Turbo vs Supercharger question

[seschm1234]

Been following the development of the 2.3 liter Ecoboost twin scroll turbo engine that is just appearing and it seems like an interesting candidate for 7's. GIven the 7's low mass a supercharger is used most times for the very quick throttle response rather than a turbocharging system. The Mercedes F1 team this year has coupled a motor to their compressor to speed up this process and eliminate lag. My question is this... Engines performance is generally given as torque/power vs speed but this doesn't capture the lag associated with the turbocharged system and the inertia of the turbo and pressurization of the manifold. Is there a generalized parameter in the engine world that captures this relationship?

 

Thanks

 

Paul

[Off Road SHO]

Modern turbos don't have much lag. I also think the new EcoBoost engines would be great in a seven.

 

Tom

[turboeric]

The answer to 'how much turbo lag' is always 'it depends'. It is very set-up dependent. For years, VW has used tiny, tiny turbos on their 1.8T and 2.0T gas motor to beef up low end torque, and there's really no perceptible lag, but they run out of breath pretty quickly. Ford's more complex EcoBoost system accomplishes the same thing, but with a little more top end capability. The much bigger turbo on my Miata lags noticeably, but on track you can always keep it on the boil and the ultimate volume of boost is much higher, hence more hp.

 

That said, I think you're right about the Ford motors being interesting transplant candidates.

[BusaNostra]

My preference is supercharger.....I hate heat in the 7 engine bay.

The power is linear - good for race track.

[Blokko]

I had a conversation on this subject with a kit car manufacturer at Stoneleigh kit car show. Was told that the Ford EcoBoost engine as used in the UK (1 litre 3 pot turbo, kicking out anything from 100bhp to 175bhp and beyond) is not suitable for 7 type vehicles as the engine is too tall. Not sure if the same would apply to this 2.3 unit being described by the original poster....

[WestTexasS2K]

Like Busa I like the Rotrex supercharger, but it doesn't make as much power as a turbo. Heat is an issue with turbos and LSIS cars can be hot as it is. A good quality ball bearing turbo properly sized will give big power with very little lag. I just don't want the heat under the hood.

[sdca7]

I track a turbocharged larger car, and the "lag" really isn't a problem. Even the smallest engines in sevens have enough power to throttle steer through corners, and you don't need tons of low end torque on the track. And on track your revs will be up anyway, so there is always some pressure built up. You really could argue that in many situations a big turbo which does not come on strong at lower rpm's will give you lots of potential power on the straights, where you really need it, without the excessive low end grunt that can make it difficult to manage the throttle coming out of corners. Either way, I have found that the "turbo lag" has not been a problem for me on track, even with a heavy car and huge turbos.

 

That being said, I would prefer to put a Rotrex on my seven if it were easy to do! Someone come up with a kit for us!

[Bonjo2]

I think a 1.8-2.0 twin scroll would be perfect for a seven--much better than my current LS motor. I had a subaru friend that did the twin scroll and his car was nuts, and with only a 2.0. Lots of torque. My car had a bigger turbo and faster 1/4 mile trap speed, but his car was so much quicker where it mattered. It's like doubling the torque of your displacement picking up at 1600rpm vs. 35, or 4500rpm.

 

Can you share a link to the seven?

[dhubbard422]

A friend of mine did "this" to his Talon... Yes, he is a bit nuts. :smash:

 

http://gearboxmagazine.com/rays-twincharged-talon/

 

If you look at the pic, you'll notice that the turbo feeds the supercharger, i.e. in a crude sense, the supercharger simply multiplies what ever the turbocharger gives it. Which means giant boost at insanely low RPMs. This little motor is really powerful and it makes big power everywhere in the RPM range.

 

However, it is a lot of plumbing... it might be hard to fit all of that plumbing in a traditional 7, but, Ray believes it just might work. :jester:

 

Traditionally, big boost numbers from a turbo require time (i.e. RPMs) to spool up while superchargers can make nice, if modest, boost right off the bottom. If you're driving a street-able turbo and has little to no lag, it generally makes fairly small boost pressures so that it can spin up quickly. However, I'm not an expert and I wouldn't be surprised if there are exceptions to that rule of thumb...

[Mondo]

I know "more is always better" but the new Kraftwerks supercharger on my S2K will make 400 linear horsepower!

Just got to get my kid through college first... then give West Texas a call

[Blokko]

At one stage one of the smaller engines in the Volkswagen Group range (also used on Skoda's, Audi's Seat's) contained both a supercharger and a turbocharger, though only one ran at any one time.

 

From http://en.wikipedia.org/wiki/List_of_Volkswagen_Group_petrol_engines

 

 

Based on the EA111, this new engine was announced at the 2005 Frankfurt Motor Show, to be first used in the Mk5 Golf GT, the 125 kW 1.4 litre TSI engine is a "Twincharger", and uses both a turbocharger and a supercharger. Its displacement downsizing leads to improved fuel economy, with 14% more power than the 2.0 FSI, but consuming 5% less fuel. The mechanical supercharger compressor, driven at 1.5 times the speed of the crankshaft, mainly operates at low engine speeds from tick-over up to 2,400 revolutions per minute (rpm) to increase low-end torque. At engine speeds just above idle, the belt-driven supercharger provides a boost pressure of 1.2 bars (17.4 psi). The turbocharger assumes full effectiveness at middle revs, and the engine map disengages the clutch-controlled supercharger at a maximum upper limit of 3,500 rpm; the supercharger will then be bypassed once the turbocharger spools up and reaches sufficient speed to provide adequate boost in the upper rev-ranges

[westy turbo]

2.3 Eco is already boosted if am correct,so no need for an up rate unless you want silly numbers,so stock turbo means no lag.

[TurboWood]

It will definitely be interesting to see if the 2.3L eco fits in a Caterham. I believer there was a VVT version of the Duratec that from my understanding does not fit (too tall). The same story for the K24 and S2k engines (Honda). It is a wicked engine though.

 

Turbo lag really needs to be broken down into two categories, time to boost and boost/tq peak engine speed. If you plant your foot at a low engine speed the boost will build slowly as engine speed increases. If you go WOT at 5000rpm the response will be quite good. With electronics today you can even tune the ramp rate of boost to prevent unpredictable power delivery.

 

That said, an engine with individual throttle bodies or a blower is hard to beat for response. Turbos are just more fun (in my very biased opinion). There are also many heat shields available to help manage additional heat in the engine bay.

 

Daniel

[RGTorque]

turbowood, s2k engines fit just fine in our cars. many guys get a oil pan sump for better protection, but otherwise its fine for street driving.

[TurboWood]

Roman, are you talking about a westfield or a caterham?