Dyno Tuning
10 July 2001
Took the car down to the local dyno mob Chiptorque today for a bit of a run and to get a look at the air/fuel ratio. With the car now running 94 and 105 jets and 34 degrees timing I was starting to wonder what was going on in the rich/lean department. First pull was the best, car ran alright but not smoothly and power was a bit peaky but it made 327hp with an A/F of between 10.5 to 11.0 which is exactly where this current setup needs to be for safety and longevity of my pistons. He got off it around 6000 due to a large amount of smoke coming from under the car as well as a large quantity of tranny fluid seeping on to the floor and the dyno. The pressure had popped the speedo drive out of it's socket. Took about an hour of dyno time to clean up the mess and get the car refilled ready for another run.
The next three runs were disasters. While I was cleaning up the tranny fluid I also took out a bit of timing, down to 30 degrees total, and knocked the boost up to 10psi for the second and third runs. The A/F went way up and power dropped off immensely. Unstrapped her and went home. Not happy Jan.
Confient there's more there, it definitely feels like it on the road so I'll continue my late night street tuning and hopefully get her up to Willowbank next Saturday.
March 2003
Got the car onto the dyno for a bit of a play before we get back to the track next month. Went and saw Aaron from Dyno Source Qld, who has a brand spankin 4WD dyno with all the latest dyno dynamics software. First session ended in disappointment with only 389hp being made and a sudden total loss of boost pressure. Went home and found a turbo pipe had blown off and a dirty big split in one of the hoses that clamps onto the cooler. Fixed, we went back and with no change but 2psi more fuel pressure, the old girl cranked out 542hp at the wheels with 19 pound of boost. Of the 3 power runs we made, air/fuel peaked at 12.5 and she was progressively making more power on each run. There's definitely more there but dyno time isn't cheap and I'd rather see if I can get that power down the track before we try and find any more.
Tune -
19psi boost
88 and 100 jets
27 degrees timing
Just so happened that Dyno Source were having a dyno day on Saturday 15 March, and Aaron encouraged me to enter the V8 blown class just to show what the old girl can do. After the previous few years at summernats, people in Australia have become used to twin turbo commodores making 1000hp at the wheels and I knew I wouldn't go close but thought I'd try to show what a bit of home ingenuity and not cubic dollars can do. Got 2 power runs and she peaked with a best 550.7hp with the same tune as the previous day's testing, but she also spun the wheels on the rollers and my mate's who were watching said she tried to launch off the dyno when it came on boost. It was a very hot day and temps in the dyno room were around the 32 degree C mark, so with a bit cooler weather this tune could still make even more power.
Ended up winning my class, so the old girl picked up it's first trophy.
July 2003
We took the car up to Aaron at Dyno Source to utilize the load mechanism of the dyno in order to properly seat the rings. After a number of various loads during about a 45min period it was deemed this was done and that we'd have a quick look to see if there was any improvement that 8 complete pistons had over 7 1/2 damaged ones.
First pull with 9 psi yielded 410 rwhp, and with the carb and fuel pressure still set for 20+ psi, she was way rich. Next pull with 12psi gave 438 rwhp at only 5300rpm with the fuel pressure becoming unstable. Before the next pull we added a couple of pound of fuel pressure to try and remedy the problem, but with 16psi fuel pressure was struggling to maintain 25psi, way less than what we wanted and the A/F went nuts spiking past the 12.5 mark. Even still she still made 543rwhp which is close to what she made before the bang with 4psi less boost.
We're thinking that the single pump is not able to mainatin the flow required at the required pressure, so another pump will be installed in paralled to see if we can remedy the situation.
Our next plan of attack is to attempt to modify my regulator to give a rise of 2psi fuel pressure for every pound of boost, this way greatly reducing the need for larger jets and as you can evaluate from the graph should allow the horsepower to continue upwards.