Haulin_in_Dixie

A four inch down pipe will be part of the switch. I have held up on an ebrake until I have the four inch. And then it will be an air switched in line unit. I have an almost new hx35 to put this on. I have also waited until the current unit is getting loose after 327k miles. See, I'm old and sorta wait for things....

wannadiesel

Bill, I think the 18.5 cm housing will work well for you. The ISB will spin it up no problem, and with the loads you're pulling it will help economy a good bit. The 12 cm is giving you a lot more boost than you need in cruising situations.

ddestruel

I went to the 18.5 on my hybrid turbo and 4" exhaust and had good luck at 280 hp 715+ ft/lbs i think thats the numbers on my 180 hp pump 96 12v. i didnt mind the lag at allactually liked the way the combo worked especially when pulling long grades and keep egts under control.

never considered it till now my mileage was usually more consistant across the board when towing ect when compared to how much things varied with my 12 and 14wg housings. inow looking back it seems like it was the fast spool up and rapidly climbing egts with the hybrid while towing and 10-12 mpg towing after the change up to the 16cm and the 18.5 (cant compare didnt pay attention closely) if i hammered the throttle things didnt instantly happen but if i already was spooled up or mid spool up like in a big truck i could stay in it and the EGT's slowly climbed and i was able to hold my power better. dont know how to explain it but HID you are sounding like your description mirrors something i might have experienced and didnt realize happened

Haulin_in_Dixie

Ok guys thanks for all the input. I have done a lot of digging on the subject and could not say much about it because of the difference to the drag type of power that most are into. I have read much from pro's that power up diesels for big trucks and they all say the first thing to do is get the housing bigger and the boost to 16 or below for pulling hills. I spent some time looking over the specs for the cummins engines for trucking before and after the EPA onslought. EPA made it necessary to go with the smaller housing and riding against the waste gate. That gives you less smoke and emissions on the bottom end. But the overall package is more power and economy pulling steady as you do with freight, with the lower boost and larger housing.

As in my signature, my engine is 275/660 stock and then I have the EZ, Scotty II, and open exhaust. I will be trying it, just have to get the parts together, a downpipe, etc. Currently half throttle at highway speeds puts it against the wastegate at 30 pounds. Light throttle with little or no boost, does not smoke so I think I will be ok. I might even play some, try it with the stock hx35/18.5 and later I have a hx40 compressor wheel and housing that I can try and see what it offers.

Ok, one more question on this. How big is the exhaust outlet on the 18.5? I know it is flange type, but are there some with 4" instead of 3"?

G1625S

HID,
Have you considered drilling the wastegate to waste all 6 cylinders and enlarging the passage at the same time the way Wannadiesel did? Heh, you'd prolly still peg the boost gauge, only at 3/4 throttle:> Still, it's free to try. I've heard of a w/g 16cm2 housing with 4'' outlet for an hx40, so maybe there's an 18.5 too.
greg

dodgeman01

My 18.5 don't spool like a 12 but if you have enugh fuel you can spool it up pretty fast. I have no problems with my truck a spool up. If I want to drag race I just put the truck in 4x4 high 3rd gear and let the clutch do the work I droped 8-10 PSI going from a 12 to a 18.5.
DM01

wannadiesel

18.5 has the same size outlet as the 12 cm.

I didn't realize you were up against the wastgate all the time, you will see a pretty good jump in mileage by getting rid of the 12 cm.

cumminsdriver635

This thread is interesting. What HID is saying sounds pretty logical to me. If you can peg your boost at 30psi at half throttle, then sounds like you should be fine with spoolup. When i put the 16 on my truck i could tell it spooled a little slower, but i dont even notice it now, and i know an 18.5 cant be that much worse. Its worth trying for sure. Seems like mine spools faster rolling into the throttle instead of gouging on the pedal anyways.

Eric

Haulin_in_Dixie

I had a board member from Colorado with a housing contact me but the message was lost. I am still looking for an 18.5 housing. Actually I thought there would be several as the 12 valvers like to go smaller. Looks like I also could use the elbow if someone has one till I get a larger downpipe.