How much Boost can i run?

Selsvik

New member
hi!
I am wondering how muvh boost i can run on stock engine. or stock ish
I have recently upgraded the turbo with a bigger turbo from GT4-PLAY, the S148 Hybrid Turbo.
https://gt4-play.co.uk/shop/turbo-technics-s148-560
And i also have the 3" DeCat Downpipe from the same company, and i have mounted a cheap ebay muffler for less resistance.

Stock with no upgrades i was told that i can run 1Bar of boost safely. but now that i have these upgrades the exhaust have much less resistance and is then safer to run high boost(someone told me).
so how much boost can i run safely with these upgrades? :)

Mods:
S148 Turbo
3" DeCat Downpipe from gt4-play
Low resistance 3" ebay muffler
Pod filter
Silicone intake pipe
 

underscore

Well-known member
The general consensus seems to be 1 bar or 14.7 psi is pushing the limit for the stock headgasket. I'd aim for 12-13 tops to be safe.
 

Magroo

New member
I can confirm I blew my head gasket by boosting over 15 lbs. This was the stock jdm composite gasket. Upgraded to arp studs and cometic MLS gasket now.
 

Selsvik

New member
so the headgasket is the weak point on this engine?
If sometime in the future the headgasket blows, what parts is recommended to change? and yes, a stroonger headgasket :)
 

silverarrow

New member
1 bar of boost on stock turbo is NOT the same as 1 bar of boost on any bigger turbo. Your safest bet is to install a wideband o2 on your downpipe and keep an eye on your afr while you slowly increase the boost. I ran 1 bar of boost on one of my previous ST185s just fine on stock turbo though. I ran 12 psi(minimum ext. wastegate spring) on a 60 trim T3/T04e .63 ar turbo kit for a little while, but my engine would ping.

Boost typically doesn't kill motors, it's the tune. With that upgraded turbo, you're probably going to max out your injectors and go kaboom from running too lean and with the stock tmic you're going to run into heat soak which may or can lead to power loss and maybe even engine failure.

Whoever that told you that you can run more boost because you have said upgrades isn't really bright. Not to offend, but find a friend that actually knows what he/she is talking about.
 

freddie

New member
Bar is a metric measurement for Atmospheric Pressure. 1Bar = 1 Atmosphere.
Atmospheric Pressure (measurement) depends on where you are located and how high above sea level
your location is.
Where I am located (Australia) is not so high above sea level, therefore 1bar = 9.8psi. That is what we
work on.
So I think running a boost pressure of say 10psi is pretty ordinary. The A/M ECU and Turbo I am using
in my 205 engine is set at 1.85bar. max. The standard engine in my 165 (with a few mods to help it
breath a bit better) ran at 1.2bar (12psi) exceeding three years of DD without any problem.
 
freddie":1k6hek18 said:
Bar is a metric measurement for Atmospheric Pressure. 1Bar = 1 Atmosphere.
Atmospheric Pressure (measurement) depends on where you are located and how high above sea level
your location is.
Where I am located (Australia) is not so high above sea level, therefore 1bar = 9.8psi. That is what we
work on.
So I think running a boost pressure of say 10psi is pretty ordinary. The A/M ECU and Turbo I am using
in my 205 engine is set at 1.85bar. max. The standard engine in my 165 (with a few mods to help it
breath a bit better) ran at 1.2bar (12psi) exceeding three years of DD without any problem.
Not quite right.

Bar is a metric unit of pressure. Atmosphere is the average pressure at sea level (average in that there are high pressure and low pressure deviations all the time). While BAR and ATMOSPHERE are not at all related, 1 Atmosphere = 1.013 BAR. 1 Atmosphere also equals 14.7 psi.

Atmospheric pressure at 9.8 psi would be at an elevation of 10,750 feet above sea level. That is not very close to sea level at all. Australia's highest peak, Mount Kosciuszko, is 2228 meters (or 7,310 feet) above sea level. So I don't know where in Australia you would ever encounter an atmospheric pressure as low as 9.8 psi.

But, 1 BAR = 14.50377 psi, no matter what, no matter where (these terms are not atmospheric pressure related, just different units of measurement for pressure).
 

grip-addict

Active member
Silver arrow is absolutely correct. The max boost you can run on any aftermarket turbo is Wastegate until you get it on a dyno to check afr's. Installing a wideband is also an option. Just for comparisons sake, the gt3071r makes about 300 whp at 13 psi on the 3rd gen 3s.
 

freddie

New member
Not quite right.

Bar is a metric unit of pressure. Atmosphere is the average pressure at sea level (average in that there are high pressure and low pressure deviations all the time). While BAR and ATMOSPHERE are not at all related, 1 Atmosphere = 1.013 BAR. 1 Atmosphere also equals 14.7 psi.

Atmospheric pressure at 9.8 psi would be at an elevation of 10,750 feet above sea level. That is not very close to sea level at all. Australia's highest peak, Mount Kosciuszko, is 2228 meters (or 7,310 feet) above sea level. So I don't know where in Australia you would ever encounter an atmospheric pressure as low as 9.8 psi.

But, 1 BAR = 14.50377 psi, no matter what, no matter where (these terms are not atmospheric pressure related, just different units of measurement for pressure).

Sorry I stuffed up.
Standard Atmospheric Pressure at Sea Level is 14.7psi = 101.325kpa =1bar (The hard measurement is 14.695psi)
In my neck of the woods the Atm. is 14.77psi = 1018mb (that is at 12.00am 25/11 2019)

My previous explanation is wrong. Total pressure is the Atm + the pressure required. But unit of measurement only relates to the pressure
applied eg a tyre pressure of say 32psi (220kpa) is measured as 32psi (and not + 1Atm)

Therefore 1bar =(approx.) 14.7psi. 10psi = 689.2mb or 0.68bar. 12psi = 0.827bar 18psi = 1.24bar.

So 1bar 14.7psi on a stock engine (with a good few miles on it) may be a bit high.

As I am a qualified plumber and Hydraulic Draftsman, I look at Turbo's like pumps, while pressure and volume are similar,
they are not the same, so I like to think that the bigger the pump, the more mass or volume you are going to get and
pressure is what is going move the mass. No matter what the size of the Turbo is, if you are running say 15psi, then the max.
pressure to the engine cylinder is going to be 15psi. However the CFM volume can increase with the size of the Turbo.

Of cause there are other factors to be taken into consideration such as air can be compressed (water and some fluids
cannot be compressed.) Size of the plenum chamber/inlet manifold and gas flow etc. and engine dynamics.
 

MWP

New member
Everyone giving advice.... but no one has asked which gen of the 3SGTE he has?
It makes quite a bit of a difference to the correct reply.
 

Gert

Active member
Selsvik":21i3cv2z said:
so how much boost can i run safely with these upgrades? :)

Mods:
S148 Turbo
3" DeCat Downpipe from gt4-play
Low resistance 3" ebay muffler
Pod filter
Silicone intake pipe
There is no easy answer for this, IMHO.
Meaning, what is your goal? Are you going to boost the car in fifth gear for 10 minutes? Or are you only going to push 1 bar in first and second gear. In second, she can reach 100 km/h, theoreticaly enough in most countrys :D

And, what fuel? What is the condition of the engine? At what outside temps are you driving. How healthy is the cooling system? Etc, etc.
 

Selsvik

New member
sorry for late answer. But in theory the engine should be in good condition, since i am the 3. owner and the preowners have changed oil every 5000km and filter every 10 000km. but still after changing broken turbo, it still uses a bit oil...
the cooling system is fine! The coolant has also been changed when i changed turbo, so thats good.

it has only run 140 000km, so should be in good shape. but because of this oil usage, i am a bit unsure...

was aiming for 1. 2. and 3. gear,

outside temp now inwinter is cold

Fuel - 98octane, highest quality fuel
 

Gert

Active member
Selsvik":2rwlt0ng said:
But in theory the engine should be in good condition, since i am the 3. owner and the preowners have changed oil every 5000km and filter every 10 000km.
With all respect, but that does not say a thing. Changing oil regularly does not guarantee an healthy engine. Is compression good on all four cilinders. Does she tickle nice. No strange sounds. Good oil pressure.
Healthy fuelpump. Healthy fuelpressure, healthy injectors, etc, etc. We are speaking over antique cars you know...
the cooling system is fine! The coolant has also been changed when i changed turbo, so thats good.
That also is no guarantee for healthy cooling. How is the rad? Are engine temps not rising when boosting.
was aiming for 1. 2. and 3. gear,
That is not too much stress for the engine, that only lasts a few seconds. Even though, as long as you can not monitor real engine temps, knocking and Air/fuel I would not go over 0.9 bar, max 1.0.

Just my humble opinion.

Once, I burned my pistons with an topspeedrun over 1 bar.
 

grip-addict

Active member
If you want to see just how far you can go, you'd want to do different boost levels at different RPM's.
Where an engine makes peak tq is where you have the highest cylinder pressures, which also means the greatest chance for detonation. If you can do variable boost control, then you would tone down the psi at that RPM range, then up it a bit for more top-end power. Traditionally you can do this with an EMS and boost control solenoid, but I know the MR2 guys have found some standalone boost controllers that can also do it as well.

I still think the best case scenario is to put the car on a dyno and slowly ramp up the boost while checking AFR's, especially if you are on a factory Toyota ECU. I've blown up a few modified 3sgte's with JDM and USDM ECU's and I firmly believe that while our cars are great at making extra hp, the 90's electronics just don't have the safeguards in place to control and protect the engine at higher power levels.
 

Selsvik

New member
I am going to send my engine to re-bore from stock 86mm to either 86,5mm or 87mm.
And i will replace piston and rods with forged performance piston and rods.
i will also upgrade the headgasket to a steel headgasket and use ARP bolts.

If i have enough fuel, how much boost can i run now?
 
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