IROCZ28dan

6E car. 355, 8.5:1, vortech head unit (10 psi) , accel superram, 42# accel injectors.

Injector constant set @ 39.96. When PE is engaged, injector pulse width stops at 7.74 ms. Wideband confirms a lean condition. Scaling the injector constant down to 35, PW stops at 10.8 ms.

Why won't the injector constant climb over 7.74? Is there a way to make it climb higher but keep injector constant the same? Currently the car can't actually get over 3-4 pounds of boost without going lean.

tequilaboy

There is a math limitation in the pulse width calculation when the AFR target dips below approx. 11:1.

See the sticky regarding the $8D pulse width limitation in the prom tuning guide section. Same problem. Similar solution.

IROCZ28dan

I checked out the tuning guide book, but could not find what you said.

Is there anyway you could post the link for me?

tequilaboy

https://www.thirdgen.org/techbb2/sho...hreadid=276420

That is the background.

Here is how you can fix it using a hex editor:

$6E:
Original code starting from 1CDB (DCDB):
DE D5 BD F4 29 FE C3 D7 13 3A 80 03 FE C3 D9

Fixed code starting from 1CDB (DCDB):
FE C3 D7 13 3A 80 03 FE C3 D9 BD F4 29 DE D5

Don't forget to save the bin to correct the checksum.

Note: I have not tested this change yet on a $6E bin. I have tested a similar change for $32B with different addresses and positive results. It should work in the same manner, since the logic is the same.

Be sure to supply plenty of fuel in PE also with the coolant temp table and not just the rpm table, or you may wind up holing a piston.

Maxing the rpm table alone will only get you 40% more fuel than 255 gm/sec at 12:1.

+73% coolant temp enrichment will give you an 8.5:1 target and is about the practical limit with 42s.

Start there. Max negative (-50) on the rpm table will get you back to a 12:1 target. Before your MAF pegs rpm wise, start adding more rpm PE (than -50) going positive above approx. 5,000 rpm and work your way up to Max positive (+50) at 6400 rpm. You can always back it down from there as required.

Depending upon your editor the rpm table may max at 100% instead of 50%. Be sure to use the maximum range going from negative to positive vs rpm with the aforementioned coolant temp table change.

Use caution and verify that you're getting close to 10 ms pulse width at 5,000 rpm and above before pushing it to 10 psi.

IROCZ28dan

It worked, I saw as much as 15ms pw so far. Unfortunately we found out that the fuel pump cannot keep up with flow needs of the engine as the wideband began to go lean and fuel pressure began to drop. But, when the car gets a better fuel pump at least now we can add fuel accordingly.

I dont know how you found that spot to change, and what you actually changed, I read through the hacks and couldnt find it listed, but thank you.

dan0617

Bringing an old thread to the top here. I just installed this hac and I think it is going to work for me. Got to test the new setup and had tons of trouble getting more fuel in up top. After about 3 lbs of boost the injector pw wouldn't climb anymore no matter what I did with pe fueling. I have 60 lb injectors, run full open loop. I added tons of fuel in the OL tables, then scaled the MAF scalars way down. This allows me to use the MAF tables all the way up to 5 lbs of boost, then I plan on letting the PE tables work on up to 15 lbs and 6400 rpms, but the PW quit climbing at about 3-4 lbs and it starts going lean. This seems like it will solve the problem. I'm hoping, because other than this issue it seems the 6E open loop with the WB datalogging hac and MAF scalars way down is fine for tuning with boost. Cheezy way of cheating the maf but as long as the engine gets what it wants it's happy, and therefore I'm happy!

tequilaboy

While this approach is effective in extending the maximum pulse width, it still has inherent limitations and is not very flexible for changing conditions, belt slip, variations in charge air temperature, etc.

A better MAF and tune is really the way to go here. I've been playing with alternative air meters in these cars for about 5 years now.

dan0617

I will likely end up going down the road you went down eventually. For now, I added an idler pulley and arm on my Vortech bracket to increase belt wrap to about 270 degrees, bought an ultra grip drilled pulley, and went with a full 8 rib setup so hopefully belt slip will be at a minimum.

I did notice with the MAF scalars down, and on a ported stock MAF, I don't max out the gms/sec in the datalogs till I hit about 5 lbs boost. That is huge compared to what it was before. I could add more fueling in the open loop tables and lower the maf scalars more but it is getting tough to blend the tables to keep from having steps in the part throttle afr's. So far so good but going much farther I'll lose part throttle tuning.

I think if your hac works as planned I'll be in good shape up to 15 lbs of boost. I'm seeing 5 lbs at about 3800 rpms give or take. I hammered the fuel pressure to it and lowered the injector constants in the tune to richen it up before I found this hac, and I saw 10 lbs of boost at 5300 rpms. This is with a free flowing 383, T trim, 7.5" crank pulley, 3" blower pulley. I'm guessing by 6200 rpms I should see about 14 or so lbs, and that is as much as I will ever want to run.

WOT tuning starts over now though, now that I found this hac and added water/meth injection.