Thread: Megasquirt computer

Thanks Philip. I've got your 'how to' here so I'll give it another look over.

I think the GEMS system would be a good retrofit if your after economy

rovercareI think the GEMS system would be a good retrofit if your after economy

I have thought about the possibility of GEMS and Motronic.

1 Both need crank and cam sensors.These are specific to 4 bolt type blocks/ flywheels/ cams/ front covers. If you have a new 4 bolt type block/front cover then they are a possibilty, but hard (impossible?)on an older block.

2 Both are coded to a particular car VIN. So you have to buy a new one with body functions disabled. I think they have em in UK. But it would be expensive.
4 You will need a VSS.
IMHO the Motronic would be superior as it runs 14.7:1 all the time. Of course this may be a reason that later engines seem to have more loose sleeves.
Regards Philip A

Originally Posted by PhilipA

From my experience in fitting the O2 sensors, this is an accurate article on the SWOT of 14CUX.
It would be hard to get an aftermarket system to perform across the whole range of operation as well as a 14CUX, without a lot of expensive dyno time. 14CUX is really only a Lucas version of Bosch LE Jetronic , which was the state of art before Motronic.
I find Megasquirt interesting, and have been reading about it for a couple of years now. However it still seems to me to be still what the developers say it is, an experimental system.
I guess my major reservations are more to do with ignition operation than injection.
The sequential vs Batch argument is interesting, but I have 4 hole injectors, and a Thor manifold run by 14CUXand Unichip and my idle is stable. I believe the major problem with V8 idle is the old fashioned hosepipe injectors. Sequential may mask it.

The biggest problem I have is how do I get a significant improvement in the advance map ( with a Megasquirt and EDIS), from my current situation of a Unichip advance map developed by Graeme Cooper on many engines with many many dyno hours, without spending hundreds if not thousands on dyno time. Its easy to get the full throttle map sorted, but 10% throttle and every 500RPM , 15%, 20% and so on?

I have seen several Wolfs , Motecs, etc that have problems in some aspect of engine operation. I was at Stockton with a friend with 4.6 and Motec and it took him 5 minutes of cranking to start a very hot engine, while mine started within 1 second. Even though mine has several engine mods- Thor Manifold, Unichip, modded heads,free exhaust, snorkel, my engine run Perfectly under all conditions.( that I have encountered anyway)

You can have a dual advance curve by a number of means. Unichip or other interceptors often have a provision for 2 curves. You can run a Wolf or similar only on ignition duty.

IMHO I would only change my 14CUX if it runs out of headroom on a much larger engine. The only thing you cannot change in a 14CUX in Australia is the maximum duty cycle of the injectors, and I think that the Rpi chips accomplish that. There is a place on the Gold Coast who may even be a ble to do it (Lachlan Riddell? Powerchip?)
Regards Philip A

Hi Philip,
I cant say i agree with some of you statement 100%,
Re the closed loop setup time, at what engine load/throttle does the 14CUX drop out of closed loop.As far as im aware there arent any stock or aftermarket computers out there at the moment that can maintain closed loop above aprox 50% load?
Granted it does take a lot of time to setup closed loop properly but it comes down to how good your base map is. There are many people out there that will argue that unless your running cats 14.7 is richer than you need to be. There are also just as many people who will also argue that anything leaner than 15.5afr goes back wards in the torque stakes and increase fuel consumption.

The single biggest issue i have with interceptors is in my experience (i had a unichip) is that over time thet tune tends to wander,either due to the factory ecu compensating or the tune in the unichip wandering. I would be surprised if any car fitted with a unichip for more than a year without a retune doesnt require somesort of touch up.

Wolf ecu's can run mulitple fuel and spark maps. One map is stored with in the ecu and the second is stored on a plug in cartridge. The maps can be switched from an external switch.
The timing can also be altered based upon airtemp/coolant temp/throttle position/manifold pressure. This is very useful if your trying to get a car to start in very cold or very hot conditions.

The latest Autronic ECU's have an auto tune function that allows the ecu (in conjunction with a wide band 02 sensor) to "selftune" load points This means the base tune can be setup very very quickly.
The wolf doesnt have this function but it does have a wide band 02 input and 02 tracking that allows you to set a afr range that you wish to maintain vesus a given engine load/rpm. This value is also displayed on the hand held interface.
In my experience aporx 80% of the tuning required for LR's can be done on the road with a driver and a passenger driving the laptop. The beach is also a very good place to adjust low rpm/high load parts of the tune.

Obviously a dyno is the preferred option but unless you are trying to ring the last HP or very last KM per Ltr out of the tune it hard to justify the expense

You are correct that a lot of aftermarket ecu's have problems with some aspect of the tune ie poor cold start/hot start or poor idle, I have scene several cars like this too. This all comes down to tuning and setup of the computer. I have also seen alot of factory ecu equipped cars that have poor idle quality, low power and excess fuel consumption.

I suppose it horses for courses The fuel consumption figures you have quoted in your other thread in my opinion are excellent for the type of driving you had stated, Im sure the thor manifold and modified heads would help immensly with that. For what its worth, i work with a bloke who has a v8 landcruiser 100ser and he quotes ltrs/100k's in the 30's when he's towing....

Cheers
Luke

Re the closed loop setup time, at what engine load/throttle does the 14CUX drop out of closed loop.As far as im aware there arent any stock or aftermarket computers out there at the moment that can maintain closed loop above aprox 50% load?

That is something I have never found out. However the Link on the Megasquirt thread says 75%. May or may not be accurate.

Re closed loop and A/F ratios.Totally agree with you. My post didn't question the ease of A/F setup. I was talking about advance curves/profiles. My point is that you can still have the seamless A/F control of a 14CUX and control spark independently as the 14CUX does not have really any ignition function.

Interesting about the Unichip. I questioned Graeme Cooper on this and he swore that the advance settings would never change. Its impossible to check without paying him another dyno fee, but most of the economy gain from the unichip before I changed the engine came from advance, and that still seems to be there.

AFAIK The Autronic Selftune only works with their own O2 sensor on a dyno. Saves dyno time, but not for calculating advance curves.
The system I like best at the moment is
.:AdapTronic:.
Looks like a great system with self learning by driving with final dyno setup for WOT.
If I replaced the 14CUX, I think I would go with this one.

Re the 14.7:1. Yes you are correct that leaner is probably better, but the % increase in economy is pretty small after 15:1, and as you say how much time or money do you spend to get that small percentage. I do not think power or torque increase with leaner mixtures. Max torque (BMEP)is about 13:1 and any leaner loses power/torque progressively.

IMHO, the main economy and power gains with newer cars are from running very high compression, which is enabled by exact advance control, using ECU generated curves supplemented by knock sensors and ,for Motronic, individual cylinder knock and misfire analysis. EG I believe that Motronic in Range Rover 38A runs 14.7:1 closed loop at all times.
Its the high compression running right up against detonation that gives the gains , not so much the A/F .
After market ECUs cannot address these issues without extensive dyno time,This is where the manufacturers spend millions.

Regards Philip A