I want to ask a question about the Supercharger that DDM Works is selling and I need the advise from the forum before I buy. My question is does the compression need to be lowered in the engine before the SC is put on and Why or why not <<<
My question is does the compression need to be lowered in the engine before the SC is put on
No, the compression doesn't need to be lowered.
Quote:
Originally Posted by Rowan1008
Why or why not <<<
The supercharger used in the conversion is only providing a very moderate boost level, somewhere in the 7-8 PSI area. (Compared to a GXP, which has a lower compression ratio, but in which the charger is putting out 14 - 18 PSI)
Any further detail I'll have to leave to the folks from DDM who designed this installation.
__________________ "If you haven't seen the future, you haven't driven fast enough" #000741, delivered 10/3/05
No, it does not have to be lowered because the ECM reprogramming along with the intercooler control any possibility of detonation (or pre-ignition, or pinging) which is to be avoided at all costs.
Other ways to prevent detonation include lowering compression...not necessary in this case.
Jackknife
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Rowan,
If you want to meet somewhere one weekend, I will let you take it for a ride.
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dealer expected deliver 6 March, arrived 28 Feb, picked up that night w 3.2 miles on the clock :)
NOT WAITING ANY MORE!
I've been reading all I can regarding superchargers and after the 2008 autocross season is over I hope to have DDMWORKS install their Stage II SC Kit this winter.
Question for you guys. I've read (as stated below) that it's best to go with an INTERNAL (centrifugal-style) supercharger. The Eaton that DDMWORKS uses seems to be listed as a
Root" or "screw-type" which has been called the old way of making SC. Is the Interanal SC the way to go?
Most of the superchargers sold today are centrifugal-style superchargers, which are internal-compression superchargers, meaning they create the boost (compress the air) inside the supercharger head unit (blower) before discharging it into the engine's air intake. External compression superchargers (roots or screw-type superchargers - Whipple, Kenne Bell, Jackson Racing, Eaton) have become less popular as centrifugal superchargers have evolved. Centrifugal superchargers (Vortech, Paxton, Powerdyne, ATI ProCharger) are more reliable, especially at higher boost levels, and are capable of creating much more boost than external compression superchargers, while creating a much cooler intake charge (which results in an even denser intake charge).
Bump...would really like a response to my SC Internal vs External question from those gear heads out there
The only two S/C systems that I know of that are on the market are Mallett's and DDM's. Mallett, I believe, uses a Vortech "Roots" type versus DDM's Eaton.
The biggest difference I can see in these two systems is where the torque comes and at what level.
Mallett's Vortech does produce more whp, but it's torque curve is considerably lower. based on the dyno's I've seen, the Vortech system acts more like a turbo taking time to spool up.
DDM's Eaton produces, for the most part, less whp. (There is one exception that I know of, and I'm not sure it's legit yet.) However there is more torque, and it comes on earlier.
In terms of reliability here is how I look at it. Both systems are going to push the engine's ability. Your level of care and the quality of the product will dictate how much so. There is no such thing as a perfectly reliable system.
I think, in this case, it's dependant on how you want to enjoy your car. What's best for how you drive?
Admittedly, I think Mallett's system is better suited to a drag strip. The build of power is a blessing on your drivetrain. The monster torque of DDM's system seems harder to control off the line.
On a road course, I'll take DDM's. Your exit speeds out of any corner will be a tremendous advantage. (Of course, it depends on how fast you get into it, as well.)
That bit of info from superchargers online is not quite accurate. First of all, there are three types of superchargers: Positive displacement Blowers (Eaton m-series, TVS, and the old school Roots x-71 series), Twin Screw (Whipple, Lyshom?sp?), and centrifugal(Vortech, ATI procharger) I'll give a brief summery of each
PD Blowers - These only move air, They only move a specific quantity of air per revolution. For instance, the Eaton M-62 moves 62cuin( 1 liter) of air per rotation.The air is not compressed between rotors, the boost is made from pushing soo much air into the manifold, it has to compress b/c the engine can't ingest it quickly enough. The advantage of these is even at low RPM, you will more or less make full boost. the new versions of these(m-series and TVS)are very efficient and have internal bypass valves that reduces the blower power requirement when not in the throttle. With PD blowers there is no lag, the boost is instantly there upon closing the Bypass valve. PD Blowers have a disadvantage at higher boost pressures (more so the old school Roots) , they drain a little more power off the crank when getting to pressures above 12-15 PSI and they generate more heat into the Air. The Newly released TVS don't suffer these problems nearly as much, due to some wicked cool engineering. the new ZR1 Vette has the New TVS2300 on it running 5 PSI boost. The Eaton M-series were used in the Cobalt/Ions, the Mini Coopers S, the Grand Prix GTP, the Nissan Frontier and the V6 Ford Thunderbirds
Twin Screws - These look similar to the PD blower on the outside. But on the inside, they have pecision machined rotors that squeeze and compress the air between the rotors. These setups are more expensive but flow a lot of air fairly efficiently. Just like above, they are Positive displacement units. they will only flow a specific amount of air per revolution. These were used in some Mustang Cobra SVT's but then were pulled out due to delivery problems and cost. They were replaced by the above type with the Eaton M-112
Centrifugal - These are basically low speed turbos driven by a belt. They use a Scroll housing with a compressor wheel. They are slightly more effiecient (heat wise) than the above two types. They are not positive displacement. They basically have to spool. They will not move as much air at lower speeds, but the faster and harder you spin it the more air it will move. Your boost will vary with the RPM of the motor. At 2000ish RPM you may only have 1-2psi and it will gradually increase to peak boost at peak rpm. So if you only run 8psi system you will only have 8 psi towards redline. The advantage is having lots of airflow up top, the disadvantage is having almost none down low. The other real advantage with these is the tight packaging/small unit. To my knowledge, these have never been put on a vehicle by an OEM.
__________________ Randy Carter - Product Manager www.DDMWorks.com
06 Classic Cool: DDMp62 supercharger #0.5b
As to which is better an internal or external supercharger really depends on what you are looking to do. An internal compression supercharger is essentially a belt driven turbo. Since these types of internal superchargers do not move a fixed volume of air per revolution they have to be spun a lot faster than a roots type blower that does move a fixed volume of air per revolution. When you do spin up a centrifugal supercharger set-up, you gear the supercharger to make the maximum boost pressure at whatever your engine redline is. Since a centrifugal supercharger makes boost exponentially based on engine RPM if you make peak boost at redline, at half peak engine speed you make 1/4 that maximum boost. This is why you see centrifugals used a lot on larger displacement v8's and not a lot on smaller displacement 4 cylinders. The larger V8's need something to fill in the torque curve on the top end and the centrifugals do a great job at it.
There are unique positive displacement superchargers like the Whipple, because they do have some internal compression and enjoy slightly high efficiency than the units that we use. The downside of this is that they are much more expensive units to purchase and they also do not have the dependability of the Eaton units.
The best choice for street driven small displacement engines has been the positive displacement supercharger, and that is why the OEM’s have used them almost exclusively when supercharging their stock vehicles. The only OEM that I know that uses a centrifugal supercharger stock is Koenigsegg. I am not sure of any other OEM's that use a centrifugal on a stock car. TRD has an aftermarket kit for the TC that uses one, but that is the closest thing to an OEM that I know of that uses a centrifugal. Almost exclusively the OEM's use positive displacement superchargers on their cars when using a supercharger. The supercharged Ford's, GM's, Jaguar, etc. use Positive displacement superchargers made by Eaton, the same cores that we use in our kit.
Since you are looking for something for your autocross car, the positive displacement supercharger is going to give you a lot more power out of the turns and really boost the midrange of the car, while still adding power all the way to redline. The supercharger just makes that car feel like it has a much bigger engine, it is just as easy to drive as before, just that there is more under the pedal now with the supercharger.
You are welcome to come and drive Randy’s car anytime to experience the supercharger, and let me know if there are any other questions I can answer for you.
