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RPMs & Duty Cycle Lines on Graph Wavy in VTEC

Posted: Sun Aug 04, 2019 7:42 am
by G. Wiffington
Hey guys I was wondering if anyone could give me some insight as to why I am recording a pull through VTEC & on the datalog it shows the lines for the RPM & Duty Cycle are wavy like something is no reading right.

In my datalogs it is fine until I hit VTEC then the RPMS are not consistently going up, the line gets choppy as well as the Duty Cycle.

The car runs great, pulls real hard & doesn't have any issues but I just keep datalogging & seeing the lines real wavy. I saw a video of someone dyno tuning where there lines were like that & they pulled some timing & it smoothed it out but I pulled some timing & there wasn't much of a difference.

My setup is a 2000 H22A Euro R with bolt ons in a 1993 Honda Accord EX.

Thanks guys.

Re: RPMs & Duty Cycle Lines on Graph Wavy in VTEC

Posted: Sun Aug 04, 2019 8:31 am
by Hondata
The duty is wavy because it is calculated from the rpm so ignore the duty. The rpm signal has a lot of noise, and you can see it gets a lot worse at VTEC. So check the distributor wiring, the engine grounds and the ECU ground. Then look at the distributor.

Re: RPMs & Duty Cycle Lines on Graph Wavy in VTEC

Posted: Sun Aug 04, 2019 12:37 pm
by G. Wiffington
Okay thank you. I will look them over.

Re: RPMs & Duty Cycle Lines on Graph Wavy in VTEC

Posted: Tue Aug 06, 2019 6:28 am
by G. Wiffington
From another forum, "The aftermarket distributors have poor cam/crank pick-ups in them plain and simple. Do they work, yes. Are the signals clean, no. You cannot really "see" cam or crank signals in the OEM based tuning systems, so you really have no idea what is going on. Crank relates to RPM trace, so a round about way to see if at least the crank signal is dirty is look at the rpm trace during a dyno pull. I had a h22 recently on s300 with a distributor king distributor that was hitting rev limiter, despite my "stop" rpm on my dyno 500 rpms sooner than the rev limiter. Looking at the datalog the rpm trace started getting super choppy above 7k, and was so bad it was prematurely hitting rev limiter. It was repeatable every single time. I pulled the cap off and look at the pick-ups and everything was tight. Swapped out to a OEM high mileage h22 distributor and rpm trace was smooth as glass and no more premature rev limiter. Unfortunately I have seen this several times with aftermarket distributors on d/b/h series engines. "

I am running a cheap Ebey TD-60 Distributor. I found my issue. Now I just need to source a H22 OEM Distributor.


Posted: Tue Sep 17, 2019 8:24 am
by G. Wiffington
I finally found a H22 OBD1 Distributor & my datalogs are nice & clean. No more wavy lines.