Back-Story We met Ryan in 2017, and had the opportunity to tune his '99 Camaro December of that year. Before Ryan owned the car, the motor had been blown, and replaced with another LS based motor. Ryan had headers and Exhaust installed on the Camaro at the time, and we were able to line out a fairly stout street tune. We knew the previous owner had either installed a 5.3 or 4.8, but weren't positive which. Both motors look the same externally.
In 2019, Ryan opened his own business, and the Camaro unfortunately needed to be sold for startup capital. While our logo was scraped off of the back glass, the new owner at least agreed to let Ryan know if the car was up for sale. The new owner of Ryan's Camaro was having fun with it, getting a BTR stage 3 truck cam, AEM X-Series Wideband, ~3500 stall converter, and a Nitrous kit installed.
We all eventually move on to new toys, and Ryan was offered the opportunity to buy his car back. Zippy's Lawncare, Ryan's business, was thriving, and Ryan was able to bring the car back home. Having the Camaro back, Ryan was excited to go cruising again with some good friends. Unfortunately, the car didn't seem right. The transmission was no longer making the 2-3 shift, you had to hold the throttle open when coming to a stop, the cam sounds weren't there, and power wasn't consistent.
Ryan came by the shop for a consultation, and we were able to take a closer look at things. Our lifts were both tied up, but we were able to pull the new calibration off of the vehicle, and hook Ryan up with some new MLS exhaust gaskets to replace the extremely torched set that was installed.
Pulling the calibration, we were surprised to see that only 10 items were changed:
- Target idle speed was increased by 200rpm in gear, 100rpm in park - Idle airflow (in order to hit those targets) was increased by a flat 32% - Throttle follower slowed by 25% at 0mph, and 11% at higher speeds (RPMs drop slower) - Fueling under throttle was leaned out from a Gasoline AFR of 12.5:1 to 12.8:1 - 2* of timing removed above .6g of airmass (Full throttle) - Max Indicated torque was changed from 350 to 630 (Not needed) - Desired shift times were cut exactly in half (Attempting to get firmer shifts) - Converter apply / release MPH dropped by a flat 25mph at all throttle positions - The Low speed fan was set to come on at 195* - The High speed fan was set to come on at 205*
If you follow our blogs, you may notice that I made no mention of changes to MAF or VE since the car left our shop in 2017. That was not an omission. There were no airflow changes made to the calibration from when it was an NA vehicle. I was really looking forward to how the tune on this car would come out, compared to the last iteration. Idle and Drivability Tuning We have a neighbor that likes to come up with stories about me revving cars at all hours of the night, so before pulling into the shop and onto the lift, I wanted to clean up the idle quality. I increased idle airflow, changed the idle spark control strategy, and was able to stabilize the idle surge.
We idled across the street to the Dollar General, and let the car warm up. Air-Fuel as reported by the installed AEM X-Series was in the ~15:1 range. Frustratingly, there was still no cam chop.
We made a few more tweaks to the idle calibration at the Dollar General, and crept back to the shop and onto the lift so that we could thoroughly look the Camaro over. We found exhaust leaks-- several of them... And the on-board wideband was in the Y-pipe, after all of them...
The next morning, I installed my AFR500v2 into the driver's side header, and started calibrating the Camaro correctly. With an accurate gauge, it was idling at a Gasoline AFR of 14.0:1, which is too rich for a cammed vehicle. I made the following changes in the ECU to get the car on track: - Disabled the MAF temporally, so that I could calibrate VE
- Removed excessive fuel in the idle area, as identified by the WBO2 - Adjusted injection timing to not spray fuel during the cam's overlap
- Commanded a more cam-appropriate Open Loop fueling ratio
- Identified the idle speed where the cam was happiest (762rpm at 190*f) - Returned Throttle Follower to factory values - Returned Max Indicated Torque to factory value
Like magic, the Camaro started to sound like it had a cam in it.
The quality of the cam's chop wasn't up to my standards. I spent some more time fine-tuning the Camaro's idle control to produce a nice rhythm.
Up next, was the fun part - Actually tuning the car! I spent the next three hours dialing in both airflow models, so that fueling behaved as commanded, and so that the car would drive as awesome as it used to. In order to get the Camaro to hit the 2-3 shift, I had to add line pressure as well as command the shift at a much earlier RPM to hit our actual 5900rpm target.
Numbers for Nerds!
With the data I had collected from the Camaro, I could definitively tell that this was a 4.8L rather than a 5.3L. Knowing this, I'm able to show you a fairly accurate comparison of the airflow values before and after the cam. Below, I've scaled the VE tables to reflect this 4.8L on Ethanol Free 91 Octane. These tables represent the efficiency of the motor, in that 100% (the peak on the graphs) is total filling of the cylinders at a particular RPM and manifold pressure. Before the cam:
After the cam:
While the "Difference" table easily highlights where the cam lost airflow compared to where the cam gained airflow, you may also be able to visually see how the factory cam offered a broader, less peaky, power curve. Airflow, thus power, was lost below 3000rpm, in order to gain additional airflow at higher RPMs. This is denoted by the largely negative cells before the 3200rpm column.
Aftermarket cams always offer a trade-off. Usually, you're trading low-RPM power for high-RPM power. This is additionally why BTR recommends a converter with a stall speed around 3000rpm with this cam. When the motor accelerates against the unlocked converter, the engine speed sits above the RPM range where power was lost. This cam would have continued to pick up high-rpm power. Unfortunately, the intake system (throttle body, bellows, airbox, and to a lesser extent, the manifold) is a restriction. At higher RPMs, the motor is not able to breathe well enough, and is pulling the intake into a slight vacuum. You can see in the picture below that the Manifold Absolute Pressure drops further and further from ambient air pressure (the dashed line) as RPMs increase.
With the ECU calibrated, and reliably hitting our fueling targets, it was time to hook up to the Dyno and adjust ignition timing.
The Camaro's little 4.8 put down a respectable 290whp at 26* total timing. We didn't find any appreciable gains above 26*, and the motor was not octane limited. Commanded fueling was returned to a gasoline AFR of 12.5:1, and there was no loss in power all the way down to 11.5:1
Before moving on to Nitrous Tuning, Ryan and I installed a fresh set of BR7EF plugs, gapped to .028, and performed a throttle / ignition cut at the end of a dyno pull. We removed a plug to use as a baseline for what Mean Best Torque looks like on the ground strap.
Ryan and I weren't the ones who installed the Nitrous kit on this car, so we made a test-hit to cautiously check that both solenoids activate, and that the jetting is in the ballpark. We were using the Nitrous Outlet recommended jetting for a 100 shot, at 900psi of bottle pressure.
I pulled 4* of timing out of the calibration, and commanded a Gasoline AFR of 11.7:1 under WOT. My philosophy on a plate / nozzle kit is to error on the side of excess fuel. Without port nitrous injection, nitrous will flow into the cylinders unevenly. Knowing that we don't lose power as rich as 11.5:1, and fueling for the leanest cylinder, 11.7:1 was a good compromise between safety and power for the first few hits. Ryan's reaction when hearing the nitrous hit was priceless!
During my ~1 second test hit, fueling settled in at just slightly richer than I had commanded. The image below shows commanded fueling (Red) versus actual fueling (Green). We reached steady state Nitrous and Fuel flow around .75 seconds into the hit. Ramp-in was slower than I'd prefer, however, the kit works how it works, and it'll still live happily this way.
Ryan and I installed a fresh spark plug, and made our first full nitrous pull of the day. Fueling was safe, and the annealing on the ground strap of the spark plug matched the plug from the baseline NA pull, indicating that we have timing set correctly. The Camaro made 410 WHP and 571 Ft/Lb through an unlocked converter.
At the Nitrous engagement point, I softened the timing curve, and commanded a slightly richer air fuel ratio to help keep things safe. We un-loaded the car, and Ryan got to take his first Nitrous car for a drive!
Conclusion Tuning this car from NA to a Cam + Power adder setup was a fun experience. I really love seeing how this car improved as I spent more and more time with it. While the little 4.8 doesn't make *ALL* the power, it will easily get Ryan into all kinds of trouble. I look forward to seeing Ryan back for more power in the years to come!