having boost creep/spike in cold weather

[zatomz]

Here's the deal, when I come home late at night, when it's cold out, I get it to WOT and at about 4000 rpm my VDO boost gauge creeps from 16 psi to 20 psi which is not good b/c I'm not set up for 20 psi. When it hits 20 psi The whole car jerks wildly, I'm assuming b/c there's not enough fuel to compensate. What i need to know is why, why is it doing this in the cold weather and not when its warmer outside. Next I would like to know, besides a leak test which I'm working on finding the time to do, what i can do to solve the problem. Thanks for any advice you guys are awesome.

 

[dave99gst]

cold weather = cold air
cold air = more air + less heat soak.

 

[zatomz]

Don't flame me but I'm not sure I follow you. I don't understand how more air or colder air could cause creep and bucking. This is a new thing, it started idling weird a few weeks ago it will idle at 1100 and then drop to 500 then back up. I know this Isn't new but could it have anything to do with the creep. I just want to know if these two things are linked together somehow.

 

[fastalon82]

No, the idle fluctuation is your ISC motor, you need to buy a new one. And the jerking is fuel cut. I didnt see anything about a boost controller but if your using a cheap one that might be your problem.

 

[zatomz]

Its an extreme bc manual boost controller, I've been looking for a used isc and will be doing fuel mods as time and money allow...thanks.

 

[xcz504d]

Why don't you stop running a 16G turbo without a fuel pump on 440 injectors...

 

[2gGSX]

If you can't hold boost no matter what you do I would suggest just using your foot as your boost controller and lay off the throttle a little. That is, until you get the supporting mods to run the boost your turbo wants to run.

 

[oldman]

It is general accepted that boost creep is solely caused by the inadequacy of the wastegate design. This is true but like the size of you exhaust system, I think (though I'm 100% how exactly) intake capacity also plays a role. I thought about this for a while years ago when right after the installation of my fmic kit, I started creeping. Let's say your wastegate was right at its limits, any extra air flow (in your case colder intake charge) will most likely exceed that maximum capacity and cause you to creep, same reason why I started to creep after FMIC. Like I said, I'm not 100% sure but it's the only logical explanation I came up with. In any case, you have creep and it's time to pull the turbine housing and give it a proper port job.

 

[xcz504d]

Oldman, you are absolutely correct, boost creep is caused by the wastegate not keeping up with the amount of exhaust it needs to by-pass... But there are other things in the system that can cause this problem, bad boost controller and such...

If you have boost creep generally there is to much exhaust gases flowing through your wasetgate, so where does the exhaust gas go? through your turbo spooling it up faster...

 

[zatomz]

So say it is something with the wastegate, it's an internally gated 34mm what could be done...the turbo itself has been ported and I do have all of the supporting mods less the fuel mods but I need to get dsmlink first. I think your theory is pretty much dead on though. One question though, how much boost can stock injectors and fuel pump... ect. ....before it cuts out

 

[2gGSX]

With my setup, 28 lbs/min and just under 64% IDC on Denso 660cc injectors (about 420cc of flow) with the stock pump.

 

[oldman]

So say it is something with the wastegate, it's an internally gated 34mm what could be done...the turbo itself has been ported

Unless the turbo was ported specifically for eliminating boost creep, it will not work, this includes majority of vendor $50-$90 port jobs which focuses mainly on improving flow and spool, boost creep porting is a completely different animal. Check out the link below which lays out exactly where and how much to port, most important being the wastegate entrance at the turbine inlet.

http://www.dsmtuners.com/forums/showthread.php?t=186525

 

[xcz504d]

Boost means nothing... Think of "boost" as a buzz word... Let me give you an example of what I mean... 2 turbos...

One flows 400 CFM at 12 PSI (30 lbs per min or somthing like that)
and another flows 700 CFM at 12 PSI (49 lbs/min)

Your stock 440 injectors and fuel pump can handle the first turbo set at 12 PSI, but the other turbo you would need somthing along the lines of 660 injectors and a 255 pump...

So asking "how much boost can my stock fuel system handle" is a question with to many variables...

Now Boost IS VERY important when talking about how much increased PRESSURE your engine can support... When I say pressure, I'm talking cylinder pressure... to much boost and you start blowing piston rings, getting pre-detonation and yadda yadda yadda...

So when talking about horsepower, how fast your car can go, or trying to rationalize horsepower and boost... boost is a marketing buzzword... CFM and lbs/min is what's important... More air and less boost is what you want If you can get 1000 CFM at 2 PSI, why the h311 would you want to turn it up to 16 psi...


SOOO to answer your question finally, I wouldn't worry about running 15 PSI with your 16g turbo and stock fuel system... You're probably maxing out your injectors, or coming close... but I wouldn't worry about it... Besides, any more than 16 PSI on a 16G is worthless, you wont get much of a gain for the damage you're doing to the turbo...

Learn to read compressor maps, find your efficency point on the compressor map, and set your turbo to that, it will give you optimum power with optimum reliability...

 

[zatomz]

Alright now I'm from Colorado and recently moved to louisiana and its pretty much well known that lower climate=more air. So in colorado where 16 psi would be fine and dandy would being in a lower climate now cause the ammount of pressure being put out by the turbo to be increased. im going to turn my boost down right after this and see how that helps so ill post back in about 20 mins.

 

[zatomz]

FUC**NG DSM'S!!!!!!!!!!!!!!!!!!!!!!! So i turned down my boost on my manual boost controller and as i was driving i was watching my boost guage and it was running at 12 psi and then creeping up to 18 and almost 20 psi, next thing you know i look behind me and all i see it white smoke billowing from behind my car. I couldnt even see out of my rear window it was so thick. There was radiator fluid all over my motor and when i looked underneath it was pouring from the bottom of my radiator and dripping from other misc. places. All i can think of is head gasket. The car wont start it just cranks and when i try that there's more smoke coming from my exhaust.... I'm prepared for a blown head gasket but what else could I be looking at..... I can post pictures if need be please help me out or im out a car...... Oh steam and smoke from the engine bay but what is a sure sign of the blown gasket besides the smoke..... Thank you

 

[oldman]

If you know you have boost creep, why did you go out and do wot pulls without fixing it first. Turning down the boost via mbc will not solve your boost creep problem, in fact, the lower the boost level you try to run, the worst the creep. This what I would do next.

1. Pull the intake pipe and check the turbo for signs of any leakage and shaft play.

2. Obviously you have some kind of external leak, clean off your engine bay, locate the leak and fix it.

3. Compression test.

Good luck.

 

[Jason300zxTT]

this is why when i put my evo316g on I wanna do external gate. Boost spike is a bi***. My car is doing now with the shitty t25 i have it set at 14psi and it goes to like 16 17 and comes back down i hate it.

 

[oldman]

this is why when i put my evo316g on I wanna do external gate. Boost spike is a bi***. My car is doing now with the shitty t25 i have it set at 14psi and it goes to like 16 17 and comes back down i hate it.

Boost spike is different from boost creep, kinda opposite. Spiking 3psi before settling down is typical of a T25, an external for a EVO3 is an overkill IMO.

 

[lil corb]

I get the same thing. It's set at 13psi and it spikes to 14psi goes back to 10psi then settles at 13psi. I'm thinking my MBC line is too long, the hose goes from wastegate to where the MAS sensor is at. I'm going to buy zipties and tie it to fan.

 

[2gGSX]

this is why when i put my evo316g on I wanna do external gate. Boost spike is a bi***. My car is doing now with the shitty t25 i have it set at 14psi and it goes to like 16 17 and comes back down i hate it.

Why not do the supporting mods and run high boost instead?

 

[MyBeatGSX]

Besides, any more than 16 PSI on a 16G is worthless, you wont get much of a gain for the damage you're doing to the turbo...

Learn to read compressor maps, find your efficency point on the compressor map, and set your turbo to that, it will give you optimum power with optimum reliability...

Wait wait, back up a sec. I do have a s16G compressor map, and its in the exact same effiency circles at 19psi that it is at 15psi (it drops 1% through a small portion of the midrange), just a little further out. What map are you looking at?
As for not worrying about a 16G @ 16psi on a stock fuel system... I hope you're joking. I had a 255hp and AFPR on stock injectors @ 16psi and I was at what I would consider a maximum safe a/f (11.5). This guy still has a stock pump and regulator and you think he's ok??


lil corb: My MBC is zip tied to the fan with the shortest lines physically possible and it still spikes 1-2psi. More on a cold day from a high rpm roll. Don't even waste your time.

 

[xcz504d]

Wait wait, back up a sec. I do have a s16G compressor map, and its in the exact same effiency circles at 19psi that it is at 15psi (it drops 1% through a small portion of the midrange), just a little further out. What map are you looking at?
As for not worrying about a 16G @ 16psi on a stock fuel system... I hope you're joking. I had a 255hp and AFPR on stock injectors @ 16psi and I was at what I would consider a maximum safe a/f (11.5). This guy still has a stock pump and regulator and you think he's ok??


lil corb: My MBC is zip tied to the fan with the shortest lines physically possible and it still spikes 1-2psi. More on a cold day from a high rpm roll. Don't even waste your time.

No 2 setups will ever act the same... just one of those things you deal with as it comes... I've seen his car, I've raced his car... and I've seen other DSM's out run their 16G's with stock fuel systems... A 16G doesn't flow much more air at 20psi than it does at 16, and for the efficiency drop, it's not worth it... 65% efficiency is as low as anyone should want to run their turbo, at 68% a td05-16G flows 475 CFM, and at 60% it flows a maximum capability of 520 CFM... any more efficiency risked, IE more boost, then you start loosing more CFM and start severely limiting the life of your turbo... so while everyone would love to run max air flow through their turbo, PSI is not a reflection of how much air is flowing into your engine...

So, looking at a 16G compressor map... I see that the 16G flows 525 CFM at 19.2 PSI, and it flows 520 CFM at 15PSI... so what did that extra 4.2 PSI really do for you? Other than risk severe damage to your engine...

 

[xcz504d]

FUC**NG DSM'S!!!!!!!!!!!!!!!!!!!!!!! So i turned down my boost on my manual boost controller and as i was driving i was watching my boost guage and it was running at 12 psi and then creeping up to 18 and almost 20 psi, next thing you know i look behind me and all i see it white smoke billowing from behind my car. I couldnt even see out of my rear window it was so thick. There was radiator fluid all over my motor and when i looked underneath it was pouring from the bottom of my radiator and dripping from other misc. places. All i can think of is head gasket. The car wont start it just cranks and when i try that there's more smoke coming from my exhaust.... I'm prepared for a blown head gasket but what else could I be looking at..... I can post pictures if need be please help me out or im out a car...... Oh steam and smoke from the engine bay but what is a sure sign of the blown gasket besides the smoke..... Thank you

I don't know that you blew a head gasket with the description you just gave... Find where it is leaking radiator fluid, that sounds like the majority of your smoke... once that is taken care of you can figure out if you blew a head gasket...

Oldman had great advice, I cant think of anything to add to it...

 

[MyBeatGSX]

No 2 setups will ever act the same... just one of those things you deal with as it comes... I've seen his car, I've raced his car... and I've seen other DSM's out run their 16G's with stock fuel systems... A 16G doesn't flow much more air at 20psi than it does at 16, and for the efficiency drop, it's not worth it... 65% efficiency is as low as anyone should want to run their turbo, at 68% a td05-16G flows 475 CFM, and at 60% it flows a maximum capability of 520 CFM... any more efficiency risked, IE more boost, then you start loosing more CFM and start severely limiting the life of your turbo... so while everyone would love to run max air flow through their turbo, PSI is not a reflection of how much air is flowing into your engine...

So, looking at a 16G compressor map... I see that the 16G flows 525 CFM at 19.2 PSI, and it flows 520 CFM at 15PSI... so what did that extra 4.2 PSI really do for you? Other than risk severe damage to your engine...

Post up a pic of the compressor map you're using. I'm calculating the other way around. Forget what it theoretically flows at certain boost levels. The correct way to use the map is to figure how much air the engine is flowing at some of the highest RPM points it will see and cross referance that to the pressure ratio (thus giving you the worst efficiency it will see). Based on what I came up with, the worst efficiency I should be seeing is (obviously) at redline where it falls right in the middle of the 72% ring. Compare this to a 14B that would be worlds off the map at the same pressure ratio and air flow (probably worse than 50%). As a matter of fact, boosting to 19psi takes it back into the 72% ring at 7,000rpm, whereas at 15psi it falls just outside into the 70% ring. Based on the map I'm looking at, it likes more boost at higher RPM, with a small sacrifice in midrange as I already noted.

You're also forgetting there's a big difference between CFM and lb/hr. If I'm not mistaken, 525 cu.ft. compressed to 19.2psi is FAR more air than 520 cu.ft. compressed to only 15psi. Its about density, that's why lb/hr is a far more appropriate measurement. If all that mattered was CFM then there would be no reason to turbocharge anything. The idea is to increase air density, thus fitting more air into the same cylinder space... duh

As for not making a difference. The difference between 15psi and 19psi for my car was 21whp and 61lb/ft. And that's with a stock intercooler, clearly the efficiency isn't as compromised as you're making it sound.

FYI, I'm using the map from this site: http://www.rbracing-rsr.com/turbotech.html

Map link: http://www.rbracing-rsr.com/turbo/TurboMaps/td05-16gsmall.gif

 

[xcz504d]

Post up a pic of the compressor map you're using. I'm calculating the other way around. Forget what it theoretically flows at certain boost levels. The correct way to use the map is to figure how much air the engine is flowing at some of the highest RPM points it will see and cross referance that to the pressure ratio (thus giving you the worst efficiency it will see). Based on what I came up with, the worst efficiency I should be seeing is (obviously) at redline where it falls right in the middle of the 72% ring. Compare this to a 14B that would be worlds off the map at the same pressure ratio and air flow (probably worse than 50%). As a matter of fact, boosting to 19psi takes it back into the 72% ring at 7,000rpm, whereas at 15psi it falls just outside into the 70% ring. Based on the map I'm looking at, it likes more boost at higher RPM, with a small sacrifice in midrange as I already noted.

You're also forgetting there's a big difference between CFM and lb/hr. If I'm not mistaken, 525 cu.ft. compressed to 19.2psi is FAR more air than 520 cu.ft. compressed to only 15psi. Its about density, that's why lb/hr is a far more appropriate measurement. If all that mattered was CFM then there would be no reason to turbocharge anything. The idea is to increase air density, thus fitting more air into the same cylinder space... duh

As for not making a difference. The difference between 15psi and 19psi for my car was 21whp and 61lb/ft. And that's with a stock intercooler, clearly the efficiency isn't as compromised as you're making it sound.

FYI, I'm using the map from this site: http://www.rbracing-rsr.com/turbotech.html

Map link: http://www.rbracing-rsr.com/turbo/TurboMaps/td05-16gsmall.gif

Theres lots of things to consider when determining your boost, your altitude and pressure drop through your intercooler and how much your intercooler can flow will all affect how your turbo will perform... At a higher altitude, you will need more spool of your turbo to get the same effect at sea level (2 PR is 14.7 PSI at sea level)...

10 lb/min = 144.7 cfm if I remember correctly, take 525/144.7 = 3.62 which is 36 lb/min, I used that web site you referenced and it looks like they say 10 lb/min = 123.9 cfm... I did a little reading to find out the differences for us, lb/min = cfm * .07 (at sea level with 80 degree air) which is pretty close to the 144.7 I originally stated (only marginially off at 800 cfm) so you have to figure out your own pressure ratio (also called "Delta") to multiply by to figure out your lbs/min at your given location...

I'm curious how you figured you were running 72% efficiency?