Baja

From the looks of it, I run on the high side (8-10) compared to most of the responses. To me, it seems that my engine is not very efficient, I use more power to achieve the same results, 70mph. This means I get less mileage, and more cab noise, both of which I would like to improve. I have a 4" turbo back exhaust, modified exhaust manifold, and stock air box, which should be OK as far as air is concerned. My other bombs are quite mild compared to others who responded, yet they (you) still run less boost. My question is how can I make my engine more efficient? Could there be something wrong, or incorrectly adjusted? Is there something I can check? I have always pulled 8-10 since I bought the truck, and after all the changes I have made to the engine, along with filters and valve adjustments, the boost has always been the same. The WVO makes no difference. I still ran 8-10 before I made the change. Thanks in advance.

Andy505

Mine can very from 5-10 psi going 70...depending on if I am going up hill or downhill. Going through a headwind or tailwind...it just depends. It seems though that most of the high numbers, including yours and mine came from 4x4 trucks. I'm not too familiar with what differences the 12v engine would have in boost, but I'd say your numbers are good. I wouldn't be too concerned about them.

88bird

could it be that you run on WVO? i heard it isn't as "efficient" as diesel... maybe that's why you see more boost than others... mine see's anywhere from ~1psi to 20psi as stated above... load makes a big difference.... hills winds etc....

Baja

In my first post, I used level ground and no wind as my benchmark. I know that terrain, load and wind all have a huge factor. I also mentioned that my boost has never changed since I got the truck, and that includes the addidtion of WVO. When I switch to that stuff, there is no change in performance at all. I wonder if injectors can make a difference or oil. I plan on trying amsoil my next change, give it a try.

infidel

Have you checked the timing?

ellerman

Have you compared tire size to the guys that you are comparing your boost numbers against? If you have bigger tires this would effect the load on your engine at speed. Eric

Lil Dog

If you are seeing lower numbers from other with aftermarket turbos or even different exhaust housings, the boost will be different. Just adding a 16cm2 housing will drop your cruising boost by about 4 psi, but you will run hotter.

Efficiency has alot to do with flow, but just lowering your boost is not making it more efficient on the highway unless you are gonna change the way exhaust flows out of the engine as well.

Mine at 70 MPH is in the 7-9 range on flat ground.

caffecapri

Just for comparison, unloaded and flat highway, I run 5 lbs of boost at 70 mph (around 2100 RPM, 700 EGT, 3.55 rear end).

Pulling, I run 10 lbs on the same flat highway.

Baja

Interesting post on the exhaust housing. How much more heat will the 16cm2 housing cause? I can handle more heat, as I do not tow anything. How will it change the torque curve? Correct me if I am wrong here, but as I understand it, the more boost the engine is pulling, but more fuel it is using. Can you have high boost, but little fuel useage? As far as exhaust goes, I have a 4" turbo back, and a ported, gasket matched manifold, stock air filter box. I think my air is OK for my mods. Tires are 285x75x16, not large at all, 3.54 gears. Caffecapri is 2wd, so he is not pushing nearly as much air as I am, so his boost will be lower, My friends 2wd also pulls 5. I have had the IP timing changed, but the "mechanic" who did the work did it all by guess, so I really don't know. The truck does run better,no doubt, but there is no change in boost @70 from before his timing work. This guy is perfect for "if you want the work done correctly, do it yourself". I plan on doing that. I guess that I am looking for changes I can make make so it is easier to run long trips on the highway.

Lil Dog

The exhaust housing is what I refer to with exhaust getting out of the engine. That is the highest restriction point leaving the engine. If you are running about 10 psi boost pressure you are probably running around 10 psi PTIP (pre turbo inlet pressure) on the exhaust manifold side of the turbo, irregardless of stacks, pipes, mufflers etc.

The air flow through the engine is at higher pressure with the stock 35 and 12cm2 housing. IF you put on a 16 lets say, you now drop your PTIP by 4 or 5 psi at the same conditions, but your boost is also lower at those same conditions by 4 or 5 psi.

Boost on the engine is entirely up to the turbocharger to provide. Typically if you have more boost you are using more fuel because with the stock system setup, you have to have X exhaust flow to provide Y boost. You add more fuel to the combustion and your exhaust flow increases, result, more boost from the compressor side. However you can add more fuel and change the turbo and have the same boost. IE. someone with an hx35 running 36 psi would be burning less fuel (less power) than another with a 40-16 combo running 35 psi boost. Its a tough balance.

Fuel economy, if thats the targets is more affected by timing and operating the engine in its sweet spot for efficiency being RPM related.