2G MAS reading vs 1G MAS, tuning issues..

a73_4g67 · 02-27-2006, 05:13 PM

Setup: 14B turbo, VR4 Engine, 2G MAF on a 1G, 550cc injectors, 255lph pump, AFPR set at 40psi, ECU factory programmed for 510cc injectors and 1G MAF, SAFC-no digital display.

Hi,

I just recently installed a 2G MAF on a 1G engine. Before we further tune the car, I want to have answers on some issues.

1) Does the 2G MAF interpret it’s input the same way the 1G MAF does? For example, 2G MAF reads 1500 Hz, is this equal to the 1500 Hz reading on a 1G MAF. If both MAFs reads 1500 Hz, does this mean they see the same airflow? If there’s a difference in calibration, can you give me an idea how they differ?

2) I’m using a GVR4 ECU factory programmed for 510cc and 1G MAF, but recently I’ve upgraded to 550cc injectors and a 2G MAF. Logically, where does this position my A/F ratio? Am I on the lean side or rich side? I’ve read that using a 1G ECU(set for 450cc) with a 2G MAF and 550cc injectors requires minimal tuning.

3) I recently logged a run and here’s my log story using MMCd. Car was boosting at 15psi with 95 Octane gas. The logger shows knock from 4k rpm to 6.5k rpm. It started at 27 counts at 4k rpm, then followed by 43 counts of knock on every rpm increment with an o2 voltage of .78v to .82v at WOT. Timing Advance was 17 degrees from 5k rpm to 6.5k rpm. We tried to richen rpm points where knock appears, but couldn’t shake off knock and the o2 voltage doesn’t seem to change. Biggest SAFC increment value was +5. It showed MAFs Hz increase and IDC also increases. By seeing this, I know the SAFC is working. Maybe we got a faulty knock sensor or o2 sensor. In case every sensor is working, can we further tune for mimimal knock using SAFC on my current setup? Should it be better if I would rechip my ECU to correct the MAF and injectors

any inputs?

huafist · 02-27-2006, 06:48 PM

I would re-chip the ECU if it were me. The 2G MAF flows ~33% more air than its 1G counterpart, so your AFR is leaned out without proper compensation. A stock 1G ECU (450's) with a set of 550's and a 2G MAF is fairly close to normal - You'll still be around 11% lean with no compensation. With a set of 510's, you'll be around 20% leaner than stock.

Someone please correct me if my numbers are wrong, but I think they're pretty close to accurate.

a73_4g67 · 02-27-2006, 07:58 PM

Quote:

Originally Posted by huafist

I would re-chip the ECU if it were me. The 2G MAF flows ~33% more air than its 1G counterpart, so your AFR is leaned out without proper compensation. A stock 1G ECU (450's) with a set of 550's and a 2G MAF is fairly close to normal - You'll still be around 11% lean with no compensation. With a set of 510's, you'll be around 20% leaner than stock.

Someone please correct me if my numbers are wrong, but I think they're pretty close to accurate.

thanks for the info. That explains the knock story. I have a SAFC(no digital display,only knobs), now by adding +20 on the SAFC, will this compensate for the lean mixture? Will this work?
1K 0 2K +13 2.5K +13 3K +15 4K +20 4.5K +20 6.5K +25? I hope I dont hit fuel cut by increasing IDC. I'll try to rechip it as soon as I can find an EProm writer. I'll just edit the bin file for the maf and injector compensation.

a73_4g67 · 02-27-2006, 08:35 PM

Quote:

Originally Posted by huafist

I would re-chip the ECU if it were me. The 2G MAF flows ~33% more air than its 1G counterpart, so your AFR is leaned out without proper compensation. A stock 1G ECU (450's) with a set of 550's and a 2G MAF is fairly close to normal - You'll still be around 11% lean with no compensation. With a set of 510's, you'll be around 20% leaner than stock.

Someone please correct me if my numbers are wrong, but I think they're pretty close to accurate.

I emailed Nate from DSMChips, they can't rechip the JDM ECU. No choice but to tune this ECU using SAFC. Any recommended settings?

GVR4592 · 02-28-2006, 01:43 AM

If you are using a stock JDM VR4 RS ecu, then it is not the same as a 1g US ecu. VR4's don't have lower honeycombs, so it already flows more than a 1g sensor, the correction factor wouldn't be as much as a US 1g. You can burn chips for the JDM ecu, it's a pain in the ass though. You can also convert a JDM ecu to US specs which is also a huge pain in the ass.

What kind of vehicle do you have?