taking car to the dyno

[rsx858]

Im thinking its time to take the car to the dyno becasue im dying to know what kind of numbers im making. Of course i want to make the most of a trip to the dyno so I was wondering to what extent the car can be tuned on a dyno with the modifications available to us (ITS RX7). I have stock ecu and a new remanned motor.

what exactly can an experienced tech tune on the car with a dyno? and are there any modifications i can make that will increase tunability?

thanks

[C. Ludwig]

Originally posted by rsx858@Oct 13 2005, 12:51 AM
Im thinking its time to take the car to the dyno becasue im dying to know what kind of numbers im making. Of course i want to make the most of a trip to the dyno so I was wondering to what extent the car can be tuned on a dyno with the modifications available to us (ITS RX7). I have stock ecu and a new remanned motor.

what exactly can an experienced tech tune on the car with a dyno? and are there any modifications i can make that will increase tunability?

thanks

62508



Sounds like you're limited to the stock ECU so there is nothing to adjust there. If you have an adjustable FPR...fuel pressure regulator... you can tweak the fuel. You're only concerned with the upper RPM band. Most tracks we'll only use 5500-8500 rpm so that's all we worry about tuning. When you tweak the fuel curve if it get lean or rich below that it's not really going to matter because you shouldn't be using those RPM anyway. Concentrate on the band where you drive the car. If you don't have the FPR I'm not sure how to tweak the fuel. There are resistor tricks you can play with the AFM and other sensors but I've never messed with those. We've found air/fuel ratios in the 13.7 range to give best power. It's a starting point for you.

You can tweak timing with the CAS. Again, you're not worried about what the timing is at idle but what your full advance is through the useable power range. We mapped the timing curve across that rev range on the dyno and then made adjustments accordingly. To save you some time and give you a starting point we found 25* BTDC @ 7000rpm to be MBT...minimum best timing. Meaning we could feed in more timing without knock but made no more power.

On our first trip to the dyno with an S5 setup we started with something like 146whp using the factory setups for fuel pressure and timing. We gained over 20hp that first day with only 6 pulls and it cost all of $100. Money well spent! Since then we've been able to make some tweaks based on the education we got from the 6 runs and have found a bit more power. One of the best investments we've made.

Also, to optimize your time go in there with a plan. Know what you're going to try each run and only try one change. Sneak up on the adjustments. You might skip over the sweet sopt otherwise. A wideband O2 sensor is pretty much standard fair for a dyno operator anymore so make sure they have one where you go. It's an invaluable tool! Take your tools and any other parts you want to try and have your tires aired to proper pressures.

Any questions you can email me offline. ludwigmotorsports at insightbb.com

[rsx858]

thanks for the info i think i will put in the fuel pres reg before the dyno

[Chris Taylor]

Take a couple different designs of plugs. If you're running a K&N, find a Purolator filter and take it with you, too. Assuming what I've learned can be applied to all rotary engines (which it should) that should net you 10HP alone.

If you're running a stock thermostat, see if you can find a slightly higher temp tstat. On a less-than-IT-prep 12A going from 180 to 195 was another 5HP.

- Chris
Who has a 130RWHP 12A that was originally built in 1985 in Japan and has 90,000 miles.... and still has room for more power. :D