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N/A Diesel Exhaust Theory

Discussion in '6.9L IH & 7.3L IDI Diesels' started by Enginerd, Sep 20, 2019.

  1. IDIBRONCO

    IDIBRONCO IDIBRONCO

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    You're welcome. The reason that most people are disappointed is that they confuse an opened up engine with one that is force fed. Yes, headers like this do give you an increase in power. It's not as larger as what you get from a turbo, but that's because headers let the air flow through (out of) the engine better while a turbo will force more air to move through the engine. I rarely tow heavy and if it wasn't for me liking to ride ATVs in Colorado at high altitudes, I most likely would stick with the headers. I just don't need more than that very often. When I was visiting Thewespaul last January, he set the timing on my truck. He wanted to follow me on a test drive after that. He said that it looked like my truck ran pretty good for being N/A. I say that if you want to experiment (like Wes does) then go for it. Just be sure to let us know your results. Just remember that this is your truck and do what you want with it.
     
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  2. Macrobb

    Macrobb Full Access Member

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    No, not even close. You are limited by the amount of oxygen you can get into the cylinder. Like I said, a worn motor might make 85. New, 125 - 47% increase. A turbo and minor tuning? 200HP or 135% increase over a worn motor(These numbers are wheel HP, or the actual amount of power you put to the ground).
    And that's with a 'mild' turbo setup - single, off the shelf turbo kit, like a wastegated Banks or ATS 093/Factory Turbo, stock IP, no intercooler, no headstuds.
    Add a bit more expensive setup - Add a RD2-110 IP to a wastegated banks or factory turbo with a wicked wheel, and you'll make 250 HP (194% increase). This is basically the limit without studs, and you want them at this point.
    Now, do some more stuff - Intercooler, and possibly an upgraded turbo - and you can hit 280, 300+ HP.

    And, like I said... I found that the difference between a completely worn out motor(half the rings were broken, .020" of bore taper, drank a quart of oil every 50 miles(!)) and freshly rebuilt motor was... negligible above 2000 RPM. Idle to 1600 - where you have no turbo boost - yes, it makes a difference. Higher in the revs, though, the engine wear doesn't matter.
     
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  3. compressionignitionrules

    compressionignitionrules Full Access Member

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    [​IMG]Stans' headers look like this :hail
     
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  4. Thewespaul

    Thewespaul Supporting Vendor Supporting Member

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    I dont buy it, I’ve owned na trucks that would run circles around turbo IDIs, if all that boost and compression is going straight into the crankcase it doesn’t matter how much boost and fuel you throw at it. Justin proved that with a good na engine, headers, and tuning can make 200hp. Thats 60% more power than what you’re saying a new na engine is making, and without any boost o_O
     
  5. frankenwrench

    frankenwrench overkill is under rated!

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    R&d IDI performance
     
  6. IDIBRONCO

    IDIBRONCO IDIBRONCO

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    I don't know about Stan's, but it was Brian's Custom Exhaust before Stan's bought it. They used to claim up to a 30% increase in power with a pair of headers. That seems like quite a bit to me, but with an almost perfect tune, then who knows? The "H" (crossover) pipe was always included in their full exhaust kits as well. Was it needed? I don't know that much about exhaust theory.
     
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  7. Macrobb

    Macrobb Full Access Member

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    I'm saying based on what I've experienced. Everything I've laid out here is backed up by dyno numbers I've seen in person at a legit dyno event(Hunting 4 Horsepower in Coeur D'Alene Idaho), with SAE-compensated wheel HP numbers.
    I'm not convinced that's not /engine/ HP instead /wheel/ HP. Adding 20 HP to a N/A IDI with a little adjustment is totally doable. Adding 60% to one, not so much. They already run hot EGT wise, and the only way you are going to get more HP is to add more air. A *lot* more air.

    The one time I actually went to a local shop and had my truck dyno'd(it was an opening day type thing), the "big number" was the calculated engine HP. Which seemed close, based on what I see, but still a much bigger number than wheel HP, which actually matters(at the lower power levels we are dealing with, it seems around 60-70 HP difference between them).

    Here's another datapoint that I use: https://official.bankspower.com/magazine/banks-sidewinder-turbo/
    I haven't seen anything to *disprove* these numbers, and they are right in line with what I am seeing - ~125 range NA(they got 135 with a brand new engine), ~200 range turboed (they got 209). If you figure the fuel quality has probably degraded a little between now and then, or just plain wear on things... that's still a close range.

    Now, here's the thing: I'm fine with being wrong. Show me dyno sheets(along with how they are labeled - which number you use makes a huge difference), and lets talk.
     
  8. Thewespaul

    Thewespaul Supporting Vendor Supporting Member

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    Go read Justin’s thread on fte, the dyno sheets are there, it’s nothing new the data has been out for years
     
  9. Macrobb

    Macrobb Full Access Member

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    I saw it when it first came out. I just spent the last few minutes pulling up the topic and getting links:
    I did miss-remember it - he did make higher numbers in WHP. But I stand by my point.
    https://www.ford-trucks.com/forums/...ullsize-bronco-idi-build-14.html#post15549316
    He made 171 WHP N/a... with a whole bunch of water/meth: https://www.ford-trucks.com/forums/...ullsize-bronco-idi-build-14.html#post15548243
    And, blotted out the sun with all the smoke(according to the first post).

    So, no, I don't count that as making that much N/A. If you are smoking, that's not 'right' - you can't use that power for more than a few seconds, because of the high EGTs that will produce.
    And adding water/meth(at 25GPH) is fine for a dyno pull, but not for any 'use' of the truck.
    Oh, and that motor was anything but stock:
    So, I guess we know the absolute limit of a N/A IDI with everything you could possibly throw at it, aside from Nitrous.
     
  10. Thewespaul

    Thewespaul Supporting Vendor Supporting Member

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    That’s still over 200 crank hp, and almost 50hp more than you’re giving an na engine credit for. If you saw the videos of it na, it cleaned up the 90cc pump pretty well, got good mpg and had very manageable egts. Dynos are hard on diesels, most the time you end up with smokey runs that don’t equate to what they make on the street, and you have to play with the setup to favor the dyno. in the post you quoted he says it would have made more if it were adjusted for the dyno. As for the water meth, that’s going to help with egts some but it’s mostly a fuel, so for that na engine it likely wasn’t adding any power. And since when does a dyno number not count just because it was smokey? If you’ve ever been to a competitive diesel event that is the norm, and for most the 12v guys the amount of smoke he showed in the videos would be normal for a completely stock truck. Sure smoke isn’t ideal, but that doesn’t mean the data doesn’t count and that the truck isn’t driveable, your right foot controls the fuel, you just have to pay attention to it when you’re driving.
     
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  11. The_Josh_Bear

    The_Josh_Bear Full Access Member

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    Justin also used Total Seal rings or at least he shaved oversized rings down to gain every bit of cyl pressure he could. Ended up with great N/A power and 20mpgs(in his Bronco) driving like he stole it, lol.
    So for the OP that's an important detail in the engine build, this was not standard rebuild.

    Anyone know what the cost of Justin's rebuild was? I bet it's at least double a good turbo setup.
     
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  12. IDIBRONCO

    IDIBRONCO IDIBRONCO

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    In the end, it's still Enginerd's truck and money. He'd like to try to build some headers to get a little bit more power out of it for less that the cost of a new turbo kit. Let's just concentrate on trying to help him out. Once again, my truck in N/A form works fine for me. If I didn't like to go to high elevations in Colorado occasionally, I wouldn't bother with a turbo at all. Just for the record, it runs very well from the 2200 feet where I live clear out to the Front Range that can be from 5000-6000 feet. That's just with headers.
     
    Last edited: Sep 22, 2019
  13. Macrobb

    Macrobb Full Access Member

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    Yes, you are right. You will notice that the same day(same post), a stock N/A made the same... 125... that I rate a N/A IDI at.

    He's also only hauling a <5K bronco around, not a 6.5K truck, plus optional trailer.
    When you don't need to put any fuel into the motor(due to less work needing to be done), you get both of those.

    I've seen this, but I don't see why it would make any difference N/A. Turbo, there's a difference, if you can't get the turbo to spool quickly enough. N/A, the air you have is the air you have.

    It also cools the charge air, which makes a density difference. Doing some random numbers, at 120F and, say 20% humidity, that's .06833 lbs/cubic foot. Add water evaporating, lets say it drops the charge air to 80F and 100% humidity - thats .07256 lbs/cubic foot, or 6% increase in oxygen. Now, I'm not sure exactly what the real numbers would be, but it's something that Banks sure takes into account when considering how to shove more air into a motor to make more power.

    IMHO, if you can't tow with it, the numbers are just for show. And yes, I've seen a lot of poorly-tuned rigs on competition at H4H. I've also seen multiple properly-tuned rigs making good numbers as well. Those are the more interesting rigs.
    No, but if you have to take your foot out of it, guess what... you aren't making the same power as WOT. So that power is not there anymore - not usable.

    I don't have a problem with that; I'm just saying that physics doesn't lie. By all means - do whatever you want. But don't expect to get some magical number.
    I've gone the route of trying to tune and get power out of a N/A IDI and basically didn't get any noticeable difference.. I then slapped a used, $500 turbo kit on it in one weekend and made double the power(after cranking the IP). It was pretty much an outlook-changing moment for me.

    I'm looking here and thinking that the mods to make a smokey 170HP are far more involved and costly than a simple used turbo kit, that can cost $5-700.

    If you ever are in my neck of the woods, I invite you to drive one of my trucks. I can pretty much tell you that you will want a turbo after that.
    I will say that I've seen and driven poorly-tuned IDIT trucks that couldn't get out of their own way - if the timing or the fuel isn't right, you won't make power.
    Just a little tuning, though, and it's a night and day difference. And, if you do get the turbo all set up, and it doesn't feel as strong as I say it is, I'm more than willing to offer advice on getting it dialed in.
     
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  14. IDIBRONCO

    IDIBRONCO IDIBRONCO

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    Thanks for the offers. I know that you've done a lot of different things to these. I've watched several of your You Tube videos. I also want to say that I've had the full nitrous experience of Wes's Shop Truck. I want a set up like that, but I also know that I don't need it or want to pay for it. I fully understand the differences between need and want. One make for A LOT longer list.:dunno
     
  15. Enginerd

    Enginerd Registered User

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    Hey guys, I seriously appreciate all the input you've given. A few things I want to point out: I didn't mean to start an argument on turbo vs na, and really I shouldn't have even tried comparing them because there shouldn't be a comparison. They are two different animals in nearly every way! Sorry if I caused any trouble in that :D

    This hits the point as to why I am not going to add a turbo to a 320,000 mile motor. Yes, there is no argument I can make more power under boost!! But I don't like the idea of routing 9 exhaust pipes from the engine - 8 cylinders and one crankcase pipe from boosted blowby. Plus I think I'd have to change my oil often enough that it would be a hassle since I'll be putting at least 400 miles on a week.
    I made mention in the beginning that I'm not looking to build a hot rod, just something that is efficient and strong for what it is - a simple, reliable, mechanical diesel with no extra moving parts. I don't want to take apart my engine and find broken piston rings either. Headers are very cheap material wise. I want to learn how these engines work and respond on the exhaust side for a few different reasons. I had an idea come to me on header design that after working the math out I really felt like it was a game changer (in the non-boosted world). I want to try it out on this motor because it seems like there is really only one business who has tried anything. IF I can get something out of this design, it might be helpful to those who want to stay na. Also, in the hopefully distant future after I have to rebuild the motor, I would like to supercharge it. I like the idea of a supercharger on a diesel like this and the potential in that, but I want to figure in a good exhaust first.

    I'm really excited about this diesel engine because (please correct me if I'm wrong, like I said I am new to this engine) there is no throttle valve... meaning that the engine's breathing is always a WOT condition, meaning that you are always experiencing a max volumetric efficiency. So assuming a perfectly uniform timing of the exhaust pulses merging together, scavenging could have a major effect on the volumetric efficiency. These are pretty low lift, low duration cams so that poses a challenge, but a well played NA exhaust and intake could really do good in filling those cylinders with fresh air and exhausting the residual burnt gasses.
    So, all that being said, thanks again everyone for their input. It appears this is an unexplored aftermarket area of these engines and it's cheap enough to give the exploration a go personally. I like experimenting so this will be a good place to spend my time. Maybe I'll be able to come back in a year with dyno, EGT, and real world results to show everyone.

    Thank you Thewespaul and IDIBRONCO for the encouragement, I'll take it and run. It is after all... just my truck. I love the wealth of information and experience I've found in this forum and I am glad I joined!
     
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