I have talked to James about this before, but I still think I want to try the .84 with the KC38r 66/73. I am never above 2800 rpm, and rarely above 2600. I want some better spool characteristics and street manners. I have 238/80. Thoughts?

 

I'd be interested in seeing that graph with my 180/30's and my T500 HPOP, if it makes a difference or not.

 

If you rarely see over 2800 therei no point in a 66 cmpressor side, in my mind a 63/73 would match better.
How do you use the truck, what gears/tire size?

 

I completely get your point... and have argued the same thing to my team from both view points. But from a customer/business stand point we will never get rid of the stages. We have tried just listing sizes and 95% of customers want to know what "stage" it is.

Not everyone has the same level of knowledge, and we try to cater to as many people as possible.

95% of people just want this info
Stage 1 - tow
stage 2 - street
stage 3 - race

When presented with these numbers... 95% of our customers don't know what they mean and end up getting confused. Even with pictures and diagrams.
63/68/.84
63/73/.84
66/73/1.0

So we try to include all info to cater to both types of people.

 

I don't like to post up blanket "recommendations" like I did earlier because there is always a variance. This is a great example.

If you NEVER go above 2600 rpms then you will NEVER see the benefits of a larger turbo. I don't have your exact example handy... but this dyno graph below will relay the same basic info.
t4 s364.5 vs s369 with 205/30s. If you look at the graph you will see that the smaller s364.5 spool ups sooner, makes more power down low. At 2000rpms it makes 100hp and 300ft/lbs of torque more over the s369. That means it will tow better, accelerate quicker from a stop, less smoke, cooler egts, etc. You won't start to see any benefits from the larger turbo until you get over 2600rpms.

 

what would be the differences in performance between the t4 sxe’s and the kc drop ins? What would be the advantages of going with the t4? The drop ins are cheaper and have the same sizing besides the 0.91 A/R housing?

 

t4 kits are great. Everybody loves them... basically no downside except for the price tag. If you manage to sell off all your own stuff and find used prices on a t4 kit it is not as bad. But to just call up and order a new t4 kit with nice sxe turbo and all boots required typically run about $2500-$3000 depending on whose kit and what turbos.

The bigger you go, the bigger advantages you will see out of a t4 setup.

Also with a t4 setup you do get more options... but I would also like to point out they should not be called "t4 kits". Because that confuses people and think that a t4 kit will run any t4 turbo. But that is not true. In fact the stock OBS turbos are already t4 turbos... so to t4 swap an OBS does not even make sense at all. They should be called "s300 kit" or "s400 kit" or "Garrett/precision kit" because those are all different kits.

But back to your original question... the KC drop in turbos have come a long way over the past few years. Sub 500hp the t4 kit still has a slight edge in spool up, but size for size tend to make similar power. As you go above 500hp you will really start to see bigger and bigger advantages out of a t4 s300 or s400 setup.

Hope that helps without sounding too bias

 

I have 3.73 gears and 35's. Used to have 37's. KC did not have the smaller size turbo when I got this one. Truck is just a daily driver with some minor towing a few times a year. If I ever opt to go to a T4 kit, I am fairly compelled to go with a 364.5.

 

a side by side dyno comparison of t4 set up and similar kc would be awesome. If they get similar performance in lower hp applications, maybe the lower cost would be huge for marketing. I feel like most people that daily drive and tow aren’t looking for something in the 500hp+range

 

I am willing sell my t4, 363/68 .91 custom intake pipe, s&b intake and cncfab 4 line feed(for t4) with bowl delete. Then I can instll a 63/68 .84 and do a direct comparison.
I actually had emailed Charlie earlier to see if we could work something out

 

I agree with this statement 100%. I switched from a MST to a Carson Stauffer Diesel T4 kit with a Borg Warner 364.5/74/.91 SX-E turbo in late 2018 and earlier this year swapped in a 363/68/.91 SX-E. My initial T4 kit install was well before the current line up of KC Turbos was available. I have zero regrets as the SX-E turbo has been flawless since day one, but I am sure I would have tried the KC Turbos 63/68/.84 if it had been available.

I have 266,000 mile AD injectors and when they start to die, I will swap in Bitterroot Diesel remanufactured AD injectors. So, I am well below 500 HP and have zero intentions of going anywhere near 500 HP. My truck is a tow pig built around the task of long distance heavy towing. We make the choices we make based on what we have learned and what we have available to us.

A good family friend of mine recently installed a KC Turbo 63/68/.84 and has nothing but good things to say about it. Even towing a skid steer and a heavy trailer through the mountains of north GA.

 

Something I failed to mention, I have PMR’s. Do you guys think 205/30s would be pushing it?

 

No, 205/30 will be fine on a pmr.