Stock Boost [Merged 5-7]

[Gs-tHaVoC]

hehe kinda dumb question but whats stock boost on my car? just wondering if its worth it to install a boost controller and gauge without bov thats all. thanx

 

[Denji]

The relability problem of running 17 psi without many mods is that it will eat away on your piston rings. Do a compression test now, and do one in a few months, let me know the results.

any opinions on this statement?

 

[Ultimatedsm]

All I can say is wow.....
Boost does NOT change the compression of an engine. Let me say that again, boost does NOT change the compression of an engine! In a 1g turbo, if you run 11.5psi as opposed to 30psi, your piston will still compress the air/fuel charge 7.8:1. Compression is how many times the piston compresses the volume present in your cylinder from BDC to TDC. A turbo will only make the volume of air entering that cylinder more dense to start with.

To answer the original question of the thread, our stock turbo(4g63t) engines can handle ~23-24psi before you have to start worrying about the head lifting.

Your compression ratio as in static compression ratio doesn't change obivously thats fixed. Sorry I didn't make my self clear, I mean't the boost compression ratio. For example, You are better off with a low compression/high boost combination. The combination of turbocharger boost coupled with your static or geometric compression ratio provides a resultant Effective Compression Ratio. There is a complex formula for determining the Effective Compression Ratio. However as an example if you are running an 8.75:1 static compression ratio and 6 pounds of boost you will have an Effective Compression Ratio of 12.32:1. You don't want to go too high or POP . Anyway I hope that clears things out.

 

[gr8popp]

as long as the car is tuned properly and with with supporting mods 20-23 psi is safe. If you have a stock car I would limit my boost to about 15 psi. Anything over that will cause fuel cuts, knock, detonation, and your factory smic isn't too effective after that.

 

[stirpicult]

Your compression ratio as in static compression ratio doesn't change obivously thats fixed. Sorry I didn't make my self clear, I mean't the boost compression ratio. ... Anyway I hope that clears things out.

yes, that clears up a bunch. when you say "compression ratio" people read it as just that. but thanks for the clarification.

 

[Ultimatedsm]

Quote:
Originally Posted by Ultimatedsm
The relability problem of running 17 psi without many mods is that it will eat away on your piston rings. Do a compression test now, and do one in a few months, let me know the results.


any opinions on this statement?

Any opinion on this statement? Why don't you give it a try run lean all the time and let me know after a few months by doing a compression test. It is not an opinion, this is an actual experience.

 

[dave99gst]

knock + detonation will kill the motor before PSI will.

 

[94Jettameowpsst]

Actually, although all this points are valid, it leans more towards the size of the turbo you are running. You can run 20 psi on a stock motor using a 14b. But if you're talking about making power and determining how much power you can make before stuff breaks, you might have a problem running 20psi on a gt35r on a stock motor. I know < that can be done easily, but i think you get my point. Efficiency of the turbo and compression is the key. If your running 7.8:1 comp. and pushing 400cfm @ 20 psi, its easier on your motor than running the same compression and boost but pushing 1500 cfm. I hope that helped a little bit

 

[11sectsi]

With all the right supporting mods and tuning you can run 26-27psi on a stock engine. I am running 29-30psi for over a year now on my stock engine and it runs fine.

 

[Denji]

Any opinion on this statement? Why don't you give it a try run lean all the time and let me know after a few months by doing a compression test. It is not an opinion, this is an actual experience.

I think i was bothered by the vagueness of that statement. The original post never said anything about running lean. If you have a few mods, and they are the right few mods, you very well could run 17psi and not have piston ring problems for a long while.

 

[v2ner]

yep, 27psi for a year now. stock internals.

 

[VicBoost]

so basically if i get a good fuel pump and fuel injectors you should be fine?

 

[BoostinAWD]

I'm running 18 psi on my 91 fwd. Stock fuel pump and injectors. Have arp's and a brand new head. Doesn't knock at all.

 

[stirpicult]

so basically if i get a good fuel pump and fuel injectors you should be fine?

and tune them in (safc, dsmlink, etc)

 

[Minimalitia]

Hey i was wondering if my car is supposed to be putting out roughly 17 LBS. of boost without any mods other than exhaust? i installed some gauges and one was obviously a boost gauge (Faze) and wen i drive hard it maxes at 17 lbs. but im a lil worried.. i blow blue smoke out the tail pipe and from around my turbo if it sits at idel too long and i have really really bad fuel cut at around 14 lbs. of boost.

 

[Black94DSM]

Deffinatly not, should be more around 11 psi stock.

 

[SkyLineGtR-R34]

Hey i was wondering if my car is supposed to be putting out roughly 17 LBS. of boost without any mods other than exhaust? i installed some gauges and one was obviously a boost gauge (Faze) and wen i drive hard it maxes at 17 lbs. but im a lil worried.. i blow blue smoke out the tail pipe and from around my turbo if it sits at idel too long and i have really really bad fuel cut at around 14 lbs. of boost.

Don't even think of going more than 12-14 without a better fuel delivery. Just think of it as if you turn the boost up you push more air in. If you push more air in you need more fuel in too.
And if you put bigger exhaust you'll start getting boost creep.
I would recommend reading some tech articles on this site about tunning steps.

 

[vintagemuscle]

the reason you are pulling 17lbs. of boost is probably because of your exhaust. a 3'' exhaust on a 14b is just asking for boost spiking. to solve this you are at the very least going to have to have the wastegate area of the turbo ported and also your o2 housing ported on the wastegate side. the best way would be to go with an external wastegate setup on your manifold.

 

[beatshack]

Even with 3" exhaust you still shouldn't be creeping to 17 pounds. I have the stock 14b on my car, stock o2 housing, 2.5" downpipe, 3" catback. I only hit 11 psi with no boost leaks. Did you mess with the boost control solenoid?

The blue smoke is either oil slipping past your piston rings or your turbo seals.

I just read your car profile, you have a 16g exhaust side and a 14b compressor side??

 

[Minimalitia]

Im not sure about that.. someone i met said that the way my car is set up rite now and if it is pulling the numbers that it did than i probly have a 16g heat side.. i believe the numbers were somewhere around the low 14's and a speed of 96 mph in the quarter.

 

[Minimalitia]

and no i have not messed with anything that has to do with the turbo ### i dont know what all the parts to it are yet. but if this helps when my turbo spools up somewhere near upper 3,000 rpm closer to 4 grand the turbo spools instantly to 13 or 14 lbs. roughly then a lil higher in the rpms it gradually increases to 17 and then im almost at 7 grand and need to shift. the colder days im fuel cutting at 15 lbs

 

[payup]

Turn the boost down to 10-13 psi. I believe this is a safe number on stock stuff. The blue smoke is oil comeing from somewhere. I would do a dry/wet compression test, and a cylinder leakage test to see it your rings are going. Could also be a problem with your turbo.

Hope you get it fixed and runnin good. Stay boostin (but not that much)

 

[Minimalitia]

How do i turn it down if everything is all stock but my exhaust? i dont have a boost controller.

 

[fwdeclipse]

You probably have boost creep,although im not sure 14b have that problem.I have a 14b with a full 3" exhaust and i can run 11psi all the way to redline.Also you may want to check for a boost leak,you should not hit fuel cut at 14psi.

 

[iboostdoyou]

17 isnt normal, but it isnt absolutely horrible either. My t25 boosted 16 psi with a catback and an intake so I doubt anything is wrong. Logged everything with my only mods being intake and exhaust and i wasnt close to maxing out my fuel or knocking, or anything like that. If you do in fact have a 16g hot side then that would explain the boost creep, as well as the fuel cut since it will flow better than the 14b. The 1g MAF's arent the best of units, and can't really handle the added boost too well without some kind of engine management. Go out and buy a boost controller for $30 and turn the boost down to 15 if your concerned about the fuel cut, but it's not necessary. Have fun and dont blow anything up

 

[zippyshoe]

As an experiment, you might want to try connecting your wastegate actuator directly to your turbo compressor housing/J-pipe (to bypass the factory boost control solenoid) and seeing what boost level you reach. In this setup you should only be seeing roughly 7 lbs of boost. If this setup functions correctly, than you might suspect a problem with your boost control solenoid or one of the vacuum lines to/from your boost control solenoid.