Twins (Compounds) Build!

[PToombs]

Update, since I've been driving it some. The big turbo doesn't seem to light until I get up to about 2200 rpms, but when it does, we're leaving in a big hurry! It runs about the same on the bottom end. After the 471 spools up it accelerates faster than before, and I think EGT's are way down on the top end. It's hard to tell, too many gauges to watch at once!

Any tricks to getting it to light sooner? Do I need to turn the fuel screw back in? Any other words of wisdom for me?

And FYI, the trans is rattling a little again.

[cmann250]

Any tricks to getting it to light sooner? Do I need to turn the fuel screw back in? Any other words of wisdom for me?

Do you have adjustable gates on both chargers? It seems that after boost leaks, waste gates are the biggest issue with twins.

[Sutter1stgen]

I know I set my gate to open at 20psi for my hx35. This helped it spool a little quicker, and had me at a higher boost level, and the truck ran free'r if that makes sense. Letting your secondary open a little sooner may help.

What is the exact spec of that s471???

[PToombs]

Caleb, it only has a gate on the S300.
Sutter, I'm not sure how to adjust it to open sooner. If I shorten the rod off any more it will pull the gate open, longer will take away gate travel and it won't open all the way. Does that make sense?
Pretty sure it's this one, http://www.himni-racing.com/turbocharge ... t6-turbine

[Sutter1stgen]

Caleb, it only has a gate on the S300.
Sutter, I'm not sure how to adjust it to open sooner. If I shorten the rod off any more it will pull the gate open, longer will take away gate travel and it won't open all the way. Does that make sense?
Pretty sure it's this one, http://www.himni-racing.com/turbocharge ... t6-turbine

Loosening or lengthening the wastegate rod should relieve spring tension, allowing the gate to open sooner. I know if you tighten them too much it will limit overall opening of said wastegate.

As for the turbine wheel size, and housing size, I'd say that spool up is about right. But I think with some more tuning it will improve a little bit.
Oh, and have you turned your fuel screw in more yet?? Adding more fuel could help drive the primary harder, sooner as well.

[PToombs]

Ok, I'll eyeball that rod again and try adjusting it more. I didn't really want to dump more fuel back in yet, but I can easy enough.

[AHineman]

Any updates?

[ellis93]

Na....it's probably the same....choking,puking,spitting,and sputtering

[AHineman]

Truck or owner?

[PToombs]

Owner! I drove it a few days last week, didn't adjust anything yet. The trans is rattling like a SOB again in neutral, I need to pull a PTO cover and see how much play is on the counter shaft again. I wish I had the money to upgrade to a different trans, but on the bright side I can have it out in about 30-40 minutes now. I'm real glad it's not a 4X4 with a transfer case.

[AHineman]

Time for a sig change Pete. Green 2wd trucks with flatbeds and twins....

[PToombs]

A small update! After driving the truck since mid-summer, I finally made a small adjustment. I went and picked up a fuel sump from a friend of mine and we were talking about the big turbo lighting and how to change it. Everybody talks about shortening or lengthening the wastegate rod. I didn't think that would help as to when the wastegate opens, and after talking to him I made the connection I was missing. The spring controls when, as in, how much boost it takes to open the gate, adjusting the rod only controls how much it opens. So the thing to do is change the spring rate, right? I took a small spring, put it on a pull scale and saw it is about a 10 lb spring. I put it on the actuator rod so it pulled the gate open, countering 10psi of boost. I took it for it's probably final ride today to fill it with fuel before I park it for the winter. Boost was about 25psi when the big turbo started pushing, usually it's 35-37 before it starts moving the gauge. It seemed to hit down lower in the rpm band than it did before too. It started to rain as I was on the way home, so testing was over as I had my son with me and a ditch ride sucks. I'll resume playing with it when I get back out in the spring, but I think it made a noticeable difference.

[Tacoclaw]

The different rod length puts a different preload on the spring, the shorter it gets the farther down the spring is squeezed. Just like our AFC springs, the looser they are the earlier they start moving.

[PToombs]

So the spring is a progressive in there? I thought they were a regular, even rate spring. No matter, my fix works, and it seems pretty good too! In the spring I may make a bracket for the extra spring, and play with different ones to see what happens.

[RCCUMMINS89]

If you compress a regular spring it does the same thing as putting in a different rate.....just like our afc springs.