0-60 mph - MAF graph
Burning Brakes
Joined: Jul 2006
Posts: 1,080
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From: Pittsburgh PA
I'd say hitting near 225 or so is pretty good for that motor. If i remember right, i dont think my exhaust modded L98 ever saw more than 212, but I cant be certain.
My 383 HSR was stealth ram intake (Holley Stealth Ram=HSR). TPI electronics, based on a 4bolt L98 type block. Just a simplestreet 383 build.
My 383 HSR was stealth ram intake (Holley Stealth Ram=HSR). TPI electronics, based on a 4bolt L98 type block. Just a simplestreet 383 build.
Thread Starter
Drifting
Joined: Nov 2009
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From: Perth Western Australia
St. Jude Donor '10
Drifting
Joined: Jun 2001
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From: Mass Mass
In a perfect world, you could work the math back from Grams/Sec to Horse Power, guessing at the Brake Fuel Specific and Air Fuel Ratio.
Here is a quick cut and paste from one of my spreadsheets.
Top Left Image: When my 1988 L98 was bone stock, it pulled 208 Gr/Sec from 4500 to 4800 rpm, which figures out to about 256 FWHP (seams about right?)
Bottom Left Image: Your 225 GR/Sec figures to be about 277 FWHP
Top Right Image: You have to be careful that (in the stock chip) the gm/sec value is capped in the firmware, to the values in the “Max Air Flow vs RPM” table. This can be changed with a custom chip.
Here is a quick cut and paste from one of my spreadsheets.
Top Left Image: When my 1988 L98 was bone stock, it pulled 208 Gr/Sec from 4500 to 4800 rpm, which figures out to about 256 FWHP (seams about right?)
Bottom Left Image: Your 225 GR/Sec figures to be about 277 FWHP
Top Right Image: You have to be careful that (in the stock chip) the gm/sec value is capped in the firmware, to the values in the “Max Air Flow vs RPM” table. This can be changed with a custom chip.
Race Director
Joined: Nov 2003
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From: Overland Park Kansas
2020 Corvette of the Year Finalist (appearance mods)
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Thread Starter
Drifting
Joined: Nov 2009
Posts: 1,341
Likes: 2
From: Perth Western Australia
St. Jude Donor '10
Top Left Image: When my 1988 L98 was bone stock, it pulled 208 Gr/Sec from 4500 to 4800 rpm, which figures out to about 256 FWHP (seams about right?)
Bottom Left Image: Your 225 GR/Sec figures to be about 277 FWHP
Top Right Image: You have to be careful that (in the stock chip) the gm/sec value is capped in the firmware, to the values in the “Max Air Flow vs RPM” table. This can be changed with a custom chip.
Bottom Left Image: Your 225 GR/Sec figures to be about 277 FWHP
Top Right Image: You have to be careful that (in the stock chip) the gm/sec value is capped in the firmware, to the values in the “Max Air Flow vs RPM” table. This can be changed with a custom chip.
I would appreciate it if you could expand on the airflow cap comment. Is there some tuning I can do to improve the airflow by adjusting that table?
Thread Starter
Drifting
Joined: Nov 2009
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From: Perth Western Australia
St. Jude Donor '10
Exhaust, Intake, Emissions, head shave(see my profile pictures) - Basically all the good "bang for the buck" stuff recommended by this forum.
Obama. Myself.
Obama. Myself.
Last edited by Lemme; Aug 13, 2010 at 07:21 PM.
Drifting
Joined: Jun 2001
Posts: 1,701
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From: Mass Mass
This was probably a safety feature to protect the engine from MAF errors.
Have to remember that back in the 80’s Fuel Injection was brand new, and maybe they had trouble with early versions of the MAF … who knows?
Should have no effect on calibrations until you start exceeding these chart values, then it’s time for a custom chip (to raise the limits).
255 gr/sec would be around 314 Horse Power
Just warned you about this because, at some point (despite any engine changes you made) your displayed MAF values would stop increasing, and you might be wondering why
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Thread Starter
Drifting
Joined: Nov 2009
Posts: 1,341
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From: Perth Western Australia
St. Jude Donor '10
If the value (read from your MAF) is higher than the table value for a given RPM, the firmware will use (and report) the table value.
This was probably a safety feature to protect the engine from MAF errors.
Have to remember that back in the 80’s Fuel Injection was brand new, and maybe they had trouble with early versions of the MAF … who knows?
Should have no effect on calibrations until you start exceeding these chart values, then it’s time for a custom chip (to raise the limits).
255 gr/sec would be around 314 Horse Power
Just warned you about this because, at some point (despite any engine changes you made) your displayed MAF values would stop increasing, and you might be wondering why
This was probably a safety feature to protect the engine from MAF errors.
Have to remember that back in the 80’s Fuel Injection was brand new, and maybe they had trouble with early versions of the MAF … who knows?
Should have no effect on calibrations until you start exceeding these chart values, then it’s time for a custom chip (to raise the limits).
255 gr/sec would be around 314 Horse Power
Just warned you about this because, at some point (despite any engine changes you made) your displayed MAF values would stop increasing, and you might be wondering why
I have all the chip burning / emulation gear so I can change that. What if I load in the 1989 arap bin? That still has the same MAF limit table. I note it won't let you change the maximum setting above 255 g/s! What values do you recommend?
Last edited by Lemme; Aug 13, 2010 at 08:59 PM.
Drifting
Joined: Jun 2001
Posts: 1,701
Likes: 458
From: Mass Mass
The MAF is limited to 256 levels (8 bit).
Some guy’s just top that table out to all 255’s, but I remember having some odd behavior when I did that @ WOT.
I just increased my values maybe 10 (or so) gm/sec above what the engine needed.
The emulator make changes easy, just increase the table for the rpm’s it’s limiting your readings
I figure someone had a good reason for that table existing, and I only changed it as much as needed.
Some guy’s just top that table out to all 255’s, but I remember having some odd behavior when I did that @ WOT.
I just increased my values maybe 10 (or so) gm/sec above what the engine needed.
The emulator make changes easy, just increase the table for the rpm’s it’s limiting your readings
I figure someone had a good reason for that table existing, and I only changed it as much as needed.
Thread Starter
Drifting
Joined: Nov 2009
Posts: 1,341
Likes: 2
From: Perth Western Australia
St. Jude Donor '10
The MAF is limited to 256 levels (8 bit).
Some guy’s just top that table out to all 255’s, but I remember having some odd behavior when I did that @ WOT.
I just increased my values maybe 10 (or so) gm/sec above what the engine needed.
The emulator make changes easy, just increase the table for the rpm’s it’s limiting your readings
I figure someone had a good reason for that table existing, and I only changed it as much as needed.
Some guy’s just top that table out to all 255’s, but I remember having some odd behavior when I did that @ WOT.
I just increased my values maybe 10 (or so) gm/sec above what the engine needed.
The emulator make changes easy, just increase the table for the rpm’s it’s limiting your readings
I figure someone had a good reason for that table existing, and I only changed it as much as needed.
Burning Brakes
Joined: Jul 2006
Posts: 1,080
Likes: 2
From: Pittsburgh PA
Yeah, if you hit the limits in the max air flow table, the MAF wont beable to control the fuel addition for higher flows at that rpm. PE mode will take over, and if those % increases arent correct, the motor will not be at optimal air fuel...may go to the lean side
Thread Starter
Drifting
Joined: Nov 2009
Posts: 1,341
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From: Perth Western Australia
St. Jude Donor '10
Following installation of long tube headers I thought it would be good to see what improvements have been made to the air flow.
The graph shows I have managed to hit 230 g/s at 4500 rpm compared to about 215 g/s before the headers were installed. So it is going in the right direction. Would be nice to see what happens out to 6000 rpm.
The acceleration graph looks slightly better as speed increases. Headers don't seem to have made much difference in acceleration. Maybe some tuning is required.
The graph shows I have managed to hit 230 g/s at 4500 rpm compared to about 215 g/s before the headers were installed. So it is going in the right direction. Would be nice to see what happens out to 6000 rpm.
The acceleration graph looks slightly better as speed increases. Headers don't seem to have made much difference in acceleration. Maybe some tuning is required.
Last edited by Lemme; Sep 17, 2010 at 04:43 AM.
Tech Contributor
Joined: Oct 2008
Posts: 3,729
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From: Custer, WI
Following installation of long tube headers I thought it would be good to see what improvements have been made to the air flow.
The graph shows I have manged to hit 230 g/s at 4500 rpm compared to about 215 g/s before the headers were installed. So it is going in the right direction. Would be nice to see what happens out to 6000 rpm.
The graph shows I have manged to hit 230 g/s at 4500 rpm compared to about 215 g/s before the headers were installed. So it is going in the right direction. Would be nice to see what happens out to 6000 rpm.
Thread Starter
Drifting
Joined: Nov 2009
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From: Perth Western Australia
St. Jude Donor '10
I think I am a fair way off that yet. So it serves a useful purpose at the moment. Actually there are quite a few pegs in the rpm vs max g/s table that have to be watched as well before one gets to 255 g/s..
Thread Starter
Drifting
Joined: Nov 2009
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From: Perth Western Australia
St. Jude Donor '10
When I overlay the g/s limits over the graph before I put the headers on it can be seen that they are not far away
Then after I put the headers on
Getting very close. Need to raise the limits in the tune.
Then after I put the headers on
Getting very close. Need to raise the limits in the tune.
Last edited by Lemme; Sep 17, 2010 at 04:14 AM.
Le Mans Master
Joined: Apr 2005
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From: The Old Dominion
Le Mans Master
Joined: Apr 2005
Posts: 6,413
Likes: 9
From: The Old Dominion
You're dead on!! Maximum airflow, and maximum volumetric efficiency, occur at peak torque!!I believe you will see the MAF values at WOT map out a graph that is proportional to the horsepower curve of the engine.
Thread Starter
Drifting
Joined: Nov 2009
Posts: 1,341
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From: Perth Western Australia
St. Jude Donor '10
The latest graph is at WOT and shows actual g/s is very close to the ecm limits of g/s. The original graph wasn't quite WOT but was pretty close. I was trying not to spin the wheels.
Le Mans Master
Joined: Apr 2005
Posts: 6,413
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From: The Old Dominion
It's too bad the automatics can't be controlled better, it would be more interesting to see it run solidly past the power peak. I feel like you also get a smoother graph if you can make a run in a higher gear, but then you lose out on the low RPM part of the graph.