supercharger
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daxtojeiro
- Posts: 22
- Joined: Fri Aug 11, 2006 8:16 pm
- Location: Norwich UK
- Contact:
Hi,
without getting into it too deeply a supercharger actually takes power from the engine to produce boost where as a turbo is as near as damn it free. A turbo's outlet temp is a lot higher than a blowers so they are less efficient as far as thats concerned. Depending on the type of blower it can produce boost lower down in the rev range, but these generally become in-efficient at higher speeds and the boos level isnt particually high. The best method would be to have a blower come in at lower revs untill the turbo's boost was up to the blowers boost level then dis-engage the blower via a clutch and switch over to the turbo. I designed and fitted a supercharger setup on my old 3.5 Rv8 on the cobra before I changed it for a 5.0L, see my site for more info if your interested,
Phil
without getting into it too deeply a supercharger actually takes power from the engine to produce boost where as a turbo is as near as damn it free. A turbo's outlet temp is a lot higher than a blowers so they are less efficient as far as thats concerned. Depending on the type of blower it can produce boost lower down in the rev range, but these generally become in-efficient at higher speeds and the boos level isnt particually high. The best method would be to have a blower come in at lower revs untill the turbo's boost was up to the blowers boost level then dis-engage the blower via a clutch and switch over to the turbo. I designed and fitted a supercharger setup on my old 3.5 Rv8 on the cobra before I changed it for a 5.0L, see my site for more info if your interested,
Phil
TVR 5.0L Powered Cobra Replica
MSnS-Extra (EFI)
http://www.replica-cobra.co.uk
http://www.extraefi.co.uk for Megasquirt's
MSnS-Extra (EFI)
http://www.replica-cobra.co.uk
http://www.extraefi.co.uk for Megasquirt's
This was my thought, to have the supercharger running from start until the turbo becomes effective then shut down. Surely this can be done by having a 2 way valve operated on spring pressure between the two inlet air pressures I.E turbo pressure and supercharger pressure. This would result in instant response and maintained acceleration throughout the whole rev range.
Trying my hand at web design!!
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hybrid dreams
- Posts: 93
- Joined: Sun Aug 20, 2006 10:21 am
has been done b4 but...
IMO waste of money...personally if u r car lags then i would do...
-get a nice boost controller...quality manual ball and spring type, or a good electronic (lots of people I am sure here would give u reccomendations). dropped my lag by 300 RPM over standard boost solenoid!
-exhaust mods...downpipe/02 housing, and free flowing exhaust.
-and of course maping (which was already previously mentioned but I will mention it again) will make a big difference.
-and if lag is still an issue...look into deadbolt ball bearing turbos, and keep your turbo selection fairly small.
(currently i run the standard Evo 3 16G thrust bearing turbo...rated at 40 lb/min. capable of flowing up to 380-400ish bhp. not uncommon to hit 20+ PSI at low 3k range on the Evos once fully mapped and supporting spooling mods completed. lag isnt too bad i dont think)
If u still arent happy....then i would suggest selling your car and getting an american V8. throttle response, transient response is unparralelled. if u own a turbo car u r going to have to get used to some sort of lag.
IMO waste of money...personally if u r car lags then i would do...
-get a nice boost controller...quality manual ball and spring type, or a good electronic (lots of people I am sure here would give u reccomendations). dropped my lag by 300 RPM over standard boost solenoid!
-exhaust mods...downpipe/02 housing, and free flowing exhaust.
-and of course maping (which was already previously mentioned but I will mention it again) will make a big difference.
-and if lag is still an issue...look into deadbolt ball bearing turbos, and keep your turbo selection fairly small.
(currently i run the standard Evo 3 16G thrust bearing turbo...rated at 40 lb/min. capable of flowing up to 380-400ish bhp. not uncommon to hit 20+ PSI at low 3k range on the Evos once fully mapped and supporting spooling mods completed. lag isnt too bad i dont think)
If u still arent happy....then i would suggest selling your car and getting an american V8. throttle response, transient response is unparralelled. if u own a turbo car u r going to have to get used to some sort of lag.
BOOSTAHOLIC ;-)
Lancia did it with their Group B rally car S4.
I do like superchargers, good power and no supprises. As BigFil says you can always fit a smaller pulley. You could always have a twin Turbo setup.. I do love superchargers but I am ditching the one on the project I have for a turbo.
Depends on how much you want to spend.
I do like superchargers, good power and no supprises. As BigFil says you can always fit a smaller pulley. You could always have a twin Turbo setup.. I do love superchargers but I am ditching the one on the project I have for a turbo.
Depends on how much you want to spend.
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hybrid dreams
- Posts: 93
- Joined: Sun Aug 20, 2006 10:21 am
my 10 pennies worth
Assuming standard everything, you want an earlier spool up, OK?
One thing I found when I had my standard tubbies up rated to steel internals and roller bearings was a very noticeable increase to boost in the lower rev range - the roller bearings were responsible for this - I would also replace the boost controller as the greddy can be adjusted to help in this area as well as getting rid of the big power step at 4k
Don't know if this helps but it might be a cheaper option and it is well tried and tested.
Mark
One thing I found when I had my standard tubbies up rated to steel internals and roller bearings was a very noticeable increase to boost in the lower rev range - the roller bearings were responsible for this - I would also replace the boost controller as the greddy can be adjusted to help in this area as well as getting rid of the big power step at 4k
Don't know if this helps but it might be a cheaper option and it is well tried and tested.
Mark
There's nothing that shouts "Poor Workmanship" more than wrinkles in the Gaffer tape.....
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Bladerider
- Posts: 1597
- Joined: Sat Aug 26, 2006 2:51 am
- Location: nowhere !!!
- Contact:
Wow,
Quite a few takes on how things work in here !!!!
Compund charging (super and turbo together) is a great idea which in practice works to a degree but is expensive, heavy, overly complex and frankly not worth the bother when you can focus the car more in other ways.
The spool up on a turbocharger has nothing to do with EGT directly. It is exactly like a water wheel in that you get more turning momentum the more water flows over the wheel. In the case of a turbocharger you need more gases to flow through the turbine wheel (thats the usually grubby looking one at the rear the exhaust manifold bolts to) which is in turn connected by a shaft to the front half of the turbo - the compressor wheel - which is the bit that sucks in the fresh air and compresses it into your engine, usually through an inter or charge cooler.
Once you have got your head around how they work then its easy to see the simple ways in which you can increase their performance. As people have already mentioned, uprating the bearing can have quite a pronounced effect, as the shaft and wheels have to turn which needs support of a bearing you can get roller, or even needle roller type turbos that spin more easily with less resistance. Its this resistance which is usually described as lag - this becomes more noticeable on bigger turbos as the bigger wheels inside the larger turbos weigh more, having more inertia and also more resistive force on their bearings, therfore needing more gasflow to get them spinning upto speed (100,000rpm+).
Another good trick is to make sure there is as little airflow restriction as possible to the front and back of the turbo - this means a decent quality intake system so it doesnt have to waste energy sucking through a heavy grade filter and plastic airbox (a bit like a McD's milkshake with one straw) and also a decent turbo elbow, downpipe and exhaust system - removing the catalyst always helps here too as they are a major restriction. Dont be tempted to automatically assume that a tubular manifold will help though, as actually the "out of sync" pulses from a regular cast manifold actually help push the turbo up that bit quicker than the ultimately superior "matched length" type manifolds required for outright horsepower. I would go into this more but its very boring, so just trust me on this one !!
Other things that help can be choice of boost controller as mentioned, some of which - like the Greddy profec B - allow you to effectively over spool the turbo slightly before you hit real boost at decent revs in order to get the thing upto speed earlier. This is because as you get near the point that the turbo reaches the boost limit you set - lets say 1bar - the wastegate starts to open to syphon off any additional pressure in order to stop you going over your 1bar limit. However if this is occuring at relatively low revs, then there is no harm having this creep over the 1 bar threshold slightly (your engine map will accomodate the fueling requirements easily at such low revs) to make sure that the turbo is "well up to speed" before the wastegate opens bringing the actual pressure back to your 1bar limit. This can make a small but noticeable gain in your boost curve - 200rpms is realistic for <400bhp type turbos.
The biggest differences you can make is in the head. All aspects of what you can do to increase power via the top end is also effective on spool up, with some changes affecting power more, and others affecting flow and spool more, its up to you which is more important to you. What I mean by this is that a head that is ported to the max, is assuming a huge volume of air will be rushing through it at peak revs, and your engine builder will not be wanting the design of the inlet and exhaust ports, the valve seats and so on to be a restriction on this. However if you are not going for outright power and just want decent spool up then you would be better off with a more moddest amount of work focused on flow rate rather than outright volumetric efficiency. To put it simply, Rocket Ronnies GTR head will be looking to flow enough air to spool up a massive T51r turbo at 9000revs to acheive 900bhp. The porting, valves, inlets, exhaust, cams, and so on will all be focused on peak performance. Your GTS-t will maybe looking at 400bhp from a T3/4 style turbo at 7000revs and as such will never make enough puff through the head to warrant such oversize engineering. What you need is exactly like sticking your thumb over the end of a hose - big diameter=slow flow but lots of water, small hole=loads of flow, enough to go across your garden, but with actually less water but much more pressure. THIS is what will make your smallish turbo spin round quicker !!!
Other things that can help include well judged cam profiles and overlap, compression ratio (makes a huuuge difference), ignition advance and the general map itself. A mapper can easily make 500revs difference to the characteristics of your car using these things.
Last few things that could help are the size of your intercooler and more importantly the length of the piping from the turbo outlet to the plenum inlet - if this is too long and the intercooler too large then its a bit like blowing up a balloon, a small one will inflate almost instantly, a much bigger one takes a bit more puff to start it off !!!
Antilag and specialised systems obviously would make a huge impact here, but I wont go into them as frankly, true antilag will destroy your turbo and the poppy bangy crap as seen on alot of ECU systems isnt really worth the hassle. Nitrous Oxide is the other MAJOR cheat to help spool up, but again I wont go into it as its a non permanent solution that also requires a fair bit of in depth discussion thats probably not warranted for your requirements.
I expect I have left something out, but hope this goes some way to helping you understand the ways to do what you want.
Cheers,
J.
Quite a few takes on how things work in here !!!!
Compund charging (super and turbo together) is a great idea which in practice works to a degree but is expensive, heavy, overly complex and frankly not worth the bother when you can focus the car more in other ways.
The spool up on a turbocharger has nothing to do with EGT directly. It is exactly like a water wheel in that you get more turning momentum the more water flows over the wheel. In the case of a turbocharger you need more gases to flow through the turbine wheel (thats the usually grubby looking one at the rear the exhaust manifold bolts to) which is in turn connected by a shaft to the front half of the turbo - the compressor wheel - which is the bit that sucks in the fresh air and compresses it into your engine, usually through an inter or charge cooler.
Once you have got your head around how they work then its easy to see the simple ways in which you can increase their performance. As people have already mentioned, uprating the bearing can have quite a pronounced effect, as the shaft and wheels have to turn which needs support of a bearing you can get roller, or even needle roller type turbos that spin more easily with less resistance. Its this resistance which is usually described as lag - this becomes more noticeable on bigger turbos as the bigger wheels inside the larger turbos weigh more, having more inertia and also more resistive force on their bearings, therfore needing more gasflow to get them spinning upto speed (100,000rpm+).
Another good trick is to make sure there is as little airflow restriction as possible to the front and back of the turbo - this means a decent quality intake system so it doesnt have to waste energy sucking through a heavy grade filter and plastic airbox (a bit like a McD's milkshake with one straw) and also a decent turbo elbow, downpipe and exhaust system - removing the catalyst always helps here too as they are a major restriction. Dont be tempted to automatically assume that a tubular manifold will help though, as actually the "out of sync" pulses from a regular cast manifold actually help push the turbo up that bit quicker than the ultimately superior "matched length" type manifolds required for outright horsepower. I would go into this more but its very boring, so just trust me on this one !!
Other things that help can be choice of boost controller as mentioned, some of which - like the Greddy profec B - allow you to effectively over spool the turbo slightly before you hit real boost at decent revs in order to get the thing upto speed earlier. This is because as you get near the point that the turbo reaches the boost limit you set - lets say 1bar - the wastegate starts to open to syphon off any additional pressure in order to stop you going over your 1bar limit. However if this is occuring at relatively low revs, then there is no harm having this creep over the 1 bar threshold slightly (your engine map will accomodate the fueling requirements easily at such low revs) to make sure that the turbo is "well up to speed" before the wastegate opens bringing the actual pressure back to your 1bar limit. This can make a small but noticeable gain in your boost curve - 200rpms is realistic for <400bhp type turbos.
The biggest differences you can make is in the head. All aspects of what you can do to increase power via the top end is also effective on spool up, with some changes affecting power more, and others affecting flow and spool more, its up to you which is more important to you. What I mean by this is that a head that is ported to the max, is assuming a huge volume of air will be rushing through it at peak revs, and your engine builder will not be wanting the design of the inlet and exhaust ports, the valve seats and so on to be a restriction on this. However if you are not going for outright power and just want decent spool up then you would be better off with a more moddest amount of work focused on flow rate rather than outright volumetric efficiency. To put it simply, Rocket Ronnies GTR head will be looking to flow enough air to spool up a massive T51r turbo at 9000revs to acheive 900bhp. The porting, valves, inlets, exhaust, cams, and so on will all be focused on peak performance. Your GTS-t will maybe looking at 400bhp from a T3/4 style turbo at 7000revs and as such will never make enough puff through the head to warrant such oversize engineering. What you need is exactly like sticking your thumb over the end of a hose - big diameter=slow flow but lots of water, small hole=loads of flow, enough to go across your garden, but with actually less water but much more pressure. THIS is what will make your smallish turbo spin round quicker !!!
Other things that can help include well judged cam profiles and overlap, compression ratio (makes a huuuge difference), ignition advance and the general map itself. A mapper can easily make 500revs difference to the characteristics of your car using these things.
Last few things that could help are the size of your intercooler and more importantly the length of the piping from the turbo outlet to the plenum inlet - if this is too long and the intercooler too large then its a bit like blowing up a balloon, a small one will inflate almost instantly, a much bigger one takes a bit more puff to start it off !!!
Antilag and specialised systems obviously would make a huge impact here, but I wont go into them as frankly, true antilag will destroy your turbo and the poppy bangy crap as seen on alot of ECU systems isnt really worth the hassle. Nitrous Oxide is the other MAJOR cheat to help spool up, but again I wont go into it as its a non permanent solution that also requires a fair bit of in depth discussion thats probably not warranted for your requirements.
I expect I have left something out, but hope this goes some way to helping you understand the ways to do what you want.
Cheers,
J.
I'd have to agree with Scott here that EGT certainly has an affect in turbo spool. To give you an example in the real world*, the Porsche 944 Turbo had 2 features to specifically keep heat in the exhaust gases and quicken turbo spool-up. These were thick ceramic liners in the exhaust ports (which incidentally also helped avoid heat transfer back to the head to aid cooling) and double-walled stainless steel exhaust headers.hybrid dreams wrote:what? EGTs spools turbos? hmmm have to disagree. more like volume and velocity spools turbos.sdminus wrote:Sure....
The turbo spool is a direct result of exhaust temp in the turbo.
Scott
Cheers,
Alex
* source: Forced Induction Performance Tuning by A. Graham Bell
