RootesRacer
Donation Time
Joe you listening on this?
I had an unique opportunity this last week to wittiness a dyno test on a brand new absolutely stock LS2 (6 liter GM V8).
The purpose of the test was so that the owner could see first hand, the power options of the engine (owner is a GM aftermarket parts sales person).
The engine is destined to go in a boat.
Testing was performed at Superior Automotive in Anaheim Ca, in their state of the art engine dyno facility.
The setup for the test was as follows:
1) The LS2 engine was bolted into the engine dyno.
2) All 3 test runs were done back to back (or as quickly as the intake and fuel components could be swapped).
3) Ignition was controlled by the same source in each of the 3 tests (was distributorless ignition from one of my ECUs).
4) The carburettor setup was pre-tuned by the shop putting the test together and was 850CFM demon carbs 4150 4bbl clone. The intake was a GM LS2 aftermarket intake with injector bungs welded in each runner.
6) Injection setup 1 was a 4150 4 bbl sized air door running on the GM aftermarket intake.
7) Injection setup 2 was an individual runner intake with 8 X 12 inch runners, each with 2 inch throttles (called stack injection).
8) Ignition timing for each setup was optimized based on successive dyno pulls until the group agreed max power and torque were achieved.
9) Fuel was adjusted on each setup until the wideband O2 sensor pairs read what the engine builder desired.
Test #1 fuel injected central air door on the GM afterarket intake.
Engine produced 493 HP at about 6300 RPM. 480 ft/lbs of peak torque.
Test #2 carburetted 850CFM demon 4150 clone on the GM afterarket intake.
Engine produced 502 HP at 6400 RPM, 475 ft/lbs of peak torque.
Test #3 fuel injected 8 throttle stack injection.
Engine produced 515 HP at 6400 RPM, 490 ft/lbs of peak torque.
The carburettor used is one of the best flowing 4 bbl carbs available, it was jetted and tuned on previous days on the engine dyno (at great expense).
The first injection setup didn't perform as well as the carb in my opinion because the welded on bungs were not optimal and the fuel spray was wetting the intake walls before it got to the intake valves. I think that in cases where you dont get optimal atomization (due to large droplets of wetted fallout), you have to give the engine even more fuel to compensate for what it cant burn. This extra fuel displaces air, and you cant make as much power as a result.
The first injection setup did however have more torque than the carbed setup, my guess here is the difference is the lack of venturi restriction that the carb had.
The second injection setup blew both the first inj setup and the carb.
The reason in my opinion is that the injectors on this setup were higher up the intake stacks and and the fuel had (like the carb) more time to atomize in the intake air stream. The second injection also had its fuel parameters set to a leaner fuel curve since it was more efficient at using the fuel given it.
So thats about it, this is the first time Ive heard of a back to back comparison of this nature on the same engine (on the same evening).
We would have tested the stock LS2 EFI intake as well, but we ran out of time (we all went home at 1:30 AM).
As a side note, while we were waiting for the intakes to be changed, we were tuning and testing a 2 liter Mitsubishi eclipse that put down 450 HP to the wheels.
I had an unique opportunity this last week to wittiness a dyno test on a brand new absolutely stock LS2 (6 liter GM V8).
The purpose of the test was so that the owner could see first hand, the power options of the engine (owner is a GM aftermarket parts sales person).
The engine is destined to go in a boat.
Testing was performed at Superior Automotive in Anaheim Ca, in their state of the art engine dyno facility.
The setup for the test was as follows:
1) The LS2 engine was bolted into the engine dyno.
2) All 3 test runs were done back to back (or as quickly as the intake and fuel components could be swapped).
3) Ignition was controlled by the same source in each of the 3 tests (was distributorless ignition from one of my ECUs).
4) The carburettor setup was pre-tuned by the shop putting the test together and was 850CFM demon carbs 4150 4bbl clone. The intake was a GM LS2 aftermarket intake with injector bungs welded in each runner.
6) Injection setup 1 was a 4150 4 bbl sized air door running on the GM aftermarket intake.
7) Injection setup 2 was an individual runner intake with 8 X 12 inch runners, each with 2 inch throttles (called stack injection).
8) Ignition timing for each setup was optimized based on successive dyno pulls until the group agreed max power and torque were achieved.
9) Fuel was adjusted on each setup until the wideband O2 sensor pairs read what the engine builder desired.
Test #1 fuel injected central air door on the GM afterarket intake.
Engine produced 493 HP at about 6300 RPM. 480 ft/lbs of peak torque.
Test #2 carburetted 850CFM demon 4150 clone on the GM afterarket intake.
Engine produced 502 HP at 6400 RPM, 475 ft/lbs of peak torque.
Test #3 fuel injected 8 throttle stack injection.
Engine produced 515 HP at 6400 RPM, 490 ft/lbs of peak torque.
The carburettor used is one of the best flowing 4 bbl carbs available, it was jetted and tuned on previous days on the engine dyno (at great expense).
The first injection setup didn't perform as well as the carb in my opinion because the welded on bungs were not optimal and the fuel spray was wetting the intake walls before it got to the intake valves. I think that in cases where you dont get optimal atomization (due to large droplets of wetted fallout), you have to give the engine even more fuel to compensate for what it cant burn. This extra fuel displaces air, and you cant make as much power as a result.
The first injection setup did however have more torque than the carbed setup, my guess here is the difference is the lack of venturi restriction that the carb had.
The second injection setup blew both the first inj setup and the carb.
The reason in my opinion is that the injectors on this setup were higher up the intake stacks and and the fuel had (like the carb) more time to atomize in the intake air stream. The second injection also had its fuel parameters set to a leaner fuel curve since it was more efficient at using the fuel given it.
So thats about it, this is the first time Ive heard of a back to back comparison of this nature on the same engine (on the same evening).
We would have tested the stock LS2 EFI intake as well, but we ran out of time (we all went home at 1:30 AM).
As a side note, while we were waiting for the intakes to be changed, we were tuning and testing a 2 liter Mitsubishi eclipse that put down 450 HP to the wheels.