Ok, that was a good explanation how I should have my turbo be larger than my IP.

Lets just say hypothetically that I had the stage 1 turbo and the 110 pump, I'd still have to decompress my engine correct? Also this combination would burn more fuel than my 093 and the 90cc pump correct? albeit less powerful.

Devin

 

The fuel consumption would only change during moments when you were actually using peak power (wot). Unless you drive with your foot to the floor constantly you will never see the difference. Justin had the 180cc on Smogie and got some of the best mileage numbers I have seen for that configuration of truck (18-ish highway mpg lifted 4x4 on 35" tires).

The decompression is necessary if your set up will boost higher than low 20's psi (on a 6.9). If you have enough fuel and enough turbo to push 30-ish psi you run a serious risk of producing peak cylinder pressures that are high enough to lift a cylinder head even with ARP studs. 7/16" fasteners just do not have enough clamping load to prevent this. If the head lifts the gasket material will burn beyond the fire ring and fail. There have already been failures with a 90cc and BW256 turbo pushing high 20's psi. Fresh rebuild, ARP studs. The 110cc and Stage 1 turbo will likely push low to mid 30's psi. Lowering the static compression ratio lowers the peak cylinder pressure and allows you to run more boost. It also lowers EGT's. The down side is it reduces your low end torque, it makes it harder to start in the cold, and it will smoke more when cold. You don't want to decompress too much or you will have problems. There is no set formula, and you really need to do your homework on this before deciding to push power out of a 6.9. This is why most guys wanting to build up an IDI go for a 7.3 with 1/2 inch studs. Justin proved the NA rods will fail before the head lifts. You can run much, much higher boost without having to decompress. There are many factors that play into gasket failure like engine timing, EGT's, engine load, rpm, etc., and results will vary. I am just pointing out a weakness that needs to be considered when planning a 6.9 fuel and turbo system. Hope that helps even though it is brief.

 

I would definitely recommend the decompression gaskets if you plan on pushing the engine very high. Another thing that you could do as well would be to get some custom ARP625 studs or tap the block for bigger studs. That adds some $$$ but is an option for the 6.9.

 

You're getting some good help here. I think also you suggested early on that you were quite prepared to stay n/a so I am wondering what purpose you have for the extra power from the turbo/larger pump combo.
If it is for better performance loaded, you will certainly achieve it, or even if it only gives more satisfaction/enjoyment driving your truck that's great too.
Having read lots of posts on the topic since joining this forum, and looking at some of your questions and reasoning, it is possible that you might get most benefit from a standard IP turned well up, a pyro, and possibly studs although mild boost and studs may not be an essential combination.

You guys are lucky in that in this small burg any of these trucks are rare, and head turners, mostly people have Japanese SUVs here as they are the norm for supply, and therefore the breakers or junkyards as you call them don't have much in the ex us line to play with.

Also, any modifications to a vehicle like turbocharger, body lift kits, auto to stick conversions, wheel size what have you are subject to stringent whole vehicle safety checks and documentation at considerable expense I might add.
I will endure with 6,9,ç6 for that reason in n/a, not many of our hills are over 2000 ft, so my focus towing 7000lb will be, keep it cool and wait. I have a good stereo.
Work out what is best for your budget, your fuel use probably won't change much, but your vehicle may be more driveable in your chosen usage.

 

ARP does not offer +625 alloy studs for the 6.9 on a standard basis. Member Bronco78idi here was going to have ARP custom make a set out of that material but at a cost of ~$2,000 (vs. $250 for 8740 chromoly) it only made sense because of how much he had invested in the engine by the time he realized he needed them. The torque specs are scary high, and the clamping load still does not match the bigger studs. Bottom line is for the money there are better options.

I know I will sound like a hypocrite since I am planning a fairly maxed out build, but I really admire the super efficient and optimized fuel/turbo combinations like what Justin had with his 90cc + A3000 turbo (now his stage 1 would be even better). This made for a very responsive and potent truck without over-stressing any parts. It had a really strong power band right where you most often use it, and no side effects from decompression, touchy governor, turbo lag, etc., which are the compromises you have to accept for higher power levels. More is not always better, and depending on what you want your truck to do you need to answer for yourself whether the drawbacks are worth it.

 

Yes for sure! That is why I said custom ARP625. I never meant to make it sounds easy or cheap by any means. And yes Robert spent done cash on those. The best route for most if you don't really want to tear into the engine much would be to keep it at an RD110 and below and size the turbo accordingly. It all depends how much money you want to throw at it. Performance costs money...

 

Just as an observer to the conversation with no turbo experience here are my thoughts ..

The 6.9 is limited by the 7/16 head studs ..

the best quality seems unaffordable so probably should limit expectations to arp 8740 stud capabilities being max safe 20psi ..

The best price i was able to find for 6.9 studs were here >>
ARP Head Stud and Head Bolt Kits

[Disclaimer i have not affiliated with and haven't purchased from this company. .. do check customer service and verify that this is reputable company before placing order ~ if anyone does buy these please report back with your experience with ordering from them]

So seeing as there is a max limit of how much power potential a 6.9 can produce .. what is the reason a standard n/a pump couldn't be used .. after all. .. turned up they will blow enough fuel and smoke to melt a non turbo'd idi ..

And a diesel can be run leaner than a north korean .. fuel being metered by the throttle / ip not vacuum drawn like on a gas motor .. for such a build with limited power wouldn't a quick throttle response and fast spool with a lesser fuel flow and flatter fuel curve make a better driver ..

Just seems like top end is gonna be limited anyway .. if bottom end is also limited with slow spool and dumping excess fuel inherent drivability issues (albiet solvable with that cool aneroid gizmo/ essentially making it n/a again off the line) then gains would be real but just limited into the mid and probably not huge top end .. just rambling. .. and enjoying reading all your responses ..

 

Yup; totally turbo-limited here. Now 240-ish whp isn't bad; Without a trailer, it's pretty hard to use anywhere near that for more than a few seconds of acceleration.
With 8K of load, yeah, you can actually use all of that HP going up hills.
On the highway, my last trip with my dad's Bobcat(8K trailer weight), I only /once/ got my EGTs up to max and had to back off; that was going up one steep hill near my dad's place at 45. Still managed it in 4th, and 2400-ish RPM.
On the reasonably flat highways I was in overdrive most all of the time, holding 650-700 EGTs.

I've also hauled 16K before with the same HP; that was a bit of a load. Yeah, it was actually a struggle to maintain speed going up hills; I think I dropped to third going up a steep hill....
...I realized later that I had my emergency brake on the entire time(leaking axle seal is made worse by hot brake drums)

So yeah, for normal use, a 90cc, stock-turbo IDI isn't a bad rig. Good enough HP for most things, and a solid setup that will handle it for hours on end.

However, as you might expect, I'm not really satisfied... so bigger/better turbo it is!

 

From what im guessing, the OP is wanting "as much power as is practically possible" With a 6.9, my humble opinion is a 90cc pump, stage 1 injectors, 093 turbo kit, an intercooler, and head studs. A cam wouldnt hurt either, but would require opening the engine up to some degree.

The combo im giving above should give really strong low-midrange torque and good midrange horsepower, while still getting good fuel mileage under load, and be responsive, and should do it without overstressing the the head gaskets.

 

What about tapping the block to 1/2 studs? Why don't we hear about that more on 6.9's? I thought the 6.9 was more coveted for rebuilds because of its thicker walls?

I more than likely will buy another engine in the next year while mine is still running and rebuild it on the bench. But 6.9 or 7.3?

Devin

 

I feel like a had another article, bookmarked somewhere like this one,

Rebuilding the International 6.9/7.3L Powerstroke Engine - Engine Builder Magazine

Devin

 

How many 7.3s actually have cylinders fail from cylinder being thinner? I'm building a 7 3l and plan to run 20psi plus on a daily driven truck

 

Justin tried to put 9/16 studs in his 6.9 after he had gasket failure with 7/16 studs. It works if you keep the 6.9 stud length and don't try to go as deep as 7.3 studs... however Justin tried it the DIY method and discovered it really needs to be done by a machinist with the right tools. By the time you pay somebody to do this the right way you are better off sourcing a sound 7.3 block and heads to work with. If you want thicker walls and bigger fasteners it is your call... find a machinist to mod a 6.9 block for bigger studs or sleeve a 7.3 down to a 4.00" bore. Just remember that if you sonic test a 7.3 and it's ~not cavitated, we have yet to see a block fail as a result of performance building, but we ~have seen NA rods bend. Any 6.9 build is limited to NA rods unless you bush turbo rods for the 6.9 piston wrist pins. And the snow ball grows. Unless you are a machinist and can do a most of the work yourself, I think you will find that a solid 7.3 core engine is your best bang for the buck.

 

Good point, I will go down the route of looking for more info on 7.3's then. Doesn't adding sleeves to the 7.3 require a lot of machine work too?

Thanks Again,
Devin

 

Yes, sleeving a 7.3 block is not cheap. If I have a block hot tanked, magnafluxed, line bored and honed, decked, and cam bearings installed I'm looking at ~$350 in machine work. To have it sleeved on all 8 cylinders (which would include everything above) I'm looking at ~$1,250. So +$900 for the sleeving. I could be way off base, but I'm not thinking that having the heads and block of a 6.9 drilled and tapped for bigger studs would be much cheaper though...