ofelas

Morning all

Would a 14cm wastegated outlet still flow decently allow me to still cruise at 70mph with 3:54/auto/33" tires without affecting my current mileage ?

For max mileage on the highway I want as little boost as possible while cruising empty correct?

This truck is always unloaded, no towing/hauling.

Tranny has been rebuilt with HD parts, synthetic ATF, Transgo & a decent converter.

I understand a smaller than 21 cm housing gives me more usable torque around town.

Just a timing bump, turned stock pin and a less restrictive factory airbox; I don't plan on adding more fuel...famous last words :-laf

mknittle

It would be way better than a21cm

ofelas

Better gas mileage? Better EGTs?

mknittle

Better acceleration. More efficient, you may lose some mileage on top but you may gain some on acceleration.
EGTs shouldn't be a problem. Especially if you aren't towing or hauling. Second gen Hx35s have a 12cm turbine housing from the factory.

ofelas

What kind of boost pressures can I expect while cruising at 70mph ?

mknittle

LOL that's kind of a loaded question. Lots of variables.

ofelas

What variables would come into play? I can try to list them all.

thrashingcows

Are you sure you have a 21cm housing currently? There was only a limited number of those housing put on early 91.5 (?) trucks from the factory...the rest all got 18cm units.

As for what numbers you'll see with a 14cm housing while cruising at 70 mph....as Mknittle mentioned there are way too many variables to make that kind of prediction.

Maybe someone with a 14cm unit on there truck might chime in and give you a ball park figure...but other then that you really have to just get one on and try it out.

Rick 12v CTD

are you sure? I thought all 91.5-92.0 trucks got them.

I know my 91.5 had it. I've never even heard of a 91.5 truck not having it, not that I've made a point of asking or reading up on it. Just a passive observation.

I went from a 21cm housing to a 14cm non gated housing back in the day. Night and day difference. I would guess your mileage would either stay the same or possibly go up.

as for boost, that's a question that can never have a clear cut answer. I can't even give a clear cut answer on my own truck from day to day half the time.

thrashingcows

Believe there was something like 25,000 trucks that got the 21cm housing...but the complaints were so loud from the new truck buyers that they went back to the 18cm after that run.

bigragu

always wondered with mild turns in on the power screw and nasty injectors like PODS,(see my sig) if going back to the stock 18cm ex housing would be more beneficial as far as air flow vs the 16cm that I'm running. Sure it was laggy for a non modified truck but for modified? You think the 16 still outdoes the 18 as far as overall performance?

bigragu

Reason I ask is I still have my stock turbo and always wondered how the truck would perform if I swapped the 16 housing that came with my hybrid HX35 for the 18 housing. With the power stroke intercooler and 3" in/out intercooler piping that turbo set up would engulf and propel more air, you think?

bigragu

Sorry, btw, if I just hacked into the OP's post and topic

Jim Lane

Whenever I do any mods to my turbo or the injection pump I usually find I will get terrible mileage for the next 6 months or until the thrill of the acceleration wears off.

Every time I tell myself to take it easy on the throttle, I am either in a hurry or I find myself in some situation on the freeway where I need to get around someone at a hight rate of speed.

For as heavy as my truck is it has the acceleration of a sports car and suprises a lot of people especially the ricers.

mknittle

What is it about some modifications effecting the nerves that cause hard random right foot spasms?