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boost numbers after new turbo

3K views 24 replies 8 participants last post by  94slowbra 
#1 ·
Should I have the same boost numbers while cruising after the install of a MTW stage 1? Reason I ask is I'm having a few symptoms of a boost leak and I have noticed now that my boost while cruising 70mph has dropped about 2-3lbs. Only additions have been the turbo and 175cc injectors. Is the turbo that more efficient or is it bleeding off somewhere? If it leaking I can't tell where. I'll have to do some more searching.
 
#2 ·
get a tuner to close the vanes slightly. it should cruise around 5-6 but normally stock turbos will sit between 8-10 at 70 so maybe you do have a leak
 
#3 ·
I'm running Matt's srl and my stock turbo did run about 8-9 @ 70 and the stage one is at 6-7 @ 70. My other issue is my gets have increased slightly, from about 760-780 to 830-850. That's what originally caught my attention. My peak boost is the same, 26 but my gets rise much fast and go much higher. Maybe it just come with the territory, maybe I have an issue
 
#4 ·
Not to sound like a jackass but did you get the tune written for the stage one and 175's? Or your stock setup?


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#6 ·
Matt said the srl file should be fine for the new additions. My 175s have stock nozzles, he said he shouldn't need to change for stock nozzle. Also after talking with Adrian he said there should need to be any tuning adjustments for a stage one. Just to verify the tune wasn't the culprit I had tony write me a file for the 175s and the stage one. I'm having roughly the same results. Obviously the driving characteristics of the two tunes are different but have the same get issue.
 
#5 ·
egts sound about right to me atleast. maybe they can open the vanes up. i know thats backwards from what i just said but reading your last post it should be around 5 or so which with opening the vanes a tad you will get that and it turn it will lower the egts slightly if at all. the powermax which has no power compairison to the stage one but when swaped from the stock turbo will have slightly higher egts as well
 
#7 ·
Matt is wrong. A stage1 is not a stock turbo and requires tuning to get the most out of it as you can clearly see. The vgt vanes need to be closed slightly and open up slower.
 
#9 ·
I will ask him about this. Also the be fair I'm having the same issue with the tune from tony that I had written for the stage one and injectors.
 
#8 ·
What you have going on is a common problem and is likely the tune. Same thing happens to me when I go up in turbo size. Say from stage 3 to stage 4, my boost a cruise 70mph would go down do to the flow of the turbo being much more. I believe you have the stage 1 with the billet wheel which is a whole different turbo from the cast wheel one. Either way check all your sensors and then leaks if none found you will have to get the tune adjusted. The reason the egt's are slightly higher is because you are not building enough boost at 70 mph to get the air in the engine. Ideal boost is 5-6 psi of boost at 70 mph which you should be at about 2000 rpm. Common problems is the hose from manifold to MAP sensor, the other is the y pipe not seated. Keep me updated and remember that the ecm will need to learn where and when it needs to adjust the duty cycle. Putting a turbo on with more flow isn't slap it on and go on the 6.0, ecm has a lot of input so needs to learn.
 
#10 · (Edited)
I will forward this to matt. My cruising boost at 70 prior to turbo and injectors was 8-9 and egts around 760-780. Boost is now Lowe, 6-7 and egts around 830-850. This is all at around 1800 rpm, I have 37" tires and 3.73 gears. This could be why I need more boost, not enough gear. Thanks Adrian, I'll keep you posted
 
#11 ·
yea 37's will make it more difficult as you have now lowered the rpm range and everything is working harder to push the tires. i honestly think that even changing the tune up wont help with 37's. you would have to close the vanes up to much to get the desired boost which in turn will prob take the egts up a notch which isnt what you want. now as far as overall egts they should be down at WOT with the new turbo
 
#12 ·
That's the other problem they are higher at wot and they climb much quicker. But the 37s have been on the truck for years and I haven't had these issues prior. I'll get with matt with what Adrian said and see if he can help with the new info
 
#13 ·
You are close to my build, but we have different results. With 34" tires I get 600*ish at 70mph and 5-6psi boost with a stock or medium perf tune in OD. The boost is just a bit higher with the extreme tunes and fuel consumption is up. What do you get with it in 5th gear at 65mph? Maybe you have to re-gear it?

As background info: No, I haven't had my tunes adjusted for the 186/75s yet. Yes, the extreme tunes need a bit of fuel pulled low-mid pedal and unlike what PGreenSVT said, my vanes work about right for the boost I am making. I can easily get 30+. Maybe I would need the slower opening once a bit of fuel is pulled.
 
#14 ·
I'm going to see about having some fuel pulled. Ran the 8k tow tune yesterday only pulling about 4k but I could barley get to 950 egts and was seeing 26lbs of boost. So I'm guessing I dont have a boost leak.
 
#15 · (Edited)
ok , matt switched my tune to a vxcf4 strategy and it has brought back some of my boost. he said he did this so there would be an actual back pressure reading. my 70 mph boost is now back up to about 9 psi, egts range from 870-920. still too high in my opinion.
tried putting the truck in tow/haul to bring the rpms up but at my speed it shifting into o/d. maybe gears are the answer? its an obvious mechanical advantage, so everything else wouldnt have to work as hard, therefore lowering egts what is a stock tire size trucks rpm at 70? im only at 1800 @ 70 and 1700 @ 65.
 
#17 ·
Yes there is a relearn when switching tunes
 
#18 ·
i get that but is there a time or mileage threshold? i dont want to make tweaks after 30 miles of driving if it takes 200, see what im getting at?
 
#19 ·
Every truck is different but I have been told give it a couple hundred miles and a bunch of drive cycles. That is what works best for my truck too. The VGT relearn takes some time as does the tranny

Todd
 
#21 ·
Well I've had the vxcf4 in for about 120 miles so far. I'll leave it like that for a couple hundred more before I change anything. Hopefully your right. This is driving me nuts
 
#23 ·
3.73s. A probably not ideal but the problem wasn't there before. I'll drive it for a while and see
 
#24 ·
Your boost at 70 is right where it should be, and to answer the RPM at cruise I can go by what I had, with 37 and 3:73 gears I was running at 1750, It helped a little when I changed to 35" tires, but can't remember but I believe it was at 1800 even, since not long after that I went to 4:10 gears. Now 70mph I'm at 2000-2025 which is where I want to be and just about where a stock truck runs. As far as relearning all the members are right, depends on the truck and have seen as long as a tank full to two tank to get the learning down. EGT? well if I remember right you switched injectors and are now running bigger injectors which will raise your EGTs. I would have all your injectors checked just to make sure they are working right, I have seen some injectors that will stick open at cruise cause the problems you are have. By sticking open I don't mean wide open just a little. Sorry haven't been on this thread to help been very busy and have family visiting, you could call me and will try to help out. Thanks
 
#25 ·
thats what o thought, my boost has been the same for years, dont think thats the issue. yes i did switch injectors, renegade 175 stock nozzle, at the same time as turbo. right now i have gone through about a tank and a half. my wot egts have come down some, have seen 1300 so far on this tank. so i guess thats a good sign, hopefully it continues to come down. boost is staying the same, max of about 28. how do you go about checking injectors, flow test i assume? truck feels strong and smooth, but i guess if its small then i wouldnt notice. no worries about being busy, completely understand. if i need something in particular i give you a shout, hopefully things work themselves out
 
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