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Extra Injector.Will this work well on DSMs???

4K views 25 replies 18 participants last post by  Jehu 
#1 ·
http://www.thedodgegarage.com/turbo_extrainj.html
I want some sound technical reasoning as to why/why not.
I'm trying to build a car to GrassRoots $2002 rules so cost is the main factor here. So if anyone knows or has seen this kind of set-up in action then please tell me.
 
#2 ·
i have 4 saab 900 cold starts waiting. i need to do some other things to the car before i install 1 or 2 of them though. clutch,various gaskets, sturts/springs tbelt oil/water pumps :eek:

yes it will work on a dsm, and if your goal is to do something as cheaply as possibly this is the way.

IB someone calls it a bandaid approach/dumb.
 
#3 ·
I have a fifth and sixth injector setup on my Daytona. The whole project took 50 dollars. 40 for the pressure switches, and 5 a peice for the Saab Injectors. I had some spare wire and electrical switches lying around. I don't know the specs of the injectors, but i do know, with just one turned on i can push 22 psi no problem, and 28 with the 2nd activated. Without the two extra injectors the car would detonate around 18-19.
 
#8 ·
It will work and has been done. It's the cheap way to do it, but it does work. Ever hear of an AIC (additional injector controller). As far as running 28psi on pump gas, safely, you're dreaming. You can put dual 450cc injectors in your car with a stock 14b and it'll still be inefficeint at 20psi. It will run gas out the exhaust though. I've seen it happen with set of 92lb injectors. Putting a set of bigger injectors in will do the same thing and be safer. You need octane to boost high safely.

David
 
#10 ·
try getting the witch from turbonetics (cost about $50) and is switched by boost pressure and is adjustable. this is a good way to get AI to come on.
if not comfortable with this way haltech always makes the F5 or 9 that will cost you under $350 :cool:
or hks has the 1100 unit.
 
#12 ·
Don't forget the turbo Dodges use a speed density system and cannot make changes in the A/F ratio when you mod them, that's why the extra injector trick (developed by Gus Mahon) is needed. DSM's really have alot more options available to them as far as mods go, but if your really bucks down you can try it.
 
#13 ·
This might sound stupid but at least read it til the end...When I was running NOS on my first car I learned how everything really worked...with this being said...Now that I have a talon I want to run more boost like everyone else right :D so I was thinking if I was to put the fuel part only of a wet kit on my car with a boost switch to activate the solenoid that would automaticly five me more fuel! right! I'm just not sure how to calibrate de hole thing...Now I'm not saying that this can be done but I might try it...


For those of you who don't understand...the wet nitrous kit includes 2 indentical sides one is for the N2O the other is for the fuel...the N2O side goes to the N2O bottle the other goes the the fuel system( "T" or Y connector from the filter or connected to the fuel rail) it connects in front of your TB and sprays nos and fuel to compencate....so if you only use the fuel it would only spray fuel now you can jet that injector as you wish...


Anyway flame if you will it's farely early so....take some and leave some!!



later
 
#14 ·
CheapSpooler said:
This might sound stupid but at least read it til the end...When I was running NOS on my first car I learned how everything really worked...with this being said...Now that I have a talon I want to run more boost like everyone else right :D so I was thinking if I was to put the fuel part only of a wet kit on my car with a boost switch to activate the solenoid that would automaticly five me more fuel! right! I'm just not sure how to calibrate de hole thing...Now I'm not saying that this can be done but I might try it...


For those of you who don't understand...the wet nitrous kit includes 2 indentical sides one is for the N2O the other is for the fuel...the N2O side goes to the N2O bottle the other goes the the fuel system( "T" or Y connector from the filter or connected to the fuel rail) it connects in front of your TB and sprays nos and fuel to compencate....so if you only use the fuel it would only spray fuel now you can jet that injector as you wish...


Anyway flame if you will it's farely early so....take some and leave some!!



later

Yes, it will work. I can run my NOS wet setup without opening the bottle and it just sprays the gas. Seems kind of risky, but I have done it before by accident.
 
#18 ·
the whole point of hacking 1 or 2 extra coldstart injectors is to do the job as cheaply as possible. why get an emange when for the same price you could get larger injectors and a used S-afc?

btw i though the emanage only controlled cyclic injectors, not non cyclical cold start injectors?
 
#20 ·
The reason DSM have used the extra injectors is bc the stock system could not supply enough fuel even with 720's. More gas wont reduce intake air enough to run higher PSI. Make your own water injection system youll be about to run 25+ psi on pump gas. It should cost $200 and is worth the money it you concider the alternative is buying a larger turbo and intercooler for over $1000

Gus Mahon - R.I.P will be missed.
 
#22 ·
To run extra injector(s) you will need a rewired aftermarket pump, especially at high rpm/boost. If you are looking for high boost for cheap, why not just use a B&M Commandflo afpr from RRE for $65 in conjunction with a rewired 190lph (which you would have needed anyway) and run 43psi to start which puts your 450's at their rated flow instead of the 415 they flow at stock fuel pressure? Then you have fuel pressure adjustability, which you also probably needed anyway, and can turn it up to 50 or so to turn the 450's into 485-490 equivalent injectors. Granted, that may put you rich at lower rpm's but I think the ECU will compensate some by narrowing pulse width.

Then, run the injectors at 24-26 ms to keep it rich enough- Todd Day of TMO advises he has run as high as 27ms without problems. Going to 27 is a 33% increase over the normal 20, arguably turning your 490 equivalent flow to 650! At least that's the theory- the trick is getting the ECU to run that long of a pulse width- I have not figured that out yet... Maybe someone has tried this, although I suspect I may have to be the guinea pig on this one.

Water injection is a proven technology, but not cheap in most instances, from what I have read. Erik is currently testing propane (~$350) and will give an update soon. Most importantly, the thing we already know, race gas.
 
#24 ·
The injector on time has relevance only when RPM is considered. 27ms at what RPM? Assuming that the injector stays on for all 4 strokes and not just the intake stroke (I believe that's how the fuel injection on a DSM is setup), at 7000RPM you will only have 2 revolutions, i.e. 17 ms to fire the injectors. If the injectors only fire on the intake stroke, then it's 4.3 ms.

There are lots of methods of getting the computer to run a different pulsewidth...AFC, AFR, DSMlink...etc i.e. FUEL COMPUTERS! Unless if you can remap the ECU, there's no easy way of changing injector pulse width i.e. fueling. Unless if you consider a rheostat on the temperature sensor a viable alternative.

An additional injector on a MAF equipped car will only be of benefit when the airflow exceeds the computer's ability to add fuel, i.e. the ECU starts asking for +100% injector duty cycles. If you think you will be approaching that point, then yes, an additional injector will benefit you. For my car that point is reached at about 236 grams/second of air flow, with stock injectors.
 
#25 ·
Jehu said:
The injector on time has relevance only when RPM is considered. 27ms at what RPM?

There are lots of methods of getting the computer to run a different pulsewidth...AFC, AFR, DSMlink...etc i.e. FUEL COMPUTERS! Unless if you can remap the ECU, there's no easy way of changing injector pulse width i.e. fueling. Unless if you consider a rheostat on the temperature sensor a viable alternative.

This is what Todd Day was speaking of re: 27ms pw:

"One might think the max amount of fuel an injector can squirt into the cylinder would be limited to the time that the intake valve is open. But that is a very short time relative to the entire four-stroke time that is really available. The injector can squirt fuel onto the back of the injector while it is closed and let it pile up there. This is actually done almost all the time at RPMs over 5000 (maybe lower, too) and is the reason why the intake valves get all crudded up over time with an accumulation of carbon. This is also why you should check and clean your intake valves occasionally.

Anyway, if we decide to use all four cycles of the engine and call that the max time period, we need to find the period of four cycles. That is simply equal to 1/RPMs times two, because it takes two rotations of the crankshaft to complete four cycles of the engine (1/RPMs because period is the inverse of frequency).

An example - what is the time available for the injector at 6000 RPM? Now, charting the time in terms of minutes just isn't convenient, so we first convert RPMs to rotations per second.

6000 RPM = 100 rot/sec

Inverting and multiplying by two, we get

0.010 seconds * 2 = 20ms

So, at 6000 RPMs, the time available to your injectors is only 20ms. But that isn't the whole story - it gets worse. There is a thing called injector dead time. This is the time it takes for your injector to respond to an "open-sesame" command from the ECU. It gets complicated because this time varies with the voltage at the battery. The ECU has a lookup table of dead-time vs. battery voltage and really is the main reason the ECU looks at battery voltage in the first place (there are other less important reasons). This time can range from 0.65ms to 2.1ms. Anyway, you have to subtract this from the time available to get the true time available to the injector.

Note: subtracted from this dead time is the time it takes to turn off the injector. But, when people talk of injector duty cycle, they never include this time. Well, they do, but they say things like, "Never run an injector over 80% (or 90%)." But such a thing is really kind of silly to say, as duty cycle is a ratio that doesn't take into account the times involved.

For example, would you want to run at 90% duty cycle at 2000 RPM?

1(2000/60) * 2 = 60ms

90% of 60ms = 54ms

Now, 54ms of fuel would probably be ridiculous for most applications. But I'm just using it as an extreme example. 54ms would probably also burn out the injector - I do not think you are supposed to keep them on that long. They do have a limit. You need to watch for that, too.

It just so happens that at 6000 RPM, 90% gives you 18ms, which leaves you 2ms of available "dead time", which is probably a good thing. At 8000, you only 15ms available, so 90% gives you a paltry 13.5ms (dead time of 1.5ms still probably okay on a good battery).

Of course, what is missing from this is what does 13.5ms mean, in terms of fuel? Not easy on the first generation, because 450cc/min injectors are further derated by the 1G low fuel pressure. That 450 rating is at 42.7 psi, not the 36.3 psi that the 1G fuel regulator uses. 450cc/min * sqrt(36.3/42.7) = 415cc/min injectors! Multiply this by 13.5ms = 0.093375cc of fuel. You need to figure out if this is enough for the air you are pushing through the engine.

Multiply this number by, say 11:1 A/F mass ratio and the mass of 1cc of fuel, and you get the mass of the air this amount of fuel will support. Now, if I had a way to flow-bench the MAF, I could figure out what the actual air-mass/sec rate is, and I could log it. And you could figure out if you are getting enough fuel into your engine to match the air.

Either that, or you could look at your O2 sensor readings!

BTW, by using the injector pulse width number along with the RPM value, I should be able to produce a nice duty cycle plot. I will add this data type in the future. But keep in mind what it really means. Personally, I find pulse width a hell of a lot more useful because it directly correlates to the amount of fuel entering the engine - duty cycle does not. -todd-

I have personally run my 450s on my 1g up to 27+ms and have a calculated duty cycle of 130% from 4K to 7500rpms. This seems confusing but it works."

When you talk about a rheostat, I presume you mean the "old school" mod of a 10 k potentiometer on the IAT wire?

When Todd ran the 130% duty cycle referenced above, I guess fuel was "puddling" or backing up behind each intake valve while it was closed- how else can one get 130% duty cycle? This is what I have read on this-

"the injector is pushing fuel for far longer than the valve is open. At this point, the question is moot. To have enough fuel to make power in this region, it must store fuel by puddling it on the
valve and waiting for the inrush of air to finish mixing it. When it
stores it there is of no consequence."

What do you think of the effectivenss and/or wisdom of this?
 
#26 ·
Yup, that was what I was refering to when I said the injector could fire for all 4 strokes of the engine. The point I am making is, (using todd's numbers) if the event (4 stroke cycle) is only 20ms long, what's the advantage of having an injector hanging open for 27ms? That means it's "cutting into" the next, stroke, so it's just open all the time anyway, i.e. no difference from having the injector open for 20ms right?

That's the point I'm making 27ms has no significance unless if you're talking a specific RPM range. It sounds almost like, as an experiment, he's setup his injectors to fire a constant 27ms regardless throughout the 4k to 7.5k rpm range, which means duty cycle will go up as RPM goes up. In that case, is 130% duty cycle more effective than 101% duty cycle? I don't think so. If your injector is full open, and the computer calculates duty cycle based on available time over a 4 stroke cycle, there is physically no other way for the injector to add more fuel without increasing fuel pressure or injector size.

The only time it would make sense to go >100% duty cycle is IF the DSM ECU only injects fuel on the intake stroke, but AFAIK DSMs already inject over the entire 4 stroke cycle.

Yup, I'm refering to the old school hack that has recently been selling on ebay as a "timing increase chip". :rolleyes:
 
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