Club Cobra - Cost of Dyno time

Tru pretty much established the fence posts. When going to the dyno I usually just buy the whole day which up here approximates $1,000 USD.

If you just tune for WOT power is it typically two maybe three pulls. If you tune for part throttle driveability including tip in enrichment (accelerator pump shot and duration) en-leanment when you let off and all those other niceties that make it responsive to the driver's throttle commands you will be spending a while at the shop — which is why I just buy the entire day.

When you pick your fueling model the speed density model is a perennial favorite because of no expense for a mass air flow meter (MAF), no MAF xfer curve to have to work with and the belief that the MAF restricts inlet air flow and costs horsepower.

Predictably none of these 'problems' turn out to be real problems in real life. The MAF will greatly improve the tune quality and allow you to be properly tuned in all types of weather because the EFI is continuously informed by the MAF about the actual mass in kg/hr (or imperial units if you prefer) of air being consumed so the EFI ECU can make correct pulse width calculations for the injectors to meet your target AFR or lambda settings.

By far the most precise MAFs I have ever worked with are the units from Pro-M Racing <= clickable. If you click the link to the left when it opens it will show an imbedded YouTube video on their site illustrating their three best MAFS and the power ranges they support.

If you click on this next link it will show you the precision with which these MAF's measure airflow. Here is the link => Air Flow Voltage Signal Quality Comparison. The Pro-M 80 meter is tested last.

I use a Pro-M 90 meter on my engine because of the power level. On a separate race only 03/04 Cobra we use a Pro-M 117 meter again because of power level. The meter's precision in measuring air flow became apparent to us during the summer two years ago while working on some fueling aspects of the race car tune while the car was in the garage.

We had chosen to air condition the garage because we also use it to build engines and the constant temperature provided by the A/C allows more precision in measurements with micrometers. Reasons for A/C not withstanding, we were experiencing a troubling intermittent reading coming from the 117mm MAF that we could not initially identify the source of.

We had the air cleaner off the MAF while we were fabricating some bracketry to support the MAF. It turned out each time the A/C blower in the garage went on the MAF would pick up the air motion from that blower and the blower was behind the car facing backwards. As it turned out the MAF was picking up the air that bounced off the rear wall of the garage, coming forward and bouncing off the front wall of the garage. We were amazed!

To test our supposition we walked by the front of the car with the hood open and read the MAF signal. It could sense a human walking in front of the car and this was the 117mm MAF not even the smaller 80 or 90mm MAF! As soon as we put the air filter back on the MAF housing the A/C and human air flow movement was hidden from the MAF.

If you want to do it right and have the best tune everywhere the car goes use the Mass Air Model and get one of those three PRO-M MAFs. Nothing else even comes close! Your engine will be happy everywhere you take the car!

Ed

p.s. In the tuning department an added expense but a very valuable tool is EGT sensors. They allow you see each cylinder's exhaust temps and point out lean and rich holes so you can take corrective action in your tuning session to normalize all eight holes. Motec will allow cylinder by cylinder fueling so the balancing act is easier that it initially sounds like.

p.p.s If you haven't already bought the Motec take the time to look at Haltech. They will do 99% of what Motec does but at less than half the price — at least in the US pricing schedules. The difference will easily pay for the Pro-M MAF your EGT sensors and lots of beer and pizza.

In the States Beer and Pizza is considered a food group in certain forward looking locations. More significantly it is essential to precision engine building and tuning :)