adjusting IFR

[starks]

I keep hearing about people adjusting the IFR to compensate for E85 fuel.

right now i have normal IFR tables (for 63lb injectors)

63.16930 63.89877 64.79023 66.07419 66.34388 66.47955 66.58167 66.66701 66.75257 66.99330 67.20103

and i compensated for e85 by MAF tunes. problem i have, is the 512g max is in the 11,200 or so table, and my car is getting close to that number.

should i be adding fuel via IFR tables instead?

im also under the understanding that people are adding approx 30% to the IFR tables. wouldn't that make the pcm think the injectors are bigger then they really are, causing the car to run leaner? i would think you would want to reduce those numbers, but i may be thinking about it wrong

let me know what you guys think, car is a 98 regal gs (3800)

[starks]

anyone?

[5_Liter_Eater]

I'm not sure what to tell you about compensating for E85, but if you are approaching the 512 g/sec limit then just reduce your MAF anf IFR table by the same percentage. If you are approaching the frequency limit of the table though, you need a bigger MAF.

[usd2sing]

the v6's are limited to 11500hz internally, no way around that while still using a maf referenced tune.
EDIT: some cars have issues with exceeding that 11500hz limit and the puter freaks out, shuts off fuel/inj, it sucks, instant lean condition.
airflow limits are 67.7lb min, some (mainly turbo guys) clip this at 4000rpm....yeah, quite excited when this happens...LOL

OP, correct, reducing the number in the inj table "tricks" the system and adds more fuel. increasing the number does the opposite.

[5_Liter_Eater]

The Hz limit can be mitigated with a bigger MAF. My old 85mm MAF hit ~470 g/sec at ~12000 Hz which is my table's limit. My 100mm MAF reads the same flow at ~10500 Hz.

[usd2sing]

understood, many have used the lt1 or the vette/truck parts. but we have an internal "scale" (physical limit for the lack of a better term) limit of 11500 which makes it tough to dial in the upper end especially when your clipping over 13000hz.

[Eddie-98GTP]

For what it's worth...

The SLP MAF sensor uses a resistor to lower the freq. output. Put between the contacts of the hotwire, the MAF will read less current across the wire at the same airflow. There was a guy on the DHP board that tested this, pretty interesting. I don't remember the resistaince of the resistor, but it isn't hard to install so changing them out would not be too difficult until you get the right one.

Hope this helps.

[starks]

thanks for the help guys. i just multiplied my IFR table by .8 and my maf table by .8. now im no longer maxing out the maf 512g/sec at 11,200.



since i barely reach 11,000hz, i dont think i need a bigger MAF, yet

[5_Liter_Eater]

Thats good info! Where were you a few weeks ago? You could have saved me ~$200.

For what it's worth...

The SLP MAF sensor uses a resistor to lower the freq. output. Put between the contacts of the hotwire, the MAF will read less current across the wire at the same airflow. There was a guy on the DHP board that tested this, pretty interesting. I don't remember the resistaince of the resistor, but it isn't hard to install so changing them out would not be too difficult until you get the right one.

Hope this helps.