Breaking up under boost
Thread Starter
Registered User
Joined: Jan 2025
Posts: 5
Likes: 0
Breaking up under boost 1998 C5 Stock LS1, 2 bar OS SD, 80lb injectors, 525lph pump, Hotwire kit, E85, BR7EF plugs gapped at .23, D585 Truck coils, MSD plug wires 10-11psi max.
Breaking up/misfiring under boost bad. AFR spikes to 20+ when it does this. Almost sounds like antilag and it spools my turbo up fast. Sometimes shoots visible flames aswell and sounds like gunshots. Ive replaced my wires, coils, and plugs. The very first pull on brand new plugs is the only pull that it didnt backfire on. Not sure what the problem is at this point maybe grounds? Starts happening at 6+ psi now, used to happen earlier but the truck coils seem to have delayed it slightly. I can roll into boost slightly fine up to about 5-6 psi before it happens. Any suggestions?
Breaking up/misfiring under boost bad. AFR spikes to 20+ when it does this. Almost sounds like antilag and it spools my turbo up fast. Sometimes shoots visible flames aswell and sounds like gunshots. Ive replaced my wires, coils, and plugs. The very first pull on brand new plugs is the only pull that it didnt backfire on. Not sure what the problem is at this point maybe grounds? Starts happening at 6+ psi now, used to happen earlier but the truck coils seem to have delayed it slightly. I can roll into boost slightly fine up to about 5-6 psi before it happens. Any suggestions?
On The Tree
Joined: Feb 2022
Posts: 196
Likes: 72
From: Grand Rapids, MI
I would be looking into plugs and wires first. MSD doesnt mean they are good. Grounds? Voltage?
What is AFR before it starts spiking? Losing fuel pressure? Genuine injectors and pump? We really need datalogs....
What is AFR before it starts spiking? Losing fuel pressure? Genuine injectors and pump? We really need datalogs....
Agreed with log and tune.
At a glance I'd lean toward plugs and wires, BR7EF's might be too cold for what you're doing right now, I run those up to 14-15 lbs. on pump gas currently gapped at .022 iirc, E85 may need more heat at lower boost.
Maybe one step hotter plug and genuine GM plug wires, I've had issues with MSD plug wires in the past.
At a glance I'd lean toward plugs and wires, BR7EF's might be too cold for what you're doing right now, I run those up to 14-15 lbs. on pump gas currently gapped at .022 iirc, E85 may need more heat at lower boost.
Maybe one step hotter plug and genuine GM plug wires, I've had issues with MSD plug wires in the past.
Trending Topics
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
6 Gifts Neither Your Dad Nor Grad Will Shove Into the 'Trinket Drawer'
Brett Foote
Topdon ONE vs. Artidiag 800 BT2: Which is the Diagnostic Tablet For You?
Pouria Savadkouei
Gas Monkey Built a 6-Wheel Ferrari Testarossa With a Corvette LT4 Engine
Verdad Gallardo
7 Most Reliable High-Performance Engines GM Has Ever Built
Verdad Gallardo
Amazing '71 Camaro Restomod Is Modern Muscle Car Under the Skin
Verdad Gallardo
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Thread Starter
Registered User
Joined: Jan 2025
Posts: 5
Likes: 0
I’ll send a log and tune in a second, it spikes lean to 20+ AFR. Map sensor reading vs boost gauge is pretty spot on
Thread Starter
Registered User
Joined: Jan 2025
Posts: 5
Likes: 0
Agreed with log and tune.
At a glance I'd lean toward plugs and wires, BR7EF's might be too cold for what you're doing right now, I run those up to 14-15 lbs. on pump gas currently gapped at .022 iirc, E85 may need more heat at lower boost.
Maybe one step hotter plug and genuine GM plug wires, I've had issues with MSD plug wires in the past.
At a glance I'd lean toward plugs and wires, BR7EF's might be too cold for what you're doing right now, I run those up to 14-15 lbs. on pump gas currently gapped at .022 iirc, E85 may need more heat at lower boost.
Maybe one step hotter plug and genuine GM plug wires, I've had issues with MSD plug wires in the past.
Haven’t check FP yet, the MSD plugs are 2 days old. Just put them on the car. I just cleaned the coil ground yesterday, had old like heat wrap on it peeling off but was pretty clean. AFR before spiking is in the 12s. Will send log and tune in a second. I think i might’ve fouled my plugs out with the old crappy coils because the car did work when i put brand new plugs in for one single pull then it got progressively worse each time.
TECH Fanatic
Joined: Dec 2019
Posts: 1,129
Likes: 478
Other than consistency between the wires? Making sure that one of them doesn't have extremely high ohms. Even a cheap set should have less than 500 ohms between the terminals. Finding one with 8k ohms is usually an obvious sign of a problem.
TECH Enthusiast
Joined: Aug 2021
Posts: 507
Likes: 190
NASCAR Tech Carl Wegner stated the same "No Grease".
We were at Fontata, A GNW race, four cars with Wegner engines.
I TOLD him to use the grease I brought to the race, A Silicon base for SPW boots.
HINT: The track was wet from a night rain, I could see a mist as the group passed.
The next session was afternoon, the grease was used on all the team cars.
As I saw the LEAD CAR pass the Start/Finish I noticed it was a Wegner team car!
Thus a pole position and the rest of the field (not Wegner's cars) were very slow caused by an engine misfire.
Carl then "thanked me" by stating me as the Mad Scientist team member position,
Lance
We were at Fontata, A GNW race, four cars with Wegner engines.
I TOLD him to use the grease I brought to the race, A Silicon base for SPW boots.
HINT: The track was wet from a night rain, I could see a mist as the group passed.
The next session was afternoon, the grease was used on all the team cars.
As I saw the LEAD CAR pass the Start/Finish I noticed it was a Wegner team car!
Thus a pole position and the rest of the field (not Wegner's cars) were very slow caused by an engine misfire.
Carl then "thanked me" by stating me as the Mad Scientist team member position,
Lance