BigBully

Yep I looked today and its an 18.5 So which one would be better for me?

wannadiesel

The 18.5 isn't real bad, but it's a little big to make good boost. It really depends on what you use the truck for and what you want out of it. The smaller the housing, the faster it builds boost (and it builds more boost). This is good to a point, but a smaller housing is more restrictive at high RPM. Basically, if you're just playing in traffic like me, get a small housing (12 cm) and have fun. If you're towing heavy or you plan to make big HP, get the 16 cm for more boost with adequate breathing at high RPM. The 14 cm wastegated housing is a good compromise between lag and breathing, but it's real expensive. 12 cm wastegated housings are cheap because 2nd gen guys making over 300 hp swap 'em for 16's (which are getting kinda pricey, but not too bad yet). The 16 is the easiest swap because it's the same length as the 18.5 and 21, all the other sizes are 1 1/4" longer, which means some tweaking of the exhaust.

BigBully

Well at WOT empty im getting 32 to 33 pounds of boost and it gets it Right now, Alot faster then my Powerstroke and More then my Powerstroke, It only gets around 28 to 29 pounds.

Alec

I am pretty surprised that you can make that kind of pressure with an 18! But, it seems to me that the truck is set up just fine for you from how you describe it. You don't need any more boost, and if you went to a smaller housing for less lag, you would have too much trouble with surge.

BigBully

Ya I was really suprised it made that kind of boost and so fast.
I never really paid attention untill I took a friend for a real Ride ;D and thats what it was gettin, Even suprised him.

Redleg

HX35 by chance? I was wondering about going back to 18.5 with an hx35 or 40 after injectors. I don't need to drag race so much, but I don't like tying up the left lane when passing, not that I'm worried about anybody tailgating my flat bed and heavy duty bumper. Scratches give character, and I like a bumper with character.

BigBully

The truck has been down Due to a Clutch Problem that is now (I think) Takin care of. I still have this Flutter Problem and it seems to be getting worse. I Pulled a pretty heavy load today and Here is what it does. 4 and 5th gear, Half to 3/4 throttle This thing sounds like a Basket for of Mad Rattle Snakes. Let of it stops, Floor it It mostly stops. And when its doing this the Boost gauge is Going Nuts. It builds boost very well I think, It will almost peg the 35 PSI gauge. Its this Flutter thing that has me bothered. I did read some other posts about it but they say It does it when they let off and Mine does it when Im into the throttle?? Please help me figure this out It has me Worried.

Unloaded its not near as bad but it still does it.

wannadiesel

BB- Have you read this thread? Mine, with a 12 cm will flutter at low/mid RPM under heavy throttle in 4th and 5th, and I've even heard it in 3rd on a steep hill with my winter weights in the bed. Seems the only sure-fire fix is to upgrade the turbo, either an HX-35 or get your H1C cold side replaced with a H1E compressor. You can "drive around" the flutter by keeping the RPM up, and you can also tune some of it out by setting the smoke screw flush with the top of the AFC housing (no preload on the diaphragm) as well as turning the star wheel CCW to increase the preload. These changes cause the pump to fuel less at low RPM, so you lose some bottom end power, but it's harder to get the flutter. Advancing the pump timing also cuts down on the flutter. I'm surprised you're getting flutter with the 18.5 cm housing, most guys have no issues until they put on a 12 cm.

frostie

I am running a 14 CM non waste gated housing. I think the 14 is too small with my POD nozzles. however I get almost no lag and have gotten 39 PSI boost.
With stock nozzles I think a 14 housing like mine would be a nice combination. The 14 housing cost me $150
With the fuel Im running I have talk to High Tech Turbo in Utah. I think Im going to have my H1C modified to an HX40 compressor wheel and go back to a 16 CM housing.
Just my 2 cents.

Frosty

DJ

I looked at your pictures. Looks like you're not running an intercooler. With as much boost as your running the air going in must be real hot, probably enough to be losing power. You should be able to set the fuel down a little without much loss in power at high boost levels but may be noticible at low boost. Seems like I read somewhere you lose one HP for every 10 degrees increase in air temp. Are you sure your boost guage is correct, do you make a lot of smoke at low boost. That boost pressure sounds way off for an 18.5

furious70

I would agree that those boost #'s don't look right. I have a 16 and I only see 23psi. My pump is only at the '10%' level as the shop I had it done at told me, and I only see smoke at night, so mine definitely isn't fueling too much.

If you look at a compressor map, this high load, high psi, low rpm (read low air volume required) problem is shown by being in the lower left of the graph. Basically you're getting way too much out of the compressor for the air that's required by the motor for that rpm. This makes complete sense with the 12cm hosuing. At low rpm that thing is gonna spin like mad (especially if you're bleeding off the wastegate), and simply provide more boost than the 1st gen compressor side can handle. I wouldn't think it possible to surge with the 18.5, since it was a factory offering.

Anyone got the 2 maps handy to post? It would be nice to have them to compare.

Monty

Getting Holset compressor maps is like pulling hens teeth, and the people who do have them arent sharing.

BigBully

No Im not running a intercooler. I only reach 1150 EGT Pre turbo pulling a heavy load. I have no reason to beleive the Boost gauge is wrong. It starts out at 0 and goes up from there. 70MPH im running right at 5 psi 1900 RPM If I nail it it seems to go up smoothly Except when the flutter starts in. Yes It makes a bunch of smoke at low boost. I turned the smoke pot Down and that helped some But When I first let out on the clucth It smokes pretty bad. Maybe just some adjustments are off ya Think? Im not thrilled about the Smoke but Love the power, Im ready to turn it up some more Since I finnaly got a clutch that will hold.

wannadiesel

Take the cover off the AFC housing and set the smoke screw so it's flush with the inside surface of the cover (no preload on the fuel pin). While you're in there, try turning the star wheel CCW a little bit. You'll know you've gone too far when the truck gets bad turbo lag, turn it clockwise until you're happy with the response. Also, have you adjusted the timing?

Alec

I just realized that your boost numbers are so high BECAUSE you don't have an aftercooler. This also exascerbates the flutter problem. You are flowing the same mass of air that the rest of us are, but at higher pressures, because the air is at a higher temperature.

PV=nrT . . .

Wannadiesel's suggestions should help you out, but you will probably want to bite the bullet and get an hx-35. You also might want to squeeze an aftercooler in the truck.