Jump to content

Problems staging injectors, engine in dyno now!


Recommended Posts

We are having problems getting the injector staging right on my  4 cylinder methanol turbo engine, I have 4 1680 bosch 842 injectors as primary injectors and 8 bosch 846 as secondary. All injectors have ballast resistors connected. The secondaries are wired in pairs.  We disconnected 4 of the secondary injectors so that we had 4 + 4 and then we set sec/pri ratio to 1 and got it working perfect, but with all 8 connected on the secondary with sec/pri ratio 2 the engine runs lean when it has staged the secondarys in.  Here is my settings:




Please help I need to get this working soon!!

Link to comment
Share on other sites

I havn't really paid too much attention to what is going on here.  But here are some points to note:

Putting injectors in parallel does not change their dead time.

Putting a resistor in series (with one or two injectors) does alter (increase) the deadtime as the effective applied voltage to the injectors is lower. 

At 14 volts battery voltage you have 1 amp per injector (two 5 ohm injectors in parallel in series with 4.7 Ohm).  1 Amp will be enough to hold the injetcors open but may not be enough to open them if high fuel pressure is used.  Consult injector manufacturer data sheets for an answer.

The pri/sec ratio is a flow ratio.  Claculate the total flow from your primaries (at the used fuel pressure) and secondaries and work out the ratio using the equation given in the help.  I dont think 2:1 will be correct. 

Link to comment
Share on other sites

Just read through this whole post again and you are using two different types of injector the 842 was designed by bosch as a cng injector designed to operate at 1 bar pressure with gas and yes can flow 1680cc at 3bar on petrol

the 846 injector is a methanol injector and flows 1680cc but that is at 100% duty cycle ie hard on

the flows at lower duty cycles could be quite different between the 2 types you would need to run them on a flow bench to confirm this and this would have quite an effect on how they staged



[email protected]

Link to comment
Share on other sites

because I don't have any more resistors and have to order them in that case and have to wait for them before we can run the engine more on the dyno, that's why I want to know if this is a problem with the resistor or if it is a problem with the settings. But you say it's the settings?

Link to comment
Share on other sites

We had an 'injector dyno night' tonight. We hooked up a computer with a Signal Generator to the triggers so that we could run the injection without starting the engine. Then we mounted a fuelrail with 1 '842' injector and 2 '846' injectors. First we ran at 3mS dutycycle With one 842 and one 846, each serial connected to 4.7ohm resistor they gave exactly the same amount fuel sec/pri 1:1. So they are the same size. Then we parallel connected 2 '846' secondary injectors to 4.7ohm resistor. Sec/Pri ratio 2:1  still running 1 '842' on the primary with 4.7ohm, We tried to spray about the same amount in the bottles each time. We had 411gram in the primary bottle, 284+266 in secondary bottles=550. 411x2=800  800-550=272grams too little coming out of the secondaries! Way off... Now we parallelconnected 2  4.7ohm resistors on the secondaries so we had 2.35ohm in series with the 2 secondary injectors. This time we had only 47grams too little in the secondary bottles. We then increased the deadtime +0.1 and now we had exactly double amount coming out of the secondarys. So the we increased to 10mS dutycycle, now we had 45 grams too little out of secondarys. Adjusted back deadtime to standard setting and adjusted sec/pri to 1.9 and had 16 grams too little, so thats pretty close to the truth. Tried same settings with 3mS dutycyle and had 7 grams to little.

So now I'm only waiting for my new resistors and we'll get the engine running as it should!

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Create New...