Use 65lb. Injectors I have, or purchase 85's?

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portmod7
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Use 65lb. Injectors I have, or purchase 85's?

Post by portmod7 »

I have a 5.7L small block Chevy with EDIS-8 ignition, a FAST EZ-EFI throttle body, and an MS-II running msextra code. I have been having some weird issues ever since I got this thing running, which has finally lead me to look a little closer at my injectors.

I originally purchased the throttle body of ebay, described as lightly used in FAST's dyno room. I thought it would have 85lb. injectors since that's what the EZ-EFI throttle body comes with and never bothered to confirm this. Now I am 4 or 5 years down the road and still haven't figured this system out and am finally trying to do some injector testing to get exact flows and deadtimes. I am new to fuel injection, and am learning all of this as I go. So if it sounds like I don't know what I'm doing, it's because I don't.

So I was doing some testing last night, rigged up on my vehicle using the injector test function of Tuner Studio. I found a nice spreadsheet to enter flow volumes at various test settings. 2ms opening time, 4000 cycles, 4ms opening @2800 cycles, etc. all the way up to 10ms. What I discovered, for one, is that the part number on my FAST injectors is 80527(65lb.). The second thing I discovered is that one of the four injectors flows A LOT more than the other 3, almost twice as much for every test. Doing a continuous flow test to fill up a 100ml graduated cylinder, this lone injector seems to be the only one flowing the advertised amount. And the third thing, the dead times aren't very consistent. Only two of the injectors seem to have reasonable dead times, 0.6 and 0.9. The other two are .02 and .04.

So I am not really sure how to proceed. My engine is the Fast Burn 385 crate from GM. I added 1.6 roller rockers, and put super thin head gaskets on it to get a compression bump. I figure maybe it's capable of 400hp. All the injector calculators I find seem to indicate I need around 63lb. injectors. The 65lb. injectors I have I believe are rated at 58psi, and I am only running 43 since that's what FAST says to run with this throttle body. So essentially they are 56lb. injectors at my pressure. So I thought about sending them somewhere to get checked out, fixed, cleaned, whatever, but I am not even sure they are big enough even if they can be repaired to work correctly.

So I guess after all that, my question is if I should work with the injectors I already have, or invest some money in bigger injectors? I am not sure what, if anything, can be done with the ones I have. And if I get new injectors, should I just go for the gold and get Injector Dynamics pieces, or would something more affordable serve me just as well? I intend on flow testing anything I get to come up with some accurate numbers to plug into Tuner Studio.


Thanks!
ewflyer
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Re: Use 65lb. Injectors I have, or purchase 85's?

Post by ewflyer »

Time to get mathematical, right? Figure out the duty cycle percent. Work out how long (in Milliseconds) at your engine's redline speed you will have to inject the required fuel. So something like 6,500 rpm: 1000 (milliseconds in a second) times 60 (seconds in a minute) divided by 6,500 should give you the time require for one 360 degree engine revolution, then that X2 will give you the full time to execute the full 720 degree 4-stroke engine cycle. Then figure out if your injector setup is fast enough to deliver the required fuel (with dead-time and something like 85% duty cycle taken into account). I guess the throttlebody setup might complicate the estimation a bit (with individual throttle bodies you just have to do an estimate for a single cylinder/injector).
portmod7
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Re: Use 65lb. Injectors I have, or purchase 85's?

Post by portmod7 »

So, the redline on this engine is about 6k. That would be 20ms. Now where I get fuzzy is how to determine if my injector setup is capable of delivering the right amount of fuel in that time..... Would that be the Req. Fuel number that TunerStudio calculates? I plan on running 4 squirts per cycle, alternating. That gives me a Req. Fuel of 8.2. Worst case scenario VE and MAP will both be 100 to give me 1's for the PW formula. Add 1ms of dead time to that and I am at 9.2ms. If I understand duty cycle correctly, that puts me at 46% duty cycle before any other enrichment?

No clue if I've understood any of that correctly, it really seems like I must be missing something. But if that's right, it seems like the injectors I have should work fine on my setup as long as I get them working properly?

If that's the case, and the size of the injectors I have now is acceptable, I guess the next question is if they can be repaired and where to send them? I could understand if they just didn't flow the correct amount, I would assume they were plugged up. But the dead time problem puzzles me. why would the dead time be ~0.03ms? I checked the resistance tonight, all were 12.5Ohms.

EDIT.....
I think the part I might be missing is that there are two banks of injectors alternating firing for 8.2ms each. So add the dead time to that, multiply by 2, and you get 18.4ms. That seems more reasonable and coincides better with all the injector size calculators out there. That would be 92% duty cycle. However, I don't see any reason why I couldn't up my fuel pressure to 58psi to get the 65lb/hour out of the injectors. That would put me at 7.1 Req. Fuel, and 82% duty cycle before other enrichment. Not really sure if I should cut it that close though.

Does any of that make sense?
slow_hemi6
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Re: Use 65lb. Injectors I have, or purchase 85's?

Post by slow_hemi6 »

I have the fast throttle body on my 351. It makes around 350hp at the fly maybe a little more, and is around 65% DC @ 6000rpm with pressure about 43psi. You should be able to fuel 400Hp with one quite easy.
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portmod7
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Re: Use 65lb. Injectors I have, or purchase 85's?

Post by portmod7 »

I agree, with the 85lb. injectors the throttle body is supposed to come with, no problem. But my issue is that mine has 65's in it for some reason. I bought it "slightly used" off ebay. It looked brand new, but evidently somebody changed the injectors.
portmod7
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Re: Use 65lb. Injectors I have, or purchase 85's?

Post by portmod7 »

Went ahead and took the 65lb. injectors to a local guy, Race City Injector. When I get them back I will bump the pressure up to 58-60psi and see how it runs. I think it should be ok.
slow_hemi6
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Re: Use 65lb. Injectors I have, or purchase 85's?

Post by slow_hemi6 »

What I am saying is the injectors they come with are 65lb/hr @ 43psi. I actually have mine @ 630cc in tuner studio settings. Makes for a required fuel around 7.1 and results in a VE map with numbers that seem good (sensible) to me.
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Cheers Luke
portmod7
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Re: Use 65lb. Injectors I have, or purchase 85's?

Post by portmod7 »

Ah, I see! Thank you for the info! I think it should be ok. I sure hope this all makes an improvement.
slow_hemi6
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Re: Use 65lb. Injectors I have, or purchase 85's?

Post by slow_hemi6 »

The way I run this throttle body is with a modified link arm that allows me to get about 1/4 primary throttle before bringing in the secondaries. The secondaries are also all in when primary plates are also 100%. The factory link was close at full extension but not quite enough for what I wanted and you also lost some secondary opening at full throttle. With this set up I use staged injection with one channel for primaries and one channel for secondaries. I use a stage points of 50% (TPS), hysteresis 5 and MAP of 80kpa, hysteresis 10 and have the injection at 4 squirts per cycle and tuner studio set as 2 injectors. Using 4 squirts vastly improves the idle quality as the fuel distribution is much better but it is also only possible because the staged injection halves the duty cycle when it stages to 4 injectors. If you try 4 squirts without staged and 4 injectors set then you find your idle pulsewidths get too small.
Find the Manuals up top under Quick links: Manuals. :RTFM:
Cheers Luke
portmod7
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Re: Use 65lb. Injectors I have, or purchase 85's?

Post by portmod7 »

Well, I got my injectors back. The report I got back from Race City Injector backed up what I saw when I started trying to test them. I got them back on the truck today and tested them. They all flow much better now, just not as identical as I had hoped. Is that the quality of the injectors I have, the quality of the cleaning they got, or is that just the way injectors are unless you have them professionally matched? When I tested them, I ran them for 7 seconds and ended up with flow rates of 64, 66, 68, and 77lb/hr @43psi in no specific order. I had deadtimes of .571, .458, .724, and .766ms respectively. Battery voltage corrections of .178, .169, .145, and .152ms respectively.

Since I had two pairs with similar dead times and voltage corrections, I paired them up that way on each of my two banks and entered two sets of deadtimes and voltage corrections in TunerStudio. I also put the higher flowing injectors diagonal from each other on my throttle body. I am running 4 squirts alternating and can idle it down to 500rpm if I choose to. Hopefully through all of that I have averaged out the difference as good as possible without having them professionally flow matched.

It runs better than it ever has, as you would probably expect. And with the good injector data, I hope working on my tune at all temperatures and pressures will go a little better now. I've had this thing running for 3 years or so now and have fought strange issues the whole time. I've never really solved any of them. But this exercise has made a world of difference for the better. I am optimistic that this is the main issue I've been fighting the whole time. Maybe I missed it, but in putting this system together and learning about this stuff, I never found one place in the "instructions" that told me to flow my injectors to get data on them. I sure wish that would have been in there somewhere, probably would have saved me a lot of headache. But maybe it goes without saying, and this is just another example of me being out of my element. But I am learning!
portmod7
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Re: Use 65lb. Injectors I have, or purchase 85's?

Post by portmod7 »

Well, that didn't take long. I got a couple good drives in, and it started acting up again. So, I rigged up my "test bench" again, same as before, and sure enough, my injectors are plugged or something again. When I got them back from the cleaner, they flowed 64, 66, 68, and 77lb/hr @43psi. Now, they are at 35, 43, 56, and 51lb/hr, respectively.

Could I have gotten the run around on the cleaning service? Could these injectors just flat out need replacing? Anything else anyone can think of?

My fuel system was all new 3 or 4 years ago when I started down this road. New aluminum tank, new Aeromotive Stealth 340 in-tank pump, new fittings, new lines, new in-line 40-micron filter, new pressure regulator. The only thing used was the throttle body rails and injectors. I have a hard time believing that there is that much crud in my fuel system, but I will investigate that next.

EDIT
Maybe I spoke too soon... Took a look inside the fuel rail end of the injectors, teeny tiny silver flakes. Pushed a paper towel down in there best I could to get some out, teeny tiny little silver flakes on my paper towel. I am guessing aluminum from when my tank was built. Wonder how much my fuel pump has liked eating that stuff? I guess it's time to drop the tank and completely flush the whole system.

One thing I do notice though, I don't see the filter baskets in the injectors? From everything I can find on the net, they should be pretty easy to spot?
bradyzq
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Re: Use 65lb. Injectors I have, or purchase 85's?

Post by bradyzq »

Hmm, I saw something similar once. The eventual determined cause was a fuel pump that was somehow machining itself to bits. The tiny metal flakes made it into every nook and cranny in the fuel system. It was a return system, so that meant the bottom of the fuel tank had a nice fine aluminum sandy beach.

Filter, pump, pressure regulator all had to be replaced. The tank had to be cleaned and the lines flushed well. The injectors were successfully cleaned in this case. It doesn't sound like you were lucky in that respect.

I'm not saying the pump is the problem in your case, but _something_ is eating metal in there.

Once you are certain that your entire fuel system is free of any and all crud, and any future crud-producing components, I strongly suggest replacing the injectors. It's bad enough that you're dealing with a TBI-ish setup, probably with differing fuel distribution among cylinders. Why make things even more complicated by throwing uneven injector flow into the mix?
Cheers, Brady
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portmod7
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Re: Use 65lb. Injectors I have, or purchase 85's?

Post by portmod7 »

Thank you for the insight. One thing about the whole situation is that it seems like something has happened recently that triggered me to look at my injectors. VE analyze live was giving me big numbers across my VE table, like all of a sudden my fuel system couldn't keep up. But, this project has been such a constant evolution, my parameters keep changing, so I thought it was something to do with that, so I kinda overlooked it. But looking back now, it seems like something has changed. I was thinking, or hoping that maybe I got a bad tank of fuel. My 40 micron filter really didn't have much in it, but obviously its not enough filter to keep the silver flakes out.

I already sent the injectors off to be cleaned again. I guess maybe that was a mistake. Any idea how to tell if my pump is the culprit? I guess the whole system will have to come out, what a mess. I have no idea how to even go about cleaning all the expensive parts, fuel rails, etc.
billr
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Re: Use 65lb. Injectors I have, or purchase 85's?

Post by billr »

Is the 40 micron filter between the pump and injector rail? I would think 40u would be fine enough to catch anything qualifying as a "flake", but I know how something very fine can reflect light and make it visible (think dust in the air in a shaft of bright sun-light).
bradyzq
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Re: Use 65lb. Injectors I have, or purchase 85's?

Post by bradyzq »

In my case, the metal shavings got so small that they could be called paste, at least what was caught in the fuel pressure regulator. It was more obviously metal shavings in the windings of the fuel pump.
Cheers, Brady
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Audi 200qa20v
Audi 5ktqa
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portmod7
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Re: Use 65lb. Injectors I have, or purchase 85's?

Post by portmod7 »

Yes, the 40 micron is the last thing the fuel flows through before the fuel rail. These are really small flakes, gotta have the light just right to see them.

Maybe I can take apart my regulator and see what's trapped in there to get a better idea of what I'm dealing with. That would be easy to do.
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