Performer RPM w/throttle body FI

[Cyclone03]

I have FAST ez 2.0 FI on my 433ci FE. I have been using a Performer RPM with a 1/2” open spacer .
I found the open spacer helps mixture distribution. Reading spark plugs shows a noticeable rich mixture on the corner plugs without the spacer. With the spacer the mixture is more even,center plugs richened up but ends still read richer. I don’t have the clearance to add more spacer so I’m looking the other way,cutting the plenum divider . I’ve read the Dyno results on cutting the divider with a carb I don’t know if the results will be the same with TBI. If your not failure with the FAST TBI it has 8 injectors with pairs aimed under each throttle blade from the front or back. 4 shoot into each side of the plenum more or less toward the center of each plenum half.
I haven’t found anything on line about modifying a 2 plane to perform better with TBI.,everything I’ve seen says use a single plane.
Anybody have experience with this?
Time to look for another Streetmaster?

[cammerfe]

Most of my experience has been with Holley TBI and two plane manifolds. I have used a Sidewinder, a PI, and a pair of TBs on a MediumRiser and a TP. I also used one on an SP2P on a 460. On the SP2P I cut the center divider down a bit and also cut back the runner dividers as well, but everything I did on any engine seemed to run just fine---no hickups to point to a manifold difficulty. Good Luck!

KS

[My427stang]

How are you reading the plugs, general use, wide open and shut down? Does the system have a log capability?

[Cyclone03]

No logging. General use but being in Tx. I have a toll road with an 85 limit,so 20 mins at 95,right at 3000 rpm,then 75-80 home with 3 miles at 45. The 1/2 open leaned the end runners noticeably ,AFR remains the same. The O2 sensor is in the left bank so the mixture is an average of 4. For what it’s worth the left bank is lean overall that is why the sensor is there.
At low cruise loads the mixture shows 14.0/14.2
At the above speeds 13.8/14.0 ,map shows a noticeable load at 90.

I know it’s all about speed and power and to hell with what plugs look like,but with mixture that averages 1/2 the engine 2 lean and 2 rich can make a difference ,just trying to balance what I have .

[My427stang]

What fuel pressure does your system run and how big are the injectors?

I never thought the RPM was great for distribution, carb or EFI, but wondering if you are fighting injector spray pattern problems

[cammerfe]

I have no idea regarding other available systems, but Holley comes set for 25 PSI and uses 4 90 pound injectors when configured for a V8. When using dual TBs, we had to go down to 70 pound injectors in order to have the adjustments within the operation range. For what it's worth, the pair of TBs gave a massive boost to midrange torque when tested against a pair of 652s, and 750s.

KS

[Cyclone03]

8 78lb injectors at 42 psi.
Injectors fire in pairs,4 drivers. They fire opposite corners according to the wire diagram.
I’ve talked with CPG in the past but not this issue. I asked about how would I know I lost an injector  they said pay attention to duty cycle so I do,no real change.

My427stang you might have touched on my problem stating you haven’t found the RPM distribution to be that good,so I may be stuck. I just was wondering if by removing the requirement for carb signal opening the split plenum might help distrubution.
If I had the room under the hood I would add spacers 1 inch at a time and test,but I’m not a fan of running without an air filter.

[My427stang]

So, it's likely only marginal utility to read plugs like that, but a modern EFI should look like you are running lean though, so it likely is rich somewhere, but it also could be dousing at low RPM confusing your results.

So the question comes next is, "would another intake be better?"  I am not sure it would, you are adding a lot of fuel very high in the path, so in terms of comparing to a carb, I agree that a carb likes more signal, but that is to get circuits moving when they are supposed to, in your case, I think you are potentially experiencing fuel falling out of suspension

Let me give you a reference, that may not apply, my 489 with port injection runs 8 45 lb injectors with 50 psi. Now if you are saying at any given time yours are only running on 4 injectors, that makes sense, but regardless, that big of an injector may be losing spray pattern to operate at less than full demand

Are you high enough on duty cycle that you may be able to increase fuel pressure for better atomization/spray pattern?  Might make a cleaner but shorter shot of fuel.  Remember the high end ECMs can adjust slope and duration, meaning how the injectors open and close and how long they stay open, however, some cheaper versions only adjust duration.  Very limited models adjust pressure and that is usually only for boosted and done by pressure to the regulator.  I see that the FAST 2.0 system will let you go up to 60 psi in the handheld, may want to try bumping it up to get a little cleaner pattern. 

I also see that the FAST system uses a vacuum reference.  I am on the fence with those, as a boost reference, they are awesome because they allow more fuel when there is pressure in the intake port, however on a nat aspirated motor, it will richen at high vacuum.  I have disconnected that on some models (crappy Professional Products versions) and just run a fixed pressure, another tuning tool.

Also, what kind of idle vacuum are you running and what kind of timing curve.  I know you are not asking to make it run better per se, but trying to get the feel for the engine

Another question, what are you running for a return, is it full return or modulating pump power and no return?

My gut tells me that system is made for big HP numbers and you may be asking those big injectors to operate in a wider range than they should, but that doesn't mean you can't get closer, just takes some thinking

[Cyclone03]

Thanks Ross.
Timing is ECM controlled and has a MAP adjustable slope. But the MAP function is vacuum advance only not true load based timing.
This is EZ 2.0, the timing is set at base,total and rate.
I have 18deg base,34 total all in at 3500. The reason for slow curve is the vacuum,load based timing. After a lot of trial and error I have found the cruise timing sweet spot and still have good timing under load. Just a balancing act to get good usable cruise low,mid load timing and still have a safe high load wot timing.

As for the injector size,again stock ez2.0.
This set up has been running for about 6 years now,with the current tune over a year now after the cam change ( I’m the guy who broke the camshaft last year).

The duty cycle ,it shows on the display but I don’t remember what it is,I haven’t used the screen every day for several months now. At low cruise it runs 18-22% I remember that because of repetition ,it was alway on screen. Higher speeds low 30’s. WOT I have no idea, too busy  to look. I’ve never had a co-driver to read the display. Time to point my Go Pro at it...hum.

Your insight on Performer RPM distribution is helpful. I don’t know if adding spacers and running without a filter would relate to cutting 1/2” out of the divider (or more).

I wonder if Jay wants to rerun TGFEIComparo with TBI instead of carbs? It’s not like he’s too busy doing anything else.lol

Lance

Edits are fun you added some stuff while I was responding .

[My427stang]

Go back and check my edits, sorry made some changes in the meantime

I think you want it to be the intake, but to me, it's a "too big of an injector" problem, assuming it is really a problem and not just something you see.

Those duty cycles seem low to me, which would indicate an injector that is too big

[My427stang]

For reference, I generally calculate for an 85% duty cycle at WOT.  if you can get a passenger to hold on for a real ride LOL, you might me able to get a good idea of where you are.

Also FYI - calculating an 85% injector duty cycle on a 500 hp motor, using 8 injectors at 42 psi, typically I would size at 37-42 lb injectors for port injection.  Your injectors really seem to be for a big horse application, makes sense for that kit, but also means the injector has to trade off at lower duty cycles.  In other words, you have a hose of fuel flow you are trying to use as a mister

May not directly apply to the FAST TB, but if you wanted to chase it, I would maybe call FAST and talk to them about injector sizing and duty cycle in your specific application and RPM.load environment.  Could be a drop in injector size would get more control

[Cyclone03]

Call FAST,lol it’s almost impossible to get some one on the phone who speaks mechanical not electronics . Case in point,I had the seal around the MAP sensor fail,spent half a day on the phone setting resetting testing in the end I took a step back and noticed when I blipped the throttle the vacuum gauge moved as it should but the MAP never moved.Looked “normal” but responded incredibly slow. Same with adjusting throttle blades.....

Yes a set of 42lb injectors would be a better match.....

 I think I need to load my cooler and plug socket and head for the toll road , I have 60miles ($9) of 80-90mph test road for a cruise mixture test. Nice big travel center right off the exit ramp,can coast right in.

I have thought about just un plugging four injectors.....

Lance

[My427stang]

Call FAST,lol it’s almost impossible to get some one on the phone who speaks mechanical not electronics . Case in point,I had the seal around the MAP sensor fail,spent half a day on the phone setting resetting testing in the end I took a step back and noticed when I blipped the throttle the vacuum gauge moved as it should but the MAP never moved.Looked “normal” but responded incredibly slow. Same with adjusting throttle blades.....

Yes a set of 42lb injectors would be a better match.....

 I think I need to load my cooler and plug socket and head for the toll road , I have 60miles ($9) of 80-90mph test road for a cruise mixture test. Nice big travel center right off the exit ramp,can coast right in.

I have thought about just un plugging four injectors.....

Lance

That would be interesting, but not sure the ECM would like it.  Another option would be to see what design they are, might be able to find some Ebay takeoffs cheap, there are only a few options.

[Cyclone03]

They are standard GM design ,common EV style.