I have been back and forth on the rear mount/front mount option.

Now I have decided that the rear mount has too many points of failure(IMO).

I am thinking of using a smallish 60-1 Garrett with fairly high turbine a/r 1.15 for egt control. My motor is a 6.8l v10 and I want to use it for towing and performance in the 2000-4000 rpm range.

I used the Squirrel performance calc and it put the 60-1 as fairly efficient in the 2-4000 rpm range. The best efficiency across the board was the GT4088, but I am afraid of too much lag. The 4088 has a 64mm ind and an 88mm exd. for a trim of 50. The 60-1 has a 59mm inducer(from what I can find)

Am I correct in my assumption that a smaller compressor and a higher turbine a/r should offset egt's and provide lowend boost considering my engine is fairly large at 415 ci?

Also I plan on installing a used powerstoke intercooler. They bolt right up!

Oh, yeah I am one hell of a tig welder/fabricator.

 

sounds like a fun project. no turbo expert here but your line of thinking seems resonable to me. keeping the egt's down with a high ar should keep the motor happy for longer but would increase lag some. with a large motor it might not be too bad.

if your goal is for towing the lag wont be an issue. the load comes on gradual and the boost will just come up when you need the power. my set up is very laggy when hiting it from a stop but on the road towing the boost comes up effortlessly when needed.

 

Parish

if your goal is for towing the lag wont be an issue. the load comes on gradual and the boost will just come up when you need the power. my set up is very laggy when hiting it from a stop but on the road towing the boost comes up effortlessly when needed.[/QUOTE]


That is exactly what I wanted to hear!!! I didn't know how much lag would come into play while underway. Stop light to stop light is not my goal. The truck moves around town pretty good as it is. Just doesn't have the torque in O/D with a load like my diesel did.

 

Ive been through a lot with my truck becasue I tow a lot also. I tried the 1.15 Turbine on my 60-1 and it did lower my egt's about 100 deg under normal driving conditions. This is what I found the problem to be. There was definately more lag with the bigger turbine so in order to get into boost and have power to pull the steel hills I had to run a higher RPM which in turn raised my EGT's a lot. I found that runnibg a .96 Turbine it would spool sooner with less throttle and give me the same pulling power with less RPM and EGT's. The tune is a big part also. Allen Nelson worked with me to the tune of 12 PCMs before we got it right.

I just recently switched to a GT67 with the .96 A\R and am very happy with the towing abilities. I would also suggest water injection as this made a huge difference also. I pull some very big grades (Donner, Shasta etc.) pulling approx. 11,500 pound toy hauler loaded all the time.

 

I would consider a larger compressor....

My tow rig is a 393 ci motor with a 1.30 turbine A/R Q-trim T76.

 

Ya, but your "tow" rig runs 11's

I think a T60, maybe a 67 is about right for a tow rig, but agree that you would like the .96 A/R better. I dropped all the way to a .69 with my 60 and love it! With intercooler it will support close to 500 rwhp. I think to many people build for top HP and not where they will use it most. Personally, I like a setup that is fun for everyday driving over a lagy, more race/max Hp setup.

 

Dont I need a higher A/R turbine for a front mount compared to a rear mount?

 

you could run a low ar and have quicker spool but a little more back presure(heat) or you could run a higher ar and have slower spool but less back presure(heat).

i agree with your initial thoughts that a higher ar will be good for a tow rig. the boost wont come on instantly, it wont come on till you actualy need it and it should keep the manifolds and exhaust valves a little cooler.

1.15 might be a bit much. not really sure what would be ideal.

 

It's a big motor, they like to breath, I certainly wouldn't throttle it at the turbine for the sake of spool.

Trust me, with a load on, the turbo is going to spool anywhere you ask it to. Poke the throttle, air flow goes up, load is very high... it'll spin right up.

Also, big motors make lots of power at low PRs. The smaller turbos generally don't really get efficient until the PR is fairly high.

I'd go with something T70 or larger with a .96 AR minimum to start. But it's also easy for me to spend your money!

 

thanks guys

i looked at the compressor map for the T68 or 68-1 or whatever it is. It is very efficient in the 1.6 pr range. Looks to be my best bet. I will likely try a 1.06 a/r first.