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I have a 93 3500 daully. just hooked up temp boost guage to see what I was getting. Unloaded but steep hill full throttle got around 10-11lbs. factory aftercooled,all hoses look good and tight. as far as I now it doesn't look like anything has been done. what do you normally get stock?. thinking of getting 16cm housing. ,then maybe bigger injectors. does bigger exhaust make much difference, hear pro's and cons.

I tow a 10,000 lb boat. don't want a hotrod but just a little stronger,seems like spool up time is long.



thanks

cwienenga





1993 3500 dually,4wd,auto. no mods yet
 
180 HP injectors and the 16CM gives me 27 PSI:D If I remember right... stock was 17 PSI. Bigger exhaust did help!
 
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Mine was running about 14PSI stock. Turned the pump up a little, got to about 17. Put in 180HP injectors and had the pump timing set correctly and the pump tweaked a little more, now running 25 PSI. Some of the guys that have really cranked on the pumps have gotten up to 40PSI but I think the pump life will suffer. A K&N filter will help if you put one in, your choice as there are some that feel the K&N doesn't filter dirt as well as a stock filter.



I put the 16 housing on and didn't relly see any increase in boost, it just came on a little sooner. (There may be a pound or two additional)



I would suggest that a larger exhaust, high performance injectors be the first things you do. Also have the pump timed correctly and increase the timing to around 1. 5. Had my pump timed and they found the timing pin was off 2. 5 degrees from the factory. Then had the timing set at 1. 7 but am thinking of backing off from that a little. Boost means more air and fuel so the air filter will need something done whether it be a K&N or some other way to let more air into the engine.
 
My '92 made 12psi stock. After turning up the pump, advancing the pump timing to 1. 31mm, swapping the 21cm2 exhaust housing for a 16cm2, adding Rip Rook's 4" exhaust, and installing a BHAF, I now make 24psi unloaded on flat ground. Turbo lag is almost gone. I can’t tell you exactly what I gained from the exhaust housing swap alone, because I flushed the intercooler at the same time (due to a K&N filter). But, after that, I hade 4psi more boost. The 4" exhaust made it a little zippier, and cooled it down. My max EGT's are about 1000-1150 degrees up a 7% grade at 65-70mph.



Mike
 
Mike is right - when changing out a 21 to a 16 housing, the boost will go up. Changing a 18 to a 16 give less noticably improvement

You have an 18 in your 93.



Stan
 
Bigger exhaust will DROP boost! Not much, but by letting the engine exhaust breath easier will lower EGT's & Boost.



Down sizeing the hot end housing makes the exhaust gases speed up through the smaller opening, which inturn, turns the turbo quicker and boost comes on quicker and boost goes up slightly.



Once the exhaust gases move into the down pipe and exhaust pipe it slows down and cools.



Pushing anything through a smaller opening will raise temps, but will speed up the flow at the point of reduction. Which makes the smaller housings spool faster but is poor for towing at higher speeds and longer pulls, as it raises temps, which takes the stock turbo out of the map it was designed for.



So the choice is yours. Smaller the housing, the faster the boost comes on, but the higher the temps in normal driving.



Opening the exhaust side up is always good as it allows you to add more fuel and keep EGT's the same.



You don't have to turn in the power screw to get into the 30's as my power screw is turned OUT from factory setting. :p



Found some more fuel and boost lately. :eek:
 
Bigger exaust after the turbo will increase boost. Boost is more related to presure difference across the turbine wheel than to the temprature. You could pump ice cold air through the turbine wheel and it would make boost if the pressure was high on the inlet and low on the outlet. The lower the presure on the turbine outlett the higher the presure differential and the more boost you get.
 
Sorry I have to dis agree.



As i have taken note of every mod on my truck since i bought it new in 93. Any increase in exhaust end of the engine will lower boost. Including head porting, bigger exhaust housing and exhaust.



Head porting and exhaust size[ not exhaust housing ] will lower boost and egt's. As much as 4 psi drop. But it is a plus as lower egt's mean you can add more fuel for a longer time.



Which is a very good thing. :) Smaller housing will raise boost.



16cm is best all around housing for towing/performance.



cwienenga... yes my truck did come with the 18. 5cm and i didn't notice much performance difference but egt's did go down on average of 75 deg.
 
Why don't you try putting a 2 inch exaust on and see what happens? Smaller turbine housing= higher boost we agree. Back preussure behind turbo lowers boost and is bad in every way. Pressure difference and flow across the turbine wheel is what makes it spin. The faster it spins the faster the compressor wheel spins and the more boost you get. The higher the restrictions after the turbine wheel the less flow and pressure difference and the slower it spins making less boost on the compressor side.
 
I think you are missing my point!

2" exhaust with straight through muffler wouldn't change things for cwienenga's setup unless he was to bomb his truck, which he stated he isn't. I know as i tried straight piping the stock exhaust and it did spool up alittle faster and lowered egt's some but did not raise my boost. The stock turbo can only spin so fast and then anything faster is taking it out of the map it was made for and you will not gain any more boost, only heat. Heat means less air to fuel mixture, which means less performance. The colder the air, the more dense it is, which means more air to fuel mixture.



What amount of boost are you making? Have you tried any of the above? Then a 5" exhaust would make even more boost? Not!

Waste of money unless you have big time hp.



Boost is related more to fuel than air! Try porting the exhaust end of a head and see what happens to your boost! You say less restriction means more boost! With out touching anything else try opening up the exhaust or manifold and see were you are at.



I've tried things along the way, so thats why i'm making the hp/ftlb's i'm making and others are asking how. And no my head is not ported. I will port in time to lower egt's and allow for more fuel. I was going to port when PDR cam goes in but then that would throw off readings on the cam and i would not be able to report true readings on the cam for Piers and others. So i will have too wait and do it the hard way.
 
Ok I see your point. Enlarging an exhaust that is already big enough will not do any good. I don't disagree with you about the porting either.



Obviosly if you opened up the exaust manifold you would loose pressure before the turbine wheel and you would loose boost.



You say you did get faster spool up and more low end boost when you strait piped your exhaust. You may not have had a higher peak but you had more low end boost and lower egt's wich was what my point was. Or more boost for a lower egt.

Looks like we agree afterall.
 
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