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  • Writer's pictureWinfield (Goose)

Updated High Pressure Fuel pump and full E85 tuning!

I want to update the site on working with full ethanol and the new XDI High Pressure Fuel Pump. XDI has two versions of the fuel pump; the 35% more capacity, 200bar/2900psi and the 60% more capacity, 250bar / 3625psi. $1599/$2499 respectively. In this writeup we are going to focus on the 35% pump. We are now a dealer for this pump so should you want to purchase one please feel free to ask, no more blending down to E50!!

A buddy Travis installed this pump on his truck in about 30-45min, super easy and very quick! This pump DOES require custom tuning so that will need to be considered as well. This calibration was done with the COBB Tuning Pro Software and the COBB Accessport.

What we saw right off the bat was a big bump in fuel pressure at 70% ethanol. Where the HPFP system would fall off and drive short term trims very lean, the short term trims were well in check (even negative meaning plenty of fuel availability!). As we bumped ethanol content up towards 80-85% we noticed short term trims come up closer to 0. At this point the low pressure pump started falling off, from 75psi down to 48-50psi. That meant the in tank fuel pump needed a boost. Travis decided on the Boost a Pump which was another easy installation. After that was installed low pressure no longer dipped, at all. Solid 75psi across the whole pull!

What we noticed at high ethanol content (82-85%) was high pressure started to fall off ‘slightly’ around 5000rpm but picking back up at 5500rpm. We will look into more in to this here soon but with fuel trims solid and Air-Fuel Ratio spot on it seems to be a non-issue. On to the fun stuff, Power and gains!

So first off, there is no baseline data for this dyno. In the hundreds of trucks I’ve tune and the final number Travis and I came to, I’d imagine a stock baseline on this dyno would be in the 310-320whp area. Travis and I have been logging for months, back and forth on 91 as well as ethanol so his truck was 90% of the way there after hopping on the dyno.

First pull out was 472whp and 511wtq. This could be improved...

One thing I’ve been wanting to do, data wise, is show “lower boost” levels vs “high boost” levels. That topic is overly discussed with 0 data. So lets talk about it and look at real data behind the words. 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'. Lets set aside the fact that I've run this boost level for over 40,000 miles on my test truck.

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 map bottom charge air temps at 83.3* while the higher boost map bottoms out at 88* at the same RPM, so a 4.7* 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*.

SO…as you can see, a 4psi bump in boost pressure basically bumped charge temps up 4*. I’ll let you guys decide if that added “heat” was worth the huge gains I’ll explain next!!

Power onset: Looking at the red line (low 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. I will 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 bump boost back down to 20-21psi which is what we did.

The truck ended at a very very solid 485whp 538wtq. We didn’t let the truck cool much after the runs so it would’ve probably hit 500whp in just letting it cool down, but it didn’t so we cant say it happened :D This is still a very very solid truck! Glad we were able to collect some good data from this experience! Thanks for reading!

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