supercharching options

328s were CIS also, as was the Mondial 3.2

 

Scott~

From all I have gathered, the CIS cars fuel system is virtually bullet proof in both reliability and mixture control. While its not a good system from a NA performance standpoint, it needs virtually no alterations to work with boost, as it simply responds to the added volume of air with an equal amount of fuel. I am sure it may need somthing done if you went way up, but up to maybe 500 HP it probably is fine just as it is.

In addition, the 308 series, all have much lower compression than quoted as being 8.8:1, as the pistons stop .055" short of the deck, so actual is more like 7:1 and possibly less. This is why the motors of cars that added boost have worked so well. It is also why no one has ever seen the factory quoted 255HP of of the early carbed cars. Jack the CR up and fix the ports, and it jumps beyond that and then some with the euro/early US carb cams.

I think a simple single turbo system using the stock headers could be accomplished, but most of the systems so far have left the turbo way down low and it cant drain back to the sump properly. It needs to be up higher, maybe where the sump sits on the dry sump cars? Maybe relocate the oil cooler to the front of the car? This would also allow better cooling of the turbo and may even allow a intercooler to be jammed in there. But this would also allow the car to be returned to stock without altering anything, and because the fuel system and stock induction remains intact the car would run and drive normally at low speed, a big plus. 350 HP should be easily attainable and reliable without need of an intercooler if everything is spot on and kept cool.

 

I think Scott was talking about a centrifugal blower, not turbo. Centrifugal Blower would be fantastic and i am all for it, takes up less space, less poumbing and heat, with no lag. i would convert my carb 308 to FI with a Planetary drive blower if the 'kit' was available.
john

 

I *really* *really* want to put an intercooled centrifugal supercharger on my USA 308QV (I'd been looking at www.procharger.com but obviously there are many brands out there) and would purchase a plug-and-play for the brackets, etc, that it would take to adapt an off-the-shelf supercharger and EFI. In fact, I'll commit right now if you need someone to help prototype it.

 

Say that again? The CIS airflow sensor plate is a mass flow sensor, not a pressure difference sensor. It's opened by the force of the air moving thru it. (Or am I missing something???)

Ferrari used it with the 2x8 Turbo engines it built for Italy, & I think it was used with the 288GTO turbo system. It's been successfully used with several after market turbo conversions as well.

BTW, why a centrifugal supercharger?
As primarily a street driver, I'd rathar have my added power & torque at much lower RPMs than the centrifugals provide.

 

I'm seriously considering the SuperCharger option for my Mondial-8, so the market isn't limited to 3X8's. Judging from the interest I've seen in this topic over the last year or more, I think there is a market for it. You can count me in.

 

SC has plusses and minuses as do turbos, a centrifugal SC is the worst of both worlds IMO. It probably is a bit easier to plumb, the loss of function and performance is really not the savings. There are reasons that no OME manufacture since the 50s has tried to sell one. If you must have one, look at a paxton. It has a gearless planetary drive that will slip at a given load, so it flattens out the boost curve a bit.

The problem is that a centrifugal compressor has an exponential flow curve, but a piston engine has a linear curve. I looked at installing one myself years ago, but when I got the flow curves and did the sizing I found that to have 10 psi at redline, I’d have basically no psi below 4000 rpm. Not very useful on the street.

With a turbo you can get maybe 5 psi by 3000 which is nice and the best peak power. A positive displacement blower you will get about ¾ full boost at idle, and that is really nice. My engine makes more torque at idle than a stock engine makes at any rpm. Driving around town I usually shift by 3000 because there simply isn’t any reason to rev any higher, it just makes the tires spin.

I think you’ll find that a roots or screw type blower fits very nicely where the CIS unit come out of. Any CIS manifold can be converted to EFI without a great deal of effort. A haltech E6x will read the stock crank pickups, fire the stock distributor (but allows the timing to be programmed) for something like $1500, the stock CIS fuel pump works up to about 400 hp.

I would get rid of the CIS. It can be recalibrate to work, but it’s a lot tuning time to get them right (you need to change springs so it doesn’t max at the flows you’re using, then re-size the injectors or alter the fuel pressure to get the mixture correct) and stock they aren’t good for much over 300 hp from what I’ve read. EFI is so much easier, plus you get programmable ignition along with it and you need that anyway to get boost retard, or add a second box.

 

I agree that they are better than nothing. The dyno curves I've seen with a centrifugal setup make great peak numbers, but have terrible looking torque curves and aren't very driveable or honstly noticably faster in normal driving conditions. To be a good setup, it needs to deliver a wide torque curve IMO and the set-up you are taking about simply can't.

I did look ading a CVT trans to the drive of a centrifugal blower, that would allow the bloost curve to match a turbo's but without the lag...but it adds parts and still isn't nearly as good as a positive displacement.

The last point that has already been mensioned is that only the 348 has EFI. 308s and 328 would require a conversion or a CIS re-tune.

 

Tnx, I understood that issue, was figuring on having to change the CIS metering spring & go to larger jets. Thought you had some other concern.

Not sure that an RRFP w/CIS would give you the mixture control you'd need tho. Without recalibration, the CIS would still stop controlling fuel flow when the plate reached it's stop, which would be well below WOT. How would a RRFP help?

I'm with Mk e, we 3x8 guys need about 100 - 150 more hp, starting down around 2k RPM. I also think that we're the bulk of your potential customers. While the 348s & newer could use some more hp, they aren't as far down on power as the 3x8s...

There's an Fchat member that rebuilds CIS systems. Suspect he could come up with the recalibration kit & larger jets to match the SC. Maybe even perform the recalibration as a service.

 

Scott,
A search of the archives will answer most if not all of your questions about Mk e's project in detail.

Mk e's project was covered in depth in a handful of threads. His trans. is stock. His clutch is a multiplate (carbon fiber or kevlar) special, last i checked, his engine was pretty much stock. The intercooler installation was a major effort. He had to give up his A/C.

He's on his 3rd generation project. His 1st generation supercharger would probably make most of us 3x8 crowd happy, it was in the 350-400 hp ballpark. If I remember correctly, it didn't even have an intercooler, which it probably really needed to avoid detonation.

One way of getting the cost way down would be to find a way to use a supercharger from one of the GM or Ford production sc cars. Used or rebuilt GM or Ford scs s/b pretty cheap compared to new ones.

Being able to keep the CIS would be another big savings. Having EGI as an extra cost option for those who want the extra 30 or so hp would be desirable.

Your concern about people grenading their engines is very valid any time forced aspiration comes into play.

EFI adds a whole new dimension of risk as you can just as easily detonate an engine if the map lets it go too lean, & the map has to be tuned in in the first place.

 

FWIW, I have a considerable amount of time on the flowbench with the Bosch unit. My results were the stock Bosch does not come anywhere close to maxing out, even with an OS TB. As I recall, the air door (flapper plate) was about 1/2 of it's travel @ 3" HG. The tests were done sans fuel as it would have been a dangerous testing situation to say the least. Without fuel to apply counterforce on the Pintle, the travel would be more than under actual operating conditions. I do not feel it wuold be a problem to run the Bosch system with a smaler blower, as it should handle the flow requirements. You shoud adjust the fuel curve to richen the mixture, but that is not a difficult task.
If in doubt, dyno test one with the air filter off, to observe the travel.

 

You may want to check with the guys at 928motorsports.com

They sell a supercharger kit for the CIS 928 and may help with your product development.

 

Scott,
The effeciancy of the centrifugal units was always been quite good, it's the shape of the flow curve that's the problem. Get the flow maps for any compressor you are thinking about and overlay the engine's NA flow curve on it. What I found 5 years ago was a big mis-match.

CIS is doable, but it's a lot of tuning time to get it worked out....and you still need to add a boost retarder for the ingition timing. It might be cheaper, it might not, I never did the map because I didn't feel keeping it made performance sence.

An intercooler is required for over 7-8 psi roots (I got away with 10...barely), 10-12 screw/roots/centrifugal (SC or turbo). The standar way to do it is a water/air with hoses run up the rocker panel to a heat exchanger in the front. A/C can be retained...I just haven't re-connected mine yet, it on the list though.

If you decide not to pull the CIS, space is a bit of a problem...maybe though.

 

I would have thought that a series of staged kits would be the best way to market this idea, STARTING with EFI.

There are planty of threads where people are looking for EFI just to improve power and efficiency a little. Creat a kit that does this, and you not only have a larger audience, but you have a perfect base for a forced induction setup. The larger audience helps defray development costs, and will ultimately lead to a portion of these folk wanting more, thus increasing the potential customer base for any sc/tc kit.

Now.... come up with a list of requirements for an EFI manifold that covers all the bases (NA, SC, TC) and I am sure that one could be designed that could be cast for a very reasonable price. I am thinking a modular system that allows for split plenums like the 348 for NA or twin tc, individual throttle bodies like the 355 for those that just wann have fun, and then single plenum for single sc/tc options.

Anyway, food for thought perhaps.

Dave

 

I have seen 3 seperate SC units mounted on 308s. 2 had the blower mounted on top of the engine, the 3rd was mounted behind the engine where the CIS unit used to reside. In that I already have EFI (via Electromotive), the third option makes the most sense for me.

Without considering the EFI conversion, the SC conversion will probably price out about $6K-7K without intercooling, and another $2 - $3K - installation excluded. If one is thinking about "making money" on this, I seriously doubt there are that many people willing to pony up to make it a viable business venture. However, if there is someone willing to do the design work and make the mounting components along with putting together the remaining parts list, that may be a different story. I know I certainly would be very interested.

There are a lot of threads on this subject. The real question is how many people are actually serious about doing this?

 

I'm surprised you haven't considered the Lysholm. Here's a description:

Lysholm Screw Blower.
The screw type blower is the newest type of blower to be developed.
On the outside, the screw type looks similar to the roots type, but inside, the two rotors are twisted into a complex screw pattern (called a helix pattern).
The helix pattern was used in industrial applications to pump oil, but was only used in automotive applications to pump air when tolerances were brought down to 0.002mm.
Fleming Thermodynamics of Scotland licence out other manufacturers to produce the Lysholm Blower. The most well known are IHI in Japan (who also make turbos), other companies are Opcon in Switzerland, PSI Corp in USA and Whipple in USA. The Mazda 2.3litre Miller cycle v6 was the first production car to use the Lysholm Screw Blower.

This appears to be the blower of the future and its only problem at the moment is the cost of manufacture. It has efficiency of 75-85% which far exceeds the roots (35-60%) and is well in front of the centrifugal.
It is lighter and smaller then the roots and requires less power to drive it.
It gives the best of both worlds in boost delivery. It provides substantial boost at low levels just like the roots, but continues to supply good boost further up the rev range like the centrifugal.
It was banned from top fuel drag racing in the early 90s but it continues to dominate the 500cu top alcohol class (3000bhp) and there is nothing which looks like beating it.