Low speed/high torque turbo propane application

[metalz]

Hello all

I am having some difficulty deciding which turbo would fit my needs/wants which I will list:

- 300 six
- propane fuel
- aftercooled
- 14 p.s.i. maximum
- 6400 lbs. vehicle weight
- 4 & 2 trans. with overdrive, shift points 500 r.p.m. apart
- 1900-2200 r.p.m. @ cruise speed
- engine operating speed 800 r.p.m. to 3200 r.p.m. (usually less)
- 4000 r.p.m. (or less) MAX.
- shift points usually 2500 r.p.m. or less
- low speed torque most important
- boost to start as low as practical
- max. boost available by 2400 r.p.m.
- general transportaion and towing application
- altitude 3500 ft.
- climate temperature -40 to +100 degrees F
- turbo with integral wastegate

I have used the Ray Hall calculator and have come up with the T3 50, T3 60 or T3 Super 60. Also working through the books "Maximum Boost" and "Turbochargers". I would like to discuss this application with someone who has experience with this low speed, high torque application. Most everyone I have talked to locally has experience with higher r.p.m., high horsepower applications. The TO4B that Ak Miller used
seems to be too large when applied to my specs when using the Ray Hall calculator. As such, I would very much like to hear your experiences and advice.

Thank you in advance for any assistance
MetalZ

 

[Lazy JW]

I have zero experience with turbos but that combination sounds about ideal for a heavy truck like my White Ox. I like it.
Joe

 

[xctasy]

I have used the Ray Hall calculator and have come up with the T3 50, T3 60 or T3 Super 60.

The T3 60 is the one to have.

Use it and you'll be happy. Its okay to 270 hp, about where a 2-bbl Impco CA 225, CA300, or CA 425 carb will work to.

Get an TransAdapt adaptor so you can fit the Impco carb to your truck. Or an Offy 2-bbl intake, and run the stock exhast manifold with a J-tube adaptor. The blow through an Isuzu FZR truck intercoller, and then run it into a cast alloy or specailly made turbo hat. Don't use the Ak Millar TC-3 controller. The turbo will become the restriction, and everything else should tak care of itself.

Get a rebuilt engine with new pistons. 300's don't have very good pistons, so it won't like any more than a 9 to 12 pounds of boost. An intercooler will help, but the piston itself is not very strong.

 

[Anonymous]

- 14 p.s.i. maximum
- 6400 lbs. vehicle weight
- engine operating speed 800 r.p.m. to 3200 r.p.m. (usually less)
- shift points usually 2500 r.p.m. or less
- low speed torque most important
- boost to start as low as practical
- max. boost available by 2400 r.p.m.

You REALLY need a diesel.

Trying to get the engine tuned for what you are asking will be a challenge.
Good thing propane is forgiving.

 

[metalz]

Thanks guys. Does anyone else have any input?

 

[Lazy JW]

As I stated above I have no practical experience with turbos or propane for that matter. That said, I will try to apply a bit of common sense.

#1. Low speed torque requires a short duration cam.
#2. Short duration cams don't need or want lots of compression.
#3. A turbocharged engine is happy with a short duration cam.
#4. Propane has a favorable octane rating.
#5. A low compression engine under boost needs the octane.

The way I see this, a low compression torque motor like the one in my 81 F-150 would be a good candidate for what you are proposing.

I would suggest using a 300 carby head with all the usual prep work (porting, etc.) Use EFI hypereutectic pistons to lower the compression. Zero deck the block. Use a short duration cam like the Economaster 188º cam I am running from www.reedcams.com. Bolt up the induction system and tie the turbo into it. Have fun!

I hope someone else can help with the details but this should give a good, solid base to start with.
Joe