(Gen 2 Raptor) Boost - Myths and Truths
I pulled this data from my other blog. Boost levels have been a topic of conversation in the Gen 2 Raptor scene for a while. One thing I’ve been wanting to do, data wise, is show “lower boost” levels vs “high boost” levels. This topic is overly discussed with 0 data. So lets talk about it and look at real data behind the words. I had the opportunity to test boost levels, and compare some data. The high boost map had a peak of 21psi that some say is ‘too much boost that can over heat the truck cause issues with the smaller turbos, over-spinning them'. Lets set aside the fact that I've run this boost level for over 40,000 miles on my R&D Raptor.
One of the most important things to consider is Charge air temp. Looking at the charge air temperatures below you see that 17.8psi sits at a charge air temp of 91*, while 21psi sits at 93.2*. So a difference of 2.2 degrees. As we progress thru the pull you see the lower boost tune bottom charge air temp is at 83.3* while the higher boost tune bottoms out at 88* at the same RPM, so a 4.7 degree difference. Peak charge air temps are 87.5* for the low boost map, and 92.3* for the high boost map: a difference of 4.8 degrees.
(Red line is "high boost, 21psi. Blue line is "low boost, 17.8psi) So…as you can see, a 4psi bump in boost pressure basically bumped charge temps up 4 degrees. I’ll let you guys decide if that added “heat” was worth the huge gains I’ll explain next!!
Power onset - High boost vs Low boost
Looking at the Blue line (high boost) you can see a HUGE gain in torque as well as power from 3500rpm to redline. Now while the peak power numbers are close up top, the higher boost map will get off the line MUCH sooner as well as pull away from the lower boost map a lot quicker. There is almost a 500rpm response difference. Low boost doesn’t make 400whp until 4500rpm while the higher boost map makes it at 4000rpm! Low boost makes 450whp at 5400rpm while the high boost map makes 450whp at 4600rpm! That’s a big big deal for those who daily/street/race their trucks. So now you ask the feared question, does 18psi vs 21psi make that big of a difference in heatsoak? To me, the answer is a very clear NO! A 4-5 degree drop in charge air temperatures are NOT worth a loss in power and torque from running 17.8psi vs 21psi. The MUCH quicker and faster truck will run more boost pressure, period! I will also say that this particular truck made 20-30 more torque with 2.5psi more (22.xpsi) pressure, but no more power. Would that be worth it? Not to me, I’d lower boost back down to 20-21psi which is what we did. TLDR; Higher boost nets MUCH quicker power/torque onset with almost no effect to charge air temperatures! Lower boost leaves a significant amount of power/torque on the table. While 'lower' boost is very conservative, you will get left behind by a 'higher' boost truck. Thanks for reading!