Winter Strip Down and Rebuild (Done and Dusted)

[hiscot]

mike are you still running the std fuel pump it must be close to max in new condition without using more bar ?
be a shame to waist a r/road session ?
does you traction also use advance control as well as injector cut and anyway to keep an eye on afr during traction just incase it runs lean ?
you thourght the oil cooler cowl was expensive ( now on e bay £25 buy now, always the way ) the support bracket is £86 + vat ect look like i will be making one at the weekend
ps are your costs still within budget

[Mikie711]

Standard fuel pump at the moment, probably end up running a piggy back pump or splash out and get the elise shop upgraded one if mine is US.
Traction control cuts 1 in 5, 2 in 5 or 3 in 5 injector pulses. As the K is batch fired 50% of the injector cycle is against a closed inlet valve so the cut sequence should lean off the mixture too much. Logging the AFR will show up any significant changes when the TC/LC is used.

Kenny, I would go for either goodridge 200 series hose or hydraulic hose swedged if I could get 1/2"BSP fittings not the original lotus ones as they cost a small fortune. Think I was quoted £100+ each FFS.

[robin]

The fuel that goes against the back of the closed inlet valve is part of the fuel load - even with sequential injection a whole bunch of the fuel is squirted against the back of the inlet valve because the injector is running for almost the whole cycle of the engine. The fuel vapourises to some extent; the rest pools on the back of the valve and vapourises again as soon as the inlet valve opens.

Unless the TC controller is aware of the batch nature of the K's injectors I wouldn't let the TC cut injector pulses. Imagine it cuts just 1 pulse. Both cylinders on that batch will get a 50% fuel load for that cycle. When the spark fires the very lean mixture will burn fast and the flame front will reach the top of the cylinder before the piston does - severe detonation!

The easiest solution is to wire the injectors individually OR to control power by retarding the ignition, I think.

Cheers,
Robin

[Shug]

Robin - I think Mike is wiring the injectors individually (sure I read that earlier in the thread...)

[robin]

Traction control cuts 1 in 5, 2 in 5 or 3 in 5 injector pulses. As the K is batch fired 50% of the injector cycle is against a closed inlet valve so the cut sequence should lean off the mixture too much. Logging the AFR will show up any significant changes when the TC/LC is used.

Shug, I agree that Mike has said he'll use sequential injection earlier in the thread, but the above is still something I would recommend against, whether or not Mike uses that approach, IYSWIM. I was just trying to point out that the effect of cutting 50% of the cycle would be a lot worse than the AFR being wrong - it would be dangerous for the engine.

Cheers,
Robin

[Mikie711]

The xoombox is wired to both the ECU signal and power wire for the each injector. With the signal wire it knows when the injectors are being fired and because it was control over each individual injectors power wire it can cut single injectors rather than pairs of them. So when it cuts 1 in 5 it is cutting the power to only one injector on each cycle not both IYSWIM.
Take a look at he online documentation here

[hiscot]

mike looking at your oil pipe photo , is your out and return mixed up ?
found this thread on seloc
http://forums.seloc.org/viewthread.php? ... pid3706077
???
might be worth checking

[robin]

Hi Mike,

Are you running fully sequential injection or twin-batch injection (i.e. as per standard EU2 K16)? I don't believe the XoomBox properly supports the twin-batch. Here's why - in their documentation they state:

On some systems - notably K Series or Emerald - you may find that two injector drivers are used instead of 1. This is simply to reduce the load on the electronic switch and does not alter the operation of the system. In such a case, the J2-4 and J2-5 connections can be made to either driver.

This is wrong - it may be that their product will work with J2-4/J2-5 wired in parallel to either driver BUT the statement that this is done simply to reduce the load on the electronics switch is wrong. The standard MEMS driver (and the Emerald for that matter) drive the two injector pairs 180 crank degrees out of phase so that at least one half of the fuel squirts when the inlet valve is open. Knowing the timing of one does not easily give you the timing of the other.

If you wire the xoombox the way it is drawn in the second diagram (titled "4 batch fired injectors with XoomBox") on this page then the box is only seeing when one pair of injectors being fired and has no idea when the other pair are being fired. If you're using twin-batch (standard EU2 K16) injector wiring I would suggest you should wire J2-4a/J2-4b in parallel to one injector drive circuit and J2-5a/J2-5b to the other (now the XoomBox can see the timing of each injector pair).

The reason this matters is that their switches are not designed to interrupt the current while the injector is open - they want to break the circuit while the injector is closed and no current is flowing - this wiring will achieve that.

BUT I don't see any input to the XoomBox that would let it know which phase the engine is on (i.e. is cylinder 1 in the compression or exhaust stroke). So I don't know how it could possibly know which of the four cylinders currently has a 50% charge sitting in the intake tract. The only sensor in the whole engine that allows this is the EU3 or EU2 VVC cam position sensor (but then the EU3 is fully sequential injection anyway), but there isn't any input on the XoomBox, even if you had such a sensor fitted. Do you know how it works?

It's your engine, but if it were mine, I wouldn't like to deliberately engineer a situation where you will regularly explode a 50% fuel load on full throttle!

I designed a similar system once but chose to interrupt the ignition circuit instead ... it's a much harsher environment to interrupt (400V and bigger spikes on the low voltage side), but ultimately it's safer, and also it allows you to vary the ignition timing which in turn gives you finer control over power delivery.

Cheers,
Robin

[campbell]

Robin,

Shouldn't you be working in an F1 team

Campbell
(humbled faction)

[Mikie711]

mike looking at your oil pipe photo , is your out and return mixed up ?
found this thread on seloc
http://forums.seloc.org/viewthread.php? ... pid3706077
???
might be worth checking

I checked this against the oil paths shown in the rover supplement in the Elise manual. The oil filter housing central pillar (the bit the fiter screws onto) should be the feed from the oil pump. The oil then flows through the filter and out through the hole in the base plate into the main oil gallery to feed the crank and head. Assuming the diagram is right then I have it the right way round. If however the manual is wrong then its backwards which will mean having to swap round the 2 hoses on the feed side of the oil stat. Will see when I prime the oil system which hose is feed and which is return just to confirm but pretty sure it's right, unless someone knows differently.

Robin, I will have a look through what you a have written when I have more time. At work just now, will read it all in the morning, cheers for your help with it BTW.

[Mikie711]

Robin, this doesn't answer your points fully but does cover the issue of fuel cut v's spark cut TC. I had thought about the leaning issue but didn't think it would have as much impact as you have suggested. It would seem that fuel cut is the preferred method and almost a must in catalytic equipped cars, such as mine. Not sure how to get the fuel below 50% though, as I am pretty sure it will be running rich anyway it would probably be above the AFR required to burn. Maybe need to speak to David and see if there is a way to cut both injector pulses to one cylinder at a time.

Fuel Cut
The idea of cutting fuel to an engine sets alarm bells ringing in engine builders, as they all know of the potential disaster of a high revving race engine running lean. Running in a lean combustion mode will elevate in-cylinder temperatures very rapidly, the denser the air/fuel charge, the more heat the lean burn can generate. Therefore it is vital that a fuel cut system will not cause a lean burn.

The simplest way of preventing a lean burn is to remove more than 50% of the fuel from the pulsed delivery. A mixture will only ignite if the air/fuel ratio is within a tightly defined window, look at the efforts being put into making lean burn engines fire on very low air/fuel ratios (1:20 or more). Removing more than 50% of the fuel will cause an air fuel ratio of over 1:25 and will result in a complete miss-fire, with the unburned fuel passing out through the exhaust valve. Even if a high air/fuel ratio did manage to ignite, the energy available from the amount of petrol injected wouldn't be enough to elevate temperatures significantly. Of course the ideal system will remove 100% of the pulsed fuel delivery, allowing the cylinder to take a gulp of fresh air, and the in-cylinder temperature would remain virtually unaffected. Our Traction Control operates in this manner - the complete injector pulse is removed so no possibility of lean burn can exist.

Prolonged fuel cut on one particular cylinder would cause scavenging of the petrol lining the inlet tracts, and when the next full fuel pulse arrived, it would be partially reduced in quantity by the re-wetting of these tracts. Therefore it is often important to manage a rotation of the cylinder cutting to prevent this situation from occurring.

Spark Cut
Cutting the spark to an engine will stop any chances of a weak mixture occurring, but it carries it's own potential problems due to a large quantity of unburned fuel travelling through the cylinder and out of the exhaust. This petrol can remove some of the oil lining the inside of the cylinder, and pass it thorough the exhaust, again this only becomes a problem if the fuel to one particular cylinder is cut for an extended time. The best way to overcome this is to rotate the order in which the cylinders are cut.

The unburned fuel in the exhaust will have a catastrophic affect if there is a catalytic converter in the exhaust, as it will try to convert the unburned fuel to harmless elements, effectively burning the mixture. This causes the catalytic converter to heat up very rapidly, reaching temperatures in excess of 1000°C, and possibly melting down completely. Thus prolonged spark cut is not recommended for catalytic equipped cars.

Be interested in your thoughts

Mike

[hiscot]

Mike the text above is taken direct from the excellent race logic site
http://www.racelogic.co.uk/?show=Tracti ... w_it_Works
their system is regarded as fantastic with no known engines blow ups , is your system a direct copy ?

[robin]

I hadn't considered the 50% fuel load as being non-flammable - if that is indeed the case, then there isn't much to worry about - we must have some chemists from the petrochem industry on here that can tell us ...

My concern wasn't the leaning out of the cylinder causing raised exhaust temperatures (though that is a general problem of running lean) - I don't suppose the engine does many traction control limited cycles, so the impact on running temperatures is not likely to be significantly changed.

I was concerned that a leaner mixture (if it burns at all) burns faster and the flame front will reach the top of the cylinder much too quickly resulting in pressing the piston down the way before it's reached TDC.

Cheers,
Robin

[robin]

P.S. Rather than cut the spark, my system was designed to retard it - there is no harm in burning the fuel a bit late - you can time the ignition so that the power produced is much reduced, but the cat won't see unburnt fuel. Retarding the ignition is going to be smoother than misfiring the engine, I believe. I also understand that the fuel cut system is easier to implement reliably, so I can see why they do it compared to a spark cut.

Cheers,
Robin

[Mikie711]

Bob, It was indeed from that site, I came across it when looking into what Robin had talked about. I also never considered weather the mixture wold burn or not so should be OK. David has been running the system in launch and traction mode for a good chunk of last season while developing the xoombox, without any problems so far, so I feel quite happy about running with it. If any problems do appear there are enough people in different cars going to be using it next year that they should get ironed out quite quickly. Quite look forward to seeing how it copes TBH. On the hunt for a suitable GPS receiver to use with it now.

Robin & Bob, cheers for all your feedback it's more help than you know