Building Twin Turbo LS3 w P59 / Flex Fuel
Building Twin Turbo LS3 w P59 / Flex Fuel My shop is adverse to the P59, says it doesn't have enough secondary tuning tables for the power levels ( ~800 - 1000 WHP ) this car will be making. He really wants me to go Holley, I don't want to because:
- I already had a custom harness made for the P59 ECU and the 98 F-Body / Gauges
- I'm not a fan of the Holley Screen and want to keep my stock gauges
But is he right? am I at the limits of the P59 ECU?
- I already had a custom harness made for the P59 ECU and the 98 F-Body / Gauges
- I'm not a fan of the Holley Screen and want to keep my stock gauges
But is he right? am I at the limits of the P59 ECU?
He's wrong, it's very capable of making those power numbers. That being said you aren't going to have any sort of feedback, no closed loop control of fueling, no logging, not boost control, etc. There are plenty of reasons to switch to something else, but that power level is not a problem.
He's wrong, it's very capable of making those power numbers. That being said you aren't going to have any sort of feedback, no closed loop control of fueling, no logging, not boost control, etc. There are plenty of reasons to switch to something else, but that power level is not a problem.
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Look into TurboV6's custom P59 OS. It is MORE than capable of doing that power level, with dedicated boost VE tables, boost spark adders, wideband closed coop fueling and boost control/safety
Last edited by JonAdkins; May 22, 2026 at 06:06 PM.
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The older versions are over on PCMHacking forums for free or his Patreon has the newer ones. He has a YouTube video going over the features and on how to install it and what all is needed. Just Google LS1 Boost OS and go to the video tab, it'll be the first video. Link to the downloads are in the description.
Just remember it is solely based on the 12587603 OS, so some oddball vehicles (like my gto) are difficult to use it on. If I ever figure out how to get it to operate the fuel gauge in my IPC, I will probably switch from the HPT 2bar OS over to the BoostOs. I like the 2 step and no lift shift features, as well as the ability to pwm a mac valve based on things like TPS and alcohol percent.
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Joined: Nov 2017
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From: Kentucky
Just remember it is solely based on the 12587603 OS, so some oddball vehicles (like my gto) are difficult to use it on. If I ever figure out how to get it to operate the fuel gauge in my IPC, I will probably switch from the HPT 2bar OS over to the BoostOs. I like the 2 step and no lift shift features, as well as the ability to pwm a mac valve based on things like TPS and alcohol percent.
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edit-- That is what I am currently running in mine.
That's up to you, but it sure sounds like the shop you are dealing with doesn't want to deal with the P59 regardless. I've watched the development of the Boost OS over the years and it's a nice mod for the OEM computer and works well enough for somebody who likes to tune their own stuff and not spend the money on an aftermarket computer. That being said no shop is going to tune a P59 with that OS mod so unless you plan on doing it yourself you get to do whatever somebody else is willing to tune for you. An aftermarket computer has so many advantages over a P59 computer even when using the Boost OS so keep that part in mind. I'm not a Holley fan even though I've tuned more of them than I can count over the years, I would much rather run a Haltech Rebel and if you want to keep the factory gauges that means you get to piggyback it.
That's up to you, but it sure sounds like the shop you are dealing with doesn't want to deal with the P59 regardless. I've watched the development of the Boost OS over the years and it's a nice mod for the OEM computer and works well enough for somebody who likes to tune their own stuff and not spend the money on an aftermarket computer. That being said no shop is going to tune a P59 with that OS mod so unless you plan on doing it yourself you get to do whatever somebody else is willing to tune for you. An aftermarket computer has so many advantages over a P59 computer even when using the Boost OS so keep that part in mind. I'm not a Holley fan even though I've tuned more of them than I can count over the years, I would much rather run a Haltech Rebel and if you want to keep the factory gauges that means you get to piggyback it.
I guess Im not worried about a computer failure. I 'really' want to stick with my P59 as I have a custom harness built to integrate it between my LS3 and 98 F-Body... I am worried about the fuel gauge in either route but I think there are work around to get it to work. I don't wanna fork over another $2k for a harness and ECU but there is one thing that is appealing, It can interpret x58 wheel reluctors without an additional ligenfelter computer. I think that part does make me feel more comfortable under boost. That stated I know this shop is basically dodging the P59 because they don't feel comfortable tuning it but meh. Maybe I could get a base tune from a vendor and drive it to another shop for a better dyno tune.
You just added a new variable to the situation. A 58x converter box is $300 that could go toward an aftermarket computer. When added to the roughly $500 that you would need to spend on HPtuners to tune the factory pcm, you are most of the way to a Haltech rebel. This would definitely change the calculations in my head. Considering Nic is absolutely right about no commercial shop using some of the hobbyist software we were discussing earlier, there would also be the cost of addons like a boost controller and 2 step that could push your cost of keeping the p59 over the price of a Haltech.
You just added a new variable to the situation. A 58x converter box is $300 that could go toward an aftermarket computer. When added to the roughly $500 that you would need to spend on HPtuners to tune the factory pcm, you are most of the way to a Haltech rebel. This would definitely change the calculations in my head. Considering Nic is absolutely right about no commercial shop using some of the hobbyist software we were discussing earlier, there would also be the cost of addons like a boost controller and 2 step that could push your cost of keeping the p59 over the price of a Haltech.
Could I keep my stock gauge cluster? I wasn't really a fan of their digital clusters -- although I technically am in process of seeing what it would take to design my own cluster with homage / style of F-Body gauges but mostly digital (possibly physical Speedo and Tach - not sure yet.. ..I'm teaming up with some vendors to see what we can do. What makes F-Body clusters hard with digital LCD's is how curved it is - I would either have to oversize it and see if I can get it to fit in the dash, or have custom LCD's built $$$...)