How much can I boost???

Hello, I have a 2nd gen 3s-gte motor in my '91 MR2 and I was wondering how much can I boost up to and still be safe. The motor has a T3/T4 hybrid turbo done by turbonetics, ACT clutch, HKS chromoly flywheel, Greddy Profec-B II Boost Controller, Greddy Boost CUT controller, Blitz DTT turbo timer, and I think that is about it. Everything is stock. Please help me, I really want to know where my range of boost will be at.

i heard 12 is good for street...and 18 would be the best for race...

But will it still be safe?

But will it still be safe?

well in that case is up to the driver! how hard would you push the car...know what i'm mean?

Yeah, that does make sense. How much are factory cars like mine boost stock?

I do believe most stock are arond 9 psi . But since you got big money for all the extras . I have seen someone run their A/C line inline with the intercooler and push 25 psi. Its all about how cold you can keep your turbo. the colder the more PSI but more boost = more fuel and air needed

Do I need anything else for my car to make it more safe to boost higher?

bigger intercooler then the stock one

If I get a bigger intercooler, doesn't that cause more turbo lag?

i would upgrade the fuel pump atleast if you are going to up the fuel. if you get a chance dyno tune your car and see how its running. since you got rid of most of the safety features of your car, boost cut/fuel cut then you wouldnt know when you run too much boost right? i always suggest to do things right rather than getting too boost anxious.

As long as your engine is healthy it should be able to handle 15 psi on 93 octane pump gas.

If you add a better intercooler and water injection you could probably go to 18 psi safely on pump gas.

I have a T3T4 with Water injection and upgraded intercooler and I run 22 psi of boost when I use race gas. My engine has 195,900 original miles on it.

Hope that helps.

hydes car has also been blessed with holy water.

How do you know how healthy the engine is? Getting a fuel pump upgrade and bigger cooler will help it more safer? I just want to boost safe so that I can have the engine last as long as possible.

A compression check and a leak down test will give you an idea of how healthy your engine is.

The safest things you can for your engine is get a better intercooler and water injection.

If you want to boost over 18 psi, you should look at getting a controllable fuel system: larger injectors, fuel pump and some sort of fuel controlling device (SAFC or stand alone engine management).

What should the numbers be around on the compression test to know if it is good?

It is more important that the cylinders are close to each other than to be at a specific number.

The factory calls for 164 or higher.

So do you think I can boost around 12psi no problem with the mods I have now and be safe or should it be different?

if your car is not running properly stock 12psi will be too much with no mods. but assuming that your car is in good condition then 12psi is safe. = )

You think I am able to go higher boost than 12psi with the mods that I have now or will it be too much?

wow you are boost anxious eh? lol. i ran at 14psi but not constantly when i had intake, exhuast, afc, fuel pump, and avcr. that was when i was making 236whp. i am always cautious about turning up boost though. boost at your own risk. if it were me, i would run 12psi.

Yea..I am sort of curious of how much boost I can go with. How much boost am I running right now? I have the mods in, but I never adjusted the boost yet. Also, how much horsepower do you think I will get with 12psi?

Why dont you just do this, since you prefer to be safe above all else and you already have the boost controller, why dont you just set it to 10-12 psi for daily driving and raise it up to about 15-18 max when you go for a run? this way you'll be fast when you want tobe and not hurt the car as much and worrying about boost sneaking up on you.

Yea...I can run it on 10-12psi daily and 15-18psi on runs. How much horsepower will I be putting out? How much boost am I running stock?

Stock boost is roughly 7~11 psi.
Running over 15 psi on the factory turbo is not worth the risks involved.
Above 15 psi you are increasing your risk of detonation for very little pwoer gain.

If you want big boost and big power you are going to need a bigger turbocharger.

If you are really engine-safety conscious look into upgrading your intercooler and/or getting water injection.

Yea...I can run it on 10-12psi daily and 15-18psi on runs. How much horsepower will I be putting out? How much boost am I running stock?

In all honesty, talking about how much power you have from adding this and that and turning boost up this amount is kinda nonsense. What you need to do is get on the dyno to know how much power you are making and if you want to know how fast your car is then take it to the track. dont race on the street, or do anything idotic. = ) not all cars with the same mods make the same amount of power. like i said before, i rather have a reliable car than to tell someone i make such and such amount of power or that my car runs this fast.

next on my list W/I kit, Intercooler, Hotel room

Stock boost is roughly 7~11 psi.
Running over 15 psi on the factory turbo is not worth the risks involved.
Above 15 psi you are increasing your risk of detonation for very little pwoer gain.

If you want big boost and big power you are going to need a bigger turbocharger.

If you are really engine-safety conscious look into upgrading your intercooler and/or getting water injection.

I changed my stock CT26 turbocharger for a T3/T4 hybrid turbocharger done by turbonetics. Will that help my boost increase?

In all honesty, talking about how much power you have from adding this and that and turning boost up this amount is kinda nonsense. What you need to do is get on the dyno to know how much power you are making and if you want to know how fast your car is then take it to the track. dont race on the street, or do anything idotic. = ) not all cars with the same mods make the same amount of power. like i said before, i rather have a reliable car than to tell someone i make such and such amount of power or that my car runs this fast.

Yea...I should go to a dyno shop to get it tuned and see how much power my car is making. Sometimes you have no choice but to race on the street because of the other driver that pulls up next to you and just wants to start something. I just can't say no to myself when I am being challeged to a race.

I changed my stock CT26 turbocharger for a T3/T4 hybrid turbocharger done by turbonetics. Will that help my boost increase?
A T3T4 will be more efficient at higher boost levels.
They can run more boost without causingthe increase in temps that the CT26 would.
With more boost (especially from a bigger turbo) you are going to need to make sure your engine is safe for the power (tuning, intercooling, water injection, etc...)
You can safely drop in a T3T4 and run 15 psi and still have much more power than your CT26 @ 15 psi.

Yea...I should go to a dyno shop to get it tuned and see how much power my car is making. Sometimes you have no choice but to race on the street because of the other driver that pulls up next to you and just wants to start something. I just can't say no to myself when I am being challeged to a race.
That is what all of these people though:
http://jekylandhyde.madpowaz.com/streetrace.htm
Please check out that link

A T3T4 will be more efficient at higher boost levels.
They can run more boost without causingthe increase in temps that the CT26 would.
With more boost (especially from a bigger turbo) you are going to need to make sure your engine is safe for the power (tuning, intercooling, water injection, etc...)
You can safely drop in a T3T4 and run 15 psi and still have much more power than your CT26 @ 15 psi.


That is what all of these people though:
http://jekylandhyde.madpowaz.com/streetrace.htm
Please check out that link

With all the mods that I have now. Do you think I am able to do 15psi no problem?

Also, thanks for the link. It make me more wiser to know something bad can always happen in street racing. I will think about taking my car to the track instead.

Sometimes you have no choice but to race on the street because of the other driver that pulls up next to you and just wants to start something. I just can't say no to myself when I am being challeged to a race.

well you do have a choice. i was on 287 south and a 911 turbo guy was looking at me then takes off. he slows down and then i pace him. we both took off and i pulled on him. state trooper was there and i had my license taken away. its NOT worth it. who cares if some guy pulls up next to you. i have so many civic guys around here always revving at me and turning up their stereo systems everytime they see me. i jsut laugh cause deep down inside i know they wish they had my car :) on the other note, as hyde said 15psi on stock turbo and 15psi on an upgraded turbo is DIFFERENT. and yo answer your question if its safe with your mods to run 15psi. i say NO. because if we say yes and you blow something, youll be upset. better safe than sorry. if you had the stock turbo then 15psi should be ok.

well you do have a choice. i was on 287 south and a 911 turbo guy was looking at me then takes off. he slows down and then i pace him. we both took off and i pulled on him. state trooper was there and i had my license taken away. its NOT worth it. who cares if some guy pulls up next to you. i have so many civic guys around here always revving at me and turning up their stereo systems everytime they see me. i jsut laugh cause deep down inside i know they wish they had my car :)

You are right...better doing it the legal way than doing it illegal and getting myself in trouble.

on the other note, as hyde said 15psi on stock turbo and 15psi on an upgraded turbo is DIFFERENT. and yo answer your question if its safe with your mods to run 15psi. i say NO. because if we say yes and you blow something, youll be upset. better safe than sorry. if you had the stock turbo then 15psi should be ok.

So you are say that a stock turbo can boost 15psi and it should be ok? I alway thought the T3/T4 turbo is better than the stock turbo.

15psi with a small turbo is DIFFERENT than 15psi with a big turbo. you are pushing more volume at the same boost level. if you dont get it, then just keep your boost at 12psi :)

To be honest with, I really don't understand. It seems to me that you are saying that a factory stock turbo is better to push 15psi than the T3/T4 turbo. I always though the bigger the turbo is, the better boost you can get. Please explain to me in detail. I am really new to this and I really want to know how everything works. I really appreciate all the help and information that you guys are providing me.

15 psi in a 2.0 liter engine is the same volumn regardless of what turbo makes it.
The difference (volumn wise) is how much air can it flow over the entire rpm band and how hard does the turbo have to work to make it (heat).

A stock turbo may make 15 psi all the way to redline, but it's powerband drops off regardless at 5500 rpoms or so. I larger turbo will pull all the way to redline, but most likely will spool up a bit slower.

Also, the stock turbo is going to generate a lot of heat trying to make 15 psi which will increase your chances of detonation.
A bigger turbo will not have to work very hard to make 15 psi.

Think of it this way.
If Pam Anderson and and Arnold Schwarzenegger were both going to pick up a 50 lb weight ... who is most likely to struggle to pick it up and who could carry it further?

Make sense? Pam could probably pick it up, but she isn't going to be carrying very far (across the whole power band).

So is the T3/T4 turbo in my car right now okay? or Should I change it back to factory stock turbo?

There isn't any problem wiht you having a T3T4.
If you went to the OEM turbo you would have a huge loss in power.

Assuming a healthy engine, there isn't any reason you coudln't throw a T3T4 onto a stock MR2 and run 14-15 psi.

From what I am understanding is that Arnold(bigger turbo) can carry the weight all the way across the power band without a problem and Pam(stock turbo) will stop at a certain point of the power band

From what I am understanding is that Arnold(bigger turbo) can carry the weight all the way across the power band without a problem and Pam(stock turbo) will stop at a certain point of the power band
You got it.

The only part that doesn't exactly fit that metaphor is that the bigger turbo will take a slight bit longer to get going. The smaller turbo will get going sooner (in the rpms).

Think of it as Arnold is taller, so while he is spending time bending over to pick up the weights ... Pam is already lifting hers since she is closer to the ground. :D

There isn't any problem wiht you having a T3T4.
If you went to the OEM turbo you would have a huge loss in power.

If the stock turbo is pushing 15psi and the T3/T4 turbo is pushing 15psi. How is it exactly that the stock turbo will have a huge loss in power? Becasue if they both boost the same amount, shouldn't it be the same power?

If the stock turbo is pushing 15psi and the T3/T4 turbo is pushing 15psi. How is it exactly that the stock turbo will have a huge loss in power? Becasue if they both boost the same amount, shouldn't it be the same power?
Nope.

Since the larger turbo is more efficient (can make psi/power in higher rpms) it pulls the whole horsepower curve up. The small turbo is still working really hard (making a lot of heat) to make 15 psi while the big turbo is not even breaking a sweat.

Go back to the Arnold metaphor, since he is so big (more power) he is not trying hard to pick up the weight (easily) and carry it much further (more rpms).

Maybe this will help:

CT26 @ 15 psi:
http://www.turboforum.net/dyno/

T3T4 @ 15 psi:
http://jekylandhyde.madpowaz.com/hydedyno.jpg
(red lines! .... blue lines are at 20 psi)

Notice:
CT26 made peak HP at 5600 rpms
T3T4 made peak HP at 6200 rpms

At 4000 rpms:
CT26 made 150 rwhp
T3T4 made 153 rwhp .... very close at 15 psi.

At 5000 rpms:
CT26 made 180 rwhp
T3T4 made 245 rwhp .... not very close any more

i dont think the problem is will his turbo be able to handle it. i think the problem is will the rest of the car and his motor be able to handle it. run 12psi improperly and you are done for also. oh well, interesting point you made there. i always thought that with the bigger turbo you are pushing at the same psi but a greater amount of air is moving due to the larger turbo.

So even 12psi to my car is dangerous?

vsiev , as long as your engine is already healthy... 14-15 psi should be fine on 93 octane gas.

If you do not have an intercooler upgraded, I would stick around 12 psi.

I always thought a jdm motor needed a higher octane than 93. Isn't the octane in japan like around the 100's?

just to clear a few things up,

bigger turbo = more cfm = more air = more volume
so 15psi on a small turbo and a large turbo will put out different volumes of air which explains the power difference.
you "can" run whatever boost you want, the question is if your engine can handle it. some engines are in better condition and some have the proper tuning. if ones engine is crap any boost can damage the motor. the only reason i am running the boost levels i am with the stock intercooler is because of my engine. if i had a stock motor i would be stupid to run that much boost with a t67 on stock intercooler.

The volumn is key when you consider the RPM band.
The bigger turbo can keep filling up a 2.0 liter engine as rpms rise while the smaller turbo runs out of breathe (can't keep up).

At 3500 rpms, if both turbos are maintaining the same 15 psi, the volumn is the same, unless there is a temperature difference which is possible considering the smaller turbo would work harder (making more heat) to make the same psi.

The psi setting is merely a pressure setting not amount of air. Physically a larger turbine housing will have more air in it than a smaller turbo. there is simply more space in there. that is why it takes longer for the large turbos to spool, because it has to fill up all that space to create the same amount of pressure. think of it as two balloons. if you have a small balloon, you can fill it up with 15psi of pressure, and fill up a large balloon with the same amount of pressure, but the larger balloon will have more volume of air due to its size. if you let both go at the same rate(pressure) the larger balloon will be moving a greater amount of air from its biggere opening. the blades inside the turbine move and compress the air. the bigger the blade, the more air volume it is moving. wave your finger in the air, and you are moving air, wave your whole hand and you are moving air at the same rate but you are moving a larger volume of air. same with the arnold and pam anderson analogy. because of arnolds size, he is moving more air in the atmosphere than pam is moving. they are doing the same work but because of his size, his larger body is causing a larger amount of air to be moved.

the blades inside the turbine move and compress the air. the bigger the blade, the more air volume it is moving.
You are confusing terms here.
The blades in the turbine do not compress air.
The blades in the compressor, compress air.
The turbine blades are spun by exhaust and in tern spin the compressor.

At any rate, the benefit to having a larger compressor is in order to be able to maintain higher levels of boost at higher rpms.

At 4000 rpms at 15 psi, the engine is taking in the same volumn of air regardless of the pressure source. The only way that is different is if the temperature is different. The smaller turbo will make more heat.

At 6000 rpms, the flow of the larger compressor shines because it can still has the ability to fill up a 2.0 liter engine FASTER because if it's greater ability to flow ... while the smaller turbocharger has run out of air. At 6000 rpms you need to fill the engine up many, many more times per minute.

well thats what i meant about the blades. they are connected to technically the blades turned by the exhaust gasses are the same. Anyhow, larger turbos move a greater volume of air than the smaller turbo. They will be the same however depending on the set up of the outlets and the piping. if you have a large room full of people, there are more people than a small room full of people. but if the doors coming out of both rooms are the same then you will still only have the same rate and volume of people coming out. the larger will just have more people to let out.

OK, I like the room anology. :)

If you have a room that fits 200 people and a room that fits 100 people.
Each room is connected to a different room that can ONLY fit 10 people.
That 2nd room has the door to get out.

If we tell everyone to leave at the same time ... the middle room can only ever hold 10 people ... doesn't matter how big the 1st room is :D

You could have a turbo that is 10 feet tall and at 15 psi, it will fill a 2.0 liter space with the same amount of air as the ct26. ;)

LOL, this is a great debate but I am coming to the conclusion that we are talking about something that is completely different. I am talking about the amount of volume that two different turbos are moving. you are talking about how much volume of the gasses can be forced into that engine. THAT i totally agree with you :) using the room analogy again, because the larger room is filled with more people and is forcing them out at a greater force, the actual pressure volume to the middle room is greater. We are talking about two different things. bigger turbo moves more air. an engine a certain size can only hold that amount of air that it can contain. more you try to force into it though will create more strain on it.

All I wanna know, is RollHard's mods list...

309RWHP on the STOCK INTERCOOLER?!?

All I wanna know, is RollHard's mods list...
309RWHP on the STOCK INTERCOOLER?!?
Look for the thread started by me that has rollhard's name in the thread title. His mod list is in there.

lol, must i post this again?

http://www.rpipower.com/eloydynomr2.jpg

i woudl think that it is more unbelievable that jeffs car is pushing the same amount of power and we are running simular times with a stock motor and almost double my miles! that IS amazing.

I am sort of confused about what rollhard and jekylandhyde are talking about.

HEHE, It's just two guys babbling :) i think we can both agree on you sticking with 12psi though. I wouldnt recommend you running higher boost until you understand a little bit more about how this works. good luck!

The confusion probably lies in that rollhard was talking about the volumn of air the turbo can put out and I was pointing out that a 2.0 l engine can only take in so much air.

We are both correct. We just kept chasing eash other's tails pointing out the part we liked the most :)

So what do I do when it takes too long to spool up? Will I loose power when it does that?

correct me if i'm wrong but don't some b/c controll when the turbo spools up or at least make it spool up alot faster?

actually i'm almost positive some do.