Gas vs PSD
Elder User
Joined: May 2010
Posts: 650
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From: WV
If I was racing a truck, it would be 2wd.
2wd >>>>> 4wd for rolling speed in a truck
4wd will get better take off but suffer after that. 4wd in 2wd still has to turn the transfer case and slows the truck down and get worse mpg. 2wd doesn't have as much rotational mass, will get far better 1/4 mile times, and better mpg.
2wd >>>>> 4wd for rolling speed in a truck
4wd will get better take off but suffer after that. 4wd in 2wd still has to turn the transfer case and slows the truck down and get worse mpg. 2wd doesn't have as much rotational mass, will get far better 1/4 mile times, and better mpg.
Elder User
Joined: May 2010
Posts: 650
Likes: 0
From: WV
If you have 4wd, that is probably the best way to launch. But that is probably because the owner wanted a 4wd fisrt and a drag truck 2nd. If it was an all out drag truck, 2wd is the better option. My 2wd trucks would have slaughter any of my 4wd trucks after take off. The few feet advantage you'll get from launching in 4wd, will be lost to the 2wd after a few hundred feet IMO.
Lead Driver
Joined: Jul 2007
Posts: 7,868
Likes: 9
From: Rhode Island
An EFI you're dealing with a fuel and spark table. Now make each one of those for every position of the VVT. Look at best option, will it blow the engine up? Test it, does it produce emissions legal exhaust? What is the knock sensor doing? Good? Now move up 100 RPM and repeat.
So let say each map takes 1 day as you say. Now lets say there are 20 positions on VVT (yes I know there are infinite, but let just break it down to 20 ranges). Let say you can eliminate 75% of those positions at any given RPM, so that takes you down to 5 VVT positions per a 100 RPM range. You will need to create a map fuel/spark map for each of those 5 ranges/positions. Find the best one and test it. Lets say that takes a day as you say to create each map. That could take up to 5 days for each VVT range. But lets give tuner, Dr. XXX, the benefit and say he can elinate 2 of those 5 and narrow it down to 3 test. he will still have to make sure it is emissions legal at that RPM.
So it took our tuner Dr. XXX 3 days, probably 4 days with emissions testing and tuning of the specific map. Now he gets to move to up 100 RPM with a new set of VVT positions and repeat until he reaches the redline... IF the RPM goes from 1000-5000, that a 4000 RPM range taking 40 positions to tune for. That would be 160 days... Then you get to go back tune the tranny, because all that is now controlled by the computer unlike your early EFI's.
Now you could just tinker with the timing of the VVT on a dyno for a few weeks and monitor the emissions, but that is what you are saying the "lesser" tuners do. So from your prospective that is not an option.
Have a map in a full map in a day, doubt it. You also can not just slap a stand alone unit on the engine like you used to because so many parts of the car/truck are run off of and in conjunction with the computer.
So let say each map takes 1 day as you say. Now lets say there are 20 positions on VVT (yes I know there are infinite, but let just break it down to 20 ranges). Let say you can eliminate 75% of those positions at any given RPM, so that takes you down to 5 VVT positions per a 100 RPM range. You will need to create a map fuel/spark map for each of those 5 ranges/positions. Find the best one and test it. Lets say that takes a day as you say to create each map. That could take up to 5 days for each VVT range. But lets give tuner, Dr. XXX, the benefit and say he can elinate 2 of those 5 and narrow it down to 3 test. he will still have to make sure it is emissions legal at that RPM.
So it took our tuner Dr. XXX 3 days, probably 4 days with emissions testing and tuning of the specific map. Now he gets to move to up 100 RPM with a new set of VVT positions and repeat until he reaches the redline... IF the RPM goes from 1000-5000, that a 4000 RPM range taking 40 positions to tune for. That would be 160 days... Then you get to go back tune the tranny, because all that is now controlled by the computer unlike your early EFI's.
Now you could just tinker with the timing of the VVT on a dyno for a few weeks and monitor the emissions, but that is what you are saying the "lesser" tuners do. So from your prospective that is not an option.
Have a map in a full map in a day, doubt it. You also can not just slap a stand alone unit on the engine like you used to because so many parts of the car/truck are run off of and in conjunction with the computer.
The rest of the sensors will basically act as multipliers. Effecting the entire fuel table.
Like this:
Its an XY chart of coolant temperature vs. injector pulse-width increase over stock values. So say at a coolant temperature of -40*C, it will move the entire fuel table injector pulse-width up 60%. Then you make another multiplier table for IAT, another for TPS, and so on. Same with the spark advance. You'll make a base table figuring in RPM, manifold pressure (or MAF) and initial spark advanced. Then that will have its own multiplier chart for the knock sensor. If X knock detected retard timing Y degrees.
The VVT table would be similar, you'd probably have a base RPM x Amount of timing advance/retard chart, and then stuff like TPS, ECT, would all be multipliers. The VVT advance/retard values could also be a multiplier itself for the fuel table.
What I'm trying to say is that it is not necessary to make fuel table for every single position and condition, because as far as I know, no modern EFI system works like that. They all have a base table, and then from there use simple to set up multiplier charts that effect the entire table as a whole.
EFI tuning is not nearly as hard as you make it seem. Any tuning shop worth its salt should have access to a load dyno, making mapping the engine even easier.
Thread Starter
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Modular motor junkie
Joined: May 2009
Posts: 6,190
Likes: 8
From: Texas
If you have 4wd, that is probably the best way to launch. But that is probably because the owner wanted a 4wd fisrt and a drag truck 2nd. If it was an all out drag truck, 2wd is the better option. My 2wd trucks would have slaughter any of my 4wd trucks after take off. The few feet advantage you'll get from launching in 4wd, will be lost to the 2wd after a few hundred feet IMO.
Elder User
Joined: May 2010
Posts: 650
Likes: 0
From: WV
Most of those will be 4x4's. Although if it didn't snow so much and our state plow trucks so lazy, I would have a 4x2 just because I really only use 4x4 a couple of times a year. And yet I pay for it every time I go to the pump.
Elder User
Joined: May 2010
Posts: 650
Likes: 0
From: WV
Its an XY chart of coolant temperature vs. injector pulse-width increase over stock values. So say at a coolant temperature of -40*C, it will move the entire fuel table injector pulse-width up 60%. Then you make another multiplier table for IAT, another for TPS, and so on. Same with the spark advance. You'll make a base table figuring in RPM, manifold pressure (or MAF) and initial spark advanced. Then that will have its own multiplier chart for the knock sensor. If X knock detected retard timing Y degrees.
The VVT table would be similar, you'd probably have a base RPM x Amount of timing advance/retard chart, and then stuff like TPS, ECT, would all be multipliers. The VVT advance/retard values could also be a multiplier itself for the fuel table.
What I'm trying to say is that it is not necessary to make fuel table for every single position and condition, because as far as I know, no modern EFI system works like that. They all have a base table, and then from there use simple to set up multiplier charts that effect the entire table as a whole.
EFI tuning is not nearly as hard as you make it seem. Any tuning shop worth its salt should have access to a load dyno, making mapping the engine even easier.
The VVT table would be similar, you'd probably have a base RPM x Amount of timing advance/retard chart, and then stuff like TPS, ECT, would all be multipliers. The VVT advance/retard values could also be a multiplier itself for the fuel table.
What I'm trying to say is that it is not necessary to make fuel table for every single position and condition, because as far as I know, no modern EFI system works like that. They all have a base table, and then from there use simple to set up multiplier charts that effect the entire table as a whole.
EFI tuning is not nearly as hard as you make it seem. Any tuning shop worth its salt should have access to a load dyno, making mapping the engine even easier.
Even with multipliers though, those numbers are not just randomly tested until it works. Lets say you have 20 multipliers (which is probably a very conservative number) you will have to adjust each multiplier at each of the 16 RPM ranges. So lets say the tuner finds the best point for multiplier 1, he then moves on to multiplier 2 and find the optimal point for 2. Guess what, there is a new optimal point 1 since 2 changed. He then he optimizes 1 which changes 2... it can take some time to optimize the pair. Now imagine doing 20 at once! You're telling me that can be done in a week?
My point is that the engineers at Ford, or where ever, can simulate the engine under each of these conditions, run a full range of every multiplier at every RPM range and determine the optimal position without ever touching a dyno. Sure they will take it to the dyno and maybe fine tune it, but they will have the numbers basically figured out long before the dyno.
the tuner on the other hand is trying to cram boost down the N/A engine is working in dark. They will have to use the trail and error method for each RPM range multiplier and hope they run it the optimal one. Even if they know every aspect of the engine, they still don't have the working CAD simulation to help predetermine the optimal multipliers.
The more multipliers the OEM's add, the problem becomes exponentially harder. At some point the OEM's will have to either run the CAD design's or release them to the tuners if anyone wants to do major modifications to their engine.
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Thread Starter
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Modular motor junkie
Joined: May 2009
Posts: 6,190
Likes: 8
From: Texas
With the hubs unlocked and the T case in 2wd, how much does it reall hurt MPGs?
Elder User
Joined: May 2010
Posts: 650
Likes: 0
From: WV
I should add my experience is based on 1/2 ton trucks. 1/2 tons are the only ones I've had the same engine, tranny, rear end, body configuration in both 2wd and 4wd.
Hotshot
Joined: Jun 2007
Posts: 10,008
Likes: 7
From: Austin, TX
2wd and 5 speed. It does decent. looked at my time slips last night and if i could get the truck to cut a 1.6 second 60' then it would run 13.4's, but the first 60' makes my E.T suffer.
Agreed, but if you saw how my truck launches you'd say 4wd would be much better... i could cut a 1.65 60' in a 4wd, not in this 2wd though.. it simply doesn't want to hook at all in 2nd gear which slows me down at the start of 3rd gear also being that i have to spool on the turbo...
a 4wd version of my truck would leave me in the dust for about the first 330ft... then i would start reeling in on it, but its hard to say whether i would actually catch up or not.. they both have good advantages, but if you can get a 2wd to hook up and pull a 1.6 ish 60' then you'd spank a 4wd all day long.
If I was racing a truck, it would be 2wd.
2wd >>>>> 4wd for rolling speed in a truck
4wd will get better take off but suffer after that. 4wd in 2wd still has to turn the transfer case and slows the truck down and get worse mpg. 2wd doesn't have as much rotational mass, will get far better 1/4 mile times, and better mpg.
2wd >>>>> 4wd for rolling speed in a truck
4wd will get better take off but suffer after that. 4wd in 2wd still has to turn the transfer case and slows the truck down and get worse mpg. 2wd doesn't have as much rotational mass, will get far better 1/4 mile times, and better mpg.
If you have 4wd, that is probably the best way to launch. But that is probably because the owner wanted a 4wd fisrt and a drag truck 2nd. If it was an all out drag truck, 2wd is the better option. My 2wd trucks would have slaughter any of my 4wd trucks after take off. The few feet advantage you'll get from launching in 4wd, will be lost to the 2wd after a few hundred feet IMO.
Elder User
Joined: May 2010
Posts: 650
Likes: 0
From: WV
Agreed, but if you saw how my truck launches you'd say 4wd would be much better... i could cut a 1.65 60' in a 4wd, not in this 2wd though.. it simply doesn't want to hook at all in 2nd gear which slows me down at the start of 3rd gear also being that i have to spool on the turbo...
a 4wd version of my truck would leave me in the dust for about the first 330ft... then i would start reeling in on it, but its hard to say whether i would actually catch up or not.. they both have good advantages, but if you can get a 2wd to hook up and pull a 1.6 ish 60' then you'd spank a 4wd all day long.
a 4wd version of my truck would leave me in the dust for about the first 330ft... then i would start reeling in on it, but its hard to say whether i would actually catch up or not.. they both have good advantages, but if you can get a 2wd to hook up and pull a 1.6 ish 60' then you'd spank a 4wd all day long.
Do you have an slicks for it?
Elder User
Joined: May 2010
Posts: 650
Likes: 0
From: WV
Cummins Puts a 3500-hp Engine In (Well, On) an Original Mini - Car and Driver Blog
V18 diesel with 12 turbos and about 5 ton-ft of torque and 3,500 hp, all in a Mini cooper
You can do anything with enough money.
V18 diesel with 12 turbos and about 5 ton-ft of torque and 3,500 hp, all in a Mini cooper
You can do anything with enough money.
FTE Leadership Emeritus
Joined: Jul 2002
Posts: 42,561
Likes: 423
From: Long Island USA
My short-bed, supercab, 4x4 will just about get the same (or better) MPGs as a DRW 4x2 F350 crew-cab longbed. The rear tubs, the height, and weight, make up the difference.
Elder User
Joined: May 2010
Posts: 650
Likes: 0
From: WV
It only hurts in MPGs when it comes to overall weight of the truck (city), and the height of the truck making it's aerodynamic drag higher (highway).
My short-bed, supercab, 4x4 will just about get the same (or better) MPGs as a DRW 4x2 F350 crew-cab longbed. The rear tubs, the height, and weight, make up the difference.
My short-bed, supercab, 4x4 will just about get the same (or better) MPGs as a DRW 4x2 F350 crew-cab longbed. The rear tubs, the height, and weight, make up the difference.
In your case, there is additional drive train mass by have DRW on your 4x2. Your also looking at least a 300lb difference because of cab differences.
I had an F150, long bed, supercab with the 5.4 and 4.10 rear end in both 4x4 and 4x2 (2 4x4's actually). The 4x2 consistently got just under 16 mpg while the 4x4's were just over 14 during the summer months (obviously they went down during the winter when I would use 4x4). That's a mix of city and highway with more city than highway.
The 4x4's where maybe 2" higher, probably more like 1" since all the trucks had the high payload package they all had beefed up front springs. The 4x4's weighed about 5% more (300 lbs on a 5,500 lbs truck), so yes that probably did affect mpg also, but I don't think it took down that much. I mean 2 people can weigh that much and you won't see that big of a drop in mpg with 2 people. But an extra 100lbs of drive train mass can drop your mpg really fast.
I will add, that additional weight and drivetrain will affect city mpg far more since your are accelerating the mass at a far greater rate. I found on long highway trips the difference to be less than 0.5 mpg, which could be do to many difference things other than the drivetrain.