I'm wondering how quickly fuel requirements go up as mods are added. I'm chasing problems with my tune and it seems happy now, but I have 65# injectors and a 175 BPC (vs. 55# and 135 from the factory). Combined, that's about a 35% increase. Is this within reason for a motor with an open intake and headers, or should I still be trying to run down mechanical problems?

 

it shouldent drop but maybe a gallon or two, mine stayed the same

 

I meant in the fueling tables, how much more would it want at the same RPM/MAP cell. I know people with really hot motors go to all kinds of trouble to get bigger injectors and more fuel pressure.

 

65 lbs injectors at 13 lbs FP will support 236 HP BPC 133

" .......................... 18 .............. ........ 289 .......... 109

Your fueling table(VE) values are determined by a datalog of BLM in CL.

A log of DC% at load will determine if you need increased fuel pressure or larger injectors. You should be 85% or less.

A WB come in handy for WOT data log.

 

Thanks. I just want to know what is realistic, to know if I should still be searching for fuel problems or something else. I'm looking for some sort of example case, like if someone stuck a factory TBI on top of a race motor, would the initial BLMs shoot up to 200 on the first test drive? Not necessarily at high RPM, 150 mph, but just in the normal VE table range.

 

Possibly. As long as BLM <160 in CL there would be adequate fuel. In AE or PE all bets are off as fuel could be inadequate.

What cam and what heads do you have?

 

Can you explain why this is the case?

I'm afraid I don't know all the specs on my motor. I had it built about 10 years ago and just had them go for performance but with good low end and idle vacuum. So it's far from wild, but hotter than factory.

 

CL is the output reads from the 02 sensor affecting the INT term and the final BLM resulting. Bottom line when >112 or <160 BLM the engine runs at stoich or 14.3/1 for E10.

BLM is going to change based on atmosphere/barometer, environmental temps, enginewear/defect. It is doing its job.

If the VE table is looking good(124-132) then the AE and PE will be OK assuming there is enough fueling capacity(ie DC% or A/F<13.0/1).

W/O a WB tune I ran my car on dyno. BLM was decent as stated above. PE ended up 12.0/1 A/F. I had enough fuel to support 225 HP wheels

 

Isn't the system still stoich if it's running happily in closed loop with a BLM of 170?

 

Maybe. I thought 160 was max but your .bin may alow 170 max. It is still not providing proper correction as it is at the end of its rope. I presume you know how to correct that?

 

I did a combination of things. Turned up VE some, used 65# injectors, turned up the fuel pressure, and increased BPC. It seems happy (BLM around 128 now), but it seems like I did a lot for a fairly mild buildup. Thus my question.

 

Are you datalogging for BLM and changing the cells that need changing?

 

Of course, but VE was already at 100% in the factory bin, so I upped BPC to get some headroom.