The Monsterbox 4 Rotor
If you mean the lean wideband readings on the dyno charts, it's pretty common to see that when an O2 sensor is mounted near the end of a large-diameter exhaust system. I'm not sure if it's entirely due to reversion at low RPM, or if the exhaust gases just aren't passing by the sensor quickly enough to overcome all the fresh air at the end of the tailpipe. I've also heard of piston engines with high-overlap cams seeing lean-looking wideband readings at low RPM because oxygen is going right out the exhaust port rather than travelling through the engine and getting turned into combustion gas. Previous generations of hot-rodders tuned engines before widebands were common, but I hear it took more time and may have involved more risk.
Last edited by scotty305; Nov 6, 2018 at 08:02 PM.
Senior Member
Joined: Oct 2007
Posts: 363
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From: N.J
If you mean the lean wideband readings on the dyno charts, it's pretty common to see that when an O2 sensor is mounted near the end of a large-diameter exhaust system. I'm not sure if it's entirely due to reversion at low RPM, or if the exhaust gases just aren't passing by the sensor quickly enough to overcome all the fresh air at the end of the tailpipe. I've also heard of piston engines with high-overlap cams seeing lean-looking wideband readings at low RPM because oxygen is going right out the exhaust port rather than travelling through the engine and getting turned into combustion gas. Previous generations of hot-rodders tuned engines before widebands were common, but I hear it took more time and may have involved more risk.
I’m pretty sure it’s a lean mixture, it’s reading lean and breaking up With no exhaust smoke.
You might be right; I've seen smoke from my RX7 and other cars when the fuel map was too rich. Then again I haven't tuned a peripheral ported 4-rotor so I don't really know how it would act. I didn't notice smoke during the pull at 7:55 in the video (not until the they lifted the throttle), and the dyno plot at 8:08 was showing AFR readings in the 9's. I'm also hoping the ECU logs would include wideband data from a sensor mounted in the downpipe and the dyno wideband is just a second set of numbers for quick reference. The sensor clamped onto the rear tailpipe isn't the best way to get accurate readings, the non-rotary tuning community experiences false lean readings at low RPM too and they often build setups like this to help : Lambda Meter Probe Design
Thanks for letting Rob post that video on youtube, it's really fun to see dyno footage of rotaries and really a special treat seeing so much footage of this car.
Thanks for letting Rob post that video on youtube, it's really fun to see dyno footage of rotaries and really a special treat seeing so much footage of this car.
Thread Starter
Mazzei Formula
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Joined: Jun 2006
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From: Birmingham, Al
We had lean transient spike when stabbing WOT, because we didnt realize the values in the transient duration settings were 0 to 1000 not just 0 to 100. It has since been fixed! Car is insane. 1000hp on 18psi, made same powrr at 20 because tires were throwing rubber everywhere! We turned her down to 12psi for now at 680. Shes wicked ! Sevenstock and sema were dream come true. So glad to meet all you guys in person. I live in a small bubble here in Alabama. But now I understand the real rotary world! It's amazing
will update more soon when I get off the road. Been traveling back 30hrs
will update more soon when I get off the road. Been traveling back 30hrs
Senior Member
Joined: Oct 2007
Posts: 363
Likes: 1
From: N.J
Tbh I thought it would make atlease 800 whp @12 psi giving most 3 rotors make Around 600 whp or better around that boost level with a 80mm turbo. But 1000 whp at 18 psi is pretty solid. Gonna be a scary ride.
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Joined: Feb 2006
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From: CHICAGO
He built the car twice. Sounds like he is happy with it being a little conservative on the tune. Making 600rwhp is nuts, in a 7. He did make 1000, has to be one the sickest Rx7 to date. Enjoy it!!
Well if you halve the numbers and compare it to a 13b, 340rwhp at 12lb is nothing to sneeze at.
I don't see it that way at all. Like Rob said, he personally likes to push the envelope on power. Some people prefer a more conservative build and this 4 rotor in theory should be more reliable than a 3 rotor making the same power. That's what I got out of it anyway.
