Justin Abbott: Modifying a New GS – LS is the Best Chevy V8, Period
Editor’s note: Justin Abbott is vice-president and technical supervisor at Zip Products, Inc. We’ve invited him to give us some insight into how the company tests and develops parts for their extensive catalog. Here’s what he had to say. – Paul Huizenga
The LS engine platform is the best engine GM has ever had. I know there are some die hard small and big block guys that think otherwise, but I will show you what those engines could never accomplish. – Justin Abbot
We are going to start with a new 2011 Corvette Grand Sport, and while it is not a 2012, it is a brand new left-over. The first dyno run was done with 800 miles on the clock. This particular GS was an A6 automatic. The car runs fairly well, but I did have a check engine light when I first picked the car up. A quick check of the gas cap fixed that. So now it was time to pump the tanks dry and fill up on some Sunoco 94. I do this because every brand of gas has their own blend and since we are always testing Corvette parts, I like to use the same brand so I know that at least every tank is very close to the same fuel makeup.
With the tanks full of the Sunoco, I headed out to one of my trusted dynos. We typically use several different dynos depending on what we are trying to do. This time, it was just to get some good baseline numbers, so we used a Dynojet 248.
Getting a Benchmark
Once the car was strapped down it was time to hook up the scanner and get to work. The first step was to make a first run and see what the GS could do. The first pass was good with 383.82 horsepower and 380.65 foot-pounds of torque. Next, we reset the fuel trims to see what she would do. I made five runs after this, trying to get the car back to the same engine coolant temperature before each run. The best the car could do was what it did in the first pass; the closest to it was 383.06 horsepower but 377.35 foot pounds of torque. Now this is not enough difference that even the best driver would ever feel it, and it falls in the inherent plus or minus accuracy of the dyno. So with data in hand, it was time to head back to Zip to add some parts.
We have several power packages that we offer, but they are a far cry from the typical parts you see advertised in the marketplace. The first item that we added was our stepped Kooks headers. These headers were designed originally to compete in the World Challenge for Banner Engineering. We were building differentials for them and a phone conversation ended up with George from Kooks Custom Headers building Zip a special set of headers. From there, the headers were used for some mock up on the then-new LS7. They did so well in the midrange that we decided to go ahead and have our own header made for us by Kooks. We have since made some ever so slight changes and we are also using them on the LS3 engines and modified LS2’s.
Air Err is Human…
The next part added was our own Mamba Air Intake Box. We started designing this box back in 2004, but it was not until the release of the LS7 in the C6 Z06 Corvette that the light bulb went off. We had been designing an air box around the filters that were available instead of designing a box and then having a filter made for it.
With the new design of the LS7 box with that huge Donaldson air filter in mind, we set out to make the best CAI available. The first design was by far the biggest air box that was in a Corvette and it looked awesome. There were some rough roads ahead to get a finished item, but our friend Ed from TKO Performance had just come out with his new line of Attack Blue filters and he had a filter made to fit the Mamba.
On top of the new design, the Mamba was made out of genuine 2×2 twill carbon fiber, the same stuff used on real race cars and the Team USA bobsled. Our Mamba Air Boxes are built by hand and cured in an autoclave just like they do with the Indy Car body panels. So obviously, we are a little biased, but we have seen some great numbers with it and we have also added a honeycomb airflow straightener to clean up the MAF signal and eliminate surging that was so common in the LS7 and LS3 air boxes.
The downside – if there is one – is that on a LS3, PCM calibration is required because of the increase in air flow. If you do not calibrate an LS3 car, you will end up with a WOT air/fuel ratio in the low 10’s because of the increase in airflow and the way the factory calibration is “biased” on that end of the scale, so to speak.
I like the added comfort knowing that that we will have no issues of damaging our motor because we sabotaged the ability of the PCM to keep us safe.
So with these two great parts added, the next job was to control the heat. Heat is the worst enemy of any Corvette. But you may be surprised to learn why. The GM engineers are very smart people and with that being said, they incorporated some safety into the calibration of the PCM. You have an ECT (Engine Coolant Temperature) timing retard and an IAT (Intake Air Temperature) timing retard. Starting at about 200 degrees Fahrenheit, the PCM will start to remove timing so the engine will not pre-detonate (spark knock).
This kills horsepower, depending on how much it removes. The easy way some tuners battle this is to eliminate or lower the amount of timing that the PCM removes, but this is really not the right way to handle it. The timing is there for a reason, so our philosophy is to not get the temperature there and then we don’t have to worry about it. On those really hot days, I like the added comfort knowing that it is there and that we will have no issues of damaging our motor because we sabotaged the ability of the PCM to keep us safe. To increase cooling, we installed a DeWitts HD aluminum radiator.
Keeping the Fire Lit
We also added our HD spark plug wires that are made for us with a Magnecor wire. I strongly suggest that everyone visit their website and read up on the truth about spark plug wires. For years, I had the wrong idea about what to look for in a spark plug wire until a very smart engineer friend of mine pointed me in this direction.
Our wires are shielded from the extra heat, being in close proximity of the header tubes, with DEI heat shields. Next, we also added a set of Corsa cat back mufflers to finish out the package.
The Proof is in the (Dyno) Pulling
You could get into this GS and take a drive across the county in traffic, if you wanted to.
Now – back to the LS engine family and the hardcore early SBC and BBC crowd. I can’t think of any small block or big block that you add a couple of parts to and have that kind of power output and still be civil enough to let your mother drive it to the grocery store. You could get into this GS and take a drive across the county in traffic, if you wanted to. Having personally owned many earlier Corvettes, I can’t think of any of them that could do that and put down 428 horsepower to the ground.
Zip is not being very intrusive on what we are bolting on to the engine. The original factory engineers did a really good job on the calibration for a universal customer; however for performance-minded individuals, there are some things we need to focus on. First and foremost, we need to get the PCM to deliver what we ask it to. Part of this important process is to have the right equipment. Depending on the year of the Corvette, I use a EFILive V2 interface or the HPTuners Pro interface. They both have their pros and cons, but they both get the job done.
My most important piece of equipment is my wideband oxygen sensor. Why is this so important? This is the one sensor that all of our programming is being based off of, so accuracy is key. I use an ECM AFM1500 which has a serial output to my interface. This is what the OEM’s are using, it has an accuracy of 1% and there are different models that ECM makes that are within ½ of a percent. But you must be willing to pay for accuracy – the AFM starts at about $2000. So why not a $199 wideband sensor? Remember – accuracy is key. If your wideband is 5% +/-, that is a variance of 10%. That could easily be the difference between an engine that lives on a hot day at WOT, and one that does not.
With all of this together, it allows us to create power packages that have parts that are designed to work together and the end result is a customer that is very happy with his or her Corvette. Yes, there can be a lot of work involved in testing products to make sure they do what we expect, both by themselves and as part of a package, but there are certainly worse jobs in the world than working with new Corvettes…