Maxed MAF question

[Pulse_GTO]

I was tuning a friend's 2004 GTO that is stock except for a GT-2 cam (?), longtubes, catback, and a small APS twin turbo kit and Siemens 60lb injectors.
I used the injector spreadsheet to scale the injectors, and when hooked up to the scanner the MAF would max out around 4500rpm and then have a jagged up and down line. I went ahead and tried my best to tune it in SD, but with a stock MAP sensor there is only so much I could do, so I had to rape the PE table to make it safe. Car seems to run fine, but this is just a band-aid so he won't blow it up. Also the afr will range from low 10's to below at WOT.

I did some searching, and it says that I can multiply the injector table by 80% to help with this issue, but here is where I'm getting confused. I would imagine that the MAF table should be multiplied by 80% as well as the engine size to keep everything in check. Also I should not have to make any changes to the VE table since I got that pretty close when he is not in boost.
Should I procede with normal PE and spark tuning after that, or am I forgetting to change anything else?

[WS6FirebirdTA00]

That is if you are hitting the g/sec limit. If that what you are maxing out or are you maxing out the MAF (MAF Hz)? Get that fueling closer to 11.8 and your issues may go away. Running in the 10's will falsely max out the g/sec if that is the case. That is WAY too rich.

[Pulse_GTO]

Yes, it was hitting the 511 g/sec limit, then going crazy on the scanner, still had some HZ left. I know that if I hit the Hz limit, I need a bigger MAF.
So what is the best approach now?

[WS6FirebirdTA00]

Try to lean out the commanded fueling if you are 10.0 or richer.

[Pulse_GTO]

It was maxing out the MAF before I started changing the PE table, then it would go extremely lean. I just put the car in SD and tried to keep it rich so my friend would not blow it up. Problem was that I could not get it around 11:1, a small change would cause it to go up or dow 1.5 points.
My question is what do I have to change to trick the 512 g/s limit?

[WS6FirebirdTA00]

OK, so the car matches what you are commanding then? If that is the case, then it sounds like you will have to go SD or alter the MAF and IFR to play with the numbers and get it to work.

[Pulse_GTO]

OK, so the car matches what you are commanding then? If that is the case, then it sounds like you will have to go SD or alter the MAF and IFR to play with the numbers and get it to work.

My friend would like to stay with the MAF, so from what I gathered by searching, I can start by multiplying both the MAF and IFR tables by 80% and see if it still hits the limit, if it does not procede with tuning the MAF, then work on spark, keeping in mind that the g/cyl values in the spark table will be inb a lower range.
Am I leaving anything out?

[5_Liter_Eater]

You've got it.

[Pulse_GTO]

I've scaled the tables 75%, and now I'm not running out of g/sec, but the frequency is hitting 11260 Hz at 5154 rpm. Does this mean that we need to go to a bigger MAF? You can see this happening at frame 4454 of the log.

[SEGA]

I've scaled the tables 75%, and now I'm not running out of g/sec, but the frequency is hitting 11260 Hz at 5154 rpm. Does this mean that we need to go to a bigger MAF? You can see this happening at frame 4454 of the log.

Why did you scale it 75%?


www.admperformance.com

has 100mm mafs for many vehicles that do not max out like your current one.

[Pulse_GTO]

We put in a 100mm MAF with the LS3 sensor, and had to do some tweaking. I had to raise the MAF table by almost 400% to get the car to run, but that would have maxed it out early on the frequency, so I then halved it, and multipied the IFR table by 75%, and that gave me room up to for the frequency and g/sec, and it allowed the car to actually run somewhat decent. It's hitting over 11,000 HZ even with this MAF, so I think that if he goes bigger he will need to go SD with a custom OS.

[RWTD]

I would imagine that your MAF transfer really isn't exactly true due to the fact that you're not using the proper values for the 60s.

Where is the MAF located? Also, is the 100mm housing sandwiched between two 3" pipes? How much power does this beast make? Thanks!

[SSpdDmon]

The problem with running false MAF numbers is you end up in a different spot on the timing map and the internal load calculations are thrown off. That is why I don't like the internet's 'correct' way to VE and MAF tune. Let's say for example you had to halve your MAF table to get the car to run right. Now, instead of it reading ~.80 grams/cyl at WOT - it'll read ~.40 grams/cyl. Look at what that does to your timing. Assuming you RE-MAP the entire table, you've just lost half of your precision. Granted, that's an extreme example. But, that's one of the things that happen when you fudge a MAF curve. Tread carefully, grasshopper.