Siamese Code Trial - With Boost
Turbo Mini Forums

As you say, the input is high impedance so that's not an issue.

Jean

http://www.jbperf.com/

Schrödinger's cat - so which one am I ???

With high Z injectors, it's no big deal to drive 2 injectors from one FET. The required 2A is nothing for any FET someone is likely to use in this application.

Jean

http://www.jbperf.com/

Edited by Paul S on 10th Aug, 2009.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Going about it a different way, I have been using one of the tables off the internet which gives expected HP per injector at 80% duty cycle for a given range of BSFCs. They recommend a BSFC of 0.47 for turbocharged and intercooled, but there is also a table for 0.52

Assuming you mean your doubled up injectors are 960cc/min in total on each port,

From 0.47BSFC table, 960cc/min ~ 156HP @ 80%
So 117HP @ 60%

From 0.52BSFC table, 960cc/min ~ 141HP @ 80%
So 105HP @ 60%

Interpolate for 0.5BSFC gives ~ 109HP

Then double it for both ports ~218HP

So essentially I agree.

Assuming you would know if you were producing 220HP, are you sure about the 12mS ???

When you first mentioned it I commented that it gives 60% duty which is more than the combined valve open time so I was a bit surprised at the AFRs still being balanced.

The only other thing I can think of is open/close times on the injectors.

Schrödinger's cat - so which one am I ???

Thanks Rod, that confirms my calcs.

Certainly not putting out 220hp !!!!

The MS is reporting 12mS peak pulse widths to Logworks. It's also showing 1.8 mS at idle, 5-6mS at 15 psia so it's about right, allowing for a bit of extra fuel under boost.

On the basis that the cam is still open well into the compression stroke, I do not think that 60% is unrealistic. However, on the basis that I cant get lower than around 13.5:1 on the outers, then 60% is higher than what can be considered useful fueling.

It's odd that the AFRs show that the engine must be passing enough air to burn the fuel.

Puzzling :(

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Ooops.

Forgot that at some time I must have dropped the fuel pressure to help the pulse widths at idle :$

Fuel pressure is around 2.5 Bar instead of 3 Bar.

So the injectors are only flowing around 70%.

Still enough fuel for 150+hp.

This does mean that I can increase the fuel pressure to get more fuel into the outer cylinders.

Bugger, it also means that I may not need 3 injectors for 250hp.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

What's your "Required Fuel" value and did you halve it when you doubled up the injectors (unless that was the time you altered the fuel pressure too).

Having said that, although I can't remember the exact formula, surely 0.5bar down on 3.0bar wouldn't drop 30% off the flow ???

Schrödinger's cat - so which one am I ???

My "Required Fuel" is only 1.8.

But remember that I'm running Hybrid mode that should double it to 3.6.

That's still half of what I would have expected. Given that it's running at 12 mS.

I've assumed square law for adjusting the fuel flow. ((2.5/3)^2) = 0.694.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Bugger, I should have stayed in bed.

Fuel flow adjustment due to pressure should be 1/((3/2.5)^0.5) = 0.913.

So still flowing enough fuel for 200hp.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Surely it isn't square law - otherwise doubling the fuel pressure would increase flow by X4 - my Weber Marelli ones are dual rated (3 bar and 6 bar) but the increase in flow is only about 30% from memory.

But agreed - 1.8/3.6 and 12mS don't appear to correlate.........

I'll have a play on the JimStim later because last time I was also getting much longer pulses than I expected from my injector size calculations.

My "reqfuel" is 3.8, two pulse mode, and I was exceeding my planned 20% duty at 5K RPM with injectors that are sized for 105HP (N/A) at 2 x 20% pulses. Yet I would expect the engine in its N/A form to manage 75HP at the best.

Schrödinger's cat - so which one am I ???

I'm thinking that the 12mS is being reported incorrectly.

It may be the way that the interface between MS and Logworks is set up. I know Sturgeo had some trouble getting the data stream right.

I'll have to go and do a log with Tuner Studio.

Better gird my loins for some wheelspin.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Mystery solved.

Tuner Studio is showing a maximum of 8mS pulse width under boost, so the Logworks plug-in is not working correctly.

Re-running the calcs with 2.5 Bar fuel pressure and 40% duty cycle gives 135hp.

So in the right ball park after all.

I would have thought that I could get higher than 40% before struggling with the outers, but this does back up earlier tests that showed similar results.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

my head is sore. *groan

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Paul,

Don't forget to subtract the opening time from the pulse width to compute the amount of fuel. If you have a 1ms opening time that means 7/8 of the 135HP or about 118HP.

By the way, if the logworks plug-in is not designed specifically for this firmware version, I don't see how it would work. Unless it can read the ini file.

Jean

http://www.jbperf.com/

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

That sounds better.... (lost both my phone lines yesterday lunchtime, BT have only just fixed them...)

8mS minus the openning time sounds more realistic and, to my mind is why you hadn't lost the AFRs.

40% (ie, 2 X 20% in my case) is what I'm determined not to exceed.

Are you still thinking three injectors for the Miglia with these new figures ??? I'm not 100% decided.

Schrödinger's cat - so which one am I ???

I wondered where you had gone.

118hp is close to what I had calculated from the airflow etc.

I think 20% per cylinder is a good target that is achievable.

Therefore I will need around 2500 cc/min per port, which is best achieved with three 800s with a bit of extra fuel pressure if required.

Obviously, if you are using low impedance injectors, you may have other options.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Edited by Rod S on 11th Aug, 2009.

Schrödinger's cat - so which one am I ???

Is injector sizing linear? e.g. it looks like for the siamese code you need about 100cc for every 10hp.
So for an engine of about 150-160bhp you'd need a couple of 800cc injectors.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

The staging is presumably to avoid crippling low pulsewidths for lower RPM/idle operation.