Regret removing the OMP?
#26
gross polluter
iTrader: (2)
There aren't really any great reasons to remove an OMP, but there area lots of good reasons to keep it whether you modify it for fresh oil or keep it stock drawing from the oil pan.
My REPU has no OMP because it was a real pain to tray and make it work with the mixture of engine parts I have and my carb. I had several setups for OMP in there and each time it was a leaky mess. I really hate that it doesn't have one. If you want to premix go ahead and do it even with the OMP, but sometimes you really don't want to have to pull out the funnel and oil then have to clean up your mess and keep that messy stuff in your car, or maybe you just forget one time. Do you want that one day to be the end of your motor?
My REPU has no OMP because it was a real pain to tray and make it work with the mixture of engine parts I have and my carb. I had several setups for OMP in there and each time it was a leaky mess. I really hate that it doesn't have one. If you want to premix go ahead and do it even with the OMP, but sometimes you really don't want to have to pull out the funnel and oil then have to clean up your mess and keep that messy stuff in your car, or maybe you just forget one time. Do you want that one day to be the end of your motor?
#28
Senior Member
iTrader: (10)
0% duty on deceleration?
Maybe I'm just ignorant, but the engine runs because it is getting a mixture of air, fuel, and heat (spark). If it ceased to squirt ALL fuel on deceleration the the motor would cut off, would it not? The throttle regulates the air charge and fuel is added based on the map sensor readings, engine load, and rpm. Not the 'gas' pedal (air pedal?)
#29
Urban Combat Vet
iTrader: (16)
My PFC Commander reads zero injector duty-cycle during off-throttle decel. When I lift my foot, it goes to zero. Not a tuner, but there maybe a way to play with that with a datalogger..I'm not sure. Regardless, very little or no fuel, very little or no lubrication...and frequently at relatively high rpm and for relatively long periods with just pre-mix.
#30
~17 MPG
iTrader: (2)
Maybe I'm just ignorant, but the engine runs because it is getting a mixture of air, fuel, and heat (spark). If it ceased to squirt ALL fuel on deceleration the the motor would cut off, would it not? The throttle regulates the air charge and fuel is added based on the map sensor readings, engine load, and rpm. Not the 'gas' pedal (air pedal?)
If you have entirely too much time, get an ECU that will cut fuel or spark when the engine runs too lean, then configure it in such a way that will trigger that fuel cut without hurting the engine (for instance, set the target fuel ratio to something unrealistically rich). When the ECU decides the mixture is not rich enough, it will cut fuel or turn on a low-RPM rev limit to protect the engine, and you'll end up with the fuel injectors turned off when the throttle is fully open. The engine will still coast down to a stop, but the sound will be even quieter and it will not decelerate as quickly without the vacuum that would have been present with a closed throttle. Probably best not to do this often, but it's entertaining and a good way to double-check that the failsafe functions as intended.
#32
~17 MPG
iTrader: (2)
Regarding the OMP, if you're making much more power than the stock ECU could support, you might be running more fuel than the maximum output of the OMP... I measured it once and saw maximum of ~4.3 volts at 11psi with stock a nearly-stock engine: aftermarket downpipe but stock exhaust and intake. My take on that is there's not much headroom, unless they were injecting more oil than needed for stock power levels.
Pouring 2-stroke premix is a mess but seems unavoidable if you're running E85 even near stock power levels. I've been looking for some sort of large plastic syringe to suck premix out of the container and push it into the fuel tank. I'm told large syringes exist for farm use, but haven't yet found a clear one that will hold as much fluid as I'd like.
Pouring 2-stroke premix is a mess but seems unavoidable if you're running E85 even near stock power levels. I've been looking for some sort of large plastic syringe to suck premix out of the container and push it into the fuel tank. I'm told large syringes exist for farm use, but haven't yet found a clear one that will hold as much fluid as I'd like.
#33
talking head
4.3 volts is only a vague appreciation of where the position sender has sat on a s5 or FD engine
and is not in any way an output to the pump
the number you see is also subject to a ground offset when you measure without earthing to the ecu earth point
and the oil output from one engine to another when returning 4.3 volts can be different
as the body of the position sensor is fine tuned at the factory by displacing it back with small shims
the EOMP itself works by action of a 5/6 wire stepper motor ( 4 channels and two power )
which variably depresses a plunger,, which in effect is the inlet valve to the mechanical pump that is turning with engine speed
removing the ECU control will just "park" the plunger at one setting,, and the OMP part will still work with engine speed but at a fixed inlet flow
it is a simple matter to displace with a spacer between the stepper output rod and the plunger for more flow everywhere
or to take the shims out ( or add them in ) and make the pump move either less everywhere,, or more
by this design,, there is more left in the pump than many of you can achieve
and there is scope for the user to add a physical offset trim to his need
also will point out that FC s5 ( 4 outlets ).. FD rx7 ( 2 outlets ) and 20 B ( three outlets )
all use exactly the same pump .. with only the final tapping of the holes for banjos makes them any different from each other
note that a 20b and an FD engine has significantly more stock HP than the FC
and from that then you should see what the pump is capable of keeping up with
but yes., once you go through to silly HP.. it pays to add something extra to the tank . to be sure
and if you have custom mapping for your OMP..
to push it to max flow ( 5 V return ) once you have gone beyond stock boost ( or earlier for aftermarket seals )
and dont pull any out unless you have an octane related knock
to be sure, to be sure
edit .. note that the rx8 changes things a little,, and only seems to use the position sensor for a switch at either limits,, and instead "counts" the number of full winds it orders the stepper plunger to
it also only seems to do the self check immediately after startup
and so mazda made moves to improve the redundancy of the pump ,, where silly flags before caused warrantee issues
( EG ..engine code and limp )
for what may have been fleeting errors or a bad wipe of the return sensor rheostat
as such,, have seen the "jason dixon eomp controller" operating just fine ( in rx8 mode )
on s5 eomps that had previously produced codes and limps from bad wiper when on stock vehicles
and is not in any way an output to the pump
the number you see is also subject to a ground offset when you measure without earthing to the ecu earth point
and the oil output from one engine to another when returning 4.3 volts can be different
as the body of the position sensor is fine tuned at the factory by displacing it back with small shims
the EOMP itself works by action of a 5/6 wire stepper motor ( 4 channels and two power )
which variably depresses a plunger,, which in effect is the inlet valve to the mechanical pump that is turning with engine speed
removing the ECU control will just "park" the plunger at one setting,, and the OMP part will still work with engine speed but at a fixed inlet flow
it is a simple matter to displace with a spacer between the stepper output rod and the plunger for more flow everywhere
or to take the shims out ( or add them in ) and make the pump move either less everywhere,, or more
by this design,, there is more left in the pump than many of you can achieve
and there is scope for the user to add a physical offset trim to his need
also will point out that FC s5 ( 4 outlets ).. FD rx7 ( 2 outlets ) and 20 B ( three outlets )
all use exactly the same pump .. with only the final tapping of the holes for banjos makes them any different from each other
note that a 20b and an FD engine has significantly more stock HP than the FC
and from that then you should see what the pump is capable of keeping up with
but yes., once you go through to silly HP.. it pays to add something extra to the tank . to be sure
and if you have custom mapping for your OMP..
to push it to max flow ( 5 V return ) once you have gone beyond stock boost ( or earlier for aftermarket seals )
and dont pull any out unless you have an octane related knock
to be sure, to be sure
edit .. note that the rx8 changes things a little,, and only seems to use the position sensor for a switch at either limits,, and instead "counts" the number of full winds it orders the stepper plunger to
it also only seems to do the self check immediately after startup
and so mazda made moves to improve the redundancy of the pump ,, where silly flags before caused warrantee issues
( EG ..engine code and limp )
for what may have been fleeting errors or a bad wipe of the return sensor rheostat
as such,, have seen the "jason dixon eomp controller" operating just fine ( in rx8 mode )
on s5 eomps that had previously produced codes and limps from bad wiper when on stock vehicles
Last edited by bumpstart; 10-21-14 at 02:05 AM.
#35
rotorhead
iTrader: (3)
Maybe I'm just ignorant, but the engine runs because it is getting a mixture of air, fuel, and heat (spark). If it ceased to squirt ALL fuel on deceleration the the motor would cut off, would it not? The throttle regulates the air charge and fuel is added based on the map sensor readings, engine load, and rpm. Not the 'gas' pedal (air pedal?)
Once engine speed falls low enough, the fuel will inject again and the spark will fire again, so combustion resumes and the engine generates torque to overcome friction and propel the vehicle forward.
#36
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pretty bloody simple.. in 1971 mazda fed the OMP into the carb bowl
essentially premixing
they soon changed that
evolved to carb throats ( SD 12a )
evolved to housing direct and inlet runner ( 13b RESI / GSLE and s4/ s5 FC
evolved then to only housing direct ( FD )
evolved to housing direct , with rubber inserts and lower flow ( later FD )
evolved to housing direct,, but at the edges ( rx8 s1 ) , got lots of warrantee issues
evolved that to housing direct edges and middle ( later rx8 )
i hope you are seeing the pattern in this
the middle direct housing spot is where the motor needs the lube
premixing just blankets the entire rotor .. in all the spots it doesnt need it
and only a very small part of it is going to land in the hot spot in middle of the apex seal where you want it most
so what does all this extra premix and wasted oil do?
it turns to carbon and acetelene compounds when not completely combusted
what is already in your combustion chamber ? carbon and grit
so this pre mix oil magically stays wipe **** clean when it goes into the motor?
i pull plenty of engines down .. guess where the clean strip is on engines that run the OMP
-right down the middle of the rotor -
guess this OMP isnt so bad for carbon build up
.. and it is the oil distributed elsewhere,, and residual petrol from running too rich far too long that makes engines carbonised
so.. this premix.. tell me about its magical qualities again? how it makes the motor somehow cleaner,, but when i pull them down,, they are often worse?
how many premix motors made 250 000 km ?? ...not many... i bet
ask yourself why mazda moved away from bowl mixing into the fuel
.. i can think of a few good reasons that are still valid in todays cars , and one of them is octane
the other is continued lube when the motor is in decel
every time it revs up.. it has to rev down .. am i missing something or are you ?
if you have 300 rwhp,, then you need to keep the OMP ( more than ever before ) and add suplement premix as at those flows you may be dropping below the optimum ratio as determined by mazda in the SAE papers
PS
some of you need to change your oil more often
.. cant imagine the engine running very long on the carbonised and gritty engine oil that you seem to wish to avoid injecting for OMP
PS.. i run LPG.. with OMP .. my engines and rotors and turbos are SPOTLESS, and have posted many pics to prove it
OMP is not contributing greatly to the carbon build up .. but the lack of petrol is certainly helping keep it very clean
essentially premixing
they soon changed that
evolved to carb throats ( SD 12a )
evolved to housing direct and inlet runner ( 13b RESI / GSLE and s4/ s5 FC
evolved then to only housing direct ( FD )
evolved to housing direct , with rubber inserts and lower flow ( later FD )
evolved to housing direct,, but at the edges ( rx8 s1 ) , got lots of warrantee issues
evolved that to housing direct edges and middle ( later rx8 )
i hope you are seeing the pattern in this
the middle direct housing spot is where the motor needs the lube
premixing just blankets the entire rotor .. in all the spots it doesnt need it
and only a very small part of it is going to land in the hot spot in middle of the apex seal where you want it most
so what does all this extra premix and wasted oil do?
it turns to carbon and acetelene compounds when not completely combusted
what is already in your combustion chamber ? carbon and grit
so this pre mix oil magically stays wipe **** clean when it goes into the motor?
i pull plenty of engines down .. guess where the clean strip is on engines that run the OMP
-right down the middle of the rotor -
guess this OMP isnt so bad for carbon build up
.. and it is the oil distributed elsewhere,, and residual petrol from running too rich far too long that makes engines carbonised
so.. this premix.. tell me about its magical qualities again? how it makes the motor somehow cleaner,, but when i pull them down,, they are often worse?
how many premix motors made 250 000 km ?? ...not many... i bet
ask yourself why mazda moved away from bowl mixing into the fuel
.. i can think of a few good reasons that are still valid in todays cars , and one of them is octane
the other is continued lube when the motor is in decel
every time it revs up.. it has to rev down .. am i missing something or are you ?
if you have 300 rwhp,, then you need to keep the OMP ( more than ever before ) and add suplement premix as at those flows you may be dropping below the optimum ratio as determined by mazda in the SAE papers
PS
some of you need to change your oil more often
.. cant imagine the engine running very long on the carbonised and gritty engine oil that you seem to wish to avoid injecting for OMP
PS.. i run LPG.. with OMP .. my engines and rotors and turbos are SPOTLESS, and have posted many pics to prove it
OMP is not contributing greatly to the carbon build up .. but the lack of petrol is certainly helping keep it very clean
#38
Senior Member
iTrader: (10)
Emissions
Mazda has had a tough time keeping rotaries emissions compliant. Couldn't that have a lot to do with the changes in the OMP system? Perhaps it had something to do with everything bumpstart said, or perhaps it has to do almost entirely with pandering to ignorant customers and strict emissions laws and Mazda had to design a system that would appease both. I imagine that in that attempt they would be creating an oiling system that used the minimum amount of oil needed to get by, still maintain a lengthy engine life, be easy for customers to use.
#39
Senior Member
iTrader: (4)
So the real solution to this premix/omp debate basically still stands at
1-grab an adapter
2-make/get and external tank and run lines to omp adapter
3-add premix into tank for the omp to inject clean oil for lubrication instead of carbon/dirty engine oil
Problem solved...unless I'm missing something
1-grab an adapter
2-make/get and external tank and run lines to omp adapter
3-add premix into tank for the omp to inject clean oil for lubrication instead of carbon/dirty engine oil
Problem solved...unless I'm missing something
#41
Searching for 10th's
iTrader: (11)
I removed the OMP a couple years ago and do not regret it.
My FD is race only though, and premixing is no big deal.
If it were a street car I would have just fixed all the leaky stuff.
As it is a race car, and every winter something new leaks, I just blocked them off and premix.
The OMP not working properly was a bit of a worry, so less things to leak, one less thing to break my car.
My FD is race only though, and premixing is no big deal.
If it were a street car I would have just fixed all the leaky stuff.
As it is a race car, and every winter something new leaks, I just blocked them off and premix.
The OMP not working properly was a bit of a worry, so less things to leak, one less thing to break my car.
#44
packin' heat
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The 0% duty cycle on decel was enough to convince me to keep mine. I had a PFC and you can watch the injectors go to 0% when in decel, then once you get down to an rpm where you are no longer compression braking, the injectors turn back on. I kept mine, but I also have an Adaptronic ECU which allows control of the OMP. So I dialed back the amount of oil injected and use premix.
#45
F'n Newbie...
iTrader: (6)
The 0% duty cycle on decel was enough to convince me to keep mine. I had a PFC and you can watch the injectors go to 0% when in decel, then once you get down to an rpm where you are no longer compression braking, the injectors turn back on. I kept mine, but I also have an Adaptronic ECU which allows control of the OMP. So I dialed back the amount of oil injected and use premix.
#46
~17 MPG
iTrader: (2)
I'd be interested to hear more about this, fendamonky. I've only spent a little time running without decel cut because I was told it helps assist tuning the very low-throttle sections of the map. With the injectors off (decel cut active), the car feels and sounds smooth when coasting down... with the injectors on (decel cut disabled) the car bucks, burbles, and generally feels & sounds rough.
As soon as I was happy with the car's transition from decel cut to light-load fueling I re-enabled decel cut and never looked back. I'd be interested to hear if others found some combination of AFR, timing, and (whatever else is a factor... trailing split? injection angle? idle position?) that would help.
As soon as I was happy with the car's transition from decel cut to light-load fueling I re-enabled decel cut and never looked back. I'd be interested to hear if others found some combination of AFR, timing, and (whatever else is a factor... trailing split? injection angle? idle position?) that would help.
#47
F'n Newbie...
iTrader: (6)
I'm no tuner, so I can't really go into the "how" of it. I just recall that mine didn't cut fuel, nor did it have noticeable issues with driveability.
That was 2 years ago, running a PFC.
That was 2 years ago, running a PFC.
#48
All out Track Freak!
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Yep you can still spray a little fuel on decel with a PFC
For those interested I have an OMP (approx 62k miles taken off of a mostly stock 94 touring) in good shape with SS lines (the good ones with rubber coating on the outside)
$125 shipped
For those interested I have an OMP (approx 62k miles taken off of a mostly stock 94 touring) in good shape with SS lines (the good ones with rubber coating on the outside)
$125 shipped
#49
Rotary Enthusiast
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Hi everyone,
I'll chime in. I have been reading the forums and replying for some time. I modified my car with some of the knowledge I have gained through this forum and some from my experience and knowledge as an engineer, and I am not a design type engineer.
I went with an external tank and OMP with some premix. I think Mazda engineers knew what they were doing and strategically located the OMP injectors in that location for a reason and I run 2-cycle oil through the OMP. I also pre-mix a little due to running more WHP and ensuring that enough oil gets injected into the engine. Now ensuring how much and exact amounts is a debate, but I do .5 to 1oz premix with a working OMP. I am at 380-400WHP.
So I think lubricant is very important and I spent a lot of time thinking about the options and weighing them against each other.
Then on to what can possibly kill an engine. Most engines need rebuilds due to coolant seals, fuel delivery problems, overboost, or carbon'd up.
Coolant seals are damaged from heat cycling out or age. Ensure water temps and oil temps are in check and replace with viton seals. done.
Fuel delivery problems, keep the fuel filter clean, use the car on a regular basis, use stock parts were can (hardlines, etc), replace with a stock denso supra pump for reliability. Check system on a regular basis.
Overboost can happen from a line cracking going to the wastegate or something with a boost controller failing. Best option would be to go off spring pressure on a wastegate. If something fails like a vacuum line, ensure you have enough fuel to run the engine in an overboost state. But now you need to worry about detonation.
Carbon. probably from running rich. most speculated on that here. I run a healthy idle at 12.6-12.7 AFR to catch the idle from decel. This is needed because the engine does cut fuel when cruising off throttle. The powerFC adds fuel back in depending on when the tuner says to add it back in. Most tunes I have seen add fuel back in around 1100-1250 rpms. otherwise fuel is cut.
Water injection/methanol - This helps remove carbon from the engine/seals/etc. It also removes heat from the combustion chamber and increases the octane (when using meth). If tuned to say 14PSI where the car can run without water meth (safe tune), and you add a water rich, slight meth mix, it removes the carbon from the engine, prevent engine detonation, can save you on a fuel delivery problem (maybe), and protects against a possible overboost scenario.
I do everything above on mine. I would also run stock seals for the best housing to seal interface with lots of design R&D behind them with predictable manufacturing processes/quality control. My car does have super seals in it from the previous owner, and will run till I need a rebuild and replace with stock seals.
And just by observation on these forums (I know a little off topic). Those who venture the furtherst from stock seem to have the most problems. A lot of people have blown engines from E85 even though that was supposed to protect them. Lots of very low mileage engines having to be rebuilt using aftermarket seals, Chattering marks and destroyed housings. Unknown causes but most with aftermarket seals. Stock seals can handle the power, they just don't handle detonation well, so we try to find seals that can at the expense of reliability. Why not handle the detonation first and use the most reliable seal?
I'll chime in. I have been reading the forums and replying for some time. I modified my car with some of the knowledge I have gained through this forum and some from my experience and knowledge as an engineer, and I am not a design type engineer.
I went with an external tank and OMP with some premix. I think Mazda engineers knew what they were doing and strategically located the OMP injectors in that location for a reason and I run 2-cycle oil through the OMP. I also pre-mix a little due to running more WHP and ensuring that enough oil gets injected into the engine. Now ensuring how much and exact amounts is a debate, but I do .5 to 1oz premix with a working OMP. I am at 380-400WHP.
So I think lubricant is very important and I spent a lot of time thinking about the options and weighing them against each other.
Then on to what can possibly kill an engine. Most engines need rebuilds due to coolant seals, fuel delivery problems, overboost, or carbon'd up.
Coolant seals are damaged from heat cycling out or age. Ensure water temps and oil temps are in check and replace with viton seals. done.
Fuel delivery problems, keep the fuel filter clean, use the car on a regular basis, use stock parts were can (hardlines, etc), replace with a stock denso supra pump for reliability. Check system on a regular basis.
Overboost can happen from a line cracking going to the wastegate or something with a boost controller failing. Best option would be to go off spring pressure on a wastegate. If something fails like a vacuum line, ensure you have enough fuel to run the engine in an overboost state. But now you need to worry about detonation.
Carbon. probably from running rich. most speculated on that here. I run a healthy idle at 12.6-12.7 AFR to catch the idle from decel. This is needed because the engine does cut fuel when cruising off throttle. The powerFC adds fuel back in depending on when the tuner says to add it back in. Most tunes I have seen add fuel back in around 1100-1250 rpms. otherwise fuel is cut.
Water injection/methanol - This helps remove carbon from the engine/seals/etc. It also removes heat from the combustion chamber and increases the octane (when using meth). If tuned to say 14PSI where the car can run without water meth (safe tune), and you add a water rich, slight meth mix, it removes the carbon from the engine, prevent engine detonation, can save you on a fuel delivery problem (maybe), and protects against a possible overboost scenario.
I do everything above on mine. I would also run stock seals for the best housing to seal interface with lots of design R&D behind them with predictable manufacturing processes/quality control. My car does have super seals in it from the previous owner, and will run till I need a rebuild and replace with stock seals.
And just by observation on these forums (I know a little off topic). Those who venture the furtherst from stock seem to have the most problems. A lot of people have blown engines from E85 even though that was supposed to protect them. Lots of very low mileage engines having to be rebuilt using aftermarket seals, Chattering marks and destroyed housings. Unknown causes but most with aftermarket seals. Stock seals can handle the power, they just don't handle detonation well, so we try to find seals that can at the expense of reliability. Why not handle the detonation first and use the most reliable seal?
#50
Rotary Freak
iTrader: (5)
You can I think I mentioned it . BUT! you MUST get it tuned and set up for it ..
Because I turned on the fuel on off throtle set it at 8k ... and lets JUST say.. the flames comming out of the FD were a bit much . and the MPG definitely suffered ..
if you do remove the OMP . THen You should raise the fuel cut . and lean it out to a point where its not turning black gold into fireworks all the time ..
I have been thinking about doing JUST this .. BUT I dont know what AFR to tune the car to during decell I mean
Because I turned on the fuel on off throtle set it at 8k ... and lets JUST say.. the flames comming out of the FD were a bit much . and the MPG definitely suffered ..
if you do remove the OMP . THen You should raise the fuel cut . and lean it out to a point where its not turning black gold into fireworks all the time ..
I have been thinking about doing JUST this .. BUT I dont know what AFR to tune the car to during decell I mean
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Jeff20B
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09-16-18 07:16 PM