Hi all,

I have some questions. Does anyone know how much boost the stock '99 twins will produce? Max? This can be controlled by a computer and boost controller like Apexi?

What is the highest boost one can run on pump gas?

Thanks

 

pump gas is only a small factor of your boost limitation. What computer are you running and what do you plan to have it tuned to. There are members running 18 psi on the stock twin (the 99'S may be capable of a slightly higher psi) if your planning on running 18 or higher for any period of time a single should be in your future. The stock fuel system is good for 14psi max (everything being perfect) and the stock ecu is good for 10psi period.

 

The boost level is controlled in the Apex'i PFC by using the stock solenoids. These are slow and are not the best choice for boost control unless you're deviating from stock by just a couple psi. You'll want a manual or electronic boost controller.

The usable max for stock or 99-spec twins is maybe 15psi. That is not a hard limit, but higher boost causes higher air intake temps. The highest power ever made from stock turbos was around 18psi IIRC, but the air intake temps were very high, it probably wasn't on pump gas, and the turbos probably didn't last long.

If you are running nearly stock power, you're going to need a bunch of fuel, intake, ecu, and exhaust mods to get to where running elevated boost is reasonable.

BTW, there are many past discussions on these exact subjects. Use the search feature, and feel free to ask/add to the past threads.

Dave

 

Thanks for your reply. I probably wouldn't want to go higher than 15 PSI. The higher intake temps would be taken care of by intercooler upgrade. You say the turbos wouldn't last long but why would running at higher boost make them crap out as long as temps were kept down and oil was cooled? I guess I just wonder why so many people go to single turbos for more power when the stocks are capable of quite a bit more and less turbo lag?

As far as searching previous threads I have tried that before but then I have to read through hundreds of posts that end up goin off on tangents/ rants about some other bull.

 

Well the stock sequential controls will work at 15psi+ if you install a pressure regulator on the pressure tank.

The temps go up both in/around the turbocharger assembly and in the intake temps. Higher intake temps mean less power and shorter engine life. Single turbo setups will flow more cfm at lower AIT than the stockers, and produce a lot less heat under the hood. Overall it's the superior setup for higher boost. If power is your goal with sequential, I suggest BNR Stage 3's. This is a really good upgrade over stock without leaving sequential land.

Dave

 

Because besides the overall assembly temps that Dave mentioned, running the turbos constantly at such high boost numbers causes major stress on the turbo shafts due to the sustained ultra-high rpm (surely upwards of 150,000 rpm or more). The stock Hitachi turbos were not intended nor designed to run at that pace for long.
Because once you venture well beyond a particular turbo's efficiency range, you begin producing more heat than you do horsepower, which ends up being destructive in more ways than one.
An unfortunate by-product of trying to research stuff on a forum. You just have to be patient and scroll past the riff-raff.

 

Thanks for the input. I will give it some thought. I am taking my car to Gotham Racing soon to have an engine rebuild/ upgrades, tune. i will talk to Steve about options. He says the stock '99s are good for 340 rwhp with the appropriate supporting mods. That's plenty for me for awhile.