Started playing with the wastegate...

[JeepSJ]

Wow. What a difference. I was getting a little frustrated because I could not get much, if any, boost at low RPM, and I really had to stand on it and let it rev to get more than about 5psi. I thought that I was still advanced on the timing, because it snaps to life when cold, even with no cold advance hooked up. Retarding the timing was helping boost a little, but EGTs started climbing. I was thinking that maybe the vehicle was just too light and just could not load things enough to get it to boost.

I noticed last weekend that there was a lot of room left for adjusting the wastegate, so I gave it a couple turns and took it for a spin. I liked what I saw. So, I have been cranking it down a little at a time and it is running like a totally different engine.

I now see boost at low rpm, and just a little throttle gets the boost to come on. I also have sustained boost as low as 50mph (about 1/2psi), whereas I would not see boost at cruise until >70mph before the adjustment. At 70 I'm now seeing 2+psi, and EGT is down slightly. In fact, EGTs are down overall. I also had an issue where boost would fall to 0 when it shifted, and that is no longer the case.

I have more playing to do, but overall I am extremely happy with the results.

[ccatlett1984]

keep cranking that down, you should be seeing more boost than that. BTW what are your cruising EGT's?

[Robyn]

The cruising boost on my dually is about 4-5 PSI and the EGT is about 400-500 at 60 MPH
from there in OD the boost will climb to about 13-14 PSI at around 800F

You should be able to get a sustained boost of at least 3-4 PSI going down the road.

[JeepSJ]

Well, just got back from a little road trip. Drove from Phoenix out to Lucerne Valley (high desert in CA) to help the team do some testing of our desert racer.

70mph, sustained 2psi, egt just below 500. 80mph, 3.5psi, 600egt. There are a couple good grades, and I wanted to see just how far I could push it. Hwy 62 from Palm Springs up to Yucca Valley - about 107* for a nice 20 mile climb. There is one very steep and twisty section and I could keep it at just over 70mph, egt climbed to 1000 and stayed there even when I totally mashed the pedal, and coolant temp never went over about 210. Boost was 5-6psi. Interesting thing - when I came down that grade today, my coolant temp went down to about 165. One of my tstats must be stuck open.

Also on the way home was the grade on I-10 coming out of Indio. Crusing up that at 75+ was no problem, again with 5-6psi and EGT about 850 and coolant temp at 195. I again decided to see how far I could push it and eased into the throttle and she accellerated, and at just about full throttle it downshifted into 3rd and boost jumped to 11psi and the thing pinned me into my seat. When it shifted into 4th again I looked down and the needle was over 100mph. EGT never went over 1000, and coolant temp stayed below 200.

High gear I cannot get it over 7psi. There is some adjustment left on the wastegate.

I also pulled the best mpg yet, at just over 24mpg and that was pushing it at 75-80 the entire time.

[JohnC]

If your full throttle EGT's are under control then you will not benefit from more boost. In fact, all you'll get is more backpressure. What you need is more fuel... ;)

[JeepSJ]

Yes, I think it is time to start playing with the fuel now. I'm thinking 1/8 turn of the screw and see where that gets me. Before I played with the wastegate I would get a little smoke when I got on it at low RPM, and now that smoke is gone.

And as for my sustained boost at cruise, remember that I am in something that is smaller and lighter than a Suburban or 3/4-1 ton truck, so I'm not working it as hard so I won't generate the sustained boost of a heavier vehicle. Theoretically.