FRporscheman

I imagine an IC would be essential for racing, and aside from that would probably serve well.

lsinlv

I would not.

my experience over the past 7 years in S/C ing VW's in the HEAT of the Las Vegas summers, even with A/C, that the IC is helpful, but not needed; especially under low boost applications. Add to this, the unit Carl is "spec'ing" is self lubricated, so you are not adding any additional thermal load to the engine oil.

In my experience in one of the hotest places to drive a FI'd car, with low boost, an IC is not essential and the unit (Rapotr) has a very high addiabatic, so it won't add any real thermal load to the intake, let alone ~.4 bar.

the need to add weight and complcate the design, plus induce additional locations for failure should negate the need for an IC.....again, I ask Carl to:

K.I.S.S. - as this will keep the cost down.

Carl Fausett

+1 I agree.

notthd

I have to agree in the low boost VW world. Our Vr6 here in Va had an almost non-existent temp delta IC or non-IC as long as the SC is lubed. a few degrees did not justify the mod... IMHO-

cheers,Mike

FRporscheman

I gladly yield to those with experience!

So in a hot environment it's better to have a self-lubed unit, rather than one that gets oil from the engine? I was thinking that self-lubed would result in the charger's oil never being cooled = bad thing. No?

lsinlv

my understanding of the raptor unit (and Carl correct me if I am wrong) is that the design is such that you only need to cool for internal friction and pumping, which together are minimal and fall within the design parameters of the sump supplied. Now, add to that a modification that Carl has come up with, which adds "venting" of the crankcase (internal to the charger transmission) and you have greater heat exchange efficiency of the oil in the charger. Thus you get longer oil life, better cooling/lubrication, longer life of the components.

A winner all the way around.

Now, take a Vortech unit (like the V1/V2 or V9's) and you need external oil to lubricate and cool the charger's transmission. With this design you are using both the engine oil and it's realated cooling system, which can compound a bad situation....like in the VR6's...which tend to run hot (and by hot I mean a NORMAL 240F oil temp)......I have seen oil temps on my S/C'd VR run more like my air-cooled 2.5L race-spec 914/6 motor....in the 260F range....and oil doesn't live long at those temps; not even a good synthetic......

Long story short, I think Carl has the IDEAL set-up for our application.....if he can make it work.

FRporscheman

Ideal regarding heat. I'm not complaining but the centrifugal is less than ideal for low end boost. Yeah I'm nitpicking, I know... I suppose my priority is cost and reliability so I too would have to agree Carl's choice is best.

I'm sure he can make it work. And likely better than other kits!

Eric_Oz_S2

Carl - If the kit could be adapted to work with an S2 and in RHD (not sure if that would make a difference) I would be interested - or are there too many differences to make the kit adaptable to an S2?

Would it require a piggyback ECU/fuel controller or only upgraded injectors?

Could you sell the kit without the Raptor SC, as being in Australia it would be much cheaper for me to buy it here, given the exchange rate?

rdhayward

This thread has me wondering what could be accomplished with a supercharger and lower compression pistons, which would still be a lot less expensive to build than a properly turbocharged engine.

Carl Fausett

Its not quite that simple.

In general terms, a supercharger with 75% adiabatic efficiency will add some 90 degrees F /26.6 deg C to the charged air aboive ambient air temp on a common summer day. More if its a hot day, less if it is cool.

But - leave that aside for the moment.

If we pick a nice 80 deg F/ 26.6 deg C day, we know that the case temperature of the self-lubricated supercharger starts at the same temp and gains a little heat as it runs because its location behind the radiator.

In comparison, the supercharger lubricated with engine oil is being fed motor oil that is heated to about 220 degrees F / 104.4 C - and the supercharger headunit will just about rise to that temp.

So, in this example, the supercharger is being heated by the engine oil. Add the increase in heat on top of the 90 deg rise in temp at 75% adiabatic efficiency - and you see the heat rise is a lot.

However, If we are running really high boost on a really hot day, its possible for the supercharger to get cooled by engine oil if the supercharger is hotter than the oil going through it - but that isn't common.

In conclusion - if the hot oil is removed from the supercharger, we remove that heat source from the charged air.

richard glickel

Carl,

One reason that I favor a normally aspirated engine is not having to worry about "staying on boost" and the associated "turbo lag".

What are the minimum RPM required to keep the S/C engaged and is there a similar lag as with turbocharging?

R.

Carl Fausett

Richard, I appreciate the question but I just dont have the time to right the book that your questions would require.

This is going to get into Turbo lag and supercharger "lag" and "which is better? Turbo or SC or a built NA motor" and host of other questions-that-have-no-end.

Remember - I am a kit builder. Not a "one-of" builder, nor a "optimum output" builder. I have to be able to hit a price point and a delivery schedule.

I will say this: our SC kit willbe designed to be simply installed by the average guy on a Saturday. Neither a turbo system nor a built NA Motor can offer that. Ultimately - they may produce more HP, but producing the most HP from all options available is not one of my design goals.

What it will be is a well-engineered, simple to install, reasonably priced supercharger kit that affords a good HP output for the $ spent.

lsinlv

I think I love you Carl....

FRporscheman

Sounds great Carl and I can get jiggy with it.

Carl Fausett

Thought the 968 would be in the shop by now. It was scheduled for the 20th. The Porsche in that bay has not left yet - waiting for parts. The bay should empty and the 968 SC project begin this week.

Just thought you'd like to know. I will try to post progress notes as I think of it.

Thanks to all for your interest and comments.