jsplit

Well I blew my motor ( front rotor / housing ) but luckily my rotor decided to eat the broken seal on the first pass...





Just thought it was an interesting image to share...

BuckyFD3

How deep is it??? Not polish it out??

Railgun

Hey man...been a while...

Same thing happened to me a few weeks ago, though not quite as extensive as that. But gouged the housing too.
Don't exactly know what the cause was, but the corner seal on the apex in question was jammed in there pretty well. It's a chicken and egg senario for me I think.

What are your plans for a rebuild?

jsplit

Yeah it's pretty extensive... Did you have the newer 2 piece seals or the 3 piece?

I have no real plans for a rebuild other than to pick up a rotor and housing and get a larger port

GUITARJUNKIE28

when the apex seal jams into the rotor, the metal tweaks, so the corner seal probably just go pinched in the groove. you can verify this by measuring the width of the apex seal groove close to the corner seal. i bet it's too tight.

Railgun

3 piece.



I'll check it out but it's a decoration at this point. Same with it's associated housing.

GUITARJUNKIE28

you wouldn't BELIEVE the kind of stuff people ask me to fix. my policy on fixing stuff like that is an ounce of prevention is worth a pound of cure.

jsplit

yeah well mine was mazda who should have done the prevention as mine was a reman ;p

G's 3rd Gen

iTrader: (11)

Any known reason for the failure? Spike, fuel problem, etc? Do you run a continuos wideband ?..

jsplit

Bad gas / fuel problem possibly based on the increased ethenol in fuel lately.

Long story short, I filled up with gas in the am, cruised around and when I got on boost for the first time that day it hit fuel cut. AFR's were perfect ( yes to your wideband question), wasn't overboosting, etc. I tried to get on it a few more times later in the day and then driving home just cruising on the highway it let out on a downshift from 5th-4th as I was trying to pass a truck :\

t-von

iTrader: (8)

IMO 3 piece apex seals was the worst thing Mazda ever did internally within the engine. The top piece gets so fragile and has so little structural integrity it breaks to damn easliy.

mdpalmer

iTrader: (24)

Damn man, looks a lot like what happened to my front rotor. How many miles did you have on this reman? Have you ever ran the thing lean? Good luck with the rebuild, you have a very positive attitude!

jsplit

This one had maybe 1300 miles on it. Never ran lean, always fully tuned etc.
After a while you have no choice but to have a positive attitude, once you reach a certain number of blown motors it all just becomes comedy.

t-von

iTrader: (8)

So your saying you know the exact condition of your fuel injectors? Perfect tuning never guarantees your engine will never run lean. There's no reason for a low mileage engine to blow unless something else was the cause.

t-von

iTrader: (8)

double post!

FDNewbie

iTrader: (10)

Jon, that's def. an interesting pic. I hope you're gonna be replacing the housings regardless of whether they were gouged...not something you wanna skimp on IMO.

Yea? You'd be the second person locally to have that happen. I have a friend who JUST popped his motor, and he *swears* it's from the ethanol in the gas around here (I think the gas has as much as 10% ethanol now). Either way, sorry to hear it let go

~Ramy

SuIcIdeKiNg-

sorry to get off the topic, But what does ethanol have to do with blowing motors?

Railgun

From what I've read, a 10% mix raises the octane by 3 points.

jsplit

Well I already explained my theory to be bad gas or increased ethenol in the gas in this area.

There's just relaly no other plausible theory in my mind. I had the car tuned maybe 10 days prior and had just gone single so I spent 10 days driving as much as I possibly could, going to the track (drag) etc and essentially just railing on the car every chance I had. The tune was dead on, the car overall was dead on until I put this one tank of gas into the car.

Also, it is relatively easy to know the condition of fuel injectors when they were purchased new or have been recently flow tested. Granted this isn't exact as you mentioned but it's much better than a stab in the dark guess on their condition.

jsplit

This was posted in a NE region thread by MR_rx-t_tt


---

With 10% ethanol blend, running in closed loop at stoich (AFR programmed to 14.7), would display still 1.00 Lambda and 14.7 AFR, because the LM-1 does not magically know what fuel you are using. If you programmed it to 14.1 AFR fuel, it would show 1.00 Lambda and 14.1 AFR.

Widebands (and 5-gas analyzers) do NOT measure some magical AFR. They measure Lamda. There is a second way to calculate Lambda aside from the familiar actual_AFR/stoich_AFR. It's

Lambda = %O2_of_air / (%O2_of_air - %O2_of_exhaust)

This is how a wideband measures Lambda. The term %O2_of_exhaust can go negative if the gas is rich. In that case it means the amount of additional O2 needed to get the gas to stoich.

If you run open loop though and tuned the engine to for example 12.5 AFR (gasoline) and then switched to the ethanol blend, you would run leaner (both in Lambda and AFR) because you need higher fuel flow to compensate for the lower stoich value. If you programmed the LM-1 to 14.1 AFR as stoich, you would then see the correct 12.5 AFR value, but then 12.5 AFR is too lean for the fuel used.

To give an extreme example:
Nitromethane has a stoich value of 1.7. This means for every pound of air entering the engine you need 0.59 pounds for fuel to get to stoich. For gasoline at stoich you need 0.068 pounds of fuel per pound of air. Both values are at Lambda 1.0. If your engine runs max power at 15% rich (Lambda 0.85 or gas AFR 12.5), you could leave the LM-1 at 14.7 gasoline setting and tune to 12.5, irrespective of fuel. That's fine for tuning if you are used to AFR. If, on the other hand, you want to calculate a VE table for the engine, using measured AFR, MAP, displacement, inj. duty cycle and IAT, THEN you need to know the real air-fuel-ratio and stoichiometric value."

If ethanol (stoich AFR of 9) is mixed with gasoline (stoich AFR of 14.7) the resulting gas has a lower stoich AFR than 'pure' gasoline. As the fuel injection is tuned to mix a certain amount of fuel for a given amount of air, the resulting mixture would be leaner when using a fuel with lower stoich AFR.

This can be calculated:

sAFR = (%ofAdditive * sAFRadditive + (90-%ofAdditive) * sAFRgas) /100

where:
sAFR is resulting stoich AFR
%ofAdditive is amount in % of mass of additive (ethanol) mixed in
sAFRadditive is stoich AFR of additive (9 for ethanol)
sAFRgas is stoich AFR of base gasoline (14.7)

For a 10% mixture of ethanol to gasoline by mass the resulting stoich AFR is 14.13

So, for an engine that's tuned to certain AFR at a certain load and RPM on straight gas, the resulting (gasoline equivalent) AFR when running the mixture can be calculated as:

new AFR = tuned gas AFR * (gasoline stoich ratio) / blend stoich ratio

An engine tuned to 12.5 gas AFR will run at the equivalent of 13 gas AFR with a 10% ethanol blend. This is what these people were seeing.

Of course, when running in closed loop, the engine will run at 14.13 AFR instead of 14.7. O2 sensors (incl. widebands) don’t measure AFR, but Lambda. Lambda is defined as actual AFR/stoich AFR. It's a ratio. In closed loop part throttle the engine is just running at Lambda 1.0, regardless of fuel. The same would be true for other Lambda values when running closed loop at WOT using a wideband. The engine would run at the tuned Lambda and everything would be fine. Open loop systems would need to be retuned for alcohol blends though.

The bad news is that WOT fueling in the cars I have knowledge of is a form of open loop so you will be fine driving around day to day but WOT fueling will be effected, this becomes particularly inportant in Forced Induction applications.

FDNewbie

iTrader: (10)

Hmm...I'm lost

afterburn27

iTrader: (5)

So you can reprogram the LM-1 wideband to account for the new 14.13 stoich ratio? I'm pretty sure you can't do that with my Zeitronix. Although you can datalog the lambda values and convert them later in Excel. Interesting stuff though, never crossed my mind.

jsplit

Lol yeah it's quite detailed, I had to read it a good 3 times to make sense of it all...

SuIcIdeKiNg-

So the motor got to much air for the mixture due to the fact that ethanol needs less air. correct?