Dyno run - need advice

[huntsg]

So I took my 87 GN to the Dyno today. Here is my setup: I have a stock turbo, a 3” TH DP, 2 3/4" Dual Magna flow exhaust with test pipe, Stock intercooler, 3” MAF pipe with K&N cold air intake, stock MAF sensor, 3” up pipe, Red Armstrong XP plus fuel pump with hotwire kit, adjustable fuel pressure regulator, 42.5 lb injectors, SMC non progressive Alky kit, TurboTweak Alky chip v5.6, BstC Boost Controller, and a Scanmaster 2.1. I also have an O2 “port” near the test pipe for the dyno to take its reading. As background, I bought this car 11 months ago and have been struggling a fair bit with knock and most of my addons have been to try and get more fuel to the engine. I started the day with the Alky on and the chip set to add 7% at both WOT and 1st gear and timing was pulled -2.8 degrees in both ½ and ¾ gears. Max boost was 20 psi. Fuel pressure was 42 psi at idle with vac. Hose off. From the very first run my readings were showing that the AF ratio was too lean – approx. 15 at start up. In steps, I ended up adjusting the chip to max fuel at WOT and 1st gear and this brought my starting AF ratio to roughly 12. The car ran fine at low boost and RPM with no bogging down. The problem I could never solve was the AF ration would always go very lean (16-17) as the car’s boost and RPM rose at WOT in 3rd/4th gear. I had to back off on every dyno run due to leaning out. The fuel pressure at WOT and 15-17 lbs of boost was approximately 62 psi. Is there any reason you all know of that would cause my car to lean out so much as i build speed? There seems to be plenty of fuel pressure at the rail and I'm wondering if my injectors are too small? Could the MAF sensor be bad? On my last run I even jacked the fuel pressure way up at idle and still got the same result... Sorry for the long post and thanks for any help.

 

[jasjamz]

dirty injectors, low fuel volume, faulty boost gauge. We need scanmaster info like Airflow, 02s, and voltage at WOT.

 

[huntsg]

Unfortunately, I didn't record that data at WOT.

 

[Chuck Leeper]

My $.02...

I'd wonder about the accuracy of the WB.[Exh leaks?]
Pulling only 2.8* on the shifts, and showing an a/f of 16-17??
If you assign a FWHP of 450,[An estimate on my part], a duty cycle of 85%, a BSFC of .6, you need to be looking at an injector in the 53-55# range.
Jacking the FP to 50psi, the injectors you have are now at 45#. Since you don't mention how much you added to the base FP, this is only a SWAG.
Is the alky working as designed?
And, already mentioned, but worth checking: Gauge accuracy.

 

[Sleeper-6]

Like Chuck said, check for any exhaust leaks before or near the O2 sensor. Any air getting into the exhaust stream will screw the readings all up. Have you tried reading a plug after a run to confirm that it really is that lean?

Also, back the boost down and shut off the alky for now. Try to get a clean WOT run at 14 psi of boost before turning the wick up. With the alky off it just removes a tuning factor and may make thing simpler.

Also I would look into some sort of logging software, either DirectScan or PowerLogger. That way you can sit on the couch after a few pulls and review what was going on, instead of trying to remember everything as it happens.

 

[87GN_70GS]

On my last run I even jacked the fuel pressure way up at idle and still got the same result

What happened to the fuel pressure reading as the boost and rpms increased on this run?

 

[huntsg]

During the run the fuel pressure rose steady from 45 psi to about 62 psi as boost increased to between 15-17 lbs.

 

[huntsg]

I'm pretty sure the alky was working as designed. It was certainly lowering the amount of alcohol in the reservoir and the pump was set on max flow When we increased the FP during the last run to see if it wouldn't go lean we increased it to 60 psi vacuum hose removed. As stated above it still leaned out at 5000 rpm or so.

 

[Sleeper-6]

I'm not saying that the Alky isn't working right, but it appears you have a fueling problem with two fuel sources. Eliminating one (alky system)will help you trouble shoot the problems in the other. You need to have a good pump gas only tune before getting more advanced with additional boost and an alky system.
Also a going lean at 14 psi isn't as bad as going lean at 20 psi.

 

["Reaper"]

I think its the opperator and you should sale me the POS for a $1. It really sound like you just don't have a clue and I need to have it before you tare something up.:biggrin::biggrin:

 

["Reaper"]

LOL :biggrin:

Him and a friend changed the fuel pump and he thinks they may have crossed the vent tube and the return line could this cause a lean problem?

 

[WSLN 6]

There is no way you would ever be out of injector with a stock turbo and 42's, even without alky.

 

[Turbo-Archie]

And stock IC.


More like 350hp, not 450..



..

 

[huntsg]

Update from this weekend. Checked all the fuel lines at the tank and they are connected correctly. Removed the driver's side exhaust header and repaired crack(s). Thanks "Reaper" Took the car back out and tried to get scanmaster readings at WOT and came up with these:

AF 195
BLM 124
O2 765
CC 87

Boost was still 15-17 lbs and chip is still tweaked to provide max fuel at WOT and 1st gear WOT. Timing is still -2.8*. KR readings ranged from 0.0 to 4.3. I can understand the exhaust leak from the header crack causing a bad reading O2 reading on the dyno, but now shouldn't all that fuel at WOT cause some change in run characteristics? Car certainly didn't hesitate or bog down. Still puzzled??

 

["Reaper"]

bump

 

[huntsg]

I thought I would provide an update on this thread in case someone else runs into this issue. Bottom line is that I was going lean at high RPM WOT due to a bad MAF sensor. It was a "new" remanufactured OEM MAF that I had just installed and I guess it never worked right. I was on the dyno at SE Turbo last week and when we put on a known good original MAF the problem went away and the car ran like a champ. I am now running 22 lbs of boost with 0.0 KR. Still tuning it for best performance, but it feels good to have that problem solved. I have already bought an LT1 MAF and have ordered a GEN 2 - will install those as soon as they arrive!

 

[TR87386]

Just curious, what kind of power did it make on the dyno?

 

[BOP4ever]

I thought at WOT the MAF went to saturation and the system was open loop and did not use the maf reading due to being overranged Seems like it reads 255 or something the scan tool at least mine does... I have had some knock issues just like this... still do... wondering if I am having the same issue....

 

[omar escamilla]

o2 readings at wot should be about 780-820

 

[huntsg]

As far as power goes it was pretty interesting what happened. When we were still trying to figure out the lean problem we put in a stock chip. With my 42.5 lb injectors this made the run fuel rich - finally. That was the run I saw the most power before we ran out of time. When I get to a scanner tomorrow I'll post a graph of three of the runs we did. For that run we were at 15-17 lbs of boost and it pulled 320 HP and 438 Ft-lbs of torque. Now that I'm at 22-23 lbs of boost it pulls much harder. For BOP4ever I suggest going to www.vortexbuick-etc.com and read the basics section. I wish I had before this past Monday night. Take a look at the A/F ratio graph and read the explanation in the O2 sensor section. My scan master was telling me what was wrong when I kept getting low O2 readings but I didn't know what to do with it