turbo's- wixh spools faster? single or twin? i have heard convincing proof for both sides of the arguement..so..how do i find out for sure wich spools faster? cuz all i am looking for is MAYBE 20 psi. tops. but i dont wanna wait 30 seconds for it. 1/4 mile is well over by that time lol.
help me settle this once and for all.
- Thread starter suprashred87
- Start date
depends
the sequential setup of the stock 2J diverts all exhaust into spooling one turbo first, then the second kicks in, so it's faster and has a broader torque band.
The HKS upgrades for the twins is laggy as hell, a decently sized single will spool first (less weight, ect) and still have the same pull.
Keep in mind turbo designs vary and new tech will spool WAY faster than old tech (better turbines and compressor wheels, ball bearing center sections, ect...)
Lag can be defeated with RPM as well, that's why you slip the clutch off the line to keep the RPM"s in boost territory and build load to build boost to pull without bogging...
the sequential setup of the stock 2J diverts all exhaust into spooling one turbo first, then the second kicks in, so it's faster and has a broader torque band.
The HKS upgrades for the twins is laggy as hell, a decently sized single will spool first (less weight, ect) and still have the same pull.
Keep in mind turbo designs vary and new tech will spool WAY faster than old tech (better turbines and compressor wheels, ball bearing center sections, ect...)
Lag can be defeated with RPM as well, that's why you slip the clutch off the line to keep the RPM"s in boost territory and build load to build boost to pull without bogging...
These two posts should help you out.
And
HTH
SupraWood;5275194 said:
And
SupraWood;5275664 said:No worries socalguy, I was not talking about you. Doing a straight comparison between a single vs. twin is going to be VERY difficult because of the number of factors involved.
When comparing ultimate power it's really determined by two things (if we assume the same 2JZ engine at a given speed): 1) Boost & 2) VE.
If we assume, as we should, that you are operating at a fixed boost level, then VE is all we care about. Since we are talking about a given engine, we don't need to worry about head design, cams, intercooler, etc. It comes down to engine delta P. A single GT4088R can flow ~70lb/min. A single GT28RS can flow ~35lb/min. So, using two of them should provide the same potential. Meaning, the compressor(s) can provide the same maximum amount of flow.
So, everything else being equal, both setups would make the same power. This brings us back to the VE stuff I was talking about. The twins will require more energy because they are less efficient. This will raise the backpressure on the engine and hurt VE. So, you wont make as much power and you will make it later.
Below is a ROUGH match I did. You can see that the twins spool later because of the lower efficiency. I assumed the same VE for both cases (and BSFC) so that is why the power number are line for line in the upper rpm. The max boost line on the twins is lower because the compressor map I was using didn't go to the higher pressure ratios so I kept the boost down. As I said, this is rough. I don't think you'll find a GT4088R that spools that quickly in reality which probably means some of my VE assumptions were a little....optimistic.
Daniel
HTH
wow...awesome....thanks!
and just to make sure i understood it<cuz i have a MASSIVE headache right now>
a twin spools faster, but less power. a single takes just a bit longer but has wider powerband and has more boost potential. correct?
and just to make sure i understood it<cuz i have a MASSIVE headache right now>
a twin spools faster, but less power. a single takes just a bit longer but has wider powerband and has more boost potential. correct?
Ok, well then no. Not necessarily... AFAIK
You want to get out of the mentality of shooting for a target boost. Focus on a target power.
flow = power
boost = resistance against flow
Obviously, more boost will yield more flow but only to a certain extent. At a certain point, more boost will only result in increased pressure but not necessarily anymore flow. One engine can make more power at X amount of boost than another engine with the same turbo because of flow characteristics.
You want to get out of the mentality of shooting for a target boost. Focus on a target power.
flow = power
boost = resistance against flow
Obviously, more boost will yield more flow but only to a certain extent. At a certain point, more boost will only result in increased pressure but not necessarily anymore flow. One engine can make more power at X amount of boost than another engine with the same turbo because of flow characteristics.
Ok, well let's take a hypothetical situation. (Well, one that can be fairly common).
Let us say an engine with stock cams puts down 300hp@14psi.
Then the owner adds aftermarket bigger duration/lift cams and dynos the car again without making any other changes. The new cams will allow the engine to flow more air and make more peak power but the boost pressure may have dropped some due to the cams allowing the engine to flow better than before. The end result in may be 310-320hp but at a lower boost pressure. More flow, less resistance(boost), more power.
Just a situation I made up on the spot.
Cams have other specific effects on any engine's characteristics but that is another discussion...(Probably one that can be found using search.)
If you increased boost by some small increment and watched the gains on the dyno, at some point you will hit a level where adding more boost will result in no more gains because the engine has reached its flow limit no matter how much pressure you put in the system.
Think of blowing through a thin straw. The harder you blow, the more air comes out the otherside. But if the straw is small enough(and your lungs are strong enough), at some point blowing harder will not move anymore air through the straw but you will still feel the increased pressure resistance the harder you blow... Now increase the size of the straw. You can move more air easier and you will feel less pressure resistance in your cheeks/lungs/whatever. And if you increase the straw size too much, at some point, your lungs will barely be able to keep up any pressure at all... Think of maybe a straw that is 1/8" in diameter and another straw that is 1" in diameter.
You could try this just by making the gap between your lips smaller or larger when you blow. (Just keep from passing out from blowing too hard or something...:hsugh
Engines work in a similar manner. Your lungs are the turbo and the straw is your engine.
Ok, I am going to bed. This is a little off-topic of your original twin vs single question but I covered that earlier.
HTH
Let us say an engine with stock cams puts down 300hp@14psi.
Then the owner adds aftermarket bigger duration/lift cams and dynos the car again without making any other changes. The new cams will allow the engine to flow more air and make more peak power but the boost pressure may have dropped some due to the cams allowing the engine to flow better than before. The end result in may be 310-320hp but at a lower boost pressure. More flow, less resistance(boost), more power.
Just a situation I made up on the spot.
Cams have other specific effects on any engine's characteristics but that is another discussion...(Probably one that can be found using search.)
If you increased boost by some small increment and watched the gains on the dyno, at some point you will hit a level where adding more boost will result in no more gains because the engine has reached its flow limit no matter how much pressure you put in the system.
Think of blowing through a thin straw. The harder you blow, the more air comes out the otherside. But if the straw is small enough(and your lungs are strong enough), at some point blowing harder will not move anymore air through the straw but you will still feel the increased pressure resistance the harder you blow... Now increase the size of the straw. You can move more air easier and you will feel less pressure resistance in your cheeks/lungs/whatever. And if you increase the straw size too much, at some point, your lungs will barely be able to keep up any pressure at all... Think of maybe a straw that is 1/8" in diameter and another straw that is 1" in diameter.
You could try this just by making the gap between your lips smaller or larger when you blow. (Just keep from passing out from blowing too hard or something...:hsugh
Engines work in a similar manner. Your lungs are the turbo and the straw is your engine.
Ok, I am going to bed. This is a little off-topic of your original twin vs single question but I covered that earlier.
HTH
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Sounds good to me Joe. I hope I dont reach my maximum until 501rwhp. Hopefully my ported and polished head can flow enough for me to reach that number.
Tissimo, I have always heard that twins flow quicker or that they spool up quicker. That was all just hearsay and I don't know where they heard it.
Tissimo, I have always heard that twins flow quicker or that they spool up quicker. That was all just hearsay and I don't know where they heard it.
read the 3rd last and last paragraphs of the first article joe put up...if in theory there was a twin turbo arrangement that had identical characteristics to a large single, the twins get to target faster, at the expense of the top end.
Of course, in the real world there are no perfect conditions, nor are there perfect twin to single equals, so everyone's findings would be a little different depending on the comparisons they tried. The physics remain the same however.
Of course, in the real world there are no perfect conditions, nor are there perfect twin to single equals, so everyone's findings would be a little different depending on the comparisons they tried. The physics remain the same however.
like mentioned, they work wonders when worked in sequential
broad powerband that comes in early and pulls to redline is the idea of a good sequential.
on a V format engine, it's usually done because it's easier to get a good strong flow right off the header instead of after a Y pipe, ect...
then you have the bugatti....
broad powerband that comes in early and pulls to redline is the idea of a good sequential.
on a V format engine, it's usually done because it's easier to get a good strong flow right off the header instead of after a Y pipe, ect...
then you have the bugatti....
suprashred87 said:
not a valid question to many variables are left undefined. you cant just make a general rule saying twins spool faster than singles it is completly dependent on the specs of the turbo and the engine. so the easiest thing for you to do is go to amazon and buy corkey bells maximum boost then you will know what to do to optimize your turbo choice instead of asking people on here who assume alot of things