HOw to get 42lb inj below 1.9 PW (pulse width)

[lbz34]

So I am tuning a 99 TA with STS turbo and 42 lb injectors (green tops). I can not seem to get the idle AF to drop below 12-1 af. This car is 3 bar SD. My 96 lb 02 camaro with 02 OS will go to .9 with the min pulse, adder/default/etc... and a af as lean as i want it. Injector adders/min pulse etc... to 0 but this car is not responding to zeroing out the min pulse and adder tables. I lower the VE table with no response in AF at all. Just stays at 11's a/f at idle but the part throttle and wot responds normal. Am I missing a table somewhere on the 99 3 bar SD OS??????????

Have to finish this customer tomorrow so any ideas are well appreciated.

[WS6FirebirdTA00]

They will start to misfire around 1.7-1.8 ms and go way lean, 1.8-1.9 is about the best you can do. You can decrease the offset and the min pulse width..

[[email protected]]

is this ecu limitation? can make other factory hacked sytems do it. i know, not best for injectors 2x stock, but....

[WS6FirebirdTA00]

no, other injectors car go lower without a problem, it is something with these injectors. I read a test done somewhere, can't remember where, and they discussed this.

[jewce]

A boost referenced FPR will fix the issue, but then you would have to redo your VE tables.

[maxgee]

At idle, what are the injector p/w supposed to be?

[WS6FirebirdTA00]

depends on what the injector is...

[BADSZ28]

I can't get my green tops to go below 2.5ms at idle.

[WS6FirebirdTA00]

They will go to 1.8, just have to change the correct tables.

[BADSZ28]

What are the correct tables? VE is not doing it. No idea what table to change. My min pulse tables are at 1.277 so I am lost.

[WS6FirebirdTA00]

and I quote...

They will start to misfire around 1.7-1.8 ms and go way lean, 1.8-1.9 is about the best you can do. You can decrease the offset and the min pulse width..

You need to decrease these. The min pulse width at 1.277 means absolutely nothing. Read the rest of your tables, you have adders to the min pulse width like the short pulse adders and the offset.

[Bluecat]

I've never seen the code broke down to know if this is exacly how it works, but to the best of my knowledge and lots of experimentation this is how I belive the min pulse tables work....

The min/default pulse tables are relative to the delivered fuel. In other words it does not include any offset added to the opening time. So lets say for a given condition, your offset table looks up 0.5 ms and the spa table gives you 0.1ms. So with a stock min value of 1.2 you get an effective 1.8 ms minimum pw.

0.5ms + 0.1ms + 1.2ms = 1.8ms

With you average 42's you need the floor dropped to around 1.4ms to keep from going rich on decel so I'd run a min and default tables at like 0.8 with 42's





Don't forget the Transient / Min Fuel Miligrams value (if your calibration has it or its not zeroed). I personal think HPT has that labled wrong, because

A. If the computer viewed it as fuel quanity, you wouldn't have to change it after an injector size change.

B. it binarly is the exact same value in the calibration as the min injector number, so it sure looks like the computer treats it as a time value.

C. Other brand software strait up calls it a min injector pw value and makes the enginering unit ms

Reguardless, functionality wise if you change you min and default pw tables to x% less than the stock value you need to decrease the Transient / min fuel minigrams value by the same % or the tables get overided and nothing happens. Ex, Lets say you have a stock min/default tables of 1.277 and stock Min Fuel Miligrams value of 0.041. If you changed from 1.277 to 0.630 you would need to decrease the Min Fuel Miligrams to 0.020

[WS6FirebirdTA00]

yeah good point, the transient also may need to be lowered depending on the injector.

[BADSZ28]

Hmmm...I finally got the AFR at idle where I want it with the VE adjustments, but the pulse width is the same. I will look at the tables Bluecat mentioned and see what happens. I want to be sure my decel PW is where it needs to be.

[Bluecat]

Do a histogram of injector pw in VE table format (RPM VS MAP). If the lower map cells all read the same number, then your hitting the floor. ex, all your 25,30,and 35 kpa cells read 1.9ms.

[BADSZ28]

I may try that, but I think I hit the floor. Although 2.6ms seams high for a cam only 346 at idle.

I have another question related to this. When I first start the car, it idles lean (18-19 AFR), but the PW is at 3.0ms. I don't understand. When it warms up it settles in to the 14.6-.7 range and the PW comes down to 2.6ms again. I thought afterstart enrichment was suposed to richen the mixture, not lean it out. Any ideas there?

[MNR-0]

Sure its not just your wideband coming up to temp?

[BADSZ28]

Yes I am sure because I added in some after start enrichment and it went away.

[gametech]

Yes I am sure because I added in some after start enrichment and it went away.

Do you still ahve the AIR pump functional?

[BADSZ28]

No. It is removed and turned off.