Log RPM not equal to actual RPM

Vehicle specific forum for tuning the Foxbody Chassis Mustangs utilizing the LUX0, GUFA, GUFB, and GUF1 Strategy

Log RPM not equal to actual RPM

Unread postby yeastieBoB » Sat Jan 06, 2018 11:39 pm

I went for a drive to take some logs for dialing in FN035. The RPM (NE) in the log appears to be lower than actual RPM. I let off ~6500 and the highest WOT RPM my log shows is ~4900. My shift light did come on and it's probably set around 6500. The highest RPM in the log is 5100.

I took two logs and the RPM in both seems off.

What could cause the RPM to be understated and what impact would that have on the engine?
'93 coupe, rebuilt stock internal 302, ProM 80 MAF, 75 TB, Victor 5.0, Stage 3 High Ports, 30# inj., 255 pump, B303, 1.6s, Tremec 3550-2, 4.10s, full exhaust, Moates QH v1.6.Q, TunerPro RTv5, X3Z/A9L2/GUFX. Mostly untuned stock bin went 12.68 @ 111.69.
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Posts: 45
Joined: Sat Jun 21, 2014 7:02 pm
Name: Robert
Vehicle Information: '93 Reef Blue coupe. Stock internal 302, 80 MAF, 75 TB, Victor 5.0, High Ports, 30# inj., B303, 1.6s, Tremec 3550-2, & 4.10s. Cobra EEC mostly untuned went 12.68 @ 111.69.
Vehicle 2 Information: '66 F100 shortbed, 352ci, 3 on the tree - on hold
Vehicle 3 Information: '65 Coupe rolling chassis - on hold

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