boost testing with a sps62

torque beast

torque beast

addicted to diesel
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Feb 21, 2008
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has anyone done testing to find the best range to set the boost on a sps62.

Long story short I did some dyno testing and THOUGHT I had my boost set at 44psi but I just bought a new set of guages and found out I was only hitting 39psi so I adjusted my boost elbow and now hitting 48-49. Just wondering if I should drop it down to 44-45? I thought someone had done some dyno testing and showed 44 to be the best power and egts with that turbo, anyone know?
 
I did some and found 42# to produce the best all around HP/egt. I could up it to 50# but egt's went up quite a bit (over 100*) and the net HP gain was only 5HP.
 
so going from 42 to 50 you only gained 5hp? And this was with a sps62 (62/71/14)?
 
I made more HP at 48-50 PSI than 44-45. By adjusting the boost elbow I picked up 18 peak.

This was b4 the DDP90's so ran lower EGT'S.
 
I know air temp,alt., timing all affect boost numbers and higher is not always better but I know I should be more than 38-39 and can tell a difference going to 48 but I don't want to get too high. I would like to get it set as close as I can -like you said, having the proper balance
 
Forrest Nearing said:
yup, boost requires energy to produce...
Click to expand...

While boost requires energy to produce using a wastegate negates measuring HP based on boost. One can increase boost well past efficiency and have a loss in HP. I have seen a smaller turbo pushed to high numbers make much less HP than a larger turbo pushing a lower boost number. Using boost as a basis for HP is pointless as there are way too many variables in the equation. The only true way to measure HP is on a dyno.

Back on my 02 truck I was able to make just shy of 650 RWHP using a moderate sized turbo (steroid B1) @ 43# boost.
 
Jetpilot said:
While boost requires energy to produce using a wastegate negates measuring HP based on boost. One can increase boost well past efficiency and have a loss in HP. I have seen a smaller turbo pushed to high numbers make much less HP than a larger turbo pushing a lower boost number. Using boost as a basis for HP is pointless as there are way too many variables in the equation. The only true way to measure HP is on a dyno.

Back on my 02 truck I was able to make just shy of 650 RWHP using a moderate sized turbo (steroid B1) @ 43# boost.
Click to expand...

we're not comparing a small turbo to a larger turbo... we're talking about an sps62... SO... with that one particular turbo... the more boost you're seeing out of it, the more energy required to drive the turbine... it also takes energy to compress the intake charge in the cylinder.

I don't think a wastegate necessarily negates measuring HP based on boost... I mean, you could just run a larger turbine housing on a given turbo
 
Forrest you are wrong on the wastegate issue unless you are opening it.... If you set the wastegate for 40# it will open as long as you reach this threshold, no additional boost will be created but yet there can be a huge difference in HP based on mods and fueling.

I have done many hours of dyno time and I have personally seen the effects of higher than required boost. The effects are higher egt's and a loss of HP. The steroid B1 I spoke of above was a 63mm turbo (I used it only as an example). Using the sps62 I came up with the numbers in my first post.
 
I guess what I'm saying is I don't see boost as an indicator of HP in any situation... maybe a ballpark indicator, but not a "measure"

put a 1.00 A/R housing on that sps62 vs. the .080 that's on it, and you'll support more power at a given boost level.

but yes, I know what you're saying. I guess I'm just bantering and playing a little devil's advocate to help wake my brain up on this daylight savings' morning! :p

why do they lose hp? going out of efficiency range increases heat in the intake charge and more power is required to push the exhaust charge out against the turbine
 
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