Engine/Transmission (1994 - 1998) Max "Safe" boost pressure

[Bhale]

I peg my 30 lb boost gauge with the latest upgrades and am waiting for Genos to send my new 60lb gauge. What would be the max safe boost i can run with the stock turbo and housing?



Thanks



Brian

 

[HoleshotHolset]

After 35psi, the stock turbo isn't as efficient as it is at boost levels below that point.



Once you operate a turbo out of its most efficient point on its compressor map... . all you are doing is blowing excessively hot air into your engine. The intercooler helps... ... but its not doing you much good if you don't need the boost in the first place. A good rule of thumb is to only use as much boost as you need to burn the fuel that you are putting into the engine.....



HTH,



Matt

 

[Rammin On]

Also keep in mind the higher the boost level - more stress is created on the upperend without measureable increases in power at stock engine/turbo boost levels over 35-36 PSI range . .

 

[Bhale]

Thats what i was afraid of, that i was beyond the usable boost level of the stock turbo. I still have the 16cm housing sitting here and i'm debating on putting it in. I assume it won't spool up as fast as the stock and i'd need bigger injectors to feed it. I guess i could also hook up the wastegate but that cuts out around 25psi i believe.



The 60lb gauge will be here tomorrow and i'll see just what it's doing beyond my 30lb gauge.



Thanks

Brian

 

[illflem]

Besides boost over 35 psi being counterproductive the intercooler is only rated at 50 psi. You need a turbo with more cfm, not psi.

 

[BWilson]

I have the 16 cm housing on my truck with stock injectors and my truck still smokes (black) at full throttle and 42 psi boost. I am assuming that the unburned fuel (black smoke) is an indicator that I am getting enough fuel for my boost pressures. I've got to tell you, when the boost gage hits over 40, hang on!!!! If it's wet out I can spin my 35" BFG's at 60 mph in fifth!

 

[Koa Man]

Max boost I could get with my stock turbo was 34 psi. With the PDR HX35/14 non wastegated, max boost is 40, maybe 41.

 

[HoleshotHolset]

Dad's truck gets 39psi out of his 'elbowed' stock HX-35...

I used to get 39psi out of my 'plugged off' stock WH-1C...



Matt

 

[Bhale]

The new gauge arived today from Geno's and it took all of 15 minutes to install. Went for a ride and could only get the boost up to about 34-37 psi. Even up hill on the highway didn't get me to 40 so i guess i'm safe.



Sure is good to know what the engine is doing!



There seems to be a black cloud hanging over my neighborhood... .



Thanks again!

Brian

 

[drice]

Question

so is it bad that I am pulling 40-42 psi with a stock turbo and a small exhaust leak in the manifold??? if so what do I need to do? bigger housing. or bigger turbo.

 

[HoleshotHolset]

A bigger housing should reduce overall boost... . in theory. Remember... anything above 35psi and you're just blowing hot air.



Fix that exhaust leak too, even if you do it just to keep busy for a few hours.



Matt

 

[drice]

fixed

I fixed the leak today waiting till tomarrow to test run it I guess I am going to order a housing this weekend. any ideas on what size so that I don't have TOOOOO much lag I was thinking 14 maybe 16. any help would be nice. Thanks

Daniel

 

[Joseph Donnelly]

BWilson, if you have a very strong torque plate, some fuel is coming into the cylinder very late and it doesn't burn well, adds little if any power. That is where much of the smoke comes from.



DRice, the 14 housing will spool faster than the 16 but the 16 will help about twice as much with max egt reduction (150-200 deg). If you want a 14, look for a used one in good shape because they are pricy new. (email me offline if you need more info as this has been covered before on the forum).

 

[BWilson]

Ok, now I have a couple of questions. I just read the article in the TDR about airflow and I have determined that I most definitely need some airbox upgrades. This should give me more power and less smoke.



Joe, will larger injectors (370's) get the same amount of fuel into the cylinders in a shorter amount of time thus creating more power with less smoke? Or are there other changes I should make (based upon my late fuel injection? advance the pump?)?



Holeshot, I don't understand why theory dictates that anything over 35 psi boost is wasted. I can feel a significant increase in acceleration from 35 to 42.

 

[HoleshotHolset]

BWilson: Don't get me wrong... . I fell a huge difference between WG plugged off and running with OEM WG setup. The fact that still remains is that your HX-35 isn't loving life after 35psi... . you will reduce its service life and it is operating beyond its most efficient range within the compressor map. We all seem to be able to get away with it, though... . which is a testament to the durability of the smaller HX-series Holsets.....



Matt