General engine questions

In short, engine speed will continue to rise, but as the speed increases, the engine will start to run lean and cause damage if run for a prolonged time with a lean burn situation. Also performance will decrease. The speed it will rev to will depend on the particular engine.

The amount of air increase will only be marginal as the engine is still pumping the same amount of air, albeit with a slightly lower vacuum in the inlet manifold. The engine speed will still rise, but once again performance will reduce.

It will create a slight rpm limitation, but it would be quite erratic in what speed it would rev to (it would vary greatly depending on engine load)

M Cuthill skrev:

Thanks for your reply, let me tell you the background of my questions...

I've designed an electronic blackbox which measures injector pulsetimes and adds about 30% extra time to allow use of alcohol (ethanol) in order to have the lambda correct. And at about 4000rpm and maximum throttle I get the "injector saturated" warning light turn on. This results in, as you tell, a lean burn condition, which worries me. I then thought that when reaching this critical limit, the engine wouldn't have the chance of increasing rpm, thus some form of automatic rpm limitation. But you tell that, though the engine runs lean, it will still increase rpm. That's not good. I would rather see the engine more or less rpm limited at this point the burn turns lean. But you also tell that performance during a lean burn will be bad, so actually the output power from the engine will drop, which would tend to decreasing the engine speed, right?

powerampfreak ( snipped-for-privacy@hotmail.com) gurgled happily, sounding much like they were saying :

This might be a silly question, but why would you reinvent the wheel, when there's programmable ECUs like Megasquirt about already?

Adrian skrev:

There are no silly questions...and I know of Megasquirt indeed. Though, the price of my box compared to MS is very low, and my box is much easier to install than a complete MS system. Besides, it suits to a big number of brands. "Anyone" could install it , with very little engine knowledge. This is not true for a MS system.

In news: snipped-for-privacy@d34g2000cwd.googlegroups.com, powerampfreak wittered on forthwith;

Thing that worries me is it appears to be designed by someone with very little engine knowledge.

Pete M ( snipped-for-privacy@bogoffwithzepressedmeatblueyonder.co.uk) gurgled happily, sounding much like they were saying :

Quite.

Particularly when an MS ECU kit is about a hundred quid, yet his is "very low" price compared...

I can't possibly imagine how anybody could replace a factory ECU and put a viable map together with "very little engine knowledge".

Wow. =A3100 sounds cheap so I hate to think what a sub =A350 one would be= =20 like. Hell, it costs more than that to convert my car from points to=20 electronic ignition.

Badly? Obviously no idea what 3D mapping is.

--=20 Conor

How about taking the safety labels off everything, and let the=20 stupidity-problem solve itself?

He didn't say he did that.

He said he designed a box which would extend the fuel injector pulse by ~30%. So there's a box that sits between the ECU and the injectors, increasing the duty cycle of each pulse...

David Taylor ( snipped-for-privacy@yadt.co.uk) gurgled happily, sounding much like they were saying :

Even when it's inappropriate...

So the engine will use 30% more fuel at all times, and run massively rich.

Except it won't, because the lambda will knock the overfuelling back...

Adrian ( snipped-for-privacy@gmail.com) gurgled happily, sounding much like they were saying :

Of course it bloody won't, because the lambda will be right because of the effect of the Ethanol...

Would your average narrowband Lambda do that automagically anyway? Possibly not.

But the MS is very simple to install for anyone with basic electronics knowledge and a good level of engine/control/tuning knowledge. To convert a car to run on ethanol you do not just need to adjust fuel injection ratios across the board by a fixed %, and you should know an aweful lot more about engine tuning than just the relative AFRs. And considering lambda 1 isnt ideal for max power your X% adjustments will be wrong at high load situations and doesnt take into account cyl temps and the adjustment of mixture to cool the cyl walls.

Re-mapping on a different fuel with different calorific content and different knock supression abilities takes a LOT of time and effort and a good 'tuning head', time on a dyno etc. The engine will react differently to the fuel and you will need to monitor exhaust gas temps to ensure you dont end up with total meltdown. The cost of all the extra knowledge and equipment needed to do it safely totally negates the cost of your product. I have built and installed a fully working MS system in my car for =A3300. IT needs mapping (say another couple of hundred). If you make a product that drops into any vehicle without the correct adjustments for other possible mods etc (Which are unique to an engine/car combination) you will end up with no engine, very quickly. IF you sell this product to others you will end up with lawsuits, very quickly too.

It will be relatively correct in most locations as the lambda sensor reads oxy content so wont know what fuel its running on, but as you say, its not as simple as that. For a start the o2 sensor only works between certain rpms and not at WOT. If this tuner hopes to gain massive power increases by using ethanol, he will be doing it at WOT, where the stock ECU cant keep control of itself. IF the injectors are near 100% they can float and either run lean or rich. The poster clearly doesnt understand the depths of control required to tune an engine, but im sure he/she is learning so lets not be too harsh.

Coyoteboy ( snipped-for-privacy@hotmail.com) gurgled happily, sounding much like they were saying :

What in? Something on factory injection or as a conversion from carb?

Get it broadly there so it runs cleanly across the rev range, then log it, run the log and map through MegaTweak, repeat until right.

S'wot I'm planning to do if I ever get round to doing anything with this collection of bits...

Its not quite that simple unless youre running a low power, non-turbocharged, fueling only setup. I'm running full spark control and fuelling to 300bhp which is 50% increase on stock with 100% higher boost levels - at this point you're not just worrying about your fuelling, despite having wideband AFR monitoring and AFR targetting set up - you're still only 3 seconds worth of too much advance away from total meltdown, holey pistons and a big rebuild cost. If I was doing a lower power setup on a normal runaround or converting a carbd car I wouldnt have an issue with giving it a rough setup. But then i wouldnt bother fitting an MS to a normal car, except if i were doing a gas conversion.

Its worth it, and i am road-mapping but it is a big risk enginewise. What car/engine you doing it on, out of interest? Are you a member on msefi?

Oops, missed that bit. Its a '91 Celica GT4, turbocharged 2 litre 4 cyl, using all stock sensors except for wideband oxy sensor and fast response intake temp sensor. All mounted in a stock ECU case and connectors so i can plug n play if i have a fault. Was working great until my nearside front caliper seized the other day and since then its been sat in the drive looking forlorn lol.

Look, my box is a microcontroller with injector drivers connected between ecu and injectors. It simply adds 30% extra injector time since ETHANOL HAS LOWER ENERGY CONTENT AND THEREFORE ENGINE NEEDS 30% EXTRA FUEL TO KEEP THE CORRECT MIXTURE AND ACHIEVE LAMBDA 1. IT'S NOT TO INCREASE POWER. I would wish that all posters did READ THE ORIGINAL POSTINGS BEFORE JUMPING ON UNRELEVANT FACTS, thank you.

Should be 34% apparently.

Well done, we read that in the first one. My point, about not always running at lambda 1, was nothing to do with that if you read my post, and linked to the reason the change of fuel is being considered, which you never stated.

That would be "irrelevant" but.... your question raises questions that need clarification - i.e. what is the intended work environment/point of the product. Life isnt black and white. Why would you want to run ethanol, other than "green" reasons? Its harder to get hold of, more expensive (currently).

Your question was answered, well and truly, by the first replies. Others were simply adding thoughts that you might want to consider in your design. If you give very little information and sound like you dont know what you are doing (which im sorry but you do sound that way) then people will warn you about the problems you MAY face to try to save you from failure. Provide more information and you will get less of what you consider irrelevant. Otherwise dont be so ungrateful when you came asking for help.

Coyoteboy skrev:

bla bla bla.... ethanol costs much less than unleaded, also counting in the 30% increase in consumption.

And there endeth the helpful replies...

Still, back to school now so it should quieten down a bit.