Raising the compression?

[AJ4]

in a nutshell... the theory is big power needs a big turbo which means lots of lag and I hate lag.

You spend 95% of your time driving at less then 5000 rpm where there is no power. The charger gives constant boost pretty much from idle, so you have full boost from say 2500 to 7000 rpm instead of it peaking up high in the rev range. So even driving round town at 3000 rpm, you could be at full boost with instant throttle response

The downside is that your peak power is lower than a turbo, as the charger takes power to drive it ( about 60 bhp at full whack ). But you more than make that up with all the low down torque. Some people think the difference isn't even that great, as having a dity big turbo in the exhaust path causes a major restriction to airflow which probably wastes nearly as much power as running a charger would... Fortunately, God was kind enough to bestow me with a huuuge penis, so I don't really care what the pub bhp figure is anyway My target is 300bhp with 600 ft/lb of torque. The charger is capable of it, it remains to be seen if the engine is :lol:

For hill climbs, short sprints and 'urban rally ', a supercharger will usually beat a turbocharger because of zero lag and instant throttle response. Big turbos are only really suited to sprint events with long straights and drag events, for everything 'short' the charger is usually better. A charger will usually perform better on a handling course event, if you fluff a gear change with a turbo you've lost all your boost and momentum, but the charger is there all the time.

Think 'driving from one side of my town to the other through all the council estates and mini roundabouts as fast as possible', thats supercharger territory

There is also a bypass valve fitted to the supercharger, so that at very low loads ( like motorway cruising ), air is bypassed around the charger and it doesn't 'drag' on the engine. It uses less than one bhp typically when doing this. Then as soon as you plant your foot on the accelerator, the bypass snaps shut and you go straight to full boost...

And the end of the day its down to personal preference. I dont like turbo cars, I'd much rather have a car that has a very broad power range that is usuable in daily driving, than a peak power that I would only reach once in a blue moon.

 

[paz]

That was very interesting - thanks for that 300bhp and 600 ft/lb of torque is pretty much unheard of isn't it, I didn't think even WRC cars had that much torque - but more than likely I could be wrong :lol:

With a charger, is it possible to 'turn up the boost' so to speak in the same way as you can with a tubby, or is it a pre-built and limited design that can only be run at what it can be run at? I have even less knowledge of charged cars that I do of tubbies!

On a slightly different note, I saw a video the other day of a supercharged clio - it made a hell of a wailing noise, and when lifting off or changing gear made a high pitched squeak. I'm guessing thats the belt - but why does it do that?

You've got my interest now - prepare to be inundated with questions :lol:

Paz

 

[Dooie Pop Pop]

600lbft!!???

i can hear your con-rods/gearbox quivering in fear from here mate! lol

top marks for ingenuity, maybe this will become a common mod in time as i cant fault your reasoning:eyebrows:

my turbo' s not really laggy at all but you cant argue with zero lag!:lol: :-D i do agree about the what you said about the sprint stuff tbh if i tried to race a real twisty twisty course i think the savage way the boost comes in would work against me:doh:

lucky i spend most of my time on A/B roads really :twisted:

how much fabrication work is involved?

 

[AJ4]

questions questions... lol

IIRC correctly the WRC rally cars were around 450 ft/lb with 300 bhp as they were fitted with 34mm restrictors on the turbo inlet. So in reality without the restrictors they were probably 500 bhp ish.

The boost is set mechanically by the pulley size. Superchargers are rated in 'litres per revolution'. For example, mine is 2.3 litres meaning for every revolution of the charger shaft it produces 2.3 litres of air.

A 2 litre engine takes in 1 litre of air every revolution, so if I ran the supercharger at the same speed as the engine, I would be cramming in 2.3 litres per revolution when the engine only wants 1 litre, so the boost would be just over 1 bar. If I want more boost I just put a smaller pulley on which makes the charger run faster. If I made the supercharger run at twice the engine speed, it would be trying to pump in 4.6 litres when the engine only needs 1 litre, which is a boost of about 3 bar

My supercharger is rated at 16000 rpm, so if I wanted a redline of 7200 rpm on the engine, I could run the charger at 2.2 times speed maximum. That would result in a boost of 4bar :lol:

In reality, there are all sorts of losses such as belt slippage ( about 10% ), and the supercharger would probably blow apart at 4 bar I forgot to say though, that the supercharger is a lot more efficient than a turbo as well. I very very good roller bearing turbo is about 70% efficient, a good charger is 98%... Also, with a turbo you are blowing the intake air through a lump of metal that is around 700 degrees centigrade, which warms the inlet charge. The supercharger output temp is very low as there is no hot exhaust involved, only the rise in temp from the air being compressed.

Its not something I've really looked into, but I think you can buy controller kits that electronically control the boost. Its something like a wastegate, but on the inlet side that bypasses air around the charger at certain levels to hold a steady preset boost. Sounds like crap to me, but apparently its possible...

I've already got this kind of thing on my charger, but its to help efficiency, not control boost. As soon as I lift off the wastegate opens and bypasses the charger so I don't have a build up of air in the inlet manifold ( a bit like a dump valve ). It also means that the charger isn't dragging on the engine when its not needed. I shouldn't get the high pitched screech of the belt slipping when I lift off then, because the charger will just be idling, not hitting a brick wall by trying to slam 2 bar of boost into a closed throttle

The wailing noise is what you used to get on old superchargers, with badly designed gears.

I know I'm talking it up and lot and making it sound better than what it actually is, but all the time that turbos have been developed, charger technology has been improving as well. With modern materials and machining its now possible to make extremely efficient chargers and they have got to the point where its a viable alternative to a turbo.

After all, a turbo is just an exhaust driven supercharger, and mine is just a belt driven supercharger. The advantage of belt driven is a lot lower intake temps and no lag, but lower 'peak' boost and a bit more power needed to drive it than a turbo.

On the fabrication side, I need a mounting plate that bolts to the engine to hold the charger in place, and of course I can now design a proper exhaust with the correct length runners to maximise or 'pulse tune' the engine ( something you can't do on a turbo, so its another gain for the charger :lol: ). Apart from that its just routing intake and outlet pipes around.

One last thing - the charger doesn't need a water supply and has an internal oil resevoir that only needs changed every 100,000 miles, so no worries about blowing the turbo and having the dreaded trail of black smoke out the back :lol:

 

[Dooie Pop Pop]

if you listen you can just hear lots of braincells getting a battering all over the board now lol

yeah im jealous..

i used to like that whining noise too like on the vipers. it sounds pretty good imo lol

next big question is...........how much? just curious, you can pm me if your feeling a bit squirrel like;-)

 

[paz]

Coolio cheers for the extended answer - much appreciated

Pretty much answers all my questions tbh, I'd just love to see it installed and be able to compare the performance side by side with a similar spec turbo'd car. It really will be a first in the 'R world

paz

 

[CruiseGTi-R]

only have to look at cars that use superchargers to see they're a good alternative to turbos. Usually used on 'limo' type cars where smoothness and instant punch low down are preferred to slightly peakier and later power.

Jag xkr's
Any Merc 'Kompressor' for e.g.

I always thought superchargers were normally used on engines which were effectively just N/A engines with appropriate compr ratio's. They're then powerful enough to drive the supercharger from the off at very low revs. You playing with the comp ratio on yours, (you've a stroker don't you?).

You can't usually 'map' or really control boost like you can on a turbo throughout the rev range. I guess you'll just let the supercharger force whatever air in it can and fuel/time accordingly?

How do you avoid the power being too immediate from pulling away, or I guess with a SR20DET engine having a very weak engine low down due to losing 60bhp at the off?

Very interesting Ross, good on ya, should be awesome.

Going for a little missile button on the gearstick Mad Max style?

Username should be changed you know. Ross Max perhaps, eerm, AJcharger4. GTiSR, Whipple4, Ross Gibson, could go on...

 

[Dooie Pop Pop]

How do you avoid the power being too immediate from pulling away, .

with your right foot.........:lol:

i vote MadRoss

 

[stumo]

I guess with a SR20DET engine having a very weak engine low down due to losing 60bhp at the off?

You'll only loose that amount at full revs

 

[jpward]

Very interesting read well it's used a lot in the states and not forgeting the micra superturbo!!!

but id say the mounting is going to be a complete pain in the ****.


Do you need a charge cooler with a blower? :?

 

[Fast Guy]

Yes. (well intercooler or chargecooler) but you could probably get away with one if you only planned to run low boost, like on some low pressure turbo applications.

 

[Fast Guy]

Do you want one of these to go with it Ross?

http://www.drcreview.com/absolutenm/templates/headlines.asp?articleid=3&zoneid=2

 

[cojack]

Top mark's fella great idea. I will be keeping an eye on this project as this thought crossed my mine at work a couple of month's ago, but soon fissled out lol.

A f plated mk1 toyota mr2 supercharger import of course came in to work to have a cuscus crank pulley and a smaller idler fitted. The crank pulley is larger than the standard one so this results in more boost from the charger. Set the timing up colder plugs and she was ready for road test.

Before i fitted this mode this car was pretty rapid for a 1600cc with a blower. But i have to say with this new pulley set up i reckon it would give the standard R a run for it's money.

Best of luck fella

 

[jpward]

Do you want one of these to go with it Ross?

http://www.drcreview.com/absolutenm/templates/headlines.asp?articleid=3&zoneid=2

Nice work glad to see the turbo revoltion has some competition and ive always hoped that one day chargers would become as widly used as turbo's and that little blower is the daddies ;-)

Though kinda looks like the inside of a fuze and could go wrong easily :?

 

[AJ4]

lol, if your talking about mine its very robust, there are no touching parts to go wrong. The same model I've got is also used on 1800 bhp dragsters so it should be ok

 

[setb]

do you have pixs fitted?
is this easy to fit?

 

[Fusion Ed]

Cool project. Superchargers are great. As some here know, nissan kindly fitted one to my car as standard. Boost bypass control is perfectly possible - Nissan used a mechanical system on my car.

It sounds like you already has some kind of boost control, which is good as it will be needed. On many superchargers it does work exactly like a wastegate with actuator. Others use what is basically another throttle body to bypass the supercharger when not needed.

 

[AJ4]

What supercharger do you have / how is it installed ? You said Nissan fitted it ? got any pics ?

I have electronic boost control but I'm choosing not to use it. Instead I'm using the wastegate to dump boost at closed throttle ( similar to a dump valve ) to take the load off the charger and bypass it at cruise and idle.

My boost is set by my pulley choice and valve timing, so I don't need to control it. Its a positive displacement charger so the boost level is a constant.

 

[jpward]

lol, if your talking about mine its very robust, there are no touching parts to go wrong. The same model I've got is also used on 1800 bhp dragsters so it should be ok

no no aj your type i know is very reliable it was the link to the new one that centrifugal system good in theory but interesting to the the long term test results ;-)

 

[AJ4]

lol, no worries. I did think about using the pulley from the aircon pump, as its electro-mechanical and can be switched on and off for low boost / high boost. And then I thought, what the **** would I want low boost for ?