Boost psi with s475 over stock

[IdahoRob]

You big turbo should be pushing 1/2 of the total boost. On a stock fuel truck on an all out race tune, you should see 45- 50ish psi total boost.

Let's say 50 pounds of total boost. So you say the primary (big) charger should be making 25 psi. This places the pressure ratio of the "big" charger around 4.4 and the stock charger around 2.7. That makes the total boost of the stock charger 9.25 psi to make your 50 psi of boost with the big charger making 25 psi.

This example isn't too far off on a stock set of twins. Go up in kit size and this "1/2" of total boost will not work well, IMHO.

 

[Chevy1925]

Let's say 50 pounds of total boost. So you say the primary (big) charger should be making 25 psi. This places the pressure ratio of the "big" charger around 4.4 and the stock charger around 2.7. That makes the total boost of the stock charger 9.25 psi to make your 50 psi of boost with the big charger making 25 psi.

This example isn't too far off on a stock set of twins. Go up in kit size and this "1/2" of total boost will not work well, IMHO.

i did not know this! How do you figure that our Rob? based of turbo maps? my "1/2" ratio was based off what i was told by trent and few others for stock turbo twins.

 

[IdahoRob]

rough formula to figure P/R's out and then boost PSI. Then you can take a look at the maps of the chargers to come to your conclusions.

(atmospheric pressure) + (overall boost) divided by (atmospheric pressure) = overall P/R
(atmospheric pressure) + (primary boost) divided by (atmospheric pressure) = primary P/R
(Overall P/R) divided by (Primary P/R) = Secondary P/R
(Secondary P/R x (atmospheric pressure) minus (atmospheric pressure) = Secondary Boost

So in your example we'll use sea level:
14.7 + 50 / 14.7 = 4.4 P/R
14.7 + 25 / 14.7 = 2.7
4.4 / 2.7 = 1.629
1.629 x 14.7 - 14.7 = 9.255 psi

 

[Chevy1925]

rough formula to figure P/R's out and then boost PSI. Then you can take a look at the maps of the chargers to come to your conclusions.

(atmospheric pressure) + (overall boost) divided by (atmospheric pressure) = overall P/R
(atmospheric pressure) + (primary boost) divided by (atmospheric pressure) = primary P/R
(Overall P/R) divided by (Primary P/R) = Secondary P/R
(Secondary P/R x (atmospheric pressure) minus (atmospheric pressure) = Secondary Boost

So in your example we'll use sea level:
14.7 + 50 / 14.7 = 4.4 P/R
14.7 + 25 / 14.7 = 2.7
4.4 / 2.7 = 1.629
1.629 x 14.7 - 14.7 = 9.255 psi

Thank you rob!

 

[catman3126]

subd

 

[dieseladdiction23]

Thanks everybody for all the info, i will do some more checking and see if I can find anything.

 

[chevyburnout1]

Good info here! I know Garret's website has finally expanded on their diesel compounding tech section.

 

[MaxPowerLB7]

Could be boost leak (boot, flange, intercooler), high return rates on injectors or possibly maf tuning. Rob should be able to help you narrow it down if you are able to get a log.

My basic rule for compounds is 1/3 total boost from the big charger and 2/3 fron the small charger. So if your 30 overall you should see 10 from your atmosphere charger (s)

 

[quadracer37]

Pressure testing is very Important! That would be first on my list to check once the tuning is squared away.

 

[Benltr]

i was seeing 48 to 56 depending on which gear. It didnt stayed at 56, it creeped there but ran consistant 48-51

 

[Robby Avery]

Def good info subd

 

[j.stanton2009]

Michael, is that kit still fighting ya!

 

[dieseladdiction23]

I got tired of messin with it lol, it's still not making the boost it should, right around 38-40psi. Oh well haha

 

[Harbin_22]

Sure your gauge is correct. Do you hold rail pressure like it is supposed to?

 

[Harbin_22]

How much boost from the big charger? Hooked a drive pressure gauge up?

 

[PACougar]

Have you dynoed it, or even better taken it to the track. That will really tell you if somethings not right. If the power is there then it could be something much more simple like a bad guage.

 

[dieseladdiction23]

Well I don't really know what power it should make with my setup. I want to say it's making 20 off the big charger but it's been awhile since I paid attention to the gauges because it's to depressing haha.

 

[Chanzilla]

Well does your truck feel like it's got an s475 on top of your stocker ? I guess it might be a stupid question but like PAcougar said , if it is running mechanically sound , then it is probably a gauge. Have you tried logging it?