Feedback on Boost pressure

I'll post this here because I think its related to my wastegate/ regulator setup. What #'s are you guys seeing for boost pressure? I'm looking to get a consensus before I start tearing into it.

Quick review of whats going on and my concerns. Ever since installing waste gate my maximum MAP (Manifold ABSOLUTE Pressure) I record is right around 38psi. I'm @ sea level so give or take depending on the weather on average that equates to about 24psi MGP (Manifold Gauge Pressure) or what the gauge in dash displays. I've completely backed off regulator to see if I could get boost to rise. Nothing. Now I know the actual max. boost level will invariably differ from tune to tune, but I'm primarily interested in the race tune numbers. Say 275 hp and up since these are my daily driver files.

To narrow my field, I currently run Spartan files and I've been running 300hp file (nice DD tune). I've run all files from 210 and up to 310 (truthfully 350 also but I won't blast it cause I'm not about to roast my stock trans, so not an accurate assessment) with all the same results at or about 38 psi MAP. I briefly discussed with a buddy today and we are both thinking either gate is plumbed wrong or regulator is not working cause he see's 48 psi easily on average. Don't get me wrong my ride still gets and goes damn well but I want to realize the limits because my motor can safely and easily handle the bad boy files with the mods I've done (see sig.) I'm gonna try and bypass the regulator to see if I can get gauge to move, if that doesn't show a result I'll look to plumbing on gate.

So what do you guys see for yours? Could you please identify your maximum psi in either MAP or MGP and what/who's hp file/ you are recording? This will help me pragmatically get to the bottom of this. EP figures would be great also? I want to play :evil Thoughts?

First off you need to be carefull when selecting manifold absolute pressure, because one of thoughs readings happens to max out at 36psi...

I would select manifold guage pressure KPI if i remember right that will give you the max boost reading.

Kilo Pascals?

I think the 45-48 psi range is optimal as long as drive pressure is in check. As long as you have head studs, I wouldn't worry to much about boost pressure. Getting a good ratio of drive pressure to boost pressure would be my #1 goal.

I think 45-48 psi of boost and 52-55 (67-70 on the DD) psi of drive would be a good ratio.

Danbonzo said:

Kilo Pascals?

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its deceiving it still reads PSI

Or at least mine does...

08stroker250 said:

I think the 45-48 psi range is optimal as long as drive pressure is in check. As long as you have head studs, I wouldn't worry to much about boost pressure. Getting a good ratio of drive pressure to boost pressure would be my #1 goal.

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Thats the problem I don't think I'm seeing 45-48 psi. I got all the tid bits and I want to test their limits if you follow.

Dzchey21 said:

its deceiving it still reads PSI

Or at least mine does...

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Ok now I'm confused

go out and try it, but im pretty sure it reads regular PSI

If not select manifold guage pressure go for a quick drive, you should see 40 psi with the converter locked easy.

my truck on stock turbos would not go over 34psi untill the converter locked.

I have my gate dialed in so at light throttle and cruise I am almost a dead on 1:1 ratio. only when romping throttle will I max out boost @ 38 psi (again MAP) and wastegate controls my EP to 65-68 EP which I've been told is the SAFE target. I believe there is more boost in this thing than 24 psi MGP, No????

Danbonzo said:

I have my gate dialed in so at light throttle and cruise I am almost a dead on 1:1 ratio. only when romping throttle will I max out boost @ 38 psi (again MAP) and wastegate controls my EP to 65-68 EP which I've been told is the SAFE target. I believe there is more boost in this thing than 24 psi MGP, No????

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Thats what im getting at...


when you select the MAP on the dashdaq, its reading map with absolute pressure built in, for whatever reason that particular pid max's out at 36 or 38psi total, so the boost is still climbing but the guage wont move, thats why im saying to go look at manifold guage pressure and you should see well over 35psi guage pressure.

24psi of boost you would have a smoky pig i bet... plus your drive pressure is high enough that im betting actual boost is in the 45psi level.


Or watch the factory boost gauge, if it goes to 30 you know your making more boost than that...

Im gonna try it now give me 10.

65-68 on the DashDAQ is only 50-53 psi of drive at sea level. That would be a good number if your making around 45-48 psi of boost. 1:1 doesn't make power, but it's great for daily driving. I think to make power, you need 7-10 more psi of drive than boost.

actually jeff 1:1 usually gives better power, and 10 psi more drive than boost tends to make the truck drive better, key is to keep drive up a little untill you get almost to the top of the boost level, and then vent off the little drive pressure to get it down to a comfortable level, that way you can kinda mix the benifits of both

Dzchey21 said:

actually jeff 1:1 usually gives better power, and 10 psi more drive than boost tends to make the truck drive better, key is to keep drive up a little untill you get almost to the top of the boost level, and then vent off the little drive pressure to get it down to a comfortable level, that way you can kinda mix the benifits of both

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good info

Standing on it: MAP 37 psi, MGP 26.4 psi, EP saw 62.5 psi.
Question; if the valve seat was installed upside down would it make any/ or barely any boost?

yes, and it would probably drive like POOP

for that drive pressure you should be making alot more boost IMHO

Dzchey21 said:

yes, and it would probably drive like POOP

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Well that ain't the problem then, again it goes good, I just think there is more in it. I know of 2 ways to plumb gate. I have a line off cfm to input of reg. then output to gate. on top of gate is vented to atmosphere. I believe Tad plumbs another way but I was told pressures are erratic and hard to dial in. Again hear say. Too late now but I'm going to try bypassing regulator by closing down line from reg. to wastegate. and see if I can get boost to go up. I'll just be careful with the EP.

Dzchey21 said:

actually jeff 1:1 usually gives better power, and 10 psi more drive than boost tends to make the truck drive better, key is to keep drive up a little untill you get almost to the top of the boost level, and then vent off the little drive pressure to get it down to a comfortable level, that way you can kinda mix the benifits of both

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Then why do tuner only trucks tend to make more power than trucks that are gated with just a tune? I don't know enough about this stuff to say for sure, but the trends point to stock trucks with stock turbos and no gate making more power than the same setup with a gate.

I am still learning all of this as well. It's hard for me to see it though. All gated trucks that have been on Dunbar's dyno do lower than non gated trucks with the same setup. That is all.