TMIC and bending rods

[rd415]

we have just started our sixth engine with a bend rod (#4 rod) as normal.

Why number 4 - very strange.

[Doug_MPS6]

It took me a little time of thinking that TMIC would be almost as good and that the extra costs (and plumbing) of going to FMIC wasn't likely to be worth it and if it hadn't been for the availability of the CS_Ram Air system and K&N filter setup replacing the TMIC in the stock intake with the FMIC, I may not have made the change.

But I'm glad I did. MATT has covered the reasons why pretty well. The car just breathes and runs so much better. There is a definite boost gain over stock without any other mods. Combined with the 3" Dump pipe it's hard to believe the difference it all makes. Ultimately, it will make working with the Standback tuning flexibility a whole lot better.

As an aside, I like the fact that in the MPS6, the FMIC is almost invisible,unless you look real hard. Q-ships rule!

[Nexus]

If the mzr is do cutting edge, why the problems?

Awnsers in the question - because it's cutting edge.
Consider the same development processes in IT.
The cutting edge code is always the hardest to work with, because there's more "new stuff" to consider and things that are unfamiliar.

---------- Post added at 11:07 PM ---------- Previous post was at 10:47 PM ----------

The benefits of the Dashdaq is access to a whole heap of stuff the Dashhawk can't. I haven't been able to even use most of them...

New Page 1

Nexus: I understand what you're saying about sensor readings to calculate boost since that's how I've had to configure my Dashdaq to show boost. I guess my question is why the sensor readings are different to a gauge plumb directly into the system?

I think there might be a couple of PSI variation depending on how the gauge accounts for barometric pressure. Someone correct me if I'm wrong...

A gauge plumed directly in displaying +/- PSI relative to barometric may assume barometric pressure is 96Kpa or ~15PSI and display relative to that which would mean that in a high pressure weather system near sea level the gauge might consistently show a couple of PSI higher than the values calculated from MAP and Barometric.

Basically barometric will be anything from 90 - 110Kpa depending on altitude and weather etc and a gauge that assumes 96 might show a different reading?

What type of gauge would behave so? I'm not sure. Electronic senders I suspect, because they are more likely to be an absolute pressure sensor, not relative to barometric. A mechanical gauge is probably going to zero at barometric properly. the electronic example would need two sensors to zero properly. One for manifold pressure, and one for barometric.

???

---------- Post added at 11:08 PM ---------- Previous post was at 11:07 PM ----------

?
This thread is a good read...Why rod#4 is probably the most relevant question to the topic?

[rd415]

Awnsers in the question - because it's cutting edge.
Consider the same development processes in IT.
The cutting edge code is always the hardest to work with, because there's more "new stuff" to consider and things that are unfamiliar.

---------- Post added at 11:07 PM ---------- Previous post was at 10:47 PM ----------



I think there might be a couple of PSI variation depending on how the gauge accounts for barometric pressure. Someone correct me if I'm wrong...

A gauge plumed directly in displaying +/- PSI relative to barometric may assume barometric pressure is 96Kpa or ~15PSI and display relative to that which would mean that in a high pressure weather system near sea level the gauge might consistently show a couple of PSI higher than the values calculated from MAP and Barometric.

Basically barometric will be anything from 90 - 110Kpa depending on altitude and weather etc and a gauge that assumes 96 might show a different reading?

What type of gauge would behave so? I'm not sure. Electronic senders I suspect, because they are more likely to be an absolute pressure sensor, not relative to barometric. A mechanical gauge is probably going to zero at barometric properly. the electronic example would need two sensors to zero properly. One for manifold pressure, and one for barometric.

???

---------- Post added at 11:08 PM ---------- Previous post was at 11:07 PM ----------

?
This thread is a good read...Why rod#4 is probably the most relevant question to the topic?

Nice comment, but simplified in the Automotive World there are two pressures

1. Gauge Pressure - the zero on gauge = 14.7 pounds per sq inch or 101.3 kpa which is air pressure at sea level

2. Absolute Pressure - the zero is actual zero - this means that the gauge will read 101.3 kpa at seal level - only reading zero in a vacuum or outer space.

In the auto industry it would be confusing to use absolute pressure. Imagine picking up a tyre pressure gauge reading 15 pounds before putting it on a tyre or an oil pressure gauge reading 15 pound before even starting the engine. I don't believe any automotive instruments would use Absolute Pressure.

Still want an answer why number 4 ???
Does it have something to do with Harmonics (two different source vibrations produced at the same time). If it is harmonics it should be overcome in the design.

[Nuliaj]

It's not always number 4, there have been other cases of 3 or 1, not sure if I've read about 2. No one knows why number 4, otherwise it would've been addressed by now.

[rd415]

we have just started our sixth engine with a bend rod (#4 rod) as normal.
Plus we have supplied other ten rebuild kits off the top of my head.
So I would say its common.

This is where the idea of always No. 4 came from and in another post MPSgarage state that there are only two reasons
1. out of tune
2. Too high Pressure in Number 4.

I am intrigued at the "conclusions drawn game". I know I have been drawn to a conclusion on a mechanical fault, only after deeper investigation found the problem something completely different from my original conclusion.
Here is an example:- I had a brand new police XU1 Torana come into the workshop with a flat battery, after a quick battery test it was found the alternator was not charging. On removing the alternator I found part of No.1 conrod stuck in the side of the alternator and a big hole in the side of the block.

Is there any documented proof of the bent rods?
Is there any concrete evidence of the actual cause?

Or is it just wishful thinking by the owners to blame the engine and not their right foot.

[Nexus]

Just to show off : This is what I did with a DashXL layout
The vac/boost in PSI is calculated from MAP and barometric. In order to use the same needle to indicate both the manifold absolute pressure and vac/boost, I made the green +/- PSI ticks rotate around the axis so that 0 PSI is always indicating barometric, and replaced the 100Kpa text with the Barometric reading.

Gauge pressure would recalculate this display for PSI presuming 101.3Kpa.

You know the only thing this has to do with bending rods that I can think of is PSI.



If anyone wonders how I could have boost temps of 35 with intake temps at 52, well that display is because I when I first started logging them I didn't understand that the BAT sensor I was reading reports inversely and relative to the IAT. so 52-35+52 = 69 actual boost temp.

Different software probably hides some of these things - does dashhawk make you write scripts to process readings like this, or you just buy a PID pack that includes all of that for your vehicle?

Nice comment, but simplified in the Automotive World there are two pressures

1. Gauge Pressure - the zero on gauge = 14.7 pounds per sq inch or 101.3 kpa which is air pressure at sea level

2. Absolute Pressure - the zero is actual zero - this means that the gauge will read 101.3 kpa at seal level - only reading zero in a vacuum or outer space.

In the auto industry it would be confusing to use absolute pressure. Imagine picking up a tyre pressure gauge reading 15 pounds before putting it on a tyre or an oil pressure gauge reading 15 pound before even starting the engine. I don't believe any automotive instruments would use Absolute Pressure.

[duglet]

[YOUTUBE]Pvi02xesIMM[/YOUTUBE]

Happy Motoring
duglet

[Nuliaj]

If anyone wonders how I could have boost temps of 35 with intake temps at 52, well that display is because I when I first started logging them I didn't understand that the BAT sensor I was reading reports inversely and relative to the IAT. so 52-35+52 = 69 actual boost temp.

This would explain why when I switched to dashdaq my BAT were much higher than when I had a dashhawk.

[kmh001]

Do you know which rod Dug?

[kagerou]

Just to show off : This is what I did with a DashXL layout

oh my, what did you use to capture all that data and display it? i need one of those things!!

[2XS]

Do you know which rod Dug?

My reading experiences would say number 4

[kmh001]

It's common for #4 to fail, but the other rods do fail also.

Here's an example of a broken #3 from a 3MPS.


The thing that bothers me the most is that the vast majority of DISI failures I have read about reportedly occurred with little or no load on the engine. Now that's bizarre because physical failures can't really occur without some stress-inducing load. Scan the various Mazda forums around the world that talk about blown engines and the word that seems to occur most frequently is 'highway'. If you haven't seen them already, these quotes are typical of what people say:

"I was 1 block away from Cobb, turning onto their street when it happened. I was accelerating in 2nd gear just getting ready to shift to 3rd, boost was around 2 or 3 psi, and it happened somewhere between 3500 and 4000 rpm."

"A couple days ago after a rather low key 10 mile trip on the highway, I was coasting at about 60 mph and THUNK! "

"Instant failure with no load on the engine and I had been driving conservatively the whole day actually, it was kind of busy on the highway and we had wet roads, was in no hurry and while coasting at 60 mph, WHAM! Just like that."

At one stage there was a paranoid thread on a US forum about not using cruise control because it created the conditions that most commonly caused engine failure.

Why do so many engines die after being operated at high vehicle speed/low engine rpm? Except for some harmonic feed back, the physical components of the engine don't know the difference between 3000rpm in 3rd or 3000rpm in 6th. But the ECU does know the difference.

The ECU has full control of inlet cam timing, ignition, fuel pressure, injector opening etc etc etc. In the old days you had to abuse an engine to make it fail. But these days a dodgy bit of code can conceivably create a cylinder over-pressure condition.

And from the whacky things I have seen my engine do there is definitely dodgy code in there.

[duglet]

I guess im lucky then....

Most of my 116000kms are highway kms and i use my c/control all the time.

Oh well...i guess i have a good ECU.

Happy Motoring
duglet

[Nuliaj]

My bet is on ignition timing. Drive around at cruising speeds long enough and timing goes stupidly high and you start to get more KR. Whether or not it's real knock is another question, but running that hot cannot be good for the engine.

[kmh001]

Same here, lots of highway driving with cruise control and lots of timing advance noticed also. I've had the death rattles a few times with the smoke cloud, usually with cruise active, but always hoped that with a stock engine it would be survivable.

[rd415]

Interesting idea of the timing, but I believe it is co-incidental with an aready damaged rod.

There seems no accurate correlation between the timing and the engine rpm. At least not in all the reports I have read. If it was a combination of something in the computer eg engine rpm & over advance timing it would show up as common occurence in all broken rods. In essence there would be closer links between the breaks.

I am starting to think it is caused by a stretched rod. Stretched so often by high rpm that it has lost it's elasticity.

I have seen plenty of axles break at what is literally low speed take-off, upon inspection the the splines looked like a corkscrew just at the break. I kept a few as demo's to show the students how badly an axle can wind up before breaking, quite incredible to think that a solid piece of metal will wind up like an elastic band.

The trouble is you never get to measure them before they break, would be interesting to measure the rods on a rebuild that doesn't have a broken rod.

Just had a thought - twigged by a previous post and that was "Engine Temp". In lean burn mode if the temp starts to rise dramatically the computer advances the timing dramatically to cool the combustion temperature. If the knock sensor detects detonation it retards the timing instantly. 6th gear long haul under load at low rpm is the perfect scenario for high combustion temperatures and the possibility of detonation and a broken rod - maybe?????

[Doug_MPS6]

RD415. You're right. I broke four rear axles in my old series 2 Landrover, which was so noted for it I carried spares and could change them inside 30 minutes. But I never broke one at high load on a steep rock face when the car weighed around 2-3 tonnes or storming up a sand-dune. All of them died soundlessly on a quiet drive in the suburbs. They died from the accumulated stress that one could observe in the metal crystallinity and fabric.

Incidentally, 6th is a very tall gear and we've seen posts here from people that run quite high loads at low engine speeds, including one guy who had not had a turbo before writing in wondering why he got smoke and rattling when he floored it in 6th at 1500rpm!!