Need turbo advice: Detroit 12.7 s60

I did the 171702 and the Full Tilt. All else is stock, apart from 550/2150 tune.

I’d advise the manifold - while you’re in there, and it’s worth it. Call it your early birthday present.

 

The 701 has a wastegate, it is a good replacement for the original garret Brand new,It’s cheaper than a reman garret. The 702 is the same turbo, except without a wastegate. I’ve got the 702 on a stock 12.7. I’ve had 2- 701’s on the same engine, in the past. The difference is with a wastegate, it will spoil up faster, especially in lower gears, while getting up to speed. The non wastegate 702 is said to have a lag, compared to the 701. I see no difference at all. The 702 seems to do a better job. Higher egt from a 702 can crack the exhaust manifold. Need to watch the egt. A pyrometer is suggested. I haven’t hooked up my new pyrometer yet. I just noticed my manifold leaking a bit at one slip joint. I imagine it’s from the extra exaust gas temps. Bottom line,, 702 seems to have more overall power, and higher boost. Just have to watch egt on long pulls, especially at lower RPMs. That’s all I know. Still learning.

 

I got one with a 171702, tune, injectors.
I got one with an 11 blade turbo from Leon, tune and same injectors as the first.

I’ll be changing out the 171702 (Been running it about 8 years) to an 11 blade in the near future. Way better down low, more air volume with less pressure.

 

Waste gated turbos open when there is more pressure than the engine can effectively use, they are more effective at lower rpm and tend to have a smaller housings than comparable non waste gated turbos, therefore they build more pressure at lower RPMs, and are less effective at higher RPM. I would likely be more inclined to run a wastegated turbo doing more local work. Nonwastegated turbo for more highway work.

Utilizing a larger turbo to produce more boost without matching injectors and a tune to the turbo would likely cause no increase in mpg or performance. A bigger turbo pushing more air into a motor, that cannot add enough fuel to be effective would cause no gain in performance, and i expect it would raise pyro temps somewhat.

171702 will build up to high 40’s for boost pressure. It loses efficiency beyond the early 30s however.
Stock garret is most efficent in the 20’s as i recall.



for fuel efficiency, 1750 is well beyond where i would want to be. I see my best mpg when i keep highway rpm about 1400 with as little boost as possible.

 

I think the pyro needs to stay at or below 1000 max. I always tried to keep it at or below 900 max. They say 900 with probe after turbo is equivalent to 1100 pre turbo manifold temp. I never got more than 28 or 29 lbs of boost from any of the 4 garret and 2 BG 701s I’ve had between 2 Trucks over 20 yrs.and over 2 mil miles. This 702 has been at 30 quite a bit. 32 also. Just came out of NC on 26 north, across 40 west through the Gorge, and up 75 north across Jellico. It was hitting 35 psi. First time I’ve seen it that high. Came up Jellico at 40 mph and 1500 rpm with 43k in the box. I’m pretty happy with it.

 

My last Truck had the computer read out. 1375 rpm was the best economy. Not letting it drop below that, as it would lose mpgs when picking it back up, unless I could do it little at a time, going down hill. I studied the instant readout extensively. With light loads, babying it up small hills, without dropping a gear, lugging it down as low as 1050, using a light foot, then gassing it a little bit at a time, downhill ,to pick up speed, and RPMs. I got crazy good economy. 8 or higher. It makes sense. Torque curve roughly 1350-1650. Realistically with 354 rears running 1500 RPMs, at 65 mph is perfect, right in the middle. Just running it normal, I’d get 6-6.5 overall. This Truck at best averages 6. More like 5.5.running heavy in hills. Just figured my average on 3000 miles at 4.9. It’s still breaking in. I’ll be happy with anything over 5.5. Hoping for 6+. I’ve yet to hook up my new pyrometer. Haven’t melted a piston yet. Lol. I don’t think it’s a big deal. Still breaking it in. Still can’t believe I hit 35 lbs boost last night, all the way up Jellico. Im sure gets got pretty high, at 1500 RPMs. Cac is also new.

 

I honestly don’t feel any Lag that some complain about with the 702. Could be because it ran so weak before the overhaul. Both my Detroit’s got excellent economy on flats, but drops quick in hills, especially if heavy. Seems to be better to just run it above 1500, even up to 1700, to get through the hills. Since mpg's drop anyway, wound up or Lugging. Anything under 1300, doesn’t do much. 1200 or less, up a hill, falls on its face.