350 EFI TBI Mods, cam, heads, intake, tune, 383?
07-31-2018, 05:15 PM
#71
Registered
Although I don't go by gaskets..good job.
Back when the dinosaurs roamed, we had a set of SBC raised D port heads (I believ they where Bowtie Aluminums - can't remember which 'Phase' )on an engine that was underpeforming. After dicking with many tuning changes during 'track days' - ie: practice days - we got the engine on the dyno and the motor was a pig. You named it, we thru at it - still sucked. Was about 40hp off.
Headers did not match these ports. I did the 'old gasket making trick with a manilla folder and a small pean hammer) Part of the welded port to header flange was blocking off the port. Yeh ! Rolleye's...got that fixed wih the custom header guy ($$$$$$$) and wallah. Right where it should have been. The Chevrolet Power Book got read real well after that and for each new addition that came out. Dammit. LOL.
So, anyway, good to do with any header or marine exhaust manifold vs head used just to make sure. Small things can ruin your day or make you a hero.
Back when the dinosaurs roamed, we had a set of SBC raised D port heads (I believ they where Bowtie Aluminums - can't remember which 'Phase' )on an engine that was underpeforming. After dicking with many tuning changes during 'track days' - ie: practice days - we got the engine on the dyno and the motor was a pig. You named it, we thru at it - still sucked. Was about 40hp off.
Headers did not match these ports. I did the 'old gasket making trick with a manilla folder and a small pean hammer) Part of the welded port to header flange was blocking off the port. Yeh ! Rolleye's...got that fixed wih the custom header guy ($$$$$$$) and wallah. Right where it should have been. The Chevrolet Power Book got read real well after that and for each new addition that came out. Dammit. LOL.
So, anyway, good to do with any header or marine exhaust manifold vs head used just to make sure. Small things can ruin your day or make you a hero.
07-31-2018, 06:35 PM
#72
Platinum Member
Platinum Member
As you can see above, nowhere in my timing table do I have 36 degrees of timing. Here is a picture of my timing table, the best its ran so far. Still get some knock. This is about as high as it gets, but I can hear and feel it when it happens. I pulled a couple plugs, last night, they look good to me, but wonder if maybe I should go a step cooler. The plugs are Autolite 4063's which is about an 8 heat range in an NGK. I am thinking about going to a BR9ES NGK, colder plug.
07-31-2018, 08:02 PM
#73
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articfriends (06-29-2023)
07-31-2018, 08:09 PM
#74
Did some tuning this past weekend. I ended up finding an original set of GM 454 TBI injectors I had in my tool box, so I swapped them out, I was suspecting some fueling issues with the aftermarkets. All that did was lean my entire tune out a little and pretty much forced me to start over. So I started over with the stock .bin. Initial timing at 8 degrees, and went from there. My fueling is very close, 12-12.5 everywhere except idle which is 13.5. I get a little blip of spark knock when I accelerate out of the hole. I can not go full throttle out of the hole or it knocks, I have to ease into it. If I hammer it, the AFR goes really rich, like the PCM has an acceleration enrichment being activated. But if I ease it out of the hole AFR stays around 12 and she takes off, with maybe just a blip of knock. It also goes rich when I am decelerating. I have tried lowering the BPW in the 40 KPA column, that helped.
I see there are some scalars that may or may not help with this
Delta TPS AE Multiplier
DE Delta TPS Threshold
AE Delta TPS Threshold
DE TPS Scalar Factor Multiplier
When I started over with the tune I forgot to raise the fuel cut off form 4800 to 5500, and could not figure out why around 4800 the wide band would go nuts, and the boat would knock like crazy. The MEFI-1 has a crappy way of doing this. It cuts fuel, but not timing, making the boat knock like crazy. Anyway, I finally was like oh yeah...duh! I changed the fuel cut off to 5500 RPM.
Here is the other issue I am having. The log from scanner pro does not match the timing I have in my main timing table. There is something advancing the timing.
I see there are some scalars that may or may not help with this
Delta TPS AE Multiplier
DE Delta TPS Threshold
AE Delta TPS Threshold
DE TPS Scalar Factor Multiplier
When I started over with the tune I forgot to raise the fuel cut off form 4800 to 5500, and could not figure out why around 4800 the wide band would go nuts, and the boat would knock like crazy. The MEFI-1 has a crappy way of doing this. It cuts fuel, but not timing, making the boat knock like crazy. Anyway, I finally was like oh yeah...duh! I changed the fuel cut off to 5500 RPM.
Here is the other issue I am having. The log from scanner pro does not match the timing I have in my main timing table. There is something advancing the timing.
Check your F1 Slope value. That may be the issue with your WOT advance as Arctic alluded to.
Just looked closer at your timing table. I think you have too much in the 1200 rpm 60 kPa cell. This might be the source of your slight off throttle knock. Might want to tweek that cell and a few around it down a touch.
Last edited by Trash; 07-31-2018 at 11:10 PM.
08-01-2018, 08:14 AM
#75
Registered
Thread Starter
The AFR going rich under heavy acceleration is normal, I leave mine unless it's less than 11.0.
Check your F1 Slope value. That may be the issue with your WOT advance as Arctic alluded to.
Just looked closer at your timing table. I think you have too much in the 1200 rpm 60 kPa cell. This might be the source of your slight off throttle knock. Might want to tweek that cell and a few around it down a touch.
Check your F1 Slope value. That may be the issue with your WOT advance as Arctic alluded to.
Just looked closer at your timing table. I think you have too much in the 1200 rpm 60 kPa cell. This might be the source of your slight off throttle knock. Might want to tweek that cell and a few around it down a touch.
Here is what I found in the F1 Slope table. Should I just zero it out and disable it?
08-01-2018, 01:42 PM
#76
There is a formula you can use for calculating the F1 extension but I don't recall it off hand.
08-01-2018, 01:52 PM
#77
Registered
Thread Starter
Yours .00099*4600=4.55
I think I am getting way more advance than you are. I may zero it out or try your numbers.
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articfriends (06-29-2023)
08-01-2018, 02:46 PM
#78
The F1 slope extension is the slope of the ignition curve as it 'leaves' the boundaries of the spark table.
The UPPER RPM THRESHOLD is where the spark slope will stop increasing.
To calculate this slope take the UPPER RPM THRESHOLD value and subtract the upper rpm in the table, 3600 in this case.
5000-3600=1400
Take this number and multiply it by the F1 slope extension value.
1400 x .00297 = 4.158 degrees
For your current tune it will add 4.158 degrees of timing from 3600-5000. Above 5000 it won't add anything more. That's the UPPER LIMIT. At 75 kPa and your existing advance at that point (between 32.7 and 33 deg) this 4 deg of additional timing is giving you the 36 deg of timing ScannerPro is showing you. I'm sorry I didn't have the formula earlier.
IF I was you, I would leave your timing at the upper end rpm (3600) and cut your slope value and upper limit value.
I would also lower the timing in the 1200,1600, 2000 rpm cells in the 60 kPa column.
As another option you could lower your 3600 rpm advance values and play with the F1 parameter. I don't do that because in most cases being all in around 3600 is sufficient.
Last edited by Trash; 08-01-2018 at 02:50 PM.
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articfriends (06-29-2023), Paxtonspeed (08-01-2018)
08-01-2018, 03:56 PM
#79
Registered
Thread Starter
Your calculations are off because you are using the wrong formula. I dug into my notes to find the correct formula.
The F1 slope extension is the slope of the ignition curve as it 'leaves' the boundaries of the spark table.
The UPPER RPM THRESHOLD is where the spark slope will stop increasing.
To calculate this slope take the UPPER RPM THRESHOLD value and subtract the upper rpm in the table, 3600 in this case.
5000-3600=1400
Take this number and multiply it by the F1 slope extension value.
1400 x .00297 = 4.158 degrees
For your current tune it will add 4.158 degrees of timing from 3600-5000. Above 5000 it won't add anything more. That's the UPPER LIMIT. At 75 kPa and your existing advance at that point (between 32.7 and 33 deg) this 4 deg of additional timing is giving you the 36 deg of timing ScannerPro is showing you. I'm sorry I didn't have the formula earlier.
IF I was you, I would leave your timing at the upper end rpm (3600) and cut your slope value and upper limit value.
I would also lower the timing in the 1200,1600, 2000 rpm cells in the 60 kPa column.
As another option you could lower your 3600 rpm advance values and play with the F1 parameter. I don't do that because in most cases being all in around 3600 is sufficient.
The F1 slope extension is the slope of the ignition curve as it 'leaves' the boundaries of the spark table.
The UPPER RPM THRESHOLD is where the spark slope will stop increasing.
To calculate this slope take the UPPER RPM THRESHOLD value and subtract the upper rpm in the table, 3600 in this case.
5000-3600=1400
Take this number and multiply it by the F1 slope extension value.
1400 x .00297 = 4.158 degrees
For your current tune it will add 4.158 degrees of timing from 3600-5000. Above 5000 it won't add anything more. That's the UPPER LIMIT. At 75 kPa and your existing advance at that point (between 32.7 and 33 deg) this 4 deg of additional timing is giving you the 36 deg of timing ScannerPro is showing you. I'm sorry I didn't have the formula earlier.
IF I was you, I would leave your timing at the upper end rpm (3600) and cut your slope value and upper limit value.
I would also lower the timing in the 1200,1600, 2000 rpm cells in the 60 kPa column.
As another option you could lower your 3600 rpm advance values and play with the F1 parameter. I don't do that because in most cases being all in around 3600 is sufficient.
I wonder why they just didn't give the spark table more resolution, seems like it would be the easier way to do it.
08-01-2018, 06:45 PM
#80
The bigger problem is lack of available documentation on all the parameters and what they actually do IF even implemented. Hence F1 in this situation is confusing at the outset.
If you had a table that had spark break out points in 50 rpm increments and every 1 kPa that would be a PITA to monkey with. With MEFI 3 and up you have multiple tables covering a broader rpm and kPa breakouts AND they must match on the overlap points. Gets a little laborious when first playing around with it. In addition much of the table is never even used, nor is the motor capable of operating in that range. In the end some of the added fidelity is non-value added, or simply stated, useless. For example does a motor even operate at 10Kpa and 200 rpm? Nope.
Keep us posted. The work you are doing is fun to watch and we all learn something in the end.
Last edited by Trash; 08-01-2018 at 06:47 PM.
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