Turbo versus Supercharger

Submitted: Tuesday, Aug 20, 2002 at 00:00
ThreadID: 1769 Views:1928 Replies:6 FollowUps:4
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why does a supercharger put less strain on the bottom end of a motor than a turbo. Excuse my ignorance but i would have thought that both being forced induction of a sort (one obviously being hotter than the other) then the pressure put onto the bottom ends would be similar. I have seen a few comments in this forum relating to this and if you could spare the time I would appreciate your responses on this matter.
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Reply By: Joe - Tuesday, Aug 20, 2002 at 00:00

Tuesday, Aug 20, 2002 at 00:00
John,

Assuming that both induction systems run at the same pressures, for any given rpm, then the supercharger will actually put MORE strain on the bottom end as the engine has to drive the supercharger as well as the gearbox etc.

The small myth that superchargers are kinder arises from the fact that they produce boost from virtually zero rpm so you can actually run the engine at lower revs and get decent performance from it. Turbos on the other hand need a few revs on board before they produce boost.
AnswerID: 5863

Follow Up By: John H - Wednesday, Aug 21, 2002 at 00:00

Wednesday, Aug 21, 2002 at 00:00
Joe thanks for your response. I would have thought that this would be the case. The bottom line though I think would be drive it with respect and it should last hey! Just a thought though, would you think that if you were driving a non turbo 4wd at 3000rpm (say its flat out with a heavy trailer) and a turboed 4wd at 3000rpm in the same conditions, which would be under the most pressure? The one that is turboed is going to be able to stay there easier in the hills etc. Let me know what you think. Regards JOHN.
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FollowupID: 2547

Reply By: John - Tuesday, Aug 20, 2002 at 00:00

Tuesday, Aug 20, 2002 at 00:00
Hi John,
Being involved in drag racing for a while, I can say that Turbo charging puts much less strain on most of the moving parts in your vehicle, esp the the gear train.
Turbo's have to build up manifold pressure at a rate that is somewhat dependant on exhaust flow (But also Exhaust temperature), so the engine rev range the maximum tourqe and horsepower peak thends to come on at a much slower rate than Supercharging.
Supercharging on the otherhand is mechanically governed (Directly dependant on Engine RPM) Horsepower and tourqe tend to come on at a much steeper rate , But even so the manifold pressure tends to remain at a "Vacuum" state at lower rev ranges with the throttle/s closed.
But Open the throttle/s and remove the restriction away from the intake, and look out!!....Boost rises very quickly indeed (positive pressure in the manifold).
All in All both systems Super or Turbo when producing boost in the Manifold will produce similar loads on the engine components, Supercharging produces this boost at a much more rapid rate, hence the higher stress loads on all components.

Cheers
John
AnswerID: 5864

Follow Up By: John H - Wednesday, Aug 21, 2002 at 00:00

Wednesday, Aug 21, 2002 at 00:00
John (good name that), mate thanks for your reply, would you mind reading my comments to Joe and tell me what you think.

Regard John H
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FollowupID: 2548

Reply By: Joe - Wednesday, Aug 21, 2002 at 00:00

Wednesday, Aug 21, 2002 at 00:00
John,

Given that the power required to lug a 2 tonne 4WD and a 1 tonne trailer up an incline of 10% is "X" at 80kph then it doesn't matter what the induction system is, it will require *Y" kilowatts.

So, turbo, supercharger or not the "strain' on the engine is the same.

Of course, if you have some form of forced induction then you will be able to extract more power and therfore produce more wear on your engine. It would be an unusual driver who could restrict himself and therefore limit the power production/wear, so your comparison wears a little thin.

What is the problem you are looking to solve?

As for John H's response, well in racing the frictional losses incurred in supercharging the induction would not be worth the effort over turbo charging. How many drag races are you looking at entering though?

Take a leaf out of the production engineer's handbook - look at the vehicles that get supercharged and those that get turbo charged (diesels excepted) and you will see that the supercharged vehicles are more driver response oriented and the turbos are MUCH more performance oriented. Do you want ultimate performance or the sort of easy added response that supercharging gives?
AnswerID: 5880

Follow Up By: John H - Saturday, Aug 24, 2002 at 00:00

Saturday, Aug 24, 2002 at 00:00
Joe thanks for your response once again. I am not really trying to solve a problem but you have clarified something for me, that is that it is possible that if a turbocharged vehicle is driven sensibly then the wear on the engine should really be no greater than if the engine was non turbocharged. Does that sound reasonable? I have a turbocharged 1hz troopy which I have been told, by some, can't handle a turbo and that I will have bottom end trouble etc, my argument was and still is, if you don't flog the guts out of it then it will handle the mod and there is no reason why I shouldn't have good milage out of it. Food for thought anyway. Once again Joe thanks for your time.

Regards John H.

PS No I won't be drag racing the troopy.
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FollowupID: 2625

Reply By: Joe - Sunday, Aug 25, 2002 at 00:00

Sunday, Aug 25, 2002 at 00:00
Your deduction is correct, but it is VERY difficult to not use the xtra power once you have it! Why bother with the turbo?

So, given that you will use the power it is a case of driving sensibly and minimising the effects. How about keeping the wastegate pressures turned down?

Good luck!

Joe
AnswerID: 6020

Reply By: John - Tuesday, Aug 27, 2002 at 00:00

Tuesday, Aug 27, 2002 at 00:00
Hi again,
Very similar result overall in both super or turbocharging once cruising speed has been reached, infact with the vast majority of forced induction systems be it diesel or petrol once this speed has been reached and the "acceleration load" on the engine levels out, boost actually decreases.
Boost in Supercharged (both types turbo and mechanical) engines is a result of the engine not being able to use the "charge" available to it in the intake manifold.
In supercharged(mecanical) engines the level of boost is controled by blower speed ver's engine revolutions, intake opening and engine consumption(Camshaft, displacement etc).
In turocharging the boost is governed by intake opening, engine consumption and exhaust flow but most importantly exhaust temperature.
You may have heard a diesel truck coming to the bottom of a hill , then when the truck starts to come under load as it starts to go up you can hear the turbo starting to wistle.....a result of not an increase in engine RPM or but rather an increase in exhaust temperature.
My point here is that turbos tend to be a more "self governing" thing, they don't have the response of a supercharged(mechanical) engine, they take a while to build up pressure (hence the term turbo lag). As a result of this they are regarded as being easier on the engine.
Super charging (mechanical) tends to be much more responsive and that is why it is used in competion.
Neither is ideal but I think in the everyday application a turbo wins hands down.
Manufacturers are now starting to supercharge vehicles as a result of the unpopularity of turbo lag and turbo cool down times.
Either system has the ability to harm the engine if the engine hasn't the mechanical strength to cope with the new horsepower is will produce as a result if the boost level is to high.
You will notice huge performance increases if you can pressurise the manifold around 6-8 psi,...any more is asking for trouble without bottom end mods to increase strength.
Sorry for the long post
John
AnswerID: 6060

Follow Up By: John - Tuesday, Aug 27, 2002 at 00:00

Tuesday, Aug 27, 2002 at 00:00
Just one more thing....
If ou keep the pressure down to around the 6 psi or so you will not have to many problems....Just keep the oil changes regular because the poor old oil in a turbo engine is the coolant for the turbine shaft as well as the lubricant......bad oil....that is what will increase engine wear, be warned.
Cheers again
John
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FollowupID: 2654

Reply By: John H - Tuesday, Aug 27, 2002 at 00:00

Tuesday, Aug 27, 2002 at 00:00
THANKS FOR YOUR RESPONSE JOHN. IT CERTAINLY IS STARTING TO GET CONFUSING WITH ALL THESE JOHNS THOUGH. i APPRECIATE YOUR COMMENTS AND WILL TAKE HEED TO YOUR WARNING.

REGARDS JOHN H
AnswerID: 6077

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