dual charged 3800

[the-dude1]

anyways if you guys do some research you will see that it has been done to the 3800 before. the technology of a dual charged system has been around much longer than the fiero.. so :la: ... im not going to do cause the lack off support..

[Mach10]

Twin charging has been around for a long time. But then again, so have points distributors and carburetors.

Doesn't mean that it's the best way to go.

VW has done some really, REALLY neat things with twin-charging and direct-injection. But that setup is enormously complicated;

The theory works like a split intake manifold, with the turbocharger feeding the "high-range" intake runners, and the SC feeding the low-range. There's a valve system as well as a pulley/clutch setup for the SC.

The SC creates boost at low RPM, and maintains that level until the turbo spools up. Then the two cross-over(keeping boost constant), and once the Turbo is shouldering the load, the SC uncouples, and a flapper valve slams shut to prevent boost from creeping back out the SC.

The idea here isn't to create massive amounts of power (which it does, actually), but to keep engine displacement low while maintaining high output AND creating a flat power curve. It does this for emissions and economy reasons.

When going balls out, it's MUCH more efficient to run one or two large turbos than to attempt twin-charging. Efficiency in the compressor (either SC or TC) == more power + safer operation.

Superchargers are--in general--not as efficient as a well-designed turbo. They are tricky to intercool, and they create more drag on the motor.

turbos aren't "free" power, but they rely more on waste heat to generate boost, rather than raw mechanical energy.

[The Dark Side of Will]

Boost from twin charging != boost from turbo alone.

Turbo: 75% adiabatic efficiency

Supercharger: 60% adiabatic efficiency

Twin charging: 0.75*0.6 = 45% adiabatic efficiency.

If you run your engine to 20 psi twin charged, your intercooling needs are going to be MUCH greater than if you ran the turbo by itself to 20 psi because the efficiency of the twin charged arrangement is going to be much lower.

[Boscolingus]

Its all nothing new, we built a dual charged at West Coast Fiero years ago - do a search over aa P-F-F-Lamers . nl under Johy Tinay's car or also knowns as sspeedy

[lucky]

Please listen before you speak.

Why would a twin charged engine run lean?

i was listening, and you obviously didn't finish reading my post about extensive fuel delivery upgrades being needed to make it not go boom.

[The Dark Side of Will]

Fueling is so basic to engine performance that I was really wondering why you thought for one second that someone building a stout twin charged 3800 *wouldn't* upgrade injectors...

[the-dude1]

hey guys a quick ? is the 3800 turbo from the grand national the same bolt pattern as the newer series 3800's??? if so has anybody done the swap.

hey aaron dont be so sensitive :ky: loosen up a bit.....

[The Dark Side of Will]

No. The 3.8 and 3800 are almost different engines. Very little interchanges. 20 years of development does that...

[the-dude1]

yea thats what i thought, my father in law brought it up to me cause he found one compete with 30xxx miles for only 600$$

[nocutt]

Darn guys take it to another thread it is not about Aaron...jeez!!

Most of the information for twincharging here is very incorrect...in any event since you have made your mind to go turbo I will just briefly enumerate...using a turbo with a roots actually increases the efficiency of the supercharger. Of course you will have to be blowing into the SC, in any event a roots is inefficient because it "leaks" regurgitating a lot of air supposedly going into the engine. When pressure (from the turbo) is forced into the SC it acts like a seal...thereby increasing its efficiency. Although the SC still moves air at the same volume it is at a higher density!! The crux is the amount of boost one will need to run...WCF designed this yrs ago based on this ideas; talk about power ALL thru the RPM range.

[The Dark Side of Will]

Did some housecleaning.

[The Dark Side of Will]

Darn guys take it to another thread it is not about Aaron...jeez!!

Most of the information for twincharging here is very incorrect...in any event since you have made your mind to go turbo I will just briefly enumerate...using a turbo with a roots actually increases the efficiency of the supercharger. Of course you will have to be blowing into the SC, in any event a roots is inefficient because it "leaks" regurgitating a lot of air supposedly going into the engine. When pressure (from the turbo) is forced into the SC it acts like a seal...thereby increasing its efficiency. Although the SC still moves air at the same volume it is at a higher density!! The crux is the amount of boost one will need to run...WCF designed this yrs ago based on this ideas; talk about power ALL thru the RPM range.

The SC is mechanically driven off the crankshaft. This means that it always tries to overfeed the engine by the same amount. It doesn't matter if it's being fed by air that's 14.7 psia or 34.7 psia. It will try to increase the pressure of that air by the amount the S/C's volume flow rate exceeds the engine's volume flow rate. You don't make any leakage problems go away by pressurizing the blower inlet because the blower outlet will always be at a higher pressure. This is why twin charging is less efficient than a turbo by itself. No matter how well intercooled the higher density air is, the blower will still add plenty of its own heat and the engine can only take so much boost. 25 psi twin charged will have HUGE intercooling needs compared to 25 psi from a highly efficient turbocharger.

However, I can see that if a twin charged engine is running an anemic amount of boost like 12 psi, then it might seem like it performs pretty well because it's probably not at the limits of the engine. But at that boost level, all a twin charging system does is waste space and weight, since that boost level and power could be achieved more easily with a blower upgrade.

So does twin charging work? Yes. Does it work well? Not really.

[The Dark Side of Will]

So does twin charging work? Yes. Does it work well? Not really.

BTW, this doesn't apply to the VW setup, which according to Mach declutches the SC when the turbo spools up. It doesn't apply because the VW setup isn't using the turbo and SC at the same time.

[Mach10]

I understand that there's a bit of crossover--where both units are working, but the systems are in parallel, not in series (like std. twincharging).

I don't know if that would increase efficiency or not; seems to me it wouldn't.

[The Dark Side of Will]

It's not that reducing overlap increases efficiency... it just doesn't reduce it as much as a fully overlapped system.

[Mach10]

Yep, clutched and bypassed... But NOT in parallel.


http://www.greencarcongress.com/2005/08 ... _new_.html

[lucky]

Fueling is so basic to engine performance that I was really wondering why you thought for one second that someone building a stout twin charged 3800 *wouldn't* upgrade injectors...

i wanna apologize, i'm so used to dealing with idiots at work that would try to do something like install a turbo in front of a sc and just expect it to work. I've seen the caliber of the work you guys are turning out through the pics you post and for me to assume that anyone here would be that ignorant was just ignorant on my part.

[Mach10]

lol...

Even the most finely tuned bullshit detector will flash off false-positives due to the vast amount of background BS radiation. Especially on teh intarwebs.

[nocutt]

...The SC is mechanically driven off the crankshaft. This means that it always tries to overfeed the engine by the same amount. It doesn't matter if it's being fed by air that's 14.7 psia or 34.7 psia. It will try to increase the pressure of that air by the amount the S/C's volume flow rate exceeds the engine's volume flow rate. You don't make any leakage problems go away by pressurizing the blower inlet because the blower outlet will always be at a higher pressure. This is why twin charging is less efficient than a turbo by itself. No matter how well intercooled the higher density air is, the blower will still add plenty of its own heat and the engine can only take so much boost. 25 psi twin charged will have HUGE intercooling needs compared to 25 psi from a highly efficient turbocharger.

Will based on thermodynamics it matters. Using a flight of staircase as a rudimentary analogy...two ppl, one of each standing at the middle and bottom of the staircase have different potential energy; the bottom been the least equates to a motor starting from atmospheric pressure. The man at the middle is halfway and equates to an engine starting with pressure (higher density) who will make it to the top first? The variable we are concerned with here is air!! now lets look at the temperature...first why is a roots so inefficient? by virtue of their design! Since the roots is nothing but a pump, it only moves air and this air is pressurized in the inlet (after the blower). We understand the process of compression creates heat however this pump also allows air...heated air by the way to "leak pass" the vanes of the blower thereby heating additional air behind the blower...
Now with pressurized air been pumped by the turbocharger into the blower, the blower cannot "regurgitate" heated air thereby the turbo also "seals" this imperfection.
Another quality is a depression is also created infront of the turbo by virtue of the sc...which happens to "jumpstart" the compressor. In other words, there is a synergistic quality to this setup done right...
We both agree going more than 2 bars imho is definitely an intercooling nightmare...at least in the fiero!

It is a very worthy and streetable setup done right...I cannot describe the feeling of such a setup...Boscolingus will and can testify...a v6 fiero not chirp tires but burn them thru the first 3 gears...plenty potential :salute:

[Series8217]

Proportionately, the pressure difference accross the blower remains the same regardless of how much boost you're feeding into it... so its still going to "leak" just as much (well, maybe even worse since the absolute pressure difference is greater)..