Surging ls1
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Teching In
Joined: Jun 2015
Posts: 5
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From: Spokane WA
Surging ls1 I have read many posts with interest on this site now I finally need help.
I have a 61 corvette that I just put in a 1998 camaro LS1 motor. Runs great without the alternator. At first we connected the alternator to the computer. It would not charge. We then went with the one wire setup with a resistor. The car charges at idle but surges with any throttle. When I disconect the alternator it runs great. My question is not how long I can run without an alternator but why is it surging and how can I fix the issue.
Thanks
Cal
I have a 61 corvette that I just put in a 1998 camaro LS1 motor. Runs great without the alternator. At first we connected the alternator to the computer. It would not charge. We then went with the one wire setup with a resistor. The car charges at idle but surges with any throttle. When I disconect the alternator it runs great. My question is not how long I can run without an alternator but why is it surging and how can I fix the issue.
Thanks
Cal
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Joined: Aug 2010
Posts: 7,323
Likes: 529
From: Ann Arbor, MI
I can only think of too things that could cause the engine to surge when the alternator is connected - the slight additional load, or the additional voltage.
You might be able to simulate the additional voltage by connecting a 50 Amp battery charger/booster while the engine is running and the alternator is disconnected.
Couple questions:
1. Are you using the stock LS1 injectors?
2. Is this the stock tune for the engine?
3. Do you have a wideband O2 sensor/gauge connected
Assuming you made non-stock mods to the intake and exhaust, the PCM might just need retuning. It could be close to surging the and the slight additional load is reducing the RPM and causing the surge.
You might be able to simulate the additional voltage by connecting a 50 Amp battery charger/booster while the engine is running and the alternator is disconnected.
Couple questions:
1. Are you using the stock LS1 injectors?
2. Is this the stock tune for the engine?
3. Do you have a wideband O2 sensor/gauge connected
Assuming you made non-stock mods to the intake and exhaust, the PCM might just need retuning. It could be close to surging the and the slight additional load is reducing the RPM and causing the surge.
Some things like injector offset are bent by system
voltage (affecting injector actuation time and so on)
and this can be a big deal at lower injector pulse widths.
Especially if you've moved on to injectors that don't
match the stockers in this respect.
High system voltages makes the injector work faster
and deliver more fuel. The injector offset vs volts vs
vacuum table is populated with science-type numbers.
There is also a injector flow vs voltage multiplier that
is all 1.000 in my stock '02 tune, and this could be a
handle for you to tweak system voltage dependent
fueling at the big end (offset table is probably more
appropriate / relevant at the idle end).
Rich mixture is the #1 cause of idle surge.
voltage (affecting injector actuation time and so on)
and this can be a big deal at lower injector pulse widths.
Especially if you've moved on to injectors that don't
match the stockers in this respect.
High system voltages makes the injector work faster
and deliver more fuel. The injector offset vs volts vs
vacuum table is populated with science-type numbers.
There is also a injector flow vs voltage multiplier that
is all 1.000 in my stock '02 tune, and this could be a
handle for you to tweak system voltage dependent
fueling at the big end (offset table is probably more
appropriate / relevant at the idle end).
Rich mixture is the #1 cause of idle surge.
