Turbos

[TonyB]

Quoting peak torque figures is meaningless unless you can see the entire curve.
An engine with a lower peak torque may have an actual curve that starts sooner and is flatter than the other giving a much more flexible engine and one that'll accelerate harder in the real world. And regardless of how you do it, X amount of power requires X amount of fuel once you reach optimum volumetric and thermal efficiency.
And I'd rather hear supercharger scream than that asthmatic gasping that turbos do.

That's the point I'm trying to make- the turbo engines all make their peak torque at very low revs- much lower than the normally aspirated engines- yet the peak power is still near the red line. Therefore they have a good spread of torque and are more driveable than a normally aspirated engine (turbo lag aside). Drive an XR8 and an XR6 turbo back to back and you'll see what I mean. The XR8 needs lots of revs, whereas the XR6 turbo pulls very hard for very low down and just builds and builds as the revs rise. Why anyone would buy the XR8 after driving the turbo is beyond me.

[Jonty]

All these pros and cons go out the window with turbo diesels,they are a natural for turbo boost and it's a win/win situation all round - you don't need lower compression,you don't need more fuel,temps are cooler not higher,no strengthened parts...more power,more torque,less fuel consumption.Nearly every haulage truck,locomotive,ocean going vessel will have a turbo - it's for efficiency not power.2 stroke diesels like the Foden V12 ran twin blowers/twin turbos.

Agree - Although I notice only a few diesel tractors are turboed. I have a feeling it is to do with reliability factors in that turbos can be costly and have a habit of causing problems. Also, the turboed tractors I am familiar with have noticably better power output than the equivilent naturally aspirated machines.

Could all be in my imagination though

[Ixion]

All these pros and cons go out the window with turbo diesels,they are a natural for turbo boost and it's a win/win situation all round - you don't need lower compression,you don't need more fuel,temps are cooler not higher,no strengthened parts...more power,more torque,less fuel consumption.Nearly every haulage truck,locomotive,ocean going vessel will have a turbo - it's for efficiency not power.2 stroke diesels like the Foden V12 ran twin blowers/twin turbos.

Diesels is a whole different matter. Turbo on a diesel is a no brainer.

[Lou Girardin]

TonyB, peak power is always near the redline.
And I'd take issue with the better drivability statement. EG. the flat spot when the turbos change over on twin turbo Legacy's and Clarkson's test of a modded EVO 8 as an extreme example. There are some turbos that are hard to pick as turbos, but they're usually low boost examples. You'll never get the instant punch at zero revs that big cubes will give.

[Motu]

You'll never get the instant punch at zero revs that big cubes will give.

Or a supercharger - it's pretty hard to tell if you are driving a V8 or a supercharged V6 Commodore when you floor it off the line....if you are half deaf like me anyway....

[chris]

no strengthened parts

I thought most diesels ran stronger blocks and bottom ends than their petrol counterparts due to the much higher compression ratios.

[Ixion]

I thought most diesels ran stronger blocks and bottom ends than their petrol counterparts due to the much higher compression ratios.

I think Mr Motu meant that putting a turbo on a diesel didn't create any requirement for strengthing anything. Mainly because (as you note) diesels are already built stronger

[TonyB]

TonyB, peak power is always near the redline.
And I'd take issue with the better drivability statement. EG. the flat spot when the turbos change over on twin turbo Legacy's and Clarkson's test of a modded EVO 8 as an extreme example. There are some turbos that are hard to pick as turbos, but they're usually low boost examples. You'll never get the instant punch at zero revs that big cubes will give.

Sigh. At smoko I had a chat with one of my workmates. He gets to drive just about every new car that is test driven by his motor journalist mate. So he gets to drive a hell of a lot of cars. New cars. He confirmed what I am trying to say: once spooled up, a turbo car will make a lot of torque and therefore pull very hard all the way from say 2000rpm all the way to the peak power output. An Aussie V8 makes very little power down low. It all comes in a rush in the top half of the rev range. Infact, my mate said that when he has driven 5 or six speed manual SS, HSV, XR8 or FPV cars, and tried to roll on accelerate in a higher gear from lower revs, they simply bog down and "do nothing". When he has tried the same test in Legacy Turbos, WRX, EVO 4,5,6,7 etc etc etc they all push you back in the seat and accelerate. I also can confirm this having driven an old late 80's Mirage turbo, my dad's 90 Cefiro turbo, an 02 WRX, the bosses XR6 turbo and my own Legacy GT that ALL of these cars pull MUCH HARDER from low revs than my bosses ex VT SS and the BA XR8, and they continue to build in power right through the rev range*. Sure the XR8 has a killer rush at the end, but it doesn't do a whole lot down low. This is speaking from experience.

*Except my GT which does indeed have a flat spot as the turbo's change over. Infact, if your overtaking at around 100km/h in 4th up a steep hill, it can actually get to a point where it seems to get stuck in the middle between the primary and secondary turbo's...

So can you see what I am saying? Turbo charged engines have a much broader spread of torque and power than a conventional engine.

Edit: until such time as the turbo spools up, a big cube engine will shit all over a small turbo engine, so yeh for instant grunt big cubes are the go.... but then a good turbo with bearings etc spools up bloody quick..

[soundbeltfarm]

i wanted a super charger after watching mad max.
his car was was shit hot flick a switch and start and stop his charger whenever he wanted pity it dosnt work like that in real life.
maybe it does now though.
in 1995 me and a mate were going to import a used 350 chev super charged with a B&M mega blower for 10 grand. through a proper source.
but no one would insure us as we were pretty young.
not sure what it would be now.
but im not into the car thing anymore.

[HDTboy]

Sigh. At smoko I had a chat with one of my workmates. He gets to drive just about every new car that is test driven by his motor journalist mate. So he gets to drive a hell of a lot of cars. New cars. He confirmed what I am trying to say: once spooled up, a turbo car will make a lot of torque and therefore pull very hard all the way from say 2000rpm all the way to the peak power output. An Aussie V8 makes very little power down low. It all comes in a rush in the top half of the rev range. Infact, my mate said that when he has driven 5 or six speed manual SS, HSV, XR8 or FPV cars, and tried to roll on accelerate in a higher gear from lower revs, they simply bog down and "do nothing". When he has tried the same test in Legacy Turbos, WRX, EVO 4,5,6,7 etc etc etc they all push you back in the seat and accelerate. I also can confirm this having driven an old late 80's Mirage turbo, my dad's 90 Cefiro turbo, an 02 WRX, the bosses XR6 turbo and my own Legacy GT that ALL of these cars pull MUCH HARDER from low revs than my bosses ex VT SS and the BA XR8, and they continue to build in power right through the rev range*. Sure the XR8 has a killer rush at the end, but it doesn't do a whole lot down low. This is speaking from experience.

*Except my GT which does indeed have a flat spot as the turbo's change over. Infact, if your overtaking at around 100km/h in 4th up a steep hill, it can actually get to a point where it seems to get stuck in the middle between the primary and secondary turbo's...

So can you see what I am saying? Turbo charged engines have a much broader spread of torque and power than a conventional engine.

Edit: until such time as the turbo spools up, a big cube engine will shit all over a small turbo engine, so yeh for instant grunt big cubes are the go.... but then a good turbo with bearings etc spools up bloody quick..

I know from experience that a 170Kw naturally aspirated 330i has a lot smoother torque curve, and pulls harder and lower than my 165Kw turbo skyline
A4L XR6 turbo will pull hard anyway because it has 4L, the low down torque in these cars comes from big cubes, your GT legacy probably hsa a little turbo to get it moving.
The previous generation of aussie V8s made torque at lower revs than the latest ones, they've moved the powerband higher in the rev range

[chris]

Turbosupercharger

[Ixion]

I think Mr Motu meant that putting a turbo on a diesel didn't create any requirement for strengthing anything. Mainly because (as you note) diesels are already built stronger

hm. Strengthing. I like that word. Mr Hitcher, please add strengthing to the offical dictionary.

[Motu]

I know turbo pistons in the 4D56 Pajero are different than non turbo - but some use non turbo pistons because they are cheaper....and the total piece of crap motor will self destruct before the pistons do.The DOHC Turbo motor in my Charade was a thing of joy inside - the forged pistons made more noise than a 501 Maico but were strong as,a strengthening (long version of the choice word) bridge over the bottom end had 2 squirters to each piston and the head had a wide valve angle with 4 valves...it put out 100HP from 1000cc and were raced with 3 times the boost reliably.One of the best big grin cars I've driven.

[sedge]

The old MR2s came out with a supercharger and were pretty fast... HKS did a 'twincharger' kit that added a big pulley, big injectors, management computer and BIG turbo etc... So you got boost from idle via the SC and then when the turbo spooled up you got more.

Base kit was 300HP (they already had forged pistons and strong crank etc)

The kit was able to be used under warranty at this output , most people who added it then let the turbo spool up to it's potential... 500HP+... Heh heh... What a nice little car, I always wanted one.

Oh yeah, 1600cc, reasonably light, mid engined, t-top, midnight blue - 500HP+

One of these days I'll get one...

Sedge.

[dangerous]

What I want to know, is given the theory of how both work, can they both be bolted to one engine? The supercharger will give you the boost off the lights, the turbo will give the power up the rev-range..

Yeah mate trucks have used that theroy for years in OZ I was driving a V8 Kenworth that was a two stroker deisel with a supercharger and two turbos....... ohhhhh, wicked

I'd love to fit a small turbo to my bike, not for the power increase, but just to hear the whoosh from it..

Been there done that and its fuking awesome

Thought the anti lag system fed the over boost from the waste gate back to the inlet of the turbo, to keep it spinning?

pressure release or 'blow off' valves release the pressure from the manafold during a gear change which allows the turbo to spin freely.... other wise as the engine revs drop during the gear change so does the turbo.... it then has to wind up again ie: lag