Interesting Observation About Afm

[VMax2007]

Ok, today was the first time towing my 3500# boat on hilly 2-lane country highway and I observed the following:

 

Let me begin by stating my truck info.

2007 NBS GMC Sierra SLT 4x4 Crewcab 6.0 with 3.73 gears and 20" wheels. (see sig).

 

I have been driving my new truck since mid-March, mostly all city and busy freeway driving. I do watch the DIC most of the time with it on the Instant MPG screen which also shows V4 or V8 mode. I have noticed that my truck with the 3.73's only goes into V4 mode during deceleration and on flat or downhill roads at constant speed. It is VERY difficult to keep it in V4 mode while maintaining speed. This has lead me to believe it is quite worthless with my type of driving (not much freeway).

 

Well, today was the 2nd time I have towed my boat with the first time being bringing it home from it's winter hibernation pole barn about 30 freeway miles away a month or so ago. Today's trip was about 20 miles of hilly 2-lane country highway and I used Tow/Haul mode. I found this VERY interesting. My truck actually uses V4 mode MORE while towing my 3500 lb boat than it does with no load at all. Tow/Haul mode rarely allows OD, especially on hilly terrain, so my RPMs were higher, therefore, more HP was available, which allowed V4 mode to actually stay activated even while maintaining speed on level highway WITH the boat!!! Sure, any uphill grade or moderate acceleration immediately kicked her back into V8 mode, but on level freeway I was actually able to keep it in V4 mode more than when empty. This confirms what I have heard about 4.10's using V4 mode more as well. I have come to this conclusion...If you do alot of freeway driving, get the 4.10's. You will get better mileage on the freeway with 4.10's vs 3.73 due to more time in V4 mode, assuming you don't live in the mountains or are constantly tromping on it. But in cruise control on fairly level highways. I don't do much freeway driving, so I am still glad I got the 3.73's as I am sure I get better city mileage than I would with 4.10's since neither use V4 mode much in city driving.

[ridnlow]

I was looking at the AFM in a Tahoe tune the to other day ( no stock nnbs trucks in the repository) but it looks as if you can change the rpm window of when you want it to come on.. I believe that once these trucks become more popular you will be able to tune the truck to switch to v4 mode more often and even hold it there longer.

[VMax2007]

I was looking at the AFM in a Tahoe tune the to other day ( no stock nnbs trucks in the repository) but it looks as if you can change the rpm window of when you want it to come on.. I believe that once these trucks become more popular you will be able to tune the truck to switch to v4 mode more often and even hold it there longer.

 

 

That would be cool!! I am still waiting to hear back from Jesse at Wait4Me and Charlie at Wheatleys. When I do, I will definitely ask about this. (They cannot yet tune the NBS GMs).

 

Thanks for the info!!

[ridnlow]

Have you checked with Charlie (Wheatley) lately?? I thought he was working on a NNBS the other day but was having problems with the TAC module not letting the throttle open fully when you go WOT until the 4 second delay is up... I guarantee he will be able to make the 6.0 run like hell when he gets done.. that truck has so much potential it isnt even funny..

[VMax2007]

Have you checked with Charlie (Wheatley) lately?? I thought he was working on a NNBS the other day but was having problems with the TAC module not letting the throttle open fully when you go WOT until the 4 second delay is up... I guarantee he will be able to make the 6.0 run like hell when he gets done.. that truck has so much potential it isnt even funny..

 

Nope, haven't heard from him yet, maybe this is why? Sounds like he is just getting started, I will let him get really good at it....Sounds like it shouldn't be too much longer now though...good news!!!

[ridnlow]

I wouldnt worry about letting him get good.. Basics are still the same since the ls1 in 98 hehe.. Only thing he would be new at would be the AFM.. Guy can flat out tune though.. Quick question.. Are you already running 93 in your truck??

[VMax2007]

I wouldnt worry about letting him get good.. Basics are still the same since the ls1 in 98 hehe.. Only thing he would be new at would be the AFM.. Guy can flat out tune though.. Quick question.. Are you already running 93 in your truck??

 

Nope, 87. And I plan to get a 87 tune, I don't want to have to run 91-93. I don't need a racetruck, I just want to maximize throttle response and make the 6.0 run like it should.

 

Any opinions would be welcomed. I am planning on getting ahold of Charlie again this week to see where he is at with the new software for NBS GMs.

 

I am considering both Charlie and Jesse at Wait4Me, any opinions there?

[ridnlow]

I hear ya about 87.. Ive got mine set up for 93 right now because Ive pretty much turned mine into a race truck heh but the beauty of having Hp Tuners is that I can change it back to 87 in about 30 seconds hehe. .I would go with Charlie hands down.. He does a good job and is very approachable, plus hes not near as busy as jessie so he can spend more time on your truck..

[svensk]

Well if a NBS sierra denali can pull a 14.8 in the 1/4 I would think a vortec max with 4.10 and a truck with less weight could do even better.

[s-ten]

Good observation. I had thought that 4.10's might be the better gear for a AFM truck on the highway, but I would have never guessed that the V4 mode would be on more often towing with 3.73 gears.

[C & A s Dad]

Jeff, since you are still waiting and trying to decide on a tune, I would suggest you get a good solid read on your MPG, then run about 2 tanks of 93 and then get another good read on your MPG. I have always used 10 fill ups to take an average. Don't check your MPG on the 93 until you have run at least 2 tanks. According to what I have read, it takes some time for your PCM to advance the timing with the 93 octane and you will not see any positive results until then.

 

I suggest this because, many people report better MPG with 93 over 87. I went all for 20+ years thinking the use of premium fuel was foolish until I finally tried it in my Yukon XL. It did make a difference and picked up about .5 MPG. I cannot prove it on a dyno, but I also strongly believe it helped my truck in towing my 6500lb camper, especially in the hills. You can search this and read many opinons on it both pro and con.

 

I will add this. I tried it on my 3.3L Dodge Carvan that I use for work and the 93 octane made absolutely no difference at all. However, it is likely about a 8.0:1 compression ration compared to a 9.5:1 (I think) in your truck.

[VMax2007]

Jeff, since you are still waiting and trying to decide on a tune, I would suggest you get a good solid read on your MPG, then run about 2 tanks of 93 and then get another good read on your MPG. I have always used 10 fill ups to take an average. Don't check your MPG on the 93 until you have run at least 2 tanks. According to what I have read, it takes some time for your PCM to advance the timing with the 93 octane and you will not see any positive results until then.

 

I suggest this because, many people report better MPG with 93 over 87. I went all for 20+ years thinking the use of premium fuel was foolish until I finally tried it in my Yukon XL. It did make a difference and picked up about .5 MPG. I cannot prove it on a dyno, but I also strongly believe it helped my truck in towing my 6500lb camper, especially in the hills. You can search this and read many opinons on it both pro and con.

 

I will add this. I tried it on my 3.3L Dodge Carvan that I use for work and the 93 octane made absolutely no difference at all. However, it is likely about a 8.0:1 compression ration compared to a 9.5:1 (I think) in your truck.

 

Thanks for the info. I will have to try it. How much better MPG would I need to offset the additional cost of 93 vs 87? I am not even sure of the price difference these days as I always use 87. I used to run mid-grade (89-90) in my 2000 Sierra 5.3, and when I switched to 87, I did not experience much (if any) drop in mileage.

[C & A s Dad]

At .5 MPG increase you will not offset the cost completely but it would come very close.

 

If 87 is 2.89 and 93 is 3.09 and you were getting 17MPG on 87 and 17.5 on 93. You would burn 23.53 gallons of 87 in a 400 mile trip and 22.86 gallons of 93 in the same 400 miles. The 23.53 gallons of 87 would cost you 68.00 and the 22.86 gallons of 93 would be 70.64. A difference of $2.64.

 

I run it for two reasons. The idea that it helps me when towing and I use only Chevron and their 93 contains a higher concentration of Techron than their 87 or 89. This is how I justify it in my mind and with my Dear Wife.