ViribusUnits

There is no bias toward one or the other with engine sizes.

Turbos where used on those huge US made WWII aircraft motors.

Superchargers where used on the huge British and German made motors.

Turbos and SC are on even small 4 cylinder engines as well.

Anything is possible.

Jim Nowak

</font><blockquote><font size="1" face="Verdana,Tahoma,Arial,Helvetica,Geneva">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva"> I know the Subaru WRX and little SLK Mercedes use a turbocharger. </font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva">Nope, the SLK uses a supercharger too.

Normy

I don't think that there is any correlation between engine size and the choice of supercharging vs. turbocharging.

For example: gm developed a turbocharged version of the corporate 3.8 liter V6 for the GN. About the same time... Ford did a supercharged version of their nearly identical 3.8 liter V6. DaimlerChrysler sells a 2.3 liter supercharged four cylinder in their SLK, while Ford has sold Sierra's [and Thunderbirds] with 2.3 liter turbochared engines. And Honda sold 2.3 liter engines that made just as much power due to nothing more than a VTEC cylinder head...and NO forced induction.

The choice of forced induction method probably has more to do with corporate dogma than anything else. A great example of this comes from VW and Audi a few years ago. These two groups had one owner but separate engineering departments. While Audi was busily mounting turbochargers on the corporate 1780 cc four cylinder [and its 5 cylinder cousin], VW was experimenting with scroll superchargers [the infamous "G-Lader", in which the "G" has unfortunately come to stand for "grenade"] on the same motor.

Turbochargers are inherently more efficient and more powerful, as they are powered by energy that is normally wasted. Banks Engineering literature states that when one of their turbocharger kits is installed on the naturally aspirated diesel V8 found in some motor homes, that not only is there more power but up to a 40% increase in mileage! The turbo recovers energy that is then used to increase the effective compression ratio of the engine... essentially for free.

BUT... turbocharged engines from the factory are deceptively simple LOOKING. You don't see the hundred or so engineers who spent YEARS developing the factory system, all the while armed with a nearly unlimited budget. I found this out a few years ago when I installed a non-intercooled turbo kit on a VW Scirocco. The little car suddenly developed 40% more power...and baked its stock clutch in short order.
Well, a new clutch was installed...and though it accelerated like a bottle rocket, it was no fun crawling under it almost weekly to replace the exhaust donut! There was no flex joint in the kit, so it had to eventually be welded. The point here is that I wound up with tons of trouble, and basically had to try to engineer this stuff myself. By the way, my degree is in Aeronautical Science...not engineering!

The plumbing/fitting etc. that a proper turbo setup would require on a 928 would be a NIGHTMARE! I guess it could be done, and I've even fantasized about getting a couple of 951 heads/turbos, a big intercooler, a whole lot of aluminum tube and a good bender, some silicone connectors and clamps, bigger injectors, and having a friend here in town burn me a chip with boost fuel compensation...But in the end I'd wind up with a burned clutch, an exhaust that keeps coming apart, connectors that fall off, boost making its way into the vacuum system, oil leaks, heat, burned pistons... You know, in the end I'd wind up WORKING ON IT more than DRIVING it! No thanks...

The supercharger kits are quite a bit easier just because they are less involved...but of course they give less results too. And I've read on here that these kits that are available for the 928 leave something to be desired, though I've never messed with one. Most of the people that I've talked to who've mounted them on Jetta's and Mustangs say they had to do quite a bit more to make them run right than the instructions said.

Normy!
'85 S2 5 Speed

Herr Schnell

Jim,

Yep, my mistake.

Viribus, Normy,

Thanks for the info. <img border="0" alt="[cheers]" title="" src="graemlins/beerchug.gif" />

TurboTim

If there is enough interest we would be willling to develop a turbo kit for the 928. Fitting two small turbos on it is not that difficult. Supercharging is alot more complex on this application then some peopel make it sound.Yes a supercharger only requires a few things to make it work like the blower,pulleys,belt and bracetry along with the plumbing.Unfortunately there are only two options for blowers.Roots and centrifugal.The roots blower would require a custom intake manifold.The centrifugal is almost impossible to fit.We have tried;^).Two small turbos with interna wastegates could be plumbed right onto the existing headers of the 928 with a little modfication.The turbo intakes and discharges could be routed fairly easily. Tuning can be accomplished in a vareity of ways and there it is..... a 928 twin-turbo. I uploaded a picture of a twin-turbo set-up we did for a Supra.Although it is not a 928, you can see the type of work we do .You can also see that two T-66s were plumbed into this car so two small turbos is really a piece of cake on the 928.

<a href="http://boards.rennlist.com/upload/supraengine002.jpg" target="_blank">http://boards.rennlist.com/upload/supraengine002.jpg</a>

John Struthers

FWIW,
If you have run into any Supra TT's and whipped them -easily- I'll have to recommend you for a coveted membership in the Tall Tales Club.
Punch up Supra Twin Turbo on your search engine.
You could probably spend an afternoon reading road tests, specs...
About the 8th or 9th site down there is a turbo out fit that does TT to single turbo conversions.
There is a basic single turbo package pictured with price. This should give you an idea of'some' of the needed hardware.
The Supra and Sharks were in the same ballpark for performance, size, weight and looked good to boot. I think they made a few more Supra's than Sharks even though they started production later and finished about the same time.
Like the sHARKs they are fairly rare and have a close-knit, hardcore, dedicated following.
After my local Suzuki dealer sold 5 1200cc Suzuki Bandits out from under me, I narrowed my search for automotive propulsion to the Supra TT and the 928 family. There is a near 30 year old named Tony Strong here in town who has a 2001 Cobra R, and a Mirror Black -I prefered the RED- MY 93' Supra TT amongst other wheel sets.
It is a beautiful, stock TT, that loses to the Cobra R only off the line and at the extreme top end. After a short distance it catches and abuses the 'R'. The fact that fewer were available and many were abused - sound familiar fellow sHARk hunters?- steered me to a final decision on the 928 path.
There should be enough links for you to find someone knowledgeable, with flicks and specs to land you in a budget/space/reliabilty projection zone.
Come spring, I will be looking to find a wrecked Turbo Pick-up truck and start dabbling myself.
Keep us posted.

Drewster67

Turbo Tim -

Thanks for dropping in. It's good to know that it's feasible. I do have a couple of questions.

First of all, what price range would the TT fall into?. (including labor, if one chooses)

Could it be a DIY project?.

Does it matter if it's a 16v or 32v engine?.

Does the driveline need to be modified?.

That's it for now.

TIA

Z

</font><blockquote><font size="1" face="Verdana,Tahoma,Arial,Helvetica,Geneva">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva">Originally posted by TurboTim:
<strong>The centrifugal is almost impossible to fit.We have tried;^).I know that F_A_S_T online has come up with something but the part that you dont know about is all the extensive modifications that had to be done to make it work. The radiator had to be moved forward and the chasis had to be cut.</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva">I have no idea where this came from. I know of two cars with the FAST kit on them, and two others with centrifugal superchargers that are not the FAST kit, but also mounted the centrifugal superchargers in basically the same location as the FAST kit does. FAST uses Vortech superchargers, one of the other ones is a Powerdyne, and the last one is some different brand of centrifugal supercharger. In none of these four cases was the radiator moved or the chasis cut.

Randy Page

I agree with Z. There are no centrifugal supercharger installs that I have seen or heard of that involve removing, moving, or in anyway changing the radiator. You simply replace the fans. And, there are absolutly no modifications required to the chasis. I can't imagine where any of TurboTim's statements came from.

Randy

87 S4 Auto Black/Black
Supercharged & Intercooled

Old & New

</font><blockquote><font size="1" face="Verdana,Tahoma,Arial,Helvetica,Geneva">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva">Originally posted by TurboTim:
<strong>...This is why they dont have a complete kit for sale at this time.</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva">Really, now?

Jay Wellwood

Hmmm....me thinks I smell a rat.

Installation of the piping realatively easy? Come now...look at the engine bay of an 87 S4. Only the skilled hands of a surgeon can possibly move about in there (albeit with slow methodical process). The clearances are extremely tight, to say the least!

I've seen Randy's car in person - no cutting was performed - and the radiator is still in it's original position.

So - what gives???

TurboTim

Easy guys, I meant no disrespect to anyone. We actually looked into supercharging the 928 with a centrifugal unit. I emailed FAST Online about 9 months ago and they didnt have a complete kit available at that time. I thought I recall something about the radiator needing to be moved or something to that nature.

All I was saying is that if there was some interest, we could twin-turbo a 928 pretty easily. I know exactly how to do it for a reasonable cost. I think somewhere around $6-7k would be reasonable enough for those 928 guys that want to go alot faster then they are now. If anyone has any doubts about our capabilities, I would be more then happy to send you a few pictures of our work:^) We have turbocharged or supercharged BMWs, Fords, Nissans, Porsches, Toyotas, Dunebuggies.....We can turbocharge or supercharge any vehicle. Take care.

Jack Riffle

TurboTim;

If you can show me a power increase comparable to a SC setup that will work on a 16 valve engine, at a cost of 6-7K, then let me get out my Gold Visa card so we can talk.

Drewster67

Since powerhause is located in my town, Ill give them a call tomorrow to see what's up?.

TT - do you need a shark for beta testing?. If so, let me know and we can work a deal.

John Anderson

Having worked on 928's especially the 16 valve models I think I have the experience to say twin turbos would be one hell of a tight fit.

It could be done, but it would take patience and a very understanding customer. Your not talking about a one month turn a round (unless there is a KIT available to bolt right on, and after reading this thread I'm lead to believe there is not a KIt yet). The customer would have to be told up front, that he may not have his car to drive during the summer/winter, while this job is being done :-)

The 8 valve would be much easier to work with, at least there is a little more room in the header/strut tower area. But your still looking at plumbing the fresh air to the turbos, from the turbos to the intake manifold, then the exhaust has to be plumbed, unless you can find a way of running the two exhausts to use one single wastegate (it would have to be a big stout sucker too, like the 930 type waste gate at least)your looking at making two separate systems, two waste gates, two dump tubes, and two exits from the turbos and it all has to fit with no cutting to the frame or the body. THe last I looked, your not dealing with a ballroom sized area from the headers back either.

Now the 16 valve, who boooy! Talk about room, or lack thereof!! can you imagine the task of pulling the heads just to get the exhaust off, then fabing a setup with headers to only find when dropping them back on, with headers and turbo inplace, that you have to pull the motor??!! Infact, unless you have bolts holding the head down, your most likely pulling the motor anyway for the work.

What about the MAF signal?? YOu have two turbo inlets that need to be fed metered air, are you going to build electrics too? How do you split the signal? Maybe you can use one MAF, pull it from under the airbox, and move it elsewhere which would allow some tricky fabwork in the area of a split intake. But its bound to offer up its own fitment issues with the intake plumbing that has to be run somewhere from the front of the engine too :-)

Now, lets take this big ball of what if's and maybe's...and add the intercooler!!! This means two sets of pipes running forward and aft, sheesh! THere is room up front for the easy ionstall of the IC, but thats about the only thing that would be easy on this venture.

Now its all in there, lets talk oil and water, first off, the garrets would not need the oil that the KKK needs, its been built on the concept of water cooling, it only needs a few psi and a few drops of oil to stay lubed, but you need to get the water to it...and how will you circulate that water? Electric pump?? I guess you could maybe tap the head for its water to the heater core (thats how I do the S2 and 968) and run it thru the turbos, it should not get above 190 degrees anyway, and thats very cold when looking at the temps your holding down on the turbo. Oil is another deal all together. The 944 series has those great little balance shafts, easy to tap for a feed, but I guess the 928 would need an external source, seperate little pump.

While on oil, we must remember, the turbos MUST be mounted high enough to allow drain to the pan, its gravity. This is an issue that goes back to mounting the turbos and headers...the higher up you go, the less room you have in an already highly restricted area. Maybe you could use a scavange setup like the 930 also, but again, you need a pump to evacuate the oil and dump it back to the pan, two pumps or one? :-) More stuff to cram in there...

I think it could be done, but look at the logistics of such a task. It has been done, but not on a large scale such as bolt on kits. It is definately a custom job, and it will cost lots O cash, and your car will be down for a long while getting it just right.

But, when its done...and all areas have been thought out and delt with...like compression, fuel, longevity, and last but not least, built in a way that allows you to still do daily upkeep without removing the entire setup just to change oil, plugs, whatever....then you have a monster of a 928.

I'd like to own one :-)

Take Care!