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BNR Stage 3 - #'s don't add up.

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Old 05-15-12, 02:45 PM
  #51  
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The more air (cooler air is dense/more air and more timing) you can get in and push out the more fuel you can put in (size of your ports and exhaust, intake TB etc....) so of course your intake/ports, intercooler and exhaust will play a major role.

You are risking detonation when you up the boost a lot and don't gain power because clearly the intake temps are way too hot. If making power isn't easy be happy with what you have because that's what your setup allows.

If I was you I'd turn the boost down to 14 psi which is about all you'll be able to use on your current setup. The extra 15 HP you're getting isn't worth the heat and chance of blowing your engine. Sure you could throw in some c16 and up the timing, run 20 psi and make 400 but why, that stuff never makes sense to me. Make it easy or don't make it. Same with all this injection BS if you need meth, water etc... and you're not a pro drag racer or serious amateur I just don't get it. If your engine is tuned and maintained properly and you're not overloading your setup you'll be fine. If you want more power there's a hell of a lot more to it the upping the boost and adding fuel.

Once the engine lets go you can do a nice port, single turbo, vmount, etc...etc... but IMO 340/350 rwhp in one of these car is all you need and about all the driveline can handle.

For now just enjoy your car and if anything reduce weight and remember rotational weight reduction is X 4.

PS there's a good argument for running e85 if it's convenient to you because it's a REALLY cool running fuel (hard to ignite so no pre-detonation) basically it's cheap race fuel. With this stuff you can safely up the boost and timing and make more power but again IMO your car is perfect the way it is.
Old 05-15-12, 03:38 PM
  #52  
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Lightbulb

Originally Posted by fendamonky
Not to be rude, but I think that the dyno operator may have fudged those numbers to make you feel good. Twins will NOT make 358whp at 12psi, regardless of how happy the motor is, you're talking a (roughly) 140whp increase for 2psi of boost. BNRs or no BNRs, that just ain't happening.
Back in 2003 before I left Texas, my FD with BNR stage 3s non-sequential and every other mod you can imagine made an honest 350 peak rwhp on the dynojet at RP/rx7.com with Chris Ott tuning. I remember Chris was *very* surprised by the numbers, but he didn't have much experience with the BNRs at that point either.

My car went on to make 421 at 17.5 psi on a Dynack a few years later, and 70 more rwhp for 5.5 psi more boost seems pretty reasonable to me.
Old 05-15-12, 05:58 PM
  #53  
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My apolgies for my last post. Autocorrect on the tablet really hit me hard...

Originally Posted by Fritz Flynn
If I was you I'd turn the boost down to 14 psi which is about all you'll be able to use on your current setup. The extra 15 HP you're getting isn't worth the heat and chance of blowing your engine. .
good point, but the BNRs have plenty of breath at 17psi. I have plenty of fuel, and the FMIC doesn't have a challenge keeping the temps low. I will see what my first track event does to this, but even in traffic it was better than a heat soaked M2 SMIC with stock twins breathing hot air.

Originally Posted by Fritz Flynn
PS there's a good argument for running e85 if it's convenient to you because it's a REALLY cool running fuel (hard to ignite so no pre-detonation) basically it's cheap race fuel. With this stuff you can safely up the boost and timing and make more power but again IMO your car is perfect the way it is.
Oh the aweful smell . Imagine the prius guy behind me with a nasty e85 smell, and fireballs coming out the exhaust.... Unfortunately, in Chicagoland this stuff is becoming harder to comeby.
Old 05-15-12, 06:03 PM
  #54  
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I remember driving behind Chris last fall, that e85 crap sinks!
Old 05-15-12, 06:04 PM
  #55  
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If anyone is interested...

Here are the two dyno logs.

The one with RX1 in the name is from 2011. Uncorrected WHP (column E) shows max HP at 291

The one with FosterRX7 in the name is 2012. Uncorrected WHP (column E) shows max HP at 302.4


If you are interested give them a look. The correction values are HUGELY different from year to year.
Attached Files
File Type: zip
Black RX7 Foster426.zip (27.7 KB, 26 views)
Old 05-17-12, 06:26 AM
  #56  
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dfoster,
I noticed that you may not be happy with your RB catback. I'm actually trying to get one right now, and I have a Blitz CBE I'd be willing to trade. The RB is a little more pricey new, so I could work that out to cover the difference. I'll PM you.
Old 05-18-12, 08:58 PM
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OP and boosted414, where in Chicago are you two located? I need to get some better ideas and see more builds before I rebuild mine this winter. I am thinking Efini's or BNRs when I have the motor rebuilt.

Also curious to learn about more shops and local tuners.
Old 05-19-12, 11:25 PM
  #58  
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We are both out in the St. Charles area.
Old 05-21-12, 12:15 PM
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Ahh Cool, I don't work to far from you guys. Wanna grab a beer after work one night and impart all your RX7 wisdom on me?
Old 06-08-12, 12:21 AM
  #60  
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I didn't read all the other responses but I got the same setup and it's all cuz of heat. The BNR have a little more lag but work well at high boost. Get meth and you will be good
Old 06-09-12, 05:06 PM
  #61  
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Update.... definitely compression. Rear Rotor gave out. 80-30-30 for compression.... Guess 43K miles is not bad for the original motor... althought that stress test on the dyno probably didn't help... No this car is not running e85
Old 06-09-12, 09:52 PM
  #62  
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Sorry to hear about the bad luck. Good luck with the rebuild!
Old 06-09-12, 10:02 PM
  #63  
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That sucks, what tool did you use to check the compression?
Old 06-09-12, 11:15 PM
  #64  
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I just went and bought a basic compression tester. Removed the schrader valve and hooked into the plug. I know its not exact, but it quickly proved my concern


http://m.youtube.com/index?client=mv...&v=O_gD4fwtO-0
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