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View Full Version : 850cc + Q45 MAFS + SAFC II, Good You?


SequenceGarage
05-21-2005, 01:54 PM
Oh boy oh boy oh boy does the car run silly. It sounds like a mother fucking bridgeported 13b or some shit.

I had to raise the idle screw just to keep the car idling.

I guess I should answer the first question - why the fuck are you being an idiot - cause my ems isn't here yet but it should be here tuesday. For now I am just trying to use my safc to get the car to run. Which it does. Now to my question:

Q45 has 370cc injectors stock, 370 * 8 / 4 = 740. So if i put in 740cc injectors + Q45 mafs theoretically the car should run pretty much the same, except the timing would be more advanced all across the board. Now I put in the Q45 mafs, and the 850cc SARD injectors so 740/850 = .870 so that means on the s-afcII I should pull 13% across the board to get the car to run its best. Right. Awesome.

Now I did NOT set the Q45 mafs on the safc because then I wouldn't be able to remove enough fuel (it would only support 50% more which obviously isn't enough).

Ok sooo all that backround info has been taken care of heres my question. The car runs better at idle with +50% rather than -13%. I'm guessing this is because the mafs is reading such a low figure (0.9% on the safc - old mafs was about 2.5~) it isn't very accurate. Also the 850s are at such a low duty cycle that they are probobly not even atomizing the fuel, and more is required to get the same afr due to these inefficiencies. Correct me if im wrong thats just my guess.

But heres what I dont get, even at 2000, 2500, 3000rpm in neutral no load, if i set the afm to -13% and then raise it to about +8% it revs itself up (in otherwords the mix is getting stronger and creating more power - i was lean before). Where did I go wrong? Does the mafs not have a linear curve for airflow : voltage? And if so would my s-afc correction map have to be all fucked up just to make the car run well?

Lastly, before the car ran very very smooth, hold it at 2000 and its just a steady WAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA now it burbles and pops like a dirty bitch. Is that from timing? Or injector lag time?

Thanks guys. I was trying to get the car running for a montreal drift event, but it got cancelled, which (i never thought i'd say this) is actually a bit of a relif, the car is clearly not ready for these 850s yet, hopefully the ems will do the task on tuesday.

Sorry for the long post there was a lot of info to throw in there. Thanks boys! Oh its an S14 SR btw

DTS
05-21-2005, 07:38 PM
im pretty sure the ecu is used to numbers at certian points such as 2% at cold start and 1.1% on idle and your q45 maf (WHICH SUCKS YOU RICER) is reading a lower afl than the stock maf confusing the ecu since its only a piggy back but im just a hippo lover so i am only gussing

speeddreamz
05-22-2005, 04:18 AM
if you don't select a Q45 maf on the in and out settings, the car will run like shit reguardless of how much fuel is gettin. if i had 100000000cc injectors, but didn't set the "in" setting on the S-afc with a differet maf i'd run shitty. Set that first, and work from there. But I hope you're running a turbo setup soon. And another thing, the hp to come from these injectors seems pretty lage, meaning that to tune this kinda high HP setup, you'd need more than a s-AFC you're gonna need timing adjustment and other stuff too. Get a REAL EMS if you plan to use all of those 720'cc's with a proper sized turbo.