GEN 2 Flat spot during acceleration.. ANY IDEAS??

[19RaptorPB]

It would help because I could compare it to my footage to see if you indeed have a power loss. That said, the Ridge Grapplers are nearly 10lbs per tire heavier than the KO2s, which being unsprung weight significantly slows down the truck. I noticed a difference with my new tires only being up 2lbs each corner. I doubt it is the main issue here, but probably a contributing one.

I'm with smurf - unless you are running sport mode, 4A, t/c 'off', I'm inclined to think you aren't getting traction and the computer is compensating (something you've picked up on as well). Run a few times in that mode, then also try manual shifting and see what happens.

Your truck has a lot of torque and a very light back end. Those tires should help, but 36 psi is too high. You will definitely break loose in the back a lot more than you think. I have a supercab, but with both sets of tires running at 34psi in the back I was able to break them loose going straight.

It could also be, like dil mentioned, that your particular timing doesn't mesh well with the turbo lag and transmission shifting. Most of the delay I've noticed in my truck is the transmission having to drop 2-3 gears, which is generally in the RPM range you note as being problematic.

I appreciate your knowledge for sure. I realize that my tires are heavier but my VR 601’s are lighter which in the end is a wash. I am also looking for the correct tire pressure run, what would you suggest? Keep in mind I am running 20’s so my profile is slightly less. That being said, don’t think I’m driving a street queen because of the 20’s... this truck has already spent plenty of time off-road and will continue to do so. I really don’t think it’s the T/C but I will pay attention to it next time. I’ve tried in manual mode as well with no changes. When speaking of my particular timing meshing well with my transmission, what do you mean exactly? I’m pretty old school when it comes to timing and short of turning a distributor with a timing light in my hand and checking vacuum advance... I’m thinking that’s all handled via tuning now correct? I’ll try to get a video posted today so you can compare. Thanks again for the help.


Sent from my iPhone using Tapatalk Pro

 

[rtmozingo]

I appreciate your knowledge for sure. I realize that my tires are heavier but my VR 601’s are lighter which in the end is a wash. I am also looking for the correct tire pressure run, what would you suggest? Keep in mind I am running 20’s so my profile is slightly less. That being said, don’t think I’m driving a street queen because of the 20’s... this truck has already spent plenty of time off-road and will continue to do so. I really don’t think it’s the T/C but I will pay attention to it next time. I’ve tried in manual mode as well with no changes. When speaking of my particular timing meshing well with my transmission, what do you mean exactly? I’m pretty old school when it comes to timing and short of turning a distributor with a timing light in my hand and checking vacuum advance... I’m thinking that’s all handled via tuning now correct? I’ll try to get a video posted today so you can compare. Thanks again for the help.


Sent from my iPhone using Tapatalk Pro

Well, I'm running 30psi in the back with my new tires, and I still think I'm getting slightly overinflated wear. The supercrews have more weight, so I can't say for sure, but my coworker running 36psi has overinflated wear on his rear tires. Assuming you are running unloaded, I would say 34psi would be a good starting point. Raptor Assault runs their trucks at 32f/28r. Of course, the reason the placard says 38psi is for fully loaded weight and ideal fuel economy, so you'll have to increase your psi as you increase your load. This is stock rims, so I don't know how much the new wheels will affect your truck.

When you get on it, the transmission will drop gears, usually two or three gears. It isn't slow, but it isn't supercar fast, and 3 gear changes is a lot when you are waiting for the power to hit. It feels like a dead zone - you are in the power band but nothing happens for what feels like a second. Kind of a combined hit from turbo lag and gear change, so it seems in my truck at least.

Doing a brake-boosted launch in 4A would probably be the best way to determine if this is what is happening, since that will eliminate both of those factors. If you've still got a dead zone, it is either lack of traction or you've got some kind of problem.

 

[jabroni619]

My 18 has that same little dead spot. I actually notice it a lot more during light acceleration. Its absolutely not related to octane, or tire slipping since even under very light load it's there. About a year ago I read another thread commenting on this and virtually all the replies were "me too" i'm surprised that a year later no one seems to have this issue. In normal mode it's really noticeable from the 1-3 shift and less noticeable from 3-5. After that I don't notice it at all.

In that old thread there were even suggestions that perhaps a tune could program that dead spot out of it with other people that had tunes commenting back that it's still there with a tune (at least the ones available at the time)

 

[Irish1964]

a MPT tune will take care of everything. I run 91px it's amazing the difference.

 

[19RaptorPB]

My 18 has that same little dead spot. I actually notice it a lot more during light acceleration. Its absolutely not related to octane, or tire slipping since even under very light load it's there. About a year ago I read another thread commenting on this and virtually all the replies were "me too" i'm surprised that a year later no one seems to have this issue. In normal mode it's really noticeable from the 1-3 shift and less noticeable from 3-5. After that I don't notice it at all.

In that old thread there were even suggestions that perhaps a tune could program that dead spot out of it with other people that had tunes commenting back that it's still there with a tune (at least the ones available at the time)

Well at least I know I’m not crazy. I know I’m not losing traction although it’s not a bad suggestion. I’m not really looking to do any tuning and won’t get into the debate about warranties etc... I’ve had plenty of tuned and non-tuned vehicles. This one has a 120,000/10yr bumper to bumper that I would hate to lose. I’m a maintenance geek and take very good care of my vehicles, I know a tune wouldn’t necessarily be the cause for a dead motor and I may re-visit after 10-20k miles. I’m more concerned with what the issue actually is instead of covering it with tuning. Is it timing? Is it a coil? Is it an injector? Sensor? I have to figure out what it is before I make a decision on whether to tune or not. I know damn well that Joe Schmoe at the ford dealer isn’t going to give a shit enough to actually find it especially since it isn’t throwing any codes.


Sent from my iPhone using Tapatalk Pro

 

[rtmozingo]

I actually notice it a lot more during light acceleration. Its absolutely not related to octane, or tire slipping since even under very light load it's there. About a year ago I read another thread commenting on this and virtually all the replies were "me too" i'm surprised that a year later no one seems to have this issue. In normal mode it's really noticeable from the 1-3 shift and less noticeable from 3-5. After that I don't notice it at all.

Then it is downshifting and turbo lag (more accurately, being below the boost threshold). At light loads, the truck is aiming for max fuel efficiency, especially in normal mode. Therefore, if you step on it, it will drop gears and begin building boost. The turbos put out power quickly, but only if exhaust is flowing through them, which a good deal of the time is not the case when cruising. So, you'll have a short time where your turbos are spooling up, compounding with the transmission having to drop gears. Both of these take time.

Tunes may help with the transmission shifting (I've seen mild improvements at best), but the delay from the turbos will always be there. It is still better than the 6.2 in how quick you get the power, but physics is physics.

 

[jabroni619]

Then it is downshifting and turbo lag (more accurately, being below the boost threshold). At light loads, the truck is aiming for max fuel efficiency, especially in normal mode. Therefore, if you step on it, it will drop gears and begin building boost. The turbos put out power quickly, but only if exhaust is flowing through them, which a good deal of the time is not the case when cruising. So, you'll have a short time where your turbos are spooling up, compounding with the transmission having to drop gears. Both of these take time.

Tunes may help with the transmission shifting (I've seen mild improvements at best), but the delay from the turbos will always be there. It is still better than the 6.2 in how quick you get the power, but physics is physics.

It's not downshifting, and it's not when stepping on it. I can accelerate smoothly and slowly from a complete stop and the lag is there after the UP shift from 1-3 and then again, but less prevalent from 3-5. I'm not talking about the delay from when you punch it to the time it takes for a downshift and getting thrown back in your seat. This is completely different, it's literally a loss of power. It could be turbo lag, but i'm not entirely convinced. It hasn't bothered me enough to check my actual boost pressure when it happens.

 

[19RaptorPB]

It's not downshifting, and it's not when stepping on it. I can accelerate smoothly and slowly from a complete stop and the lag is there after the UP shift from 1-3 and then again, but less prevalent from 3-5. I'm not talking about the delay from when you punch it to the time it takes for a downshift and getting thrown back in your seat. This is completely different, it's literally a loss of power. It could be turbo lag, but i'm not entirely convinced. It hasn't bothered me enough to check my actual boost pressure when it happens.

I appreciate the help from everyone but I’m convinced the entire first post is ever read fully. I wrote that it does it in all situations including going easy. It is not the transmission at all because it’ll do it in manual mode too. That was the first thing I checked. It isn’t downshifting, it’s not a loss of traction and it’s not only when my foot is to the floor. Those would all be very obvious if they were occurring.


Sent from my iPhone using Tapatalk Pro

 

[rtmozingo]

It's not downshifting, and it's not when stepping on it. I can accelerate smoothly and slowly from a complete stop and the lag is there after the UP shift from 1-3 and then again, but less prevalent from 3-5. I'm not talking about the delay from when you punch it to the time it takes for a downshift and getting thrown back in your seat. This is completely different, it's literally a loss of power. It could be turbo lag, but i'm not entirely convinced. It hasn't bothered me enough to check my actual boost pressure when it happens.

Well, the whole point of upshifting is to drop RPMs. So yeah, in normal mode the truck will upshift as soon as possible to keep you OUT of the power band to save fuel. Therefore your power will drop as the truck upshifts. I don't have the HP and torque graphs handy, but a drop from 3k RPM to 1.5k will noticeably drop your power.

The main culprit I think yall are dealing with is boost pressure vs boost threshold. If you stab the throttle after running at low RPMs, you'll be under the boost threshold since the truck will downshift, causing RPMs to jump. You'll wait while the turbos spool up and build enough pressure to cross the threshold line, referred to by most as turbo lag (for our discussion, good enough, in reality our trucks have very little turbo lag, since as soon as they spool you are getting power).

This is the worst case scenario, as the truck is shifting and having to build boost at the same time. It feels as if you didn't press the pedal at all.

In more mild situations, you aren't producing much (if any) boost to begin with, so any time your engine needs it you must wait for the boost to build. The bigger the demand for power the higher the engine revs, which further increases the required boost, ultimately increasing the time you are waiting for the power to hit.

Driving modes, current conditions, and driver input make a large difference on how the truck responds. I've noticed this behavior in my truck, but it is only due to limitations of the design and programming of the truck. I'm not saying there isn't something wrong with your truck, but that would indicate the programming is not working as intended, which seems pretty unlikely.

I run Harry's lap timer with OBD data feed so I can see exactly how much power I'm making at any given point, as well as boost and throttle inputs. I have a very good feel for my truck, how it responds and what it does in various situations, but I'm still surprised time from time exactly what the data looks like after the fact. The only mode to use true anti-lag is Baja mode, and even then there are times when my boost pressure drops off. Hence why I think a video would be helpful - knowing exactly where you stand in the power band and boost band will shed a lot of insight into what is actually going on.

 

[jabroni619]

I know what up shifting is supposed to do. This isn’t my first car nor my first turbo car. It shifts up, RPMs drop (normal) then start to rise again (again normal) and a split second later the loss of power (which feels like a timing pull) happens causing the RPM to drop. NO shifting, and NO loss of traction is occurring during this period.