drb5

iTrader: (4)

hairy muf, cosworth

Cosworth427

Did you time the spool up yourself??? Turbos *do* take a while to spool when at low revs and low power. Especially with smaller engines.

Remember, you *need* power to make power with a turbo. Exhaust energy must be sufficient to spool the turbine quickly. Exhaust energy is derived from horsepower generated....so.... HOW MUCH horsepower does a 2 litre OFF-BOOST make at 2000 RPM? ...20 HP?....30 HP even?

Remember, revs do not climb quickly, you will be around those low revs for a few seconds, stuck with limited power output. The turbo doing what it can with little exhaust energy driving the turbine blade.

Within those seconds, the natural aspirated car will be ahead, it would have covered more distance and effectively overtaken you.

There is no advantage gained for the BMW whether it was tested while rolling or from hitting throttle, remember power is available instantly with a natural aspirated car.

juan

How often are you travelling at 30mph in top gear Cosworth?, particularly when anticipating some kind of rapid acceleration manouvre. The conditions you choose to make some of your arguments just aren't realistic.

Maybe you should get yourself an XKR and then you might be happy. Supercharger and auto for you.

CraigH

Beef, I think you've answered the question yourself It's still got lag, no matter what hasn't it? Even the Merc 6litre V12 TT has a little lag.

WRX280

No point arguing with Cossie...been there done that.

He's like a baby throwing his toys out the pram when people disagree with him

Phil M

Yeah the situation might not be very realistic but your still missing the point, the only point he's trying to make is that a turbo engine does lag and this is just an example of that situation.

forget asbout using topgear for a minute. my mate has an EVO 5 std apart from some exhaust. when he floors it in 2nd gear at 2k jack **** happens till u get to 3.5 - 4k.. another mate happens to have an M3 and i've had the pleasure of a ride in a csl, when you put your foot down at 2k it starts to take off quite rapidly. this does happen in the real worls, when you dont quite stop coming up to junctions and you want to pull away fairly quickly in 2nd gear, at 2k in an evo you'd have a 20tonne truck up ur *** unless you were in 1st

evo39

And a normally aspirated engine engine will take time to get into its powerband. Especially a peaky high revving one like the M engine.


If what you say is correct then why are most cars that are designed for effortless cruising and acceleration Rolls Royce, Bentley, Mercedes, Aston Martin etc etc usually force fed ?

Cosworth427

Another unproductive post by WRX280. Go do another "180 MPH" run with a standard MR-2 Turbo.

Phil M

force fed with a 6.0 engine! bit different to a 2.0l

and they are twin turbo, one small turbo that spools up quick for low down torque and another big one for top end power. if they did a bi-turbo scoob i'd be impressed, but they don't

evo39

Then explain why the M3 takes nearly twice as long pulling from low revs in top gear from 60 - 80 when compared to the scoob spec C ?

Your post implies that you have bever driven an evo ? so why make the comment ? Or are all your comments percieved ideas only ?

juan

Sounds a bit poor for the evo. Mine would be pulling hard at 2.5K with bascially just lots of improved breathing (Hardly any increase in max BHP but 25% increase in torque over standard). I'm not saying there was no lag but it was pretty minor. Its hard to compare to a term such as 'it starts to take off quite rapidly' though. Does that mean by 2.5K its rapid, or 3K? or instantly at 2K?

Current car has a bit more lag but is still on song by around 3K. Even any N/A motor I've tried doesn't pull that hard at 2K

Cosworth427

It doesn't have to reach its "powerband", it simply uses the torque it makes at the RPM at the time. Which with an NA car, what you see is what you get.

A turbo car on the otherhand, it says you make 50 HP on the dyno, but in real life, you're making 20 HP and then you use whatever exhaust energy you have from 20 HP to drive the turbo.

But Rolls Royce, Bentley, Mercedes and Aston Martin use atleast 4 litres of displacement. That's the difference between them and Subaru Imprezas and Nissan Skylines.

The displacement offsets any loss in response and extra weight of the car. A 2 tonne Bentley has 6 litres, for every litre, it carries only 333 KG of weight. A Skyline weighs 1520+ KG. With an RB26DETT, for every litre, it has to carry a whopping 590 KG.

"Off boost" these luxury cars can still respond very well, although not as quickly as a tuned big displacment NA engine.

Cosworth427

In what gear though?

evo39

So what you are saying then is if a forced induction system is applied properly it will out perform the equivalant N/A engine in virtually every respect.

Phil M

The reason why the M3 does is because its overall gearing, this can be anything, final drive ratio, wheels size etc is different to the impreza.

If your comparing an M3 in top you should be 'thinking' that the spec c should be in '7th' to get the same ratio. or just look at the M3 times in 5th.

I have driven the evo, not a lot but pulling out of the drie way and onto the street is enough to tell the power characteristics of the car, driving it or not

Cosworth427

It's not that Phil. The overall gear ratios (gear x final drive) in 6th is very similar between the M3 and the Spec C/STi models.

If you go back to the acceleration times posted earlier, the test starts as low as 20 MPH, and it took 11+ seconds for the spec-c to move from 20 MPH to 40 MPH, so you can say it has atleast 11+ seconds to build up boost, JUST-IN-TIME for enough power to do 60-80 in 4.6 seconds.

Beef

Biturbo is usually only done on V engines, with one turbo per bank. A 300ZX is biturbo, with 3 cylinders driving 1 turbo which then feeds those 3 cylinders again (actually, I think the 300ZX has the outlets from each turbo feeding the *other* bank, but it makes no difference). The big blown Mercs are also biturbo.

Twin turbo is where both turbos feed into the same inlet, and both turbos 'share' the same exhaust gases. A Skyline is twin turbo.

What's you're talking about is twin sequential turbo setups, such as the Supra (which makes positive boost at 1000rpm, can make 10psi @ 2000rpm, and has more than enough torque to be easily driven between 1000 and 2000rpm all day - flexible enough for you?) or the RX7.

Sequential setups are virtually always made up of *identical* turbos, not different sized ones. I know of no factory production sequential setup using different sized turbos.

Phil M

No, You will get more power, but not the response of a n/a engine

And were not talking big mercs etc here were talking bout the scoob (or was it skyline) in a big merc or bently the lag is not noticeable because of the torque converter, you can't compare that.

ever been in an RS4? bi-turbo and manual. very powerful but it doesnt matter where you are in the rev range it WILL lag when you stomp the go pedal

WRX280

You took the bait...just as i intended

Looooooooooooser!

Cosworth427

Yeah...

Beef

Hang on, you're implying that if the Skyline was an auto, it would be as responsive if not more so than the M3!

Cosworth427

The torque converter applies torque gradually. Simply because the the nature of the fluid. This hides any perception of lag.

But more importantly, "big mercs" run with big engines, twice the size of an RB26DETT, plenty more torque when off boost.

evo39

Please let me know of a N/A that is going to produce better reponse and flexibilty than a engine force fed with around 550lb/ft at 1800 rpm. I cant think of one.

Fosters

this thread is the first time for a while that I've posted outside of comp. related/non scoob related.

Cossie427 - you really started on the wrong foot and only in the last few pages with the support of craigH, philm, etc did you calm down and debate.

I realised what you were getting at by the beginning of page 2, but you really didn't help yourself, esp. having a go at Simon DB, whom imho everyone on this board should stfu and listen to.

apart from the few outspoken supporters, i'm really disappointed with the rest of the scoobynet bunch. i thought we were bigger than that. I loved my scoob to bits for the 2 years i had it, but during that time i became accutely aware of how capable other cars were on the road.

i personally hate bmws after working there for 2.5 years, but going out in 3 or 4 (as passenger) and... ahem... 'having a go' with a couple, I know exactly where cossie427 is coming from. my uk ppp decat turbo took an age to get going when m3 drivers and me looked at each smiled and floored it.

cossie was an ar$e to start off with and deserved the flaming, but alot of you guys don't seem to know when to stop. "you took the bait, looooser!" - ffs, what is that?!

I've kept reading coz I've learnt a few techie things in this thread, but some of you are real idiots.

flame me all you like, but I think i've made a valid point - have some respect for others' opinions and knowledge.

Cosworth427

The Skyline and Impreza doesnt make 550 lb/ft at 1800 RPM.

Phil M

no, where u get that from!

a car with a torque converter (unless its programmed to imediatly lock up) will not be as responsive as a car with a manual, turbo or not

Phil M

throttle response! at any revs! forget the big numbers..

lets pretend these 2 cars were both manuals

SL500 5.0 v8 and impreza spec c (yeh its already a manual)

they will both produce ABOUT the same torque at same revs, the merc will have the best throttle response! end of story

Phil M

I think you've got a valid point if you think i'm outspoken or not... (look, no insult! its not necessary)

evo39

Now lets compare the same two 5.0 V8's one N/A and one force induced with around 500 lb/ft at 1800 rpm. Which one do you think will be more responsive ?

juan

In 2nd as this was what I was responding to: