Sponsored

jb4 or MHD w/ just 91 octane?

aakim89

New Member
Joined
Dec 30, 2024
Threads
2
Messages
2
Reaction score
0
Location
San Diego, CA
Car(s)
m240i b58
Anyone who has experience with both, would it be worth it to go MHD with just 91? Maybe even a splash of e85 on occasion? Located in Vegas with ACN91 so I'm debating if it's worth the unlock + MHD or just Jb4.
Sponsored

 

razorlab

Well-Known Member
First Name
Bryan
Joined
Oct 2, 2021
Threads
29
Messages
8,776
Reaction score
17,216
Location
NY
Car(s)
Not a Corvette.
91 will đź’Ż be better with actual timing and fuel control with MHD.
 

jmikes

Well-Known Member
First Name
Jake
Joined
Jan 2, 2025
Threads
0
Messages
457
Reaction score
647
Location
Tampa Bay, Florida
Car(s)
2021 3.0 Premium Silver
JB4 doesn't do anything except spoof the boost and wastegate readouts to trick the ECU into targeting more boost than it should. Because of this, the gains are very minimal with 91 as it isn't good enough fuel to properly support boost levels above stock; some people have even reported lost power and throttle closures with 91 on a totally stock Supra.

100% go MHD. You probably won't get a ton of extra power off 91, but it will still be way better value for your money and feel way smoother. And comes with the benefit that if you ever push further with a bigger turbo you'll already be unlocked.
 

SupraEffective

Well-Known Member
First Name
Alan
Joined
Apr 20, 2023
Threads
15
Messages
176
Reaction score
141
Location
Los Angeles
Car(s)
GR Supra 3.0 2022
Might be a dumb question, but I’m going MHD route too like OP is and we only have 91 here in California. Do I need to upgrade my spark plugs to the NGK plugs a lot of tuners recommend, or are stock ones fine?


I’m about to do my spark plugs soon and just want to be ready.
 

nanaisu

Well-Known Member
First Name
Ronnie
Joined
Jul 2, 2024
Threads
1
Messages
252
Reaction score
313
Location
United States
Website
bananaisu.com
Car(s)
2022 Supra 3.0 Premium
Might be a dumb question, but I’m going MHD route too like OP is and we only have 91 here in California. Do I need to upgrade my spark plugs to the NGK plugs a lot of tuners recommend, or are stock ones fine?


I’m about to do my spark plugs soon and just want to be ready.
On a custom 93 tune, tuner hasn't said anything about needing to "upgrade" plugs, or gap them differently. Stock should be fine for quite a while.
 

razorlab

Well-Known Member
First Name
Bryan
Joined
Oct 2, 2021
Threads
29
Messages
8,776
Reaction score
17,216
Location
NY
Car(s)
Not a Corvette.
No need to change to different plugs. I run OEM plugs, OEM gap at 600whp+ and 30psi.
Sponsored

 
 








Top