Boost falling off

[sa22c]

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:

1. 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.
2. 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.
3. Get an EGT for $80. This would have little value without professional tuning and hours of dyno time.
4. 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.

[TitaniumTT]

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.

In this case though, it's an ongoing loss. Everytime you drive the car your burning more fuel thatn need be, and fouling plugs quicker than need be

Originally Posted by vrracing

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:

1. 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.

1. Leaning it out will net more power though.
   
   
   

   Originally Posted by vrracing

   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.

   Be glad to help.
   
   
2. Get an EGT for $80. This would have little value without professional tuning and hours of dyno time.[/quote]
   
   Which EGT gauge? I have a feeling that it's not going to react nearly as quickly as it should.
   
   

   Originally Posted by vrracing

   Spend $400+ on professional tuning and dyno time.

That is excessive by our billing standards

Originally Posted by vrracing

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.

Like I said.... it will continue to cost in more frequent oil changes, more gas burned, more fouled plugs and power lost, excessive carbon buildup etc etce etc.

Originally Posted by Pete_89T2

I can give you one sample point to judge return on investment on a similar setup. Currently running a stock S5 13BT with about 50K miles on the block. No porting or internal mods to the engine. I'm running a BNR Stage 1 turbo, with 720cc Bosch FI's in all 4 holes, and a Supra TT fuel pump. Stock ECU with Rtek 2.x mod for control. Intake is stock with a K&N filter, and when I got it dyno tuned last winter, the exhaust was a Bonez DP into the stock main cat, into a Borla catback.

Took it to Dave at Speed1 (Brian's boss) for dyno tuning. Going in with the default Rtek settings (other than checking the box for 720's FIs in all 4 holes), my car put down about 189rwhp, but boost was maxing out at just under 6 psi -- Dave found this was due to a restrictive main cat. After Dave's tuning magic, which cost just under $200, I left with about 210 rwhp. Not bad for boost limited to <6psi!

Over the summer, I managed to get historic plates on the car and yanked the main cat & Borla DP and replaced them with the Racing Beat DP & pre-silencer combo. Still using the stock EBC solenoid as controlled by the ECU which now nets me a very consistent 8~9 psi boost all the way up to redline. Haven't brought it back to Dave yet for dyno tuning, but the butt dyno tells me the improvement is significant -- need to make an appointment to get it dialed in.

That's what I like to hear! When are you bringing that thing back up here?

Originally Posted by sa22c

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.

At that boost level, yeah, .78L (thank you by the way) or 11.5afr is an excellent place to be. Where he is at, .82 is fine.... hell I had one guy tell me to run pump gas @ .85L... I wouldn't do it... not even with the Motec and the FFE kit and the timing SPOT on.

[Pete_89T2]

Originally Posted by TitaniumTT

That's what I like to hear! When are you bringing that thing back up here?

I'd like to get up there some time before the DGRR trip, but I'm still looking into what I should do about boost control. I'm pretty happy with the set up as-is, but it would be nice to be able to dial in just a little more boost.