T4 VS KC Gen 3 RESULTS

2001 7.3 with full built motor, ported heads, cam, piston work, headers, 238cc/80%, and s364.5/73/.91. We got the truck in and was worried it might be an injector issue or maybe mismatched size because they just seemed to flow too much down low, but made awesome top end power. We sent the injectors to Nate @ Unlimited Diesel and he flow benched them and verified the size and that nothing was wrong. When we got them back we spent a lot of time on tuning, checking for boost/exhaust leaks, driving the truck around on and off the dyno. We were not sure if the ported heads/cam/pistons could because issues and was not ready (did not want to?) to tear into the motor.

We decided to try some turbo options, the t4 setup always fit a little weird, was leaking oil, and the downpipe was causing a huge leak we couldn’t seem to get right… so we decided to take this time to do some back to back testing.

Same tune, just swapped turbos. See dyno pic below for results.

KC s1 – 563hp and 1281tq

If you look at the dyno graphs you can see the s364.5 carried the HP a little better on top, but came on much later and made less peak tq. The KC s2 spooled about 100-200rpms sooner, KC s1 spooled 200-300rpms sooner. I honestly could not tell a difference in top end power on the street but the spool up was super obvious. The s1 cleaned up all the low end smoke and we were able to make the tune a little more aggressive down low to bring on the power sooner without crazy smoke like before with the T4 turbo installed.

Matt’s goals for the truck were aimed at quick spool up, low smoke, and he said his goal was to only make 500hp, but wanted it to be super clean. So he decided to keep the KC s1 gen3 turbo on his truck and pull some fuel on the top end to bring the HP down.

Would an s364.5/68 have spooled faster? for sure but would have also lost top end power?

Does this mean everyone with a t4 kit should swap back to drop in turbo. NO WAY. T4 kits are great and have great turbo options and can go much larger. They have some weird quicks with oil drains/feed and boots blowing off, and some guys prefer the OEM fitment look (especially in emissions states) but I am not advertising that people should un-t4 swap their trucks.

For a little deeper dive into the turbo data we found interesting. The s364.5 ran very “efficiently” when it came to boost/ebp ratios. It was very impressive. But it was also laggy? So efficiency isn’t everything

IMO, it comes down to what you want. Most customers we deal with care most about quick spooling and that was the biggest goal with the new gen 3 turbos. Here is an example of what I am talking about. At 1900 rpms we saw the biggest variance in HP/tq/boost/ebp/etc. So here is just a screen shot of that data

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1900rpms 85% load, 3rd gear

20 boost

16 ebp

22 boost

22 ebp

27 boost

28 ebp

We have had customers ask us why we don’t release compressor maps or sizing for our most recent lineup of turbos. They have even gone so far as to threaten to not buy one until they see this data. The real reason we don’t want to post this information is that the all new kc300x Gen 3 is so vastly different from any turbo on the market for the 7.3 powerstroke that these numbers would only confuse the market and we often get copied by people who simply read specs off of our website. What we want to offer is much more valuable and this comes in the shape of towing tests, boost numbers, spool up times, injectors sizing to pair with our turbos and dyno graphs. The most important part of your truck is its drivability. A turbocharger’s compressor map doesn’t have as large of an impact on driving, towing, and spool up than what we want to showcase with this data. By providing data with injectors sizes, tuning options, how they tow, how they spool, how they drive, etc, we are striving to bring you the most complete understanding on how these turbos perform. It is simply impossible to get any of that data from compressor map.

To drive that point home. In a 6.0 or 7.3 making 550hp s363/68 is going to tow better, spool faster, and make more power than an s363/73 even though they share the same compressor map. Also the s363/68 will outperform the new s364r/73 even though its more efficient and has a wider compressor map. Turbine wheel and turbine housing size matters, application matters, efficiency of the motor matters. Injector size and tuning matters, how you are actually able to spool up the turbo and use the power matters WAY MORE than efficiency islands on a compressor map. You just can’t get that info from maps and reading wheel sizes, it takes real world experience and that is what we actually do provide.

The info we give about towing, injector sizing, dyno graphs, and recommended tuning is literally GOLD! Its where the rubber actually meets the road in real life, nothing is better than that. Passing on REALLY WORLD application data for theoretical efficiency islands maps is NUTS!