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Old 10-24-2020, 12:15 PM   #1
marcusj2001
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Default Megasquirt hot start afr oscillations

engine spec:

b230ft with
90+ turbo manifold
ebay t3t4 turbo
Kl racing t2 cam
compression ratio 9.5
1226cc injectors

The MAT air density table is set 102 at 0 deg Celsius and 100 from 20 to 50 deg Celsius

I'm having trouble with hot restarts, The AFR swing from 12:1 to 22:3 and the rpms are swinging a lot to. It does the same thing when increase the rpm and i hold the throttle steady. I have tried increasing the ve and changing the dead time if that was the issue but no change. Tried changing the after start enrichment with no change, also tried changing the fuel pressure but still no change. Even tried running the fuel pump all the time but no.


The AFR swing a lot. but the pw is going up and down to trying to compensate almost. See the log.

So what can cause this to happen?

Tune and logs of the oscillations

should work now.

https://www.dropbox.com/sh/wzap876p1...Fb9pN_5pa?dl=0

Last edited by marcusj2001; 10-27-2020 at 08:00 AM..
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Old 10-26-2020, 11:56 PM   #2
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Sorry, your dropbox link is bad so I can't see the logs or .msq

Do you have automatic EGO Control enabled? If so, try disabling it, or try half the step size, or double the events per step, or both. Are your VE and Ignition tables fairly smooth or somewhat lumpy?
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Old 10-27-2020, 12:14 PM   #3
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Make sure your AFR table is right in the idle area (not 14.7) so the O2 doesn't drive it off target.

try flattening the MAT Air Density Table in your hot start/idle area?

Also make sure there is minimal heat soak on your MAT sensor, I mounted mine in the end of the air filter cone.
Away from the radiator and not in the intake manifold.
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Old 10-27-2020, 01:45 PM   #4
marcusj2001
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Iat sensor location see picture
[IMG][/IMG]


Mat air density correction table see picture
[IMG][/IMG]

The afr table is set to 14.7 at idle or lambda 1 for the yearly inspection here in Sweden so it's need to be idling at 14.7 to pass the emission test they do. If i start it and put it in gear and drive for like 15-20 sec it goes away. it's almost like it's not getting fuel in the fuel rail because after it settle down it idles perfect.

The ego is on but it's not fast enough to correct for the afr swing.

It started after i rebuilt the engine. Before that is hade no problem with the hot start. I may have f**t up a cable or something in the process of installing the engine.

I have played around with the ase setting and increasing the taper to 300, and the ase is set to 18% but to no noticeable difference.




ve table not clean up in boost and higher rpms. But down low it's almost perfect.

[IMG][/IMG]
[IMG][/IMG]

Last edited by marcusj2001; 10-27-2020 at 02:01 PM..
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Old 10-27-2020, 08:53 PM   #5
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I'm really not very good at deciphering tuning problems from weird log files. That being said, I'd cleanup the ignition table at lower rpms -- get rid of the noisemaker entries and swap the 700rpm/900rpm columns. You generally want some extra advance if the rpm's drop below target idle rpm.

I'm not familiar with the MAT density correction table - I'd use the default unless you really know what you're doing.

While you have EGO control enabled, it's not doing anything due to the high/low kpa limit settings.

I see that you have flex fuel enabled too. When you get to trying to use it, check the msextra ms2 development forum - I think there's a new firmware release in process that fixes some of the flex issues.

In megalog viewer, you can load up your log and then load your msq via the File-Open menu. This should show 2 of your tables on the right. You can select which tables by clicking on the table_name box, and you can enlarge them by moving the screen divider. Start with the VE and the Advance tables. With this, click your cursor on a region of interest in the waves. You can then use the left/right arrow keys to advance through the log and watch what table cells are being hit. This may help figure out what's changing to cause the oscillations.

Good luck, and maybe someone better at log reading and tuning can offer some better suggestions.
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Old 10-28-2020, 01:26 PM   #6
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Okay I will try that and see if it helps. Updated to 3.4.4 now to.
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Old 10-28-2020, 02:17 PM   #7
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The Volvo B20 E and F are prone to a problem called hot injector syndrome (HIS). If the injectors have heat soaked on shut down, following restart the flow rate through the injector is reduced causing high AFRs and unstable engine operation. The hot injector problem normally goes away after a minute or so of operation because fuel flow through the injector cools the injector off. That sounds a little bit like your description
Quote:
If i start it and put it in gear and drive for like 15-20 sec it goes away.
.

Thing is, HIS is typically a problem on engines with cast iron heads and none cross flow design where the injectors are positioned over the exhaust manifold. Various strategies have been developed which includes 'pigs in a blanket' (wrapping the injectors in insulation. Volvo retrofitted the B20E with insulating washers on the injector holders to reduce the problem. I am not aware of HIS being a problem on the B230 engine. However, it may still occur; but, not be so significant as to cause a problem.

There is a simple test for HIS. After the engine has been running and everything is hot, shut the engine off and then immediately restart it. The quick restart avoids heat soak in the injectors. If the oscillation / AFR problem does not occur with the quick restart then repeat the test; but, wait 3 - 5 minutes to allow the injectors to heat soak. After the wait, do the restart and if you get the oscillation / AFR problem you may have HIS. On my B20E there is about a 45 second 'window of opportunity for a problem free restart. After about 45 seconds the injectors have started to heat up enough that you start to see lean operation.

On the Volvo B20E, HIS is always present on a hot restart; but, high ambient air temperatures (> 30 C) make the problem worse - the engines may not restart or if they do they idle like crap. If air temperatures are cool the above test may not work so well in terms of monitoring oscillations because they may not be bad; but, if you monitor AFR you should still be able to see it as the AFR runs high until the injectors have cooled off.

It would be unusual that your B230 suffers from severe HIS; but, the test is simple so give it a try.
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Old 10-28-2020, 03:50 PM   #8
marcusj2001
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The firmware did not help.

I did the HIS test and here is what i got.

shut of and start immediately it runs fine. After a 10 min wait it's runs leaner after start see the log like 15-16 to 1 instead of 14.7 to 1.

After another 20 min wait the very AFR is lean again see log.

So it's seems like it has something to do with hot injector like you said 142 guy.


should I just increase the after start enrichment to help with the problem?

immediately restart log
https://www.dropbox.com/s/f1y2c3a8st...46.29.mlg?dl=0

10 min what then restart
https://www.dropbox.com/s/5957x0skj6...06.06.mlg?dl=0

20 min what then restart
https://www.dropbox.com/s/3nn022v8cz...31.48.mlg?dl=0

Last edited by marcusj2001; 10-28-2020 at 04:01 PM..
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Old 10-28-2020, 05:25 PM   #9
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That is what I did.

My ASE taper is a Vee curve. It bottoms out around 60 C at 215 and then increases in a straight line to 413 at 90 C. My ASE adder bottoms out at 60 C at 20% and then increases to 30% for coolant temperatures above 60 C. That does not completely eliminate the high AFRs following a hot restart; but, it is good enough that on a hot day the engine will run smoothly and I can drive it without problems. As you note, if you drive it the injectors cool off faster and everything returns to normal faster than if you let it idle. My settings are for a naturally aspirated B20E, not a B230F and I have not spent any time trying to optimize them. They are good enough to allow for reliable operation so I have not been motivated to do more fiddling.
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Old 10-28-2020, 05:39 PM   #10
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Thank you for the advice, I will try it out tomorrow to see if it helps. I will post the result.
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Old 10-29-2020, 07:57 AM   #11
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Are you sure you're getting good afr readings? I know mine shows some goofy things until everything warms up. Does the car drive any differently with the lean readings? Are you hearing knock? How old and what kind of O2 sensor? I know mine is supposed to be calibrated every so often and before and after racing, mine is the lsu4.9.
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Old 10-29-2020, 02:33 PM   #12
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I have not had any luck in trying to get any motor to idle at 14.7AFR.

Maybe a newer motor but not a vintage Volvo.

It will surge and likely stall with AFRs that lean.

You can't force it to run that lean, give the motor what it wants. If it's not clean at a "lean best" AFR you have other problems. (Bad convertor?)
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Old 10-29-2020, 02:51 PM   #13
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I can get any of mine to idle there (I can get em to idle elsewhere as well usually. with and without an idle valve), but sometimes it takes more work than it's worth.

I would do this: adjust your after start enrichment for hot re-starts to be higher for longer, and see if that helps.
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Old 10-29-2020, 05:13 PM   #14
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02 sensor is a lsu 4.9 with a Innovate lc-2 controller 1.5 years old. calibrated a mouth a go so no problems there I think. The afr when it's cold are normal no fluctuation at all

To idle at 14.7:1 is no problem for me. /The car is manual

I think it help. But when a went for a ride the car ran great but then out of no where it went real fat like from 14.7:1 to 11:1. I think i have some bigger problems then the hot restart now. The only think to get the normal afr back was to lower the ve number. Ve number was 49 and to get the back to normal I hade to lower the ve to 33. I will troubleshoot tomorrow and see what happened. Maybe a stuck injector or something among those lines.

Edit i think it happend when i turned on autotune. That the afr became fat.

Last edited by marcusj2001; 10-29-2020 at 05:32 PM..
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Old 10-29-2020, 05:39 PM   #15
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Quote:
Originally Posted by Dirty Rick View Post
I have not had any luck in trying to get any motor to idle at 14.7AFR.

Maybe a newer motor but not a vintage Volvo.

It will surge and likely stall with AFRs that lean.

You can't force it to run that lean, give the motor what it wants. If it's not clean at a "lean best" AFR you have other problems. (Bad convertor?)
My 1971 B20E has an MS2 Extra retrofit using a Yoshifab CAS adapter for crank and cam signals; but, other than a stupid Patriot header is a stock B20E with a D cam. With the target AFR set at 14.7 it idles at a steady 875 RPM without problem. The AFR does bounce around about +/- 0.5 point; but it does not surge or stall. The dash tach says that the idle is rock steady; but, if you look at the Tuner Studio display with the high count tach wheel you can see that the idle is not rock steady. It moves around about +/- 25 RPM.

I don't use idle air control for idle speed control - way too slow. I do use the idle advance feature in MSExtra which helps stabilize the idle speed fluctuations. Prior to implementing idle advance the car would idle fine at 900 RPM and a 14.7 target AFR without stalling. The idle fluctuations were larger.

If you have a camshaft with more overlap than a D cam, then you will be idle challenged.
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Old 10-29-2020, 05:46 PM   #16
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Quote:
Originally Posted by marcusj2001 View Post
I think it help. But when a went for a ride the car ran great but then out of no where it went real fat like from 14.7:1 to 11:1. I think i have some bigger problems then the hot restart now. The only think to get the normal afr back was to lower the ve number. Ve number was 49 and to get the back to normal I hade to lower the ve to 33. I will troubleshoot tomorrow and see what happened. Maybe a stuck injector or something among those lines.

Edit i think it happend when i turned on autotune. That the afr became fat.
Did it go to a really low AFRs and stay there? Then you are correct that you have a new / different problem than your original hot restart problem. If the AFRs went low following the restart; but, then recovered to normal after some running that might be a case that the ASE taper was too long and the engine was recovering from the HIS problem before the ASE taper ran out.

Running autotune should not cause problems unless you have enabled that feature where it implements changes on the go.
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Old 10-29-2020, 06:02 PM   #17
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It when really rich and stayed there I tried restarting and power cycle the ecu to see if it help but no it stayed really rich. So I don’t now what happed. I will look at the tune and compare with and older version. One thing I saw was the rpm gauge was weird the max values was a 100 something but it showed the real rpm of the engine


Edit picture of gauge in the autotune window.
[IMG][/IMG]

Last edited by marcusj2001; 10-29-2020 at 06:24 PM..
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Old 10-29-2020, 08:04 PM   #18
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^^did you do what Kenny suggested?
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Old 10-30-2020, 11:57 AM   #19
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The afr fix itself today don't now why. And i tuned the ase, The taper is set to around 400 and added is set to around 30 now and it help a lot. I think I will increase the added a bit more. Otherwise it's running great. The weird afr can be because a was apparently running out of fuel.
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