[Oldman]

Re: (quick)

and I may add, this is all WOT theory, low speed, part throttle, there is no way to make the turbo spool except of course to make it smaller. My turbo OEM stock shows boost as low as 1500 RPM and with part throttle. There is no way a bigger turbo is going to make the same boost at the same throttle setting. Volvo knows this and decided to go with a low pressure setup thinking that is what say 80% of the market wants. Not like the S40 is a dog it is quick enough and with chip only I have been able to keep up with SRT-4s thu the gears, nuff said.

I have build and used many VNT turbos and they work great for diesels but cant take gasser heat and lack of lub.

 

[quick]

*very* good points, oldman.

Part-throttle response and lag characteristics are just as important if not more important than WOT spool.
-Chris

 

[Oldman]

Re: (quick)

It is all based on volumetric efficiency, squeeze and spark timing, Volvo uses miller cycle or similar technology to boost fuel economy. Volvo uses turbo boost to up VE which is very similar in upping the CR ratio, but with the added benefit of delivering the higher virtual CR further up in the RPM range where load ( second order differential of piston position aka acceleration of the piston) and detonation is less of an issue. Think of it this way you can increase CR by physically reducing the size of the combustion chamber OR by increase the VE of the engine; of course in the latter the physical CR is the same but the virtual CR is much higher as more air and fuel is squeezed into the same area.

So what is the end result? 1500 RPM 3PSI of boost, the engine behaves with the torque of a 2.9 liter engine due to the increase VE AND due to the higher pre ignition temperatures / pressure the engine behaves as a high CR 2.9 liter engine. This is a direct result of squeezing more air into the same size combustion chamber. The true end results are 30 MPG from 3400 lbs on a day in day out basis on regular fuel, on an engine that feels like a V8.

 

[tmtalpey]

Re: (Oldman)

Quote, originally posted by Oldman »

Volvo uses miller cycle or similar technology to boost fuel economy.

You have a reference for that? I thought Miller cycle engines needed a supercharger, to hold pressure during the compression stroke.

The S40's T5 does have CVVT, which is capable of Miller-style timing but it mostly manages valve overlap and the like, not a true Miller cycle.

Tom.

 

[quick]

Re: (tmtalpey)

Quote, originally posted by tmtalpey »

The S40's T5 does have CVVT, which is capable of Miller-style timing but it mostly manages valve overlap and the like, not a true Miller cycle.

Are you saying that the V50's T5 doesn't have this?

 

[Pat'sNewV50]

Re: (Nebor)

Quote, originally posted by Nebor »

... And the AWD systems in the two cars can't even be compared.

While everyone else is talking about hoursepower, torque and turbos, I would like clarification on this comment. From the tone you your post, I will assume your prefence is towards Subaru. When I was looking at AWD systems, everyone said Subaru were the masters. Well I think Haldex (who also make AWD for Land Rover amoung others) know a thing or two and I think theirs is a great system. Volvo/Haldex has a slightly different bias philosophy but one I tend to agree with and the Volvo AWD (especially enhanced by DSTC) is every bit as good as Subaru (dare I say, if not better) for performance & handling under all possible road conditions from best to worst.

 

[dpinto1]

Re: (Pat'sNewV50)

Quote, originally posted by Pat'sNewV50 »

Volvo/Haldex has a slightly different bias philosophy but one I tend to agree with and the Volvo AWD (especially enhanced by DSTC) is every bit as good as Subaru (dare I say, if not better) for performance & handling under all possible road conditions from best to worst.

Torque steer, wheel hop and understeer are not things i admire in a awd system.

If the Legacy's cabin wasn't made out of cheap plastic i think Volvo would be having an even tougher time selling cars. No more Haldex junk for me.

 

[tmtalpey]

Re: (quick)

Quote, originally posted by quick »

Are you saying that the V50's T5 doesn't have this?

Doesn't have what? The T5 (and the 2.4i actually) has CVVT (Continuously Variable Valve Timing), which is key to the engine's efficiency and torque, but I don't consider it to be a Miller cycle engine.

Quote, originally posted by dpinto1 »

Torque steer, wheel hop and understeer are not things i admire in a awd system. ... No more Haldex junk for me.

Huh? My T5 AWD exhibits absolutely zero torque steer (I can do a hands-off full-throttle sprint), zero wheel hop, and once I got rid of the stock tires, relatively little understeer. Do we have the same car?

Tom.

 

[Oldman]

Re: (tmtalpey)

note I said "or similar", in all probability Volvo changes both cams in order to reduce the overlap to minimize the filling of the cylinder yet still retains the same physical stroke while a true miller would delay the closing of the intake valve (requires a supercharger) ejecting some of the charge back into the intake: the end result is the same. As an added benefit there would some passive EGR that would be present in the reduced cam overlap that is not there in a true miller.

Modified by Oldman at 9:02 PM 5-20-2006

 

[tmtalpey]

Re: (Oldman)

Yes, the T5 uses CVVT on both cams. (The 2.4i just on the intake.) There is definitely overlap, largest in moderate engine load situations. The cam timing algorithms are pretty interesting.

Tom.

 

[warmonger]

Re: (quick)

Quote, originally posted by quick »

Quote, originally posted by warmonger » It was intended to point out that there are Turbos available that can spool quicker at lower rpm and still be efficient enough to provide more airflow at higher rpms. No. There is no such thing as a free lunch. If it spools fast enough to provide near instant torque it will die on the top end. (Unless it's VATN or something)

Out of context quotes....when if you'd have just read the original post you'd have seen the very next sentence said the same thing you did and gave substance to the claim?

Quote, originally posted by warmonger »

It was intended to point out that there are Turbos available that can spool quicker at lower rpm and still be efficient enough to provide more airflow at higher rpms. I'm not saying you get something for nothing, but you can have better performance than what we have, with just as much low-end torque and MORE high end torque. However you will sacrifice fuel economy.

So all my statement was pointing out is that we could improve higher rpm torque while keeping similar low end torque.....in effect better than what we have....as I said. But at costs. I never said spool would be the same.
To me, I'll sacrifice 500rpm of spool for 500-1000 rpm of efficiency higher up the rev range ANYDAY, especially when this thing spools off idle as it is. I don't launch at 1200 rpm, I don't normally drive at 1200rpm in cruise, therefore I don't care that it currently spools at like 1200rpm. I'd rather it spool to 10psi by 2000-2500rpm and be able to hold it efficiently through 6000 rpm.

With the newer turbos today the metallurgy allows us to have new cartridges with ball bearings and less friction as well as lower mass turbine/compressor wheels. This IS a direct benefit to spooling at lower rpm while having both the turbine and compressor sized to be more efficient at higher rpm. It won't actually replace the effect of sizing a smaller turbine though, but it will extend the efficiency range. Without VATN.

But VATN would be the poop, especially if it was practical and affordable.

 

[Oldman]

Re: (warmonger)

here is a logical counter, for any given turbo that you would find that would fullfill, your claim there is one that is slightly smaller that will spool slightly quicker and spool even better at part throttle i.e. perform better during 99.9% of normal driving.

Yes we all agree there could have been a slightly biggert setup, a high pressure setup, I would have got that instead, but ya know with $3.00 gas and the ability to use cheap pump gas with little loss in everyday street manners, maybe it was good that I ended up with a LP setup. Now if that is me, an avid racer and street fighter, I would assume that the vast majority of T5 owners would buy or now are glad to have a LP setup. Chip only the T5 can keep up with SRT-4s nuff said.

Modified by Oldman at 1:15 PM 5-21-2006