IRACE87

To make a long story short, I have been tuning my new combo for the last few months (DIY PROM) and yesterday was the day that I would try my engine above 5000 rpm.

Here is the problem in second gear once the engine reach around 5600 rpm the duty cycle of my injectors will drop from around 81% to 39% and feels like fuel is cutting out no more power nothing.

In third gear it will happen sooner around 4900 rpm my duty cycle will drop from around 72% to 34% instantly.

When this happen my fuel pressure goes from 45 psi to 40psi (but I still have fuel) and my MAP drop from 100 kpa to 70 kpa with tps still at 100%.

My question is can it be something corrupted in my bin that does this or a bad ECM because I really have no idea what is wrong.

THANKS

PAT

Grumpy

Sounds like your not entering PE.
Or your scanner maybe doing something odd when the DC hits 100%.

Double check the sensor end of things.
Be sure the TPS is reading high enough to hit the PE enable threshold.

Grim Reaper

Or maybe you haven't adjusted the upper RPM values for the PE Tables.

BTW, how are you calculating your DC?

RBob

iTrader: (1)

Interesting, taking all of this into account I would say that your intake duct work is collapsing. The key being that the fuel pressure also drops in concert with the drop in DC & MAP.

If the intake duct work is collapsing (or being suddenly restricted in some way) the manifold pressure will drop. This will cause the fuel pressure to drop (it is manifold pressure referenced) along with the MAP reporting the lower manifold pressure to the ECM. The ECM reads a lower MAP looks up the VE (now less) and lowers the pulse width.

Of course the loss in power is the end result.

A sanity check is to coordinate the MAP KPA drop to the fuel pressure drop. Lets say baro is 102 KPa and the MAP drops to 70 KPA, that is a 32 KPA change. The fuel pressure drops from 45 psi to 40 psi, a 5 psi change.

psi = kPa x 0.14503

4.6 psi = 32 KPa x 0.14503

Close enough.

RBob.

IRACE87

I do enter in PE mode because on my datamaster I go in fuel cell 15 and my BLM and integrator goes to 128 as soon as I pass 65% of my TPS were it is set in my bin.

I will have to take a second look at my upper RPM values for the PE tables when I get home. But I think it is set at 22%.
And my DC is calculated with datamaster.

I'm still using the stock camaro set up with a 90-92 intake duct. But the lower air box is cut no restriction there and I removed my air filter for my WOT test ???? But I guess it can still collapse, now I have to find a way to test this ????

Thanks

PAT

RBob

iTrader: (1)

Remove the bellows and with a hose clamp put some window screen over the TB. Go WOT to test.

RBob.

P.S. I don't think I'd ever run w/o air filters. To much stuff on the roads. One small stone. . . . What you may want to do is to take an old set of air filters and remove the paper filter while leaving the screening in place.

TRAXION

I can almost GUARANTEE you that what RBob mentioning is happening. It happens to almost everyone running an older SD bellows on a high horsepower setup. I personally know of 4 people this has happened too ... not including myself.

Our 'fix' (credited to Mike Davis) is to buy a small can of coffee. Use a can opener on the bottom of the can (as well as the top). Grease it up and shove it into the duct. It will take some work but it will go in.

You can see the bulging of the bellows (created by the coffee can) in this picture ...

http://www.celligent.com/tim/iroc/bracket/DCP_0871.JPG

Tim

IRACE87

Thanks everyone, I will try the coffee can trick as soon as the rain goes away hopefuly by tomorrow.

Something else came up (nothing to do with DIY PROM but) I have the inside of the plenum coated with oil that I guess came from the PCV. Is there any downside by removing it ??? from what I see TRAXION doesn't have it on is engine.

Thanks

PAT

TRAXION

Yes, there is a downside. PCV helps draw a vacuum on the engine to help ring seal which often means longer engine life. Everyone you ask will tell you to keep PCV. I ditched it and haven't noticed any ill effects ... .. . yet.

Tim

Grumpy

How can it draw a vacuum, ie enough of one to help with ring seal, if the crankcase is open to atmosphere?. ie you have the PCV on one side, and breather element on the other (valve cover, as typically executed).
It draws fresh air thur the crankcase to min the build up of various acidic fumes. Not having one, or one of poor design often causes the bearings having a pited look.

There is no down side to PCV, unless oil fumes are allowed to migrate thru the system. Oil has a very low octane and will cause detonation. The problem is that there is no real air/oil vapor seperator used, in oem form. Properly done a PCV system will increase engine life.

During overun it's extremely useful for purging the crankcase, and can be tuned for helping with emissions. The weight of the slug and orfice size are way to tune them as far as the mechanics of the system go.

Depending on how many miles you go before tear down, you'll see the bearings developing a much darker color, and or piting, from primarily sulfuric acid fumes.

IRACE87

I just tried the can in the bellows trick (used 1L empty hydraulic fluid oil can) and I gained 1000 rpm in third gear. The engine pull so hard now .

But now I'm having an other problem it won't rev pass 6025-6075 rpm, on my first run I reached 6025 rpm at 98.9 kpa with 92.2% DC and an O2 of 876 mvolts.

On my second run I dropped my PE% and with the same result. Reached 6075rpm at 96.7 kpa with 87.9 DC and O2 of 850 mvolts.
Both run were tested in third gear only.

After that the engine drop around 100-200 rpm and stay there until I lift the trottle. But before that the engine feels like it want to keep on going ????

My fuel pump is a Holley 255 lph so I don't think that is the problem and my O2 never drop below 850 so I don't think it is fuel related. (I don't know my fuel pressure during those run, my fuel gauge is under the hood).

It doesn't feel like valve float either, and I have an AFR rev-kit and my heads were upgraded with stiffer springs ???? And the rev limiter on my accel 300+ is set at 7000rpm ????

And everything in my programming seems fine, any idea ????

THANKS

PAT

RBob

iTrader: (1)

There are both speed and rev (MPH & RPM) limiters in the ECM. If your MPH reading is off in the ECM (as too high from the T56) the speed limiter will kick in prematurely.

Could also be the accel 300+ limiter kicking in too soon.

RBob.

IRACE87

In my constant the fuel cut off speed is set at 255 mph and the fuel cut off engine speed is set at 10031 rpm so this should not be an issue.

I guess I can bypass my 300+ to see if it is at fault.....

Thanks

PAT

P.S. The VSS signal comes from my speedo (mechanical) and my T56 was machined to accept speedo gears. (I'm around 106-108 mph at 6000 in third gear).

Grumpy

If your using an NB O2 as a guage for AFR, your playing with fire.
What are the plugs looking like?.
You maybe out of range of the K/S and just hammering the motor.
You can add enough fuel to do that.

And none of this excludes things like valve springs, or a mechanical ill.

IRACE87

I know having a WB would be wise but my budget is kind a low right now. I did my lower rpm tuning using datamaster and VE master that i know rely on my O2. But my plug had nice brownish color and my engine builder looked at them and didn't say a word so I guess it was fine.

At WOT I have a total of 32 deg and my K/S never detected any knock (how can it be out of range ???)
And I don't really know what a plug looks like when there is knock at WOT but mine have a grayish-tan color.

I have ford 30 lb/hr injectors set at 48 psi and at WOT in third gear at 6000 rpm I had a duty cycle of 87.9% on my last run. So there should be plenty of fuel there.
If I understand what you mean is that I can have knock occuring but since my mixture is so rich the knock sensor is not hearing it ????

I really don't want to hurt my engine......

Thanks

PAT

P.S. By the way 95% of the time my K/S detect knock is when I go in DFCO.

IRACE87

I tried my rev limiter on my 300+ by setting it at 4500 rpm (lowest setting) and it works great. But the sound it makes and the way the engine react is not the same way that when I reach my 6000 rpm limit my engine have right now ?????

I really don't know what is wrong.

PAT.