3 inch. it does not reduce and then open up. i am pretty sure it it is a 4 inch wheel

 

The factory turbo has a 2.229" exducer on the turbine wheel... That's the diameter of the exit of the turbine housing.... And it has a wheel occupying that space as well...

3" is plenty sufficient for any of us, but going bigger doesn't hurt, just better scavenging...

 

I 100% agree on all counts, which is why i originally looked into the roller rockers.

7.3 had revised seals to reduce the amount of oil consumption (read:guide lubrication)

 

Any idea if 6.9 replacement shields are the original design, or are all 6.9 gasket kits "upgraded" to the interchangeable 7.3 style?

 

Just read this thread and am following it. Some very good questions and answers.

 

A few Myths I heard.

1. A Powerstroke crank shaft can be used in the IDI
2. Powerstroke valve springs can be used in an IDI.

Are they true?

 

1: no

2: Yes...

The PSD and IDI valve springs are the same.

Only springs to use in my opinion are the comp 910-16's...

 

interesting thread! Some knowledgeable guys on here with thorough explanations. Glad I saw this

 

I thought 7.3's had bigger head bolts?

 

That's true, one of the minor modifications when they bored it out.

 

myth 3 inch exhaust is all an idi needs.

fact any turboed engine will use a cone as the ideal exhaust, so larger is better, but may not be necessary for your setup


myth there is no stroker kit for these motors ( as i was told on other sites)

fact yes there is and its costly though, someone may remember the name.

myth there are no proformance parts for the idi

fact yes there is cams, rockers, valve springs, upgraded turbo setups, higher cc pumps, a girdle, lower cr pistons, and more

myth glow plugs suck

fact improperly functioning gps suck, but a well maintained system with all the proper parts will be a lifesaver

myth do not use starting fluid

fact its fine as long as you do not use gps also, disconnect the gps when using the starting fluid. i have proven this batteling with following many of the manual control systems out there. if you use manual control keep the copper squiggle (resistor) as it will drop the voltage and keep you from burning up plugs.

some id like answers to

whats the best pop pressure for an injector?
is there an injector better than others?
has anyone removed the gp system for something else? like an air grid?

 

1- Depends on the amount of Fuel being run.

2- Only if the injector is new, otherwise, no.

3- Don't know, works on a Cummins, don't see why it wouldn't work on our engines. I don't think the GP's are much of an issue though?

 

1 whats ratio? higher fuel higher pop?

3 you would think its a problem if you have had all the issues i have.

and ps racin check out my build thread got a question for ya on there thanks

 

I'm curious about this... how did you come to this conclusion?
The facts are the IDI has more immobile surface area than piston surface area. Regardless of the power you've made (Well done! ) the fact is... Pre-cups do hinder performance if for no other reason than they exist.

I'm not busting *****, I found this and your other threads while doing some research for my own IDI 6.9. I hope you can prove me wrong

 

Im glad this is questioned, trust me, it took a long time for me to wrap my brain around it as well.

The number one reason I have come to this conclusion is simple.... The conclusion...

The fact that we can produce 2.81hp/cc is the reasoning behind it not being a restriction (At least on these particular engines, at these particular fuel levels, at these particular RPM's, at these particular timing specs). Granted, that was done on an engine with only 130ccs of fuel, and comparision engines so far (My DB2 dyno and DB4 dyno's) have tossed down 2.61 and 2.13* cc/hp (*hp/tq peaked at less than previous dyno runs due to a slipping clutch, numbers show it was down 50whp) those particular pumps had stockish fueling curves as well. Even a 7.3psd struggles to get to 2.81hp/cc (Read never) unless it is a highly tuned/optimized engine, and that is with computer controls. Our engines can only be tuned mechanically, which relegates us to base timing, fuel inlet pressure, and injector pop-pressure.

This is my theory on the matter. We can compare our engines to the 7.3psd, because they are nearly identical, aside from the injection type/control system. I feel that direct injection is superior in a highly tunable, high pressure computerized system, but when comparing a lower pressure mechanical or computer operated system, the injection pressure is key, and this is why IDI was engineered in the first place. You can use a lower injection pressure and achieve the combustion characteristics of a direct injected engine, it was the bandaid to do the very thing that common rail does today (Obviously in a less sophisticated form)....

Now, the same characteristics that make IDI comparible (NOT the same, NOT as Good, but comparible in characteristics) to commonrail, also make it achieve a better burn. Ive researched just about any study I could find on combustion characteristics in a diesel engine, and the one correlation that has never made sense, is the idea that IDI is a slower burn process. This is completely untrue. The IDI burn starts slower (Initial flame front, etc) but catches up and surpasses a burn of a low pressure DI setup. The reason this happens is the obvious, the pre/semi-combusted fuel is forced through the "little throat" everybody complains about at far more of a pressure than a DI nozzle injects fuel into the piston of a DI engine.

So where is the proof?

I would say the proof is that we make the HP/TQ numbers at far less timing than any DI engine could imagine. The big IDI numbers we have put down are in the 6-8* BDTC base range, with full timing in the 12-14* range. Not only are we utilizing the fuel we are burning, but we are burning it in less time.

That is my conclusion on IDI not being limited like you always hear.... At least on this particular platform....