General Injector parameters don't match.

[mikyrc]

Hi guys I have a problem and I can't figureout what's wrong.

I got new 750cc FIC injectors and an aeromotive FPR.
I'm using a 2G mas and custom eprom code (I have an ostrich and use tunerpro).

The problem is that I have to lower the global injector setting to 720cc to get correct AFR numbers, even do I have the base pressure set at 43psi instead of stock 38. In theory with a base pressure of 43psi I should set the value to 797cc on tunerpro.

I know those injectors should flow 740cc and have a deadtime of +315us aprox. I had to lower the deadtime to +180us to get a correct fuel low trim and the global fuel value set to 720cc to get correct AFRS at WOT and high trim..

I've checked for boost leaks and found none, tested other 2 different 2G mas and there was some minor differences but nothing that could cause that much variation.

I use a used Mazda RX7 fuel pump (denso) that should flow about 225lph. It's not only lack of fuel under boost but all the rpm and boost range above idle.

I have a flow test sheet for a set like mine and the real flow is around 740cc instead of 750cc.

The fuel pressure gauge is acurate i tested it against two or three expensive gauges and it matches.


BTW, those are the values I used for the 2G mas mod (the ones everybody use):
MAF adder = 64
MAF scalar = 31235
MAF compensation (from 0 to 1600Hz):
133.00
133.00
168.00
182.00
190.00
195.00
200.00
204.00
208.00
212.00
215.00
218.00
220.00
227.00
230.00
232.00
235.00
234.00
234.00
232.00
231.00

I use a totally stock mas, no honeycombs taken out and calibration screw not moved from it's stock position.

Right now the fuel trims are around 100% (98-103%) and the afr at WOT is pretty close to the AFR table. Although the mid fuel trim is always at 100%.
I test it setting the AFR to 11 all across the table (above 1g/rev) and my PLX M-300 wideband show 11.2-11.4 aprox on all range.

In closed loop the wideband reads from 14.6-15.2. So I don't think it's a problem with the wideband, as if it were reading wrong the high fuel trim would be at very low % right now (meaning very rich condition) because of the injector global value I use, and instead it's moving around 102-107%

Could a fuel pump cause that problem?
Or a leak on the fuel pump to bracket seal or a clogged fuel filter (which is 6000 miles old)??
Maybe the 3 MAFs I tested are reading wrong?
Could undegreed 264/272 cams make this happen? (wouldn't it be worse at iddle?)

Any help will be apreciated.

 

[mschlanglv]

I have a similar issue going on. My FIC 750s are needing much less deadtime than the recommended +315. I figure that if the car runs well, and fuel trims are pretty close (as it seems yours are) I'm not going to worry about it too much. There are many variables that cause one car to use different settings than the rest.

 

[mikyrc]

And what value did You set on the injector global setting?

I guess I'll leave it like this as the car runs perfect.

 

[donniekak]

Are you sure they are 750's? I ran the same type of 750 on e-85. At 47 psi base pressure my global was at 625, and deadtimes around 300. I also use a 2g mas. Where did you get the 2g mas values? I forget what mine are exactly, as i did mine a long time ago in a hex editor, and dont have my tuning laptop with me now to check the tuner pro values.

 

[mikyrc]

Yes they are 750's, I wrote FIC customer service telling them the numbers stamped on my injectors and they told me they were 750cc and sent me a flow chart from a set like mine (real flow around 740cc and deadtime +315)

I got the 2G mas code from the dsm-ecu group on yahoo and Jeff from dsmchips told me it's the right one.

So is there anything else that can affect injector settings asside from Mas sensor and fuel pressure?

I don't think it could be our gas being different in Spain than USA or aftermarket cams.

 

[mschlanglv]

I believe I am around 680cc or so, but I'd have to check my tuning notes at home. I am running a stock-pressure 1g fuel system.