on a Cossie running piper 509 (similar to bd16) inlet cam, with 264 duration.


i'm tryin to find out the maxium time available (for injector openin) at all rpm sites between 1000 to 8500 rpm.


as tryin to understand why i'm havin problems on my s8.

Cheers Danny

 

that depends on whether you're wanting to only have the injector open when the inlet valves are open, or not

 

yes only wen inlet valve is open.

 

have you got the opening duration of a bd16 cam in degrees then? if so, just convert that into time over the range of engine speeds. if not, you need it.

does this help?

https://passionford.com/forum/viewtopic.php?t=157347

 

my piper 509 inlet spec.


264 duration, timed in at 110.
lift 10.78mm

 

so is there a equation to work it out?



i take it 1000 milliseconds = 1 second,


so 1 minute = 60000 m/s.


and to 1 rpm = 264 inlet open duration = inlet vavle open for 73.33% of total cam duration per rpm.


So at 3000rpm =

60000 / 3000 = 20 m/s X 73.33% = 14.67 m/s max fuel injector open time???????



so at 7500 rpm =

60000 / 7500 = 8 m/s X 73.33% = 5.87 m/s max fuel injector open time?

Does that look right?


Edited 6/12/05 cos had a long day yesterday

 

don't think that's quite right.

cams turn at half the crank speed, so for every 1 crank revolution the inlet cam turns 180 degrees.

when you get the right time, you don't multiply it by 4.

hth a bit, and back to the maths book

 

opps, edited above post as relized early this mornin my mistake, as well as you relized too. LOL.


how does it look now?

Cheers for your time

 

are you sure that a duration of 264 means that the inlet valve is open for 264 degrees out of one cam rotation? that's 528 degress out of the 720 degres of 2 crank revolutions? how can you fit in 4 strokes if the inlet valve is open for that long?

maybe it means 264 degrees of one crank rotation (so 132 degrees of cam rotation)?

i don't know for sure, i'm just trying to learn along with you.

maybe this diagram, found by Gareth T on this post helps?

 

How long the inlet is open is not that important, it´s the time between cycles that is important. And you just need to know how much time you have at your maximum rpm. At half the rpm you have twice the time, but it´s not likely that your engine can handle twice the amount of fuel just because you have the time to inject it.

It´s 60000ms in a minute and that divided by the max rpm will be:

60000 / 8500 = 7.06ms between tdc and since it´s a 4-cycle you get twice the time. That equals 14.12ms @ 8500rpm

The reason that it´s not that important to inject while the intake is open seems logic when doing some more math, The intake valve will open and close nearly 71 times every sec @ 8500rpm. The fuel will never have the time to stop by the valvehead and "wait" for it to open.

 

i agree with you lars that you don't have to only inject when the inlet valve is open, but what if you wanted to? how would we work out the time available?

 

You seem like a clever chap.. .... why!?

 

come on dave, be fair, there's clever in more ways than being able to read and write properly.

i'd say building a 4x4 cosworth powered fiesta and turboe'd xr2 and having a go at mapping them yourself is quite clever

 

im not saying he isnt clever... im saying he is!

 

I don´t think this is a realistic option for most people.
The inlet only opens every other crank rev, so then you have 7.06ms between tdc@8500rpm
One revolution is 360degrees, inlet is open 264degrees of that. So:

7.06 / 360 * 264 = 5.18ms@8500rpm

This means you need LARGE injectors to get enough fuel for making decent power.

 

LOL at all those guesses (YBP is close)

Will post up the definitive answer later when I have had my tea

 

yes please simon, enlighten us all, but please don't take the piss out us trying to learn something by trying to figure it out by ourselves

 

...or you need both banks of greens firing, 2x803 = equivelent of a large injector.

 

what are the advantages / disadvantages to firing anytime vs. firing only when inlet valve open?

 

Nick, I guess the most obvious benefit firing the injector when the valve is open, is that the incoming air helps to atomise the fuel better = better burn. If you fire before the valve opens, then you could risk fuel pooling/poor atomisation.

 

come on then simon, tell us

 

Sorry, didnt mean to diss anyone.

I didnt see Stu's explaination above so I dont need to go into full detail
as he has done the hard work.

Generally the equation I use ( I have simplified it so you can all follow)

A=RPM/60
calculate crank rotations per second

B=1/A
calculate 1 rev time in seconds

C=B*2
allow for 2 crank cycles

D=C*1000
convert to milliseconds

E=D * 0.90
only use 90% duty cycle (or what even you deem correct)

The value in E is the final maximum allowable injection time in millisconds.


=============================


When talking about SEQUENTIAL injection as on cossies....

Fuel injection point (I.E the crank rotation degrees an injector starts to inject)
is generally only critical at low speeds as you inject MOST of the fuel on a CLOSED
inlet valve just before it begins to open.
The reason is, 1, it cools the valve and 2, the inrush of air mixes the fuel
better than
injecting the whole lot while filling the cylinder.
This applies to low loads and low rpm's only generally.
So its NOT just injection duration thats critical but WHEN it injects.
This is because the slow moving air at low rpm will cause the fuel to drop
out or the mixture if not kept moving.
However, at high rpm, (above >2500 rpm usually) the injection point is advanced
as the average air speed does not change much mixing the air/fuel better.
(on a cossie usually about +90 degrees every 1000 rpm till 5500 rpm)

So you can see, the map is NOT the only thing that matters.

At high rpm and/or high loads, the timing of the inlet valve becomes LESS
critical as generally all fuel in the inlet port will get into the cylinder and
is mixed nicely due to the high speeds and squish effect of the cylinder design.

===============================================

Ok, now back to Dannys original "problem" with the S8.

He complained about getting error code 31.

This error is set when the available fuel time based on the current rpm
is exceeded. The error code also cuts the power to the injectors to prevent
the engine melting. The reason is the map is telling the injectors to open
MORE than the time available. This means there COULD be NOT enough
fuel to match the air, the result - melt down.
I have set this to a figure of 95% of the injection duty cycle in the ecu
software that CANNOT be changed by the mapper only me.
This is a safety feature and therefore protects the user and myself from
destroyed engines and all the sh*t that may go with it.

On Dannys car, he has 8 injectors and a turbo that spools up faster than
ima taking the piss out of me

There may be a possible scenario where the ecu software estimates the rate
of rise of the rpm and may be prematurely causing this fault.
Rather this way than the reverse from an engine safety point of view.
I have been unable to reproduce the fault on my engine simulator YET.


Danny,
Could you please tell me exactly at what rpm this fault occurs
and what boost you think it happens at.?????
You did tell me by email but have lost all my emails since then in a
hard disk crash.

 

Simon:

https://passionford.com/forum/viewtopic.php?p=2287746

 

nice write up simon

 

Cheers billibong,


Simon,

it happens at any rpm, normally when boost comes in (spike) but only wen over 27-28psi

 

Danny, give me 10 minutes, will try it out on the simulator setup I have.

 

Ok

 

I have found the problem !!! It was a software issue
Never shown up before as most people that run 8 injectors, run laggy T4's
that dont generate boost until the rev limit
I was correct, the ecu is predicting the rev rate rise too fast.

I am just modifying the software, can you send me email address
to simon@s8ecu.co.uk and I will send the update programs within an hour.

 

Sounds promising

emailed you. either wise its dannycampion@hotmail.com

 

thanks for the information simon, very interesting, and good to know.