Working on getting low speed/idle dialed in, it's working about as good as it could get with a monster cam, 253/261, .644/.624, the A/F at idle is around 17:1 A/F, I'm thinking it won't get much better, I believe it is not burning all the way, giving me the "lean" reading, although it stinks of fuel. I tried searching, couldn't find what I'm looking for, does this sound right? BTW, the specs are in another thread here, "408 opinions"
That's a ton of overlap, it's gonna look lean from all of that fresh air making it's way out through the open exhaust valve. It fools your wideband. Without a multi gas analyzer you will be tuning by idle quality errrrr feel. The overlap is gonna make it stink, but if you have been adding fuel trying to get the AFR down, then it could be too fat. It's just gonna read lean. Fortunately this is only at idle and no significant load. Start to dial some fuel back out and see how it acts.
This car will clearly require open loop tuning; at least through it's range of significant overlap. Closed loop will make it drown itself.
Thanks for the feed back, that's what I figured was happening. The idle is steady, (relatively, LOL), doesn't stall. It will probably stay in open loop, I've got to work a bit on low speed, light load some more, it bucks a bit, don't know how much better I can make it, the owner isn't quite as picky as I am, but I'm planning on working the timing some, good thing I told him in the beginning this would take some time.
Add 30* across the board to your injector timing boundary...
Agreed, you need to shift the end of injection point to reduce the amount of short circuiting in the fuel delivery. You are seeing a significant difference between the AFR delivered to the cylinder and what the real AFR for combustion is. Delaying the injection timing will mean less of the fuel has the opportunity to go out the exhaust valve during overlap.
The cylinder itself still wants lambda=1.00 for combustion.
My boundary # is at 6.5, so I should add 30* and end up with 36.5* correct?
I am interested to see how much this change alone will make in the fueling reading, quite interesting.
Sulski Performance Tuning
2000 WS6 M6 - LS6 (long block, refreshed top end), 10.8:1 CR, 90 mm ported FAST, Exo-Skel, 227/232 cam, QTP HVMC, EWP, GMMG, 9" w/4.11s
2018 Sierra SLT 5.3L A8 - Airaid intake tube, GM Borla catback, L86 Intake/Ported TB
Yeah, I'm real interested in the results also, I was at work when I read both responses, couldn't quite remember that parameter at all! Now that I think about it, it makes perfect sense, wait a bit for the exhaust to finish closing, now I wonder how the rest of the fueling will behave. I'll definitely post up the results. I had planned on doing the car tonight, but the owner had to go into work, police stuff. (Good customer to have, hee hee), now I'll have to wait a couple of days to check out how this works, damn!
It'll still read leaner in the pipe than it actually is in the cylinder. Moving the injector boundary in doesn't change overlap in open valve time. It seemed to take a little of the smell out in the one of the two cars I played with it onThis kind of thing makes me want equipment that I can't afford or really financially justify
Greg I want to get into your class pretty badly; I tried to get there late last June but was unable. I am hoping things work out better this year. Thanks for staying active in the forums while having so little free time.
what effect does this have on part throttle and WOT? Does shifting the injection point require retuning other areas?Originally Posted by eficalibrator
Greg, does this have any impact with engine "run on" after the ignition is terminated with a high overlap camshaft?
HT
Full Service GM Late Model Performance Facility
www.redline-motorsports.net
Follow US on FACEBOOK!
Follow us on Instagram! redline_motorsports
Ah... That sux
You have the older style ECM (pre-E38) that measures injection boundary in increments up to 8, not degrees ATDC.
Mmmmm... you will need an oscilloscope
Try changing the boundary EOIT to 6.833 (across the board)
At WOT? Not much, if at all (depends on your duty cycle)
Part throttle? Significantly more so. If setup correctly, more torque for less fuel. Usually the gains are only apparent up to around 3000RPM but again it depends on your duty cycle and cam.
Hi,
I have tried several settings of the boundary on the older pcm.
Does anyone know what the formula is to calculate the correct boundary for a cam? I have a 224/228 114 .581
thanks
Brian
I'm not sure what you mean by "across the board", there is only one number, when I click on it, the 6.5 highlights in the Boundary box, there are two others below it, one is "normal", target vs ect, the second is "makeup", which is also vs ect. If I read 'em right, both "normal" and "makeup" are in addition to the boundary, "normal"- "The end of injection target measured in reference periods after the injection boundary that the normal injection pulse should finish."
"Makeup"-" The end of injections target measured in reference periods after the injection boundary that the makeup injection pulse should finish."
My head's starting to hurt!
Unfortunately this ECU is not intuitive to calibrate unless you have an oscillosope
Set the Normal EOIT to 5.883 across the board.
I have a smaller cam with 6 degrees of overlap (224/230) and get some fuel smell at idle... would you recommend adding to the injector timing boundry and retune? I'm not tripping any codes.
Now I'm a bit confused, MNR-0, you first said to set the boundary @ 6.883, then to set it @ 5.883, the setting in the car at the moment, (as I type this, it occurs that I should probably check a STOCK tune), if I am at 6.5, the 6.883 makes it later, which makes sense, (assuming that is a stock setting!?), 5.883 would be sooner, could you expand a bit on this along with the normal and makeup settings.
OK. This is not easy to understand because your ECU makes it difficult to correlate to real world crank angles.
Note I should have said raise it by 0.667 (an estimate to shift EOIT boundary 30* later)
You agree that a bigger cam extends the overlap period hence more fuel is wasted through the exhaust. Thus we need to alter injection boundaries to bring idle back under control and reduce exhaust emissions (a tip for cammed cali cars and their emissions laws
The size of your cam dictates where it needs to be, as does the size of your injectors and efficiency of your engine. Requirements will be different for each car - even with the same cam as injector duty cycles can vary depending on their size.
With this ECU there is no load based scalar as offered in the newer E38 ECUs. So this will affect all loadpoints. But if you want to get idle better for a very large cam, apart from tuning the usual AFR and timing advance, there is not much else available for you to try.
So... you can do this many ways (as always) but if you want your injection boundary to be consistent whether cold or hot, set the Normal EOIT to the same value across the board (whatever it is plus 0.667). If you want the injection boundary to vary as ECT rises, then leave all else stock and just lift the single boundary value by 0.667.
Now there is also a make-up pulse, which from what I can see in the stock calibration, does not seem to be calibrated for use (my opinion). I would try copying over the normal EOIT and lifting these values again by 1.334. This should allow enough time for the make-up pulse to fire (under transient conditions) and assist in reducing lean spots in tip-in helping reach commanded AFR quicker.
You really have to verify shifts in crank angle with an oscilloscope, but from my observations each increment is about 45* crank angle (roughly speaking). Remember we are talking about reference pulses here, not crank angles.
You will likely have to revisit your VE table too, but if in closed loop, it will trim.
If after all this playing around you cannot see any useful gains, then set it back to stock and forget about it or go see an EFI diagnostics centre with a multi-channel that can monitor CKP (crank), EOIT (injector) and ICP (ignition).
OK, I think I'm following this, would you suggest I try leaving the injection boundary consistent first, or vary it first, or either way first doesn't matter? As far as the make up pulse, copy the normal #s into the make up section, or copy over the normal #s with the make up #s, and then add 1.334? Why would I add 1.344 if I am adding .667 to the single boundary value? Don't know what it means but, .667 and 1.344 are nearly equal amounts away from 1, just wondering. BTW, THANKS for the time and patience!
Reply With Quote
