3sgte boost, how much Options

[6g25th]

I have a 95 3sgte that will be going into my car very soon and I was wondering what the max boost pressure is that the engine can run on. I though I saw somewhere that you can run the engine on 15psi comfortably and that is the max boost, but maybe I am wrong. Also is it safe to run the engine on 93 octane or do you have to use 103?

[woosey]

i really wouldn't run it on 93!

1 bar is usually ok as a peak for day to day driving if your not planning any other mods.

[jason]

93 should be fine, get a good tune when your done

max boost pressure is determined by how many supporting mods you have on the engine -or- how fast you want to blow it

its not good to use more fuel as a crutch to 'safely' run more boost so upping the octain and maps is not the best route to follow

id leave the boost levels alone until you know what is good. imo anything over 8psi is not suitable for daily driving and should be saved for the weekends

This post has been edited by jason: Jan 2, 2008 - 8:56 AM

[Supersprynt]

Depends on your cooling. What kind of intercooler are you using? The better cooling the more pressure you can run.

I wouldn't use anything but 93.

[woosey]

Depends on your cooling. What kind of intercooler are you using? The better cooling the more pressure you can run.

I wouldn't use anything but 93.

you are talking about 93 ron fuel yeh?

well the st205s map will be designed for the fuel it has in its native country, so if you have a UK import 95 ron or if its from japan 99 ron.

therefore its a REALLY bad idea to run a car like that on a low ron fuel unless you have the map adjusted to take this into account.

with 93 ron you will be down on BHP by quite a way too (239BHP for 95 ron and 255bhp for 99 ron, so roughly 4bhp per ron, so between 93 and 103 thats 40bhp!

If your stock map thinks its getting 95/97 and you put 93 in your really leaning out your fuel mixture.

[Supersprynt]

No I'm not speaking RON. Here in the U.S. we use PON which is the average of RON & MON.

Here in the northeast, 93 is the highest available octane, 87 is the lowest. You have to adjust your thinking to a different set of standards.

[woosey]

No I'm not speaking RON. Here in the U.S. we use PON which is the average of RON & MON.

Here in the northeast, 93 is the highest available octane, 87 is the lowest. You have to adjust your thinking to a different set of standards.

ah ok, not sure how that works then!!

[phattyduck]

No I'm not speaking RON. Here in the U.S. we use PON which is the average of RON & MON.

Here in the northeast, 93 is the highest available octane, 87 is the lowest. You have to adjust your thinking to a different set of standards.

ah ok, not sure how that works then!!

LOL... you take the RON rating, add it to the MON and divide by two.

Really though, US 93 octane is equivalent to something around 97-101 octane by the straight RON. I don't know the exact conversion.

I run a JDM '95 ST205 motor on US 91 octane fuel (highest available in California) and only have minor problems with hesitation from low octane (even at 17lbs of boost). The knock sensor does a pretty good job of pulling timing when necessary and I've never gone into safe mode from detonation (nor heard any).

-Charlie

[lagos]

as long as you have proper intercooling and 93 octane, you should be able to run 15psi. You may find that on some cars you can run more then that or less. It all depends on what your a/f ratio looks like and if everything is working like it should. The only real way to find out what YOUR motor can do, is to slowly turn the boost up on a dyno while keeping that a/f ratio in a safe range.

[Dr_Tweak]

Keep in mind that a good free-flowing exhaust is important too. Try not to run more that 12psi until a car has a 3" mandrel-bent exhaust and a high-density intercooler. Then you're good for 16, 17psi a little more if you're running an ST205 or ST215.

I know this one guy (not a swap I did) who is running an ST205 engine in his MR2, good supporting mods and stock turbo, running 20psi and 300+whp. Been running for a few years with no major problems.

-Doc

This post has been edited by Dr_Tweak: Jan 2, 2008 - 7:39 PM

[2slow2nervous]

i have a 3sgte in my car and have a fmic and 3inch mandrel bent exhaust and have been running 16 for a while now. Have no problems at all and running on 93. Car runs great and is very quick.