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Rev limiter
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Hello to All,


I'm installing a MJLJ in a racing car, i need to rise the rev. limiter beyond the configurator limit of 10000rpm because the engine easily pass this rpm on accelleration with a max power in the region of the 9500rpm but the engine is capable of 10700rpm on the dyno with a fuel-spark racing ECU. Actually, the car is running with Keihin FCR 41mm carbs and distributor, when tried the fuel injection, the rpm are rised a little, but the power and the trottle response has reduced too much (over 10 hp). Now the owner is interested in try the MJLJ because his mechanic think is possible to have better results with only ignition programmable. This project is a bit at the known limits of the EDIS and the MJLJ hardware-software.

My Question is for Brent:

It is possible to rises or eliminate the rev. limiter? The mechanic has another car with a more aggressive engine and the rpm are higher, he told me the max. power is in the region of 9800-10000rpm, in this case the rev.limiter can be a problem setted at the max. value.

If this can be made, and the EDIS can handle the job, i will test in others engines like this.

Best regards!! Wink

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Hello,

Apologies for the late reply.

In the current firmware implementation the 'soft' rev limit is always there with the maximum settable limit of 10,000 RPMs. Not a problem for the vast majority of people (excluding you, of course! Smile )

Disabling that requires a firmware change. Yet, the MJLJ won't measure past 10000 RPMs, anyway.

The other issue is that the EDIS module may not be stable up to the RPMs you are seeking. Reportedly some EDIS modules can sustain higher RPM's than others, but the information I've seen revolves around discussions on the EDIS-8 variants. Less info is present on EDIS-4. I will have to compare my notes and possibly re-test on the bench to verify the upper RPM limit of a small random sampling of EDIS-4 modules.


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Brent Picasso
Founder, Autosport Labs
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Thanks for the reply Brent. Is a bad news for me Sad Is how i suspected, the EDIS4 probably can't handle rpm to the 10000rpm limit. This is a problem, this engine is capable of 9500-9700rpm max power and a redline over 10K rpm. In this case, the need for another ECU is crucial, but i think the costumer don't want to change for a more expensive system. Anyway, I will try to use the max. resources the MJLJ-EDIS4 can handle without problems.

Best regards.

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Hello Brent,

Unfortunatelly, the car i say can't be handled with the mjlj-edis4, and we are moved to a professional ecu (because we have one to try and do not need to buy first for test. Well without modifing noting of the MJLJ install, only changed the connectors in the wiring loom for the single connector of the new ecu, the results are promising. Accellerating in neutral the rpms rises very fast, and the max rpm reached are 10270rpm. But the last saturday, when we had gone to the rolling road dyno for mapping, we had tested first the original configuration, with the distributor, well, the results aren't too much good how i have expected from the owner has said to me, the best with distributor [email protected] (a little 1150cc 16v engine), well, the engine actually have a year of races and 2 weeks all day in the dyno because the owner have tryed to convert it to fuel injection to another ecu tuner, the results are unsoddisfactory, they have lost 10hp going 1000-1200rpm higher !! and the throttle response are lost too. This is the reason for the test of the only ignition with the MJLJ first and the new Racing ecu now. Unfortunatelly, in the 4th launch to find the max value with the distributor, some bad happened, i don't know what, probably the flywheel fasteners brokened or clutch fault or maybe brokened crankshaft at the flywheel attach (all this issues has occurred in the past during the development of this engine.

But now i want to investigate in another MJLJ install i have made, because i think the sistem is capable to handle the 8500rpm without problems because i have tested and installed in racing cars running 8000-8500rpm. I remember some problems going higher rpm, but we have solved this changing the sensor gap, if i remember well, we increases the gap, from about 0,70mm to 1,0mm or mayby high. Do you think is correct? i Know about the increase of the voltage of the VR signal of the VR sensor, mayby the edis can't handle this and when the signal goes too high, the edis lost rpm-TDC position, when the problem occurr, seems to shut off the power supply. Whit the Race ecu, because this uses the falling edge detection, the signal is better (i had to change some degrees in the configuration sw to obtain the right ignition reading with the strobo light. The EDIS don't uses the falling edge, detection, mayby the rising edge?.

I want to test my other installs to verify the effective capability of the EDIS4 module, modifing the sensor gap can help, we need to know how much without lost signal at low rpm, or we will have start up problems (specially if the starter motor don't spin too fast). Actually, all my MJLJ installs (I have made 5 permanent installs and tested the sisyem in about 7-8 cars) The first installs in NA engines i have used the MAP version, using a vacuum compensation chamber for a more stable MAP signal at low rpms (the cars have single carbs thottle) The results are very good, all of this cars reached good power gains in the entire powerband and gained up to 10 Hp in the redline. actually, i have ongly a turbo engine install, the power is good (about 200hp from a 1.4 litres Renault 5 GT turbo, converted to fuel injection from an old bosh system), we are now upgrading some things and an all new rebuilt engine and hope to pass the 200hp mark, actually we are using all the capabilities of the internal map sensor in the MJLJ, 2500mbar (and is good, our competitors with the same car, are over 2 bar of boost (28 lbs) but with very close power to our car. I have received some request for install a MJLJ in some of this cars, but when i told to they the limit of 1,5 bar of boost reading, they esitates to decide. For a turbo car, is crucial to measure all the boost the car can handle, and probably a little over is preferrable, in this case, we can retard the ignition a lot to handle a unexpected overboost situation without the risk to detonate. My question is, Can i chanche the sensor for anoter with a large scale and made the new calibration? Using an external MAP connected to the TPS version, i think is possible to have the problem solved, but the problem i see is how i can modify the configurator to show the new MAP readings? Maybe the next MJLJ2 can be the anwer??


Sorry for the long post!! Laughing

Best regards,
Antonio

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