Alright 7.3 powerstroke t4 guys, you asked we answered. We have been doing a lot of testing lately. Well we have a lot of data to report. I don't want to post up too much and make it a mess. But I don't want to leave anything out. I will display the info in a couple of different ways.
Irate t4 with s369/73/.91 vs s364.5/73/.91
I know this is the one a lot of guys were excited for. I can tell you the graphs 100% backed up exactly what we noticed on the streets and towing.
For daily driving the s369 was a little lazy down low. It did not lack fuel down low at all and could be smokey at times. But the mid range and top end was a blast. It cleaned up those 205/30s to nothing once you got the turbo spooled.
Towing light the 369 did great and easily kept egts in check, but if you towed heavy and in high elevation the s369 was a NIGHTMARE! We would have to downshift into 2nd gear sometimes just to try and stay on top of the turbo. It would often shift and snuff out the turbo when rpms dropped. One time he even had to drop down into 1st gear just to keep going. Oil temps got really high also, often topping 250 on grades he has never had issues with. We were at UCC when James got the call from Zac after the first time he tried towing heavy in high elevation... I think his exact words were "I want this F**king POS off my truck right now" Zac uses his truck as a tow truck for a living.
The s364.5 spooled much better for the streets. It did not have quite the top end power of the s369 but was much easier to drive around with less smoke.
Towing the s364.5 did awesome. Just as good if not better than the BASB we had on before. Egts were almost never an issue unless lugging the motor in OD. Towed great light/heavy and in all scenarios. Where we would have to downshift into 1st or 2nd with the 369, the 364.5 would pull in 3rd or 4th with lower egts and oil temps. IMO this is the ticket for middle of the road guys who want great power and good towing.
Here is the dyno graph: It backs up exactly what we experienced.
On the top end the 369 did make 15-20hp more
But the s364.5 made 36tq more and made it 260rpms sooner (2280 vs 2440)
But as you move lower in the rpms it becomes even more impressive. The farther down in the rpms the better the s364.5 did. At 1900rpms the s364.5 made about 100hp and 300tq more than the 369.
Keep in mind this testing was done on an ALL OUT race tune. On a tow tune there is not enough fuel for the s369 to make any more power than the s364.5. Those 30% nozzles need a LOT of PW to make decent power. Most tuners won't even write more than a 4.2ms tune... but you can gain upwards of 100hp on a 5.6ms tune. Something to keep in mind.
Personal opinion... anything bigger than an s364.5 on 205/30% or smaller is a waste. You gain about 200-300rpms of lag and lose a ton of towing ability to gain a little top end power and only on an ALL OUT race tune (which most tuners won't even write for you unless you specially request it).