hey guys i have been wondering for awhile now why people want to upgrade to larger turbos when nobody has come up with a solution to the 2bar map sensor?? are there benefits to running a larger turbo even if you can only run up to 14.7 psi which the stock turbo could handle??
i know the turbo wont have to work as hard to achieve full boost (more efficient) but i don't see how upgrading will make more power without upgrading to a 3bar map sensor and fixing computer controled fuel cut...that from my reading no one has fully solved...
help me out...what am i missing
thanks in advance,
mike
You must not be very well up to date on what the important thing to look at with a Turbo is..
PSI is a measurement of restriction, the number you really want to look at is the CFM
Example, say turbo A here is the Stock Turbo and Turbo B is that one turbo ????
Anyways, say Turbo A here can push this X CFM of air at 14.7 PSI, where Turbo B there can push this same amout of CFM of air at say 6-7 PSI, so your running 6-7 PSI of boost and getting the same amount of air which is probably going to be much cooler as well as the Turbo A at 14.7 PSI, so you can go 7 more PSI and flow THAT MUCH more air, and we know more air equals more power.....
Does that make sense? That is one reason why you want to upgrade to a bigger turbo.
Now on the 3-BAR topic and what not, if your really going to pushing that much boost then you WILL figure out how to trick the computer, hey maybe just put the 3-BAR sensor on and tune it to the liking of what the computer thinks is a 2-BAR MAP sensor, or something like that maybe? I'm no expert on this part, because well if your pushing that much boost your probably not going for driveability and quite frankly a nice AEM/Haltech Programmable EMS will probably get the job done and has no problem being tuned for a 3-BAR MAP sensor *Puts on flame suit for flames on this one*
i realize that the bigger turbo can flow more air compared to stock at any given rpm, but what im saying is, if the boost is computer controlled (run off map sensor readings) then it shouldn't matter becuase which you use, becuase, the same amount of air should make the same amount of psi (ignoring the intake temp). meaning if you measured the flow rate and the psi for each turbo that is pumping into the same sized chamber, wouldn't you see that they are each flowing the exact same amount of air for a given psi, the only difference would be the smaller turbo must spin much faster to achieve the same effect.
it takes a certain amount of oxygen within the manifold for any given incremnt of read boost.
example: a 3 oz cylinder is filled with 10oz of gas resulting in 30psi of contained pressure (numbers are hypothetical)
now you have another 3oz cylinder with an unknow quantity of gas that also reads 30psi of contained pressre. how much gas was compressed into the 3oz cylinder? you would inference from the previous information that 10oz of gas was compressed into the 3oz cylinder.
so what im trying to say is that it doesn't matter if one flows more air becuase in the end the psi converts to a volume inside the manifold....so each turbo must compress the same amount of air into the manifold for any given psi of pressure....again the only difference being that the bigger turbo can do the job at a much slower rmp but its gains really come from exploiting the fact that it can achieve a much higher peak flow rate and thus a higher psi.
that is my thinking behind it and i will need further discussion to swayed from my stance....if im wrong so be it...haha im anal about this kind of thing and obveously stubborn...not to mention that i like this sort of discussion so don't just tell me your right PROVE your right..
how is "PSI is a measurement of restriction?"-- z284pwr
if you had said constriction that may have worked still needing explanation
explain this more please...
p.s. do not! i repeat do not!! take any of this personaly!!! i only seek to find full understanding of the subject
thanks again
mike
Wrong....
Like I said, PSI is a restriction I think your thinking of it in a wrong way, its hard for me to explain what I mean, let me put it this way, this is a bad example but you should get the idea
If you took the BEST flowing engine in the world that could alway outflow more air than could ever be pushed into it, you would NEVER get pressure right, because the engine would always flow more air than the turbocharger would be able to produce, so all the air the turbo is pushing isn't enough to pressurize the intake tract.
I know this should make sense, when you drive your car and you feel the turbo start spooling but the engine isn't under boost, can you still feel how the engine is making more power because it isn't running out of air yet but the turbo hasn't pressurized the intake tract? This is easy for me to explain because the wastegate on my car is messed up so when I hook vacuum to it, it begins opening so the turbo can never produce boost so you can hit 0 inHG of vacuum but you never feel the car have the power that it should because the turbo isn't producing enough air to make a difference in the intake, as where with it unplugged the turbo will produce air but I'm not using enough throttle to require it but you can still feel the power difference, does that make sense?
However, yes a bigger turbo will flow more air, but the thing is, it is capable of flowing that amount of air at a different pressure ratio than the stock turbo. Look at the turbo flow charts and it will make more sense. Like I said in the first one just differently, Turbo A can produce X CFM at this pressure ratio, but Turbo B can produce that same amount of CFM but at a much lower pressure ratio and more effeciently, producing less HEAT which obviously is less RPM from the compressor wheel
Quoteit takes a certain amount of oxygen within the manifold for any given incremnt of read boost.
Now this, yes this is true, however, think of it like this, yes it will read boost, HOWEVER running this larger turbo at the SAME PSI will mean your running A LOT more air into the engine which the engine WILL NOT recognize with it being a MAP controlled thing, HOWEVER on different cars such as a DSM for example, it uses a MAS Mass Air Flow which calculates HOW MUCH air is going in now by the pressure so it can more easily compensate for a larger turbo because it can recognize the amount of air charge as compared to a MAP sensor where it will only recognize the pressure inside the intake and give that much fuel in return and if your running Turbo B here which is pushing a lot more air at the same pressure its going to cause some serious detonation because your pushing that much more air with the same amount of fuel.
Quoteso what im trying to say is that it doesn't matter if one flows more air becuase in the end the psi converts to a volume inside the manifold....so each turbo must compress the same amount of air into the manifold for any given psi of pressure....again the only difference being that the bigger turbo can do the job at a much slower rmp but its gains really come from exploiting the fact that it can achieve a much higher peak flow rate and thus a higher psi.
that is my thinking behind it and i will need further discussion to swayed from my stance....if im wrong so be it...haha im anal about this kind of thing and obveously stubborn...not to mention that i like this sort of discussion so don't just tell me your right PROVE your right..
Now this, YES this is correct, but REMEMBER, not all engines breathe equally. An built engine that has more lift, ported heads/intake, bigger vales or whatever, will be capable of flowing MORE AIR than a stock engine, which will result in stock engine being more prone to building this pressure than built engine which is going to be capable of flowing this air resulting in a less pressure build-up, correct? I think this is where we are thinking differently. Think of it like this, try taking a small straw and breathing through it, not very easy right? Now take the straw out and breathe, and see the difference, you are flowing more air resulting in a less pressure build-up *in the straw* So like I said, pressure is just showing a restriction, this straw being the restriction.
Oh yeah, I totally see where your coming from and take non of it personally. No I'm not an expert this is just coming from what I understand and have read. I'm sure someone will come in here and better explain and may even prove me wrong, who knows?
Anyways, yeah, that is it, any comments to further move this discussion along?
Quote...running this larger turbo at the SAME PSI will mean your running A LOT more air into the engine...
i understand that if you run the two turbos at the same
RPM you will flow more with a larger tubo...but saying that you run the two at identical psi in indentical motors and would still mean that you have the same amount of air moving through the manifold...how can you say that the engine (big turbo) gets more air than the engine (small turbo) when physically there must be the same amount of air present in the manifold to create a certain PSI of pressure
so again please support this statement scientifically!!
and when you talk about psi of restriction do you mean as in intake/exhaust flow of the heads...your straw analogy is suited to explain that larger ported heads or bigger diameter exhuast systems would let the turbo breathe through the engine easier (less flow restriction), but you should try to find an analogy that focuses on whats pushing the air. unless you care to re-explain that more thoroughly as i may have missed the your exact point...
What about a granger valve to leak off the boost before it reaches the sensor, like the turbododge guys use?
oh, thats sound pretty clever!!! anyone here ever try one???
Having a 2 bar map sensor is not much of a problem. All you really have to do is, since at any boost over 14.7psi it will still read 14.7psi, you just program the chip to provide the right fuel and timing for your max boost that you are running and command it at 14.7psi. Yeah, at the lower boost levels that are above 14.7psi it won't be exactly right, but it will be close and this method should work pretty well. (unless of course you are gonna run like 30psi or something insane like that)
PSI is a measure of restriction. If you were to hook up a supercharger to some sort of motor/engine and put it in a room (lets just say 10' X 10') and let the supercharger pump air from outside or something like that into that room are you gonna have huge PSI numbers? No, you're not even gonna make close to 1psi. But if you put the same supercharger on an engine and spin it the same rpm it might make 10psi on the engine. Why, because there is a much smaller space for the air to go into, so it has big pressure numbers. This is why if you take a GTP and put headers on it, boost drops about 2psi, it also drops about 2psi with a cam. If you get the engine to flow more air, it won't make as much boost with the blower spinning the same speed, because there isn't as much restriction causing the air to back up.
I personally am not knowledgeable enough to tell you anything on the psi vs. cfm debate, but I can tell you that I've heard/read from numerous places that you can have the same psi but different cfm. Don't know how its possible, but i know it makes a difference with different sized power adders.
Shawn
Lookie here :lol:
GT28rs
http://www.stealth316.com/images/gt28rs-62trim-raw.gif
GT42
http://www.stealth316.com/images/gt42-raw.gif
Notice at a 2 PR (14psi atomosphere{varies on elevation}+psi boost guage/14.7) the smaller GT28rs turbo can only flow about 35 lbs/min max at that PR. Now a GT42 can flow 75-77 lbs/min at that same PR. This is with the same turbo oulet temp. Its said that about every lbs/min is worth 10hp. But we don't get what we see on paper. Theres still other factors. From the air filter to the open intake valve and from the exhaust valve to the exhaust tip..we see many ristrictions that don't let all of the air go into the cylinder to get those nice numbers.
At 4500rpm and a pre-intake valve air temp of 70*F a PR of 2 on the 1st turbo we could get 260hp. Same conditions at 2PR on the 2nd turbo we could get 290 hp. "WTF..what happen, why so little gain". Hold on!
If we port the heads, port the intake, exhaust, bigger pipes, low ristriction IC ect.. that 1st turbo would produce its max flow rating of 350hp at a PR of 2. "YEA!"..BUT...what if we slap that bigger 2nd snail on there.. Now we get close to 400-500hp. "DAM that's crazy power, how come it don't got to 550-600hp? Its still a small gain" Good Question. The differance is the Turbine side. THe bigger turbo can flow more air on the turbine side AND requires a bigger inlet which can flow more air compare to the t2 flinge. This = to less back pressure/ engine pumping loss/ less exhaust leftovers in the combustion chambers. "OK , how we get more HP" Well this is when we need to increase the boost when the heads/engines given all its got known as Volumetric Efficiancy (VE). This is when a 3bar comes into play. Jack the boost up..more HP to a point. "But what if we did this to the 1st turbo?" The first turbo is already max at a PR of 2..trying to increase the boost on the first will come to a diminish in airflow (lower HP) , cuz it goes into surge limit, impeller speed increases, back pressure on the exhaust increase, engine is lossing power trying to pump the turbo and the turbo is choking the engine.
The major problem with our T25 is the exhaust side. If we could upgrade the turbine/housing for a .80-1.5 A/R housing/ high flow turbine we could fully utilize the stock compressor with stock intake tracks or ported tracks. As is were seeing almost 3 times the exhaust backpressure to intake pressure. so at 10 psi guage on the TGP..were getting 30psi on the x-over preturbo pipes because the turbine section is a choking point. The rate of pumping loss increases as the boost increases. Why do you think we can only get away with 10psi . Beyond this and were lossing power. A large external Wastegate is a good patch/remedy.
But then if you live in the Mountins (TGPilot can tell you about the thin air). The turbo will almost not see its full potential cuz of the thin air. 7psi altmostphere pressure +14.7 psi guage / by 14.7 is 1.47 PR..which will also effect the DR.
Oh theres soooo much more to this. The Math and real life events seem endless.
Heres a good site to read/learn from. One of the best done sites I've seen.
http://www.stealth316.com/2-3s-compflowmaps.htm#i
So to sum it up.. At a given engine N/A VE/rpm...at the SAME PR, SAME TEMP, ..ANY compressor side WILL flow the SAME amount air into the engine ON a Turbocharger setup. The difference is in the turbine side/ exhaust side.
Supperchargers work differently. Increase the VE on the engine..the boost level drops cuz SC work on positive displacement based on crank rpm. The same ratio of the rotors to crank stays the same at all rpms IE 10:1. If the SC boost 7psi at 4000rpm then you port the heads do other "after SC mods" the boost level drops cuz of less restrictions. Increse the "pre SC mods (ram air, cold air.ect)" the boost level rises. Also increasing the ratio of the pully increases the boost.
I was thinking like you Brian. But I realized that VE has a dramatic affect. Even if the PR is the same on both..and the temp is the same ..regardless if the turbo can flow more Lbs/min at that given PR..the intake valve and engine displacement will limit the amount that goes in. This is when more boost forces more air to go into the cylinder. For example ..even if the turbo flows 35lbs/min or 70lbs/min at a 2PR..the intake stroke at a given VE will only allow a certin amount..IE..27lbs/min per intake stroke at that PR. Now increase the PR and more lbs/min will "shoehorn" itself in the cylinder EI 35lbs min. No boost (PR of 1)and were back to 14lbs/min.
I've still need to explain why we loose boost on the compressor side when we increase the flow of the exhaust on the turbo..but im too tired right now. It should be self explanitory if you think of it. Maybe Jeff can finish this little novel :lol: .
I still need more to learn :shock: .
ok, i accept that if a tgp setup was running P&P heads and highflowing intake and exhuast that a bigger turbo would do some good (i acknowleged this earlier)...but our turbos don't exactly "choke the engine" meaning that stock heads and exhuast dont really need more boost to do what they are already limited to do...
i don't know how much sense that made...
dbtk2 your room example works to say that if we had a bigger intake it would be harder (or impossible) for the smaller turbo to keep it pressurized, yes, but that has nothing to do with where the computer cuts your fuel that goes off of map readings...which comes down to the volume of compressed air inside the intake...and you didn't feel you were up to tackling the cfm vs psi debate....
im really curious about the fuel cut off raiser/boost controller http://gusmahon.org/html/cutout.htm
how much of a gain would you see with good tunning/how much boost will the stock t-25 push?? i read in the previous post that 10psi was the only usable boost we can get possibly...if thats true than a jeff m chip can already do that correct....but with a bigger turbo and this device along with some clever tuning and supporting mods....how far could this primitive aproach take this engine? would it only get worse the higher the peak boost level?
Finaly I'm with a fresh mind. OK. Now the other difference why we need to upgrade the turbo ..and this goes for the compressor side is the Compressor Efficiency.
QuoteThe elliptical curves with labels such as 60% represent the efficiency of the compressor, or how well the compressor achieves pure adiabatic heating of the air (higher numbers are better and mean less extra heating of the air).
Im more than sure our little t25 is like the Garrett GT25R or Maybe the GT22. You could prob use those as a referance.
Remember that I said that AT a given RPM/VE no matter what turbo ..if the
TEMP was the same and the PR was the same..the same amount of air would flow into the engine. Well my friend for the real world..the temp doesn't always stay the same. Also the intercooler effectiveness plays a role. For a PR of 2 on the stock turbo we could be getting a compressor efficiency of 70%. If we get the GT28rs or the GT30 we could see that we have a better compressor Efficiency at that same PR. SO the compressor oulet temp of our t25 could be 270*f at a PR of 2..while the GT28rs or GT30 could be 240*f. Now get the intercooler in line and we could see the outlet at the IC at about 130*f on our t25 while the GT28rs or GT30 could be at 110*f. This means more denser air (DR) into the engine which = more power. VOLUME OF AIR don't mean JACK 'AKA' CFM (cubic feet per minute). The engine will consume the same volume of air no matter what at that given VE. BUT DR will be different. Theres calculations to convert turbos into CFM which is the absolute CFM. If you think about it..the engine will consume lets say 150cfm per given VE. IF you put a turbo on there boosting at a PR of 2..the same CFM will be the same at that same VE. BUT the turbo compresses the air to get more desity out of the same CFM. DR is like a multiplier. SO 150cfm now looks like 225cfm "assuming 1.5 DR" (150cfm x 1.5DR=225cfm).
OK now looking at what you said tgp'er.. this is why we need to upgrade turbos/up the boost. THe stock heads intake can be maxed out at the 150cfm mark but the DR of the turbo really makes it shine and makes those 150cfm look like 200-500cfm. This increase in power will come to a haut onece the exhaust side cain't flow out all what the intake side is consumming. This is when modding begins to take full advantage of the better snail. The intake side (I'm useing this term loosly) doesn't need upgrading to get more power. THe exhaust does.
(Let's see if I could word this right..math again is not using exact figures..too time consuming to do) We can crank more boost from our little t25 than 10psi if the weather is cold. The density of the air is better. The exhaust volume/DR won't be too high for the density of the air entering the cylinder. Another example: At a hot day the DR of the turbo at 10psi is 1.3. On a cold day its 1.6 at 10 psi. IF the cylinder at a given rpm/ve can only hold say 150cf of air and the 30 psi of back pressure on the exhaust is consumming 50cf then the intake charge only has 100cf to play with. So 100cfmx 1.3 is 130cfm of usable air. Now cold day at 10psi is 160cfm. So you can still crank the boost up to a point where exhaust to intake air ratio is still good at making more usable power.
Max PSI on our Stock turbo depeds on the air temp, atmosphere pressure. If you live in Rockies on a summer day...you'll notice that your turbo is crying uncle at 8psi. If you live in the Coast during the winter..your turbo will most likely live at 14-20psi.<- where a 3bar map comes handy or map trickery(not verry safe).
Our turbo prob tops out at 280HP at 75*f. No more.
thanks for the input TurboGTU i think your last post and reading the websites clarified some of the variables that i was unaware of. :)
TurboGTU what turbos have you come up with that would be good for our cars? are you going to be buying your own and experienmenting...
also could you explain to me how and why an external wastegate is better than internal...
thanks for the info,
mike
Thanks. No problem.
The thing with compressor effectiveness is that even if the IC is 60-99% effective at cooling the air..most IC don't see constant air to cool them down..IE during takeoff, location of IC or, low speeds. The IC will act more like a ristrictive pipe or smaller IC that cain't cool the charged air down enough. Almost like not having an IC..so this is when Compressor effectiveness really becomes important.
THe best turbo for our car would be the GT28rs*. The engine demand lines fall all over the good spots. However the turbine side does flow good, I'd still want it to free more. I've heard of so many sources say that the turbine side has been improved by the aftermarket..but no maps of them like the Garrett site has. This turbo should be almost a direct swap too. For more hp up on the rpm band...the gt35(with the smaller wheels) looks great if you could deal with some lag..furter mods make it shine. This one requires a x-over, new pipes.
But like I said the real world is different.
Im going all out on high hp/tq (max ported heads,costom parts..ect). So my turbo choice is till not yet decited.
The thing with an external WG is that 1. The exhaust gasses don't crash with each other like they do in an internal gated one...slowing down the flow. 2. Your not limited to the size that you only get with an internal flap. The bigger the WG..the more BP it can vent out.
http://www.atpturbo.com/Merchant2/merchant.mvc?Screen=PROD&Product_Code=GRT-TBO-025&Category_Code=GRT
what about this turbo... its t25 flanged turbine and it supports 450hp...the outlet looks just like our flange too...so would this be a high hp bolt in??? didn't see a map for it though...anyone know if it would be a good choice for a hi hp upgrade?
http://www.atpturbo.com/Merchant2/merchant.mvc?Screen=PROD&Product_Code=GRT-TBO-025&Category_Code=GRT
what about this turbo... its t25 flanged turbine and it supports 450hp...the outlet looks just like our flange too...so would this be a high hp bolt in??? didn't see a map for it though...anyone know if it would be a good choice for a hi hp upgrade?
Well, I don't know how fast you want to go, but that turbo is going to require some major tranny and fuel system mods for it to work. Really, the biggest I would go with for a street driven TGP is a GT2871R, which IIRC supports 400hp. But for most everyone on here, the GT28RS is plenty big enough. It should provide a very large gain.
Shawn
is the turbo i was looking at and the two that you named...are they all direct bolt-in replacements??
oh yeah i know that those bigger turbo require alot of mods and supporting tuning to run properly...i was really just wondering if the characteristics of that turbo (gt30 71R-WG), could ever complement/work with our displacement and rmp range in a moddified engine (higher flowing heads, exhaust, bigger injectors, fuel pump and all the supporting tuning)
basically if we had a need to reach 450hp would this turbo (compressor map and turbine map, couldn't find any) be a good choice....or are their other bigger turbos that would work better.
i sent atp an email and they refered me to maps of the GT3071R becuase they don't have any for the GT3071R-WG...so the guy said they are very similar (compressors have the same wheel size and trim, A/R is the same too) here are the links...could somebody with better knowledge of reading the maps explain why this turbo would or would not be a good choice for a high hp build up.
trubine: http://www.atpturbo.com/root/maps/gt3071rturbine.htm
compressor: http://www.atpturbo.com/root/maps/gt3071r.htm
the guy who emailed me back said "this would be a 'sweet' set up." jee whiz thanks for nothing...