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Transmission Junkie
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Discussion Starter · #1 ·
I have a GT-42 and am looking at using it on my truck... its a 1.23 exhaust housing and i don't really want it to be too laggy for street driving... should I make it compound with another turbo or should I just use it with some B codes and get a good chip made. This is my daily but its a fully built engine, I already have an engine on a stand that I am building.

I want to have 600 rwhp when i turn it up.

:shrug:
 

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Laces Out
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as a single to make that much hp you're gonna have something that smokes a bit, prolly a lot...but in a compund kit you can prolly use it as ur big charger....then use a small drop in turbo as your lead charger...or small charger.... may smoke less and run cooler.
 

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I'd say twins would be more streetable at that level.

But can't say from experience cause I can only dream about twins... :( :aiwebs_001:
 

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Transmission Junkie
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Discussion Starter · #4 ·
I really don't care if it smokes... thats part of the fun of a diesel... :poke:

If i use it in a twin set up.... what kind of drop in do you think that I should go with...

TN drop in 1.0?

I was thinking about figuring something out with a turbo similar to the H2E, that way I can build it with whatever a/r housing that I want, i want to keep drive pressures as close to 1:1 as possible....
 

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But can't say from experience cause I can only dream about twins...
Don't tell my wife, but I dream about twins too.........
 

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Transmission Junkie
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Discussion Starter · #6 ·
yeah.... def a dream of mine...
 

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Village Idiot
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iirc that is what danny uses, and said it takes a bit to spool up..
but when it does , look out.....might be better off in a compound setup.
 

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DI POWER
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GT-42 doesnt smoke too much , ask Thuglike he has one.....................YEAH Right................put the fog lights on.:cool:
 

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Corona Killa
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iirc that is what danny uses, and said it takes a bit to spool up..
but when it does , look out.....might be better off in a compound setup.
I believe he runs a gt45r
 

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iirc that is what danny uses, and said it takes a bit to spool up..
but when it does , look out.....might be better off in a compound setup.
I think Danny was talking about his 45r. If I remember right, he's going back to a 42r.
Seems like you could pull it off, but compounds are the ultimate in driveability from what I understand
 

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When funds becomes available I'm gonna let Pius have fun with my GT42R and whatever else he wants to toy with next year. :ford:
 

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First of all, what boost do you plan to run and at what rpm do you plan to run that boost?

Secondly, which 42 do you have? There are serious differences within the "GT42" heading. There is one that has a 96lb wheel. Which do you have?

Only after answering those two, and the first with reality in mind, can you decide how to best use this 42.

FWIW, it would be too small for the first stage on my truck. Hence the GT47-88. With an efficient set of compound turbos you start moving a LOT of air real quick. Combined with the relatively low PR of each charger and you start flying to the top of the big turbo list real quick for the first stage compressor because the low PR just calls for a very large compressor to still be efficient that low and to the right in the map.

Just for fun, start at around 100lbs/min. That's a good guesstimate for a 600rwhp fuel only truck running compounds. Now imagine that if both chargers were balanced (meaning equal Pressure Ratios) that at 60psig boost you would be running them both at a PR of around 2.2 or so.

Start plotting 2.2 (60psig or so) or 2.5 (which would be boost in the 80psig range) all around the 100lb/min flow mark and see which compressors start looking good to you.

Good Luck.


On Edit:

This is a 5 sec paintbrush plot of some rough points of where my charger should operate. Yellow is lugging at full power. Need this point inside the surge line which it plots to be. Blue is towing with the first stage making around 15lbs of boost. Dead nuts on the map. Red is pretty close to where the first stage will run WOT at peak power for now. This should show you that the 47 is actually a compromise for towing and driveability. A maximum effort system would actually employ a larger unit. And the Green represents where the system should eventually run up to once some other things are finally sorted out with the rest of the truck and it starts pulling mid sixes on fuel.

http://rides.webshots.com/photo/2502852750082519711gqlqiL

The numbers are VERY rough, just off of some faint memory of when I sized everything a year or so ago. But should serve to get the basic idea across on how mapping is generally done.
 

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Transmission Junkie
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Discussion Starter · #14 ·
Its 78mm inducer dia. I don't know the trim of the wheel off hand. I've been told that it can flow a max of 95lbs by the guys at precision turbo.

If I need something more I have access to a 91mm turbo, which is a little bit bigger than your GT-47 88, I was realisticly looking at 80-100lbs of boost to make that kind of power... I figured that it would take some rpm on fuel only probaby around 4000k, after all RPM=hp mathmatically speaking.
 

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Yeah, my 47 is by no means big for the job.

And try 3400rpm for 600hp on for size. I plan to do around the same 1000ft/lbs I make now but at 3400rpm. That's not 600rwhp, that's nearly 650.

It doesn't take the massive increase in rpm that you might think.

4k would be good for over 750rwhp at that same 1000ft/lbs. But a much more managable scenario is to simply run 1100ft/lbs at 3800rpm. Thats good for 795rwhp. And I for one see no reason that stock rods cannot do that at all. 1100ft/lbs would be just outside of what I would consider daily driver reliable, but nothing extreme. I believe it has been done on PMR's, so god knows forged should take it for no other reason than that. Nevermind how many forged rods have taken that much and more.

But then again, I am one of the crazy ones.....

;)



I just remembered that the GT55 is a 91mm turbo. If that's the one you're reffering to, then it is actually not really "bigger" at all. The map on the 55 leans SHARPLY to the right. Meaning it would be easy to slip into surge down low (like towing). And the map is VERY tall. The map on the 55 is nowhere near the size of the map on the 47. The 55 is basically a 47 made for high boost. The 55 is designed for a single stage system, like a big single or parallel twins. The broad map and the drivability/usage potential that come with such a broad compressor map was a major portion of my compressor choice. A GT47-88 is a very capable turbo. Varied usage such as cruising, towing and all out decently well in one unit.

JMHO of course. I'm no Garrett engineer, lol.
 

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You'd be surprised what you can really lite with 444 CI.

I am nowhere near Charles' HP #'s, but we put a 91MM Thumper on a daily driver.

What we run on my truck is actually smaller to meet DHRA rules. We did compensate with some added air density.
 

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Transmission Junkie
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Discussion Starter · #18 ·
The cubic inch isn't the problem at all.... with a 360 gas engine we ran the 91 and a 101 thumper, the only difference between the two was the impeller... they both ran extremely well...

what i find funny is that charles says stock rods... and all i hear elsewhere is 500hp MAX, and I know that there are a few out there that are making more power than that with the stockers... im just trying to understand why you are claiming that it can be done why others say it can't, is it tuning and tuning strategy? I know that there are millions of ways to tune an engine, i tune gas engines all the time, from 2.0L hondas with 300-500hp, to 7.5L engines with 2000+hp...

i would have no problems running the stockers if I knew that it was safe... i have access to cryo and micropolish(stress relief) at work so, lets hear it...
 

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Well, what breaks the rods in the first place? Force. The easiest way to measure this force is to look at the pressure acting on the surface of the piston attached to that rod. That is where cylinder pressure analysis comes in. You just cannot run but so much cylinder pressure for but so long before the rods start to get short on you. It's slightly more in depth than that, but that is really the basic concept of it.

Now the engine's torque comes from the BMEP (Brake mean effective pressure) basically. Just what is the average cylinder pressure throughout the powerstroke in simple terms. The longer you hold a higher pressure the more torque the engine can produce. And for any given rpm for peak power, more torque equals more power and we go faster as we have for so long.

Holding things like drive pressure, timing icp and so on constant....you will reach a cylinder pressure limit at or right around the same torque value everytime for any given engine rpm. So that means, that if the engine rpm for peak power were held constant, you would nearly always be hitting this wall in power that was actually a wall in torque, that was actually a wall in cylinder pressure that you cannot cross without expected failure.

So. If you do not increase the engine operating rpm for your power peak then you are limited in total power production because you are limited in torque production due to it's VERY close ties to cylinder pressure. (The thing that breaks the rods).

Combine this with the fact that the stock PCM will NOT allow you to make your power any higher.....and you have a wall forming at around 500rwhp because that equates to a torque value of right around 1100 or so which equates to a cylinder pressure that is killing rods in most trucks. If you do better on drive pressures and timing and such for that 1100ft/lbs you can live longer than others. But it's still a pissy little game to play to try and make more power by making more torque.

What did DB make for torque last time out? 1400+ ft/lbs. Blocks don't like that. It's because he made his power at a dismal 2600 or so rpm. You have to punish your way to some power at that kind of rpm. What did he make, 750 or so hp? The reason the nitrous was required was to make that hanus 1400ft/lbs of torque.

Imagine instead, he had simply run around 1200 ft/lbs at 3400 rpm. The truck would not have needed nitrous oxide to make the 1200 with compound turbos, and it would have made over 775rwhp and still be driving today without having ripped its own crankshaft off of the block. With aftermarket rods 1200ft/lbs is a non-issue. And I think that anyone can see that 3400rpm is a non-issue for any powerstroke. I wouldn't expect any failure until you exceeded around 3900 for a while. I think they'll live long at 3800 rpm so says my piston acceleration/force work as well as the 60 or so hours I have personally logged in an OBS at precisely 3800rpm in 1 to 2 hour increments. That engine now has over 300,000 miles on her and it's still pulling skid-steers everyday for a landscape company.

If you can't make the injectors stay on past 26-2800rpm, then no...you cannot reliably make over 500rwhp on stock rods. But if you can keep them on, you only need to push the rpm up a tiny bit to get amazing rewards in power without even a 1psi increase in cylinder pressure.

But that's just me talkin
 

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Transmission Junkie
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197 Posts
Discussion Starter · #20 ·
This is the kind of useful information that I was looking for. I understand completely what you are speaking of.

In laymans terms to make 500hp at 2600RPM it take x cylinder pressure

if you want 600hp and you try and make it at the same rpm the cylinder pressure has to increase by a certain amount, im sure i could do some math to figure it out but its friday morning and i really don't feel like it.

so if you take the 600hp figure and move it to say 3400 rpm, then the cylinder pressure at 2600 becomes less than it was at 500hp.

as i have stated before RPM = HP, its simple math...

rods are cycled, compression and extention, on most gas engines that break rods the rod bolts actually stretch too far and the bearing begins to sease on the journal resulting in a spun bearing and then the rod breaks, to counteract this process you have to upgrade the rod bolts, or you have to reduce overall piston, wrist pin, and small end of rod weight, or a combonation of the two, because of the exhaust stroke on a rod there is not nearly as much pressure on the rod and the rod stretches,

if you ever mock up an engine put a bearing in the rod and torque the rod with the rod off of the crankshaft, when you check the bearing it isn't a perfect circle, its wider where the cross section of the rod is, that is a design to keep the bearing from catching on the crank when the bolts stretch.

So if we were to get custom pistons made... I have priced them from the custom piston manufacturers, and they were reasonable, and have them lightened in the correct areas without sacrificing strength, one could easily subject one of these engines to higher rpm without the worry of destruction
 
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