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**paxton350** · 09-04-2005, 11:30 AM

whats your fuel pressure at? do you have an adjustable fuel pressure regulator? you need to have at least 35# at the fuel rails if your going to be romping on it id bump the pressure up to about 40 and run rich rather than lean... do you have an air fuel meter in your car?

-chris

**94 formula** · 09-04-2005, 11:36 AM

Originally posted by paxton350

whats your fuel pressure at? do you have an adjustable fuel pressure regulator? you need to have at least 35# at the fuel rails if your going to be romping on it id bump the pressure up to about 40 and run rich rather than lean... do you have an air fuel meter in your car?

-chris

Isn't the lowest pressure for an LT1 supposed to be 41psi? Also if your getting adequate fuel pressure it shouldn't affect your rich\lean because the computer tells the injectors how much to dump in. If the pump wouldn't be getting enough fuel to it then that may cause it to run lean.

**paxton350** · 09-04-2005, 11:47 AM

well me for instance im running a STOCK pump with pcm4less programing, 30# injectors an adjustable fuel pressure regulator and my air fuel flow on my dyno run was 11.4 -12.1ish... and i have a supercharged application... the first place i would start if i was you is getting more fuel to those injectors via a fuel pressure regulator, did the dyno operator tell you what your a/f mix was at idle?

**paxton350** · 09-04-2005, 11:53 AM

holley makes a few, slp makes this one...http://www.slponline.com/view_product.asp?P=25001 thats where i would start but you might want to get some more opinions...

-chris

**Craig 94 TA GT** · 09-04-2005, 12:02 PM

The entire fuel system is relatively new (installed around 3/04) including a new fuel pump, pressure regulator, filter and injectors. They're all OEM. The last time I checked, pressure at key on was around 41, and idle was 5 or so lower. I'll recheck that, though, as I'm not sure my memory is 100% correct. I didn't check the pressure at WOT though.
I'll look into AFPRs, but I always thought a tune eliminates the need for one, especially on a stockish N/A car. The PCM would adjust for the target ratio making the gains from the AFPR eventualy reduce to 0?

But would a lack of fuel or bad tune contribute to the lean A/F ratio and low dyno numbers?

**paxton350** · 09-04-2005, 12:59 PM

maybe they didnt tune your pcm 100%, or left something out?? i would maybe pick up another pcm send it out to them have them tune it and just double check everything esp map/ timing adjustments, get that one plug it in see what it does, because that really sounds like a tuning issue esp if your f/p was at 41 last time you checked.

-chris

**Craig 94 TA GT** · 09-04-2005, 01:15 PM

Thanks for your advice. I gave Bryan an email, trying to figure this out. My main concerns are the heat from the exhaust (lean), and why I lost torque. And dumb me didn't bother to scan it while getting dynoed. Very, very dumb on my part.

**fastTa** · 09-04-2005, 01:41 PM

On the top of the dyno printout they place 2 items: The method of correction if any (SAE in this case), and the smoothing factor. They just happen to be right next to each other and it looks as if they are one item. 5 is the maximum smoothing capability for smoothing the actual power plots. 275 RWHP equates to roughly 331 HP at the crank using approximately the 17% drive train loss for your 4l60E. That is not too shabby at all for a bolt on LT1.

I would be curious to see what the actual voltage range was on the 02 sensors during part throttle. You�re a/f range is lean especially considering dyno�s normally report a richer a/f ratio than you would typically see on the street. Have you checked to see that you do not have any significant leaks past the MAF or at the intake manifold? This would let un-metered air into the cylinder causing a lean condition. Did your O2�s appear to be switching normally after the car was warmed up and went into closed loop? They could have also leaned out your fuel map a little too much with your last tune.

**Injuneer** · 09-04-2005, 01:41 PM

Just to clarify, its not "an SAE smoothing factor of 5". Those are two different items. Its "CF = SAE" and then "Smoothing = 5".

The HP was corrected to SAE standard temp, pressure, humidity using the "SAE" procedures. The presentation of the graph was "smoothed" using the setting in the dyno software of "5". Both of those are normal.

It appears to be running at about 14.7:1 before it goes WOT, so that would indicate the dyno wide-band and the PCM are both OK.

A big problem can be leaks in the exhaust system. If the fast moving exhaust gasses pull in (educt) even a small amount of air through the leak, its going to throw the wide-band readings off. Are you sure there are no leaks? The dyno operators comments regarding the hot condition of the exhaust and other issues would seem to indicate its a true lean condition, but you have to look at what might throw the readings off.

What is the straight red line along the bottom of the A/F graph?

It would be wise to CHECK your fuel pressure - and YES you do want at least 41psi at WOT. There would be no reason for it to be below 40. And you do NOT want to start trying to tune the engine with the fuel pressure.... that is the worst thing you can do, when you have the alternative of correcting it using the software of a mail order tune. Let PCMforless solve the problem... do not start screwing around with the fuel pressure, unless it is too low. Then correct the problem the right way, not with a bandaid.

**Craig 94 TA GT** · 09-04-2005, 02:41 PM

Thanks for your guys' advice, I greatly appreciate it. Thanks for the clarification for the dyno corrections.

Kevin, here's a scan of driving home from the dyno: http://s94938520.onlinehome.us/lean.csv I guess 331 hp isn't bad for bolt-ons, but it's not saying much considering I put down around 310 FWHP with just the catback and CAI and a steady miss. Either my motor doesn't respond well to more mods, or something's wrong. I'm pretty sure that there aren't any leaks past the MAF...unless there's something I missed. I inspected it well before the dyno.

Fred, I'm almost certain there aren't any leaks. I spend half a day making sure the driver's side flange had no leaks since the O2 is after that part. The passenger's side looks to be good too. It leaked horribly when I first installed it, though. I could feel the exhaust coming out with my hand. But I think I got it fixed to where there's no leaks anymore. I'll double check though.

The straight red line, I believe is the target A/F ratio for this guy's dyno? Maybe? It's at 12.5:1, but I'm sure that all sheets had this, so it didn't have anything to do with my reading.

I'll make sure to let PCMforless handle this then. I was kind of scared to mess with an adjustable FPR, and I'll take your guys' advice well. If nothing is wrong though, I must say almost $2000 in parts and tune for the last round of mods for 16 hp and 0 ft-lbs of torque is absolutely ridiculous.

Lastly, one thing I did notice driving home, on my scan, was the battery voltage was around 12.4 to 12.8 for some time. I'm not sure if that's normal.

I'll post the video later, if anyone is interested. I recorded the computer readings, mostly, to see what was going on during the dyno.

**Craig 94 TA GT** · 09-04-2005, 09:52 PM

Here's the videos from the day. I posted the other videos too in case anyone is interested in seeing the A/F ratios or other data for all cars. Each video has 1 run where I captured the dyno screen. Please, if possible, right click and save-as to avoid bandwidth overage if you wish to view more than once.

My T/A: http://s94938520.onlinehome.us/pictu...ig94TADyno.wmv

Steve's Z: http://s94938520.onlinehome.us/pictu...eve93ZDyno.wmv

2000 Z28 A4, 2.73s (Magnaflow cat-back, intake/lid): http://s94938520.onlinehome.us/pictu...e00Z28Dyno.wmv

2002 Z28 A4 , 2.73s (Flowmaster exhaust):
http://s94938520.onlinehome.us/pictu...k02Z28Dyno.wmv

**Z Ya Later** · 09-04-2005, 10:52 PM

Originally posted by Injuneer

What is the straight red line along the bottom of the A/F graph?

According to the guy at the shop, the red line is where the A/F ratio should be. That sound right to you?

Originally posted by Craig 94 TA GT

Here's the videos from the day. I posted the other videos too in case anyone is interested in seeing the A/F ratios or other data for all cars. Each video has 1 run where I captured the dyno screen. Please, if possible, right click and save-as to avoid bandwidth overage if you wish to view more than once.

My T/A: http://s94938520.onlinehome.us/pictu...ig94TADyno.wmv

Steve's Z: http://s94938520.onlinehome.us/pictu...eve93ZDyno.wmv

2000 Z28 A4, 2.73s (Magnaflow cat-back, intake/lid): http://s94938520.onlinehome.us/pictu...e00Z28Dyno.wmv

2002 Z28 A4 , 2.73s (Flowmaster exhaust):
http://s94938520.onlinehome.us/pictu...k02Z28Dyno.wmv

Man, you weren't kidding when you told me about the bass being cut out. Oy! Oh well, she still looks mean at least lol

. Thanks again man for recording it, even if it was disappointing

**Craig 94 TA GT** · 09-05-2005, 04:03 PM

I just checked my fuel pressure and at key on it's 41. When idling, it's 36-38. When I remove the FPR vacuum line, it's around 46-48.
However, when it's shut off, the pressure shoots down fast. It'll go from 41 to 38 in several seconds. About 10 minutes later, it's below 30. And maybe 30 min to 1 hour, it's at 10. I don't think this is normal, right?

I also noticed that smoke is coming from my passenger's side header. It looks like it's either from the #4 or 6 primary or from the flange. It smells like oil, but continues smoking a few minutes after shut down. I hope this is nothing internal

I may have just spilled a few drops of oil when checking the dip stick tube and now it's burning off. It wouldn't make sense anyway for it to smoke at the flange if there are no leaks.

**Craig 94 TA GT** · 09-05-2005, 10:41 PM

OK, scratch my last post. It may be that the fuel pressure gauge hose is leaking. Although there is no visible signs that it is leaking, the rubber seal that mates with the schrader valve is chewed up. We tried it on Steve's Z28, and found that it did the same, showing a drop off of pressure. We'll try to buy a new hose, or a whole new gauge to make sure we're not both having the problem.

I've been also having trouble with the scans reading a bit low battery voltage, and found the following post on cz28.

Scanmaster voltage is what your PCM sees, as voltage runs through the system there is a voltage drop accross all the components, by the time the PCM/fuel pump sees the voltage its no longer 14 volts, yet the alternator will not see this as a big load since the further away the drop is after the alternator/more system it goes through the less sensitive the alternator becomes & won't generate as much current.

I noticed the biggest voltage drop in the system occurs at the fuel pump, as the wiring ages & so does the pump, the pump draws more power & the wiring becomes degraded & the voltage drop accross the system becomes pretty big, the alternator barely sees this & so it doesn't really compensate.

Easy fix is buy the Racetronix Fuel pump wiring kit, just the wiring kit which is a 10 gage wire that comes right off the alternator terminal & goes all the way to the back to a relay, the stock fuel pump connector is now only used to energize the relay & the relay feeds the fuel pump off the 10 gage wire comming off the alternator. I did this & my voltage in scan master went from 12.5 to 14.1 in the morning & once she warms up to 13.6 steady which is where the voltage should be at operating temp. At the battery I'm reading around 13.9 when she warms up, so now I only get like a .3v difference between system voltage (what scanmaster reads) & whats at the battery.

This also fixed my fuel pressure problem at WOT, the pump only saw 12.5 volts at WOT & my fuel pressure after 5k would drop with all my mods pretty hard, after i did the racetronix wiring mod my stock pump stays at 43psi from 1k-7krpm without even blinking cuz the system voltage is high now & alternator is compensating for the draw properly.

Is this possible, because I'm seeing lower voltage and seeing a lean condition? Or would the PCM see that the pump is not "outputting" enough fuel and throw the SES light?

Of course, I'm still

for Bryan's response at PCMforless. Just want to make sure something else, like a lack of fuel, isn't causing the problem.

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dyno results and A/F ratio

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