Engine/Transmission (1998.5 - 2002) Boost Pressures?

[RussW1911]

I just ordered my Guages and got to thinking.....

I was told My 02 HO produces 17 1/2 Lbs of boost and read on here my max was 21. I am stock now and plan on a EZ or Comp, buit thats about it. will a 0-30 gauge be enough or will I max that out? any help will be great. need to chang my order if I will.

 

[Partyat33]

A 30 psi gauge will be pretty close. With Stock injectors you may not get much over that. I would recommend a 40 to be on the safe side.



Dennis

 

[Mundgyver]

I have 275's and the Comp and can peg mine above the 35 mark at will if so desired. Most of the time, I will be 10 / 20 unless I am pulling a hill and in a hurry and then it will be anywhere from 20 to 29. Just depends on the style of driving.

 

[DLeno]

Consider matching your boost gauge full scale to the limits of your turbocharcher. For example, the stock hx35 is good to about 32-34 lbs max and can be wastegated to this value with the either the Edge boost elbow or the Piers adjustable boost elbow. The standard Westach EGT/Boost gauge is 0-35 lbs and is a good match.



If you plan to upgrade your turbo and then you'll need more than 35 lb full scale gauge. --Doug

 

[HillCountrykid]

My truck will make about 32 lbs. of boost on the lowest setting of the Comp box (EZ rating). I had the 35 lb. gauge when I had the pump wire disconnected. When I put the pump wire on I had to move to a 50 lb. gauge. HTH



Brian

 

[MGordon]

I have never seen over 26 lbs with the EZ. Maybe because of the high altitude?

 

[mgoncalves]

I think altitude has something to do with it. I can only hit 31 with comp on 5x5.

 

[HillCountrykid]

I forgot to say that with the Comp on 5x5 and nothing else I have hit 38 once, but other than that 37 lbs. This is around 500 ft. above sea level.

 

[DLeno]

over 34 lbs with the stock turbo is outside the efficiency map, so you're paying a high price for those pressures (in the form of high EGTs and risk of turbocharger failure). are you guys achieving these high boost pressures with the edge boost elbow? I would suggest the Piers adjustable boost elbow to accurately set the wastegate point.



But getting back to the original question, I don't think you need more than 35 lbs full scale unless you have (or will have) an HX40 or higher turbo.

 

[RussW1911]

Thanks for the input

Thanks for all teh input guys. ordered all my guages and should have them in next week.

 

[ynot]

Hope you ordered the 50psi. Mechanical spring type gauges have the best longevity if kept below the 2/3rd mark. Electric ones generally suck. 35psi on a 50 psi gauge is about right. I bent the needle on my 50psi gauge twice at 56+, and had to replace it (sticky spot at 28psi) on an HX35, btw. Always get the biggest ones you can, as you never know where you will end up on mods and boost, and you don't want to buy stuff twice ;-) ... T

 

[HillCountrykid]

Doug, I have the boost elbow I got with the Comp. I don't run on 5x5 very often, and when I do it's not at 37 lbs. for long. I've heard that 37~ish is the max for the hx35. A Piers hx40 is in the plans for the furture anyways.

 

[ynot]

HX35

For future reference, I (and many others) have 120,000mls on a basically stock HX35 with a 16cm turbine housing (no waste gate)running 38/ 40psi all the time, and will bury the boost gauge (56+) whenever I want, and never had a problem. Spins smooth, quick spool, TONS of power. Cheap too ... T

 

[Amianthus]

You want to keep your max boost in the middle third of the gauge range. So if you're running 50 psi boost, you should have a gauge that is no smaller than 75 psi. and no larger than 150 psi.

Normally, a guage that is twice your max boost pressure is a good way to go.

I also second what ynot said about not buying stuff twice. Heed this advice from those of us that have.

 

[DLeno]

good comments guys. just keep in mind that the stock HX35 should not spin up past 34 lbs. lots of work at Piers behind that number. thanks for the reminder about the cheep HX housing though. while that doesnt fix the spin balance and max rpm issue of the stock turbo, it does help the EGT issue and I would guess that would improve the efficiency map for the higher boost pressures. So thats a good argument for the higher boost pressure gauge if you plan on using the larger housing.

 

[Diesel Freak]

Exhaust housing size has no effect on turbo compressor efficiency.

 

[DLeno]

cool. I think we're on the same page. by "efficiency map" I'm refering in part to the fact that sustained higher boost pressures come at the cost of higher EGTs. pushing the smaller turbos to higher boost pressures results in diminishing returns. So the 16mm housing on a stock HX-35 makes it run cooler -- that makes the higher boost pressures more usable from an EGT standpoint. would you agree?



BTW, in honor of you guys in this thread, I'm exchanging my 0-35psi gauge for a 0-50 cause I just might put that 16mm housing on my HX some day. thanks for reminding me of that

 

[HillCountrykid]

That's 16cm . I know that if you get out of the efficiency map you start making hot boost and not doing any good. I plan to get some injectors next week and I'll be pushing the 35. To not torture the turbo and to keep EGT's down, a Piers hx-40 will be in the plans pretty soon. A guy that lives down here blew his stock turbo by pushing it too hard for too long.



Brian

 

[ynot]

Nothing you do changes compressor efficiency. That is done by changing compressor wheels or bleeds. Changing turbine housings ALWAYS changes turbo efficiency and/ or pressures, even to the point of similar numbers. A 16cm wastegated and plugged will make different boost and spool than a 16cm non-wastegated. Everyone changing wheels, face pitch, leading edge or role pitch, bleeds, etc. are trying to change the MAP range and pressure AT A GIVEN RPM (30psi at 48,000rpm instead of 62,000rpm or whatever). That will cause a slight MAP change, but does it matter? Turbo MAP efficiency is nothing more than keeping the turbo below a certain RPM, as to not make more compressor heat than boost. Super heating the turbo takes running over the MAP for so long that the ATAAC "heat soaks" and ceases to cool inlet air. Has no real detrimental affect on the turbo itself at all. If it takes 50psi+ or whatever to role down the road for extended periods, it may be time to reconfigure more than the turbo anyway. The only thing that really kills a turbo is so many RPM the wheel splits (105,000rpm- 120,000rpm+), a balance problem or shaft/ bearing coking in which the turbine pushes too hard trying to spin the compressor, thereby twisting the shaft. No one has done the hardest and most obvious turbo saver. A bigger shaft. Increase shaft size and you can put any compressor wheel on that you desire. Mid 60's would be easy, and more than that would be possible (sea level/ cold dry day). The real deal would be variable venturi turbines. Big money, but better than twins for road trucks... Whoops; sidetracked :-laf I believe the original reference was to changing turbine housings. End result is about 2- 2. 2psi drop per size. 30psi with a stock 12cm would be 25+ with a 16cm, with a 200degree (or so) correlating drop per size (hot side) in EGT's over 30psi boost or 1000*(i. e. 1350* would then be 950*/ 1000* hot side)... T

 

[Hohn]

You will want a larger boost gauge. I have the Autometer 60psi one, and I can hit 32 at full boogie. Buy something you won't outgrow as your bombs pile up... .



HOHN