Choosing a Turbo for your IDI: Turbo Components, Specs, and Compressor Maps.

Thewespaul

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Quick question at what pressure level are head studs needed and at what point would you recommend putting in head studs. Unfortunately the turbo swap I started years and years ago didn't really work as I'm only getting circa 5-7 psi at WOT. I've got another turbo to replace that one however and hopefully it will work. Planning on either selling the truck or giving it to my parents after I get in running again now as I gave in and bought a truck, used because I can't see spending 80k on something that won't do 155 at least ;burnout
I really only like to push them to 12 psi on the stock head bolts, and I bring timing down to 7* to bring cylinder pressures down and to help spool. I have two customers running 15 psi for some time now with no issues but I feel thats pushing it. Personally, I have yet to blow a headgasket from running too much boost, and I plan on doing some testing in the future to get some solid data on how much you can push them.
 

Thewespaul

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Thanks for dropping that knowledge. I read something about stock Rods here. I have a 1994 K Vin 7.3 IDI, I think it makes with the turbo about 125 Hp. It has 306,000 miles on it. Would i have to pull the engine out of the bay to put an R & D stud kit on it ? My goal is about 300 hp. Am I in danger of blowing my engine trying to get that out of an old engine like that ? Also i have only removed the crimped down pipe but the rest of exhaust is stock but i plan to go 4” exhaust with stacks and clapper caps.
Pull the engine to do studs, you can have it done in a week easily, but if you do it in the truck expect it to take four times as long. With that many miles on a 7.3 I would at least do a head job on it with new guides and seals. While you have the heads off check the ring ridge, if theres a significant ridge it would be a good idea to do a hone and rering, all things you can do at home without any real specialty tools.
 

Crawler

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not to throw another wrench or stir the pot. but what of your thoughts of true twins? one on each head like that jaguar sled pulling car. i think they are running k27 or k17 turbos on there with a p pump. obviously this for sled pulling only, but what the applications for this for everyday use?


An issue that many don’t consider when looking at true twins is that you are taking the exhaust energy and dividing it in half between the chargers. Not only that, you are dealing with less exhaust pulses or events per charger.
Both of these play a major role in driving your turbocharger(s).

Also, when a second charger is added you now have more rotating mass that has to be brought up to a very significant RPM in order to produce pressure.

In compounds the smaller charger is receiving all of the available exhaust energy. Then the larger(atmospheric) charger is receiving all of the exhaust flow still, but a little less energy do to thermal loss(time/distance of piping/driving of the first charger all impact this). However there is still plenty of energy left to drive the larger charger and you also have all of the airflow going through it.

In “twins” each charger sees have of the drive energy. Neither sees all of the energy. In order for the chargers to spool well, they have to be sized quite small, due to the amount of exhaust energy that our engines can produce(as well as our limitations on airflow due to head design). Unfortunately you cannot run tiny shafts in chargers on a diesel and make them live.
The mass of the shafts as well as the compressor wheels, and exhaust turbine wheels, all adds up.

In order to have a turbocharger that is built robust enough to live in a diesel application, a single charger is a better fit for most(if not all) diesel applications than “Twins”.

As Wes was discussing earlier any charger has certain airflow characteristics. Smaller equals faster spool up, but a limited top end number. Larger takes more energy to drive and spools slower, but has a higher overall capacity.

If you go too large on any turbo charger (single,twins, compounds, triples, etc...) then you may not have enough exhaust energy to ever get on top of the charger. Meaning you may never get the setup fully spooled.

Compounds gained a ton of popularity and for good reason. You can put a small enough charger on to get good bottom end power while being able to run a larger atomospheric charger to provide enough airflow for higher rpm power.

Keep in mind that on a set of compounds it is still a compromise. I will use The k series turbos in this example for since I quoted a gentleman asking about them.

The following example is working under the assumption that when running the compounds or the k31 as a single, that the overall fueling is the same.

The compound setup will spool slower than a single k27 due to needing to draw air through the k31 and due to not having a free exhaust path behind the k27. However it will spool dramatically faster than a k31 as a single.

Also the compounds will have a slightly lower overall power than a single k31. This is due to pumping losses, exhaust energy losses and the restriction that the k27 now places between the k31 compressor and the engine.

Compounds must be matched in a way. Meaning you can’t run a tiny small charger and a huge large charger. They must work together. We see this in Cummins/Duramax/ModernPowerstroke world quite often. I will have to let Wes or one of the more knowledgeable IDI guys here tell you what they have seen work on these engines. But using the number he provided concerning fueling and airflow requirements we could math it out.

The following is from working on Cummins compound setups. So take it with a grain of salt.

For a towing setup on a mechanically injected Cummins we often use a k27 as the small charger and a BW 475 as the larger charger.

As we go up in power/fueling (competition trucks not towing)we start looking towards other combos 363/475, 464/480, 472/491 and so on. If we mismatched the combo then the overall performance would suffer.

Keep in mind I am talking in generalities here. There are individual cases that can be looked at.
 

Goose_ss4

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That compound set up you showed before realy got me thinking. To bad I sold my ats kit about a year ago. Looks like I could have used it now. Looks like a good and simple with the stock up pipe set up. I am not a huge fan of these up pipe since they always seem to leak at the y-pipe over time
Welding them was a great idea to help with leaks. Wonder if up grading the connections to a v band set up would work on them
 

Crawler

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If it's a bolt on for the IDI and the ZF5, I'd buy one at $800.


I could be off base here, but I’m not aware of any of the big boy diesel clutch company’s making any high torque/hp clutches in a dual disk for anywhere near that amount. I’m not tLking about IDI, I’m talking about all platforms.

There is a significant material and machining cost in going to a dual disk setup, for the manufacturer.

Add on top of that, a limited market.

I would love to see a quality dual disk for any diesel platform in that range. But I wouldn’t forecast it.
 

austin92

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I could be off base here, but I’m not aware of any of the big boy diesel clutch company’s making any high torque/hp clutches in a dual disk for anywhere near that amount. I’m not tLking about IDI, I’m talking about all platforms.

There is a significant material and machining cost in going to a dual disk setup, for the manufacturer.

Add on top of that, a limited market.

I would love to see a quality dual disk for any diesel platform in that range. But I wouldn’t forecast it.
I think vlair is selling a powerstroke dual disk for under a grand and south bend has them starting at 1100. We wouldn’t need anything crazy just a little more than stock. If there was a demand, I think they could still make money off an 800$ set up


Sent from my iPhone using Tapatalk
 

Chemgrad

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Thanks for the info. I have a small turbo from a Chevy diesel that I'm putting on it. I've already done all the fabrication to make the big turbo work so putting in the smaller one is no biggie. I think it is a GM-8 or something like that been a while since I bought it. Honestly at this point I just want to get it out of my yard and get back some some of the money I have into this truck and stuff. I was thinking about using the bigger turbo in a compound setup for our Ram 2500 but looking at the number the lying POS who sold it to me gave me "assuming I can trust them" I think it is too small for that. So I'm stuck with a crappy ass Turbonetics wanna be turbo that's probably not going to work on any truck. Maybe I'll talk my Dad into putting it on his 351 Windsor in his 87 F-150 :)
 

nelstomlinson

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Wes, I want to build a turbo engine on an NA block, with studs and a typ4 cam. It will go in a '94 crew cab with E4OD. My goals are reliability and durability, decent mileage and more torque and power, listed in order of priority. Is about 250 flywheel hp a sane number to shoot for?

That is about 250/2.75=91cc of fuel,
91*7.5=670cfm,
670/14.47=47 lbs/min airflow.

The R&D turbine seems to be about right for this. Would a bigger turbo blast more air through and help lower EGTs?

I'm trying to read those compressor maps. The pounds per minute axis makes sense, but what does the pressure ratio refer to? How do I determine where I want to be or where I am on the vertical axis?
 

Thewespaul

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Wes, I want to build a turbo engine on an NA block, with studs and a typ4 cam. It will go in a '94 crew cab with E4OD. My goals are reliability and durability, decent mileage and more torque and power, listed in order of priority. Is about 250 flywheel hp a sane number to shoot for?

That is about 250/2.75=91cc of fuel,
91*7.5=670cfm,
670/14.47=47 lbs/min airflow.

The R&D turbine seems to be about right for this. Would a bigger turbo blast more air through and help lower EGTs?

I'm trying to read those compressor maps. The pounds per minute axis makes sense, but what does the pressure ratio refer to? How do I determine where I want to be or where I am on the vertical axis?
Totally doable, I think the s257 sxe would be a great investment, spools sooner, more efficient design and more power potential. With idit internals you could do double the hp and still be within sane limits where you’re not pushing anything. Im working on a second thread that will explain the rest of the map including the vertical axis. There’s a lot of math involved in it, so I will need to sit down and try and get the equations set up as simple as I can so it make sense for everyone. I’ll try and get it done and posted tonight
 

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