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Discussion Starter #1
Hey guys, just got back from a best-effort tuning session to try to get some street manners out of these 160lb/hr injectors and did a few WOT pulls as well.

The good news:
The car makes 600ft-lbs/[email protected] (SAE, rear wheels) at 11:1AFR with only 16deg total advance on piss gas with the graph showing indication that the spark is far from optimal. And, it looks like it barely reached peak torque (we think). With all that retard it may come later though. This shows promise for being able to hit my 1000fwhp (850rwhp) dream.

Matt Robison came out unexpectedly; that was a pleasant surprise, thanks for making the trip Matt, nice to meet you!

The bad news:
Drivability sucks; the 160's simply won't cut the mustard at cruise. The pulsewidth is so small (1.0-1.3ms) that I'm flirting with the injector offset vs battery voltage function which is causing the tuning experience to be a lot like trying to balance a ball on the point of a pin. Once you crack the throttle open and get off the injector offset floor, they behave linear. But down in the closed throttle region, they are far from linear and far from reliable.

Maybe they'd work better on a bigger engine or a drag-race only deal; but for something I want to enjoy on the street and road course, this isn't going to cut it. Getting beat to death just driving down the freeway is not terribly pleasant.

I tried locking the fuel pressure and eliminating the bypass valve from the equation...neither helped. I tried everything between 24 and 40deg of part throttle spark; didn't care. I can get it to idle nice/lean, and can get the drive tune close...but it still bucks and heaves and acts snotty and suffers from calibration drift regardless. In fact, with the throttle constant, the mass flow constant, fuel pressure constant, and the injector pulsewidth and spark advance from the EEC constant, the engine rpm will surge up and down at cruise all the while swinging the air/fuel ratio between 17:1 and 11:1...which can only be caused by fuel. I really don't know if it's the injectors themselves or the driver box...but I'm going to take an educated guess that it's the injectors. I know for a fact that the minimum pulsewidth it takes to get one open is somewhere around .8-1ms when the injector is cold. I made a test jig and tested this on the bench with 40psi of fuel pressure on them. Since my cruise pulsewidth is only 1.3ms...I bet that is the problem. I'm trying to work with 0.3ms of pulsewidth and the injector offset probably moves around a little due to heat, voltage, etc, making it a very hard target to hit indeed.

Anyway, as you can tell I'm frustrated.

Next step; order up some 83lb/hr siemens dekka injectors and give it another go.

Car sounds great a WOT though and sounded like things were just getting good when I hit the purposely low-set limiter. The fuel system seems to be cutting the mustard, the dash system worked as planned, so all in all...not a horrible day. I found a new oil leak (back drivers valve cover) and oh yeah, the 20w50 did the trick in the oil pressure department. I was seeing 60+psi of pressure at 5K, and 25+ at idle, hot. Additionally...with all this beating on it and no supplimental fan, the hottest the engine ever got was 170deg F. Apparently my cooling system is sufficient. :)

That's all for now, more later as I get the bitch to run right.

B
 

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Discussion Starter #2
Oh yeah, and...

Oh yeah, and before I forget...

I know I posted before that I had logger data that showed it was making 750rwhp at a similar rpm at half throttle. The logger bases the horsepower estimates based on mass air flow, and a "good guess" regarding engine efficiency and drive train losses.

It's pretty accurate if the engine is tuned, but mine wasn't...and because I had the MAF curve wrong, the logger data produced an artificially high number.

And, as I learned today, my throttle is large enough (flows 1600cfm NA) that half and full throttle are essentially equivalent because I'm flowing pressurized air I suppose. I made similar power/torque (within 70-80hp) at half throttle vs WOT in that rpm band.

So learned that the logger was probably off by 50-100hp due to maf error, and WOT vs 1/2 throttle when the throttle is giant doesn't matter much...too bad, was hoping for more power! (don't we all LOL!)
 

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Discussion Starter #3
Tuning 160lb/hr injectors...

So after digging through a bunch of data logs from today, I think I have some reasons why these 160's are being such a pain in my *** to tune. I'm going to ramble on about it a bit in hope that it may help someone in the future.

Above 2.0ms injector PW, the AFR cleans up and things are linear like they should be.

Fords data on these injectors suggest that he minimum reliable injector pulsewidth for operation at the nominal 39psi Ford recommended pressure is 1.6ms.

In looking at my logs, my normal idle and cruise PWs when the AFR is correct, are well below this number...which corresponds to wacky AFRs, and whenever above this number, the AFR is consistent.

Furthermore, in looking at the injector offset vs battery voltage function, it's clear that ford has wrestled with this injector in the 13-15V battery voltage range and depending on the drive voltage, the offset varies by as much as 30% in the 13-15v range alone. I did nothing to compensate for this offset issue. I should have.

Because my PW is so small, this effect is even more dramatic. This may explain another reason why I'm seeing big AFR swings just off idle.

The only way I can get the PW above 1.6 reliably (based on log data and napkin math) would be to drop my base fuel pressure to 20psi. If I do that, these injectors effectively become 90lb/hr injectors which would require a 2+ms PW at idle/cruise, and that would probably work to solve the first problem. It would make life easier on the fuel pump as well; and give me more headroom. However, what about feed line size? If I cut the pressure in half, then my -10 feed line no longer conveys the same amount of fuel. Anyone have a guess at how much power you can support through a -10 at 20psi? Enough for 850rwhp?

Seems to me that I may go ahead and confirm this in the name of science at idle/cruise, but it would probably be smarter to run the Siemens 83lb/hr injectors at 39psi than start deviating from the norm and guessing about fuel delivery capacity at 20psi in an EFI setup. As you know, lean at the top end on a supercharged combo is a good way to make a mess. I'm not *that* interested in knowing if it can be done. :)

Byron
 

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Is there any way you can reference vacuum to the pressure regulator at idle/low engine speeds to reduce your fuel pressure at these speeds? I don't know if your engine is experiencing any boost at these rpms so I'm just speculating that it's even possible to do this. Or is this old news?
 

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I am almost certain I had read somewhere (GFUB maybe?) that the largest injector a stock A9* series could control was 113lb/hr. Though it might have come up in conversation with Dale McPeters and Clint Garrity.
 

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Holy crap! this fuel injection science stuff is too confusing for my last surviving brain cell, he's about to burst into flames from just reading about all that's involved. :? :lol:
 

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Discussion Starter #9
Comments

Moparman:

Yes, the regulator does reference vacuum and has the effect of pulling about 5-7psi of fuel pressure out at idle. To get it to pull more, I'd need a custom regulator. Additionally, the transition from 20psi to 40psi would be abrupt as you open the throttle; I'm not sure that would work out in the end.

ScottJackson:

NEVER! lol

White90GT:

Correct, I got around this by dividing the injector size/slope by 2, dividing the MAF curve by 2, and adjusting load with engine displacement. The calibration itself isn't a problem, I can turn down the delivery to the point the engine is too lean...the problem is resolution/control at idle/cruise; it just isn't good enough. Get the injector above 2ms pulsewidth and it's wonderful.

Dilligas:

It's enjoyable, actually...but you have to be willing and at times like this it seems more annoying than beneficial; agreed.

Monstermiler:

The spray pattern already sucks at 40ish psi (squirts in a straight beam, nails the opposite side of the runner). Most injectors above about 40lb/hr have no real "atomization" properties, unfortunately. At 20psi, I think I'd have a sucky spray pattern as well as potential fuel delivery unknowns. I have no idea what my pump/lines/rails do at 20psi and it just doesn't seem like a good idea to muck with that when 83/86lb/hr injectors are doable, and big enough for the job at hand. I'm just a little disappointed I couldn't master the 160's. On the bench test, they looked so promising. I guess now I know why I only see them in drag cars.

Thanks for the help/ideas guys,

Byron
 

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Byron I was hoping to see you get those 160s going.
Since you are having to change injectors, check these guys out.
Notice this guys list the response times and all the specs to help you out.

A set of Flow matched 79lb HiZ, yes they are expensive but eliminates the injector driver. These have a cone spray pattern which should help.
http://www.racetronix.com/01D129xFM.html

They do offer a 120lb set that has a cone pattern as well.
http://www.racetronix.com/INJL120.html

Here is the Siemens 83s in a flow matched set. They have a pencil type spray pattern like you have now.
http://www.racetronix.com/3105FM.html

Also Moran has introduced an adjustable injector. I have only seen pics of it so don't know a lot about it yet.
 

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Discussion Starter #11
Yep...

He's helped me with injector data in the past, so it's time to do some business with him. I just ordered the Siemens 83s.

And, while I'm waiting, I'll play around with the 20psi of fuel pressure and new calibration parameters I've developed for 20psi. However, I'm not inclined to WOT pull it with 20psi....that makes me nervous.
 

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What about a voltage reduction to the pump based off of TPS input. At idle, have the pump voltage reduced by 50% to affect the Pressure differential, then as the TPS trips anything above 1% open your back to full voltage at the pump.

I know several of the high end carb pump manufactures have come out with voltage reducers to prolong high volume pump life for street use cars.
 

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Discussion Starter #13
Yep

I have a PWM controller on the pump that varies pump output based on throttle position. Trouble is, a conventional fuel pressure regulators job is to regulate pressure regardless of pump output...and that's what it does.

I'd either need to reinvent the returnless fuel system with a pressure feedback sensor and build a very complicated controller to make what you suggest happen...or design a regulator that has a 20psi swing based on manifold vacuum.

And, once I'm done, deal with trying to make a calibration that can somehow mask the effects of having the fuel pressure swing 20psi sometime between cruise and wot while not sacrificing driveability.

Honestly, I think the reasons for continuing with the firehose injectors are diminishing rapidly...there's a much simpler path and it's $500 away. I think I'd spend another summer trying to fight it...and I'd rather be driving.
 

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Byron,

Two more cents: what about a fuel pump speed controller that is RPM controlled?

I use this one: http://www.aeromotiveinc.com/products.php?cat=4&catsub=0&prod=31

Mainly, for me, it keeps the fuel recirculation slowed at <3000 RPM so the fuel temp doesn't get too high when I'm idling for long periods of time. The activation RPM is adjustable.

Might it - or something like it - help your BIG injectors behave?

Tom
 

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Discussion Starter #15
I don't believe so.

Regardless of fuel flow, the regulator supplies the back-pressure. You'd have to slow the fuel flow down so much that you were below the flow range of the regulator...and then you'd have unregulated pressure.

I could make my controller rpm based as well...I don't see how that would help. An electronic fuel pressure regulator that changed the pressure based on RPM would work, but without some input to the PCM for fuel pressure you'd still have a bitch of a time tuning it. The PCM wouldn't know when the fuel pressure changed. Basing it on RPM would be better than TPS though; if you did want to do this.

What you'd need to run these injectors is a 700+" engine that needs more fuel at idle/cruise. Maybe next time. :)
 

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Would it be possible to run a dual injector setup? At low engine speeds it feeds off one injector and at WOT it gets an additional fuel boost? And perhaps only four large injectors in the plenum area spraying fuel towards two runners? I'm thinking along the lines of an enrichment injector like some older fuel injected cars ran for cold start. At least I seem to remember reading about a setup like that. You are probably right though. If you can run the smaller injectors and still make the power you want, then that is undoubtedly the best way to go.
 

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Byron,

Regardless of fuel flow, the regulator supplies the back-pressure.
That is logical.

Yet, when the controller throttles the pump back, I see the pressure drop from 43.5 down to about 30 psi. When the engine speed goes over 3000, it pops back up to 43.5. I'll have to check where the pressure gauge sender is located and get back to you.

Tom
 

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Discussion Starter #19
Wow

I've never tested a bunch of regulators, but apparently some aren't as flat in regard to fuel flow as others! So, your regulator isn't vacuum referenced and that change in pressure isn't based on engine vacuum?

If I could find a regulator that had a response curve like that and tuned it based on RPM, I could *probably* compensate for it in a fuel table by tweeking the respective values versus rpm. What would really suck is to develop that tune, have the pump wear a little, and have the whole fuel curve move.

Seems to me you want a regulator to regulate regardless of flow in an ideal world, which is what my big purple magnafuel regulator appears to do. It doesn't drop off until you get around 40% duty cycle (5V range) at the pump. It's perfectly flat from 5V to 15V.

That said, if you're not running firehose injectors, 10psi of fuel pressure fluctuation isn't *that* big of a change in resulting AFR. A 42lb/hr injector at 50psi is a 46lb/hr injector...9%. If the target AFR was 14:1, you'd end up at around 13:1. The effect on a 160 is 4X greater....you'd end up at 10:1.

So, a couple PSI is a big deal. This doesn't sound fun to tune. :(
 

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bds

Have you checked into BDS efi stuff? They have an eight injector plate that is capable of 1200hp.

I have looked a buying the complete system, but I have heard its a pain to tune if your not computer savy.
 
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