MAF Sensor Voltage Dropping At High RPMs
Thread Starter
Melting Slicks
Joined: Jun 2013
Posts: 3,065
Likes: 39
You have to look at the frame numbers first before deciding the order that they are in. The first chart is in order from bottom to top, not top to bottom like the other one. Just the way that I organized it in the spread sheet.
Safety Car
Joined: Sep 2001
Posts: 4,157
Likes: 554
From: Glenbeulah Wi
I'm sorry, but I have to say this again. In the first chart you were clearly decelerating. TPS went from wide open to closed and your RPMs dropped. Pulse width should have dropped. The fact that you don't see both events on the same frame is likely because of the slow data rate from the ECM. I would call this a normal condition.
Daniel, people are trying to help you but either you do not want to listen or you are have a preconceived idea on what the problem is and you are not keeping an open mind. Put together a real test plan and go get some real data. Not wanting to make a third gear pull because you do not have the room where you live is not an answer. Go find a suitable spot somewhere else and get the data.
Melting Slicks
Joined: Mar 2008
Posts: 2,141
Likes: 76
From: Santa Maria, CA
With the ECM you have, data logs are not as fast as the commands being sent by the ECM. Sensor reactions will also vary. When the ECM sends a frame snapshot to your laptop, each column in the log is the last value received from the sensors. It is common for things to be a bit out of sync during transitions.
Thread Starter
Melting Slicks
Joined: Jun 2013
Posts: 3,065
Likes: 39
Daniel, people are trying to help you but either you do not want to listen or you are have a preconceived idea on what the problem is and you are not keeping an open mind. Put together a real test plan and go get some real data. Not wanting to make a third gear pull because you do not have the room where you live is not an answer. Go find a suitable spot somewhere else and get the data.
Thread Starter
Melting Slicks
Joined: Jun 2013
Posts: 3,065
Likes: 39
Well. Someone was in my way but I still managed to get 2 data logs. Almost hit that guy though. Thankfully I didn't. But boy did it get up there quick...
Anyway, the first time around I didn't get a log passed 5100.
Second time around I got up to 5425. At this RPM I know the car goes lean.
It appears that you guys were right about some funny business going on with the previous logs. In these logs it appears that the MAF gms/sec is not dropping. So I guess it has to be something else. Let me know what you guys think.
Thanks
Anyway, the first time around I didn't get a log passed 5100.
Second time around I got up to 5425. At this RPM I know the car goes lean.
It appears that you guys were right about some funny business going on with the previous logs. In these logs it appears that the MAF gms/sec is not dropping. So I guess it has to be something else. Let me know what you guys think.
Thanks
Safety Car
Joined: Sep 2001
Posts: 4,157
Likes: 554
From: Glenbeulah Wi
Well. Someone was in my way but I still managed to get 2 data logs. Almost hit that guy though. Thankfully I didn't. But boy did it get up there quick...
Anyway, the first time around I didn't get a log passed 5100.
Second time around I got up to 5425. At this RPM I know the car goes lean.
It appears that you guys were right about some funny business going on with the previous logs. In these logs it appears that the MAF gms/sec is not dropping. So I guess it has to be something else. Let me know what you guys think.
Thanks
Anyway, the first time around I didn't get a log passed 5100.
Second time around I got up to 5425. At this RPM I know the car goes lean.
It appears that you guys were right about some funny business going on with the previous logs. In these logs it appears that the MAF gms/sec is not dropping. So I guess it has to be something else. Let me know what you guys think.
Thanks
You can try adding more fuel in the tune but to see if there is any head room in the current injectors but my thought is no. One scan shows a pulse width above 11ms at 5100 RPm, the other shows above 10.6 ms at 5400 RPM, maybe there is a little bit left but with the injector cycle time I doubt it.
Last edited by bjankuski; Oct 30, 2014 at 06:14 PM.
Thread Starter
Melting Slicks
Joined: Jun 2013
Posts: 3,065
Likes: 39
Daniel, Please go back and read my last few posts, you are out of injector, you need bigger injectors as displayed by your pulse widths. That is the bare minimum that you need, once you put in the larger injectors that can supply more fuel you may need a larger pump but that will be determined by watching your fuel pressure with the new injectors.
Safety Car
Joined: Sep 2001
Posts: 4,157
Likes: 554
From: Glenbeulah Wi
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Thread Starter
Melting Slicks
Joined: Jun 2013
Posts: 3,065
Likes: 39
Melting Slicks
Joined: Mar 2008
Posts: 2,141
Likes: 76
From: Santa Maria, CA
60 lb would be insane. The problem with too big of an injector is that you will not be able to get the pulse width short enough at idle. I've been there and done that.
Melting Slicks
Joined: Mar 2008
Posts: 2,141
Likes: 76
From: Santa Maria, CA
Well. Someone was in my way but I still managed to get 2 data logs. Almost hit that guy though. Thankfully I didn't. But boy did it get up there quick...
Anyway, the first time around I didn't get a log passed 5100.
Second time around I got up to 5425. At this RPM I know the car goes lean.
It appears that you guys were right about some funny business going on with the previous logs. In these logs it appears that the MAF gms/sec is not dropping. So I guess it has to be something else. Let me know what you guys think.
Thanks
Anyway, the first time around I didn't get a log passed 5100.
Second time around I got up to 5425. At this RPM I know the car goes lean.
It appears that you guys were right about some funny business going on with the previous logs. In these logs it appears that the MAF gms/sec is not dropping. So I guess it has to be something else. Let me know what you guys think.
Thanks
When you were doing the tune I was concerned about your approach. After adjusting the MAF tables you tuned open loop AFR using the coolant temperature table. I don't recall you adjusting the PE tables.
I'm not convinced these injectors are too small. My 396 is producing more power than your 350 and I'm using the same 24# injectors. I know mine is not leaning out. The max I have seen for pulse width was 11.2. At that reading my O2 was .886.
Last edited by cumbercr; Oct 30, 2014 at 07:28 PM.
Thread Starter
Melting Slicks
Joined: Jun 2013
Posts: 3,065
Likes: 39
If I read this table correctly, your O2 readings are rich. But you say you know its lean.
When you were doing the tune I was concerned about your approach. After adjusting the MAF tables you tuned open loop AFR using the coolant temperature table. I don't recall you adjusting the PE tables.
I'm not convinced these injectors are too small. My 396 is producing more power than your 350 and I'm using the same 24# injectors. I know mine is not leaning out. The max I have seen for pulse width was 11.2. At that reading my O2 was .886.
When you were doing the tune I was concerned about your approach. After adjusting the MAF tables you tuned open loop AFR using the coolant temperature table. I don't recall you adjusting the PE tables.
I'm not convinced these injectors are too small. My 396 is producing more power than your 350 and I'm using the same 24# injectors. I know mine is not leaning out. The max I have seen for pulse width was 11.2. At that reading my O2 was .886.
When I changed the fuel pressure, I set the P.E. AFR Vs coolant temp table back to stock to avoid over fueling it, but kept the 20% more fuel at 4000-6400. When this happened it is I believe 11:1 at low RPMs and 12.5:1 at high RPMs. So when I retune the MAF tables for 50 PSI, I'm not sure if I'll still be able to achieve 12.5:1 at high RPMs. I'd like to get 12.5:1 all across the board.
Thread Starter
Melting Slicks
Joined: Jun 2013
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If it needs injectors, what's the biggest size I should go with? And also, how do I know what injector offset to set it to?
Drifting
Joined: May 2007
Posts: 1,552
Likes: 324
From: Mid Ohio
60lb is too big for a NA sbc. That size is only for SC, turbo, or dry shot type of power adders.
Injector size just depends on where you want to go in the future. Maybe find a used set thats 15-20% bigger than where you are right now, clean them yourself (youtube search), and use them as a stop gap until you go big.
There is a trick you can do to run a big injector though. If you mix 1.5-2.0oz of 100% acetone for every 10gal of fuel it will help atomize at lower rpms. (I've done a lot of trials, data logging, and tuning for 10+ yrs using acetone. Trust me it works. Just kinda a pain to always be putting in 2-4oz every time you fill up)
And btw.. at WOT 2oz to 10gal ratio will lean the A/F right at 0.5
Injector size just depends on where you want to go in the future. Maybe find a used set thats 15-20% bigger than where you are right now, clean them yourself (youtube search), and use them as a stop gap until you go big.
There is a trick you can do to run a big injector though. If you mix 1.5-2.0oz of 100% acetone for every 10gal of fuel it will help atomize at lower rpms. (I've done a lot of trials, data logging, and tuning for 10+ yrs using acetone. Trust me it works. Just kinda a pain to always be putting in 2-4oz every time you fill up)
And btw.. at WOT 2oz to 10gal ratio will lean the A/F right at 0.5
Last edited by wydopnthrtl; Oct 30, 2014 at 10:01 PM.
Race Director
Joined: Apr 2002
Posts: 10,036
Likes: 346
From: Anaheim CA
I would like to see column labels in your data logs. You can then freeze the top row (highlight row 2 and then click "Freeze" under the Window menu) and they will always be visible even when you scroll.
I couldn't figure out what some of those columns are. Column E looks like it might be BLM cell number. Column F and G look like they have way too much resolution. Your scan tool might be lying to you. For example, an 8 bit number can be any value between 0 and 255. There is no way to have fractional values (numbers after the decimal point). The ECM gets around this limitation by rounding the values. That's why the best resolution you can get on RPM is 25. RPM is scaled to fit in an 8 bit number.
I couldn't figure out what some of those columns are. Column E looks like it might be BLM cell number. Column F and G look like they have way too much resolution. Your scan tool might be lying to you. For example, an 8 bit number can be any value between 0 and 255. There is no way to have fractional values (numbers after the decimal point). The ECM gets around this limitation by rounding the values. That's why the best resolution you can get on RPM is 25. RPM is scaled to fit in an 8 bit number.
Safety Car
Joined: Sep 2001
Posts: 4,157
Likes: 554
From: Glenbeulah Wi
Daniel, I agree that 60 lb injectors are too large, I would shot for 30lb to 36 lb injectors. That size injector will handle 480 HP to 580 HP. I am not sure what you mean when you say offsets. If you mean injector offset vs. battery voltage and low pulse width correction you get that from the information supplied by the injector manufacture. I assume you are asking how to scale the injectors for the additional size so you do not get too much fuel. That is adjusted in the injector pulse width vs. load table. You scale the injector by the percentage of change from the original injector to the new injector. Example if you go from 24 lb injectors to 30 lb injectors the percentage of change is ((30-24)/24 = .25 or 25%. That means you would reduce the entire pulse width vs. load table by 25% to get the injectors scaled in close. To do this multiply the entire pulse width vs. load table by .75
Thread Starter
Melting Slicks
Joined: Jun 2013
Posts: 3,065
Likes: 39
Daniel, I agree that 60 lb injectors are too large, I would shot for 30lb to 36 lb injectors. That size injector will handle 480 HP to 580 HP. I am not sure what you mean when you say offsets. If you mean injector offset vs. battery voltage and low pulse width correction you get that from the information supplied by the injector manufacture. I assume you are asking how to scale the injectors for the additional size so you do not get too much fuel. That is adjusted in the injector pulse width vs. load table. You scale the injector by the percentage of change from the original injector to the new injector. Example if you go from 24 lb injectors to 30 lb injectors the percentage of change is ((30-24)/24 = .25 or 25%. That means you would reduce the entire pulse width vs. load table by 25% to get the injectors scaled in close. To do this multiply the entire pulse width vs. load table by .75
So now as I understand, '85 injectors were rated at 24 lbs at 38 PSI. Are these Bosch III also rated 24 lbs at 38 PSI?
When I adjusted my fuel pressure to 50 I think that puts them at somewhere around 27. So would I need to adjust the injector pulse width table for that before I continue tuning?
And then, should I use the rating of the new injectors at 50 PSI instead of 43.5 when adjusting the injector pulse width vs load table?
Safety Car
Joined: Sep 2001
Posts: 4,157
Likes: 554
From: Glenbeulah Wi
Okay. These are my current injectors. http://fuelinjectorconnection.com/sh...p?productid=57
So now as I understand, '85 injectors were rated at 24 lbs at 38 PSI. Are these Bosch III also rated 24 lbs at 38 PSI?
When I adjusted my fuel pressure to 50 I think that puts them at somewhere around 27. So would I need to adjust the injector pulse width table for that before I continue tuning?
And then, should I use the rating of the new injectors at 50 PSI instead of 43.5 when adjusting the injector pulse width vs load table?
So now as I understand, '85 injectors were rated at 24 lbs at 38 PSI. Are these Bosch III also rated 24 lbs at 38 PSI?
When I adjusted my fuel pressure to 50 I think that puts them at somewhere around 27. So would I need to adjust the injector pulse width table for that before I continue tuning?
And then, should I use the rating of the new injectors at 50 PSI instead of 43.5 when adjusting the injector pulse width vs load table?
Thread Starter
Melting Slicks
Joined: Jun 2013
Posts: 3,065
Likes: 39
Bosch III are usually rated at 43.5 PSI, as far as adjusting the pulse width table with your current injectors it will not make any difference, the injectors are too small, the current values you are using are fine. When you get new larger injectors you will want to adjust the table.
Melting Slicks
Joined: Mar 2008
Posts: 2,141
Likes: 76
From: Santa Maria, CA
You seem to have jumped right to "my injectors are too small". You guys need to look at the O2 sensor readings. When I see readings above 1 volt, that thing is running rich in WOT. So I see no evidence the engine is leaning out. If you adjust the tune to bring those down to upper .800's, you will see shorter pulse widths.
But if you like spending money proceed as you are doing.