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-   -   Bouncing AFRs (https://www.miataturbo.net/megasquirt-18/bouncing-afrs-16859/)

richard_ha 02-10-2008 10:14 PM

Bouncing AFRs
 
2 Attachment(s)
You can see on the graph here the AFRs bouncing from 11 to 13.

Any idea what could be causing this?

bryantaylor 02-10-2008 10:34 PM

looks like you have your O2 turned on in boost too

richard_ha 02-11-2008 07:29 AM

O2 turned on in boost?

richyvrlimited 02-11-2008 08:37 AM


Originally Posted by richard_ha (Post 212303)
O2 turned on in boost?

running closed loop when in boost.

generally not a great idea as the response time of a WB sensor isn't as quick as a NB.

can be compensated for in the software iirc, but it still won't be perfect.

hustler 02-11-2008 09:07 AM

change your open-loop switch point to whatever (60-90kpa) or you have o2 sensor noise.

richard_ha 02-11-2008 09:20 AM

It is set to 90kPa already, isnt it?

richard_ha 02-11-2008 09:29 AM

1 Attachment(s)
I'm wondering if I've got a sticky injector or something. Look how rich this went (right to 8.9) after I did a 1/4 mile, even though the PW was 0

richard_ha 02-11-2008 11:28 AM

OK, think I've figured it. The noise on the MAP is causing the acceleration and deceleration flags to get lit so it must be dumping fuel in for the acceleration enrichment. Looks like I'll need a TPS.

cjernigan 02-11-2008 11:30 AM

Where is your MAP line connected?
If you have it on the nipple by the throttle body you should try Ting it off the FPR line instead.

richard_ha 02-11-2008 11:36 AM

1 Attachment(s)
Attachment 214558

cjernigan 02-11-2008 11:40 AM

yes
The port near the throttlebody is known to be noisy. It causes issues like you're seeing sometimes. Ting off the FPR port is supposed to cure that.

richard_ha 02-11-2008 12:30 PM

Cool, I also had a "no buzz" t piece so I've used that.

richard_ha 02-12-2008 11:52 AM

1 Attachment(s)
What a difference T'ing in there and using a no buzz T piece has made, look how smooth this MAP is now...

Sleeper_MX5 02-12-2008 12:07 PM


Originally Posted by richard_ha (Post 212440)
Cool, I also had a "no buzz" t piece so I've used that.

just wondering what is a no buzz?

richard_ha 02-12-2008 12:13 PM

Its like a normal t piece but the spout that comes off only has a small hole in it to prevent too much fluctuation.

cjernigan 02-12-2008 12:58 PM

You can buy a restrictor for the map line at any advanced autoparts store. AKA No buzz.

Glad that fixed it.

richard_ha 02-12-2008 07:59 PM


Originally Posted by bryantaylor (Post 212248)
looks like you have your O2 turned on in boost too

Are you sure? Looks like its set to 90kPa to me, unless I'm missing something.

240_to_miata 03-13-2008 05:12 PM


Originally Posted by cjernigan (Post 213047)
You can buy a restrictor for the map line at any advanced autoparts store. AKA No buzz.

Glad that fixed it.

What does this restrictor look like?

Also.. is the vaccuum source next to the throttle body you guys talk about the one on the 1.8 manifold on the top by the fuel rail?

cjernigan 03-13-2008 05:30 PM

The restrictor looks like a little plastic tube with a tiny hole in it.
Do not use the one near the throttle body by the fuel rail.
Tee off of the line going to the fuel pressure regulator, it is a much better signal location.

240_to_miata 03-13-2008 05:45 PM

yeah i was gunna make a thread about my jumpy MAP values. It always fluctuates about 5-10 kpa real fast no matter how steady i hold my foot. Ill try it out and hopefully get a better reading


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