Hey. You broke into my garage.
That is less peak boost than an APR stage 1 for the IS12.
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It has better timing though. Timing is a lot like stock where the APR timing is down 6-8 degrees at peak boost
Why must one use a JB4 instead of a JB1 to control an IS20?
Can't you set your boost to whatever levels you want with a JB1 on Map6?
Only up to a point. You reach a ceiling that is below the point where you're really taking advantage of the bigger turbo. With the, JB1 you are limited to like 5 or 6 over stock boost request max. The is20 can go another 5 or 6 or more over that, or more if you have a tight full mod setup. 2-4 is a good starting point.
The limit is a safety so people don't try hitting 30psi @ 7000 and make shrapnel.
And even if you could do something with the JB1, the JB4's extra authority over boost control and AFR is important for safety, power and driveability.
To get the best answer on this, ask George directly, or wait for him to chime in.
Can't you set your boost to whatever levels you want with a JB1 on Map6?
I my opinion based on experience:
If one were to put an is20 and run max jb1 settings, they would probably pick up some hp. Especially top end as the is20 is blowing more cfm, cooler, more dense are at the same settings.
But. To get the real benefit of the bigger turbo and be safe, the JB4 is what you need. It has more control and control authority over the key parameters you need to make the bigger turbo work. Most importantly the ability to bring boost up to levels above is12 tune.
Why must one use a JB4 instead of a JB1 to control an IS20?
I agree with Ton's comments. BMS has also never supported the IS20 with the JB1, so there are obviously reasons for this. If anyone were to run the JB1 with an IS20, I would only run the stock map or very modest settings (+3) as a temp solution until it was upgraded to the JB4. The JB4 upgrade is only $125, so in the grand scheme of things, it would be silly not to do things properly.
Why must one use a JB4 instead of a JB1 to control an IS20?
OK, next question...
How many different "maps" am I going to have to set and run? I drive this car daily, year round, in the Northeast. So it sees below 0 degrees F in the winter and it sees 95 degrees F in the summer. Will I need a separate "map" for various times of the year?
What about octane?
My ideal situation would be to dial it in to my liking and leave it alone. It is not something I want to, nor have time to constantly log/tweak/optimize, like a lot of the more knowledgeable members on here. It is also not something I want to constantly have to monitor to feel comfortable driving around.
If I don't sound like a "good fit" for a JB4 to you, you won't hurt my feelings if you let me know.
BTW, the IS20 has arrived.
What is the best gas you can commit to run? This is the question for every tune.
Realistically, 91....solely.
93 is barely available around here and E85 is not.
Perhaps I might run 100 octane for the 1/4 mile track.
So extreme temperature change is not an issue? I thought it was.