Turned down boost...how much hp per PSI do i lose?

[JoeyJigglesGSX]

I'll make this simple and then if you need more info. i can explain...

I had to turn my boost from 25psi to 18...about how much hp do i lose? i have an EVO III 16g

 

[Spln_Hrd]

they say one pound is about 10 hp. but there are alot of factors, you timing i am sure is advanced way more unless you put in worse fuel. also turbo efficiancy makes a differance, a t-25 maxed out vs a t-25 at 13 psi wont be much differant because of efficiancy and timing and intake temps

but roughly 10 hp

 

[nightspeed87]

theres too many veribles to answer that, only way to truely know is dyno it at 25, then at 18 and do the math.... I would think you didnt loose as many as you think because the 16g isnt said to be efficent past 21 or 22 psi so after that you could just be blowing hot air and even loosing power.... But what you lost in hp, you gained in knowing your not messing up your engine or turbo... think of it that way.!

 

[JoeyJigglesGSX]

see thats what i hear...but that can not be true...i had my car dynoed at 16 PSI and i had 230.8 to the wheels...then i got my front mount and re-did it, but my boost gauge was getting stuck and we didn't know it at the time, when i realized it on the way home, i pulled the gauge out because it was getting pinched, it was on the dyno at 25psi and had 273 whp (this was on the hot day wed. for everyone in the east coast, heat index = 115) so they said to add approx. 15-20 hp) anyway, i turned it down to 18 that would mean technically i would lose 70 hp, bringing me lower than what i was before...

so how much hp do you think i lost?

 

[Spln_Hrd]

theres too many veribles to answer that, only way to truely know is dyno it at 25, then at 18 and do the math.... I would think you didnt loose as many as you think because the 16g isnt said to be efficent past 21 or 22 psi so after that you could just be blowing hot air and even loosing power.... But what you lost in hp, you gained in knowing your not messing up your engine or turbo... think of it that way.!

what he said their is no way to know other than a dyno

without race gas or alchy injection to reduce knock i don't think you would loose more than 20 though because of knock

 

[whiteturbo]

a kinda off topic question, but lowering the boost, will you get significantly better mpg?

 

[MyBeatGSX]

see thats what i hear...but that can not be true...i had my car dynoed at 16 PSI and i had 230.8 to the wheels...then i got my front mount and re-did it, but my boost gauge was getting stuck and we didn't know it at the time, when i realized it on the way home, i pulled the gauge out because it was getting pinched, it was on the dyno at 25psi and had 273 whp (this was on the hot day wed. for everyone in the east coast, heat index = 115) so they said to add approx. 15-20 hp) anyway, i turned it down to 18 that would mean technically i would lose 70 hp, bringing me lower than what i was before...

so how much hp do you think i lost?

Dynojet's have built in weather correction factors. So it doesn't matter if its 10* or 150* when you dyno it, the number you see already compensated for the temperature, barometric (sp?) pressure, and humity.

273whp is pretty bad for 25psi, you were probably knocking alot.
So I'd say you probably lost a lot of power down low, but your peak power number probably won't be too much different.

 

[NewTurboTuner]

Its really hard to answer that. Boost is not just boost.
A 14b can make 20psi, but it has to work really hard to do it, and the air is hot so it doesn't have alot of oxygen in it.
A 60trm can make 20psi, and that easy for it to do. So the air is cool, and has more oxygen
So you see... Not all boost is created equal.


Gale Banks says roughly every 15psi, doubles the engine's power.
Of course 15psi on a v8 is more HP gain than 15psi on a 4banger. (thats another reason why you can't say... X psi = Y hp.)
...excluding air temps... Roughly 15psi is x2. 30psi x3. 45psi is 4 times the engines out put and so on and so forth ...make sense?
There are now turbo diesel engines with over 130psi!!! They are freaking powerful a phuck!!!!!!!


Yes if you turn down the boost you will get better gas mileage, BUT... just don't step on the gas pedal that hard.
If you don't create boost, then you won't burn the extra gasoline that is added to that boost. So don't get on the gas pedal hard.
I watch my boost gauge to make sure that I'm saving fuel. If I see the boost go up, I back off that gas pedal... and that how you save gas .....you don't burn it

 

[JoeyJigglesGSX]

ok thanks for your help guys...another question though on tuning:

does it matter that we were tuning my car at 25psi? do you think that i could have gotten a better tune if we were tuning it at the expected 18psi? should i save some money and get it tuned again, or does it not matter?

...also that dyno tune basically blew out my gasket on my manifold and i have a loud leak, or somewhere in the front i have a loud leak

 

[nightspeed87]

Its really hard to answer that. Boost is not just boost.
A 14b can make 20psi, but it has to work really hard to do it, and the air is hot so it doesn't have alot of oxygen in it.
A 60trm can make 20psi, and that easy for it to do. So the air is cool, and has more oxygen
So you see... Not all boost is created equal.


Gale Banks says roughly every 15psi, doubles the engine's power.
Of course 15psi on a v8 is more HP gain than 15psi on a 4banger. (thats another reason why you can't say... X psi = Y hp.)
...excluding air temps... Roughly 15psi is x2. 30psi x3. 45psi is 4 times the engines out put and so on and so forth ...make sense?
There are now turbo diesel engines with over 130psi!!! They are freaking powerful a phuck!!!!!!!


Yes if you turn down the boost you will get better gas mileage, BUT... just don't step on the gas pedal that hard.
If you don't create boost, then you won't burn the extra gasoline that is added to that boost. So don't get on the gas pedal hard.
I watch my boost gauge to make sure that I'm saving fuel. If I see the boost go up, I back off that gas pedal... and that how you save gas .....you don't burn it

Bravo !!!! I should shake your hand for that post ....

a kinda off topic question, but lowering the boost, will you get significantly better mpg?

Have the boost set as high as you can run it, just dont let your rpm go high enough for the turbo to start making the boost and you wont have to worry about gas milage... Thats the beautiful thing about turbo and another reason Id opt for it over a supercharger any day!!!

ok thanks for your help guys...another question though on tuning:

does it matter that we were tuning my car at 25psi? do you think that i could have gotten a better tune if we were tuning it at the expected 18psi? should i save some money and get it tuned again, or does it not matter?

...also that dyno tune basically blew out my gasket on my manifold and i have a loud leak, or somewhere in the front i have a loud leak

I see that as another reason why you shouldve have been running that much boost on your set up in the first place... Lucky you didnt blow your hg also with that....
18lbs tuned on your turbo would be good, and yea you may have slightly lost power, but you gained some of your engine/turbo life and efficiency back... Theres no telling how bad you were knocking on that set up... But whenever you do get a bigger turbo, and upgrade fuel and etc to safe run 25 psi youll see that your new 25psi set up will easily conquer your old 25 psi and youll feel what 25 psi feels like once done right...

 

[JoeyJigglesGSX]

I see that as another reason why you shouldve have been running that much boost on your set up in the first place... Lucky you didnt blow your hg also with that....
18lbs tuned on your turbo would be good, and yea you may have slightly lost power, but you gained some of your engine/turbo life and efficiency back... Theres no telling how bad you were knocking on that set up... But whenever you do get a bigger turbo, and upgrade fuel and etc to safe run 25 psi youll see that your new 25psi set up will easily conquer your old 25 psi and youll feel what 25 psi feels like once done right...

ok, but that doesn't really answer my question...do i need to get it re-tuned or do you think that i am fine? because like i said it was tuned at the 25psi by accident and i turned it down to 18 now, everything is running fine, but is my tune off since i didn't technically tune it at the actual 18psi?

 

[SRTthis]

ok, but that doesn't really answer my question...do i need to get it re-tuned or do you think that i am fine? because like i said it was tuned at the 25psi by accident and i turned it down to 18 now, everything is running fine, but is my tune off since i didn't technically tune it at the actual 18psi?

should just run a little richer... wont knock now though.

my truck runs rich as shit when im running the stock pulley on my race tune... (i was told i couldnt run 12's on a stock pulley had to prove them wrong)

 

[NewTurboTuner]

YES.
It should be re-tuned for 18psi.

I highly doubt your 25psi tune was optimal.
My EVOIII ran 25psi on water/meth with no knock. I know I couldn't run 25psi without it. With my setup I run 17psi easy, 19psi is OK. I can get away with 20psi, but anything over that and I need the meth injection or race gas to run a good tune.

Yeah you can go too high. it gets to the point where the boost is too much... then your tune is not good, and you start to loose power. I bet with a good tune @ 18psi you will be much happier. You'll probably get the same power, plus you don't work the system nearly as hard.... Go re-tune it!




nightspeed87 wrote:
""Bravo !!!! I should shake your hand for that post .... ""

Thanks Nightspeed! Its good to help out our fellow DSM'rs. We're all pretty much here for the same reason. We can't shake hands this far away, but I do except Rep points
Thanks

 

[donmagicjuan]

YES.
It should be re-tuned for 18psi.

I agree. Your tune at 25 psi would probably suffice to the extent that you wouldn't risk damaging your engine, but you would likely see some gains by going through and tweaking everything again. Adjusting the tune for different boost levels is normally required because of the departure from linearity of the MAS signal and the difference in load maps stored in the ECU. The 2G MAS was calibrated for the much lower airflow of the T25, meaning that it doesn't provide the best response when dealing with 25 psi from a 16G. All of this can be compensated for, of course, with some type of tuning device, but it usually means that tunes for each level of boost you run on your setup will be unique.

 

[JoeyJigglesGSX]

damn all you guys to hell...haha, jk, i just didn't want to hear that...but thanks a lot, now i have an answer, great responses donmagicjuan, newturbotuner, and srtthis (love the name)...and thanks for everyone elses help...you have all been very helpful

 

[JoeyJigglesGSX]

ok, last question...

is there a skill to tuning? like i went down to extreme motorsports and that was a complete waste because of this problem but i have a shop close by that can do it for me...so my question is do some people do a better job than others? or does it not matter?
(this should show my inexperience in tuning or even what it is)

 

[donmagicjuan]

ok, last question...

is there a skill to tuning? like i went down to extreme motorsports and that was a complete waste because of this problem but i have a shop close by that can do it for me...so my question is do some people do a better job than others? or does it not matter?
(this should show my inexperience in tuning or even what it is)

Yes, so to speak. Tuning is a very iterative process, but not a very difficult one. The more time you put into getting everything set up just right, the better your results will be. Some people have less patience (or a shorter attention span) when it comes to tuning, and that shows, too. If you are able to watch a person who knows what they are doing, you'll see what I mean. The best way to do it is on a dyno, since you can directly measure your results, but this also makes it a time-consuming ordeal. If your local shop has a decent reputation and some experience with tuning, you should be able to trust them.

 

[SRTthis]

damn all you guys to hell...haha, jk, i just didn't want to hear that...but thanks a lot, now i have an answer, great responses donmagicjuan, newturbotuner, and srtthis (love the name)...and thanks for everyone elses help...you have all been very helpful

thanks man... has nothing to do with the those ###got SRT4 driver morso the SRT10 rams who think they can roll with the REAL sport truck king!

 

[JoeyJigglesGSX]

yeah this shop is prob. the most down to earth shop...and they have an awd dyno xoticmotorsports.com so i guess i will just go back to them...thanks a lot

 

[NewTurboTuner]

Tuning can be fairly easy if you have the right tools to monitor, and correct your tune. I have a wideband O2, and DSM link which is great for that.

At its basics.... tuning is fairly simple.... this is how "I" get by right now......
I already have a good idea about where my PSI should be... but if you don't know, start your PSI low and work you way up. I think a good tune starts with a good Air fuel ratio. Any A/F ratio from 11.0 -12.0 is considered pretty safe for our turbo cars. Keep in mind being too rich is much better than being too lean... so if you have to go towards one side, or the other, go rich. Once I've got my A/F ratios dialed in, then I start tuning the timing. I start low with it the timing, do some 3rd gear pulls, and watch for knock. If I don't see any knock then I increase timing by 2 degrees, then do another 3rd gear pull. If I don't see any knock after that ...then I increase timing another 2', and do Another pull. I keep doing that while increasing my timing until I see knock. After I see even 1 degree knock, I back the timing down 2-3 degrees to keep things safe... that's technique usually nets me a decent tune.

Now... say you've got your A/F ratio tuned, but you are having trouble tuning the timing. You're getting too much knock, even when the timing is set low.... Well that probably means you're trying to tune with too much boost... its just not going to work. So at that point, back down 2-3PSI and start over. Do the A/F again, and then try tuning the timing again.

Keep in mind there are many variables to tuning.
A/F, and timing are just the bare bones of it all. But for lightly modded cars that technique has served me well.

WARNING: If you are tuning for the 1st time START LOW!!!! It takes time to get it right OK. You might do 10-15 passes easy before the tune is 100%. If you try to do a quickie job and end up blowing your motor... Don't go blaming me. Just have patients, start low with your tune, take your time, and do it right. After you are done it is a very satisfying feeling to have tuned your own car(aka: Your Baby).

 

[NewTurboTuner]

And yeah, for you guys/gals out there who don't have the tools to tune your own ride.....

.....Go to a good, reputable shop .....A good tune is worth every penny!!

 

[tonymitss5]

As said before roughly 10hp per pound of boost.

 

[JoeyJigglesGSX]

wow...newturbotuner, where did you learn how to do this tuning stuff? did someone teach you?

 

[SRTthis]

Just have patients, start low with your tune, take your time, and do it right.

thats very important... granted i work for my tuner but we have about 100 hours into my tune in my lightning.... but with my mods NO ONE can touch me. im 3tenths faster then any one said could be done with my mods

 

[GSTBlack95]

I learn how to tune, by watching my car get tuned for the first time. Just ask alot of questions, take your time and you will be amazed at how much power you will make its crazy.