bd0nalds0n

From reading the various threads, I realize that the topic is one of some contention. With this being said; however, it appears as though when I choose to SC the car, the solution that will most fit my particular need will be a twin screw SC.

My car is an auto, with the 2.20 rear end, and most of my time is spent below 4k. It seems as though the twin screw delivers the most low-end bang, and that centrifugal SCs deliver the most high end bang, with the inflection point somewhere in the 4k area. Low-end improvement is most important to me.

It also seems as though the Murf kit is the most comprehensive, well-sorted, and therefore "easiest" for the shade-tree mechanic to install. My questions are:

Are my basic premises correct;

Could one get all the components of the Murf kit, except substitute a twin screw for the centrifugal unit (or do all the other components hinge around a centrifuge vs. screws);

Or will I need to go what seems to be a less convenient, less common route if I continue to want to use a twin screw solution?

Could ease-of-installation or other considerations that may not have occurred to me trump the low-end favorability of the twin screw such that a centrifugal unit became more desirable?

Thanks in advance for replies. Again, I realize that opinions tend to be somewhat polarized in this regard, but I appreciate the informative dialogue that tends to result along threads similar to this one.

Shane

Two very different component systems.

Lagavulin

Your assessment is spot-on. If your number one priority is low-end improvement, then I would agree and say the twin-screw would be your best choice.

It is important to note that the centrifugal is really not that far behind, and has a better top-end. However, if you're not a 'racer', then that would not be an important consideration.

That is without a doubt. Every single piece needed to do the install is included.

No. Each kit is unique unto itself; there can be no part swapping except for the injectors.

That is correct.

That would be an individual choice. The respective installations themselves would be a draw I would think (..once one had gathered the missing parts for the twin-screw install).

However, if you are the type who must have a complete kit and abhor shopping to 'fill in the blanks', then Tim's centrifugal kit would win hands down. Get two of your buddies together, and it can be installed in a weekend. The only parts runs required would be beverage-releated.

On the other hand, if you don't mind looking for the rest of the kit, which can take quite a bit of time tracking down all the required fittings, etc, then Andy's twin-screw would still be the way to go.

Either way, you're going to pay. Tim's cost more but has everything included; Andy's costs less, but is incomplete and you pay with your time looking for parts, and the cost of the additional parts once found.

No matter which way you go though, you'll have a good kit and one fast car!

Gretch

I second Lag's answers. Also you will have a great time getting to know your 928's engine bay intimately.......And a car that will blow the doors off of just about anything on the street...............

and they will never see it coming.............

Shane

Actually having visited Andys' site it would appear that he will round up all components that would be needed, but gives the option to shop yourself and save. (In keeping with his original intention of keeping the costs down.) This last March when I was in a rush to get some boost going on my car he offered to sell me the system he had on his car, complete!

bd0nalds0n

Follow up question, completeness of kits aside:

Are there material differences in the installation procedures such that one is more time consuming or difficult? Some elaboration would be appreciated, and thanks so far for the quick responses.

bcdavis

The twin-screw is supposedly quite a bit faster to take on and off...

BUT...

If the plan was to take a car from stock and smoggable, to supercharged, then back to smoggable, then I am not as sure about the time required. Yes, the twin screw can be removed quickly. But the centrifugal uses the stock intake manifold. So you might just need to remove the supercharger to pass smog. With the twin-screw, you'd have to re-install the stock intake components, linkage, etc... Could add some time...

Jim bailey - 928 International

personally I prefer the integrated look of the blower tucked down in the V versus the "add on" look of the "snail" next to the radiator . Mostly however , I just like the fact that there are options .

GoRideSno

I have done a complete install from stock on a friend's 87 S4 in 12.5 hours at a leisurely pace with no help at all.

Everything that is very unique to the system is included so no shopping for unusual fittings etc...just buying the stuff in the links on my website.

I'll will offer a complete kit but it simply isn't hard to order a few things here and there. Some of the stuff in the links is cheaper than I could even get it for at cost. For example seller 16249 sells the BEGI 2025 FPR on ebay constantly for $155-$189. Several of us have bought these from him. I bought one wholesale from BEGI because I needed it next day and it cost me $226. Now add in shipping to me then to you. I would have to charge around $1000 more to save them the 2-3 hrs that it would take to buy the stuff themselves.
I talked to BEGI about seller 16249 and they said he buys them in very large quantity and hardly makes anything off them.


From what I can tell from people saying they have Murf kit serial #xxxx, I have sold around twice as many twinscrew and Jag/eaton M112. I probably have another 12 people waiting on another run of parts. 5 928s have been bought for the purpose of installing my systems.

However you choose to SC your shark I can guarentee that you will be happy.

One last interesting note, Jim Bailey of 928 International, and Dave Roberts of 928 Specialists will both be running my 16v system when complete.

HTH,
Andy

PorKen

Jim bailey expressed my sentiments exactly with the 'belongs there' look of the twin screw.

I appreciate the work done by the centrifugal package makers, but I gotta give a shout out, yo, to my west coast home boy for his engineering achievements.

All the cast parts and the integrated intercooler makes Andy's twin-screw much more of a factory installation.

GoRideSno

Thanks Ken!


Come to think of it, I have a complete kit here now that I cold ship out at the end of next week. After I sold all 12 of the initial run including the Autorotor setup I was using I put the Whipple system I had back together with a large intercooler.
I am going to put it on my car for a photo shoot with Excellence Magazine on Wednesday. After that I am going to return to stock for CA smog test so I'll betaking it back off anyway and I am making more soon.
It consists of
Whipple 2300AX twin-screw used for around 6-7k miles. (I paid $2050 new but)
Parts Groupo mostly new, manifold has same use as SC $1705
New Big Intercooler $935
New #30 injectors cost me ~$225
New Bypass valve cost me $89.00
New BEGI 2025 FPR cost me $226
New Fuel Pressure Gauge and fitings ~$40
New Boost/Vacuum gauge with memory ~$55.00
New Air Filter ~$35.00
Used 85-86 TB from 928 int $100
New Throttle switch from 928 int $54
New Belts ~$50
New Tensioner pulley ~$20.00
All fittings, fasteners and hoses of any sort needed <$100.

I'll gather an ARM1 or you could go for the LM1 that many of us are using $140 v/s $350 for superior technology.
Shipping $100 ground UPS

Total is $5924.00 for this setup.

I am willing to sell it at this price and not $1000 more as I mentioned above for these reasons: The SC is used and not guarenteed as the Autorotors were that we bought for $1725 group purchase price. The manifold is a one of a kind that I updated to match the others and is used as well. Every thing will have a few hundred miles use on it before I take it back off after the photoshoot.

The Manifold SC and IC will be assembled and ready to drop in.
I will leave the stock fuel rails, stock fuel dampers and regulator on the manifold for the price of used replacements, +tax +shipping from 928 Int.

First taker gets it but I'll want a non refundable 10% deposit immediately. The deposit is just to make one think before they leap, again, non refundable so ask questions first.
Or.... maybe I should test e-bay with this one.


Amdy K

GoRideSno

SOLD!

There will be more made soon though.


Andy K

GoRideSno

This has been a popular mis-conception but very wrong.

The twin-screw will produce more power all the way up to about 5800rpms.
Two recent dyno charts, one form my twin-screw setup at just under 7psi and an x-pipe and one from a centrifugal car at 7psi and a RMB showed that the twinscrew has a 45RWHP advantage at 4000rpms. More power was delivered by the twinscrew all the way up to 5800rpms. The centrifugal had a 5 hp advantage peaking at 6100rpms. 5hp = ~1% more HP at 6100 rpms while 45hp = ~18% more hp at 4k rpms. The twinscrew has even a much larger advantage below 4k rpms.




Andy K

Tim Murphy

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Shane

I have an auto '86 that will get Andy's Whipple kit.
I have a 5sp. 86.5 that will get Tim's Centrifugal Kit.
I'll dyno them both and we'll have a better comparison to look at.
The Ott x-pipe is known to add 30 hp. The RMB isn't really known to give anything hp related other than weight savings and a beautiful sound. So I'll pull the RMB off the 5sp and the x pipe off the auto, to eliminate exhaust as a factor. Best I can do other than installing both kits on the same car. (Don't want to go through that hassle) Then it is a matter of which intercooler is more or less efficient, and drive train loss. Anything else I'm missing. I'd like to give as fair of a comparison as possible, maybe even throw in a 1/4 mile time or two!