Safe boost after 1GMAS

[ColdScrip]

When my car is finished it will be rolling out of the shop with a MBC and a 1GMAS. It will not have an A/F ratio gauge or an EGT gauge - thus no way to monitor my fuel mixture.

 

My question is, throughout the experiences people have had here what is a safe operating boost level with a 1GMAS installed? 14lbs comes to mind but I want to make sure.

 

Stock turbo

Walbro 255 fuel pump

Replaced all fuel filters as well as cleaned all fuel lines.

No fuel leaks and stock injectors with new clips.

Forged bottom end

[scott87star]

Safest boost is no boost at all. That being said and seeing that you've got a stock turbo I'd stick with the maximum Mitsubishi allowed, 7.5-12 lbs. They had a whole team of smart guys making the turbos, engines and cars. Changing the MAF sensor doesn't change the efficiency range of the turbine or the compressor.

 

Scott

[ColdScrip]

Hmm I was under the impression that a 1GMAS was a direct upgrade because it told the ECU to add more fuel. Thus you could "safely" raise your boost because of the added fuel. So you are saying a max of 12lbs?

[on4now4]

i run 15 just fine and i have herd of people running 18 on a stock turbo but i don't think i would go above 14 without a af gauge maybe 15 on occasion when but not on a daily basis. although with that fuel pump i'm pretty sure you should be fine up to 18

[89PalermoSHP]

a forged motor and no a/f gauge?? the aem uego is just over $200.

[Technology]

A million.

 

Seriously, with everything stock and a 1G mass air sensor, you can unplug the wastegate. Run 30 psi if you can, then your problem won't be the mass, it'll be the injectors and fuel pump. But talk about a waste of money, you're flushing it right out the tail pipe. 1G mas runs pig rich. Go with a stock mass air sensor, 19psi and a slightly upgraded clutch.

[JAinsworth]

Without a wideband O2, I wouldn't run over the 14~15 range. Even that would depend on the age and condition of the engine. Are you running head bolts or ARP studs.

Jimmy

[Dad]

Arp Studs on that engine...FWIW I did not raise any boost levels until i installed a wideband.

 

 

Also Coldscrip already had a 1GMass, so no $$ wasted.

Dad

Edited December 18, 2009 by Dad

[pitboss]

It's been my experience that the 1G MAS allows better and more aitflow (especially if you remove the upper honeycomb) than the stock MAS, in the stock air can. The stock MAS runs pig rich from my back to back tests lol. With the stock 12A and stock injectors and good fuel system you can run pretty nice, but the air just gets real hot (and the smallish intercooler doesn't cool it enough either), and so does the spark since most run tight gaps. I'd say you could probably run up to 16, maybe up to 17 psi, if you open the gap up a little (maybe to .040?) and the injectors have been cleaned and flowed. I used to have my 12A up to almost 20 psi and it ripped everywhere and didn't detonate, but that was with a TB pro2 and 52mm. The ECU and injectors throw alot of fuel. I'm presently at 21 psi on a 14G with stock fuel system, and a small shot of alky above 8 psi.

[jettajody]

I think with a decent stock setup, you could run a safe 15-16 PSI. If you had a wideband you could just turn it up little by little until it either knocked or started to run lean. After 16-17 PSI these 12A's start huffing hot air, however some people say boost is boost. You can bet though that on those higher level PSI's the turbo will end it's life that much quicker. Do you have a BOV? Compressor stall on high boost levels will kill the turbo that much quicker to.....

[StarquestRescue]

a forged motor and no a/f gauge?? the aem uego is just over $200.

Your a techie guy. Get one you can data log with. There was a good deal on The Innovated WB in the GP section.

 

Just start at stock and work the boost up a little at a time. Over 14 think about a bigger turbo.

[dstar88]

14-15 lbs is good on a 1g. but with no af monitoring. keep it low like everyone els is stating.

 

 

 

 

 

Daniel

[ColdScrip]

Car came with a 1g connector spliced in as well as a 1gmas. Being how a MAF-T requires a 1g harness connector I figured it would be a waste to splice the old one back in.

 

ARP studs, BOV of course, after reading the replies I plan to run no more than 14 PSI. If I want more than 14 it will be with a wideband, a way to monitor the fuel like a MAF-T, and a larger turbo.

 

Technology is the difference really that much fuel? It would be interesting to see the my MPG at 14PSI.

 

I suppose if I really wanted to I could use the 1g harness on a stock MAS if I bust the plastic side of the stock MAS connector off. Sort of the opposite way most people install a 1GMAS. Thus I wouldn't be "stuck" with this 1g.

 

The car is not going to be a DD and will be upgraded with a turbo and such later on. So losing some MPG is not a real big deal atm. I am much more interested in protecting my investment (engine).

 

a forged motor and no a/f gauge?? the aem uego is just over $200.

 

Didn't plan on raising the boost until an AF gauge was acquired. Given my 1gmas situation I felt that if it was pretty much proven that 14 PSI was safe on a fully functional stock fuel system w/ a walbro 255 that I could go that route without worry. Hence this thread to see how "proven" this club has found this upgrade to be.

 

Your a techie guy. Get one you can data log with. There was a good deal on The Innovated WB in the GP section.

 

Just start at stock and work the boost up a little at a time. Over 14 think about a bigger turbo.

 

That WB actually fits my build very well. When the time comes I will get that.

 

A million.

 

Seriously, with everything stock and a 1G mass air sensor, you can unplug the wastegate. Run 30 psi if you can, then your problem won't be the mass, it'll be the injectors and fuel pump. But talk about a waste of money, you're flushing it right out the tail pipe. 1G mas runs pig rich. Go with a stock mass air sensor, 19psi and a slightly upgraded clutch.

 

 

If the 1G dumps that much fuel then I may switch to a stock MAS given my MPG. You are also saying a stock MAS and fuel system can support up to 19PSI?

Edited December 18, 2009 by ColdScrip

[Technology]

Well, my car was funny. With the stock setup, it would hit fuel cut at 20psi like clockwork, except when I was in florida on the dragstrip. I don't know why, but maybe there is a full throttle closed loop mode, but I never hit fuel cut on the track even with the WG disabled. Strange but true. You could get a nice boost controller and go up in 1 or 2 psi increments up till you start noticing negative effects, like boost dropping as rpm climbs, or fuel cut.

 

The other thing to consider is that the 12a can only make about 20 psi, and with a big cam, higher compression pistons and all that, it will go higher, but not by much. TainterRacing said he had one up to 25psi. Why even use it if you are trying for that much? The only reason would be for the 12a/TBI record in the 1/4 mile or dyno numbers. So, back to my point - if it only makes 20psi, even with a 1G mas, why even change to the 1G if you are going to keep the 12a and drive it? Well, it may add a bit of power, but so would adding a pound of boost. It's also not some exact tuning science with the stock setup. You can change the boost more on a stock conquest than almost any other vehicle ever made with a turbo.

 

Back a few years ago when widebands were almost unheard of, we were driving around with the wastegate unplugged, a 1G mas, and a 3" exhaust and it was super fun. goodbye clutches!

[StarquestRescue]

You can down load Logworks here. http://www.innovatemotorsports.com/support.php And view some of my Logs here. http://www.innovatemotorsports.com/forums/showthread.php?t=11657

 

Click on channels and turn some off so you can get a good look at the hz out put of different maf sensors.

 

Some screen shots here, Including one of a "fuel cut moment on a stock mas" http://www.starquestclub.com/forum/index.php?showtopic=92126

[mikec]

Turbocharger compressors have a given airflow rate (CFM) and pressure (psi) where they are most efficient. Move off that point and efficiency drops. The 12a compressor wheel wasn't designed for anything above 15psi; if you really push it you're doing 2 things:

1: to make boost pressure, the turbo has to spin fast... more boost and/or more airflow mean higher turbo RPMs. Going well above stock boost levels requires the turbo spin faster than it might be designed for. It certainly does increase the internal stresses, shortening the turbo life.

 

2: when a compressor wheel operates outside it's efficiency range - especially when it's pushed to ABOVE that range - the "lost efficiency" manifests itself as heat. Basic physics/thermodynamics states that when you compress air it's gonna warm up too; that's why StarQuests have intercoolers. Any inefficiency of the compressor wheel though means energy is being wasted... wasted to where? Guess: to extra heat in the air being compressed! So the air going into your intercooler is double-heated by operating at mega-boost.

 

Rather than dialing a 12a compressor wheel to beyond it's design point, consider a larger turbo. Either something designed for more boost pressure, or better yet something designed for more CFMs too. You still need a way to verify your fuel system can keep up with all that extra air though: the 1G MAS is just part of that job. A healthy fuel pump, healthy injectors, etc. are necessary. A wideband air:fuel gauge setup is the least expensive way to make sure you're not leaning out which can destroy the pistons/motor. The -14g (I think it was "g" anyway) wheel was a dealer bolt-on option for the later model StarQuests so that should be safe on a bone-stock car. The -16G or "big 16" compressor wheels really wake up a StarQuest but they will overtax a less-than-100% fuel system.

 

mike c.