Nissan SR20 CAS - Dropping RPM

General support questions and announcements for MS3. See also MS3 manuals.

Moderators: jsmcortina, muythaibxr

Post Reply
shaodome
Master MS/Extra'er
Posts: 741
Joined: Thu Aug 26, 2004 1:58 pm

Nissan SR20 CAS - Dropping RPM

Post by shaodome »

So this is on a slightly older alpha code (RC3). I know that firmware works as I've done a few other SR20s with the exact same setup and they have no issue on it.

This car has sync loss hard around 5500/6000RPM which is worse with higher load. Sync loss reason 65.

This is the stock ignition system which has a running dwell of 1.9ms. I've tried a spark duration of 0.1-1.5ms, same behavior. The standard log just shows the sync loss and nothing else out of the norm, but the composite log is VERY weird. The cam signal is missing most of the time even though the car is running. I think the sync loss is even too fast for the composite logger to grab it.

If I turn on the noise filtering for "CAM" the car will never sync. Noise filtering works on the "crank" section. Pots were configured as per the optispark settings.

Any ideas on things to check?
shaodome
Master MS/Extra'er
Posts: 741
Joined: Thu Aug 26, 2004 1:58 pm

Re: Nissan SR20 CAS - Dropping RPM

Post by shaodome »

datalog, MSQ and composite log attached
shaodome
Master MS/Extra'er
Posts: 741
Joined: Thu Aug 26, 2004 1:58 pm

Re: Nissan SR20 CAS - Dropping RPM

Post by shaodome »

as you can see the composite log makes no sense.....could it even run if that was correct.
jsmcortina
Site Admin
Posts: 39585
Joined: Mon May 03, 2004 1:34 am
Location: Birmingham, UK
Contact:

Re: Nissan SR20 CAS - Dropping RPM

Post by jsmcortina »

shaodome wrote:as you can see the composite log makes no sense.....could it even run if that was correct.
The data in the comp log appears ok, but the rendering of it in MLV doesn't.

James
I can repair or upgrade Megasquirts in UK. http://www.jamesmurrayengineering.co.uk

My Success story: http://www.msextra.com/forums/viewtopic ... 04&t=34277
MSEXTRA documentation at: http://www.msextra.com/doc/index.html
New users, please read the "Forum Help Page".
shaodome
Master MS/Extra'er
Posts: 741
Joined: Thu Aug 26, 2004 1:58 pm

Re: Nissan SR20 CAS - Dropping RPM

Post by shaodome »

jsmcortina wrote:
shaodome wrote:as you can see the composite log makes no sense.....could it even run if that was correct.
The data in the comp log appears ok, but the rendering of it in MLV doesn't.

James
Do you see the sync loss in the comp log?
jsmcortina
Site Admin
Posts: 39585
Joined: Mon May 03, 2004 1:34 am
Location: Birmingham, UK
Contact:

Re: Nissan SR20 CAS - Dropping RPM

Post by jsmcortina »

I'm not seeing any there, could you try the sync-error logger?

Have you been able to run SR20 successfully before? I'm a little confused by your posts?
(Also, RC3 is 'Release Candidate', not 'alpha' but that's just semantics.)

What Release codes have you tested and do they work for you?

James
I can repair or upgrade Megasquirts in UK. http://www.jamesmurrayengineering.co.uk

My Success story: http://www.msextra.com/forums/viewtopic ... 04&t=34277
MSEXTRA documentation at: http://www.msextra.com/doc/index.html
New users, please read the "Forum Help Page".
shaodome
Master MS/Extra'er
Posts: 741
Joined: Thu Aug 26, 2004 1:58 pm

Re: Nissan SR20 CAS - Dropping RPM

Post by shaodome »

jsmcortina wrote:I'm not seeing any there, could you try the sync-error logger?

Have you been able to run SR20 successfully before? I'm a little confused by your posts?
(Also, RC3 is 'Release Candidate', not 'alpha' but that's just semantics.)

What Release codes have you tested and do they work for you?

James
Sorry for the confusion. I rolled back to this specific code as it was a known working variant for me. I've used it on several SRs making anywhere from 300whp-650whp. So I don't think it's a code related issue, but I'm out of options I know of to try. I haven't tried a release code yet.

If you look at the regular log you can see the RPM drop to zero.

Is there any way you can see if it is the high-res or low res signal that has the problem?
jsmcortina
Site Admin
Posts: 39585
Joined: Mon May 03, 2004 1:34 am
Location: Birmingham, UK
Contact:

Re: Nissan SR20 CAS - Dropping RPM

Post by jsmcortina »

shaodome wrote: So I don't think it's a code related issue
OK, good.
Is there any way you can see if it is the high-res or low res signal that has the problem?
Try the sync-error logger.

James
I can repair or upgrade Megasquirts in UK. http://www.jamesmurrayengineering.co.uk

My Success story: http://www.msextra.com/forums/viewtopic ... 04&t=34277
MSEXTRA documentation at: http://www.msextra.com/doc/index.html
New users, please read the "Forum Help Page".
shaodome
Master MS/Extra'er
Posts: 741
Joined: Thu Aug 26, 2004 1:58 pm

Re: Nissan SR20 CAS - Dropping RPM

Post by shaodome »

The visual render of the sync error log also looks very weird at best.

I fixed it by changing out the NGK BKR7E plugs for a set of NGK iridiums and the RPM drop out disappeared. The exchange was now a slight miss around 3000rpm @ 100ish kpa and again at 6000RPM under any higher load. Did it at 240kp as well has 170kpa in the same exact RPM spot.

I've seen behavior like this before from SR20DET engines on megasquirt. It is ignition related for sure. The running dwell on these coils is 1.9ms but I tried everything between 1.5 and 3ms. Same miss in the SAME spots. Car ran through these areas on the OEM ECU with zero issue.

I'm just going to ditch these coils in favor of Toyota 1zz coils that work great and don't give off as much EMF.
shaodome
Master MS/Extra'er
Posts: 741
Joined: Thu Aug 26, 2004 1:58 pm

Re: Nissan SR20 CAS - Dropping RPM

Post by shaodome »

I just wanted to update this thread.

I've now installed MS3 on two other SR20 motors and they all exhibited the same strange misfire around 3000rpm under load. They are all using 1zz toyota coils (new oem). They also started to experience spark blow out around 350whp+ Under lower power amounts the car revs PERFECTLY to redline.

In my testing here are the things done:

1. swap coils for known good ones (litteraly made 750whp on the coils tuning the car prior to one of the SRs, talking like 1 hour apart)
2. change to all sort of spark plugs
3. rewire the coils indpendent of the OEM harness to ensure solid grounds and power supply.
4. Tried a large range of coil dwell
5. Last ecu firmware tried (and still in the car) was 1.3 Alpha 10.
6. Verified timing against the crank marks with a timing light using a spark plug wire between the coil and the plug for the signal source for the light.

As far as the logging is concerned the sync loss counter is at ZERO and the composite log doesn't show the 3000rpm misfire or the (as expected the high rpm blowout). I was at a loss so I tried the DIYAutotune trigger disc which emulates a 12+1 wheel with cam for full sequential. All I changed was the disc and put in the proper settings for tooth logger, dialed in the angle and off I went. The 3000 rpm misfire was gone as well any spark blow out.

That leads me to believe some weirdness is happening in the Nissan SR20 mode in regards to the spark outputs and/or coil dwell?
shaodome
Master MS/Extra'er
Posts: 741
Joined: Thu Aug 26, 2004 1:58 pm

Re: Nissan SR20 CAS - Dropping RPM

Post by shaodome »

bump...james?

Anybody else having success making good power on the SR20 decoder?
Matt Cramer
Super MS/Extra'er
Posts: 17499
Joined: Thu Apr 16, 2009 8:08 pm

Re: Nissan SR20 CAS - Dropping RPM

Post by Matt Cramer »

I can't answer the question directly, but I do have a note about the decoder: It only uses the high res wheel at low RPM such as for cranking. So at 3000 RPM, it will be less accurate than our trigger disc. Not sure if that's a factor here or not.
Matt Cramer -1966 Dodge Dart slant six running on MS3X
shaodome
Master MS/Extra'er
Posts: 741
Joined: Thu Aug 26, 2004 1:58 pm

Re: Nissan SR20 CAS - Dropping RPM

Post by shaodome »

Matt Cramer wrote:I can't answer the question directly, but I do have a note about the decoder: It only uses the high res wheel at low RPM such as for cranking. So at 3000 RPM, it will be less accurate than our trigger disc. Not sure if that's a factor here or not.
I'm not sure if that's a factor or not either, but I don't think so and here's why.

When I shoot the crank with a timing light and the SR20 decoder is in use, I can hold the timing exactly where I command it all the way to redline. It doesn't waiver at all, which is why I started to think more towards spark energy (dwell) than actual timing being weird.
shaodome
Master MS/Extra'er
Posts: 741
Joined: Thu Aug 26, 2004 1:58 pm

Re: Nissan SR20 CAS - Dropping RPM

Post by shaodome »

Nobody else experienced issues with this?
Subaru_EA82_4EAT_AWD
Helpful MS/Extra'er
Posts: 114
Joined: Fri Jan 24, 2014 4:52 pm
Location: Australia

Re: Nissan SR20 CAS - Dropping RPM

Post by Subaru_EA82_4EAT_AWD »

I am sorry to butt-in here, but can someone elaborate on the MS use of the Hi-res wheel? I am very interested in this for an install of mine and cant find much info on it, is there a thread someone can point me to, please?
Want a neat way to Check & Set Ignition timing AND CRANK the motor at the same time BY YOURSELF?
A little thing I made up... https://youtu.be/PajlPNF5mmQ
cukali
Experienced MS/Extra'er
Posts: 196
Joined: Tue Jun 08, 2010 8:59 pm

Re: Nissan SR20 CAS - Dropping RPM

Post by cukali »

shaodome wrote:Nobody else experienced issues with this?

Yes. On three seperate KA24DE's. But I couldnt get it to work with my stock CAS HR.

If you are using the CAS wheel upgrade, you will see the the trailing edge lands at the same trailing edge of the crank. I am not an expert on this, but I for the life of me could not get the skips out. It may be many different causes...internal to the CAS itself picking up light from each other (AEM suggested that), or with the MS3. I also hooked up a AEM EMS4 stand alone to one of the vehicles and it could not run at all without missing in several spots repeatedly. Although AEM EMS4 is a very buggy ECU thats so sensitive to any type of interference its miserable to install at times.

'What I did is prevent the trailing edges from accurring at the same time....I made my cam trigger on rising and crank on falling. Not the greatest cure, but it did make a difference. Also, make sure you have the 1k pullup reistors installed in MS3 case or at the CAS.

Eventually, I bought this one.... http://www.carid.com/1993-nissan-altima ... 41332.html

As you can see it doesnt have edges accurring simultaneuosly. This solved my problems for the AEM EMS4 and the MS2 with sequential.

Tweak your VR resitors some also if you have the signal that way.

Again, not sure if this is the cause of your problem, but I had the exact same thing happening to me. Drove me mad I couldnt use my COP and sequential. Also, I used the opto circuit so that may point to the CAS wheel itself or Nissan parts.

Update: Just noticed you ARE using the STOCK CAS. ouch!
shaodome
Master MS/Extra'er
Posts: 741
Joined: Thu Aug 26, 2004 1:58 pm

Re: Nissan SR20 CAS - Dropping RPM

Post by shaodome »

See that's the thing....I'm thinking something is up with the decoder and the dwell calculations. The car has no sync loss at all according to the composite logger/tuner studio gauges. All the cars experienced the same miss around 3000 rpm and then had spark blowout issues at higher RPM/higher boost. Seemed to be around 350whp the problem developed. Didn't matter what ignition coils we used. All I did was switch to a wheel similar to what you posted and disabled the NISSAN CAS wheel decoder for the more traditional dual wheel setup and problem went away immediately. Didn't change the dwell, dwell bat correction, ignition hardware, or the plug gap.
mobbarley
MS/Extra Newbie
Posts: 1
Joined: Fri May 09, 2014 9:03 pm

Re: Nissan SR20 CAS - Dropping RPM

Post by mobbarley »

So should the stock SR20det (S14a) cam wheel be avoided with MS3-Pro?

Looking for an honest opinion here as I am about to start wiring up my car - I much prefer that than wasting paid time on a dyno!
slyrye
Experienced MS/Extra'er
Posts: 255
Joined: Sun Aug 12, 2007 2:41 pm
Location: Philippines
Contact:

Re: Nissan SR20 CAS - Dropping RPM

Post by slyrye »

I can make you a breakout board decoder for your setup complete with Hall and Optical-sensor conditioner I used on my SR20DET setups, it has it's own processor "PIC" microcontroller for decoding! so it's basically a wire and play setup no need to change CAS wheels..! :D :D and if you run into misfires it's probably your ignition, getting blew out, I suggest a 12v trigger voltage using "emitter-follower" npn transistor triggering...! I've had so much success I highly recommend it...!
MSnS'n'4G15
jsmcortina
Site Admin
Posts: 39585
Joined: Mon May 03, 2004 1:34 am
Location: Birmingham, UK
Contact:

Re: Nissan SR20 CAS - Dropping RPM

Post by jsmcortina »

There seem to be lots of different reports going on here.

Posting about MS2 in a topic about MS3 Nissan CAS isn't necessarily helpful. Megasquirt-2 cannot decode the hi-res Nissan pattern at all. Megasquirt-3 (and MS3-Pro) can decode the hi-res pattern. The hi-res teeth are used for more accurate timing during cranking.

As far as the developers are aware, the Nissan CAS modes work correctly. If you have an actual problem, please start a new topic with details of the install, MSQ, datalog and any other supporting data.

James
I can repair or upgrade Megasquirts in UK. http://www.jamesmurrayengineering.co.uk

My Success story: http://www.msextra.com/forums/viewtopic ... 04&t=34277
MSEXTRA documentation at: http://www.msextra.com/doc/index.html
New users, please read the "Forum Help Page".
Post Reply