Nitrous duty% vs. flow relationship ?

[PetriK]

As part of the building an gen2 ECU nitrous controller (with gear controlled duty cycle) I am trying to find out the duty% vs. flow for fuelling calculations. In more concrete terms need something like the table below.

jet #40, bottle pressure psi 1000

duty 100% = 50hp
duty 90% = 45hp
duty 80% = 30hp
...
duty 50% = 10hp

The current status of the project is that we have a module ready that where the nitrous is activated using DSM button, nitrous solenoid (relay) is connected to the pair connector and no additional fuel computer is needed. The nitrous duty cycle can be set individually for each gear and the additional fuelling is provided by the ecu. Activation window is built in 8000-11000rpm, TPS > 95%. No additional push buttons or activation switches are needed. As usual - this is for testing and no commercial interests involved.

[sportbikeryder]

Since most controllers are not as nice as this, most people don;t know how much fuel is actually required  for less than 100% duty cycle.

this may be the best nitrous control available once it gets implemented.

[PetriK]

From reading some articles I am getting an impression that ss we are controlling nitrous as well as fuel in liquid form, it should mean that duty cycle affects both flows with same linear rate.

What I also understad is that the jet should be as close to nitrous solenoid as possible. This means that nitrous systems where the jet is integrated to solenoid and then an small black or blue hose to the airbox should work best with duty cycled controller. If a nitrous bar with jets at the airbox far away from the solenoid is used then the line between solenoid and jet acts as a pressure reserve and the duty cycle control will not work. This may also be the reason why some riders have never been able to get the progressive systems to work. So its no nitrous bar with jets folks, just the thin black line to the airbox from a solenoid with one main jet.

ps. to put this question in perspective, I have been running nitrous setup since 2006 and our team bike (kawi) has been #1 for two years in national PSB series with nitrous setup. With this the gen 2 ecu nitrous controller I am hoping to put this still thin experience gained into use and build a nitrous controller that we wanted to have had - like sportbyker said, hopefully a very good one.

[sportbikeryder]

We run a solenoid in the rear and a 4 way split spray bar in teh airbox with the jet at the airbox....good enough for 8.48 with 235 lb rider

Even with this setup, .1second difference in build time is noticable. While the setup as you mention may be better, the way I noted above does still work.

Perhaps the best is the solenoid in or very near the airbox.

[Stocker64]

i think that as soon as it starts to be tested....you will get plenty of feedback.....reall good start here......

[Gixx1525R]

Very Nice

[Stocker64]

i will be installing it as soon as the harness comes in....and giving feedback as soon as i go to our local track and test......

[Stocker64]

Very Nice

nick, would you join us and share some of your insight and talents with nitrous...??  http://www.activeboard.com/forum.spark?aBID=99460&p=3&topicID=33494433

[sportbikeryder]

i will be installing it as soon as the harness comes in....and giving feedback as soon as i go to our local track and test......

You going to get a rider that isn't afraid to spray it?   

[Stocker64]

i will be installing it as soon as the harness comes in....and giving feedback as soon as i go to our local track and test......

You going to get a rider that isn't afraid to spray it?   

no...but this new bike is a WHOLE different from the 72"wb bike.....58 1/2 right now.......

[Stocker64]

i will be installing it as soon as the harness comes in....and giving feedback as soon as i go to our local track and test......

You going to get a rider that isn't afraid to spray it?   

i like internet racing alot better....hide behind my keyboard and post away in comfort....hell i had the a/c on today....80 degrees here.....

[Gixx1525R]

Very Nice

nick, would you join us and share some of your insight and talents with nitrous...??  http://www.activeboard.com/forum.spark?aBID=99460&p=3&topicID=33494433

I sure will. I saved the thread and will sign up. I'll post on monday

[Stocker64]

Very Nice

nick, would you join us and share some of your insight and talents with nitrous...??  http://www.activeboard.com/forum.spark?aBID=99460&p=3&topicID=33494433

I sure will. I saved the thread and will sign up. I'll post on monday

nice to have you onboard.........

[sportbikeryder]

i will be installing it as soon as the harness comes in....and giving feedback as soon as i go to our local track and test......

You going to get a rider that isn't afraid to spray it?   

i like internet racing alot better....hide behind my keyboard and post away in comfort....hell i had the a/c on today....80 degrees here.....

It was warm here yesterday too. Made it up to 42!

[Gasabusa1]

As you are running a pulsed system you will need to have the fuel match to the nitrous when pulsed.Due to syncronisation issues this is not possible so you need to make a decision as to how you intend to match the fuel.
For the A/F to be perfect when the nitrous is pulsed on, its best to make the injection duty cycle the same for 50% modulation as it is at 100%.This will make the a/f too rich for when the nitrous is pulsed off but spot on when the nitrous is pulsed on.
If you try to make the A/F match the nitrous say when its at 30% modulation it will be to lean when the nitrous is pulsed on and only slightly rich when the nitrous is pulsed off,in this example 70% of the time.
It will damage the motor sooner or later if you try to add 10bhp's worth of fuel to a 50bhp kit pulsed at 20% for a prolonged time,even though the overall A/F won't look too bad.

[PetriK]

Thanks for this very good feedback.

in our case the fuel will be delivered with stock ecu and hence not pulsated separately. Rather we use just % addition to fuel delivery. There is no need to know anything about fuel pulse timing as the pulse will be always optimum, i.e. injetors opening with the intake valves at any engine rpm.

There seems to be around up to 80-100% more fuelpulse lengt available from stock ecu. Beyond this the secondary injectors need to be changed to bigger ones to retaing the maximum pulsewidth within limits.

So no need to consider wet systems for up to something like 100-150hp and after that depending on secondary injector size. Stock fuel pump though limiting well before that.

How do you guys see this practiçal 100hp limit with stock stuff ?

[Gasabusa1]

Petrik I realise that the fuel will supplied via the ECU but you are pulsing nitrous in bursts,it will enter the combustion chamber in peaks.So for a few strokes you will have no nitrous then some nitrous then no nitrous a few strokes later.This is difficult or nearly impossible to match due to the differences in the nitrous delivery systems and time taken.For example if the lines are long to the nitrous injector, the time will be greater than if they are short.So for the burst of nitrous you'll need a burst of fuel two different nitrous line lengths will mean two different times that the nitrous arrives so you'll potentially have fuel and no nitrous as the ecu would have injected an increased fuel pulse width too early on say a long line set up.
If you move away from the syncro issues and do as you propose above, as I read it at 30bhp you intend to increase the fuel injector duty cycle by half of that of 50bhp.This will mean that although the nitrous is flowing 50bhp in a modulated burst into the engine,the engine will still be getting a burst of 50bhp of nitrous but the engine will only be getting HALF the fuel it requires.

On the pulsing of the soliniod its highly dependant on the soliniod and modulation frequency used.Theres a trade off in the minimum opening point ie you may set 20% but the soli may not open until 30% depending on the size and make of the soliniod and the mod frequency.Its a long time since I've looked at this but from memory if the mod frequency is high the opening percentage is higher but the accuracy and control maybe greater in the 30 to 70% range.If the frequency is low the minimum opening point is  lower but the contrl accuracy is not so good so 50% maybe not be 50% of the nitrous power if that makes sense?

[PetriK]

if nitrous pulsation is issue then it affects wet systems too, unless fuel is injected only during and only during intake valve opening directly to port.

Assuming there is no adequate mixing of fuel and air when using nitrous port injection or spraybar then this is something that is due to layerd air/nitrous in the port. With spraybar this could mean that there is not enoug turbulence in the intake - ie nitrous flow pattern is not deep enough.

Propably best to ask from spray bar designers how they are overcoming this potential issue as its not unique to controller.

With direct port injection sounds like no way to ensure proper operation of any nitrous controller. That is due to the fact tthat fuel will be atomize when hitting the walls and valve when pulse is not controlled to the valve opening timing.

Comments ?

[Gasabusa1]

if nitrous pulsation is issue then it affects wet systems too, unless fuel is injected only during and only during intake valve opening directly to port.

Assuming there is no adequate mixing of fuel and air when using nitrous port injection or spraybar then this is something that is due to layerd air/nitrous in the port. With spraybar this could mean that there is not enoug turbulence in the intake - ie nitrous flow pattern is not deep enough.

Propably best to ask from spray bar designers how they are overcoming this potential issue as its not unique to controller.

With direct port injection sounds like no way to ensure proper operation of any nitrous controller. That is due to the fact tthat fuel will be atomize when hitting the walls and valve when pulse is not controlled to the valve opening timing.

Comments ?

Quite a few of the Pro Mod bike wet nitrous setups I've seen run 100% fuel and do not pulse the fuel soliiniods at all.We tried spray bars in the early days and they can give irregular nitrous outputs when video'd and give more nitrous to one cylinder than the other,well they did on our log type,we found the best way for equal distibution is the shower head with an individual nozzles per cylinder.
We fuel the pulsed dry systems by putting the full power of fuel in and pulse the nitrous.We made 400bhp from a 190bhp aspirated engine like this,so 210bhp on nitrous.Its also how one of my friend bikes ran at Bonneville the other year he ran 38second on gas 15 times at 215mph like this so its reliable too.

[PetriK]

What I gather from this is that:
1) Spraybars are no no
2) To ensure even nitrous distribution the installation as far in front of the airbox is safest way with progressive systems
3) Someone willing to risk having uneven amount of nitrous when running a progressive system, then the shower head is best, but fuel should be tuned to the 100% nitrous duty anyway.

So far we have been running only 60-80hp from airbox without any problems. Have talked about the spraybars, but like described above not been convinced of those.

Is that so ?

[Gasabusa1]

1.This is only how we have found it,others may have a better spray bar.
2.I'm not sure that its better,the intake charge will still have peaks and troughs in the nitrous delivery on a progressive,like dropping a blue dye every few seconds in a fast moving stream of water.

In terms of where the gas goes in we had a bike with a nitrous injector in the floor of the inlet port and one in the bellmouth.The dyno pulls showed that the one in the inlet would be inefficient at high rpm and power would drop off significantly when compare to the same size nitrous jet in the inlet in the floor of the port,which would produce significantly more power at high rpm.Both had the same size jets so it was a fair comparison.These kits were large 150-220bhp plus hits on a 190bhp motor so we were pushing it a bit.
On a simple non pulsed 50-80 shot 2 injectors at the front of the airbox where the airtubes enter seems to be ok.On a smaller hit you maybe better to pull a lot of ignition and maybe progressive add that back in or on a drag application drop the 50shot on and set/tune the clutch/chassis to work with it.

My feeling after many years of working with pulsed progressives is that on bigger hits (150-220bhp)the pulsing is causing significant issues which I don't quite understand, but are the cause of quite a few blow ups.

Are there any timers in the ECU Petrik?

[PetriK]

Lets try to figure out also the big hit progressive optimum configuration.

Ecu operation is based on
1) interrupts that are detecting the crank wheel pulses. Basically we could set nitrous pulse to start at the moment the intake valve opens.
2) timers, particularly the main timer loop that reads sensor values (e.g. Tps) and then calculates limiters, map values and pulsewidth.

I am currenlty tapping all new functionality into this main timer loop which runs @ around 250Hz,which is the maximum resolution for solenoid control and e.g. Shift cut function.

I.e. Nitrous solenoid frequency is 250/25 = 10Hz, but can be set as well to 5 as 15Hz.

So its possible to time nitrous pulse with valve opening, but as the nitrous solenoid can not run that high frequency its not going to work in practise.

I understand the benefit of injecting nitrous to port, due to the cooling effect it will deliver more power than into airbox.

So what should we do ? Which direction to take for big shot systems ?

[PetriK]

ok, so if the problem is that the nitrous pulses when using solenoid dut control inbig shot installations cause nitrous charge being varying between different filling cycles.

Then we need just a simple pulse dampener, like an exhaust smoothening the pulses but not reducing the total flow.

This can be achieved by adding a volume canister into the line, a bit like exhaust dampener or vacuum dampener.

So this is a nitrous system design issue, not a controller issue . Surely someone designing nitrous systems must have thought this before ?

[Humble1]

Assuring that no matter what method used equal shots to each and all cylinders to me is the biggest priority ................. a spray bar that just relies on "blending" in the air box i would never use as it way to hit n miss.

[PetriK]

The next version could look something like this - any comments e.g. on missing key features ?