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#41
Jim Drago

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Same here. Typically as I'm just about to shift. I've only had my new motor at RA, so hard to say if 2-3 is an issue as well.

Never have seen it, happens too fast imo. I think that is in part why we dont see on dyno 

Going to try 5th as well


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#42
mdavis

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Same here. Typically as I'm just about to shift. I've only had my new motor at RA, so hard to say if 2-3 is an issue as well.

 

 

I had a 2-3 shutoff a bunch at Topeka a few weeks ago (in addition to 3-4).  First time I've had that one.  Solved it by just keeping the car in 3rd!  So we've got that as a solution.


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#43
tylerbrown

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From the three cars I have had this issue with it has only ever happened in 3rd or 4th gear, and above 6100k RPM.

 

One of the cars was always around 61-6200 RPM, and another was always right before you were about to shift at the top of the RPMs.


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#44
JSmart

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Some times as you are making gear change, you go back to a dead pedal. 

 

This is what I experienced at Pitt in Q2. The car pulled hard up to redline in 3rd, I shifted, then had a dead pedal. I blipped the throttle several times and tried the shifter and clutch to no avail. The engine came back on it's own almost exactly 4 seconds later. Here is a data trace of what I experienced:

 

51235732502_d464eaa10a_c.jpg

NB2 Spec Miata engine cut out during 3-4 shift during qualifying 2 at the 2021 Pitt Race Hoosier Super Tour, 05/01/2021. by Jordan Smart, on Flickr

 

Unfortunately I was not logging any ECU data at the time. That will be fixed before the car sees the track again.

 

The issue has not re-appeared since swapping the main injector relay to a brand new OEM part. The car has seen 12 track sessions since.


Edited by JSmart, 06-09-2021 05:36 PM.

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#45
Steve Scheifler

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Jordan, if it had been the main relay, would the data logger have lost power?
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#46
tylerbrown

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This is what I experienced at Pitt in Q2. The car pulled hard up to redline in 3rd, I shifted, then had a dead pedal. I blipped the throttle several times and tried the shifter and clutch to no avail. The engine came back on it's own almost exactly 4 seconds later. Here is a data trace of what I experienced:

 

51235732502_d464eaa10a_c.jpg

NB2 Spec Miata engine cut out during 3-4 shift during qualifying 2 at the 2021 Pitt Race Hoosier Super Tour, 05/01/2021. by Jordan Smart, on Flickr

 

Unfortunately I was not logging any ECU data at the time. That will be fixed before the car sees the track again.

 

The issue has not re-appeared since swapping the main relay to a brand new OEM part. The car has seen 12 track sessions since.

 

From all I have heard as well as experienced myself, the cars usually take somewhere between three and ten seconds to reset itself before the engine is firing again once they've shutoff while having their issue. Our champcar did this exhaustively, and we raced with it for multiple endurance races so I have experienced it many many manyyy times. I have also raced two of our other Spec Miatas while this was happening. You're running up the rpms, all the sudden you lose ignition, the engine is still spinning, gauge cluster still showing rpm and the electronics are all on, just a dead pedal. Then all the sudden it comes back after 3-10 seconds.

 

As far as swapping the main engine relays, my Dad's VVT car randomly eats the main engine relays, but the issue it has with those is the car starts misfiring (not shutting off) and then eventually dies and the engine wont restart. We swap out main engine relays, and its perfectly fine again. When his car had the VVT shutoff issue, changing the main engine relay didn't help it at all during that problem.

 

On two of the other cars that we have had that shutoff issues, changing the main engine relay to an OEM Mazda relay has not stopped the random shutoff issue, and the timing was already at 15 degrees or less. I have heard from others with the VVT shutoff issue too that changing main engine relays did not solve it either.

 

The one car was the VVT champcar, we eventually said screw it and put a megasquirt in it to stop the shutoff issue and it has run perfectly since.

 

The other car we are still having the issue with, we have changed the main engine relay, timing wheel, crank pulley, timing belt tension, crank sensor, and cam sensor, and I took some timing out of it, none of those solved the issue so far.


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#47
Jim Drago

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I put NEW Mazda OEM relay in as well, never fixed this issue for me. 

 

Jim


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#48
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Jordan, if it had been the main relay, would the data logger have lost power?

Injector relay. Green one under the hood. 


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#49
Chris Lefferdink

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From all I have heard as well as experienced myself, the cars usually take somewhere between three and ten seconds to reset itself before the engine is firing again once they've shutoff while having their issue. Our champcar did this exhaustively, and we raced with it for multiple endurance races so I have experienced it many many manyyy times. I have also raced two of our other Spec Miatas while this was happening. You're running up the rpms, all the sudden you lose ignition, the engine is still spinning, gauge cluster still showing rpm and the electronics are all on, just a dead pedal. Then all the sudden it comes back after 3-10 seconds.

 

As far as swapping the main engine relays, my Dad's VVT car randomly eats the main engine relays, but the issue it has with those is the car starts misfiring (not shutting off) and then eventually dies and the engine wont restart. We swap out main engine relays, and its perfectly fine again. When his car had the VVT shutoff issue, changing the main engine relay didn't help it at all during that problem.

 

On two of the other cars that we have had that shutoff issues, changing the main engine relay to an OEM Mazda relay has not stopped the random shutoff issue, and the timing was already at 15 degrees or less. I have heard from others with the VVT shutoff issue too that changing main engine relays did not solve it either.

 

The one car was the VVT champcar, we eventually said screw it and put a megasquirt in it to stop the shutoff issue and it has run perfectly since.

 

The other car we are still having the issue with, we have changed the main engine relay, timing wheel, crank pulley, timing belt tension, crank sensor, and cam sensor, and I took some timing out of it, none of those solved the issue so far.

Time for a Spec ECU!



#50
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For those who have had the issue, is it all years 01- 05 is there any data on that front? I have an 01 and had an engine harness issue years back but otherwise all good for 7 years (I am Knocking on wood as I type)


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#51
Jamz14

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I haven't finished reading this thread and need to drag my ass out of bed to go run a qual race. But quick comment: I'd be much more convinced of any argument for or against if someone would offer putting these things on an engine dyno. Anything other than that is a waste of time effort and money. Chassis (and hub) dynos are not the tools to be using for this or almost anything engine related to our cars. Way to easy to goof the results and some of the things people want to look for are too fine. If we had 800hp mustangs I would feel a bit different. But we have 125hp (130 hp for some). We are looking for 1% differences and a chassis dyno is not the tool to do that imo.
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#52
Steve Scheifler

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I haven't finished reading this thread and need to drag my ass out of bed to go run a qual race. But quick comment: I'd be much more convinced of any argument for or against if someone would offer putting these things on an engine dyno. Anything other than that is a waste of time effort and money. Chassis (and hub) dynos are not the tools to be using for this or almost anything engine related to our cars. Way to easy to goof the results and some of the things people want to look for are too fine. If we had 800hp mustangs I would feel a bit different. But we have 125hp (130 hp for some). We are looking for 1% differences and a chassis dyno is not the tool to do that imo.


I disagree, completely. I absolutely can test to a resolution and level of repeatability to get the job done, quite possibly better than most engine dynos you could get access to. As far as fiddling the results, you either trust the tester or you don’t, anything can be fudged by a knowledgeable person.
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#53
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Maybe you're right Steve. I dont understand how it would be finer than using an engine dyno when you have additional variables in line. But the important statement from me is, "I dont understand". And i have no reason to doubt you. What I do know is that it sometimes appears as if the claims do not match logic or the numbers sometimes generated by chassis dynos.

As far as the tester. I trust the testers. I trust that they are knowledgeable. I trust in human nature. I trust racers to be racers, that includes me. I trust that well intentioned benevolent knowledgeable people often screw up and are generally the source of greater deviation than the instruments they use. I trust that people use data but fail in the analysis and dont achieve knowledge, fail to achieve wisdom and truth.

So maybe I change my position: dynos are great but too often used as a blunt instrument and can be used to mask much.
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#54
Jim Drago

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I haven't finished reading this thread and need to drag my ass out of bed to go run a qual race. But quick comment: I'd be much more convinced of any argument for or against if someone would offer putting these things on an engine dyno. Anything other than that is a waste of time effort and money. Chassis (and hub) dynos are not the tools to be using for this or almost anything engine related to our cars. Way to easy to goof the results and some of the things people want to look for are too fine. If we had 800hp mustangs I would feel a bit different. But we have 125hp (130 hp for some). We are looking for 1% differences and a chassis dyno is not the tool to do that imo.

 

James, 1% is VERY easy to see to those who use chasis dynos regularly and accurately.  FWIW, i offered privately to SCCA tech team and would to for NASA as well, but didnt offer. 

One full day of  dyno time with one of our VVT cars, with an employee for 8 hours, a cut open valve cover with access window and a cam installed they could beat and bang the reluctor wheel all day until they had all the info they needed.  They have not taken me up on it, but glad to do it. No charge at all

 

Furthermore, offered $5,000.00 to any one who is willing to come here and do the same and show ANYTHING outside the noise of the dyno. They could do it on engine dyno as well if they chose.  That stands as well. I would need to be there to over see the testing. 


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#55
Steve Scheifler

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Maybe you're right Steve. I dont understand how it would be finer than using an engine dyno when you have additional variables in line. But the important statement from me is, "I dont understand". And i have no reason to doubt you. What I do know is that it sometimes appears as if the claims do not match logic or the numbers sometimes generated by chassis dynos.

As far as the tester. I trust the testers. I trust that they are knowledgeable. I trust in human nature. I trust racers to be racers, that includes me. I trust that well intentioned benevolent knowledgeable people often screw up and are generally the source of greater deviation than the instruments they use. I trust that people use data but fail in the analysis and dont achieve knowledge, fail to achieve wisdom and truth.

So maybe I change my position: dynos are great but too often used as a blunt instrument and can be used to mask much.



I understand your skepticism but note that I chose my words very carefully. First, I’m assuming a random car is selected and checked for compliance including the ECU etc. We aren’t worried about absolute numbers or comparisons to anything else, the idea being to determine what impact there is from fiddling with the reluctor on an otherwise “legal” car. From there you should have no more honesty concerns with one kind of dyno over another.

Consider what a typical engine dyno really is and how it’s controlled. The basics haven’t changed in decades in large part because simplicity is often a good thing. Most that you are likely to run across are still based on one of a few “water-brake” designs (easily learned about online) that aren’t particularly sophisticated and rely on a metered flow of water through what amounts to an auto-transmission toque converter connected to a strain gauge. If used correctly and meticulously they work very well and provide consistent and repeatable results, never mind absolute accuracy which isn’t relevant to our concerns. Their responsiveness and resolution depend on the speed and accuracy on the control side (water supply rate) and output measuring devices (RPM & torque). I’m sure those have improved over the decades but I’m equally sure there are still a lot of very old systems out there because they are perfectly adequate for most purposes. But don’t assume that they would necessarily meet some imagined gold standard, most are actually rather blunt instruments.

As Jim said, <1% (resolution and repeatability) is not difficult on a good inertia dyno, again, absolute accuracy or comparison to any other being irrelevant. There are a few extra variables to control but that’s simple enough and they are even simpler without reliance on fancy electronic controls or measuring devices; the rest is just math.

The hub type of course is the relative new kid and generations ahead on the control side, with precision devices run by high speed processors capable of simulating complex load scenarios that are produced and monitored in real-time. There are engine dynos with that kind of programmability but not at your average speed shop.

All of the above require monitoring of and correction for (or tight control over) environmental and engine conditions. They should all be instrumented for humidity, barometric pressure and temperature so SAE corrections can be applied, and the temperature should be actual IAT. Newer or updated chassis dynos can take IATs from the OBD or CAN network but also monitor things like coolant and oil temps which might influence what fuel and timing trims are being applied by the ECU at any given moment. How many shops with an engine dyno can do that? Indeed, we can even monitor and log any available ECU data right on the dyno and display them alongside the power and torque graphs. Of course there are engine dynos with similar capabilities but I’m not sure they are the norm yet as they are with chassis dynos. If you have ready access to one then we’ll call that a tie. :)

Anyway, I’m not promoting chassis dynos as the ultimate tool for all purposes. In fact I hope to have a small-engine dyno in the shop before too terribly long because they have clear development benefits. My point is that used correctly a chassis dyno can be more than adequate for high resolution A/B testing.
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#56
Jim Drago

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FWIW,

I have made several changes to the car and heading to the track today and we will see if we made any headway. i am cautiously optimistic, but I have been that way a few times before. I certainly did not go to the Sprints anticipating the problem was not rectified.  I will report back

Jim


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#57
38bfast

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FWIW,

I have made several changes to the car and heading to the track today and we will see if we made any headway. i am cautiously optimistic, but I have been that way a few times before. I certainly did not go to the Sprints anticipating the problem was not rectified.  I will report back

Jim

Several changes might cloud witch one fixes it. But I do know you want your car to run so you're doing everything you can. 


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#58
Jim Drago

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Several changes might cloud witch one fixes it. But I do know you want your car to run so you're doing everything you can. 

Ralph

You are older than me and get confused easier :)  I have very detailed notes and fully intend on a-b-b-a testing if I get anywhere :) 


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#59
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Ralph

You are older than me and get confused easier :)

Golly, this ^ must mean Ralph is over 50 years of age. :rotfl: It's ok guys, getting more mature is positive.


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#60
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Ralph

You are older than me and get confused easier :)  I have very detailed notes and fully intend on a-b-b-a testing if I get anywhere :)

Anyone that is a fan of Abba is showing their age too. 


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