Because of my lack of understanding, I thought a conversation regarding waste gated turbos might be beneficial.
I have a 177148 on a 4MG and love it. It has a wastegate that opens at 24lbs. of boost normally but up to 26lbs. when the ambient temperature is cold (below 0 F*).
Many have spoken of pinching the wastegate hose off in order to get more boost, with the idea that the more air the better. So my question is why would the manufacturers put a waste gate on if better performance and efficiency would be obtained without it.
My assumption is that the design of the turbo with a waste gate is to allow superior low end boost, quick spooling, and near peak performance at higher RPM's. The sacrifice being a slight loss of possible performance at say RPMs above 1700 or so. I also assume that something like higher exhaust drive pressure might negate the benefit of additional boost created by having the waste gate pinched off. Or, perhaps the design of the turbo would allow it to overspeed without a waste gate.
Thanks in advance for anyone that is willing to educate me!
I'm far from the best person here to educate on this but any turbo can be oversped and damaged or worse, damaging the engine with excessive egt. The wastegate is there on some to prevent this or at least prevent overspeeding the turbo because excessive egt is still possible.
There's also the subject of higher boost not necessarily being beneficial. I think the question becomes where does it cross the line from being beneficial to just excessive heat. Without a wastegate, you have to control that and decide when to back off and not overspeed the turbo or build boost that's not necessarily good but not necessarily overspeeding it either.
On the other side, often the wastegated turbos may be set a little too conservatively altho somewhat adjustable. This leads some to pinch off the hose in effect eliminating it. Often times this might be done by some not fully understanding what they're doing unfortunately because they are told it's a way to get past this limit not understanding they have to control it instead
I've tried to explain it the best I can in layman's terms everyone can understand. I'm sure others will be able to do a better job but that's the basic explanation.
Thanks 379, but I don't quite understand more input air producing higher EGT in and of itself. In other words, if I use X amount of fuel to obtain 24lbs. of boost with the waste gate opening, and the same amount of fuel would produce say 30 lbs. of boost with the line pinched off, where does the higher EGT come from? Perhaps because of higher intake temperatures and exhaust pressure?
Higher boost number relate to less efficiency of the compressor wheel when you get right down to it, less efficient means more heat out of the compressor discharge, so more work for the after cooler to do to reach the same inlet temp entering the head.
Wastegates really are the best of both worlds, it allows the turbo companies to use tighter/smaller exhaust housings to increase spool up speed and still allows the engine to breath as rpms rise but keeps the turbo in the optimum operating range.
I think to answer your question, the excess boost/pressure bypasses the turbine and is discharged directly into the exhaust. Think of the wastegate as a pressure relief valve.
I don't disagree with the principle of wastegates in general. I'd like to see them more easily/accurately adjustable with a range that while maybe not 100% optimal still within reason. Take the stage one for example. While being wastegated at say 30psi might be fine the majority of the time, another 5 or 6psi would definitely be better and still beneficial. How many people would be pinching that hose off, totally defeating the purpose, because of turbo companies being a little to conservative with them? I'm happy with the way this turbo performs but would not want it wastegated at 30psi no matter how much/often I go over it.
Wow. Is that what you got from that really?
If it were gated in the mid to upper 30s I wouldn't mind if it were. Just seems many of the gated turbos are done so a little too conservatively maybe leading too many people not fully understanding the consequences, too pinch off the hose cuz they're told it will give them more boost, more power, not even knowing there's a point where it becomes a bad thing more than good.
No where did I say it WAS gated. Good God.
Why do you think the wastegate settings are conservatively set, maybe it's because that is all that is needed to meet air flow requirements, any more is wasted energy.
Not every wastegate is set the same, the 177148 is set to meet the requirements of a 550hp engine, the 175963 is set tighter to meet the requirements of the 600hp engine.
The Garrett I mentioned is off of an engine rated at 665hp and set at 35psi, see a trend here?
I understand what you're saying but "all that's needed" by whose standards? And what does the gated 1.65 on the 175963 do for a 600 tuned C-15? Maybe it meets requirements for airflow but that doesn't make it the best choice performance wise or otherwise.
Don't get me wrong Cody, I like the concept. I would just like more user control because we all know whether it's turbo manufacturers or engine manufacturers, they don't always do what's best for the end user.
Truth be told, the 7923 stocker did quite well with just the 600 tune. I would've liked it better if I had an extra 3-5psi at my disposal that imo would've been useful energy under certain conditions for brief periods.
Varying conditions alone make such black and white blanket applications not necessarily the best for everyone or wasted energy if it were breached.
Just my opinion but why I prefer a non wastegated turbo where I can decide where that energy crosses the line from useful to wasted. I'm probably more conservative with this setup than others too.
Dave, you need to learn how-to read. You took what you wanted out of that post in an attempt to make it look like I don't know whether the turbo I have has a wastegate or not and not everyone has the same opinion or agrees for the sake of agreeing so feel free to rant but excuse me if I'm not moved or impressed. The same happened with the secret housing nonsense that you could damn near insert posts from 3 years ago in that one and pick up where it left off how many years later? If you don't know what I'm referring to Dave, now might be a good time to just sit back and listen til you're called upon? Are you for real? Maybe I don't agree with everything your hero says. Sorry if that's not allowed here.
I gotta go figure out what happened to my wastegate now.
Dave, you need to learn how-to read. You took what you wanted out of that post in an attempt to make it look like I don't know whether the turbo I have has a wastegate or not and not everyone has the same opinion or agrees for the sake of agreeing so feel free to rant but excuse me if I'm not moved or impressed. The same happened with the secret housing nonsense that you could damn near insert posts from 3 years ago in that one and pick up where it left off how many years later? If you don't know what I'm referring to Dave, now might be a good time to just sit back and listen til you're called upon? Are you for real? Maybe I don't agree with everything your hero says. Sorry if that's not allowed here.
I gotta go figure out what happened to my wastegate now.
I think your right, I need to learn "How-to-read" cause I have no idea what this mean's.
Are we gonna continue being off topic here, or move on ? :bang
I hauled a light load today (75,000 gross) and noticed in the hills that the boost pressure actually came off of the gate setting of 24 lbs. by 2 or 3 pounds once I got over 1800. The engine is governed to 2100, but the fuel must start tapering off well before then.
I usually don't run over 1800 unless in the mountains trying to get enough rpm to grab the next gear. It is a 15 speed.
When the races in my governor wore out it would fall on it's face at 1800. It had a higher speed spring in it but it may have well been worn out too. Replaced it all and used purple spring. Pulls hard all the way up now. Since going to 18spd not quite as big of a deal. I rarely ever twist it over 2000 but with the 15spd I had it really sucked to have it fall off so quick.
A wastegated turbo is more of middle ground to meet emissions mostly. They also help lower the RPMs of the powerband and can help increase low end torque. But, a properly tuned engine without one can still be very strong and run pretty clean.
To throw something else into the mix, I think my MBN pulled just as good, if not a bit better than the NXS ACERT I'm running now. The ACERT just smokes less. I like the ACERT, but really miss my MBN. Would've kept it, if not having to total the truck out after the pickup truck t-boned me back in Mar.
Having said that, you don't need higher boost numbers. Just air flow. Pressure is resistance to flow. If you can make the same power and burn clean at 30# of boost, vs an ACERT making over 40 at the same power level, it is bit of a waste. I don't have a perfect side-by-side comparison, as my "new" truck has 18spd/3.36 gears and my last one had 13spd/3.55. But, once up to speed, the ACERT pulls almost as good as mine did. Having the MBN making 180hp more than this one sucks! lol Sure I'll have the ECM fiddled with on this one, too.
Better fuel atomization is one of the bigger factors in EGT, emissions and smoke control to boot.
Acert engines make more boost with the IVA's active because the intake valve is being held open, engines with the IVA's disabled don't make nearly the intake pressure, also remember that the work is spread between two turbos.
The reason the 175963 comes that way is because it is meant for a 15.8L engine, there are no factory 600hp 14.6L engines for road trucks. Displacement has a huge influence on exhaust energy and turbine selection.
That is why guys with tuned C16s can run a Perkins turbo with the stock 1.65 exhaust housing it comes with but a 14.6l engine requires a drop to a 1.15 to get the same performance.
Stock C16 Dyno test data directly from CAT, manifold pressure is listed in in-hg, it figures out to just a little under 27psi. Shows what it takes to make 600hp.
You have no choice of any control with a non gated housing, except to change to a larger housing, which many people would benifit from. The guys running wastegates or even ones that have been tuned to allow a little more or little less boost are seeing better performance and drivability out of their engines and don't have to worry about over speeding their turbo and super heating their intake air with every little hill they come too.
And just so you know, when your engine runs well enough you can get more out of a wastegated turbo than just what the gate will allow, there is a 500hp C15 sitting in the driveway that will push 35psi on the gauge with the wastegate completely open.
I think I may have been getting a little more out of the 7923 towards the end. Hard to say since at the the time all I had to go by was the in dash messenger display that only reads 31.8 max no matter what. It would max out damn near instantly tho.
I agree with most of what you say. I'd even like to try a little bigger housing. I think the 1.58 would be too big tho and it wouldn't spool right and EGTs would be too high. I still think ADs 1.42 might be the ticket tho.
Then again, with the way it performs now, maybe it's as good as gets. I really have no complaints. Pretty sure Dave would agree. I do get that snorting if I let off too quickly under high boost like over 30psi. The 7923 did this too. Pretty easy to avoid tho.
Honestly, I don't think there's a better setup for a stock C-15 with the 600 tune. Least that I'm aware of which isn't much. I wish I had the time and resources to experiment more.
Well I've been gone a few weeks and it is amazing the new knowledge that is here when I get time to check back in , you guys are a priceless resource to all of us that work trucks and like to take good care of them but have to much going to know all the things you guys do . Now I bought the 1496-988-0001 with 1.58 non-gated housing for my 15.8 and haven't had time to put it on yet , after reading this I'm a little worried that I should have gone back with gated 1.65
Housings are cheap and if you find you don't like the 1.58 I have a new 1.65 I could trade you for, came on my 175963 and I took it off as soon as I got it home, never had smoke through it.
Thanks with what I read here sounds like I might need it , I almost bought booth housings at the time and don't know why I didn't , if you don't mind me asking what did you replace the 1.65 with and why , trying to learn as much as I can .
At the time I bought my turbo(2012) there were only two housing options, the 1.65 and 1.32, I bought a complete 175963 and bought a 1.32 off of a friend for $100.
I ran the 1.32 on my 3406B and didn't care for it, with my fueling and a worn out engine I would get to 17-1800rpm and it felt like it was just restricting the engine, never tried the 1.65 before I rebuilt the engine and then sometime during first startup something went through the turbine and junked the wheel.
I want to rebuild but have come to the realization that it just isn't that ideal of a turbo for the direction I'm heading, if I turn the engine down I will rebuild and use a 1.58.
Remember all this is on a 14.6l 3406B, your displacement will make a difference.
What would you want for the 1.65? And just cause I'm the curios type , I see you said you are running a turbo off of a 665 isx , what turbo is that and the specs
No I haven't got it on yet , it is attached to a 0001 , I would like to get it on and put a few miles on it to see what it dose , I do have a friend with a new 1.58 that bought it and never put it on that would let go of it , I would have bought it but I chose to go with a a complete unit
Thanks I can't wait , if I have any worries it's that I feel it spooled fast with the 1.65 , I don't push mine hard , even a little heavier than I should be and I have never had it on the floor and never felt the need to go over 30 on boost so I'm wondering if it will be big enough, but there's so much I don't know about this stuff I don't know what to expect
It's nice, can flat foot it at 1200rpm and it will start building boost and comes on hard, makes between 45-50psi running around bobtail and the engine doesn't ever seem like it peaks. EGTs seem to not get as hot as they did with the Holsets.
Crazy ! Is the gate set that high or have you worked on it ? So you went down in housing size to gain that bottom end ?
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