ptuomov

The heat sink intercooling effect is the reason why some cars out of the factory allow for a temporary overboost for a little while, but not for longer.

For a more frequent and sustained use of boost and high rpms, here's how I would modify the kit displayed below while keeping the cost down. These fall in the category "everyone's got an a$$ hole and an opinion, they are not facts:

- Ditch the intercooler altogether. It's not large enough based on just eyeballing it. Water circulation circuit would of course help making it a "real" intercooler instead of just a heat sink, but that adds to cost. Just create the smoothest possible flow path there instead of adding this restriction in there.

- Straighten the hose that comes from the compressor outlet. If you have to do something to the oil filler neck, do it. That kink is going to cost a big fraction of the kinetic pressure.

- Drop the incorrectly applied knock-off snorkel system. Instead, just put a cobra inlet duct and a large conical K&N filter in the engine compartment as close to the compressor inlet as possible. It'll work better for this application.

- Let the BOV blow to the engine compartment. The current arrangement is a bit silly.

Just to remind everyone, these are personal opinions and beliefs, not facts derived from laws of physics.

Mongo

I would agree that removing the filter ducting on the passenger side for the BOV would drop the cost of the kit too.

Should I go this route later, I would probably opt for a low boost (5-6 psi) kit and buy a Sharktuner for it. I wouldn't need the intercooler and the BOV piping on the passenger side, letting it vent out under the hood. Although, Victor, if you look at other supercharged applications from the factory, these cars redirect the BOV into the supercharger, pre-charge (i.e. back into the airbox). See cars like the SLK 230 and turbocharged Audis.



EDIT: Another thought would be to Tee off the air pump intake hose and just duct the BOV there.

jeff spahn

That's the kit I have and I like it.

Mongo

I like the kit too. The fact that it is so modular makes it simple to install and remove. When it comes to cutting costs in certain areas, I see that as a good thing too. It may even lower the retail price a little, making it seriously competitive with the other kits that are available to us 928 owners.

victor25

We appreciate the input and over the years we have received a lot of good suggestions. Please feel free to voice them at any time. There is a lot of time and logic that went into everything you see above. Everything is as it is for a reason.

First... the intercooler was designed in cooperation with Bell intercoolers and it is a very efficient and effective piece of art. That guy knows what he is doing and he/we made sure it was designed properly!! Plus it is designed to fit right over the MAF and give a nice straight air flow. Other kits have a problem with airflow because of the 90deg turn after the inercooler and before the MAF. They require an air straighter, this doesn't. BTW a stage 1 does not come with the intercooler.

Second .. the design of the Rotrex does not allow for the air to come out on a flat horizontal plain. Vertically, yes, but that is the angle we have to work with. Plus in order to change the oil fill neck, you have to pull the intake. That in turn would make the kit much harder to install. If someone is removing the intake, we supply a custom made spacer that angles the filler neck up and back a little to straighten this out some.

Third... the BOV, intake snouts, and filter are designed on specific and multiple purposes. It allows the air to recirculate back into the intake tract of the supercharger. Thus increasing the filter life, increasing efficiency, and helping meet emission standards. The supercharger can move much more air than the engine needs at idle and cruise, so the diverter or BOV is open more often than not. That air then circulates back around through the snouts, is cooled down a little, and back into the charger without new air being sucked through the filter. Plus lets face, it's cosmetically balanced and it looks great. I personally think it would look stupid with one snout and a big filter hanging off it.

ptuomov

You're welcome. These are just opinions. I do want to question the logic of some of the decisions made in this kit, but a lot of the answers depend on opinions and are not clear cut issues that can be resolved with high-school physics.

I am just looking at this, and in my opinion a much simpler setup with a single conical filter in the engine compartment next to the power steering reservoir would likely make more power. Then I'd leave the existing intake holes open. My guess is that the losses from slightly warmer air would be less than the losses from trying to feed the engine from a single snout.

I would rout the bypass valve and the crankcase breather hoses right into the compressor inlet, if I were concerned about efficiency and emissions.

This may reflect my prior beliefs more than anything, but I haven't really seen an air-to-air or heat sink intercooler as small as that one work in an engine that consumes 1000 kg/h of air. If I may ask, what Bell core do you use?

SeanR

I ran this set up with the filter like you suggest and it really did not work well. I kept sucking the intake tube flat as it could not suck enough air through the only fiter that I could fit there. Once I went to the snout/filter set up that issue was solved.

ptuomov

I agree that the air cleaner will have to be rated for the flow required. K&N publishes the specs of their cleaners. It's only a viable solution if a large enough cleaner can fit in that space.

Mongo

Maybe there is no other efficient way. I'm sure Victor thought this out very well One huge problem with directing the crankcase breathers back into the compressor inlet will cause the MAF to get damaged later due to oil blow by. Another theory for air filter ducting that I have seen on blown 928s would be to duct it into the fender, behind the headlight. I don't know if there is enough room on the driver side to do that, but I have seen it successfully done on the passenger side (which will not work for this setup).

In the end, the original setup is probably the best. With regard to the lack of intercooler in stage 1, I would probably choose this route later. If supercharging, I would only seek about 400-450 to the crank and nothing more since my wife will be driving the car too. I also have only 8.5" rims on the back of my car. Any more HP and the car will just be for exhibition.

robot808

I had the pleasure of meeting Victor last year at Sharks in St. Charles. He is an awfully nice guy.

I also think he is being a great sport here in this thread. As fair as and intelligent as the questions/suggestions that Tuomo is making are (and they are, no offense Tuomo), it has to be a little frustrating to hear that you are doing it all wrong.

Way to keep your composure, Victor.

Mongo

I can admit that sometimes users on here can really harp on others when it comes to new concepts, problems, etc. Nobody likes negative reinforcement. Suggestions are the better, and compliments go a long way.

Mongo

I haven't found any additional pics in the thread about how the belt on the supercharger is run. To me it looks like the original radiator fans are deleted and aftermarket low profile ones are used. Is there a picture confirming this?

ptuomov

The blow thru MAF is a general problem for crankcase ventilation. My car has the same problem. There are two known solutions. First, relocating the MAF to upstream of the compressor outlet. Second, converting to MAP system. In my car, I'd need dual MAFs which is a project. In this kit, there is conceivably space for a MAF next to power steering reservoir. Relocating the MAF there would make this kit in principle CARB approvable (after a lot of expense, of course). The relocation would of course add to the price of the kit.

Yes, I am not trying to just poop on anyone's work to create mayhem. I am trying to engage in a technical debate and for once succeeding! I agree with you that Victor has responded very rationally and not emotionally to my suggestions, and that has allowed us to keep this conversation civil and on technical points. It is very easy for technical debates to get personal, as we've seen here at RL. I am very happy to see this thread now moving to the direction where everyone can agree or disagree on technical points without letting it get personal or nasty.

SeanR

On my iPhone so I'll have to edit this later. The belt is driven off alternator pulley belt. Just a longer belt. The factory fans are used with no mods. It really is that easy to install.

j.kenzie@sbcglobal.net

I have to agree that Victor is a heck of a tolerant guy. He is having his finished design second-guessed and otherwise criticized, and has not shown any sign of impatience. I should say to him that I know very well that each aspect of his finished design reflects many hours of thoughtful decision-making. I am always irritated when someone throws nitpicking suggestions at my work product. I certainly did not intend that for you, Victor. Your system must be taken in the whole for the most part. You know areas that you wish to tweak, and someone here may spot other areas to address, but overall you have what looks like an excellent product.
Thanks you for sharing your design and efforts with us, and please continue to analyze and improve your design wherever you see fit.
Thanks,
Dave