EFI, Alpha-N vs Speed Density fueling Strategies

pbp1 · 03-09-2014, 03:08 AM

In my opinion, yes. But this is especially true going from one track to another .

kdanner · 03-09-2014, 03:20 AM

David, is there any particular reason aftermarket solutions aren't MAF based? These new Mustangs I've been working with that also run closed loop fueling at WOT just crank out beautiful consistent fuel curves every time. It's so easy and they look so good it makes it look like I am better at this than I really am.

pbp1 · 03-09-2014, 03:29 AM

MAF sensors do a very good job of measuring airflow but their weakness in a race application is that they are only accurate over a very narrow range so it would take a sensor/housing designed specifically for the application. In the case of stock and super stock, we are flowing much more air than a stock engine therefore we have moved out of their effective range. Also, since these classes are throttle body limited, anything in the airstream before the throttle body is undesirable. In stock or modified street vehicles, Mass Air systems do a great job. They just have no place in this type of racing in my opinion.

Ed Wright · 03-09-2014, 09:27 AM

I think MAF is a better deal. I work with GM's factory systems every day, and the MAF system is much more forgiving for weather, elevation and engine combo changes. Different manifolds, headers, collectors, going to Denver, seldom require any tuning changes.

On many cars, (like mine) where would you put it? Going to put an air filter on it? The GM (don't know about Ford) sensors have heated wires. They glow red when running. They have to remain perfectly clean, or the calibration changes. Then you usually end up with elbows in the ducting to accommodate an air filter. You can't have dust, and who knows what else in Louisiana (Joke) cooked on those heated wires.
Speed Density done correctly compensates pretty well.

ken robinson · 03-09-2014, 12:25 PM

For odd ball combos (2.3 ford turbo)that do you do for a cal map to start with if one is not available ? Or do most of the company like FAST have a start up cal map on file you just need to call when ordering the the ecu .

RacingRicki · 03-09-2014, 12:53 PM

David,

You mentioned a racer that is running in speed density open loop. If it is open loop, how is it that the ECU is compensating for air changes? I thought open loop meant that there was no compensating going on.

I run the "classic FAST" system in Alpha-N mode open loop. With that setup, closed loop would use the o2 sensor to correct the fuel. In open loop it doesn't. How is this different with speed density? Does speed density use the o2 sensor at all?

Also, I was told that even though I run in open loop Alpha-N that there are tables that I can't see that are compensating for barometric changes much like a carburetor does naturally. Is this true?

pbp1 · 03-10-2014, 01:59 PM

Ken, one of the beauties of Speed Density is that since it is really based on airflow, it is relatively easy to start with a basic VE table and run it in closed loop and tune it in based on the O2 correction that you see in your datalogs. There are a lot of baseline tuneups in our C-Com software to chose from and while none of them are specifically for a 4 cyll, it would be very simple to start with one of those and make a few changes to give you a close starting point. I would be glad to put a tune together for you, send me a message if you are interested in this.
David Page
FAST

SS3718 · 03-11-2014, 07:59 AM

David, I just wanted to say thanks for sharing and taking the time to post on this topic. As a current FAST customer, not only do you have a great product but the customer service that you provide is second to none and this post is yet another example of the service/tech support that your team provides.

Thank you and see you at the track in 2014,
Nick Morris
SS 3718
GT/FA

Rich Biebel · 03-11-2014, 08:26 AM

How do you add a cam sync sensor to a GM LT-1 from the mid '90s ?

I raced one and used bank to bank but my Accell Gen VII could run in sequential. I ran a crank trigger with a gutted optispark dist.and was not sure how to add a cam synch sensor.

I struggled to tune my car on my own and really needed a pro's help and some dyno time.....running in sequential sounded like it would make more sense.....

Ed Wright · 03-11-2014, 09:01 AM

I used an Opti for a while. Not gutted. It can be done with the Opti electronics, although I nener tried it. Some of the Stocker guys are doing that. I now use an MSD dist with cam sync. I didn't find sequential to be the huge HP deal some make it out to be. Still, 5 to 7 hp is worth the effort. I had 2 cyls 9 & 10% lean, the rest were 2 & 3% off.

03-09-2014, 03:08 AM	#1
pbp1 Junior Member Join Date: Mar 2013 Posts: 80 Likes: 12 Liked 27 Times in 6 Posts	Re: EFI, Alpha-N vs Speed Density fueling Strategies In my opinion, yes. But this is especially true going from one track to another .

03-09-2014, 03:20 AM	#2
kdanner Member Join Date: Nov 2003 Location: Austin, TX Posts: 221 Likes: 50 Liked 38 Times in 17 Posts	Re: EFI, Alpha-N vs Speed Density fueling Strategies David, is there any particular reason aftermarket solutions aren't MAF based? These new Mustangs I've been working with that also run closed loop fueling at WOT just crank out beautiful consistent fuel curves every time. It's so easy and they look so good it makes it look like I am better at this than I really am.

03-09-2014, 03:29 AM	#3
pbp1 Junior Member Join Date: Mar 2013 Posts: 80 Likes: 12 Liked 27 Times in 6 Posts	Re: EFI, Alpha-N vs Speed Density fueling Strategies MAF sensors do a very good job of measuring airflow but their weakness in a race application is that they are only accurate over a very narrow range so it would take a sensor/housing designed specifically for the application. In the case of stock and super stock, we are flowing much more air than a stock engine therefore we have moved out of their effective range. Also, since these classes are throttle body limited, anything in the airstream before the throttle body is undesirable. In stock or modified street vehicles, Mass Air systems do a great job. They just have no place in this type of racing in my opinion.

03-09-2014, 09:27 AM	#4
Ed Wright Veteran Member Join Date: Mar 2005 Location: Sand Springs, OK Posts: 8,132 Likes: 896 Liked 390 Times in 170 Posts	Re: EFI, Alpha-N vs Speed Density fueling Strategies I think MAF is a better deal. I work with GM's factory systems every day, and the MAF system is much more forgiving for weather, elevation and engine combo changes. Different manifolds, headers, collectors, going to Denver, seldom require any tuning changes. On many cars, (like mine) where would you put it? Going to put an air filter on it? The GM (don't know about Ford) sensors have heated wires. They glow red when running. They have to remain perfectly clean, or the calibration changes. Then you usually end up with elbows in the ducting to accommodate an air filter. You can't have dust, and who knows what else in Louisiana (Joke) cooked on those heated wires. Speed Density done correctly compensates pretty well. __________________ Ed Wright 4156 SS/JA Last edited by Ed Wright; 03-09-2014 at 09:29 AM. Reason: Still can't type...

03-09-2014, 12:25 PM	#5
ken robinson Member Join Date: Dec 2001 Location: tomsriver nj Posts: 479 Likes: 74 Liked 215 Times in 86 Posts	Re: EFI, Alpha-N vs Speed Density fueling Strategies For odd ball combos (2.3 ford turbo)that do you do for a cal map to start with if one is not available ? Or do most of the company like FAST have a start up cal map on file you just need to call when ordering the the ecu .

03-09-2014, 12:53 PM	#6
RacingRicki Sponsor Join Date: Sep 2005 Location: Colorado Posts: 106 Likes: 0 Liked 0 Times in 0 Posts	Re: EFI, Alpha-N vs Speed Density fueling Strategies David, You mentioned a racer that is running in speed density open loop. If it is open loop, how is it that the ECU is compensating for air changes? I thought open loop meant that there was no compensating going on. I run the "classic FAST" system in Alpha-N mode open loop. With that setup, closed loop would use the o2 sensor to correct the fuel. In open loop it doesn't. How is this different with speed density? Does speed density use the o2 sensor at all? Also, I was told that even though I run in open loop Alpha-N that there are tables that I can't see that are compensating for barometric changes much like a carburetor does naturally. Is this true? __________________ RacingRicki

03-10-2014, 01:59 PM	#7
pbp1 Junior Member Join Date: Mar 2013 Posts: 80 Likes: 12 Liked 27 Times in 6 Posts	Re: EFI, Alpha-N vs Speed Density fueling Strategies Ken, one of the beauties of Speed Density is that since it is really based on airflow, it is relatively easy to start with a basic VE table and run it in closed loop and tune it in based on the O2 correction that you see in your datalogs. There are a lot of baseline tuneups in our C-Com software to chose from and while none of them are specifically for a 4 cyll, it would be very simple to start with one of those and make a few changes to give you a close starting point. I would be glad to put a tune together for you, send me a message if you are interested in this. David Page FAST

03-11-2014, 07:59 AM	#8
SS3718 Member Join Date: Sep 2006 Posts: 129 Likes: 5 Liked 27 Times in 14 Posts	Re: EFI, Alpha-N vs Speed Density fueling Strategies David, I just wanted to say thanks for sharing and taking the time to post on this topic. As a current FAST customer, not only do you have a great product but the customer service that you provide is second to none and this post is yet another example of the service/tech support that your team provides. Thank you and see you at the track in 2014, Nick Morris SS 3718 GT/FA

03-11-2014, 08:26 AM	#9
Rich Biebel VIP Member Join Date: Jun 2007 Location: Northern New Jersey suburbs Posts: 2,314 Likes: 25 Liked 544 Times in 213 Posts	Re: EFI, Alpha-N vs Speed Density fueling Strategies How do you add a cam sync sensor to a GM LT-1 from the mid '90s ? I raced one and used bank to bank but my Accell Gen VII could run in sequential. I ran a crank trigger with a gutted optispark dist.and was not sure how to add a cam synch sensor. I struggled to tune my car on my own and really needed a pro's help and some dyno time.....running in sequential sounded like it would make more sense..... __________________ Rich Biebel S/C 1479 Stock 147R

03-11-2014, 09:01 AM	#10
Ed Wright Veteran Member Join Date: Mar 2005 Location: Sand Springs, OK Posts: 8,132 Likes: 896 Liked 390 Times in 170 Posts	Re: EFI, Alpha-N vs Speed Density fueling Strategies I used an Opti for a while. Not gutted. It can be done with the Opti electronics, although I nener tried it. Some of the Stocker guys are doing that. I now use an MSD dist with cam sync. I didn't find sequential to be the huge HP deal some make it out to be. Still, 5 to 7 hp is worth the effort. I had 2 cyls 9 & 10% lean, the rest were 2 & 3% off. __________________ Ed Wright 4156 SS/JA