G Goodman

OK I used the search function and didn't find anything specific. My questions is this, has anyone ever taken out the turbos on a FD and gone to a supercharger instead? It seems this set up would have several advantages if a centrifugal type supercharger was used. Less heat, controllable boost, and no lag to name a few. I'm about to go to Iraq for a year and when I get back it's gonna be time to mod the car. I am just looking for options and this seemed to be one. So if anyone has any info it would be appreciated.

911GT2

It's been done a a 2nd gen. No reason it couldn't be done on a 3rd gen too http://www.camdensuperchargers.com/index.php?pag=6

Go for it

FormerPorscheGuy

Why would you want to replace two things that spin at several thousand RPM's (your turbos) with one thing (a supercharger) that spins at the speed of your eccentric shaft?

Your wrong on several points.

1) Rotary engines produce heat so the savings there would be negligible and not noticeable compared to the power loss and the pain of building a completely new system for this car. Heat on turbos can be easily controlled.

2) Boost can be easily controlled on turbos with a boost controller.

3) The positioning of the stock twins directly next to the exhaust ports minimizes lag. I don't notice any when I drive.

A turbo set up is superior to a supercharger by offering more controllable power with better efficiency and economy. And there is the argument that if it was ment to have a supercharger, why didn't they design it with one instead of a turbo? Why mess up a good thing?

blueskaterboy

what he said ^

RonKMiller

Been done to a 13b as well. Never really accepted as being better..

I think it was Atkins that supplied a kit?

The more I look at twin sequentials the more I admire them - they address a multitude of sins - except for the freakin' solenoids, vacuum hoses, ad nauseum. Blah.

G Goodman

The reason I am considering supercharging as an option is exactly what is mentioned above. It would get rid of the rat's nest and all the complication of the turbo control system. The heat in the engine bay would be significantly reduced in that the exahust would leave immediately rather that being trapped in the turbo system. Many of the mods done to these cars are targeted directly at cooling the engine bay, vented hoods, bigger radiators, etc. Boost would be directly tied to engine speed and not the wastegate and turbo control system, thus no boost spikes. Yes the stock twin system has minimal lag, when it works correctly, which if you read the posts often is a HUGE problem for most FD owners. I have seen several threads about supercharging FC's and just wondered about doing the same to and FD. In my mind it seems to be a viable alternative and I just wondered if there was any info out there. The new centrifugal type superchargers look like like a perfect way to set this up, so I am just looking for anyone else who may of researched this.
Thanks

89Turbo944

What a waste of money if you ask me. The money you could put into that system could be used to make the turbo system even better. But it can be done if you can afford it

chris406

imo, i would rather have a single turbo upgrade, turbos will always be the most effecient power adder. However Centrifugal Superchargers have come a long way, several Pro 5.0 racers like Don Walsh Jr are in the 6.60's with small block fords and monster ProChargers, his is reverse driven by a double row chain!!!! Centrifugal superchargers do however put a alot of stress on the front bearing and crank snout on piston engines, i've seen many break the snout right off of a crank at only 20psi. Imagine what that would do the the eccentric shaft.

Also centrifugal superchargers spin anywhere from 15,000 to 40,000 rpm depending on the charger and boost setting. They have gears on the inside that step up the revs just like the rear gears in a differential do.

Just get a turbo it's better. And probably the same cost.

Trexthe3rd

That is absolutly incorrect. First of all, it would be well over 100 thousand rpms (not several thousand). By the time you get to the compression stage of the SC, it is turning at an extremely high rate (much, much higher than the engine rpm)

Again incorrect, due to the fact that the turbo is utilizing the exhaust energy it must bear the 1200+ deg from the gas and that heat is present throughout the turbo (the turbos will be glowing red after hard runs). Oil and coolant is used to keep the temp at bay, but the intake still requires intercoolers to remove additional heat caused by the turbo. Keeping the turbo temperature down has always been an engineering challenge. Unless you have invented something the PHDs in Garret don't know about.

Do a search on boost spike and boost creep then try again

Please goto the site calld howstuffworks and read up on turbo functions before making an argument. Turbo lag comes from the time required to build up the necessary exhaust energy to spool up the turbine and is directly related to the size of the turbine (hence larger turbos have bigger lag).

TC and SC both have their advantages and drawbacks. That is why they are both used in various applications. TC is more efficient in producing high end power and does not have any parasitic loss but lacks lowend umph because of lag. SC provides instantaneous boost but runs out in the high end and causes parasitic power loss due to the mechanical connection.

89Turbo944

Someone invent an electricly powered supercharger. Do draw on the motor to run it, and you get the low end. Best of both worlds.

chris406

[QUOTE]Originally posted by Trexthe3rd
[B]That is absolutly incorrect. First of all, it would be well over 100 thousand rpms (not several thousand). By the time you get to the compression stage of the SC, it is turning at an extremely high rate (much, much higher than the engine rpm)

http://www.procharger.com/models.shtml

This is a list of all the ATI procharger models. Max impeller speed is given for each model, Indeed much higher than I expected but defineately not well over 100,000 rpm.

89Turbo944

Ya 100,000rpm is juat a LITTLE high. The sound would no longer be a mine of the supercharger, it would be a grinding of the intire engine. The dam supercharger would eat the engine for lunch spining that fast.

FormerPorscheGuy

The point I was making was that superchargers spin at much lower speeds then turbo chargers, and I think I made it. Superchargers are connected directly to the crank shaft RPM's through a belt drive and thus limited in speed.

If this was incorrect then why do NA rotaries still have cooling issues? If you don't believe me then do a search in the FC section.

Boost creep is caused by not having a big enough wastegates. Boost spikes, as the man stated above, can be controlled by a boost controller. They are similar but separate issues. Do a search and you will see.

If your car is not running properly and you are experiencing turbo lag then maybe that has a direct correlation to your inability as a mechanic or your chosen set up for your car. The stock set up for the sequential twins makes minimal turbo lag, that is why it was chosen by Mazda.

Thank you for backing up my above argument that turbo chargers are more efficient and produce superior power over super chargers.

If you would like a further explanation on how your car works please feel free to let me know. I will be more then happy to help and teach you all about turbochargers and rotaries.

Cheers

Brian7

Wow, talk about a Barney..

KevinK2

rough max speeds:

- turbo is about 120,000 rpm or so
- twin screw SC (eaton) is about 12,000 rpm
- centrifical SC (vortec) is about 60,000 rpm

the centrifical has some lag to it, and takes about 1/3 the engine rpm range to hit high boost.

Toadman

Supercharging is overall inefficient for a car that regularly redlines at 7500-9000rpm. Can it be done to the rotary? Sure, but it's not making the best use of the engine characteristics.

Trexthe3rd

Why is it that people always try to cover their mistakes by saying "well, what I was trying to say is..."? While the speed of the compression device is relavent, it is not the only determining factor in the efficiency and overall power output. If I have 2 fans side by side, 1 is spinning at 10,000 rpm while the other is spinning at 5000 rpm, can you definitively say the 1st fan is moving more air? What if the second fan is 5 times the size of the 1st, what then?
In case you havn't noticed, The original post was talking about heat related to the turbos, no the engine. they are two seperate issues. Can they effect each other, yes. On that note, I have seen NAs run well pass quarter of a million miles without any problems, tell me 1 FD that has done that without a rebuild. On the average, NAs have less cooling problems than turbo charged.
What is your point? My argument is based on you statement of "boost can be easily controlled". With the stock twins, can you easily take out the wastegate and replaceit with a larger one? If you can install a boost controller and enlarge the waste gate in less then 30 min then you can tell me it can be easily controlled.
Again, what is you point? Your statement was "The positioning of the stock twins directly next to the exhaust ports minimizes lag". What turbo is not positioned next to the exhaust port? If you compared a large turbo and a smaller turbo located in the same position, are you going to sit there and tell me they'll have the same lag? LOL
Since I rebuild/port my own motor and do all the work on my own car, I'll be certain to get your advice.

Trexthe3rd

I remember somebody posting something like that a while back, but it was a joke though.

Conv.WS6

here is a good reference site for a SC Carb 13B Extended port.
http://www.fullboost.com.au/cars/rea.../scottrx4.html

here is another
http://www.ridejudge.com/RideDetails.asp?RideID=7313

An electric Super Charger would be nice. Would go right along with the Electric Water pump.
That would awesome for drag, but the weight of the Electric motor to drive it might be alittle bit of a negative.

SPOautos

The only sc setup that will have less lag than the stock setup is a positive displacement sc. The only problem with them is that they are much more INefficient than proper sized turbos. The centrifugal is going to be more laggy than the twins and is also less efficient than a proper sized turbo.

As for the turbos creating a lot of heat "issues" its really not that big a deal. The air intake temps dont go up because of the exhaust heat, they go up because your greatly compressing the air. If you compress air the temps go up, it doesnt really matter if its a turbo, sc, or whatever. SCers are going to heat up the air more than your stock twins with a decent IC. If you check out Jacksone racings website they say thier sc ONLY increases the air temps 76F at WOT, however they dont ever specify what boost that is!!! Its prob at 8psi which is I think what thier standard kit runs for the car in thier example. Well, my car only runs about 20F over ambient with my SMIC and thats running 18psi on pump gas.

Coolant issues arent realitive to the turbos either, its not under hood temps that cause the problems. Its high combustion temps and small radiators, your combustions temps are going to be the same either way if your running the same boost so its really doesnt matter if its sc or turbo

In addition most SCers still need some form of charge cooling when you run over 10psi anyway so in the air temp regaurds they really arent as different as you think. Besides that its going to be a big *** chunk of metal in your engine bay thats probably 200+ degrees.....you doing think thats going to add to underhood temps???

Probably the best SC for our cars would be a Whipple.....however since they dont make one for our cars your s.o.l. It has to be designed for a spacific application cause it replaces all the intake manifold system, tb, and computer so making your own kit is going to be pretty much imposible.

As for the whole "can control boost easier" well yea....and the drawback is that you can controll it easy cause it cant change......which means thats all you can run, unless you can hop out and change your pulley at the red light (which you cant)....thats why I wouldnt want it.

Besides, honestly I never had a problem controlling my boost with a full exhaust.

STEPHEN

89Turbo944

Well i was not joking. Im shur its possible and i have seen a few "electric turbos". They look like a leaf blower with the big tube taken off the front. Apperantly they actualy do add hp to non turbo cars. Somethig like 4psi per turbo.

But im shur you could use a belt driven SC and make an electric motor to power it instead of the crankshaft. Im shur the motor would have to be of considerable size or you would have to use something to step up the power. But it could be done.

If you mad one and it worked you could make alot of money. No draw on the engine but still getting the advantage of a SC. Im shur you would see former turbo owners switching to SC.

Well it would be intresting anyway.

artguy

blowers are cool!

artguy

sorry for the two minute bastardization of your car 89turbo!

lol

jimlab

No, they don't.

What would be the difference if you drove the supercharger off the crank pulley or off an electric motor large enough to power it? Not a heck of a lot once you installed an alternator (or two) big enough to handle the amperage demands of the electric motor, and you'd be adding a lot of weight, not to mention the mounting problems. It's all parasitic loss. Something has to power that electric motor.

Unlikely. Turbocharging is "free" horsepower, in that it uses exhaust gases which would just be exiting the back of the car to pressurize the intake. There is no parasitic loss associated with a turbocharger. In addition, boost from superchargers is linear because they're driven directly off the crank pulley; X rpm = Y boost. You can under or overdrive the supercharger by changing the pulley size, but it will still turn at a fixed rate in relation to the engine rpm. A turbocharger is relatively independent of engine speed and can therefore build maximum boost much more quickly.

Look, I understand that you're really enthusiastic about being here, but posting in every thread you come across just for the sake of posting isn't going to endear you to many people, especially when you don't know what you're talking about. My advice is to tone it down a bit and think before you post. We don't need another Christi in the 3rd gen. forum.

DomFD3S