Oil Metering Pump

[benspeed]

OK - I have a used OMP that I plan to install to hopefully remediate the "limp mode" situation I've been dealing with. (Thanks again to Chris for the master switch On/off technique when the car does go into limp mode. Happened again at LRP and I still finished 2nd after doing the reset.)

So, I've got an '89 second gen with the electrical OMP. How do I go about changing this thing over? Seems to be simple, but I always amaze myself by how I can get it wrong. Any special calibration or setup after it's installed? Pointers would be most appreciated.

Thanks,



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BenSpeed
#33 ITS RX7
BigSpeed Racing
NNJR BoD - Treasurer
[email protected]
NNJR

[tims90rx7]

As a competitor of Ben's I actually appreciate it when his car goes into limp mode ;-)

Congrats on the second at LRP...you are turning up the heat in the NAARC standings!

I've gotta get back in my car...see you at NHIS in July?

Tim

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Tim Estes
ITS 1990 RX-7
NER

[Doug Ford]

Hey Ben, it looks like I am having the same problem you are having. I thought that the speedsource cars were disconnected anyway. I have always pre-mixed my gas anyway. I guess I will follow this for instructions.

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SpeedSource rx-7 ITS #12
2004 Suburban white
2001 supercrew white (tow vehicle)
memphis

[its66]

FYI..Mine is still connected. The last time I talked to David, he said to leave it.

Fortunately, I haven't experienced the limp problem, so i won't be much help on that.

Jim
ITS66

[Newbie]

Hey,

Whats Limp Mode??

I have a '87 speedsource and couln't get it past 6000 rpm last race.

[Mike Guenther]

In limp home mode you can't even get to 3000 RPM and the car is bucking and sputtering and wants to just die. Mike Van Steenburg told me that you can attach a good OMP and tie it to the side of the motor and it will fool the computer to keep the motor running. I don't know how that works because I assume that the OMP is putting out a pulse signal to the computer to indicate rate of flow. It the signal generator goes bad then the computer puts the motor in limp home mode so that you don't burn it up rumming without the oil being injected. If you can fool the computer by attaching an OMP without it being installed and turning, then I would like to know just what the computer is looking for in a signal from the OMP. If it is a pulse like I suspect, then merely hanging a good one off the side of the motor wouldn't send out the pulses if it wasn't turning. If it is a pulse then I don't understand how the trick would work. Also if it is a pulse, it could be simulated easily and a foolproof way to satisfy the computer could be cheaply devised. You would need to pre-mix to preven engine damage in the event that your OMP failed and the computer was fooled by the simulator.

[Newbie]

I assume the electrical signal is only in the S5 motors since my S4 has a mechanical pump.

Whatever the case, the problem I'm having sounds similar to Limp Mode. Unfortunately, for me it means limping around the track, taking 3rd gear turns in 4th.

What the heck is wrong with this motor???

[bldn10]

To eliminate limp mode issues add the following to your fuel:

Sprints - Viagra

Enduros - Levitra

Unsure - Cialis

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Bill Denton
87/89 ITS RX-7
02 Audi TT225QC
95 Tahoe
Memphis

[benspeed]

Hey Tim - I'll definitely see you at NHIS. I'm coming up early to practice, I want to be in the 1:14s

Mike Vansteenberg told me about the trick of hanging a good OMP on the side of the motor as a temp trick. Not sure why it works.

I do pre-mix my gas - Rx7 guys should do that for motor insurance. 5 oz of 2 stroke oil to 5 gallons of gas. From what I understand most 13b race motors have the pump disconnected to everything but the computer - but I'm not an expert.

I will call ISC Racing - Mike V - and see if he will give me the download on how to do the replacement. NHIS is a twisty track that has no chance to do the reset trick without danger of missing a turn.

Cheers,

[C. Ludwig]

Originally posted by Mike Guenther:
In limp home mode you can't even get to 3000 RPM and the car is bucking and sputtering and wants to just die. Mike Van Steenburg told me that you can attach a good OMP and tie it to the side of the motor and it will fool the computer to keep the motor running. I don't know how that works because I assume that the OMP is putting out a pulse signal to the computer to indicate rate of flow. It the signal generator goes bad then the computer puts the motor in limp home mode so that you don't burn it up rumming without the oil being injected. If you can fool the computer by attaching an OMP without it being installed and turning, then I would like to know just what the computer is looking for in a signal from the OMP. If it is a pulse like I suspect, then merely hanging a good one off the side of the motor wouldn't send out the pulses if it wasn't turning. If it is a pulse then I don't understand how the trick would work. Also if it is a pulse, it could be simulated easily and a foolproof way to satisfy the computer could be cheaply devised. You would need to pre-mix to preven engine damage in the event that your OMP failed and the computer was fooled by the simulator.

I posted this in another OMP thread but here goes again. The S4 electronics do not monitor the OMP. The OMP function of the S4 is wholey mechanical. There is a stepper motor built into the S5 OMP. It's the round, black case on the side of the OMP. The engine turns the pump but the stepper motor is what meters the oil flow. The ECU controls and monitors the stepper motor. It has no control or feedback over the actual pump that is driven off the engine. So the OMP can be detached from the block and as long as it's in good order and plugged in the stepper motor will continue to function and provide the proper feedback to the ECU.

The stepper runs a plunger that meters the oil flow. There is a variable resistor that rides up and down on the plunger. The resistor is shimmed with thin metal spacers to provide the proper voltage range. The ECU needs to see a variable voltage while the pump is in operation. You cannot fix the voltage in the center of the range with a fixed resistor and avoid limp mode. The voltage needs to fluctuate in accordance with load and RPM. When the ECU sees X load at Y RPM and the position of the plunger doesn't correspond the fun ends.

When the OMP goes bad it's possible for them to take the ECU out with it. Haven't confirmed this but it's well rumored. Changing to a known good OMP won't always cure the problem without also changing to a known good ECU.

When limp mode occurs the secondary injectors are shut down. When that happens the engine goes extrememly lean over the 3800rpm switch over point. Lean enough it won't rev past that point at full load. You can rev the engine with no load and part throttle. But load it and go WOT and it falls flat. It sounds like you've hit a soft rev limiter. Pop, sputter, etc. If the car is revving strongly past 4000rpm but encountering problems higher in the rev range the problem is not limp mode related.

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Chris Ludwig
08 ITS RX7 CenDiv

[This message has been edited by C. Ludwig (edited June 07, 2005).]

[Mike Guenther]

Chris,
you Da Man! Thanks for that info.

[benspeed]

Chris - awesome update - that is some quality technical info. I will also look into getting a new ECU since my car is also breaking up over 7800 rmp. ECU is cheap compared to an OMP. New OMP is like $1000. I bought a used one for $250 and hope that it's good.

[paulydee]

Ben,

The 7800 RPM breakup is actually the rev limiter coming into play. I had this problem consistenty, and very noticeable on dyno pulls. I got the rev limiter remove and now the engine pulls clean all the way to 9K.

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Paul D'Angelo
73 ITS CENDIV
Indy Region
http://www.iridiumracing.com

[benspeed]

Hi Chris - no rev limiter in the car - she'll pull through 10K. But around 7800-8000 folks at Start Finish tell me it sounds like I'm hitting a rev limiter. Car still pulls and I don't hear or feel any sputter, but when I rev it while parked I can hear minor breakup - it's not real bad, but not good for performance.

Any ideas? Got new plugs in, ground looks good, wires have 2 seasons on them - might replace those. ECU related to the OMP??

[Newbie]

How do you remove the rev limiter from the ECU?

[paulydee]

You have to send it out to get reprogrammed.

[Doug Ford]

My cars runs fine until the cars runs for a while. For example at the last race I ran practice/qualifying on Saturday morning and it seemed to run fine. Although my times were about a 1 seconds off my normal pace (no clean laps due to traffic). In the race I ran about 2-3 laps and it went into what I was calling limp mode. On my car I have a Pi dash and all of a sudden the RPM guage goes away and the car just doesn't run very well at all. It will rev past 3,000 b ut my times drop by about 2-3 seconds a lap and you can feel in in the lost horse power. I remembered this thread and I turned the kill switch off and back on and the car satrted running again like normal then after about a half a lap it happen again. I am not sure whether this is the limp mode thing but with some of the description I have read it sounds like some of them but not all of them. Any help would be appreciated. I plan on trying a different OMP and maybe an alternate computer just to see if it fixes it. I would just like to know what everyone else thinks and if the OMP change fixes the problem.



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SpeedSource rx-7 ITS #12
2004 Suburban white
2001 supercrew white (tow vehicle)
memphis

[seckerich]

Check your trailing coil and the grounds to it. The tach signal is all from that coil and they will drop out if they are searching for a ground or the coil is bad.
Steve Eckerich
ITS Speedsource RX7

[benspeed]

Doug - what you describe sounds like trouble I've had. Here's the rundown on stuff to check:

Throttle position sensor screwing up your computer
OMP screwing up the computer
Mass airflow sensor wires busted/chafing and screwing up your computer
Ground loose
ECU going bad
OR - secondary injectors clogging. This last one took forever to figure out since we have to take the air/fuel system apart to find the problem

I'm betting OMP because you are going into safety mode or limp mode. Can you letup on the gas and she wants to come to life, then you floor it and she dies again?

Let us know what you find.

Cheers,

Ben

PS - still trying to find time to change my OMP - I'll let you know what happens after the race on 7/9 at NHIS.

[bldn10]

Doug and I were talking about his problem and he had been thinking OMP. I was reading my Haynes manual on it and it sounded like you either have an electronic or mechanical unit. I see from Chris' post that indeed the S4 cars have a mechanical pump and the S5 an electronic one. Therefore, doesn't that mean that a limp mode problem in an S4 car cannot be the OMP? Since there is no signal to or from the ECU, the ECU can't be directly affected. (Which is not to say that a fauly OMP might not ultimately have an effect on how the engine runs.) The weird thing is that Doug's what-we-thought-to-be all-S5 car has a mechanical pump.

Steve, we made the tach-trailing coil connection and tried 3 different coils w/o success. We also tried a different fuel rail and crank angle sensor. Doug had lost the screw on the TPS and we eyeballed it - can it be off so bad as to cause this?

Let me throw this out for consideration -water thermosensor. If it is erroneously telling the ECU that the engine is burning up, could that not cause the ECU to go into limp?

Anyone other than Paul going to Mid-Ohio next weekend?

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Bill Denton
87/89 ITS RX-7
02 Audi TT225QC
95 Tahoe
Memphis