Turbo V Supercharger?
Discussion
I'v never had cause to complain about lag on anything I'v built or driven. If the compression is reasonably high and the boost modest then I don't see lag being detectable. If on the other hand you use low compression and a big turbo or high boost then sure there will be loads of lag especially on a small engine but this set up wouldn't be very suitable as a daily driver. Street cars should respond really well to low boost turbo's if designed correctly.
I have to say this has to be one of the most informative posts i have read in a long while, i'm a huge fan of turbo's but dont know alot, i drive a mkiii supra turbo only running 12 psi at the moment but you certainly feel it 
if people do get lag these days after modding to run higher boost they tend to use a 25-50 shot of nos to eliminate lag
if people do get lag these days after modding to run higher boost they tend to use a 25-50 shot of nos to eliminate lag
fatbutt said: Surely this is just an arguement over lag? With a turbo car you get lag (unless you drive constantly at medium to high revs). Normally aspirated and supercharged don't have lag.
You can get a greater rush from turbo'd cars and more efficiency but...
So, its all down to whether you want lag, barely perceptable or not.
Personnally, I like smooth delivery so its either capacity or supercharger - I wouldn't touch a turbo with a bargepole (yes I have driven a fair few on hire, hence my opinion!).
Lag or not, the power boost doesn't cut in until the engine hits a certain rev speed.
Turbos appeal to those who like their engines "peaky".
Superchargers add power across the entire range and in a much more transparent fashion and are favored by those who like their low-end grunt.
This is why you may never see a turbo-charged Jaguar. (Yeah, I know the XJ-220 had twin turbos, but that was a fluke - a quick-fix to solve their packaging problems with the V12 without giving up power)
i only have 2 experiences of turbo cars on a regular basis, a 1293 mini turbo, and a mondeo turbo diesal, the mini had realy poor initial pullaway but once it kicked it, it never lagged, unless u had to slow down, btu what i did notice was , if u slected the right gear, when comin out of corners lag wasnt a porblem, although that was nearly 2 years ago, i cant rightly remeber much, i was only a wee pup, at 17, the second experience was with teh mondeo diesal, which is about teh same, once u get going and chosse the right gear its goo, but except mine dont have anything over 3500rpm, so u get lots of pull, but dotn actually gain much speed, as for superchargers, i used to be well into teh concept of superchargers, but when i researched them more, they didnt seem as good as i once percieved. due to many things such as poor efficency,id rather put a big v8 in a car, rather than have a supercharger. bolted onto a smaller car , as a matter of interest , in drag racing, which type do they use, turbo or super, or both, seen a modded xr2 ith both once, dont no how effective both is, i fink they only managaed to get 170 bhp from both type on the same car,
randy said:
Turbos appeal to those who like their engines "peaky".
Turbo engines are not 'Peaky'. They can have lag but once the turbo has spooled up the torque curve is normally very flat.
Low capacity, high reving NA engines are the peaky ones.
Randy,
You're correct. In fact, on a turbo system, once the turbo has spooled up to full boost, it is the wastegate's responsibility to see to it that the boost is perfectly linear by changing turbo speed to account for fluctuations in volumetric efficiency. So, a turbo's torque curve is always more linear than a blower's in the mid-range and top-end revs.
And, since the whole point of forced induction is increased power, save for those few, primarily younger, drivers who merely want to customize their ride, a turbo can provide increased boost (read:Power) to ranges not possible with a blower.
Add to that the fact that each pound of boost increases torque approximately 8%, and you'll find that in a phenomenon called 'crossover', turbochargers can generate much higher intake manifold pressure than exhaust back pressure. At this point, power just goes ballistic.
If speed is your thing, it is difficult to find a factory supercharged car which is faster than the slowest factory turbocharged cars.
So, as has been mentioned, it seems the only debate is whether initial turbocharger lag is annoying enough to forego it's inherent advantages in favor of a less efficient, lower power producing and slower supercharger. Happy Motoring...Jim '85TE
Lotusguy,
You keep mentioning wastegates importance in delivering a moderated and linear level of boost. This has given me cause for concern. My ECU controlled solenoid fed wastegate gave a gently spool up and l'm sure was sophisticated, but it one day decided to drop boost by a third from 3500 to 5000 before going through the roof thereafter.
After some consideration l isolated it and used a relief and manual bleed in sequence to replace it. I only have a Garrett T2 but as far as i'm concerned the external wastegate now provides little more function than a safety limiter. Can you explain what advantages l have lost with this solution?
You keep mentioning wastegates importance in delivering a moderated and linear level of boost. This has given me cause for concern. My ECU controlled solenoid fed wastegate gave a gently spool up and l'm sure was sophisticated, but it one day decided to drop boost by a third from 3500 to 5000 before going through the roof thereafter.
After some consideration l isolated it and used a relief and manual bleed in sequence to replace it. I only have a Garrett T2 but as far as i'm concerned the external wastegate now provides little more function than a safety limiter. Can you explain what advantages l have lost with this solution?
Electronic control of the wastegate signal is used to prevent "creep" of the wastegate actuator.
This phenomenon occurs as the pressure in the manifold builds up, and causes the actuator to start opening the wastegate before full boost is acheived.
The electronic control basically holds the wastegate closed until a set level of boost is reached, say 9psi, and then opens it to control the turbine speed.
The advantage of using this type of control is that boost rises rapidly so giving that kick that is desired.
Without it, the wastegate will start opening well before full boost, bleeding off pressure continually until the correct level is acheived.
The power delivery will be more linear if this occurs, but the turbo is working harder to meet that 9psi level.
Hope this helps.
This phenomenon occurs as the pressure in the manifold builds up, and causes the actuator to start opening the wastegate before full boost is acheived.
The electronic control basically holds the wastegate closed until a set level of boost is reached, say 9psi, and then opens it to control the turbine speed.
The advantage of using this type of control is that boost rises rapidly so giving that kick that is desired.
Without it, the wastegate will start opening well before full boost, bleeding off pressure continually until the correct level is acheived.
The power delivery will be more linear if this occurs, but the turbo is working harder to meet that 9psi level.
Hope this helps.
funkihamsta said: Lotusguy,
You keep mentioning wastegates importance in delivering a moderated and linear level of boost. This has given me cause for concern. My ECU controlled solenoid fed wastegate gave a gently spool up and l'm sure was sophisticated, but it one day decided to drop boost by a third from 3500 to 5000 before going through the roof thereafter.
After some consideration l isolated it and used a relief and manual bleed in sequence to replace it. I only have a Garrett T2 but as far as i'm concerned the external wastegate now provides little more function than a safety limiter. Can you explain what advantages l have lost with this solution?
Funki,
Your post isn't really that clear, but from what I can derive, you had an ECU fault, most probably a vacuum or other sensor failure I suspect. This caused the ECU to send the wrong signal to your wastegate controller resulting in lower boost pressures. But, instead of identifying and solving the problem, you have circumvented it.
By fitting an external wastegate, which I presume does not have a vacuum link to the engine, you have merely relegated it to the role of 'Safety Valve' and lost all dynamism relative to engine speed. Again, I presume this external wastegate's operation is governed by a spring modulated plunger. This plunger overcomes the spring pressure once the exhaust pressure reaches a specific level and opens the wastegate to relieve the exhaust pressure thus reducing the power turning your turbo.
You really need to isolate the problem in or to the ECU to allow the wastegate to modulate, rather than regulate, the turbo speed and restore the real time dynamic adaptibility to the system. Hope this helps...Happy Motoring...Jim '85TE
>> Edited by lotusguy on Wednesday 15th January 21:33
Deltaf,
Agreed. With a manual bleed, wastegate creep is a problem, which is why l have installed a relief valve. This and the manual bleed give a rapid spool up, and hold a steady boost level. (Took a lot of adjustment)
Lotusguy,
Apologies if my post wasn't clear.
The ECU solenoid only ever had one vacuum pipe going to it from the turbo itself (prior to the intercooler). From here it either bled off air into the exhaust pipe via another pipe or directed it to the wastegate diaphragm. Not rocket science plumbing. This same vacuum pipe now goes through the manual workaround.
The activity of the solenoid would probably be programmed to deliver to give a nice steady boost spool, nothing too surprising for the daily drive. It would take into account other feeds such as temperature and as you suggest probably engine speeds and so on. I agree that l should address the original problem (like a faulty solenoid or temp sensor etc...) but l am still failing to appreciate what l am actually losing here. Its no Porsche!
Agreed. With a manual bleed, wastegate creep is a problem, which is why l have installed a relief valve. This and the manual bleed give a rapid spool up, and hold a steady boost level. (Took a lot of adjustment)
Lotusguy,
Apologies if my post wasn't clear.
The ECU solenoid only ever had one vacuum pipe going to it from the turbo itself (prior to the intercooler). From here it either bled off air into the exhaust pipe via another pipe or directed it to the wastegate diaphragm. Not rocket science plumbing. This same vacuum pipe now goes through the manual workaround.
The activity of the solenoid would probably be programmed to deliver to give a nice steady boost spool, nothing too surprising for the daily drive. It would take into account other feeds such as temperature and as you suggest probably engine speeds and so on. I agree that l should address the original problem (like a faulty solenoid or temp sensor etc...) but l am still failing to appreciate what l am actually losing here. Its no Porsche!
funkihamsta said: Deltaf,
Agreed. With a manual bleed, wastegate creep is a problem, which is why l have installed a relief valve. This and the manual bleed give a rapid spool up, and hold a steady boost level. (Took a lot of adjustment)
Lotusguy,
Apologies if my post wasn't clear.
The ECU solenoid only ever had one vacuum pipe going to it from the turbo itself (prior to the intercooler). From here it either bled off air into the exhaust pipe via another pipe or directed it to the wastegate diaphragm. Not rocket science plumbing. This same vacuum pipe now goes through the manual workaround.
The activity of the solenoid would probably be programmed to deliver to give a nice steady boost spool, nothing too surprising for the daily drive. It would take into account other feeds such as temperature and as you suggest probably engine speeds and so on. I agree that l should address the original problem (like a faulty solenoid or temp sensor etc...) but l am still failing to appreciate what l am actually losing here. Its no Porsche!
Funki,
The thing to understand here is that with the ECU controlling the wastegate opening, it's variable - not all or nothing. If the wastegate partially closes, the turbo speeds up, but not to max boost, conversely, partial opening causes the turbo to slow down, but not below producing appreciable boost. This variance is governed by engine speed and throttle position. Since the turbo is still spooling, it produces some boost and reduces some or all of the lag. Hope this helps...Happy Motoring...Jim '85TE
But wouldn't a set up that was all or nothing to say 5psi but then bled off a percentage over that allow partial opening of the wastegate (This one starts opening under 3psi direct pressure anyway). This would allow part boost under part throttle etc...
Still can't figure why the old system would be any better at keeping the turbo spooling at part throttle. I'm not sure lag is an issue here. Anyway hasn't this thread just determined that wasn't a problem!
BTW Thanks for taking the time to address my ignorances, hope l haven't driven you to distraction just yet!
Still can't figure why the old system would be any better at keeping the turbo spooling at part throttle. I'm not sure lag is an issue here. Anyway hasn't this thread just determined that wasn't a problem!
BTW Thanks for taking the time to address my ignorances, hope l haven't driven you to distraction just yet!
lotusguy said:
randy said:
Turbos appeal to those who like their engines "peaky".
Turbo engines are not 'Peaky'. They can have lag but once the turbo has spooled up the torque curve is normally very flat.
Low capacity, high reving NA engines are the peaky ones.
Randy,
You're correct. In fact, on a turbo system, once the turbo has spooled up to full boost, it is the wastegate's responsibility to see to it that the boost is perfectly linear by changing turbo speed to account for fluctuations in volumetric efficiency. So, a turbo's torque curve is always more linear than a blower's in the mid-range and top-end revs.
And, since the whole point of forced induction is increased power, save for those few, primarily younger, drivers who merely want to customize their ride, a turbo can provide increased boost (read:Power) to ranges not possible with a blower.
Add to that the fact that each pound of boost increases torque approximately 8%, and you'll find that in a phenomenon called 'crossover', turbochargers can generate much higher intake manifold pressure than exhaust back pressure. At this point, power just goes ballistic.
If speed is your thing, it is difficult to find a factory supercharged car which is faster than the slowest factory turbocharged cars.
So, as has been mentioned, it seems the only debate is whether initial turbocharger lag is annoying enough to forego it's inherent advantages in favor of a less efficient, lower power producing and slower supercharger. Happy Motoring...Jim '85TE
Who are you kidding? Harder to find a factory supercharged car that is faster than the slowest factory turbo-charged car?
Tell you what, I'll hop in my XJR and you can have whatever you think is a turbo-charged equivalent and we'll compare notes. Just out of curiosity, on what do you base your claim? What do you consider comparable in this situation?
In the meantime, I may not agree with Gordon Murray on some things but none of them are engineering-related. I agree, for example, with his opinion of the inferiority of turbo-chargine vs normal-aspiration or supercharging as expressed in that pissy interview he gave in a recent car mag.
Now, would you like to tell Mr. Murray that he's wrong and that he should have turbo-charged the McLaren F1?
JonGwynne said:
lotusguy said:
randy said:
Turbos appeal to those who like their engines "peaky".
Turbo engines are not 'Peaky'. They can have lag but once the turbo has spooled up the torque curve is normally very flat.
Low capacity, high reving NA engines are the peaky ones.
Randy,
You're correct. In fact, on a turbo system, once the turbo has spooled up to full boost, it is the wastegate's responsibility to see to it that the boost is perfectly linear by changing turbo speed to account for fluctuations in volumetric efficiency. So, a turbo's torque curve is always more linear than a blower's in the mid-range and top-end revs.
And, since the whole point of forced induction is increased power, save for those few, primarily younger, drivers who merely want to customize their ride, a turbo can provide increased boost (read:Power) to ranges not possible with a blower.
Add to that the fact that each pound of boost increases torque approximately 8%, and you'll find that in a phenomenon called 'crossover', turbochargers can generate much higher intake manifold pressure than exhaust back pressure. At this point, power just goes ballistic.
If speed is your thing, it is difficult to find a factory supercharged car which is faster than the slowest factory turbocharged cars.
So, as has been mentioned, it seems the only debate is whether initial turbocharger lag is annoying enough to forego it's inherent advantages in favor of a less efficient, lower power producing and slower supercharger. Happy Motoring...Jim '85TE
Who are you kidding? Harder to find a factory supercharged car that is faster than the slowest factory turbo-charged car?
Tell you what, I'll hop in my XJR and you can have whatever you think is a turbo-charged equivalent and we'll compare notes. Just out of curiosity, on what do you base your claim? What do you consider comparable in this situation?
In the meantime, I may not agree with Gordon Murray on some things but none of them are engineering-related. I agree, for example, with his opinion of the inferiority of turbo-chargine vs normal-aspiration or supercharging as expressed in that pissy interview he gave in a recent car mag.
Now, would you like to tell Mr. Murray that he's wrong and that he should have turbo-charged the McLaren F1?
Jon,
You obviously have strong feelings. However, I find your claims are more often than not based on anecdotal rather than empirical evidence.
You appear to derive significant satisfaction in isolating a word or phrase out of context and challenging it. Yet, you seem unable to sway anyone by your arguments and don't appear to fully understand the topic in depth.
I have no wish to debate you on the topic. The information I have relayed here is not my own opinion, but derived from much reading and research. I can give you the calculations and formulas used as well as numerous examples, but as it seems this thread has broken down to more of a 'Stump the Band' or 'Yea, but what about...?' arguments citing unique examples or conditions, I will defer
...Happy Motoring...Jim '85TE
>> Edited by lotusguy on Thursday 16th January 16:46
>> Edited by lotusguy on Thursday 16th January 16:49
JonGwynne said: Who are you kidding? Harder to find a factory supercharged car that is faster than the slowest factory turbo-charged car?
Tell you what, I'll hop in my XJR and you can have whatever you think is a turbo-charged equivalent and we'll compare notes.
I understood it to mean that if Jaguar produced a turbocharged XKR as well as a supercharged one the turbo car would produce more ultimate power.
kevinday said:
JonGwynne said: Who are you kidding? Harder to find a factory supercharged car that is faster than the slowest factory turbo-charged car?
Tell you what, I'll hop in my XJR and you can have whatever you think is a turbo-charged equivalent and we'll compare notes.
I understood it to mean that if Jaguar produced a turbocharged XKR as well as a supercharged one the turbo car would produce more ultimate power.
...And be faster, turbo lag and all...Happy Motoring...Jim '85TE
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