Bigger Cube, Lesser Fuel, HX35 sizing

[RacinNdrummin]

Setup is as Follows:

94 IDIT 7.3
178/190@.050 cam
21.5:1 compression
90cc of fuel to 2800rpm, 75cc@3300.
Garden hose nozzles
HX35 (8 blade 56/82 cold wheel, 12cm housing with bigger puck and through drilled)

Made significantly more power at 17psi than it did at 21psi, and after finding the sweet spot on the dyno, it was at 2:1 DP to BP...

Here is the chart, and my explaination chart to follow:

[ame="http://s72.photobucket.com/user/loneobjectivist/media/Dyno%20Day/002_zps6d9775ff.jpg.html"]002_zps6d9775ff.jpg Photo by loneobjectivist | Photobucket[/ame]
[ame="http://s72.photobucket.com/user/loneobjectivist/media/Dyno%20Day/explain_zpsbae96f12.jpg.html"]explain_zpsbae96f12.jpg Photo by loneobjectivist | Photobucket[/ame]

The truck is getting the BAE 62/86 cold wheel and I need to figure out if we need to pick up a 14cm WG housing, or a 16cm NWG housing to run on this thing....

The catch is that it is getting a 190cc pump bolted on after we run the 90cc setup with the new turbo...

Any advice would be appreciated...

 

[RacinNdrummin]

Re-reading this, I realized I left out some significant info.

The 17psi was with the WG hooked up, and the 21psi was just plugging the tube.

Hp goes flat at 2300RPM and 200whp until the pump starts to defuel (~3000).

It has a fairly thick haze all the way up to 3000RPM.

Timing was everywhere from 5*BTDC base to 14*BTDC and it made the best power right about 10*BTDC, Any more lost power due to the fuel volume, and anything less choked the turbo more.

I ran some numbers, and a 7.3 IDI is moving the same amount of air at 21psi as a 5.9 Cummins at 35psi, and that is generally where the holset starts getting inefficient. Being that its the same exhaust housing with more exhaust volume on the same wheel, could we be overspeeding the cold wheel for the amount of air the engine is moving?

And before any body asks why an HX35..... Its on purpose, this seems to be a very popular swap for the budget minded IDI guys, and we are seeing exactly what the turbo is capable of on an IDI. Right now it looks like its limited, at least in stockish form, to about 200whp on an IDI.

Im just curious what would be the best route to go on the turbine housing... Leave the 12cm on and back the actuator preload off? Drop a 14cm wg housing on and mod the gate like this 12cm, or just jump up to a 16cm NWG housing?

 

[SuperSonic]

If you don't loosen up that turbine housing with that bigger wheel it is going to surge like a mother. I would think you would be better off with at least a 16 on that 7.3 the idi's don't like a bunch of drive pressure and can't hold up to a ton of boost at 21-1.

 

[RacinNdrummin]

If you don't loosen up that turbine housing with that bigger wheel it is going to surge like a mother. I would think you would be better off with at least a 16 on that 7.3 the idi's don't like a bunch of drive pressure and can't hold up to a ton of boost at 21-1.

Yeah, that's definitely the idea here, I just didn't know which would be the "Best" way to loosen up the turbine housing. I personally was thinking the 16cm myself, but the owner of the truck was thinking 14cm gated.

As far as boost and drive pressure goes, best power was made at 17bp/35dp, which is complete garbage.

7.3 IDI's don't have an issue of taking boost as long as you can hold the heads down. Ive personally run up to 34psi on 21.5:1 for about 20k, until I built my new engine, but the studs were cranked to 150ft/lbs... It was enough for 759ft/lbs@2100 at the wheels nonetheless, with about 150cc of fuel.

This truck has a good foundation, 20k on a rebuild, Girdled, Studs@150ft/lbs, and the Turbo kit in the IDI fab thread, the bottleneck right now is just this turbo. As of this morning, we are looking at just dropping the HX and dropping a 366 on it. We could throw a bunch of money at the HX, which is counterproductive to the point of testing it in the first place... I think the HX35 is just a 200hp turbo on an IDI unless you want to invest some cash on it.