71 replies to this topic

[Steve Scheifler]

Ron, I’ll let those with 1st hand experience answer but Jim stated above that in his case (which may not be the sane problem as others), he is pretty confident that running the timing wheel in the stock position eliminates the issue whether using a stock or slotted wheel. That sounds a LOT like sync errors but some with the same symptoms have not eliminated it by moving the reluctor wheel (half as much) to offset the crank trigger change. And of course related parts and wiring have been swapped out by multiple people trying to solve this.

[Steve Scheifler]

So is it felt that the lack of freedom to move the reluctor wheel is contributing to misfires? Now that there's a spec for that more cars will not run correctly?

Some are certain of it, others like Jim still haven’t personally seen the problem solved by moving it.

From a great many years of troubleshooting all manner of things I leave open the possibility of at least two different problems, either leading to the same result (like sync errors) or producing very similar symptoms. For example, maybe when Jim’s engine tried to jump through the hood at VIR a harness for the injectors, ignition or a critical sensor was internally compromised. Perhaps it still shows continuity and works most of the time but is less than perfect. ECUs can be finicky, even a dirty/noisy signal can upset them. You might expect it to throw a code particularly if a sensor stops communicating but not everything does, some anomalies just shut it down. In this case Jim has probably bypassed or replaced critical wiring in efforts to isolate the issue, so the “what changed with the crash?” question remains unanswered and maybe a red herring.

[38bfast]

So my theory is its getting a dirty signal to the ECUs. Same issue we have with the 99s but the VVT computer deals with it differently. On our champ car we are only running a Mazda stock crank sensor with a Halltech ECU. We also are running a 36-2 timing plate. The ECU picks up crank errors at about 7200RPM. I used the stock harness and the cam and crank wires are not shielded. Sensor not keeping up? Shielding issue? 

 

Jordans car shut off once in testing at PIT. I tighten up the crank sensor gap to .010" and replaced the green relay and problem went away and went on to win 3 race. Cam plug was replaced when we built the car originally. 

 

Some have fixed the problem by replacing the ECU, Harness, or connectors. 

 

Kill switches have been a issue as well

[Jim Drago]

So is it felt that the lack of freedom to move the reluctor wheel is contributing to misfires?  Now that there's a spec for that more cars will not run correctly?   

 

The spec was intentional tight as SMAC did not want them moved.  As I stated earlier, not sure this is the issue, but if it were..  5 degree advance on the crank would need 2.5 degrees on the cam reluctor, probably 3.0 to be safe, but then again.. if they wanted to allow it to be moved, they would not need a spec as if you go much more it wont run or start.  The spec now is tight enough that if you move it a degree, you may still fail as there was a tolerance when installed by Mazda

[Jim Drago]

 

 

Jordans car shut off once in testing at PIT. I tighten up the crank sensor gap to .010" and replaced the green relay and problem went away and went on to win 3 race. Cam plug was replaced when we built the car originally. 

 

Good, now we know what to protest. the spec is .020-.059! If it doesn't say you can Ralph

[38bfast]

Good, now we know what to protest. the spec is .020-.059! If it doesn't say you can Ralph

yes you can 

[38bfast]

Or another theory is the CAM phaser is not keeping up. Mechanical lag. 

[Steve Scheifler]

Or another theory is the CAM phaser is not keeping up. Mechanical lag.

Possible, but some have replaced the entire VVT mechanism without solving their problem. And from my experience if the mechanism sticks, hangs or stops operating entirely the engine loses power but doesn’t shut down as has been described.

[Jim Drago]

Possible, but some have replaced the entire VVT mechanism without solving their problem. And from my experience if the mechanism sticks, hangs or stops operating entirely the engine loses power but doesn’t shut down as has been described.

I have changed many, never has that fixed a shut off issue. Most of the easy shut off on VVt are crank trigger.  On 99 is cam sensor or wire

JIm

[Tom Sager]

The 36-2 crank wheels seem to be popular among the street car folks.  Any chance that this would provide some benefit in terms of reliability on '96 and newer cars?

[38bfast]

The 36-2 crank wheels seem to be popular among the street car folks.  Any chance that this would provide some benefit in terms of reliability on '96 and newer cars?

the ECU is not programed to work with the 36-2. Thats for the aftermarket ECU gang. 

[38bfast]

Possible, but some have replaced the entire VVT mechanism without solving their problem. And from my experience if the mechanism sticks, hangs or stops operating entirely the engine loses power but doesn’t shut down as has been described.

Thats odd. One would think putting the cam way out of phase it would go to shut off. 

[38bfast]

Getting a oscilloscope on the crank and cam is going to be the next step to see how clean the signal is. Providing the car shuts off in the shop / Dyno. 

[Steve Scheifler]

Thats odd. One would think putting the cam way out of phase it would go to shut off.

It will, that’s a sync error. But I think I see your point, the VVT actuator changes that relationship so if it isn’t moving correctly why isn’t that the same out of sync condition? It implies that ECU knows whether and how much the VVT has rotated, or really it’s absolute position, rather than assuming it is where it should be given the maps. But maybe anywhere in its operating range is acceptable and the shutoff happens only when the reluctor and crank trigger are outside that range.

[chris haldeman]

Getting a oscilloscope on the crank and cam is going to be the next step to see how clean the signal is. Providing the car shuts off in the shop / Dyno.

Car will not shut off on dyno unless extremely out of range and then more likely just won’t start

[Steve Scheifler]

If I had to wager, the engine isn’t at a combination of high load, TP and high RPM long enough for the ECU to give up. You might have better luck at say 75% throttle if that’s sufficient for the full VVT maps to be utilized, but ideally you work with a load bearing dyno so you can simulate track scenarios where it occurs.

Does it ever, or as often, occur in lower gears when the engine spends less time at high RPM? I’m guessing not.

[mdavis]

Does it ever, or as often, occur in lower gears when the engine spends less time at high RPM? I’m guessing not.

 

Not for me.  Always above 6500 rpm regardless of gear.  Comically predictable actually on the same spots on track - see Jim's video from Hallett.

[Steve Scheifler]

Not for me. Always above 6500 rpm regardless of gear. Comically predictable actually on the same spots on track - see Jim's video from Hallett.

So it does occur in lower gears when you are actually at 6500+ only briefly? Then catching on a regular dyno may just require a bit more patience. Assuming we’re talking about the same issue across cars it doesn’t seem likely to be dependent on the additional vibrations from a moving car. You may have the most consistent case at the moment, are you friendly with a local dyno shop?

[Jim Drago]

So it does occur in lower gears when you are actually at 6500+ only briefly? Then catching on a regular dyno may just require a bit more patience. Assuming we’re talking about the same issue across cars it doesn’t seem likely to be dependent on the additional vibrations from a moving car. You may have the most consistent case at the moment, are you friendly with a local dyno shop?

 

I have seen around 6200 up, never below that.  usually approaching 3-4 gear change or 4-5 gear change, some time as you are making gear change, you go back to a dead pedal. 

[Chris Lefferdink]

I have seen around 6200 up, never below that.  usually approaching 3-4 gear change or 4-5 gear change, some time as you are making gear change, you go back to a dead pedal. 

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.