Quote:
Originally Posted by vrracing
Yeah, in my very first post I noted that the AFRs were George Soros rich. So I'm not sure I understand why that is attracting so much attention. TTT wanted to see the timing map so I pulled those charts for him. But we haven't had a chance to lean out the fuel map yet.
I don't look at "optimize" as binary. As my production engineering prof emphasized to us "perfect tolerances are infinitely expensive." I run software development orgs and we discuss product investments in terms of "marginal rate of return". Basically you reach a point where each additional dollar of investment returns less and less value.
I'm familiar with EGT monitoring as we monitored it on his sprint car using an Aimsports system and would adjust jets and send the logs back to our engine builder. And like W/B O2 sensors they can degrade with catastrophic effects.
My sense from the discussion so far is that the tuning knobs we can turn in decreasing order of margin rate of return are:
- AFR tuning leaner than AC's rule of thumb numbers. We are way outside the ballpark now and while we won't maximum any parameter it will make the car more fun and reliable. And 10psi of boost at 10AFR is a lot more fun than 4.5psi.
- Once the AFRs are in the ball park we can gen another set of charts and we might see that timing adjustments may be warranted based on TTT's expertise and experience.
- Get an EGT for $80. This would have little value without professional tuning and hours of dyno time.
- Spend $400+ on professional tuning and dyno time.
What I dont understand is what does the marginal rate of return curve look like as you traverse these investments. For example, if we do step 1 and get 250rwhp if we spend the $500 for steps 3 and 4 will we end up at 255rwh or 350rwhp and 30mpg city?
We'll get the AFRs in line and then post more charts.
Thx all. |
blah blah blah
If you set the car up right, a V-trim compressor on a standard series 5 rear end with appropriate fueling is good for 22+psi in the midrange (I know a guy who ran 25psi).
People will cry and moan it can't be done, but mid-high 10 second quarter miles at mid to high 120s to low 130s are possible in a 79-85 RX-7. In the heaver FC3S low 11s (like 11.0) is possible with a turbo that small. People have been doing it for probably 10 years.
Whats even better is people have been doing it since the mid 2000s without race fuel.
0.78 lambda is a good figure to shoot for. Frankly I'm an graduate engineer (with honours) also. I work in research and development. Most of the muppets on the internet, its not even worth reading their posts. I'm yet to lose an engine from anything but old age and I have a car that can be daily driven and is in the 11 second bracket now. I've probably put 60k miles on my car since I've owned it.