The holley unit's that come with the HSR and Commander intakes are 1:1 unit's right?

I think my math is right, you tell me for a 6psi boost combo and 30# injectors:

rail pressure at baro (100kpa) 43.5psi
holley regulator 1:1 = 6psi so 49.5psi now
4:1 vortech FMU = 24psi added so 73.5psi

A 500 crank horsepower motor with a .55 BSFC, and 90% duty cycle would need
38# injectors at 43.5psi, or would need 71psi to run 30# injectors (assuming a pulsewidth of 90% DC).

I want to run the lower base pressure so I can run longer pulse widths at idle and still support higher fueling at WOT.

-- Joe

 

It depends. Is the Holley AFPR before or after the FMU? You need to know this for the multiplier effect.

I run ford green tops 42#/hr high-z with a stock 730 ECM and modified AUJP code. The engine is a 355ci, 993 heads, 216@.050 I/E cam, LT1 intake. Everyone says that the Ford injectors are junk and don't work at low PWs. That is only true if they are not tuned properly and one uses poor fueling code like the $58 code. The AUJP fuel code is much better at controlling idle. The engine with the Ford 42's idles as well as it did with the GM 24's it had in it before.
The calcs for my engine & turbo setup comes out to about .58 BSFC in case you were wondering.

EDIT: I gave the long 42 #/hr story in case you were thinking of going larger (cheap) injectors.

 

Joe,

I think you will need to subtract the 6 psi that's in the manifold for use with the injector flow calculations.

Your effective fuel pressure (pressure difference across the injector nozzle) would be about 67.5 psi since you should have 73.5 in the fuel rail as you have calculated, but you still have the + 6 psi in the manifold which reduces the differential pressure.

You may need a little more pulse width to compensate.

30s at 67.5 psi will flow like 37.4 lb/hr ( compared to 38.99 lb/hr @ 73.5 psi)

So 37.4 x 8 x .9/.55 = 489.6 HP

92% duty cycle should get you there. Not a huge difference either way.

37.4 *8 * .92/.55 = 500 HP

Edit:
I've also had success tuning with Lucas 42s in two different cars now. Mine as well as an Si-Trim'd 87 auto trans vette with an otherwise stock tpi motor. No idle issues to speak of with either car. They did both require some unique tuning with respect to voltage compensation, but in the end both will idle fine.

 

What he wrote is true if the FMU is connected in the conventional way. That is, the Holley AFPR additional pressure of 6 PSI is just to offset the 6 PSI under the injector so under boost the injector still acts like a 30 #/hr unit.
Overall, your have your normal Holley AFR fuel pressure + the 4:1 FPU fuel pressure (43.5 + 24) = 67.5 PSI.

 

Up until I put the car away 2 months ago, I've had idle pulse width issues. These are ford "red top" SVO injectors I got from a forum member whom I trust. I'm still running the bid with the modified idle code.

The cars fuel requirements at idle is.. LOW. Like really low. Like, it's still rich on open loop idle with the lowest pulse width I can program without the car getting cranky. This is also with the "true pw calc" patch you added to report the actual PW. It's like 1.4 msec. My rail pressure is 55psi @ 100kpa.

On the flip side, playing around assuming the car has traction it goes lean around 5000 RPM under boost and static. (actually, the injectors go static around 4500 I think looking at the datamaster log)..

So I have a condition where I have too much fuel at idle, and not enough under boost.

You guys have had some good luck with larger injectors. I just don't want to buy another set of injectors to just be in the same position a week later. The car is sitting covered right now, but once the snow melts i'll be out tuning again..


Ok. So my math was off because I wasn't considering the pressure differential. Thanks guys

Yeah, my holley is connected to the rail. It's a commander intake + rails, and LS1 throttle body. I think you guys saw pictures.

I was planning on putting the FMU on the -6 return line and running a 4:1 plate in it.


My 355 had iron heads, and 36# injectors. It was a hair rich at idle, went static at WOT but I was able to do ALL the boost fueling (pinned a 2 bar map sensor!) with just the injector and a 1:1 regulator. The 358 in my vette wants WAY less fuel at idle. Right now I'm having problems with off idle transitions, black plugs, and I'm afraid I'm gonna wash the cyls on a shortblock that cost me a small fortune to build.

If you put the pedal to the floor the car is fine but I'm not 16.. I want it to leave a light just as smooth as my truck but run a 11 second ET..

How is your car? Your the only other guy I know with a powerdyne now. Everyone else sold out.

-- Joe

 

I run stock red top 30's in my bone stock 1986 TPI 305ci and I think the BPWs were around 1.4ms at idle. The 355 ci engine with the 42's was around 1.2ms........all from memory, not 100% sure. Both run stock GM fuel pressure regulators.

Did you try to reduce the BPW with the 30's at idle to lean it out? If so, did it start to idle erractically? Could have been a voltage and low BPW offset table problem (needs flattening / less correction).

I hear you about the larger injector plunge. In the beginning I had a very hard time with the Ford green tops and $58 code. Grumpy and others kept telling me they were junk and to throw them out. I wouldn't give up. I finally realized it was the $58 code that was the problem and starting to document the source code. I went to the AUJP and it was night and day in terms of idle. With the 42's it enters single fire mode under decel but stays in double fire at idle with the 1.2ms BPW. It sounds like your BPWs would be lower with 42's in your engine so I understand the concern.

Oh yeah, this is the very reason I started messing with the $0D code (427 ECM). It has two injector drivers that can be fired in bank fire mode. That is, fire alternate banks at idle so the injector essentially looks like it is half the size. I have some 72's waiting to go in once I get the fuel mode switch (code change) done next summer.

 

That may be the key. I'm running much higher pressure than stock, to keep from (but it still happens) going lean WOT.

Idled up and down. basically went into a surge of sorts. I've tried a few times.

I need to review my notes, but I think I disabled a lot of the idle correction stuff. Don't think I tinkered with the voltage one, but .. crap. what was the other ones. I know you and I talked about this in some length but.. My memory is failing.

-- Joe

 

It was a decision to blow the wad on a good FMU or injectors. I went the injector route because I figured the depreciation would be less if I had to sell them if I couldn't get them to work. More people want 42's than FMUs because the FMU is only good for boost and 42's are good for boost, N/A, N2O. I am fine with running FMUs, the larger injectors just seemed like a better path for me.

Most of the time people play with the spark advance vs. idle correction.

The low BPW offset is probably too aggressive with the 30's. The battery voltage and low BPW is usec (time) based and not injector sized based. So when it corrects......it is changing the fuel amount too much because of the larger injector. I always scale these tables along with the start up BPW and fine tune from there.

The idle surge sounds like it started hitting the low BPW offset table deeper and it needed to be smoothed out some.

 

I haven't driven it much since thanksgiving week due to the weather, but I'm still a fan of the powerdyne.

For fun, I bought an extra fender panel to experiment with. I'm going to try a Messerschmitt Bf-109 style inlet scoop to check the effect on inlet air/blower discharge air temps.

I'm just going to cut a 3.5" hole forward of the gills and simply run a forward facing 90 degree tube and route to the blower inlet with a 3.5" flex pipe. I don't think it will really be practical, but it should make for some fun.

I pulled it out of the garage on Sunday and let it warm up and idle for about 1/2 hour while I changed the oil in my truck. It chugged away nicely the whole time.

 

I'm probably going to relocate the battery to a compartment in the rear. I want to look at how the C3's are stock and try to duplicate that. I just hope it passes an IHRA tech inspection w/out having to put a cutoff switch in the rear.

After that, I'll run some plumbing so the air filter is where the battery is. With some good thermal wrap, I'd think it would be sucking in cooler air. Unless heat from the headers get's blown back there..

If I were to do this again, I'd buy a reverse rotation blower and use an LT1 intake part from a vortech/procharger kit so the air filter would be forward facing not rear.

-- Joe
-- Joe

 

I had a conversation with vortech today regarding FMU ratios. It seems they base what ratio you should use on what size injector you are running. I'm not sure if there is some type of.. equation involved over percentage gain vs injector size on raising pressure but, this is what vortech told me:

12:1 regulator for 19lbs injectors
10:1 regulator for 24lbs injectors
8:1 regulator for 24-30lbs injectors
6:1 regulator for 32-34lbs injectors
4:1 regulator for 38-42lbs injectors

(based on mustang applications, but he said these are the numbers they stick with)

So say I went with a 8:1 regulator, and we assume our 6psi of boost, on the actual gauge (discounting the differential) 43.5 + 6 + 48 = 97.5 psi.

Now, my logic tells 97.5 PSI is going to lock the injector, AND if you look at the walbro pump output at 97.5psi it won't support a 500hp application:



At 22gph it would support only 262hp.

To support 500hp, I need a minimum volume of 46 gallons per hour.

So looking back at the chart again, the highest the pressure can go while still maintaining a safe volume is around 80psi.

Which puts me right back to the 4:1 area. A 6:1 would raise pressure too high even.

The only thing I can think of is on these ford applications, the max pressure is not as high because the starting pressure is in the 30s. But even still, what does a ford run at 100kpa around 36psi? 36 + 6 + 48 = 90psi.
I don't even know how these guys with the 12:1 units get by. The only thing I can think of is these stock mustangs with 8-12psi of boost are not making more than 400hp or so. (37gph)

Any thoughts?

-- Joe

 

most stock modular 2v mustangs will run 8-10 psi and will make 400whp as thats the accepted limit on stock internals. Thats most kits i've seen they all cap it at 400whp. Not sure if that helps or not

Trying to sell my 42lb lucas injectors for a few weeks now and got little interest..i hope some ppl want them They idle fine on my n/a 383, i saw pulsewidths in the low 1.1 range no problem. may have been lower than that too i dont remember. I'd go larger injectors, there shouldnt be a problem in tuning those

 

What are you asking for them?

Nothing is selling right now. Everyone is broke.

-- Joe

 

was going for 225 shipped since they are flowmatched units that go for 340 new and they only have 1500 miles. shoot me an offer tho as i'm open to offers now

 

If you are set on keeping the smaller injectors and running a higher-ratio FMU, then you are going to need more fuel volume, and that means an additional fuel pump, just like what comes in most supercharger kits that include an FMU.

I don't know what to say about the injectors, other than I have run 42lb FMS injectors and gotten them to idle fine, even with $58. Maybe it all depends on engine combination, but I can't believe that you are fouling out plugs at idle with 30's and low PW's. How much timing advance do you have around idle? Anyway, I think a possible solution might be to run lower base fuel pressure and run a higher ratio FMU for more pressure under boost.

I remember reading a long time ago all of the issues you had with your 36pph injectors on your Firebird.. sounds like you just can't win, eh?

 

I don't get it either. I read about guys like you having no problem running 42# injectors. Maybe it's the combo's just being different .. But, when I ran the 42# the exhaust stunk and the 02 was pegged. If I tried commanding a low PW idle was just erratic. (open loop).

In closed loop, do you recall all the bucking problems I had at low speed due to the ECM trying to correct the rich idle? Those were the days!

Anyhow, I'm on the fence about this one..

Oh and I run around 20 degrees at idle.

-- Joe

 

Yeah, I remember all about your problems with bucking with the manual. Apparently I have an elephant's brain. And I kept your problems in the back of my mind when I was building my setup, as I have (had) a supercharged v8/T56 car with $58.. and in first gear at idle it would crawl up a driveway, across a lot, cruise down a residential street, no drama. Oh yeah, that was with 2.77 gears at the time, too. How is that possible? Maybe it was all accidental, but with basic tuning changes to match the combination, it seemed to run great. Of course, boost fueling was a different story, as it never made it above about 4000rpm and never saw full boost before I took everything apart. Therefore, I don't know where/when my particular setup would have ran out of fuel, and being pullied for about 10psig, 42lb injectors may have been marginal, though LT1 guys seem to make 500rwhp with them on basic setups so there's no reason why we shouldn't be able to as well. @5-6psig, with just a 255l in-tank, and no FMU, I had no signs of running lean (hint).

Anyway, I don't think you necessarily have too much fuel at idle.. maybe just a wrong combination of fuel and timing. "Missed the tune," as Grumpy may have said. I don't know what my pulse widths were, and the car has been taken apart for a few years (so I can build it "right" and so that I can mature a little bit, heh), so I have no way to verify. But, with 42pph injectors, I don't think I had my PW's as low as yours, yet I had no fuel smell, and no fouled plugs. I'd be curious to see the change advancing the timing a couple extra degrees at idle would make. I should pull out my tuning gear and files and see what my timing was like. Is the problem that you see a rich reading on the 02, or a bad fuel smell, or..? And, you need bigger injectors or more fuel pressure/volume from an FMU/supplemental pump to make the power your engine is capable of, IMO.

 

Looks like I ran about 25 degrees of advance at idle w/42's. Here's a video http://www.youtube.com/watch?v=0UNujapq_Ng ..As you can see, no smoke from the exhaust. (Please ignore white-trashy 1984 Camaro )

 

Heh neat!

I'm gonne try some 36# bosch III's and see how it works out.

The 36# injector at .55 BSFC should support 500hp at 96% duty cycle. On paper the engine should put out 500hp if the powerdyne can flow enough CFM at 6,000 RPM so it should have enough fuel.

I may need to upgrade the impeller though. I'm thinking the max CFM the powerdyne (stock impeller) will push at max eff impeller speed is about 800cfm but Tequilaboy has done a lot more testing/logging than I so maybe he can clear that up. I think to cross the 500hp threshold requires about 1,000 CFM.

I'm assuming the BSFC will be about .55. The motor has reverse dome pistons, small chambers and .044" quench and the powerdyne seems to be in the high 70s% in regards to efficiency.

-- Joe

 

500 HP at a BSFC of 0.55 requires 275 lb/hr of fuel.

Assuming a 12:1 AFR, 3300 lb/hr of air would be required to consume 275 lb/hr of fuel (or 55 lb/minute, or 412 gm/sec of airflow).

55 lb/minute / (0.069 lb/ft^3 @ 120F) = 797 cfm.

55 lb/minute/ (0.075 lb/ft^3 ) = 733 SCFM.

800 cfm should support about 500 hp depending upon the value used for air density which varies depending upon pressure and temperature and relative humidity. Note: The 0.069 lb/ft^3 density seems to be used by the turbo crowd and appears to make sense in a warm underhood enviroment.

Note: With the current calibration of my HPX MAF sensor and my own powerdyne I'm now seeing peak flow of about 460 gm/sec which would equate to roughly 888 cfm or 556 HP. This flow value appears to be a bit optimistic when reviewed in this manner. I need to recal and lean things out again.

 

275 / 8 = 34.375 so I'm within the range.

The relational HP might be a bit optimistic, but the CFM flow should be close right?

I'm figuring, the upgraded impeller has to be about damn close to being equal to a vortech s-trim. Vortech says an S-trim will produce 1,000 CFM at max eff impeller speed, and support 680hp. I think 680hp might be capable on the right combo with the right heads. On something like mine (250ish cfm heads, aluminum, small cam) I think about 500hp is to be expected. I could be wrong.. At least, I don't expect my fuel requirements to be over 500hp.


-- Joe

 

Well the measured airflow is really somewhat of a guess, unless I can verify the sensor and my calibration on a flow bench or indirectly with a wide band O2.

There was a guy posting recently on Camaroz28.com that claimed around 455 rwhp with a standard powerdyne, and around 485 rwhp after the impeller upgrade, IIRC. (Dynojet numbers). These are the highest powerdyne power figures that I've seen so far. I'm assuming its an LT1. It think its plausible.

http://www.camaroz28.com/forums/show...64&postcount=7

I think if you could safely spin them to 50-55k then you would see big power potential just like the vortechs. The compressor section should continue to flow until the inlet air goes supersonic (or the impeller disintegrates). The fact that they're rpm limited by the belt/bearings and weak cast impeller tends to hamper the potential for higher flow.

The impeller upgrade increases the boost vs rpm due to the forward swept vanes but may sacrifice some efficiency. Rear swept vanes tend to have the opposite effect. Increased efficiency at the cost of reduced boost.

It also increases the overall airflow potential by a reduction in the hub diameter allowing the impeller to hold more air, similar to a small increase in the inducer diameter. Stronger material and better balancing should also make it more durable for high rpm use. The only downside is the cost.