Looking For Pegged MAF on Boosted Application

[konabluekiller]

Looking at some logs from when my motor popped a couple months ago. I had always just looked at knock, timing advance, measured afr and AIT. My car was originally tuned on the 4.63 pulley and d1sc and made 12 psi up top. Me being stubborn pullied down to 4.5 without a tune and had the log looked at and it was perfectly fine. Drove it that way a few months.... then down to a 4.38 pulley with torco added for octane. Again, just looking at the logs myself things looked fine.

Then I swapped to an f1a and 5 inch pulley for temporary with plans of more modifications to support more boost. It was making roughly the same boost curve as the d1sc on the 4.38 pulley. Did some 3rd gear pulls, no knock, 15-16-17* of timing relative to rpm and almost dead on .78 lamda across the board. Did a 2, 3, 4th gear pull after that with the laptop closed and boom, number 8 melted and the rest of that bank was close behind it.

Motor is rebuilt, and changing setups a tad bit. Question I have now is, for learning purposes... When reading the 3rd gear logs from that night, the maf frequency is still climbing but the lb/min seems to level off at 5500 to 7500.... is that the MAF being pegged even though the frequency is still rising? That should make it lean if I'm understanding correctly.... so why would the afr still be .78ish just like it's commanded to be?

Btw car is a 13 boss 302, stock motor, f1a on 15/16 psi (at time of incident), id1000s, kb bap, and kooks headers full exhaust...

 

[Tron84]

I'd like to know how that is determined as well.
My tuner told me I was almost maxed out when I was at 14psi

 

[Voltwings]

Typically when you peg a MAF, you will know. In my previous experience it literally stops the car dead, almost like a throttle close or fuel cut would. I am used to MAFs measured in Volts, and in that case there is a 1:1 relationship, meaning each voltage has a specific G/s value it commands. Obviously the computer interpolates between break points, and the fuel trims have the ability to alter this, but my point is that if frequency is raising then G/s should be raising as well. Can you post the log?

 

[92fiveohfox]

Maf/lb stops at 86.69, look at maf frequency to see if it's pegged

 

[konabluekiller]

I will when I get home

 

[Stevem17500]

The reason it popped is a bap....on 15psi stock fuel system no bueno just my 2cents

 

[konabluekiller]

I will post the datalog when I get home. But yeah I was thinking that it just ran out of fuel on the long 4th gear pull. Because I'd done plenty 1st to 3rd gear pulls without issue.

 

[92fiveohfox]

Slightly OT but are you building it at TSS(I see you are in orange), what did they recommend for you as far as the motor build goes?

 

[DSG2NV03]

Seems like you did run out of fuel. :-/

 

[konabluekiller]

I built my own motor. It was tuned originally by triangle and they did an awesome job. I just pushed I way too far on the 12psi tune like a moron.... lesson learned and the new motor is running great. Got some break in miles on it and retuning soon with TSS

 

[92fiveohfox]

I built my own motor. It was tuned originally by triangle and they did an awesome job. I just pushed I way too far on the 12psi tune like a moron.... lesson learned and the new motor is running great. Got some break in miles on it and retuning soon with TSS

That's great. Let us know what it puts down.

 

[Stevem17500]

What's the specs on new motor

 

[konabluekiller]

Just went back with everything stock boss 302 spec. Got the block for cheap brand new and a buddy had a full rotating assembly that was basically new. Then did a new bearings and soft parts. Would have been way more to do sleeves and a new forged assembly. Just bought a house and I want to get a lift and new tools for the shop so I didn't want to blow a bunch of money on the car. This rotating assembly has already made 936 to the tire on race gas in the other motor it was pulled from. The boss stuff will hold up as long as the block will so there's no point in upgrading it without doing the block too.