Last issue we addressed the exhaust deficiencies of the GENIII and managed to meet our target of exceeding the power of a GTS , at the same time providing a real low down torque increase over both the std Monaro and the GTS.

Graph1

Testing both at the drag strip and on the dyno showed that we had a intake problem , both in terms of heat buildup and intake restrictions.

While the Monaro intake system is better than the STD SS it had some flow issues and was drawing excess heat from in the engine bay , especially when the A/C was on. Initial testing using the dynamometer data logging of intake pressure showed we were drawing a vacuum under full load still . Ideally the full load intake pressure should be the same as atmospheric pressure if the intake is working correctly.

the first test was to check if the air filter was a restriction , tests were conducted on a new std air filter element , a K&N element and no element at all to see what benefits we could find. Testing showed that a std air filter was as good as the K&N and no element at all, obviously after 5000kms of use the std filter would be blocked more than the K&N so we elected to keep the K&N in as it has the added benefit of being able to clean it at will and being reusable.

 

 

Next it was time to look at the MAF pipe as it appeared to have be a restriction in cross sectional; area  , a Convoluted pipe and a smooth bore 4" custom pipe and a new plastic 4" moulded pipe was trialed. Power gains were found with all of the intake pipes but we elected to stick with the Moulded 4" pipe as much for appearance sake as the added power increase .We will use this same intake pipe for all our testing .

The tune was then optimized again to suit this new pipe as our baseline , power had at this point picked up226.9kw with the std air box modified and the K&N air filter installed.

Different air boxes were now tested , with our std Monaro modified air box used as the baseline , and a modified HSV air box system , power at this point was unchanged but the HSV box produced a slightly lower intake temp consistently due to it being better sealed around the headlamp than the std Monaro CAI which draws air from around the top near the radiator as well resulting in hot radiator air being ingested.  We also tested a popular widemouth CAI but found large horsepower losses above 4500rpm due to a restriction over the radiator cowling so we abandoned any further testing.

The MAF at this level has become the next restriction so it was time to remove it. On a manual this can be done as the GTS runs without a MAF  std but on a auto the original coding has no input for this and the auto box will not change gears properly , locking itself in 2 gears. A intensive disassembly of the operational code in the ecu was required , resulting in Daniel rewriting the code to allow auto to function properly without the MAF.

After a couple of sessions on the dyno to optimize the fuel curve as we were now running in speed density mode rather than MAF mode the power had suddenly had a huge increase , further optimization of the tune resulted in 241.8rwkw  , some minor intake restrictions where still present and as we had seen minor power gains from running with no air cleaner it was decided to test again with a large K&N pod filter to see if the extra surface area was going to help. Power jumped again to 248.2 rwkw after a mild session reoptimization the tune to suit the increase airflow. This created a dilemma as a pod is ok on the dyno where it can be positioned to get some cold air feed to it but on the road with the bonnet closed this would not work so a complete air box was designed to house the pod still utilizing the seal around the headlight to draw air from under the vehicle ( we could have cut big holes in the body but that went against our idea of keeping the car street legal as there are issue with cutting in the engine bay due to it being a crumple zone)

Lastly we tried a larger throttle body , on the GENIII the manifold is necked down to 75mm on the opening and there is no real way to overcome this so we looked at various Throttle bodies on the market and utilized one that was 84mm on the entry and had a larger area as it passed through the throttle blade before squeezing back down to 75mm at the neck , this helped to funnel the air into the manifold and elevated the throttle blade and shaft restriction. Minor power gains were found with peak power coming to 251.2 rwkw

 

with all the spark and fuel mapping modified to suit it was time to hit the road and optimize the transmission calibration to get the shift points were we wanted them and to optimize the shift pattern for the street as well as the drag strip.

Economy mode became our auto calibration for normal street use and power mode became our drag strip mode with hard crisp shifts and increase shift points to suit our new found power. power mode now resulted in the car turning the tyres hard on the street in every gear change so it will be reserved for the track as it would be lethal in the wet as it is.

Time to head to the track and see how it had all panned out, first pass out resulted in wheel spinning 13.15@108mph .

Several passes later and out sixty foot times were going backwards due to the wheel spin so it was back to the workshop to try and find a solution.

Fitting slicks at this stage would solve the problem but our aim is to see how far we can push the std car so it was decided to try and tame the low down power output at the track , a careful look at the data logging using efilive showed that traction was being achieve once the car go to the 330 foot mark , so if we could limit the power output below 3000rpm the we should be able to get the car off the line. A careful detuning session resulted and we headed down to the track again.

WE did it , the car was now running 12.98@109 mph , making it the fastest std LS1 in the country , with no slicks , no converter , stock suspension , stock motor and a careful approach to bolt ons and tuning.

We also believe it is the most powerful Stock LS1 at present especially in auto trans format having lifted power by 83kw at the back wheels , with a corresponding lift in torque right through the whole rev range.

Next issue we will take the leap and see how a new Dominator hi stall converter will affect the drivability of the car and the 1/4 mile times - naturally slicks will now be required as it should really push the engine into its meaty part of the power curve. Then hopefully we will look at opening the Motor up and fitting a head and cam package

 

Click Here for Part 3

Source:

Chipmaster.

9452-0213.