Clowd

So, after putting the 3bar FPR in, the car will run more towards rich during hard accell, but when cruising or idling, the gauge will jump around like crazy, but stays mostly in the lean area. Am I going to **** on my headgasket running the car like this? What do I replace/adjust to make the car have a normal consistant A/F ratio?

Yabo

Since it's bouncing around at idle, but stabilizes somewhat at hard accel, it sounds like vacuum to me...

SamGrant951

What other mods does your car have? Are you running a chipset designed for a 3-bar FPR? Are you determining this off your narrowband A/F gauge? If so mine was telling me I was rich and I was actually lean, but would dither around at idle and at cruising then goto rich when on throttle. They are kinda worthless imho and you should get a wideband or head to the dyno for a A/F plot vs. rpm to get the real story...

Clowd

mods are 3" exhaust from the turbo back, lindsey boost enhancer, "cup car" chips whatever those are, and that's about it.. before the 3bar FPR, it would jump around at all times, idling or acellerating, it would jump around no matter what.

edit: oh, yes, it's narrowband(autometer something or other)

Charlotte944

If the engine is in fact running lean, then you have too much air and not enough fuel.

Start off by verifying that you do not have ANY vacuum leaks. Check ALL vacuum lines (This includes the climate control stuff as well.), inter-cooler connections/hoses, J-Boot and associated fittings, intake manifold gaskets, injector seals, dip stick tube seal, dip stick O-Ring, oil filler cap and O-Ring, oil filler to engine block O-Rings, and the throttle body to intake manifold O-Ring.

If all of that checks out, then I would start looking at the the chips you are running. At this point I would suspect that the chips may be asking the DME to dump more fuel than the injectors can deliver.

Clowd

Would I be doing more harm than good by seeing what putting the stock chips back does? I'd rather try the chip route before checking all the vacuum stuff..

Danno

Whatever you do, DO NOT put the stock chips in. The TurboCup chips are mapped for 15psi with the stock 2.5-bar FPR, the stock chips will handle no more than 12psi. Changing the chip to compensate for vacuum leaks is a bad idea. By far the most important part is the vacuum line going to the FPR. So important that on the '88+ TurboS, they provided a separate banjo-bolt and vacuum line just for the FPR alone so that it's not shared and T'd with any other device. Any one of those vacuum lines coming off the banjo-bolt at the intake-manifold can cause a leak, or many times the T has a crack in the middle, or the fuel-dampener or compressor-bypass valve or heater valve has a leak. This will end up reducing vacuum and boost going to the FPR and you end up with inaccurate fueling. Too much fuel and bad gas-mileage under around-town cruising and too little fuel under boost. Programming a chip to compensate for this is NOT the way to fix it.

Measure vacuum at all the devices using vacuum to verify that you don't have a leak. Get a rubber T and a short section of hard vacuum-line and vacuum-gauge. Remove the rubber hose going into the FPR, insert your T, vacuum-gauge and re-install the vacuum hose into the T. Make sure the car's warmed up and measure vacuum at the following devices:

- FPR
- fuel-dampener
- compressor-bypass valve
- heater-valve

What vacuum values do you get at idle?

Then, let's verify that we have the correct calibration of your AFR gauge. Under partial-throttle operation, like cruising around and less than 50% throttle acceleration, the AFR gauge SHOULD be dithering back and forth between 12.0:1 and 18.0:1. This is the auto-correction based upon feedback from the O2-sensor to arrive at the ideal 14.7:1 stoich. mixture for best emissions and fuel-economy. BUT... examine the end-ranges of this dithering motion, they HAVE to be evenly centered on both sides of 14.7:1. If however, it's centered over a leaner spot than 14.7:1, such as sweeping back & forth between 13.0:0 <--> 19.0:1, then we've got a ground problem that's throwing off the gauge; the fuel-mixtures may be perfectly OK.

That's because the AFR gauge uses a reference voltage coming from the battery's +positive terminal and that difference vs. ground is the comparison used with the O2-sensor's output. If you've got bad grounds or a floating ground, the readings from the O2-sensor will read too low and appear to be too lean to the gauge. The not-centered-on-14.7:1 test is a clue to this ground issue. So.. test the grounds:

1. disconnect both the KLR and DME boxes
2. hook up the voltmeter's -negative probe to the battery's negative terminal
3. measure resistance (ohms) at the following harness pins with the +positive probe on the voltmeter:
- DME#5 = ?? ohms
- DME#16 =
- DME#17 =
- DME#19 =
- DME#28 =
- KLR#10 =
- KLR#11 =
- KLR#14 =
- KLR#10 =

All of these should read 0.0-0.1 ohms. If you've got more than 0.25 ohms, time to clean the grounds on the block and/or replace the negative cables.

Now... if we can confirm that vacuum is OK, the grounds are OK and that the gauge is sweeping evenly on both sides of 14.7:1, then we can assume that the data is valid and usable. At idle and partial-throttle, it will always be dithering, so that's fine. The newer EFI systems are 10x faster and the sweep-rate is so fast it looks like a blur and the range of motion is also much tighter, maybe 1-2 LEDs max. Anyway, the only time the gauge will be steady is when you're accelerating briskly at 75-100% throttle. Depending upon the values programmed into the chips and whether it matches your actual air-flow, the reading may be OK or not. Best to take three full-throttle runs and use only the reading from the last one. That's because the O2-sensor is heat-sensitive and its output will change with temperature, the 3rd run will be a consistent temperature that you can replicate time after time.

So that 3rd run should read between 11.0-12.0:1 under full-throttle. The stock chips tends to get richer and richer in the stock system and stock boost, going from 12.0:1 in the mid-range to 11.0:1 by redline. This is most likely due to the dropping boost-curve, 11-12psi in the mid-range down to 8psi by redline. The TurboCup chips are also mapped for a dropping boost-curve of about 15psi in the mid-range to 12psi by redline. Ideally, you'd want to have you.r car fully sealed with no vacuum leaks so the FPR gets full boost for pressure-rise and you want to see an air-fuel ratio that's flat from 4500 to redline no leaner than 12.0:1. Theoretical power is at 12.4:1, but it's so minor, that it's better to target a 11.0-12.0:1 range for safety. As you can see, the precision of the LED-base air-fuel gauges leaves a lot to be desired... It can only point out huge problems, but not good for tuning.

Geo

I hate to tell you this, but narrow band AF gauges are basically worthless. They are notoriously inaccurate. Before you do anything you may want to go to a dyno with a Horriba or similar high quality wide band AF gauge and find out what is really going on.

A friend was helping a friend of his tune his turbo car on a dyno and the narrow band AF gauge said the ratio was fine. When they hooked up the Horriba they found the engine was running so lean it was a wonder it hadn't blown the engine!

Charlotte944

Yeah, what Danno said.