Tuning Question - ZR-1 Net Registry Forums

jss06c6 · 11-14-2018

Dominic,

Need to talk to another tuner sir.. While working with my '91 on the Dyno today, we discovered that cylinder 7&8 showed temps on the header primaries at about 1200 degrees about 6-8 inches from the head. The other cylinders showed the same issue, but not as far down the header primary. Temp at the head (about one inch from the exhaust port) was about 400-500 F. This indicates that the fuel is still burning while being pushed out of the cylinder. Can we change the injector pulse timing on the LT-5? I need to bring it in sooner so that the fuel is in the combustion chamber long enough to burn completely. I can do this with OBDII.. Can we do this with our ECM? I took fuel out of the top end of the tune and brought the AFR into the sweet spot, 12.8-13.1 across the 2000 to 7000 rpm band. Gained about 15 hp at the wheels from the past last week. We're at 373 rwhp (inertia) and 369 rwhp (loaded 10%) now.

Car is strong and the HP is carrying 367 at 5200 to 369 at 6900 rpm, flat. Very powerful at the higher RPM band! Still climbing at 6900 rpm!

Would be grateful for your thoughts and if we have the ability to start the injectors a bit earlier in the combustion cycle. I'm wasting BTU's in the headers!

Steve

XfireZ51 · 11-14-2018

Steve,

Can u describe further what u mean by changing the injector timing? Is this an issue at lower or higher rpms? Or both? How does it work for LS motors?

BTW, what injectors are u using?

jss06c6 · 11-14-2018

On an LS, we can initiate the injector pulse timing compared to the cam and spark timing, thus we can bring the fuel into the cylinder earlier, to make sure we burn 100% of the fuel.. We can change pulse width as well, which would shorten the fuel spray (fuel volume).

jss06c6 · 11-14-2018

To clarify, pulse width can be lengthened or shortened to deliver the optimal amount of fuel to the cylinder, but we can also initiate the fuel delivery earlier or later in the combustion cycle to maximize the amount of fuel we burn on a combustion cycle...

XfireZ51 · 11-14-2018

Maybe Todd wants to chime in, but the only thing I can think of is the Injector Bias and making sure its correct.
How does the LS cal do this? BTDC.? Cam timing?

XfireZ51 · 11-16-2018

Quote:

Originally Posted by jss06c6

To clarify, pulse width can be lengthened or shortened to deliver the optimal amount of fuel to the cylinder, but we can also initiate the fuel delivery earlier or later in the combustion cycle to maximize the amount of fuel we burn on a combustion cycle...

Steve,

What injectors are u using? And is this strictly at top end or throughout the rpm range?

tpepmeie · 11-14-2018

Injection end angle is not adjustable on the LT5 calibration. At least not by ordinary means. It’s hardcoded in the operating system.

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jss06c6 · 11-15-2018

Thanks Todd.. that's what I needed..

Top Toy · 11-16-2018

Did you optimize ignition timing while on the dyno? Advancing the spark, within limits, should also reduce the unburned fuel.

Sent from my HTC U11 using ZR-1 Net Registry mobile app

jss06c6 · 11-17-2018

Quote:

Originally Posted by Top Toy

Did you optimize ignition timing while on the dyno? Advancing the spark, within limits, should also reduce the unburned fuel.

Sent from my HTC U11 using ZR-1 Net Registry mobile app

Took it to the knock limit..

Sent from my XT1585 using ZR-1 Net Registry mobile app

11-14-2018	#1
jss06c6 Join Date: Aug 2015 Location: Magnolia, Texas Posts: 884	Tuning Question Dominic, Need to talk to another tuner sir.. While working with my '91 on the Dyno today, we discovered that cylinder 7&8 showed temps on the header primaries at about 1200 degrees about 6-8 inches from the head. The other cylinders showed the same issue, but not as far down the header primary. Temp at the head (about one inch from the exhaust port) was about 400-500 F. This indicates that the fuel is still burning while being pushed out of the cylinder. Can we change the injector pulse timing on the LT-5? I need to bring it in sooner so that the fuel is in the combustion chamber long enough to burn completely. I can do this with OBDII.. Can we do this with our ECM? I took fuel out of the top end of the tune and brought the AFR into the sweet spot, 12.8-13.1 across the 2000 to 7000 rpm band. Gained about 15 hp at the wheels from the past last week. We're at 373 rwhp (inertia) and 369 rwhp (loaded 10%) now. Car is strong and the HP is carrying 367 at 5200 to 369 at 6900 rpm, flat. Very powerful at the higher RPM band! Still climbing at 6900 rpm! Would be grateful for your thoughts and if we have the ability to start the injectors a bit earlier in the combustion cycle. I'm wasting BTU's in the headers! Steve

11-14-2018	#2
XfireZ51 Join Date: May 2007 Location: Chicagoland, IL Posts: 9,683	Re: Tuning Question Steve, Can u describe further what u mean by changing the injector timing? Is this an issue at lower or higher rpms? Or both? How does it work for LS motors? BTW, what injectors are u using? Last edited by XfireZ51; 11-14-2018 at 10:32 PM.

11-14-2018	#3
jss06c6 Join Date: Aug 2015 Location: Magnolia, Texas Posts: 884	Re: Tuning Question On an LS, we can initiate the injector pulse timing compared to the cam and spark timing, thus we can bring the fuel into the cylinder earlier, to make sure we burn 100% of the fuel.. We can change pulse width as well, which would shorten the fuel spray (fuel volume).

11-14-2018	#4
jss06c6 Join Date: Aug 2015 Location: Magnolia, Texas Posts: 884	Re: Tuning Question To clarify, pulse width can be lengthened or shortened to deliver the optimal amount of fuel to the cylinder, but we can also initiate the fuel delivery earlier or later in the combustion cycle to maximize the amount of fuel we burn on a combustion cycle...

11-14-2018	#5
XfireZ51 Join Date: May 2007 Location: Chicagoland, IL Posts: 9,683	Re: Tuning Question Maybe Todd wants to chime in, but the only thing I can think of is the Injector Bias and making sure its correct. How does the LS cal do this? BTDC.? Cam timing?

11-14-2018	#7
tpepmeie Join Date: Aug 2005 Location: Fishers, IN Posts: 812	Tuning Question Injection end angle is not adjustable on the LT5 calibration. At least not by ordinary means. It’s hardcoded in the operating system. Sent from my iPhone using ZR-1 Net Registry Last edited by tpepmeie; 11-15-2018 at 06:27 AM.

11-15-2018	#8
jss06c6 Join Date: Aug 2015 Location: Magnolia, Texas Posts: 884	Re: Tuning Question Thanks Todd.. that's what I needed..

11-16-2018	#9
Top Toy Join Date: Jul 2012 Location: Allentown, PA Posts: 308	Re: Tuning Question Did you optimize ignition timing while on the dyno? Advancing the spark, within limits, should also reduce the unburned fuel. Sent from my HTC U11 using ZR-1 Net Registry mobile app __________________ '95 ZR-1, aqua/gray, #167 368 LPE/Haibeck, Web cams, Stainless Works headers, B&B Fusion exhaust, 18" Fikse wheels, Alcon brakes, lowered. 491 SAE RWHP.