LG John

Ok, a thought just jumped into my head. Lets say I supercharge my S2000 for example:

Lets also say I was holding 7500rpm for a few moments waiting to take an oppertunity to pass something. To maintain those revs in say 3rd gear I'd not need much throttle or engine load. However, my understanding of s/c is that they are linked via pulleys to the engine and thus the boost they create is rpm related and fixed. On an S2000 a s/c would be making a good whack of boost (for an aftermarket s/c) at that engine speed. However, the engine is hardly under load and only on a small throttle opening to maintain those revs/that speed. So where the **** does all the air go?? Does is just back up in the throttle body? On a turbo car you're boost would probably drop off holding high revs under low throttle engine load and small throttle opening as the air the engine is consuming is much less than it would be passing 7500rpm marke on WOT so there is less air to spin the turbine. However, with a s/c 7500rpm is 7500rpm is 7500rpm irrespective of engine load or air consumption. So what does a s/c do? It must be like running anti-lag all the time - which can't be healthy?

davegtt

Im using hazy memory here... BUT.... If you foots not too the floor the intake isnt producing "flow" thats the key, pressure is pressure... but it all depends on flow. if the intake is partly closed (because your only putting your foot slightly down) the supercharger is going to produce boost but only gently. think of air/fuel ratio. as you put your foot down, more fuel is put in. to balence this out the more you put your foot down the more the throttle opens up to let more air in. If only partly got your foot down less fuel will be put in and the throttle will only open slightly producing a little air to balence it out again....

Does that make any sense to you?

midget1500

IIRC s/c's have an internal clutch which engages/disengages so it is only used when required

Brendan Hughes

<Must resist... must resist...>

It gets siphoned to one side of your fuel tank.

<...****>

Pumpkin

not all superchargers have clutches...

They are geared to spin at a ratio of the crankshaft speed

vindaloo

You always spin the supercharger which pumps the air that's fed into it.

Some systems have a diverter valve which bypasses the s/c on light throttle applications (Eaton, I think). The charger still spins but it's operating in more of a vacuum, so the losses from compressing the air are less. When you hit the throttle, the valve closes and the s/c pumps more air.

You can control maximum boost with a BOV.

Some systems have 'slippy' bearings that limit the load and maximum speed of the charger. I think Rotrex do this in the interest of reliability.


J.

Dark Blue Mark

SB- just noticed this thread. You know ive bought a Vortech S/C for mine?? Going to be a bit tasty let me know if you need any info. 300 rwhp will be great.

MB

LG John

Yeah I knew Still not sure I understand where the boost goes at high revs/low load though

Dark Blue Mark

Its all about the butterfly valve / throttle - think of it as a gate. S/C just gets backed up at high rpm low load, but its speed will be at its upper end. Not sure if some will be bled by the BOV.

Its fine to dead head a centrif charger for a short period, and even on low throttle there is enough throttle opening to dissipate any heat. Got to look into this a bit more, as there is a BOV involved, same as a turbo system.

PS - its a compressor wheel rather than a turbine in this instance

MB

LG John

That being the case you would have boost backed up in the inlet system such that as soon as the throttle butterfly is opened the pressurised air is right there. With no lag it must be an instant hit of hard acceleration?? That would be pretty neat

Ralph Wiggum

would of thought a s/c would not be suited to a vtec engine specially the s2000, due to the rotating mass at those sort of rpms, would take a big big s/c to flow the amount of air you'd need to supply power and torque to those rpms or perhaps reprofile the cams, that said you have a dilemma with a turbo as you'd need a largish turbo and have lag, but if vtec don't start till 5800rpm anyway proberly not a problem

Ralph Wiggum

you got the old s/c versus turbo argument goin there though,

s/c no lag but saps power to make power, but is instant .
turbo has lag but works off waste gases to make power and is easier to get BIG bhp,

put it this way big bhp blown cars have a gigantic blower, whereas a BIG turbo will not big comparitable in size to the equivilant s/c, less to go wrong on a turbo

MooseRacer

S/C is much more suited to high compression VTEC engines.

Dark Blue Mark

Ralph, it seems you none too clued up on these things - no offence

Vortech and Comptech have been producing centrif blowers for S2000's for a few years now, and other VTEC cars. Because a charger works in in linear fashion, with revs, they are ideal. Loads and loads of the US guys are using them with great effect.

Less to go wrong with a turbo? I think not. A supercharger is merely a belt driven air compressor into the air intake. Turbo's are a nighmare to retrofit, and more parts. Intercooler, wastegate, new exuast to fit the turbo etc etc, and you nearly always will need an aftermarket ECU.

And it is quite big too :

http://videos.streetfire.net/Player....C48F6&kw=3&p=2





MB

Tobisausage

f'me

Dark Blue Mark

Oh yes

MB

MooseRacer

Your s2k is going to be naughty MB

cts5555

Nope.

Dark Blue Mark

Cheers Moose.

CTS - trust me, they work very well indeed.

MB

MooseRacer

Oooooh yes they are

Ralph Wiggum

but at high compression you won't be running much boost and youll still need a intercooler, more so on high compression.

look in j tuner last month, turbo s2k in that, not s/c. If s/c were so good subaru nissan et all would all produce s/c performance cars, when in fact most s/c cars have high capacity engines, e.g mercs and jags etc.as they do not require much boost.

s/c applications on small capacity engines are never gonna produce outright bhp that a turbo can deliver yes it will make the car better and faster and sure s/c itr and ctrs are good but the turbos are better

Dark Blue Mark

Eh?

And Mercedes use them because???

If you want ultimate power then yes, a turbo is clearly the way to go - thats not in question. To retrofit, a turbo is major work and I would question the statement they are "better" Subaru and Mitsubishi didnt use them because thats not suited to a rally type application. For info there is a S/C and turbo scoob nocking around

To turbo an S2000 can cost near to 5 figures if you look at people that have done it. My SC cost a fraction of that, and it retains the VTEC characteristics of the car. A turbo will mask this due to its all or nothing power delivery, and spoil the car IMO.

On an S - they really work very very well! To have a shade over 300 bhp at the rear wheels will see it keep up with and beat most stuff.

MB

Baggers

10 points - correct, works exactly the same as a turbo wastegate, actuated by manifold pressure. These don't have to be fitted but it's recommended. Also, the throttle butterfly can be placed upstream of the charger and this controls the amount of air getting into the unit and being compressed this is common on older setups such as classic cars where the carb was bolted onto the charger inlet.

Dark Blue Mark

All types ive seen on the S2k are on the inlet side of the TB.

MB

Baggers

Likely the Vortex units have a bypass valve then....just out of curiosity Mark do the s2k's need the ECU tweeked and what sort of pressure can they run safely on stock internals? 10psi ish?

Dark Blue Mark

At 7 psi (standard Vortech pulley) I think the standard 340's are at quite a high duty cycle. Some change to 440's and take advanteage of the upgrade 255 pump that comes with the kit. Some run up to 11 psi with different pulleys I believe, then internals are very strong. Gearbox and clutch are the weak links at that power though!

The ECU does need tweaking, but both the Comptech and Vortech come with a fuel management unit, which you wire into the ECU. This compensates the fuelling for the S/C. As its designed for stock application it works quite well. If you mod it then aftermarket ECU is really the best option.

MB

cts5555

Ive built 3 turbo hondas, b16 1.6, most powerful is 380+bhp, standard engine ones make 260bhp.

Power figures dont tell the whole story anyway, the vortech is a nice complete kit, but you dont get max boost until max rpm, the figures they quote are so high because of the large compressor, but that power is only made at max rpm, take a look at the power figures from 4-6krpm and compare them to a decent turbo setup.

cts5555

FMUs arent worth ****, they will be the reason your turbo honda dont work. standard injectors are almost maxed out on a standard engine, the fmu raises fuel pressure per lb of boost, normally on a 12:1 ratio for hondas. U cannot run boost on a honda succesfully without proper engine management, how do you think the ignition timing is taken care of with these kits??? lol

As for running more boost with the vortech - its not quite as simple as changing the pulleys, u cant go much over 7 psi on a standard engine even with proper EMS, and when u get to 11+ you will have belt slip problems, most people change to a chain driven setup, overall a nice kit, but everyone who has one wishes they went turbo.

And a turbo is easily retrofitted to a honda, weekends work including mapping, and thats in my garage at my house with no ramps.

cts5555

BTW standard 1600 ( b16 ) gearbox's have been seen to withstand 550bhp on drag tyres, so this isnt a problem on street cars, the boxes and crank are the strongest part of these setups ( not sure bout the s2k though )

LG John

Have you been round them all door to door asking that?