Magown

Edit: This is sorry for the length, skip to the end for a summery if you don't want to read the whole thing

Ok Gang, ever since I got this car back in September of last year, it’s been plagued with acute rich mixture syndrome. I’ve progressively leaned the mixture a little bit at a time but it’s still way to fat. Here’s a report of what I have done to correct it.

When I first got it, when ever it would come on boost, it would shoot a major black cloud out of the tail pipe. At night it was really obvious, when ever I would leave a stop light @ WOT I could see how bad it was with the help of the head lights of the car behind me. Also it regularly would flame throw on up shifts. Cool eh!

1st correctional step. Replaced fuel rail. Why did I do this? Because for no apparent reason the rail had been modified. It had a nipple installed where the FPR goes and a 914 2.0 FPR installed in the dampener location. The fuel lines were reversed the high pressure line went to nipple on the back of the rail and the return came off the FPR on the front of the rail. <img border="0" alt="[ouch]" title="" src="graemlins/c.gif" /> I have no idea why it was set up like this or who did it. This is how it left the 944 Guru Charlie Andrews shop in Memphis, TN after a $2000 repair bill to convert the car back to stock condition, before I bought it. Obviously he failed miserably.

Results. This helped a lot. It was no longer producing the big back cloud. The exhaust leak that had been making my clothes reek also no longer smelt so bad. Next I realized that the #4 injector was leaking down and fouling the plug whenever it sat for a few days. So I suspected the injectors were tired and spraying incorrectly after 135k miles. I also wondered what chips were being used in the car. I could hit 18 psi no problem. I just knew that they couldn’t be stock. It was in 1999 when the Andrews guy did all the work and I swear we ordered Huntley chips. I was only helping indirectly over the phone so I don’t know what he actually did, if anything.

2nd, 3rd, 4th correctional steps. Injectors, chips, FPR. I installed all these at once but bought them as my car budget would allow. First move was to replace the leaky injectors. I ended up with some 65lb per hour Delphi units. (Why did I go so large for a car w/o a big turbo and MAF/MAP? I will have them in the near future). The next issue was how to make these new injectors work, because they can flow about twice as much as the stockers. After much due diligence I decided to buy some Guru chips, because they have the user selectable injector size feature.

Lastly, my pal Luke had sent me his old 2.5 bar FPR, I assume it was original so I figured it wouldn’t hurt to replace it with a new 3.0 bar unit, which the guru chips were also optimized for. I had one ordered but realized I made better economic sense to include it with my guru chip purchase.

Results. I installed all the goodies. Big surprise. Stock chips. (Thanks Charlie <img border="0" alt="[nono]" title="" src="graemlins/nono.gif" /> ) I forgot to adjust the FQS while I had the DME box open, using the golf tea method I turned it to what I thought was position 2 the 65lb setting. (I do not recommend this method) Hit the key, It fired up and idled really rough and didn’t want to rev. My thoughts were “opps, I accidentally hit position 3 the 75lb setting.” So I stuck the golf tea back in and turned it back 1 click thinking I was now at position 2 the 65lb setting. Hit they key, it fired up, idled at 900 rpm, and revved really nice. Decided to take it for a test drive. First impression much smoother, a little less lag, pulls harder on top. Exhaust leak smells a little better. Overall happy the performance of all the improvements. I still know something is wrong with the car, it’s got major lag, but when it comes on the boost it pulls very nicely. I don’t know what’s been done to it internally. It’s just not right. I decide to break out the g-tech and do a few pulls on my favorite test closed circuit perfectly flat test strip. Test conditions were 66 degrees, 2 passengers, ¼ take of fuel. I made 6 passes.

G-tech results. My best 3 passes were: (0-60, ¼ ET @ trap speed)
1. 6.25, 14.92 @ 100.5
2. 6.13, 14.83 @ 101.8
3. 6.12, 14.77 @ 101.8

The 2nd and 3rd passes were beautiful. Very little tire spin, sweet launches, it just hooked up and went, nice, precise, non abusive & fast ****s. The times seem way slow to me.

The next thing I did was go do my first auto cross. I sucked. Slowest time of the day (not considering a damn Nissan pick up). LOL Everyone was like it’s ok it’s your first time. Bla Bla Bla I was all over the place, missing cones, hitting cones etc. I road along with my pal Joel in his 89 951 and my car just wouldn’t go like his off boost. Something is wrong with this slug it’s not just me.

At that point I wasn’t sure what the hell could be wrong, the only thing I wasn’t sure about everything I have done so far was which setting the FQS was on. I pulled the lid. Surprise. It’s set to Position 1 the 55lb setting. I moved it to position and went for a test drive. Once again rough idle doesn’t’ want to rev, no power off boost, when it comes on the boost hold on cause it feels like it’s going from 50hp to 250hp in 500 rpm. It felt like it pulled harder but I think it was the transition that made it feel harder. I need to use my G-Tech on the g-force setting to see.

Ok last paragraph. I promise. The car runs the best, (still not great) on the 55lb setting. I know the injectors flow 59.4 lbs per hour at 90% duty cycle which means they are 65lb injectors. I know it’s got guru chips. I know it’s got a good 3 bar FPR. I know it’s running rich. It still flame throws every now and then. Lastly, I know it's one slow 951. So what could it be? I’m guessing the AFM flapper box. Thoughts?

fast951

Make sure the engine oil is not diluted with fuel. If you are running very rich, you might be washing the cylinder walls (not a good thing).

Get a A/F gauge, note the RPM & LOAD and A/F R..
Get an adjustable Fuel Pressure Regulator...
Trim the fuel a bit till you get an acceptable mixture.

Of course, always work with your tuner, let him guide you through...

Hope you found the ballast resistors you were looking for...

jimbo1111

18 lbs boost. What are you using for a gauge?
Sounds like the old boost leak syndrome to me but you seem to be holding boost pretty well. 65lbs injectors also seem to large for a stock turbo, you may want to turn the fp down a bit. 3 bar is way to much.

Magown

</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">Originally posted by fast951:
<strong>Make sure the engine oil is not diluted with fuel. If you are running very rich, you might be washing the cylinder walls (not a good thing).</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">John, I'm sure the cylinder walls have been fully washed. <img border="0" alt="[crying]" title="" src="graemlins/crying.gif" /> I'll worry about that next. Don't count me out, I'm still really intersted in your Stage 1 set up. I had to do make this step due to the current economic stat of my wallet.

</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">Originally posted by jimbo1111:
<strong>18 lbs boost. What are you using for a gauge?
Sounds like the old boost leak syndrome to me but you seem to be holding boost pretty well. 65lbs injectors also seem to large for a stock turbo, you may want to turn the fp down a bit. 3 bar is way to much.</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">Jimbo, I've had a Autometer and now have VDO boost gauge. I also have an HKS EVC IV. Yes, the injectors do seem large, but that’s ok. Maybe you are not familiar with the guru chips. They have settings for stock, 55lb, 65lb, & 75lb injectors. That adjusts the duty cycle to compensate.

Here is a quote from the guru website about how the chips are supposed to work with the 55lb setting selected using 55lb injectors.


<strong>"There is no adjustment or intercepting or massasing of the incoming air-flow signal necessary to 'fool' the stock computer into getting proper-idle mixtures with larger injectors. These injectors will deliver exactly the same volume of fuel as stock injectors under identical conditions, just at a lower-duty cycle. So instead of being at 100% around 6000rpm@15psi boost, you'll only be seeing 63% with 55-lb/hr injectors".</strong>

Taking everything into account, it has run rich no matter what I've done to it. I'm going to mess with the AFM next, but I'll try using the 2.5 bar FPR (band-aid solution) to see if that helps it run better.

Magown

I added my mods to my sig

fast951

Stephen,

If the cyl walls are being washed, then you are damaging things, fix it ASAP.

Did you check your TPS? A faulty TPS could send the wrong signal to the DME and cause the wrong fuel map to be accesses.

Check your AFM by reading the output signal. It should be smooth sweep from 0-5v (actually 4.xV)

fast951

One more thing! To make things easier on you, go back to stock chips and stock injectors. If the problem is solved, you know there is nothing wrong with the car (TPS, AFM.. are OK).

The way you have things, you have way too many variables to deal with (Injectors, Fuel Pressure, Chips..)

Start with a good baseline and work from there.

Magown

Yep, checked the TPS. It was not sending the idle signal, replaced it. Have not confirmed with a DVM that it is sending the WOT signal. I'll add that to my punch list. I'm pretty sure it is working.

I'm just saying that I'm willing to bet there is already been some damage. But I'll cross my fingers and hope that it isn't' Last time I checked compression I had 125psi across the board cold, 800 miles ago.

Magown

It ran this way with the stock chips, injectors and 2.5bar FPR.

Mledbetter

Stephen,

I'm on my way out the door, so only a few seconds for this reply.

Make sure that your boost leak isn't at the crossover to wastegate connection. That will absolutely kill performance, sounds like a regular leak, and the turbo can still make 14-16lbs.

Jack up the passenger side of the car and make sure its secure. Get about a 4 foot piece of vac line. Start the car.... Stick one end in your ear (the cool aspect is purely a bonus) and move the other end all around every pipe connection. When you find the leak, you will know it.

-Matt

Magown

Matt, I'm probably going to replace the crossover pipe next week. I'm pretty sure it's leaking from there.

Magown

One thing I would like to add, it runs better with the guru chips and big injectors then it did with the stock stuff. Meaning it was richer before. It was only when I realized that I was running the 55lb injector duty cycle that I confirmed my suspicions that something was wrong.

Mledbetter

</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">Originally posted by Stephen Magown:
<strong>Matt, I'm probably going to replace the crossover pipe next week. I'm pretty sure it's leaking from there.</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">You probably don't need to replace the whole cross-over pipe, unless you are just feeling frisky. If you do, I would suggest sending it off to JetHot. You want to keep as much heat in it as possible.

My guess would be the sealing ring on the cross-over side of the small bend pipe going to the wastegate. Mine just recently failed and the difference was huge until I replaced it.

Good luck...

-Matt

Danno

Measure the voltage output of your AFM to make sure it's up to spec. A couple have recently posted that getting their AFM adjusted really helped with some drivability issues. This can be measured at pin #7 on the DME (green/red-stripe).

1. FULL-SWEEP - with the key to ON but engine not running, have a an assistant slowly open and close the flapper door on the AFM fully. The voltage should be 0.25v when it's fully closed, 4.60v when fully open. Should rise and fall smoothly with no sudden jumps or dropouts.

2. IDLE - at 900rpm you should be seeing 0.79-0.85v.

2. 3rd gear - at 3000rpm steady-state should show about 2.3-2.5v. Gentle 1/4-throttle acceleration from here should show 3.0-3.5v.

Next up, test your temperature sensors:

The engine-temp sensor should test as follows:

32F = 4.4-6.8k ohms
59-86F = 1.4-3.6k ohms
104F = 1.0-1.3k ohms
176F = 250-390 ohms
212F - 160-210 ohms

The engine-temp sensor triggers the DME that you've got a cold engine. At which point, the DME looks at its cold-start enrichment map to figure out how much extra fuel to add. This value is determined by the air-temp sensor. Which should test as follows:

32F = 4.4-68k ohms
59-86F = 1.4-3.6k ohms
104F = 1.0-1.3k ohms

Magown

I couldn't get my assistant to get out of bed, so I tested the AFM sitting in my parking lot.

Key on, engine not running - .25v
Idle 900 rpm - 1.0 - 1.2 v

I'll test the engine temp sensor in a little bit

How do I test the air temp sensor?