Stock T3 Max Boost

[Dan15]

I'm not super familiar with reading turbo maps and all that stuff yet. But does anyone know what the max boost that a stock Spirit RT turbo can efficiently make power at?? I was hitting 25-27psi and it felt super weak, I'm assuming it's due to it being way out of it's efficiency range so it was actually making way less power than it would at a lower level. I'm waiting on my electronic boost controller and then from there I guess I'll just slowly step up and figure it out. But Any help, suggestions or info would be great. Thanks!

[rx2mazda]

Whats mods does the car have? Obviously you don't have a stock computer because they boost cut at 15psi

[Vigo]

Not sure on boost level (probably falls to ~17-20psi at high rpm if you stay in it) but with a really good intercooler it will make about 300hp maxed out.

[Dan15]

Whats mods does the car have? Obviously you don't have a stock computer because they boost cut at 15psi

Actually is a stock computer.... Has some SRT4 adjustable map sensor. It has a large FMIC, all the timing belt tension mods and the titanium retainers. Dual catch can setup. Walbro 255. +20's.. Yes on stock computer. Rich idle but helps with the higher boost. Was on it when I picked up the car.

I have a wideband and was watching it extremely close. I also had put in some race fuel because I was having some serious boost spiking issues and preferred to be safe when I was trying to figure the problems out.

Not sure on boost level (probably falls to ~17-20psi at high rpm if you stay in it) but with a really good intercooler it will make about 300hp maxed out.

Boost wasn't held at 25 psi long but as soon as it passed 20psi it just revved and lost power way bad. So i'm assuming about 20psi probably is about max for this turbo. I'll have to do some more playing around when I get my boost controller which will stop my spiking issue. I have a Forge Manual boost controller and it's a very very common problem for these to spike.

[iTurbo]

I would not bother to go past 12-14 psi on the stock turbo with the TIII..

If you want more you will need a larger turbocharger period.

[turbovanman²]

Probably around 18 psi.

[HSKR]

If there is still "boost", or the boost level doesn't level out, then it's not running out of air and the turbo wouldnt be the problem. Boost pressure means the turbo is putting out more air than the motor can take in causing a "back up" of pressure in intake manifold, the only downside would be higher charge air temps than a more efficient turbo would make. Yes there are limits, but it would usually mean that you hit a plateau of boost pressure.

At least that's my limited understanding.

[rx2mazda]

Probably around 18 psi.

+1

maybe 20psi with race gas.

That's also pushing the limits of your +20 injectors. 18psi on a stock computer(tricking the Map signal)with a good 3 inch exhaust and FMIC should be a pretty quick sedan. If you're spiking to 25-27psi then you're flirting with blowing up your motor. Stay around 18 until you have +40's and a 3bar Cal.

[cordes]

I don't want to even think about the math behind injector DC with a tIII and plus 20s at 20+PSI. Holy cow.

[Vigo]

I am guessing this 25-27psi thing was at 3-4000 rpm. If you stay in it long enough that boost will drop as the rpm goes up and the turbo is not able to maintain the same pressure at higher and higher flow levels. HSKR is right about that topic.

Right now lack of air density and race gas are probably saving your ---.

Do you have a way to watch knock counts on the computer? If not i would limit it back to 14psi and wait until you can actually watch things before really trying to push the stock turbo.

[turbovanman²]

If there is still "boost", or the boost level doesn't level out, then it's not running out of air and the turbo wouldnt be the problem. Boost pressure means the turbo is putting out more air than the motor can take in causing a "back up" of pressure in intake manifold, the only downside would be higher charge air temps than a more efficient turbo would make. Yes there are limits, but it would usually mean that you hit a plateau of boost pressure.

At least that's my limited understanding.

Not really, a turbo can put out more "air" per say but it won't make any power. When you go passed the turbo's map, all your doing is super heating the charge, even intercooled and hotter air has less oxygen, so even though you're pushing "more air" into the engine, you aren't making more power, and you could be making less and make it more detonation prone.

[Pat]

If the motor is running right and has the right supporting mods, you won't see more than 15-17 psi out of it maxxed out at rpm. You might get a big spike at lower rpm (I never saw 27 psi with mone though...maybe 24), but the boost will consistently drop with rpm as the motor ingests what that tiny turbo can put out.

If you're running a stock cal, I'd be very careful. Timing is pretty aggressive, especially around 4000-4500 and is very prone to detonate. Given that you're likely seeing the huge boost spike there, you could be asking for trouble. If I had a mishap in that rpm range, it was nearly a guarantee I'd pick up some knock which led to SBEC controlled timing retard and I'd slow down substantially. I also managed to push a headgasket or two while learning what would work.

The fastest passes I was able to get out of my stock turbo/stock cal RT was loading with race fuel and controlling the boost spike as much as possible to control knock. You will go faster and be less likely to break the motor you limit boost and control knock.

Ideally, I'd say get away from the stock cal, even if you want to stay stock turbo. It's way too limiting.

[Ondonti]

Port the wastegate passage?

Boost numbers are probably a bit off because of the high elevation. That makes it laggier and able to move even less actual CFM's.

[Dan15]

Not sure on boost level (probably falls to ~17-20psi at high rpm if you stay in it) but with a really good intercooler it will make about 300hp maxed out.

Yeah I didn't stay in it to find out. That massive spike scared me enough to pull back on the throttle.

+1

maybe 20psi with race gas.

That's also pushing the limits of your +20 injectors. 18psi on a stock computer(tricking the Map signal)with a good 3 inch exhaust and FMIC should be a pretty quick sedan. If you're spiking to 25-27psi then you're flirting with blowing up your motor. Stay around 18 until you have +40's and a 3bar Cal.

Yeah right now I'm sitting at 9-11 psi until my Boost controller shows up. That spiking up that high scared me enough to be patient ha. Not worth blowing the motor. Then I'll work up to 18psi and hopefully be able to stay there until I put on my HE351 during the winter. That'll also be when I socket my SBEC, install my 3 bar, hopefully get some +40's and setup all the data logging things to truly tune it.

I am guessing this 25-27psi thing was at 3-4000 rpm. If you stay in it long enough that boost will drop as the rpm goes up and the turbo is not able to maintain the same pressure at higher and higher flow levels. HSKR is right about that topic.

Right now lack of air density and race gas are probably saving your ---.

Do you have a way to watch knock counts on the computer? If not i would limit it back to 14psi and wait until you can actually watch things before really trying to push the stock turbo.

Yeah with how it had been spiking before I'm sure it would've dropped a lot if I would've stayed in it, but I didn't want to stay in it enough to really find out.....

Not really, a turbo can put out more "air" per say but it won't make any power. When you go passed the turbo's map, all your doing is super heating the charge, even intercooled and hotter air has less oxygen, so even though you're pushing "more air" into the engine, you aren't making more power, and you could be making less and make it more detonation prone.

That's kind of what I was thinking happened as well from what I read. I've heard other forums basically refer to it as turning your turbo into a flame thrower which completely destroys your air temps an definitely would be more detonation prone.

If the motor is running right and has the right supporting mods, you won't see more than 15-17 psi out of it maxxed out at rpm. You might get a big spike at lower rpm (I never saw 27 psi with mone though...maybe 24), but the boost will consistently drop with rpm as the motor ingests what that tiny turbo can put out.

If you're running a stock cal, I'd be very careful. Timing is pretty aggressive, especially around 4000-4500 and is very prone to detonate. Given that you're likely seeing the huge boost spike there, you could be asking for trouble. If I had a mishap in that rpm range, it was nearly a guarantee I'd pick up some knock which led to SBEC controlled timing retard and I'd slow down substantially. I also managed to push a head gasket or two while learning what would work.

The fastest passes I was able to get out of my stock turbo/stock cal RT was loading with race fuel and controlling the boost spike as much as possible to control knock. You will go faster and be less likely to break the motor you limit boost and control knock.

Ideally, I'd say get away from the stock cal, even if you want to stay stock turbo. It's way too limiting.

Well I plan to get rid of both the stock turbo and the stock cal soon. But I'm not wanting to do any head gasket anytime soon haha. So I'll probably float around 14-17 psi until then. I'm interested to see how well the EBC will control the boost spike. If it holds everything super steady like it's supposed to then I will be able to more safely up the boost until my cal is set up. Cause as you said, and as I also did, we were both using race gas as a form of boost spike insurance ha.

Curious, on those fastest passes on stock cal and turbo what times were you able to get??

[Pat]

I went 12.44 @ 110. Full weight RT on 20's, big cooler, open exhaust and slicks. Granted the weather was perfect, but the car was consistent. Went .44, .46, .44 three runs in a row.

[Dan15]

I went 12.44 @ 110. Full weight RT on 20's, big cooler, open exhaust and slicks. Granted the weather was perfect, but the car was consistent. Went .44, .46, .44 three runs in a row.

Wow that's impressive. That makes me excited to get everything running smooth on mine! What size slicks were you running?

[Pat]

23" M&H's. Short times were mid 1.7's.

This was a perfect weather/track prep day at a fast track.

[Dan15]

23" M&H's. Short times were mid 1.7's.

This was a perfect weather/track prep day at a fast track.

Well unfortunately my track is never prepped very well but I do need to pick up a pair of slicks. For now I'll be running a pair of BFGoodrich Drag Radials that are on their last leg.

[turbovanman²]

Drag radials suck in a high powered turbo FWD car. I wasted money on them,

[Force Fed Mopar]

Drag radials suck in a high powered turbo FWD car. I wasted money on them,

If you only run it hard at the track, then yeah. If you like to play with it on the road, then drag radials are the ticket. Can't ride around on slicks all the time...