Jump to content

Sluggish at Hiighway speeds!!


Recommended Posts

I have fixed my boost leak, I think, but I am still experiencing a power problem. Truck is a STOCK 2003 S.O CR motor 250hp/47RE auto except for Airdog100 and homegrown CAI and a 5" exhaust. Truck has no get up and go especially at interstate speeds. When I press the accelerator at highway speeds it seems very slow to react, the truck will go faster but it is slow in getting there. I have checked my rail pressures last night while cruising at 65mph and they hovered right around 90mpa ( 13,000 psi if my math is correct). The truck idles at about 35-37mpa (5,000-5,350 psi) and at WOT it will hit 150mpa (21,750 psi). The outside air temp was 55° and my IAT temp was 70°. All of these numbers were taken with a diablo predator in the diagnostics area. (I am not running this programmer). There was also a reading for intake temp that read 150° and it never changed. I would really like to figure this out, I need that extra umph to pull my camper, and i swear all this started after i installed my airdog this past spring after the Holley blue electric one crapped out on me. I do not have EGT guages, or tran temp guages( YET). I do know that the truck is making about 22-23 pounds of boost with the turbo (HE341 I believe is the stocker). Diablo shows 15 psi at idle which i have to assume should be 0 and at WOT it will read 37-38 psi which should be about 22-23 pounds of boost by doing the math. The truck has 141,000 miles on it with 3.73 gears, it blows very little smoke and purrs like a kitten. The truck seems to run very well it just doesn't have the power I think it should especially on the interstate. I also plan on lashing the valves in the very near future!! Other information should be in my signature.

Any Ideas or thoughts on what the issue could be. I am sure i have forgotten some information but i can hopefully answer any further questions. One last thing the truck shows no codes with the key trick, the diablo or a code reader.

--- Update to the previous post...

Also the fuel filter was replaced not long ago as was the air filter. Fuel filter is a 2 micron filter and the air filter is an oem filter. Also are the boost numbers in range or are they short for that stock turbo??

Link to comment
Share on other sites

  • Moderator

Boost and rail pressure numbers are good. Your intake air temp at 150° is a little odd, that's probably the sensor on the air box. I am not sure how much the ECM uses that number for, so it may not even be an issue. With your homemade CAI did what did you do with the sensor from the airbox.Your homeade CAI seems to not be as cold as the stock setup. Stock should be about 10-12° above ambient, and you were +15°. What filters do you have on the AD? There is no true 2um filter, and the AD f/w sep is worse than stock, so just want to ensure your running as good of filter as you can. When you go WOT does the truck downshift? What's your 60-80 time?

  • Like 1
Link to comment
Share on other sites

I am not sure what my 60-80 time is. However if I'm cruising at 60mph and roll into the throttle most of the time it will not shift down. If i stab the throttle sometimes it will and sometimes it won't. It actually seems like the truck is always in the wrong gear especially when towing. Just when it seems it is pulling good it wants to change gears(torque management??). I was unaware that the AD f\w was crap, i will get that changed immediately. My fuel filter is a new Napa Gold 2um (so they say). The only thing i really did to the airbox was drill a hole in the bottom of it.I did notice a little while back when i looked at the diagnostics on the predator that the voltage to a sensor can't remember which one was really sporadic(might have been map sensor). I did an APPS reset and the voltage settled.Anyhow, I am open to suggestions and guidance. Thanks for your help!!

Link to comment
Share on other sites

Whats the diablo add in hp to a cr ? I found my truck pretty sluggish until I could hit over 30 psi meaning closer to 350 hp. Other thing is if your wastegate opens at 20psi will feel like you hit a brick wall .., you should be able to hit more so check that

Link to comment
Share on other sites

  • Moderator

Run a Baldwin BF1275 and a Donaldson P551315 on your AD, and nothing else (certainly not Wix/NAPA). A hole in the bottom of the stock box is good, add a 3" piece of PVC to pull cold air, not hot engine bay air. Click on the link in my sig, on the bottom of that page is a link to a Home Depot CAI. The WG is set for 22-24 on the stock HE341, and with only 250/460 the truck may be more sluggish than you are thinking it should be. You may also need a trans tuneup, which may help your issues.I highly suggest a Smarty Jr. If you set it on SW1 it will give you HO tuning plus a little. It should wake your truck up and give you a little bump in economy as well. The Smarty Jr will also allow you to run an adj boost elbow and set the WG to about 30-32 psi.

Link to comment
Share on other sites

Thanks for all responses!! I can offer a 65-85mph time(couldn't get slowed down to 60 on the highway). Okay so from 65-85 my time was 16 seconds (slow!!) when I stabbed the skinny the truck actually did down shift but it didn't stay there long (this truck loves overdrive). Like I said earlier just when it feels like it is really making some power it wants to shift (always at the worst time). Now on the way back home from the big city I kept the truck around 2200 rpms (75MPH) and that seems to be a sweet spot for it. I could roll on the throttle and it seemed to go on. As long as I keep it at 75 or so it does well. I may still have a boost leak somewhere I will re-check when time and life allow. I guess at 75 the turbo is pretty well spooled and doesn't take it long to get going.I will definitely be purchasing the new filters that AH64ID mentioned. As far as the Smarty Jr and boost elbow go that is what I would like to do also. As far as the boost elbow goes how do I adjust the wastegate to allow this extra boost with the smarty?And roger on the 3" pipe I have that exact pipe and mounting flange just have not had the time to install. The kids and their extra curricular activities demand most of my time!!

Link to comment
Share on other sites

  • Moderator

That does seem quite slow, but your boost means you have the fuel. So either it's an issue in the trans, part of the OEM tuning, or not abnormal. Is your speed re-calibrated? 3.73's should be 81 at 2,200 and 285's; 4.10's should be 73.

Link to comment
Share on other sites

No, my speed hasn't been re-calibrated. Maybe i need to get the gps in the truck and check it that way. I have no way of re-calibrating anyway. I am really at a loss as to what the problem could be it may just be the way it is. If i keep her cranked up she does pretty good, but pulling a 5th wheel at 75-80 mph is really not a very good idea. Also the difference in rpm's with overdrive on and off is amazing is there really that much gear reduction between the two? It will drop almost a grand. With overdrive off and 75mph i'm in the redline (i don't normally drive that way).I also noticed tonight that if I manually shift the gears; when I go from 1st to 2nd it seems like it doesn't grab 2nd right off the bat. its like it has been double clutched. does that make sense? One other thing this truck does that drives me nuts is this: driving along overdrive on, tranny and speed have not quite got up enough to go into overdrive, i put a little more pressure on the skinny to climb a grade and all of the sudden it hits overdrive!! Why does it do that? I gave it more skinny not less. Maybe its time to swap out the governor pressure switch and solenoid. Going nuts!!!Thanks for your help!!

Link to comment
Share on other sites

its almost sounding like someone really screwed up the shift points with a ecm flash of something? Presuming lets say the tranny is fine.Have you taken the intake off the turbo and spin the wheel to see if it isnt gummed up or out of play causing late spool up? sometimes it could be the simplist thing. anything obstrucing the exhaust or intake? tranny fluid topped off and not burnt out/overheating? (throwing darts at the wall) :banghead:

Link to comment
Share on other sites

  • Moderator

3rd gear is 1:1, 4th gear is 0.69:1, so depending on the speed there may be a 1,000 rpm drop if you shift at redline. If you shift at 2500 1-2 is a 1020 rpm drop, 2-3 is a 776 rpm drop, 3-4 is a 775 rpm drop (assuming a locked tq converter, which isn't the case so the rpm drop will be slightly lower). You don't want to run over 2900 rpms, the ECM starts to defuel at 2900.

Link to comment
Share on other sites

  • 2 weeks later...

Still have not performed the OD off timed runs as Johnfak suggested. However i did install/tune the predator performance tune (100hp-170tq) today and it really has made a big difference in the truck. It actually seems like it is making power when i am on the throttle. Was making 25lbs of boost and 23,200 psi at WOT. Is the program just telling the computer to dump more fuel? it is definately a different truck.

Link to comment
Share on other sites

×
×
  • Create New...