Engine/Transmission (1998.5 - 2002) Max boost / stock turbo

[24vcummins]

What is the max boost a stock turbo can handle? I installed my boost elbow yesterday and saw boost pressures above 30psi. Is this safe for the turbo?

 

[Oil Burner]

I think you would be ok up to 35 psi or so if it is an HX35. Do you have an HY35 or HX35. I thought they put HX35 into auto-transmission trucks after a certain year but i'm not sure. I don't know if the HY is safe at that boost level. Seems to me it is made to spool quicker with the smaller housing and may suffer when spinning that fast.

-Jason

 

[Diesel Freak]

Stock HX35=34 psi

Stock HY35=30 psi





PDR35=36 psi

any HX40=38 psi



While you can push them farther than those pressures, you just start making more heat than usefull boost... .

 

[24vcummins]

Thanks guys. How do I tell what turbo I have? It's a 99 3500 auto.

 

[Bob Wagner]

your truck has an HX35 turbo

 

[Wyomingcowboy]

ok bob, what turbo do I have?

 

[16919]

ok bob, what turbo do I have?

HX 35... ... ... ...

 

[ERuhl]

Stock HX35=34 psi
Stock HY35=30 psi


PDR35=36 psi
any HX40=38 psi

While you can push them farther than those pressures, you just start making more heat than usefull boost... .

Turbos work on pressure ratios, so these max-boost numbers are elevation dependent correct? 34psi gauge pressure at standard atmosphere (~sea level) is a pressure ratio of 3. 312, and if that is the turbo's limit then that's equivalent to a max gauge pressure of ~26psi here in the mile high city (~. 83 atm)? If so, then I'm seriously overboosting my HX35 at 32psi.

 

[DWeiler]

Thanks guys. How do I tell what turbo I have? It's a 99 3500 auto.

I thought the autos came with the smaller hy35 and us 6ers had the hx35 if memory is correct---doesn"t really matter i dumped my hx35 for my B1-2, has been rock solid for the last 4 years. Oo. Oo. Oo.

 

[16919]

I thought the autos came with the smaller hy35 and us 6ers had the hx35 if memory is correct---doesn"t really matter i dumped my hx35 for my B1-2, has been rock solid for the last 4 years. Oo. Oo. Oo.

all early years all the way to 2000 had hx's in 01 and 02 autos had hy's and manuals had hx's.

 

[DWeiler]

all early years all the way to 2000 had hx's in 01 and 02 autos had hy's and manuals had hx's.

Thanks for setting me STRAIGHTDW

 

[cArNiVaLwOrKeR]

Ok,



What would happen if I put my stock Turbo back on???

 

[SSolderitch]

I see 36 psi with stock turbo, only done with software and no elbow. have rv275 injectors. stock intercooler & intake. 4" banks exhaust. You are saying I am maxed out? Don't have the $ for a turbo and/or intercooler upgrade, but thinking of a intake. Would I see a difference at the butt dyno with my set up?

 

[ERuhl]

Turbos work on pressure ratios, so these max-boost numbers are elevation dependent correct? 34psi gauge pressure at standard atmosphere (~sea level) is a pressure ratio of 3. 312, and if that is the turbo's limit then that's equivalent to a max gauge pressure of ~26psi here in the mile high city (~. 83 atm)? If so, then I'm seriously overboosting my HX35 at 32psi.

I did some more digging on this and a compressor map is hard to come by for the HX35. Holset doesn't publish them like Garrett does. There's a few out there (just do a google image search for HX35 compressor map), but they're inconsistent so I don't know which is correct. The all seem to agree that 32psi in Denver, CO is too much though.

Here's a good writeup that uses one of the common compressor maps, but unfortunately it doesn't really cover high-altitude applications. A question I have, shouldn't the lb/min be adjusted for high altitude as well? The engine volume doesn't change, but the air density sure does.

 

[DFerverda]

I just installed a boost gauge in my 98. 5 auto, i have a set of bosio injectors,i think they are like the 275's. I can only make about 19-20 lbs of boost at wot. Is that about right or do i have a leak somewhere. I have checked the boots and they look ok.

What is the best way to check to see if it is indeed leaking, or is that boost about right? The truck is about 204k on the clock. Thanks

Dirk

 

[SnoKing]

I just installed a boost gauge in my 98. 5 auto, i have a set of bosio injectors,i think they are like the 275's. I can only make about 19-20 lbs of boost at wot. Is that about right or do i have a leak somewhere. I have checked the boots and they look ok.

What is the best way to check to see if it is indeed leaking, or is that boost about right? The truck is about 204k on the clock. Thanks

Dirk

You need a boost elbow to adjust boost and a box to do boost fooling. SNOKING

 

[DFerverda]

THanks for the reply, Where do i get a boost elbow, and which one do i need?

I have a MAD, but it is not on the truck till the transmission is upgraded. How much boost can i do without hurting anything?

Dirk

 

[SnoKing]

I got one from Bob Wagner. 18 or 20 will make the truck run fine. Above about 22-24 the engine will start defueling without a boost fooler. What is it you are trying to do with more boost, are you having EGT issues. More boost on it's own is not going to add more power per say.

SNOKING

 

[DFerverda]

No, i just didn't know how much boost to expect, and see others with higher boost and thought it would make the truck run stronger, I think the MAD will act as a boost fooler, not sure. I will look into more power mods after the transmission upgrade. Thanks

Dirk

 

[NoSeeUm]

Turbos work on pressure ratios, so these max-boost numbers are elevation dependent correct? 34psi gauge pressure at standard atmosphere (~sea level) is a pressure ratio of 3. 312, and if that is the turbo's limit then that's equivalent to a max gauge pressure of ~26psi here in the mile high city (~. 83 atm)? If so, then I'm seriously overboosting my HX35 at 32psi.

Yes, you are correct. With the higher the elevation, to maintain the same boost the PR gets must go higher. PR in essense equates to turbo rpm as well as loosely an air heating factor depending upon compressor efficientcy at a given rpm.



I am at 4000 feet and I limited my HX35 to 30 psi maximum.



The maps of Holsets I have seen are for something above sea leveln (13. 4 psia? maybe). I am almost certain the numbers Diesel Freak spit out were corrected to sea level.



Jim