Stock ecu max boost question

[96atawd]

Hello Tuners, I know alot of people are going to come in here and say there are a bunch of threads on this, and I have read a few, all stating the max safe boost on stock ecu/injectors is 16psi (which is 15psi to me for safety sake). But, is that true for a 14b, or t28 or 16g? Can they all be ran at 15-16psi on stock ecu? Or is that 16psi figure only for the stock t25? I am just wondering because the threads I have read about max boost on stock ecu dont specify if that is only for the stock t25, or if the stock ecu can compensate for a 14b,t28 or 16g up to 16psi on stock injectors? I know a better fuel pump (rewired) would most likely be needed either way, but can the stock ecu compensate for 14b, t28, 16g turbos at 15-16psi, or JUST the t25?

Thank you!

 

[buzzardtalon]

Well im no expert but as long as you dont exceed 16psi i dont think it matters what tubrbo ypu use?? 16 psi is 16psi no matter what the diffrece in turbo would be how fast it delivers that 16 psi (spool) i know my car with the t25 hates 16psi it will not work at all at 16 but at 15 it will scream down the road...so like i said it seems like the turbo wouldnt matter as long as you stay at 16psi im sure you could run a holset hx35 at 16psi and it would be ok but im no expert

 

[ReggieRay]

16 psi on a t25 is not the same as 16 psi on holset hx35, there's a difference in airflow.

 

[GRAVEDIGGER]

Well im no expert but as long as you dont exceed 16psi i dont think it matters what tubrbo ypu use?? 16 psi is 16psi no matter what the diffrece in turbo would be how fast it delivers that 16 psi (spool) i know my car with the t25 hates 16psi it will not work at all at 16 but at 15 it will scream down the road...so like i said it seems like the turbo wouldnt matter as long as you stay at 16psi im sure you could run a holset hx35 at 16psi and it would be ok but im no expert

 

[ReggieRay]

Anyways to answer the question I personally feel 15psi is safe for the for the 14b and 16gs turbo on stock ecu and fuel injectors. But its not about the psi as much as it is about the airflow it can handle.

 

[96atawd]

16 psi on a t25 is not the same as 16 psi on holset hx35, there's a difference in airflow.

Exactly my thoughts. A t25 at 16psi does not equal cfm of any larger turbo at 16 psi. But all the threads I read about just simply say 16psi, nothing about turbo size, which would leave alot of people to think a 14b or 16g etc would be safe at 16 psi on stock ecu injectors. IS it actually safe? Will the ecu actually compensate for the larger turbo as long as it doesnt see more than 15 psi? The reason I ask, is, right now I am at around 11 psi on my t25, and I want to try turning it up to 15, but I think my t25 is starting to die as it is, and was wondering, if I got a cheap 14b (or t28 or 16g), would it actually be safe to run at 15psi with stock ecu/injectors and rewired 190 fp?

 

[LandSpeed-DSM]

Well im no expert but as long as you dont exceed 16psi i dont think it matters what tubrbo ypu use?? 16 psi is 16psi no matter what the diffrece in turbo would be how fast it delivers that 16 psi (spool) i know my car with the t25 hates 16psi it will not work at all at 16 but at 15 it will scream down the road...so like i said it seems like the turbo wouldnt matter as long as you stay at 16psi im sure you could run a holset hx35 at 16psi and it would be ok but im no expert

This is not accurate and you should not be trying to give advice to people.

If "16psi is 16psi" .. why will a 16G (or a GT40R for example) make more power than a T25 at the same boost on the same setup?

Think about that for a second. What's different?

 

[ReggieRay]

Yes it would be safe to run 15 psi on a 16g or a 14b turbo with stock ECU and injectors along with the rewired 190 fp and you'd love yourself for doing it.

 

[GRAVEDIGGER]

I would not run anything other than a stock turbo with a stock ecu and stock injectors... period. If you so choose to try to, I would at least like to have a wideband to monitor air/fuel ratios. A bigger turbo WILL require more fuel for the extra air it produces and no, the ecu cannot compensate for a bigger turbo. Do it right, or do it half-assed. It's your choice.

 

[buzzardtalon]

i may be wrong i never said i was right and i said two times that i am not an expert......but it just seems like to me that "16psi" is the same across the board....seeing as psi is a standard measuring unit for air pressure so sue me.......makes sense to me...yes you make more power with one turbo on 16 then with another but i dont thing that has to do with the amount of psi....cfm would be the difference not psi so technically speaking 16psi would be the same no matter what......its the air flow that changes. And as we are speaking about small stock turbos i don't think my thoughts matter much...feel free to flame me for misunderstanding....that makes so much sense....flame him ...don't help him learn.....

 

[LandSpeed-DSM]

But why, is what I want you to try and wrap your mind around. Why will a 60mm turbo make more power at the same boost on the same setup compared to a 45mm turbo?

If pressure and volume (CFM) are the same.. volume consumed is going to be determined the engines VE or demand flow.. so what else has changed?

Forget that there is a turbine stage on the exhaust side for now, and focus on the compressor.

Think back to highschool chemistry.. does this look familiar? [PV=nRT]

What characteristics of the larger compressor let it make more power.. if the pressure in the manifold is the same and as mentioned earlier Engine Demand has not changed?

 

[thomcasey]

YOu need to check what the airflow for the specific turbo is at the desired PSI FOR THAT TURBO ONLY. Then, look at the flow charts for the stock 450's and see what their limits are. I wouldn't recommend going over 85% duty cycle on the injectors for too long. Also, you must monitor with a wideband if you are going above stock, unless you like replacing engines.

 

[Broke4speed]

i may be wrong i never said i was right and i said two times that i am not an expert......but it just seems like to me that "16psi" is the same across the board....seeing as psi is a standard measuring unit for air pressure so sue me.......makes sense to me...yes you make more power with one turbo on 16 then with another but i dont thing that has to do with the amount of psi....cfm would be the difference not psi so technically speaking 16psi would be the same no matter what......its the air flow that changes. And as we are speaking about small stock turbos i don't think my thoughts matter much...feel free to flame me for misunderstanding....that makes so much sense....flame him ...don't help him learn.....

Water at 16psi from a garden hose will hurt.
Water at 16psi from a 3' pipeline pipe will kill you.

Pressure is pressure, as it's a measurement of how much higher than atmospheric something is pressurized at. Airflow is where the difference lies. Fuel + air = power, and different sized turbos flow different amounts of air at the same boost pressure. That's why different turbos make different power at the same PSI.

 

[91stocker]

Install a wideband it will answer your question.

 

[hotrodssnova]

Water at 16psi from a garden hose will hurt.
Water at 16psi from a 3' pipeline pipe will kill you

That's should be added to the "funniest things you have heard a dsm'r say thread"
The turbos mentioned all have different sized wheels and blade count and blade size. A larger wheel will move more volume then a smaller wheel will at the same psi.

 

[LandSpeed-DSM]

It's not the volume, Engine Demand/VE and turbine section determine the volume being consumed..

Charge density is what accounts for the difference in power at the same pressure ratio between compressors of different size.. that is to say the amount of heat imparted upon the charge.

A 2.0L @ 5000rpm and x% VE is only ever going to consume that volume, how dense the charge in that volume is dependent upon its temperature.

This is oversimplified, but its gets the idea across.

 

[Broke4speed]

That's should be added to the "funniest things you have heard a dsm'r say thread"
The turbos mentioned all have different sized wheels and blade count and blade size. A larger wheel will move more volume then a smaller wheel will at the same psi.

Too much science keeps people up at night, I find.
Live by Occam's Razor...die by Occam's Razor .

 

[gixxer6]

It's not the volume, Engine Demand/VE and turbine section determine the volume being consumed..

Charge density is what accounts for the difference in power at the same pressure ratio between compressors of different size.. that is to say the amount of heat imparted upon the charge.

A 2.0L @ 5000rpm and x% VE is only ever going to consume that volume, how dense the charge in that volume is dependent upon its temperature.

This is oversimplified, but its gets the idea across.

Is it correct to say that all turbos will flow the same amount of air at a given pressure, if installed on the same engine setup? The hp increase seen is strictly do to the fact that the air from the "better" turbo is cooler/more dense?

 

[LandSpeed-DSM]

When you say amount it is important to specify mass or volume in this context.

The engine will only consume a fixed volume, as a function of displacement, VE and engine speed. But the turbo is going to change how much mass is in that volume as function of temperature and pressure.

If you have two compressors, both capable of supplying more mass flow than a given engine can consume, the one that can do so most efficiently will make more power at the same PR because it is not heating the charge as much.. meaning it will be denser at the same pressure.

So its temperature (charge density) that makes all the difference between turbos at a given boost pressure.

There is also the matter of how the turbine side effects the engines ability to breathe but that is sort of beyond the scope of this particular discussion.