robzombie4551
robzombie4551
You're a real funny guy! :rof:
Or are you serious?? :skep:
I'll tell you what,if you supply the motor and trans I'll do it. LOL
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Building for MPG?
- Thread starter Crankme69
- Start date
You're a real funny guy! :rof:
Or are you serious?? :skep:
I'll tell you what,if you supply the motor and trans I'll do it. LOL
Matt Bachand
Depends on the 6.5
If you are going to make blanket statements about 4.10 gears and RPM range, please include tire-size also, or else it has no value.
2200 RPM seems peak torque I agree, but its more like 65mph since I upsized to 235/85r16's. Seems like the engine works least, to run strong and smooth.
Passenger side exhaust still has to go through the turbo restriction and the driver'side wouldn't. Fuel would have to be tuned different for the 2 cylinder banks to make equal power. Unequal output makes stress on the block and crank.
DieselSlug
Well-Known Member
Im at the point of eliminating my restrictive GM-4. I usually get in between 14-17 MPG's with my truck. Not bad, but i want to try and get better. Hopefully the Holset will cure a MPG or two!
robzombie4551
robzombie4551
I see where your coming from, but the difference woud be minimal,as the exh. pressure from only one bank would be less restrictive,meaning less pressure.
Has this been done and proven not to work? If so I will just go ahead and make a total custom exh. manifold system with a different turbo.
I believe from everything I've read and heard, that the biggest design flaw for power and efficiency is the turbo and the poor manifold design.
There are already pulse inequalities built into the GM design. Maybe that's part of the crank breakage problem. I'm a fabricator and mech. not an engineer.
I just want to experiment and hopefully not blow it up, I can see where there might be some merit to higher cyl. pressures from one side to the other if the turbo was still a major restriction on one bank of exh. at the rpms that I would be diverting the driver side exh. away from the turbo.
Let me know if what you say is theory or proven science so I don't waste my time. If it has been done already and there is a thread i can read please direct me to it.
If you are going to make blanket statements about 4.10 gears and RPM range, please include tire-size also, or else it has no value.
2200 RPM seems peak torque I agree, but its more like 65mph since I upsized to 235/85r16's. Seems like the engine works least, to run strong and smooth.
I forget the many tire size options and effects on gearing. My comments apply when equipped with 265/75-R16 - your MPH may vary.
On a Dodge Cummins 12 valve the waste gate only dumps from 3 cyls. The manifold is divided,and so is the turbo,and the waste gate is on the rear half. Also on the 6.5 with a waste gate on the crossover pipe wouldn't some exhaust also come from the drivers side? The exhaust is going to take the easiest way out . I think it will work.
robzombie4551
robzombie4551
I have been told that also by someone that I floated this idea by, but was looking for more input as it helps all around.
540s10
New Member
if the crossover is still intact, pressure would equalize between the two banks, exhaust would follow the path of least resistance, meaning part of the pass side would flow back towards the cutout.
robzombie4551
robzombie4551
Yes the crossover would still be intact, the exhaust cutout would be mounted in the crossover and plumbed into the main exh. pipe at the end of the D/P.
bison
Well-Known Member
Ofcourse i'm serious,for sheer fuel economy a 4 cyl will beat a 8 cyl,couple that to an heavy flywheel to sustain the torque and you are in business,just don't expect an 8 sec 0 to 50 take of.
I used to have an Opel record and had planted a 60 hp NA P4 perkins in it ,top speed was only 120 km/hr cause it had only max 2400 rpm but it did surprisingly well.i cant remember milage but it ran pretty cheap.
I drove it for years.
buddy
Active Member
I have always believed the best gains in power or economy is through airflow, in and out. Out/exhaust being a bigger contributor to being able to run more power at lower RPMs, being able to run higher RPMs, and just being more efficient. So improving on the exhaust manifolds and the resitriction of the turbo would be wise.
Also plays into why I believe a better camshaft for these engines would help a lot, giving longer exhaust duration and more valve lift.
If set on keeping things simple and stock like, the extrude honing process on the exhaust manifolds can produce great gains and a porting or honing job on the heads. Unfortunately the extrude honing is expensive. A custom equal length header setup would be ideal, but also expensive and more complicated.
the reason turbos hurt unloaded efficiency is that they are a restriction and parasitic. It takes backpressure to spool them, which means the pistons have to work against the backpressure in the exhaust stroke. when loaded they can help improve efficiency and loads more power though, because they also recover some wasted heat energy. So they use some energy and recover other energy, which hurts when you dont need that extra power.
The ATT can certainly give better economy when unloaded if your GM turbo was being more of a restriction. The vacuum setup usually dumped a lot of boost early and when cruising so it was still pretty efficient. when people put on mechanical wastegate actuators they sometimes failed to realize that more boost when cruising was eating some of their efficiency. Other people realized possible gains from a bit more boost. There is a fine line of where it becomes more work to spool it than it is benefit, which has to do with RPM range and vehicle weight. The ATT gives you no adjustment ability so people tend to have less boost at cruise with it, which will result in less restriction, plus the housing is much larger which allows it to flow. It is better when loaded for sure.
Like has been said, I also believe it has to do with what RPM you are sitting at, so gearing and tire size play a big role. Driving at 2000rpm may sometimes be more efficient than driving 1700rpm if it takes more fuel to maintain lower RPM because it produces less torque, like when climbing in elevation in OD or slightly loaded. But in general keeping it lower is better of course. Just a bit of info if looking at fuel rates, like 20mm3, that is based on each injection event. At lower RPM there are less injection events per minute, so 20mm3 at 1800rpm is less fuel consumption than 20mm3 at 2200rpm. Just like at idle 600rpm idle at 8mm3 is half the fuel use than 1200rpm at 8mm3. Another large factor is engine temp, keeping it around 200F will be more efficient than down around 180F, so those stock engines going to 230F always got better mpg. Fuel Temperature can play a role, since warmer fuel atomizes and combusts much better.
The NA 6.2 diesels would be a good choice, because those intake and exhaust manifolds are not so bad and they are decent power and economy. With a DS4 instead of a DB2 it may be more efficient and powerful as well, being able to control timing much better and more easily control fuel rate. Some NA 6.5s came out with DS4s but had 4L60E trannys.
Also plays into why I believe a better camshaft for these engines would help a lot, giving longer exhaust duration and more valve lift.
If set on keeping things simple and stock like, the extrude honing process on the exhaust manifolds can produce great gains and a porting or honing job on the heads. Unfortunately the extrude honing is expensive. A custom equal length header setup would be ideal, but also expensive and more complicated.
the reason turbos hurt unloaded efficiency is that they are a restriction and parasitic. It takes backpressure to spool them, which means the pistons have to work against the backpressure in the exhaust stroke. when loaded they can help improve efficiency and loads more power though, because they also recover some wasted heat energy. So they use some energy and recover other energy, which hurts when you dont need that extra power.
The ATT can certainly give better economy when unloaded if your GM turbo was being more of a restriction. The vacuum setup usually dumped a lot of boost early and when cruising so it was still pretty efficient. when people put on mechanical wastegate actuators they sometimes failed to realize that more boost when cruising was eating some of their efficiency. Other people realized possible gains from a bit more boost. There is a fine line of where it becomes more work to spool it than it is benefit, which has to do with RPM range and vehicle weight. The ATT gives you no adjustment ability so people tend to have less boost at cruise with it, which will result in less restriction, plus the housing is much larger which allows it to flow. It is better when loaded for sure.
Like has been said, I also believe it has to do with what RPM you are sitting at, so gearing and tire size play a big role. Driving at 2000rpm may sometimes be more efficient than driving 1700rpm if it takes more fuel to maintain lower RPM because it produces less torque, like when climbing in elevation in OD or slightly loaded. But in general keeping it lower is better of course. Just a bit of info if looking at fuel rates, like 20mm3, that is based on each injection event. At lower RPM there are less injection events per minute, so 20mm3 at 1800rpm is less fuel consumption than 20mm3 at 2200rpm. Just like at idle 600rpm idle at 8mm3 is half the fuel use than 1200rpm at 8mm3. Another large factor is engine temp, keeping it around 200F will be more efficient than down around 180F, so those stock engines going to 230F always got better mpg. Fuel Temperature can play a role, since warmer fuel atomizes and combusts much better.
The NA 6.2 diesels would be a good choice, because those intake and exhaust manifolds are not so bad and they are decent power and economy. With a DS4 instead of a DB2 it may be more efficient and powerful as well, being able to control timing much better and more easily control fuel rate. Some NA 6.5s came out with DS4s but had 4L60E trannys.
buddy
Active Member
If the drivers side and passenger side are connected then pressure should equalize between them, so there should be no difference, unless when the gate opened for the drivers side it blocked off the passenger side, but I don't believe thats the intent. It sounded a little like that though when saying it would take one bank out of the equation, which would be am imbalance.
A wastegate in the crossover should work like a wastegate in the turbo, only it may be a little better since it can be 2.5" rather than the small one in the turbo.