compound charging/twin charging

[Testament]

Yeah straight lobe rootes blowers are notoriously inefficient at higher boost levels because they were designed as just that "blowers" for blowing, or sometimes scavenging. They have no internal compression so its the backing up of air between the cylinder and the blower that gives you boost. basiclally over .5 bar it starts to go out the window. but if your running methanol with a 6/71 on a huge v8 thats fine.

newer (read eaton mXX) blowers have twisted lobes and do a little compression internally (like a budget version of a screw blower) and are better to slightly higher boost levels.

all this efficiency aside they still give you a significant power boost, from the get go and give you that higher pressure inlet for scavenging efficiency (and fuel inefficiency ).

Also you are better to goto a bigger rootes supercharger for more boost than to just change the pulley.

At the end of the day they make a cool noise so who cares about all that efficiency stuff anyways

[RUNAMUCK]

Roots Blowers aren't all that noisy on their own. Most of the filthy whine that people asociate with blowers is the dirty gilmer drives that V8s tend to use.

The reason why (as already said) a true compound charging set up would be a fail is because the S/C14 is so limited.

I run one on my 1500cc datsun driven @1:1, producing 10psi of boost. Given that a built as fuck CA18DET is going to scream to easily 9000rpm, and that it will take more overdrive to reach say 14 (Or even the same 10 as I'm running)psi, the blower will be running so hard that it'll be doing more harm than good. Mine punches hard in the low and mid range, but loses some of it's sledgehammer like vigor when winding out in the upper rev ranges. Think too that given the lack of VE that an S/C14 runs, the overdrive required will not be a lineal increase.

The whole logic behind having both to me is the brutal antilag that could be harnessed. Dave could run a stupidly big turbo like a T88, and still have it spooling before the blower runs out of effeciency. Speaking from my personal experience, the toyota blowers taper off dramatically with rpms, not just higher boost levels.

If you're really that hung up on scavenging, just open up the LSA buy 1/2 a degree or so.

[d.p.n.s]

its dan bart not dave but if you happy with dave thats cool by me brother lol

i have been called lots worse

[H05TYL]

The reason why (as already said) a true compound charging set up would be a fail is because the S/C14 is so limited.

I run one on my 1500cc datsun driven @1:1, producing 10psi of boost. Given that a built as fuck CA18DET is going to scream to easily 9000rpm, and that it will take more overdrive to reach say 14 (Or even the same 10 as I'm running)psi, the blower will be running so hard that it'll be doing more harm than good. Mine punches hard in the low and mid range, but loses some of it's sledgehammer like vigor when winding out in the upper rev ranges. Think too that given the lack of VE that an S/C14 runs, the overdrive required will not be a lineal increase.

The whole logic behind having both to me is the brutal antilag that could be harnessed. Dave could run a stupidly big turbo like a T88, and still have it spooling before the blower runs out of effeciency. Speaking from my personal experience, the toyota blowers taper off dramatically with rpms, not just higher boost levels.

If you're really that hung up on scavenging, just open up the LSA buy 1/2 a degree or so.

The limited VE of the supercharger isn't a problem with a compound setup though. The volume of air that passes through it is the same as when the inlet is not pressurised, but the MASS of air that passes through it is increased because the turbo has already pressurised it.

Like Tom said a roots blower pretty much just takes whats on one side and pumps it to the other side.

You don't need to spin the f*ck out of the supercharger, gear it to make 7psi, it'll be happy, then get a medium sized turbo (3076R or similar) to pump 15psi into it to get an inlet manifold pressure of ~28psi whilst heating the air less than you would with the turbo on it's own making 28psi

[Yowzer]

Pretty keen to attempt this on my diesel wagon, just for some lols. Fucked if I care how well it actually works

[Honda Ass Dragger]

I alwasy thought compund charging was what the crazy tractor pulling guys from the states did with there desils to make insane amount of power, I was under the impression it works as per below

First turbo is set up normally, but instad of sending the compressed air into the intake, it is directed through another turbo, the exhuast gas of the first turbo also being sent throught he second turbo, this can be used to creat insane amount of boost pressure and airflow, there are even kits for sale to do this sort of comversion to your big yanky v8 see links below:

Couple of Linkys:

http://www.dsmtuners.com/forums/custom- ... et-up.html

http://dieselpowersource.com/index.php? ... duct_id=60

http://www.dieselpowermag.com/features/ ... tions.html

http://www.boostlogic.com/xcart/product ... t=9&page=1

[Yowzer]

Same concept, only with 2 turbos. Principle is still the same, but turbos have a more dynamic CR.

Ya could use as many turbos and supercharges you like, in theory. Engine will probably have a winge at you though

[eke_zetec_RWD]

so on my 2.0L zetec i have a sc12 running 4psi. it has a 165mm crank pully and a standard sc pully.

if i want 12psi boost total should i run about 4psi on a turbo into it?

i have a gt30 76 (chineese be it) turbo stacked away so this could be a option.

i want about 200kw atw, currently 140kw atw on 4psi

[Yowzer]

k

14.70 + 4 = 18.7PSI, / 14.7 = 1.272:1 CR

14.7 + 12 = 26.7, / 1.272 = 20.99, - 14.7 = 6.29PSI

So run 7PSI from turbo, into 4 from supercharger to get around 12PSI at engine (math doesn't take potential losses into account)

[eke_zetec_RWD]

just remembered that my link wouldnt be able to tune it very well lol. might just swap to turbo

[H05TYL]

For a given (inlet manifold) boost level a compound setup (where the turbo and supercharger are working at lower pressure ratio's (close to peak efficiency)) will heat the air less than either type of compressor on it's own, or both working in parallel. The higher the boost level the greater the difference.

Cooler charge temp = less prone to detonation.

Depending on the original compression ratio, and the fuel you plan to use (amongst other things) you may not need to lower the compression. That said often the gains from running more boost will cancel out the losses from dropping the cr a touch anyway.

If you can get it, run Gull Force 10. If it's just a fun car (not a daily), get some ethanol and mix up your own E30.

Pray that one day we'll get E85 at the pump over here - 30+psi on 9:1 cr quite happily.

[Yowzer]

Really, it comes down to what you are trying to achieve with your engine. If you're going for all out power, fuel efficiency / economy means jack shit.

If you want a reliable daily with a bit of kick, then what you are saying does make more sence.

However I still don't get what you are on about 'flow'.

Sure, a big turbo can flow more air through it, but it's still gonna be flowing the same amount as a smaller turbo / SC on the same engine at the same boost levels. The only difference is it's gonna take longer to spool up.

[Brock-Lee]

I read that wrong. Yes it will be moving the same amount of air, the difference comes in as to the rpm's required to flow that amount of air.

Big turbo/blower = lower rpm

Small turbo/blower = higher rpm

for X m^3/s

You want to keep errthing on its adiabatic eff. "island" and so if you can produce the same flow at a lower rpm it is heaps better and shit.

[Brock-Lee]

boost pressure in an engine is a measure of restriction. If you can make a head flow well, then a lower boost pressure is required to flow the same amount of air than a shitty flowing head. More air = more fuel = more go.

On a given engine (so head flow numbers are the same) a small turbo/ar. - t25g will have to be spinning faster than a large turbo/ar. - t88 to flow the same amount because the small turbo/ar. will flow less volume than the large turbo/ar.

flow Q = velocity*area

increase turbo size/area in above equation then the velocity required drops off for a given flow Q

[/worst structure in a post ever]

[bubblegoose]

hey dan, slap some bike carbs on it and be done

[d.p.n.s]

just out of curiosity has anyone done ether of these ways.

[d.p.n.s]

if i said i had a t70 turbo and sc14 supercharger and wanted to use them would that make you chose one way over another

[Simon]

I looked into it ages ago when I got my MR2,

Then thought about it again since then.

Asked about it on a couple of forums and talked to a few people - Dad's turbo technician and fuel injection specialists etc.

They said if you are trying to do it after market it's a waste of time and you will spend heaps of time and money trying to get it to work and it will never get finished / blow it up.

Steve (turbo tech) said it is pretty much only worth it for a gymkhana type car that has lots of on and off bursts at 100% throttle.

He reckons a properly built turbo system will be over 9000 times better for a car that is going to be on a normal track and lols at the thought of a road driven one compared to a nice turbo setup.

So with that knowledge I bought a higher displacement motor and will run slightly upped factory boost through and it will go for ever while making heaps of power.

[nismo.capri]

just out of curiosity has anyone done ether of these ways.

If I can get hold of Joe McClintoch who used to work at the engine centre I might be able to get you a ride in a RWD starlet running the same valve and the SC-12 not sure of the turbo.

[d.p.n.s]

I looked into it ages ago when I got my MR2,

Then thought about it again since then.

Asked about it on a couple of forums and talked to a few people - Dad's turbo technician and fuel injection specialists etc.

They said if you are trying to do it after market it's a waste of time and you will spend heaps of time and money trying to get it to work and it will never get finished / blow it up.

Steve (turbo tech) said it is pretty much only worth it for a gymkhana type car that has lots of on and off bursts at 100% throttle.

He reckons a properly built turbo system will be over 9000 times better for a car that is going to be on a normal track and lols at the thought of a road driven one compared to a nice turbo setup.

So with that knowledge I bought a higher displacement motor and will run slightly upped factory boost through and it will go for ever while making heaps of power.

thanks mate a appreciate that.

but i still want to give it ago and i have pretty much all i need to

put it together .

and like i've said before if it doesn't work i really don't have a problem

changing it for a different setup.i just like to try things for myself.

and saying that there's nothing stopping me trying both ways out.