Lean at high rpm - ZR-1 Net Registry Forums

ALLTHECAMS · 05-04-2019

Dynoed my car today after top end porting. Did 3 pulls and it made 383, 384 and 389 on the last pull. The graphs also dipped between 6k and 7k rpm. Before porting it made 374. Also leans out above 5k rpm so I think it's pulling timing. We checked fuel pressure and at WOT it was 40psi. Are my pumps dying?1557011356540.jpg IMG_20190504_154948035.jpg

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Ccmano · 05-04-2019

Yes, should be ~48-55 psi at WOT... At the risk of stating the obvious this assumes the fuel filter is good.

With the car cold, hook up a pressure gauge then simply turn on the ignition, don’t start the car. You should see 48-55 psi that way too. Another good way to test is to check the amp draw of the pumps. Good pumps draw 4-5 amps each, 8-10 amps when both pumps run. Less and your pumps are going bad. It’s nicely written up by Paul here...at post #7.

http://www.zr1.net/forum/showthread.php?p=136108

H

ALLTHECAMS · 05-04-2019

Ok thanks

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Ccmano · 05-04-2019

Based on the HP your car is modded. Curious what mods your running?
H

ALLTHECAMS · 05-04-2019

Quote:

Originally Posted by Ccmano

Based on the HP your car is modded. Curious what mods your running?
H

OBX headers, Borla Challenge exhaust, top end porting, lightweight flywheel, Haibeck chip.

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Ccmano · 05-04-2019

Almost identical to mine, you should pick up some hp at the top end with the lean condition resolved.
H

Hib Halverson · 05-05-2019

It's a little difficult to diagnose this problem from those phone images.

Did the dyno facility give you print outs of the power and torque as well as the AFR chart? If so, can you scan them and post?

Better yet, did the shop give you the DynoJet run file? If you have the run file, please post it.

The blue and green runs demonstrate what you see when the ECM is commanding a lot of knock retard

In the other image, my comments are based on the assumption that the dotted red line is 12.5:1. If that's correct, the engine is clearly lean.

Given proper calibration and injectors, the problem could be pumps, pump pickups, fuel line restriction, fuel filter or regulator.

Has the fuel filter been changed?
Have you run all of the fuel system tests in the FSM?

ALLTHECAMS · 05-05-2019

Quote:

Originally Posted by Hib Halverson

It's a little difficult to diagnose this problem from those phone images.

Did the dyno facility give you print outs of the power and torque as well as the AFR chart? If so, can you scan them and post?

Better yet, did the shop give you the DynoJet run file? If you have the run file, please post it.

The blue and green runs demonstrate what you see when the ECM is commanding a lot of knock retard

In the other image, my comments are based on the assumption that the dotted red line is 12.5:1. If that's correct, the engine is clearly lean.

Given proper calibration and injectors, the problem could be pumps, pump pickups, fuel line restriction, fuel filter or regulator.

Has the fuel filter been changed?
Have you run all of the fuel system tests in the FSM?

I have the printouts but not the files themselves. I will scan them later tonight. The first thing I do will be change the fuel filter. I do not have a FSM.

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Ccmano · 05-05-2019

The fact remains, 40psi fuel pressure at WOT doesn’t cut it. As noted it could be the fuel filter, the pumps or a restriction. Generally if the pressure regulator gives up the pressure goes to the high end. More testing is needed.
H

ALLTHECAMS · 05-05-2019

Didn't have much time but did some testing tonight. fuel pressure with key on engine off was barely above 10 psi :0. started the car and it was 38-40 at idle. I am going to change the filter because i am embarrassed to say I haven't done that on this car. Just one of those things I never thought of. After that Ill check pressure again.

Here are scans of my dyno sheets:

05-04-2019	#1
ALLTHECAMS Join Date: Jul 2016 Location: Bloomington, MN Posts: 127	Lean at high rpm Dynoed my car today after top end porting. Did 3 pulls and it made 383, 384 and 389 on the last pull. The graphs also dipped between 6k and 7k rpm. Before porting it made 374. Also leans out above 5k rpm so I think it's pulling timing. We checked fuel pressure and at WOT it was 40psi. Are my pumps dying?1557011356540.jpg IMG_20190504_154948035.jpg Sent from my XT1710-02 using Tapatalk __________________ 1991 ZR-1 #520 Arctic White/Gray

05-04-2019	#2
Ccmano Join Date: Jun 2006 Location: Sparks, NV Posts: 2,852	Re: Lean at high rpm Yes, should be ~48-55 psi at WOT... At the risk of stating the obvious this assumes the fuel filter is good. With the car cold, hook up a pressure gauge then simply turn on the ignition, don’t start the car. You should see 48-55 psi that way too. Another good way to test is to check the amp draw of the pumps. Good pumps draw 4-5 amps each, 8-10 amps when both pumps run. Less and your pumps are going bad. It’s nicely written up by Paul here...at post #7. http://www.zr1.net/forum/showthread.php?p=136108 H __________________ 90'ZR-1 #1461 Red/Black Ported Intake, Degreed Cams, OBX Headers & Exhaust, Fidanza FW, Secondary Delete, Custom tune, C6 GS Wheels. Sold 08 C6 Z51 Crystal Red Metallic Sold Vararam Intake, Tune, Sold 05 C6 Z51 Red/Black Sold 90'ZR-1 #1723 Black/Gray Sold but not forgotten 91' Z51 L98 White Vert. My First, you always remember your first. Sold. Last edited by Ccmano; 05-04-2019 at 10:35 PM.

05-04-2019	#3
ALLTHECAMS Join Date: Jul 2016 Location: Bloomington, MN Posts: 127	Re: Lean at high rpm Ok thanks Sent from my XT1710-02 using Tapatalk __________________ 1991 ZR-1 #520 Arctic White/Gray

05-04-2019	#4
Ccmano Join Date: Jun 2006 Location: Sparks, NV Posts: 2,852	Re: Lean at high rpm Based on the HP your car is modded. Curious what mods your running? H __________________ 90'ZR-1 #1461 Red/Black Ported Intake, Degreed Cams, OBX Headers & Exhaust, Fidanza FW, Secondary Delete, Custom tune, C6 GS Wheels. Sold 08 C6 Z51 Crystal Red Metallic Sold Vararam Intake, Tune, Sold 05 C6 Z51 Red/Black Sold 90'ZR-1 #1723 Black/Gray Sold but not forgotten 91' Z51 L98 White Vert. My First, you always remember your first. Sold.

05-04-2019	#6
Ccmano Join Date: Jun 2006 Location: Sparks, NV Posts: 2,852	Re: Lean at high rpm Almost identical to mine, you should pick up some hp at the top end with the lean condition resolved. H __________________ 90'ZR-1 #1461 Red/Black Ported Intake, Degreed Cams, OBX Headers & Exhaust, Fidanza FW, Secondary Delete, Custom tune, C6 GS Wheels. Sold 08 C6 Z51 Crystal Red Metallic Sold Vararam Intake, Tune, Sold 05 C6 Z51 Red/Black Sold 90'ZR-1 #1723 Black/Gray Sold but not forgotten 91' Z51 L98 White Vert. My First, you always remember your first. Sold.

05-05-2019	#7
Hib Halverson Join Date: Jun 2005 Location: CenCoast California Posts: 899	Re: Lean at high rpm It's a little difficult to diagnose this problem from those phone images. Did the dyno facility give you print outs of the power and torque as well as the AFR chart? If so, can you scan them and post? Better yet, did the shop give you the DynoJet run file? If you have the run file, please post it. The blue and green runs demonstrate what you see when the ECM is commanding a lot of knock retard In the other image, my comments are based on the assumption that the dotted red line is 12.5:1. If that's correct, the engine is clearly lean. Given proper calibration and injectors, the problem could be pumps, pump pickups, fuel line restriction, fuel filter or regulator. Has the fuel filter been changed? Have you run all of the fuel system tests in the FSM? __________________ Hib Halverson Technical Writer former owner 95 VIN 0140 current owner 19 VIN 1878

05-05-2019	#9
Ccmano Join Date: Jun 2006 Location: Sparks, NV Posts: 2,852	Re: Lean at high rpm The fact remains, 40psi fuel pressure at WOT doesn’t cut it. As noted it could be the fuel filter, the pumps or a restriction. Generally if the pressure regulator gives up the pressure goes to the high end. More testing is needed. H __________________ 90'ZR-1 #1461 Red/Black Ported Intake, Degreed Cams, OBX Headers & Exhaust, Fidanza FW, Secondary Delete, Custom tune, C6 GS Wheels. Sold 08 C6 Z51 Crystal Red Metallic Sold Vararam Intake, Tune, Sold 05 C6 Z51 Red/Black Sold 90'ZR-1 #1723 Black/Gray Sold but not forgotten 91' Z51 L98 White Vert. My First, you always remember your first. Sold.