Worried about Knock

[bigdaddy]

So lately I have been reading up on the topic of engine knock, and I'm starting to worry. I go WOT on the highway fairly often when Im in 6th at like 2800 rpms, and sometimes less rpms. I sometimes feel a little stutter right before it builds boost and I take off. I think this might be the "hesitation" that is spoken of with the stock plugs, but I just wanted some opinions. I will stop doing so, but is it bad to have the car in 6th at like 1500 rpms, just cruising, no WOT?

[Darth Vader]

It's certainly bad to get on it at 1500 rpm at any time, that's seriously lugging the engine and stressing majorly the rotating assembly. 2800 rpm? Well, I don't hammer it under 3000 myself. Low-load cruising is fine, though I wouldn't just jump on the car after a particularly protracted spell of it as the cylinder head temps will be really high at that point.

[RuZec]

yes. I heard that flooring it while you in low rpms and in 6th gear is bad.. like the OP mentioned you putting a lot of stress on the engine.

[bigdaddy]

yeah. I will stop doing it as of now. I just didn't know that it was hard on my engine

[Darth Vader]

Nothing harder, save completely uncontrolled combustion and, even that is usually momentary. Lugging is long, protracted crushing force on the pistons, rods, piston pins, and crank. It's the most damaging thing you can do in the course of normal driving. Engines like ours let you do it because we have a pinner turbo and alot of static compression = massive low end torque.

[Saskatchewan17]

But if you are cruising at a low RPM, but not putting barely any load on the engine, is that still bad? Say barely tapping the gas when cruising in 6th at 45 MPH.

I mean I do this often, I just ALWAYS ALWAYS ALWAYS downshift before passing, going uphill, downshifting to a light/for a turn. I never-ever go WOT below 3k RPM.

And how is it a good thing for an engine to always have it cruise at 3500 rpm or even more? I would think that is more taxing on an engine to keep the pistons/crank and whatnot rotating at such a high rate all the time.

[Darth Vader]

No, that's not bad. It's putting high load on the engine at low rpm that's bad.

...and keeping an engine at higher revs IS NOT bad for it. You have to understand the physics involved. It's kind of like cheating in the gym by lifting fast. You can pump out alot of reps before fatigue but, if you take it slow, you have to strain alot harder and will fatigue faster. Your thoughts are a common misconception of how engines work.

Like I said before though, you shouldn't jump on the gas on any engine after PROLONGED cruise, as the engine timing has been retarded for a long time, mixtures are around stoich (~14.5:1 air/fuel) and combustion chamber temps are sky-high.

I believe this engine's tendency is to run pretty high combustion chamber temps normally, as this reduces emissions and boosts fuel economy. The back blade of this strategy is outlined above.

[tunersteve]

I have a few questions for the OP/anyone who seems to be experiencing 'knock'

-when you are seeing knock, is the car hesitating/bucking?
-what are you using to see this?
-have you tried letting the knock cure itself?

If you're seeing spikes randomly, let the car run itself and adjust accordingly. You should see a decrease in the random spikes by doing so. I was getting spikes of 7-8 on my DH, on light cruise during warm up on the freeway, now I rarely see anything. As long as the knock isn't audible or pulling fuel/hesitating, you don't need to be freaking out.

[bigdaddy]

i did do WOT a decent amount below 3K, and now im freaking out. I have only had my car for 6K miles, and I have stopped doing this, but do you think it has done permanent damage to my motor?

[3speedy]

You should be fine don't worry about it.

[Darth Vader]

i did do WOT a decent amount below 3K, and now im freaking out. I have only had my car for 6K miles, and I have stopped doing this, but do you think it has done permanent damage to my motor?

First question is, why? The motor makes a whack more torque at 3k than 2K. As long as you weren't going WOT in higher gears at 2k I wouldn't be too concerned. The mechanical advantage of the lower gears eases the load on the motor.

Anyway, anything is possible but, there ain't much you can do about it if you have hurt it. You can find out, if you're really concerned, by running a leakdown test on all four cylinders. If you've hurt one, it'll likely be the rod that's hurt and the cylinder will leak like an SOB past the rings if the rod's tweaked.

[Saskatchewan17]

I think you would notice if the engine was badly damaged.

[bykeryder4life]

OP if you are worried you are gonna blow your motor and you have knock, you need to change your driving style. Driving around you should stay in vacuum, drive like a granny. if you need to accelerate downshift(you got six gears for a reason) and ease on the gas after to avoid part throttle boosting. If you are gonna boost, it's all or nothing- none of this half pedal low ass rpm shit. you need to have it around 3k rpm and give it full. You cant be boosting and still have the car in closed loop operation its certain fail...

[Saskatchewan17]

?
You can't give the car 5psi when at 3,000 RPM?

[Darth Vader]

C'mon, Bykeryder, stop spreading panic and dissent. You can most certainly boost this car and run it like any other car. You can most certainly use lower than max boost and lower than max load without blowing up. It's just common sense not to lug the engine, like I described earlier but, other than that, you can drive it like you want.



I think you would notice if the engine was badly damaged.

On a less cheery note: You might not. a tweaked rod, for example, can go unnoticed until it decides it's had enough non-linear motion and fails. I've dismantled running engines that had 7 of 8 rods tweaked, had cracks in every rocker arm, cams ground flat, etc. that were reported to have been running well and "just broke".

[bigdaddy]

C'mon, Bykeryder, stop spreading panic and dissent. You can most certainly boost this car and run it like any other car. You can most certainly use lower than max boost and lower than max load without blowing up. It's just common sense not to lug the engine, like I described earlier but, other than that, you can drive it like you want.




On a less cheery note: You might not. a tweaked rod, for example, can go unnoticed until it decides it's had enough non-linear motion and fails. I've dismantled running engines that had 7 of 8 rods tweaked, had cracks in every rocker arm, cams ground flat, etc. that were reported to have been running well and "just broke".

what can I do to run this test? Take it to Mazda?

[Darth Vader]

No, any regular car shop can do it for you, with no risk or perception issues if modded.

[bykeryder4life]

.

[bykeryder4life]

?
You can't give the car 5psi when at 3,000 RPM?

Yes you can, but dont do it part throttle. you gotta get on it enough to make the open loop transition or else your car will be at 5psi running fuckin 14.7 afr's with a shit ton of timing (thats closed loop operation basically). go ahead and do it, im not saying you will blow but its certainly putting stress on your motor thats not needed.


C'mon, Bykeryder, stop spreading panic and dissent. You can most certainly boost this car and run it like any other car. You can most certainly use lower than max boost and lower than max load without blowing up. It's just common sense not to lug the engine, like I described earlier but, other than that, you can drive it like you want.

Yeah you can use low boost and low load, but again, its all about the open/closed loop thing. If you dont give it ENOUGH load or boost or whatever triggers the car to make the switch to open loop, you will be running in boost with a lean afr and high timing advance designed for fuel economy and emissions driving around town. If you own a DH, watch the lower right corner of it. driving around it should have a "C" in the corner, which is closed loop. when it goes to "O" you are in open loop. An "L" means open loop due to engine load. theres even one more i forgot that means open loop with engine failure-limp mode basically.

[Saskatchewan17]

Ok, I sort of understand... but don't at the same time (as in I understand the closed/open system concept). I understand what you're getting at byker... it's just sort of hard for me to grasp that you have to use your gas petal and turbo as an on off switch. Surely the car can be boosted saftley at less than max psi and under lower revs (say 3,000 rpm...)? I don't think the car should be driven like an on/off switch. The car has to be tuned from the factory to be able to handle low boost at lowish rpm or low boost at high rpm.

[coyfish]

Just stay out of boost when DD'ing. Thats what I do.

[matsuda]

Yes you can, but dont do it part throttle. you gotta get on it enough to make the open loop transition or else your car will be at 5psi running fuckin 14.7 afr's with a shit ton of timing (thats closed loop operation basically). go ahead and do it, im not saying you will blow but its certainly putting stress on your motor thats not needed.

What???

The MS3 has a wideband primary O2 sensor.
Closed loop does not equal stoich.

Anyone with a DH (or equivalent) probably already knows this.

[matsuda]

Surely the car can be boosted saftley at less than max psi and under lower revs (say 3,000 rpm...)?

Yes, of course it can.

Those who believe otherwise (implying that Mazda engineers are total morons) should sell their car immediately.

[Saskatchewan17]

That's what I thought...

[08cosmic3]

I never go WOT below 3500 rpm.

[bigdaddy]

dudes, stop listening to byker or whatever, this is getting a bit ridiculous. The point is, dont go WOT in high gear at low RPM's, and dont attempt to put large amount of load on the engine. You can essentially feel when you are loading the engine, just be careful. Its not like our car is in a special category of cars. Just drive it carefully, maintain it, and stop worrying so much. I get OCD about stuff like this, but this is beginning to seem dumb. This is why I shouldn't be on the forums, it makes my hyper-paranoid...

[Saskatchewan17]

it makes my hyper-paranoid...

Same here. Everytime someone posts about any problem I think "Holy shit that is going to happen to me!"
Hah.

[tunersteve]

Too many people think they fully understand the vehicle, and not enough have a clue.

Hate to say it, but this thread is full of nonsense.

[Saskatchewan17]

All these differing opinions makes it really hard to know what is correct and what is not.


But I think we can all agree that you shouldn't boost and load the engine up too much in the lower rpm range.

[bigdaddy]

All these differing opinions makes it really hard to know what is correct and what is not.


But I think we can all agree that you shouldn't boost and load the engine up too much in the lower rpm range.

fair enough

[bigdaddy]

Too many people think they fully understand the vehicle, and not enough have a clue.

Hate to say it, but this thread is full of nonsense.

directed at me, or byker?

[bykeryder4life]

What???

The MS3 has a wideband primary O2 sensor.
Closed loop does not equal stoich.

Anyone with a DH (or equivalent) probably already knows this.

closed loop has an afr TARGET of stoich. if it strays off target then your fuel trims take it into account and do whats needed to bring it back close to stoich. Yes the MS3 has a wideband primary O2 sensor, I read off it with my DH. And last I checked, closed loop = stoich for a complete burn and good emissions. thats why you are cruising around town and idling right around stoich. Anyone with a DH knows that, you dont idle at 12.0 and cruise around in the 11's afr....

As for the whole open loop/ closed loop on/off switch thing, you guys are freaking out over nothing. Im not saying you blow motors doing part throttle boosting but its putting alot of strain on your engine when you do. That, along with the engineering/design problems this platform has makes for zoom zoom boom.

I learned all this open/closed loop driving shit from Laloosh, and old ms3 owner. If you think Im wrong, ask him, I dare you. he knows his shit. he will say the same. drive either in vacuum or in full boost if you are worried about blowing your shit because PT boost isnt good on this car.
what the fuck do I know though I've only driven around fully bolted for 30k on my own tune

[onelsono]

OP, dnt wory about ur car. just dont do anymore of that 6th gear low rpm wot pulls. thats terrible for the car. if u wanna be safe, dont hit boost when ur daily driving.

idk if this is correct or not, but i herd that u shouldnt do any half throttle pulls b/c considering the turbo is so small it will be at almost full boost and ur afr is still in the 13-14's.. makes sense to me but thats just wut ive herd.

[hugador]

No half throttle pulls while daily driving? pffft good luck with that.

[matsuda]

closed loop has an afr TARGET of stoich. if it strays off target then your fuel trims take it into account and do whats needed to bring it back close to stoich. Yes the MS3 has a wideband primary O2 sensor, I read off it with my DH. And last I checked, closed loop = stoich for a complete burn and good emissions. thats why you are cruising around town and idling right around stoich. Anyone with a DH knows that, you dont idle at 12.0 and cruise around in the 11's afr....

Of course the AFR is stoich during idle or cruise.

However, closed loop on the MS3 does not have a fixed AFR target of stoich (that obviously wouldn't make sense).

Since you have a DH, you (or anyone else with a DH) can easily confirm this.

Log AFR (commanded and/or actual) and open/closed loop and try a variety of different engine loads.

[onelsono]

No half throttle pulls while daily driving? pffft good luck with that.

(scratch).... y should any1 have luck with that, i do it everyday.

[GoFast]

well this is turning into a "chicken little said the sky is falling" thread now isn't it?

[tunersteve]

I see this thread having little value.

[onelsono]

lol

[hugador]

(scratch).... y should any1 have luck with that, i do it everyday.

Exactly, it's impossible not to.

[onelsono]

Exactly, it's impossible not to.

sry but ur not making sense. im telling you that i drive everyday w/o doing any of those half throttle pulls, i simply dont hit boost. and ur saying its imposible, it really isnt impossible. theirs no need to hit boost when ur daily driving imo..

[onelsono]

I have a few questions for the OP/anyone who seems to be experiencing 'knock'

-when you are seeing knock, is the car hesitating/bucking?
-what are you using to see this?
-have you tried letting the knock cure itself?

If you're seeing spikes randomly, let the car run itself and adjust accordingly. You should see a decrease in the random spikes by doing so. I was getting spikes of 7-8 on my DH, on light cruise during warm up on the freeway, now I rarely see anything. As long as the knock isn't audible or pulling fuel/hesitating, you don't need to be freaking out.

from ur post it seems like ud no the answer to this.. isnt true that if your device shows you a knock but you dont feel any hesitation or anything at all that it could be just a false knock read? i just did a 2nd-5th gr pull in my car 5min ago and my DH tld me i had a knock of 3.0 in the middle of 4th. but the car didnt hesitate at all or nuthing it just kept going, wuts ur say on this? mind you that this was live data not a log.

sry for the TJ...

[hugador]

sry but ur not making sense. im telling you that i drive everyday w/o doing any of those half throttle pulls, i simply dont hit boost. and ur saying its imposible, it really isnt impossible. theirs no need to hit boost when ur daily driving imo..

But then you say you do it everyday. You and others are making it sound like half throttle pulls is bad for the car but I don't think so. So if I want to hit boost I should step on it if not I shouldn't hit boost at all. I think that's ridiculous.

[tunersteve]

I have yet to see any correlation between partial boosting and blown motors/knock.

As I've said before, you're car is going to adjust KR no matter what you do. Regardless of tune, driving conditions, or engine speed, the car has to actively adjust for a variety of factors. Octane, altitude, engine load, A/F, etc. all will cause slight adjustments in ECU timing/ignition. If you don't believe me, drive your car normally and monitor KR, then do the same without monitoring for a week. I would be willing to bet that ignorance is bliss in most cases.

If you have a tune on the car, then setting up some warning if you get extreme knock is a precautionary measure, and something I'd recommend. I've done a test to see if part throttle KR on the highway was something that the ECU could compensate, and indeed it will. I moved my KR warning up to 10, since if things are that high, I'd be willing to bet that it's audible.

[onelsono]

But then you say you do it everyday. You and others are making it sound like half throttle pulls is bad for the car but I don't think so. So if I want to hit boost I should step on it if not I shouldn't hit boost at all. I think that's ridiculous.

r u ok bro? im telling you i NEVER DO HALF THROTLE PULLS. I DONT HIT BOOST WHEN DD. what dont you understand.

[onelsono]

I have yet to see any correlation between partial boosting and blown motors/knock.

As I've said before, you're car is going to adjust KR no matter what you do. Regardless of tune, driving conditions, or engine speed, the car has to actively adjust for a variety of factors. Octane, altitude, engine load, A/F, etc. all will cause slight adjustments in ECU timing/ignition. If you don't believe me, drive your car normally and monitor KR, then do the same without monitoring for a week. I would be willing to bet that ignorance is bliss in most cases.

If you have a tune on the car, then setting up some warning if you get extreme knock is a precautionary measure, and something I'd recommend. I've done a test to see if part throttle KR on the highway was something that the ECU could compensate, and indeed it will. I moved my KR warning up to 10, since if things are that high, I'd be willing to bet that it's audible.

yea, i got the warning on my DH also. but i feel like if you had knock up to 10 ur motor would just pop, lol is that not crazy high, if my car does hit knock its usually .7 max

[hugador]

r u ok bro? im telling you " I " NEVER DO HALF THROTLE PULLS. I DONT HIT BOOST WHEN DD. what dont you understand.

From your post, I understand you now. I din't meant to push your button.

[tunersteve]

yea, i got the warning on my DH also. but i feel like if you had knock up to 10 ur motor would just pop, lol is that not crazy high, if my car does hit knock its usually .7 max

I've seen partial KR while cruising on the freeway of 8 or more. It'll spike, then drop off and never do a thing. I've also tried going WOT when this happens, and KR goes to zero and doesn't come back.

Speaking with and hearing from MNAO techs, they've also acknowledged that some knock is acceptable and inevitable. Also, from what I understand, the car will adjusts up to 6 degrees before pulling fuel. I haven't confirmed that yet though.

[onelsono]

I've seen partial KR while cruising on the freeway of 8 or more. It'll spike, then drop off and never do a thing. I've also tried going WOT when this happens, and KR goes to zero and doesn't come back.

Speaking with and hearing from MNAO techs, they've also acknowledged that some knock is acceptable and inevitable. Also, from what I understand, the car will adjusts up to 6 degrees before pulling fuel. I haven't confirmed that yet though.

i c

[matsuda]

i just did a 2nd-5th gr pull in my car 5min ago and my DH tld me i had a knock of 3.0 in the middle of 4th. but the car didnt hesitate at all or nuthing it just kept going, wuts ur say on this?

The timing was retarded and you lost a few HP.
It isn't anything that you are likely to notice.

[onelsono]

The timing was retarded and you lost a few HP.
It isn't anything that you are likely to notice.

sumthing to wory about?

[tunersteve]

sumthing to wory about?

Nah, just the ECU doing its thing.

[onelsono]

gotchya

[turbos3]

just wasted 20 minutes reading this thread. (deadhorsei

[cudaman]

I've compiled a list of threads on this forum to help resolve at least some of the issues. Run a search for more data pertinent to the subject if you are worried about PTB and the connecting rods, or concerned about running high boost at low RPMs over the long run. This came from other posts on this forum, not by myself. I do happen to own an MS3 and a Neon SRT-4, and the first guy is right. At low RPMs neither and EVO or SRT-4 produce as much torque (stock-for-stock) at low rpms as does an MS3. MS3 is stock-for-stock and price a much better car than an unmodified SRT-4 but the SRT-4 engine internals are practically bullet proof. I am waiting to see if the stock MS3 internals can hold up over time the same way....Take it for what it's worth.

Excerpts:

some Mazdaspeed3s seem to be having issues with too much torque at low RPM snapping connecting rods. This is a very good dissertation of how it's all happening and why too much torque at low RPM with HIGH boost can take inherent weaknesses and make them slowly but surely weaken the rod until it snaps... sending rod shrapnel through the block. they like to call it the zoom-zoom-boom club. Not funny if you are affected. Seems to happen to stock MS3's that have impurities in the rods, and (of course), those boosting too high at low RPMs, giving massive amounts of torque that the rod can't handle over time..... They even mention SRT4s. The MS3 does produce a lot of torque at low RPM and they (even stock) have a very grippy "on/off" clutch that would further exacerbate the problem of torque delivery and lots of engine load when the torque spikes with the whipsaw clutch action. Some good reading here. At least it make sense to me....

http://www.mazdas247.com/forum/showthre ... 035&page=3


Excerpt:

I have looked a lot at these blown engine issues. In the end it was all under our noses. The rods are plenty strong for this application and I have compared them dimensionally to both EVO X and SRT4 rods. They are no lighter and although the bolts are a mm smaller in diameter, the DISI engine was not designed for high RPM and we are not breaking rod bolts. I have looked at binding issues, hydrolock etc ... nothing was concrete.

So then I looked at the rod construction and noticed the small end is tapered. Interesting. Diesel engines taper the small end so that the bearing surface is lower so that the rod takes a high load. The rod I have seems to have some good wear on the bottom of the bearing caused by cylinder pressure. Interesting. Perhaps poor oiling. Perhaps too much pressure.



I then looked at how similar cars produced power and as it turns out no EVO or SRT4 motor makes as much torque as we do at such low RPM. Period.

The way this Mazda is calibrated is more like a truck than a performance car. We don't need more than 300 ft lbs of torque to make well over 400whp but Mazda didn't want that for this motor.

Everyone has been looking at hp gains for this car and have completely ignored the torque and where it is at its maximum and that it doesn't carry into the RPM band.

Further torque is the one that is DIRECTLY proportional to cylinder pressure.

Case and point, look at the tq and hp on this 450whp evo


Now look at Darksun's dyno. Again look at the torque he made.


Take a look at this recent DISI dyno. 375 ft lbs at 3000 RPM.
http://**************************/foru...ue-maf-cal.jpg

Cylinder pressure is what causes the "force" that is then back calculated as torque by a dyno. The gases that cause the cylinder pressure as a result of combustion expand at the same rate no matter how quickly you engine is spinning. This is the reason that you advance spark timing - so that the flame front occurs at the appropriate time to provide as much force to the downward moving piston as possible.

Now, as RPM rises, the piston moves much faster. So then amount of TIME it is subject to the pressure of the expanding gases is less per each power stroke. The reason cars make torque during a certain part of the RPM band is because there is a relationship between how you can control the burn rate (which depends on air/gas inflow, mixing, lighting mixture) with respect to piston speed

So when you are making 300ft lbs of torque at 2500 RPM, the motor sustains the force required to makes that torque for longer each power stroke than if you made the torque at 4500 RPM. Let's not even talk about the fact that a dyno takes an average force applied which favors high RPM to low RPM. It's pretty damn hard to make the torque we do at such a low RPM. The principle is similar to lugging.

So our engines making 300 ft lbs of torque at 2500RPM and only 280whp are under a lot more mechanical stress than an F/I honda motor making 300 ftlbs of torque at 5000RPM and 400whp at 7500RPM.

Once RPM increases too much, inertial loads of the rod and piston break rod bolts. The counterpart is extreme torque at low RPM. Oil pushed out of bearings and extreme connecting rod loads are the result. This load applied again and again eventually results in bent rods and holes through blocks.

Once you open up the flow path to this car it makes MUCH more torque at an even lower RPM instead of breathing better at higher RPMs.

Have you seen the rods on a diesel? Here is an example of a TDI (yes diesel) dyno. Look familiar?



Here is an example of a 1.9 TDI rod and piston that makes 170 ft lbs of torque and 100hp from the factory. The rods are bombproof compared to us because THEY WERE DESIGNED to take high torque at low RPM.




Nuff said. I don't think anyone should be wondering why we break rods anymore.

Solution? There are many factors that affect how an engine produces torque and power. In order for the stock bottom end to stay in one piece, change the stock tune so that you don't hit 21psi at 2800 RPM. Help the motor breathe and move the torque curve further in RPM. Not only will the engine survive longer, but it will also make more whp. And everyone will be a hero, not just whoosh, who certainly didn't make the power he did by chance.

EDIT: This is an addition further explaining the low load rod breaking phenomenon:

I know that people are concerned with the part throttle blow-ups. These are certainly explainable - and I think the short article below from Hot Rod magazine clearly explains how fatigue and material impurity can lead to brittle fractures when components are under high stress. Brittle fractures start at a point of imperfection or impurity in the metal and propagate through. This is why some guys last longer stock and some don't. When a brittle fracture starts to happen, you won't feel anything until that fracture has grown enough to cause the rod to snap. The fracture will most likely let go under vacuum or when engine RPM changes (gear changes) since the rod is being "pulled apart" at that point if you will.

Cylinder pressure, high RPM, etc all play a part in exploiting a material flaw if it exists in the first place and bring it out of the wood work faster.

If you look at MS3 rods, you clearly see that the surface finish is not smooth (machined) like it is in aftermarket forged rods.


Stock Forged Steel

Original-equipment forged steel rods are the next step up the strength and reliability ladder. Detroit-sourced OE-forged rods begin life as bars of carbon steel that are passed through a rolling die. The rolling process compacts the molecular structure and establishes a uniform, longitudinal grain flow. The bars are then heated to a plasticized state, inserted into a female die, and pressed into the near-final shape while a punch locates and knocks out the big end bore. In doing this, the grain flow at the big end is redirected in a circular pattern, like wood fibers surrounding a knot, and excellent compressive/tensile strength results. Finally the rod is put through a trimmer (that leaves the characteristic thick parting line on the beam), the big end is severed and machined to create the cap, bolt surfaces are spot-faced, then final machining and sizing take place.

But there are some drawbacks. When the forging hammer hits the hot bar, heat transfers from the bar to the hammer causing a phenomenon called de-carb (decarburization). Here, trace amounts of the carbon in the steel migrate to the surface resulting in a rough finish full of what metalurgists call “inclusions.” An inclusion is described as anything that interrupts the surface of the metal, or a lack of cleanliness (impurities) in the material. The effect of a surface inclusion can be likened to a nick in a coat hanger. Bend it enough times and the wire will fail, usually right at the nick. The rough surface caused by de-carb affects the surface to a depth of 0.005 to 0.030 inch and is packed with inclusions that are a breeding ground for cracks. The old hot rodder’s trick of grinding and polishing the beams is a valid solution to this problem, though far too labor-intensive to ever be considered by Detroit.

When it comes to inclusions caused by impurities, Detroit’s need to control costs can result in purchases of bulk steel that may (or may not) contain contaminants such as silicon that are not detected during manufacture. Such impurities can interrupt the grain boundaries between the parent molecules and lead to a fracture minutes or years after the rod is first installed in an engine. It’s a matter of luck and what kind of abuse the flawed rod is subjected to.

Stock forged steel rods are an economical choice that should be able to handle one horsepower per cubic inch with quality fasteners, and as much as twice the factory-rated output if the beams are polished.

Comment:

Excellent analysis, Russm. I've followed this "small end rod taper" issue on another forum and am glad to see the discussion coming here.

There are many reasons to believe that this taper does produce much higher levels of torque induced stress at low rpm, where torque is applied at its greatest strength when coming on boost and where exposure to the force is longest due to the low rpm.

Your suggestion that some low end torque should be tuned out of the car at low rpm makes sense. I'm thinking that one way Mazda could do that in the future (besides ECU remapping) would be by modified camshaft lobe profile and in remapping the variable valve timing, which could keep torque down at low rpm, even if boost were raised.

I think this issue may be why boost creep or raising boost levels above stock levels may be poison to these engines at light throttle and low rpm settings.

Just thinking out loud without giving it a lot of analysis.

I wonder if the short term lesson band aid in this for us is to remember to keep rpm up a bit by staying in a lower gear than we might otherwise when we are coming up on boost. That way we are at least keeping the engine closer to 3500 rpm rather than 2800 when we roll onto boost where boost pressure and torque are both at their highest. It's not a fix, but it might be good to think this way when we drive.

In short don't lug the damn engine and don't drive around at the typical 2500-2700 just off boost rpm and roll into boost. Downshift first, then bring in the boost

[bykeryder4life]

lol be careful man, apparently part throttle boosting doesnt matter on this engine. you may get flamed by noobs haha