Before I start, I know that superchargers have better low rpm response. But they are also cost prohibitive for many builds and applications.
I have a 2000 silverado 2500. 6.0L
I regularly tow 10k lbs with it. I know that smaller turbos respond better to low rpm applications. But does anyone have experience with cruise speeds and what affect a small turbo has at say 2000 (or 2300 rpm out of overdrive) and partial throttle? Does it provide some additional power? Does it have a negative affect on torque at that speed due to backpressure? There are times when you come up on a slight grade, and being able to leave it in top gear for the time to get over the slight grade can make towing easier and with less drama.
I know the small turbos may sacrifice high rpm potential. But frankly, these kinds of trucks rarely see over 5500 rpm anyhow.
Any real world experience?

 

Oh, and understanding the difference between spool time, and where in the powerband boost can be made tells me that this application is less about spool time, and more about rpm range for SOME boost. Obviously the power does not need to come on suddenly, and there is no need for high boost numbers at low rpm (and that would be destructive anyhow.)

 

It all depends on the load on the engine. Making the boost come in very early can put a lot of stress on the rods and could choke the engine in higher rpms and high egts . Something in the 70mm range T4 turbo should work for you for towing

 

Sounds like GT35 size territory?

 

I don't that at any time on any engine has a turbocharger had a negative effect on torque, they are all about torque. Backpressure wouldn't occur until higher RPM, not at 2000 RPM.

And the higher the gear, the greater the load on the engine, and the sooner the turbo will spool.

Al

 

Id say more like a gt45 69mm or T70 range. T4 . Keep the hotside at 2" to keep
The exhaust moving fast.

 

Make sure to run a large enough down pipe use the 1.25x rule to keep the back pressure down and avoid chambered mufflers you'll want to run a straight thru turbo muffler if you wanna run one at all

 

Great info. Thank you guys!!

 

The tune is critical on something like this. Boost at low rpm, and at peak torque is tough on parts especially if you're spending extended amounts of time in boost.

 

I would also look at a S366 turbo. It has a large enough turbine, it's priced right, and it's a quality turbo.

 

Speaking of tune, what are the important tuning points of a build like this? For a typical gt45 size on a 6.0L application, is upgrading injectors and fuel pump/regulator needed? What is the most practical way to get the computer cooperating? What special low rpm considerations are there?

 

Injectors, and a fuel pump are typically what's needed, but ultimately depend on how far you plan to go boost, and rpm wise. The stock fpr works just fine. Hp tuners is what most use to tune the stock ecm. The stock ecm is complicated, and having a competent tuner may be the best thing if you're new to tuning. Managing cyl pressure at low rpm, and at peak torque is key, and is basically ign timing.

 

Thank you! That's what I was looking for. I don't need to get aggressive with boost. I know it is addictive. But I have a drag car for that urge.

 

A turbo setup typically needs a boost referenced fuel pressure regulator - to keep fuel pressure constant.

Al

 

The stock fpr is referenced to the intake, and works very well... many have used them.

 

I've built 100's of turbo kits for these truck and have towed heavy with my truck just like what you wanting to do. I would recommend a BW S475 in a t6 with a 1.10 a/r and the small 83mm turbine. That 6.0l need to breath and with load, it will have no problem building boost while towing through the hills. This is from personal experience, no just guessing btw.

 

Holy smokes this thread hit the newsletter!
Wow that's a lot of kits! Who do you make them for or where do you sell them? What have you done with the fuel system/ecu in your case for the towing vehicle?
Is there any significant difference between the overall performance of the BW vs the gt45's that are quite popular? Have you tested them? The cost difference is significant obviously.

 

Any drawbacks to going remote mount for towing applications? Spool time isn't the biggest consideration in this case.

 

I have a kB racing kit on mine and a 7875 on3 turbo. Lag is a non issue, it lights up very fast.

 

Look at the VSracing turbos for something more cost effective. Their 78/75 is pretty hard to beat for $400.

Adding constant load on a turbo like that will also generate lots of heat. Cooling systems gotta be up to snuff. A remote mount setup would be great in this application IMO. Keeps the heat out of the engine bay somewhat and is easier to install IMO. Keep factory manifolds and exhaust. Just route it into the turbo.