Injectors

[DominusEtDeusNatus]

With all this fuel talk lately and injectors I though I'd post this now. I might add that to my sig once I get some free time to organize it clearly. For the time being here is some info.

http://teamzr1.com/injdc.html

Here is a nice chart. They used this formula to get it. At 6000 rpm, the time between firing cycles would be 2*60/6000 or .02 second or .02*1000=20 milliseconds. Everyone is shifting at 6000 currently so let's just concentrate on that.

Above 90%, most pintle style injectors start to wildly fluctuate their actual flow rates independant of the pulse width. The spray pattern can also break down and fail to atomize the fuel spray properly. Plate style injectors (ie Lucas) are much more reliable at persistant high duty cycles.

According to last autotap I'm at 18ms i.e. 90% at 6000. I'll have to re-autotap and log the whole RPM range.

Stock LS1 injectors are 28(98,01,02) and 26(99,00). You could use those.

Injector tips vary also. Some injectors will spray a cone patteren and some spray in a steady stream.

Some samples. 250hp at the crank NA.

1. Brake Specific Fuel Consumption desired =.50
2. Max duty cycle = .80
3. Fuel pressure @fuel rail = 50psi(I think that's what the Walbro puts out)

Using those numbers I get 24.29lb/hr.

Let's add some drynitrous. 100shot on a stock engine and on the above engine.

300hp, 350hp
1. Brake Specific Fuel Consumption desired =.70
2. Max duty cycle = .80
3. Fuel pressure @fuel rail = 50psi(I think that's what the Walbro puts out)

40lb/hr and 48lb/hr. Seems high, but remember that compared to V8 guys we need more flow since it's only 6 injectors supporting the same hp as 8.

For those supercharger guys. They shoot for 300rwhp so 375 at the crank for autos.

1.BSFC = .60
2.max duty = .80
3.50psi

Comes out to 44lb/hr.

You can get your exact BSFC if you dyno your car and know the fuel rail psi, injector size, and max duty cycle.

So much stuff thrown in here in no particular order. You guys can figure it out.

[Magnus]

Dry nitrous kits increase fuel pressure by feeding nitrous pressure in the vaccum line on the FPR pressing the diaphram closed.

I'm not sure exactly how much pressure is increased though.

[DominusEtDeusNatus]

_________stock___HC
50 psi___40______48
80 psi___32______38
100 psi__29______34

Dry nitrous shot just doesn't seem like a good idea on stock injectors.

For some reason spaces aren't recognized so I used underlines.

[ May 10, 2002: Message edited by: Dom ]</p>

[John_D.]

Ok, I've been prowling through the injector related posts, and there is some spotty information, and it looks like the board got smarter over the last few months. So I'm looking for the latest and greatest feedback on my situation.

I'm running lean at WOT with an 85 dry shot. The fuel pressure goes up to 60, from 42, so that part works ok, but the o2's are still way too low.

I may be able to richen it up with the maft, but then I'll be too rich for n/a driving, and I'd rather not have to switch the maft back and forth.

So I'm looking at putting the kenne bell boost-a-pump on, wired to the nitrous arming switch and wot switch, so I only get the bumped up pressure when needed.

Also thinking about bigger injectors, but not wanting to run rich when n/a. If stock are 22 (21.6), then the 24 lb injectors would be about 10% bigger? Less than wot would adapt to the injectors, but would probably still be rich at n/a.

Trying to stay away from exceeding the recommended duty cycle of the injectors as well.

And finally, I need to be thinking ahead about the s/c kit. I believe it comes with an AFPR, so I'll have more fine-tuning then, but I may still need more volume to keep the pressure up, so I think the boost-a-pump will be good for both the s/c and nitrous, and in combination...

So, any feedback on injector resizing vs. further fuel pressure increases vs. maft adjustments???

[Ironman24]

Fuel and injectors has been a big problem for me lately. My latest solution is LT1 24lb injectors with the MAFT at 10% lean and a inline fuel pump. At WOT O2's are in the .91/.89 range and fuel pressure is around 55psi. (this is with 6lbs of boost) I ditched my FMU because it was boosting fuel pressure up too high and locking up the injectors. My injector pulse widths are still in the 28ms range but better than they were at 32ms. So I'm not at ideal duty cycle but I'm getting the fuel I need. I'm considering going bigger on the injectors since I should be pushing around 300 at the wheels and even more with the nitrous. But I'm not going to a larger injector unless I can get some programming for it. Down low the car is very rich with the 24lbers.

[John_D.]

Ironman, is your fuel pressure higher all the time, or only under boost? I'm thinking about the 24 lb'rs, but not so sure if they are going to richen me up too much at idle.

[Ironman24]

My fuel pressure goes from 40-44 to 55 under boost only, but that is because of the inline pump not the injector size. With a stock pump your fuel pressure shouldn't change much going to a 24lb injector.

[John_D.]

<blockquote>quote:</font><hr>Originally posted by Ironman24:
My fuel pressure goes from 40-44 to 55 under boost only, but that is because of the inline pump not the injector size. With a stock pump your fuel pressure shouldn't change much going to a 24lb injector.<hr></blockquote>

That's what confused me about your earlier comment "Down low the car is very rich with the 24lbers."

I thought you were probably running stock pressure down low, but wanted to make sure.

I'm trying to anticipate what results I would probably similarly have with 24's (since my fuel pressure also stays 40-44 unless the nitrous fp regulator kicks it up to 60).

[Ironman24]

My advice is to wait and see if Keith can program bigger injectors. Unless you have a MAFT and can lean out the base until you can get a custom program. Even with the base at 10% lean the computer is still trying to pull out lots of fuel in the low rpms. My LT's are around -23 at cruise.