Max Boost on Premium Fuel

[DoubleD]

I am curious what you guys are getting for max boost on Premium Fuel. I have a 92 IROC R/T, T3, holset, all the other mods. With the right size injectors how boost can you safely run in your experience? At what point will the motor start knocking. I do not want to add Alcohol Injection yet, I want to know how much boost you can safely run before detonation. I have everything else to support fuel. I am looking at EVO 8 injectors, they flow 580-620cc at 43.5psi. I want to know if I'll see a performance gain or is this motor close to detonation with the +40 injectors at a high duty cycle.

[86Shelby]

I have ran as high as 22 psi on 91 octane with no knock retard. Normally keep it around 19-20 though.

[rx2mazda]

I am curious what you guys are getting for max boost on Premium Fuel. I have a 92 IROC R/T, T3, holset, all the other mods. With the right size injectors how boost can you safely run in your experience? At what point will the motor start knocking. I do not want to add Alcohol Injection yet, I want to know how much boost you can safely run before detonation. I have everything else to support fuel. I am looking at EVO 8 injectors, they flow 580-620cc at 43.5psi. I want to know if I'll see a performance gain or is this motor close to detonation with the +40 injectors at a high duty cycle.

It has more to do with your calibration than the amount of fuel you can throw in the cylinders. If your running a stock cal, I would say around 21psi before you start recording knock. FWDp cal has safer timing and I think I got to 23-24psi before I started getting knock. You can use race gas and go higher.

Keep in mind that all motors are different! Too many variables to say when your motor will start detonating(compression, spark plugs, timing advance, intercooler efficiency, blah blah).

[DoubleD]

Carroll,
That makes sense and that is what I was kinda figuring. Every car is different and there are many variables. I am currently running a stage 4 FWD tune. 255 HP Pump, +40's. Ported Intake, head, and exhaust. Holset, large FMIC. I am planning to switch the car over to boostbutton and install a turbonator tune. I will tune the car myself. I have a brand new knock sensor and a excellent wideband. I am going to set the boost at 18 psi and then start raising the boost electronically, slowly and watch the wideband. I will tune it so it is safe. I have heard with a good FMIC and keeping the intake temperatures low with the Holset, I should be able to reach 22-24 Psi. This will just have to be some trial and error. I was just looking to see what people's set-ups were and what they were capable of.

[rx2mazda]

Sounds like a healthy build! Do you have any experience tuning? I would suggest if your doing your own cal that you start lower than 18psi(a lot lower)and bring the boost up 1-2 psi at a time. You gotta remember that our stock computers and knock sensors are 1980/90s tech so they are not very fast and won't save your engine if spontaneously detonates at high boost. But, if you start low and slow, it should keep you safe. Keep us posted!

[DoubleD]

I have 4 years of engine tuning in college with 4 stroke turbo engines and one of my good friends from school is a calibration engineer for a power sports company with may years before that at a diesel company, tuning a car for power is easy for him and he has told me.

I would start lower but my holset waste gate actuator wont go any lower. I am going to start with shelgame's turbonator tune that has ran on many cars with +40's and 3 bar map. Going with the flashable chip and USB cable I will take that baseline and tune my car from there. Then I will swap in 1000-1200cc injectors and scale the tune and then work to get those happy on Premium at 43.5 psi base pressure. Then I will go on to retune for E85. My final goal is to have a great premium fuel tune and a great E85 tune. I have a dedicated notebook PC for the car. I want to be able to eventually switch fuels and switch tunes between E85( Race) and Premium (street) tunes. I will try and get a weak little 7 psi actuator on there to start tuning. I know the stock (not holset) actuator will only hold 15-18 before blowing open.

Before I do all this I am going to run the car in the spring on the FWD tune and see what the FWD tune will run for boost on this set-up. This will give me a baseline of what I should be able to do with a tune at a minimum.

I do have an idea for a wastegate actuator that will be able to open as low as 7 psi, but also hold solid above 25 psi, but that is a discussion in itself. I do a lot of research and by day I am a mechanical engineer/ designer so my brain never stops thinking of new ideas.