would imagine it would apply to 2nd gens also. Without boost map in the ECU and the turbo pressure sensor, your only option is to raise the fuel pressure even higher and trick it into adding more fuel.
On my car, the FPR is set such that the fuel pressure is 50-54 psi at 10psi boost. But I am running 720 cc x 4 and my sds scanner tells me I am a little over 70% duty cycle just to give you an idea.

 

What's your timing set like? I ran 12psi on the n/a ecu/afm/pressure sensor all the time, with the s-afc providing no correction and I don't have any troubles at all. I *NEVER* get close to lean. There's something more wrong here than just that.

 

NO THEY DON'T!!

Nobody in PR uses a stock computer on 10 & 9 seconds cars, now carbs is a whole different story

 

My timing is dead on, checked that one too.

HAILERS: the 52-54 psi o fuel pressure were seeing while driving and with the fuel pressure gauge attached to the windscreen and driving under boost.
What ECU are you running and how many psi?

Previously, the FPR wsa connected to a bad vaccum line, now it's connected (wit a "T") to the same line with the BOV and the Boost pressure Gauge and the Pressure Sensor. The car improved a little bit, but not that much....

J9FD3S: could you please tell me how did you guys fixed the problem with the cosmo/T2?

SonicRat: what kind of injectors are you running?