Max safe boost? [Merged 10-6]

[Turbolaser]

Is it safe to do the boost contol solenoid mod on a stock 1G?

 

[StyleElements]

you can have 2 cubic inches of air pressurized to 14 psi, or you can have 20 cubic inches of air pressurized at 14 psi. which one is more air? psi is an easy way to tune, because you know when your turbo goes out of its efficency range, and you know how many psi from whatever turbo you are tuning your motor can handle. yes a smaller turbo will generally be less efficient as far as heating up the air is concerned- a bigger turbo will allow higer psi while maintaining its efficiency.. but that is certainly not its only benefit, its also shoving a lot more of that pressurized air into the engine. compressed to the same psi, but a lot more of it.

I know this is going against what I first said, but when I really think about it ... air molecules that are unpresurized, have a certain space between each molecule. When you pressurize air, you’re forcing the molecules closer together, and the pressure itself is the force at which the molecules are trying to return to their normal spacing. Psi and volume IMO cannot be different. If there is a greater volume of air in the same container, there are more air molecules. The more air molecules there are, the more space they take up, causing molecules to be closer together, raising the pressure. 14 psi is backpressure in the manifold. 14 psi can be only one amount of volume. In the time the intake valve is open in each cylinder, only so much air can be pushed into the cylinder in the short amount of time the valve is open. The air that cannot fit in the cylinder before the valve closes is manifold pressure. So as boost is being pushed through the motor, it raises manifold pressure, forcing more air into the cylinder before the valve closes. At WOT, a greater volume of air HAS to raise manifold pressure, because the intake manifold is acting as a container for excess pressurized air that cant fit into the cylinder yet. bottom line is you can not have a greater volume of air at the same psi. This may or may not be correct, i thought long and hard about this, and i came to my own conclusion. but i think it is correct.

 

[saw wave analog]

im not going to pretend that i am well versed in turbo theory, im not, but put it like this- there is a reason that people run 3" intake and intercooler piping with huge turbos, because there is more air going through at the same psi's that a smaller turbo would push. you guys are basically saying that 14 psi is 14 psi, regardless if you have it in a huge room sized industrial air compressor or a little portable one. its not the same thing. 14 psi IS 14 psi, meaning that in any given square inch of space, there are 14 pounds of pressure. the difference is that a bigger turbo is capable of pressurizing twice the amount of air to that psi. the pressures are the same obviously, but the amount of air that is pressurized is greater. this is the reason a t76 has inlets and outlets that are bigger than a t25, because more air is flowing through. if your arguements were true, you could have an intake path the size of a pencil and as long as there were 14 psi inside of it the engine would make the same power. engines are air pumps, the more air they are fed, the more fuel they can be fed and the more power they make. a bigger turbo increases the lbs/min of air that can be forced into the engine, thats why 10 psi on a 50 trim will beat the crap out of 10 psi on a 13g. 10 psi is well within each of their efficiency ranges, the intake charge temp difference between the two would be negligible, but a shit ton more air would be coming out of the 50 trim, even though its still only pressurized to 10 psi.

 

[StyleElements]

Well I stand corrected once again. After lots and lots of research and talking to smart people, I have come to this conclusion. You can have a greater volume of air at the same psi. Air molecules aren’t stuck together in a rigid fixed manner there always moving, sliding past each other and what not. The greater the air temperature, the faster the molecules are moving. If you keep the volume the same, say you start with a 10 ci bottle at 100 degrees, and you cap it off, you would have 14psi because that’s what air pressure is normally. Double the thermal energy, i.e. raise the temperature, you will double the pressure to 28psi, with the same actual volume of air, and the same actual number of molecules. After you cool the bottle off, the pressure will return to 14psi. That’s why colder air makes more power at the same pressure ratio. The colder the air is, the more air that’s actually there. If you double the volume of air with out rising the temperature in the same 10 ci bottle, you can have twice the volume at 100 degrees at 28psi.

 

[saw wave analog]

word. thats the efficiency benefit, not to mention you are still pushing a lot more of that pressurized air into the engine with a bigger turbo..

 

[2DSMs]

To answer the original poster's question about what is a safe/efficient boost level for the 13G, I would have to say 15 psi based on what I've experienced with my wife's 91 Laser.
The 13G still made more power at 17 psi than at 15 based on my timeslips. It's also less laggy at 15psi than at stock 10.5 boost level. With the logger I found the 390's to be at 90% IDC's at 15 psi. I have a rewired stock pump. I suggest that if you want even more zoom zoom from your 13G that you should port out the manifold, exhaust housing and O2 housing. Made a big difference. Otherwise, step up to the 14B/16G and be done with it.

 

[DSMeclipse4G63]

a 13g and 14b at b12-13psi will not feal anydifferent. Its not until you start reaching the limits where you start to notice a difference. I.E if you run 15psi or more youll notice a difference there, but lower boost that is going in at the same temp will act the same. Its the fact that at 15psi the 14b isnt struggling as much therfore flowing more dense air making hp.
Andrew

p.s my big 16g at 8psi(before I re installed my mbc) felt very compareably to my t25 at around that psi. now that is of course reletive comparison as I had a few more mods at the time then when I had my t25 at that level. but all in all with the same mods there wouldnt have been a difference, except in spool.

 

[91Bomb]

a 13g and 14b at b12-13psi will not feal anydifferent. Its not until you start reaching the limits where you start to notice a difference. I.E if you run 15psi or more youll notice a difference there, but lower boost that is going in at the same temp will act the same. Its the fact that at 15psi the 14b isnt struggling as much therfore flowing more dense air making hp.
Andrew

p.s my big 16g at 8psi(before I re installed my mbc) felt very compareably to my t25 at around that psi. now that is of course reletive comparison as I had a few more mods at the time then when I had my t25 at that level. but all in all with the same mods there wouldnt have been a difference, except in spool.

Exactly as I was saying -) Although at 14psi I'd want to be using the m/t cams to help with the added air flow. BTW, can anyone who swapped to the m/t cams while using the 13g tell me what positive/negative results they've noticed with that set-up? Also, are the 1g m/t cams the same as 2g cams? (a/t and m/t)

I still haven't found out though at what the highest boost level the 13g is still operating at peak efficiency right before it starts to become inefficient. I have a map of a 13g but don't know how to read it. By using a logger and a real boost gauge could you indirectly determine this?

-Greg

 

[ruf_round_edges]

Hey everyone, with the mods I have listed in my profile and running a race gas/93 octane mix, what would be a safe boost ceiling? I want to push the car but I don't want to go overboard. I've never taken a car to the track that is not naturally aspirated, so I'm a little new to this sorda thing. Thanks for the help.

Will

 

[L2RTSiAWD]

Noone can tell you. Every car is different. You have to tune for that mix and findout what the max boost it your car will run before it starts to knock.

 

[evolvingGS-t]

Are you using any studs in your block/head? If not, then it wouldn't be a good idea to go above 21-25lbs.

 

[L2RTSiAWD]

Nevermind what I said.

With no fuel mods,logger,AFC I wouldn't run anything above 15psi.

 

[98TalonTSi]

1.21 jigawatz!!
Just kidding...Agreed with L2R, you have no idea what's going on inside, so 15 psi would be safe, but even so, a few track runs will tell you what? How fast you are, but you won't know where to go from there..

 

[ruf_round_edges]

Oooops, I forgot to put that I have a logger in there.

 

[L2RTSiAWD]

Well if you have logger start at low boost(15psi)

Run a log. Make sure you IDC is good and you have no knock.

once you start seeing some knock or you IDC gets to high back off the boost a pound or 2.

Since you have no pump,afc,injectors you may not get more than 15lbs.

 

[Ludachris]

Big16g and no fuel pump/injectors? Get yourself a 190lph pump and some 550's at least, and do the fuel pump rewire mod.

Without that, I wouldn't run anything over 14-15psi. You'll probably hit fuel cut anyway. Watch that knock sensor too.

You'll eventually want an AFC so you can start tuning it.

 

[kgtalon95]

Hey guy I have a completely stock 6-bolt with 105,000 on it. I have a b16g and the rest of the mods are in my profile. What are safe boost levels I can run w/o arp headstuds? I really wanted to run 20psi since anything above that on a 16g is pretty much useless.

 

[CYCLONE]

I was told 25 is the limit, at which your tuning must be perfect.
Past that you are risking blowing a headgasket. I would really not
recomend running it that high for a long time. Sooner or later the stock
bolt will strech. I ran 23-24psi for a couple of months before putting the ARPs
in. So I think you are safe at 20psi. Also the ARP install only takes about
1 1/2- 2 hours. If you do ever decide to install them.

 

[kgtalon95]

Awesome!! Thanks thats what I wanted to hear I figured i'd be ok since everyone seems to have a b16g these days! Thanks for the help!

 

[Gsxy99]

What about the amount of psi with a 2g eclipse, stock motor, 57 trim garret kit turbo setup, 660cc injectors, with arp head studs and 272/272 cams. I have DSM link if i get tuned very well, how much psi would be safe

 

[Defiant]

"Why are DSMs so unreliable?"

 

[CYCLONE]

What about the amount of psi with a 2g eclipse, stock motor, 57 trim garret kit turbo setup, 660cc injectors, with arp head studs and 272/272 cams. I have DSM link if i get tuned very well, how much psi would be safe

With headstuds your limit is the bottom end. I would say about 20psi on pump,
and about 25-26 on race. At this point the stock 2G rods are the weak link.

 

[jonseclipsegs]

mods are in profile, basically a big16g w/ supporting mods. i just fixed my stutter problem with a set of new plug wires and im running good. tuning using my avcr and safc i have it set at almost 18lbs and i can run perfect with no fuel cut or anything. only question is that i bought this car used and im not sure on what fuel system is in it. am i safe running this high of boost since its not showing any problems?

mods:
Evo III Big 16g, Greddy FMIC, Greddy Type S, Greddy UICP and intercooler piping, Injen Intake, Full 3" exhaust (no cat), 1g Intake Manifold, Fluidyne Radiator, ACT 2600, Neurospeed Short Shifter, SAFC, AVCR, Boost & A/F gauges.

 

[DSM90AWD]

With a stock fuel system you are prol ok at 18psi with your setup, though I highly recommend picking up one of those low-cost eBay dataloggers and check timing advance (indicator of knocking) and Injector Pulse Width / DC to see how your injectors are performing.

Obviously you should physically check to see if your pump has been upgraded/rewired and what injectors you have as this will give you some add'l peace of mind

 

[jay_rod24]

mods are in profile, basically a big16g w/ supporting mods. i just fixed my stutter problem with a set of new plug wires and im running good. tuning using my avcr and safc i have it set at almost 18lbs and i can run perfect with no fuel cut or anything. only question is that i bought this car used and im not sure on what fuel system is in it. am i safe running this high of boost since its not showing any problems?

mods:
Evo III Big 16g, Greddy FMIC, Greddy Type S, Greddy UICP and intercooler piping, Injen Intake, Full 3" exhaust (no cat), 1g Intake Manifold, Fluidyne Radiator, ACT 2600, Neurospeed Short Shifter, SAFC, AVCR, Boost & A/F gauges.

Most have suggested running 550 cc injectors with a walbro or similar fuel pump. I have the same turbo on mine and it seems to do well with these fuel mods. But I never ran it with the stock set up so I can't really say whether it made a difference.

I didn't really answer your question but....

 

[Ultimatedsm]

I hope you are running bigger injectors than the 450cc's and a higherflowing pump than the stocker. If your not, your motor is going to go BOOM .