Flat Spot/Knock rpmWOT NA FC LT8 (Street Port/Stock Injectors)
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From: Adelaide, Australia
Flat Spot/Knock rpmWOT NA FC LT8 (Street Port/Stock Injectors)
Hi, I would like to learn a little more about the characteristics of the LT8, to understand "maps" a bit more and need some help with aligning feel with data - I am a visual learner.
Quick bio of the car: 1986 Rx7 FC NA. Original motor, injectors, pump. Street port. Manual trans. 5th/6th ports working. TPS has been set to 1kOhm, new plugs, timing checked (with Timing lock ON). Engine has been recently rebuilt, and is nice. Narrow-band O2 only.
It has been dyno-tuned, but that was with a MASSIVE air leak from a busted air pump block-off gasket, and we had the port actuators wired OPEN. It was running rich before, and stinks just as bad after.
I discovered and repaired the air-leak, which caused the car to misbehave - I added fuel at MIXtrm and got it running well enough to head to the rotary tech, who took away the trim and adjusted water/idle/load enough for it to be OK.
After that, I found the reason that the ports weren't opening, and fixed them back up to work again. This caused the car to come alive again, but then it seems to be leaning out a bit as a result, and I reworked the map a bit to be smoother and a bit more driveable to complement.
However....
Can anyone please tell from my Microtech LT8 map why I might be feeling a flat spot/knocking on WOT load? Help me understand the theory.
Where I am getting an issue is at high load/50-Full throttle, 2nd/3rd gear. It feels flat, and sounds like knocking, which I know is a no-no for rotaries.
My guess is the issue somehow lies in the valley in INJms plot in the rpmWOT map between 2500-3000RPM, but I just don't know how that's occurring.
RPM and Load go up with the TPS movement, suggesting this is where I flat foot it in 2nd/3rd, and I think that's showing at 143 on the graph - which relates to the map.txt file attached. Added the Data Log MTL as .txt extension as well.
Other ranges feel fine, but not this point in the map and I don't want to grenade my motor.
Are there any trained eyes that could suggest where I can start to adjust? (yes, I will ultimately get it back to dyno-tune, I just need it to be safe...)
https://cimg9.ibsrv.net/gimg/www.rx7...aa8440c4ae.jpg
Quick bio of the car: 1986 Rx7 FC NA. Original motor, injectors, pump. Street port. Manual trans. 5th/6th ports working. TPS has been set to 1kOhm, new plugs, timing checked (with Timing lock ON). Engine has been recently rebuilt, and is nice. Narrow-band O2 only.
It has been dyno-tuned, but that was with a MASSIVE air leak from a busted air pump block-off gasket, and we had the port actuators wired OPEN. It was running rich before, and stinks just as bad after.
I discovered and repaired the air-leak, which caused the car to misbehave - I added fuel at MIXtrm and got it running well enough to head to the rotary tech, who took away the trim and adjusted water/idle/load enough for it to be OK.
After that, I found the reason that the ports weren't opening, and fixed them back up to work again. This caused the car to come alive again, but then it seems to be leaning out a bit as a result, and I reworked the map a bit to be smoother and a bit more driveable to complement.
However....
Can anyone please tell from my Microtech LT8 map why I might be feeling a flat spot/knocking on WOT load? Help me understand the theory.
Where I am getting an issue is at high load/50-Full throttle, 2nd/3rd gear. It feels flat, and sounds like knocking, which I know is a no-no for rotaries.
My guess is the issue somehow lies in the valley in INJms plot in the rpmWOT map between 2500-3000RPM, but I just don't know how that's occurring.
RPM and Load go up with the TPS movement, suggesting this is where I flat foot it in 2nd/3rd, and I think that's showing at 143 on the graph - which relates to the map.txt file attached. Added the Data Log MTL as .txt extension as well.
Other ranges feel fine, but not this point in the map and I don't want to grenade my motor.
Are there any trained eyes that could suggest where I can start to adjust? (yes, I will ultimately get it back to dyno-tune, I just need it to be safe...)
https://cimg9.ibsrv.net/gimg/www.rx7...aa8440c4ae.jpg
Last edited by REW138; Mar 19, 2026 at 06:07 AM.
Thread Starter
Junior Member
Joined: Dec 2022
Posts: 35
Likes: 0
From: Adelaide, Australia
Last edited by REW138; Mar 19, 2026 at 06:43 AM.
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