I started modding my 07 GT automatic coupe with the idea that I'd leave it naturally aspirated. I love a lot of instant torque (like a roots or twin-screw supercharger provides), so in lieu of supercharging I added 4.10 gears and a 4,300 stall converter to get the car into its peak torque range quicker. My goal has alway been to have a solid 12-second 1/4-miler (not just high 12's, but low to mid-12's, consistently). This is hard to do in a heavy, daily-driven, automatic car without forced induction.

Well, my wife has finally OK'd a supercharger purchase (yes, she obviously wears the pants in our house - j/k). So, it's time to look at my options...

Roots or twin-screw provide low end, instant grunt. However, with the big stall converter, I'll never be below 4,300 rpm's at wide open throttle to take advantage of that low end torque! And, my stall speed will likely go way up (likely around 5,000 rpm's) with the additional torque from a supercharger, so if I understand correctly, a roots or twin-screw blower might not be as well matched for my combination as a centrifugal blower?

Centrifugal blowers lack a little on the bottom end (compared to the positive displacement blowers), but make much more top end power. As I have the big stall converter and 4.10 gears, I'm thinking that this combination makes more sense. At the track, my car will always be running between 4,300 to 6,500 rpm's. Is the centrifugal blower going to make more power in this range than a roots or twin-screw blower, assuming the same boost level and tuning?

Any advice is welcome. I have a couple months to figure this out before spending any money.

 

PAXTON 2200 ...FTW!!!
BUHAHAHAHA

 

I say go procharger if you want to keep the t/c.

AND---there could be a serious flaw in your logic. Is your current t/c a multi disc? If not, with the addition of a supercharger and big torque numbers, the t/c may not last.

However, if it is a multi disc, then why not take it out and just have it adjusted tighter?

 

Hey Brian, while I don't have a blower, several of my fellow club members from Bad Mustangs Club have blowers. Some have the Saleen and some have the Whipple. One friend has the FRPP Whipple with the intercooler, got it custom dyno tuned, and recently ran an 11.7 at 120 MPH a few weeks ago at MIR. Granted he has drag radials, but the car was COOKING down the track. He was real happy when the car got done after the intercooler upgrade at JDM in Jersey. The other members who have the Saleen, they love them too, and the one guy consistantly runs in the 12.3-12.5 range (assuming traction isn't a problem). Either one of these would suite your low-end torque and your 1/4 mile time requirements. Good luck on the choice. Be sure to post pics when you get it done. Would love to do one myself, but can't justify the $$$ for it, AND my mechanic (dad) would be seriously PI$$ED!!!Even though its my car, he helps me when I have issues with it. Never turn away over 55 years of auto mechanic knowledge.

 

While I would be the first one normally to recommend the whipple, the twinscrew is NOT going to work if he keeps his existing torque converter.

If he is willing to change converters, then I say yeah, whipple all the way.

 

Are you building a track car or will this be driven on the street?
If you drive on the street at all, I would go with a twin-screw. They have a flat torque curve that makes the car feel like it has 500 cubic inches right from idle.
I would change gears to 3.73 and change the converter stall to 3200 RPM and then go with a Kenne Bell or Whipple twin-screw. Most good custom converter shops will change the stall for you if you need to. If not, buy a multi-disc PI converter.
I have owned lots and lots of fast cars since 1977and running a 4300 RPM converter on a steet car is not a great idea.

 

The thought that the centris have much more topend power is not always correct..... case in point, I swapped from a Vortech/Paxton combo at 11psi (3.33 pulley) to a Saleen twinscrew at 11psi (3.2 pulley) and the Saleen makes more power than the Vortech up to 6000rpm. The Vortech made around 15 or so more HP at 6500rpm than the Saleen did but up to 6k the Saleen rules.

On the other end of the spectrum, the Saleen made 100+ more torque at 3000rpm than the Vortech.

I would take psfracer's advice and these other guy's advice regarding torque converters though because my car is a manual trans and I don't have any experience with them in this application.

 

I appreciate the insights, guys. As I've spent a fair amount on the 4.10's and stall converter, I'm not really wanting to replace those now. The labor charges to swap those back out in addition to buying a supercharger would drive the cost of the whole supercharger project outside my budget. Instead, I want to find a supercharger that will complement these gears and stall converter. It will be a stretch to afford a supercharger anyway, so throwing away money I've already spent isn't going to work in my case.

This car is a daily driver, but my commute is only 4 miles to work. I don't mind giving up some streetability in exchange for low 12's in the 1/4 mile. I drove my 425hp '68 Pontiac GTO as a daily driver for a few years when I was in college way back when, and that car had a big stall converter and 3.90 gears (no overdrive!). I drove a '72 Chevy Nova with a tunnel-rammed L71 427-V8 big block (roughly 550hp) on the street once upon a time, as well.

The torque converter I'm running in the '07 is from Fuddle Racing. It started life as a 3800 to 4000 rpm piece, but after I added the JLT II CAI and tune it started flashing higher to 4,300 rpm's from the extra power. It's still a very, very streetable combination right now, and I don't regret going that high at all. I honestly don't know if this t/c is a multi-disc, but my understanding is that it has a huge clutch to handle full lock-up, even at wide open throttle with a high horsepower combination.

So, as much as I think a whipple or twin screw would be cool, it's sounding like a centrifugal is probably better matched to my gearing and t/c?

 

That stall seems a bit excessive for street use. To each their own.

As for forced induction...with that driveline setup, I dont think it will matter roots style or centri...either one and you will be in the low 12s, if not pass the 12s altogether.

 

MM&FF's latest issue just arrived in my mailbox the other day and there is a great article on a bunch of different blowers of all kinds and brands. Nice write up on the Magnuson (Eaton) blower, too, that looks intriguing. I'm trying hard to justify one of the roots or twin screw type blowers as that's what my gut has always told me I'd prefer.

As I work at a Ford dealership and one of my responsibilities is being the store's SVT Team Leader, I'd really like to use the FRPP whipple blower (I wonder if the owner would foot some of the bill or the labor through our shop?). Heck, I'd be totally happy with the 400hp non-intercooled unit (automatic trans friendly version). It's only about 5psi, but 400hp would accomplish my goals. Nobody really mentions the FRPP piece, would this be an OK blower? I'm not looking for max power, just something to run low 12's consistently that's affordable, that will also work with my existing mods.

 

Hi,
not to hi jack but I am following this thread closely. Within the next couple of months I will also be going S/C with an auto and 4.10's, stock converter. I think I will be going Whipple HO but thats not set in stone yet.

 

I pretty much have 0 knowledge of blowers and most everything else car related other than what I have read on these forums. (I've learned a lot, but knew nothing to start). But one piece of advice I can give is that if it's debatable whether you can afford the supercharger or not, it's more than likely a good idea to wait on it until you know for sure spending that money will not harm your finances elsewhere. This is one of the reasons I still don't have one.

 

With the stall and gears you have, I would look in to a turbo. The 4300 stall will put it in boost real fast, and every day driving will be a little easier with the 4.10's. With 4.10's and the butt load of torque from a supercharger in stop light to stop light driving might be a beast to handle. Plus turbo's have a higher potential than most S/C if the right kit is selected.

Don't get me wrong, everybody, I have a supercharger planned for mine, but with 4.10's and a 4300 stall a turbo is a fine choice.

 

With your combo I say go with the Paxton HO kit from Brenspeed. It has very good manners on the street and is a beast at the track. It will not have the bottom end torque of a TS but the top end power is amazing. You will also have plenty of room to grow later on. The Paxton will flow enough for 1000hp with a pulley change if you upgrade your block. I just finished installing the SL series in my 05. These are self lubricated, no oil lines to tap, plus seem to run cooler than the TS I have seen. In the end its all up to you. If you plan the install yourself though, be prepared the Paxton kit is a very tight fit, trust me, I have the scars to prove it.

 

Totally cool to have you chime in. You and I can learn together what others recommend for our combination. I can tell you from experience that if I had known I would be supercharging, I would have not installed the big stall converter. A good Whipple HO will give you more than enough instant torque that a big converter would be redundant.

 

You know, I have been looking at turbos, such as the Hellion kits, but I've owned a turbo car before and just never warmed up to it. A local speed shop has a 500+ hp turbocharged 2005 Mustang GT and the owner took me for a "spirited" drive in it. While it is fast, it just didn't feel good as it took so long to build power. And it was a stick shift car, so he could rev it easily.

I like the feeling of instant power, hence my predisposition for a roots or twin screw blower. I understand that they might be overkill from a standing start with the big gears and converter. Overkill might actually be entertaining, though! I don't mind driving sideways, and always enjoyed big block thunder (huge torque) in the past.

 

I guess it's worth mentioning that I can "afford" to do a supercharger, but I do have competing expenses that my wife always dreams up. We're not rich by any means, but comfortably middle class with two incomes. It's been more a discussion with the wife to free up the money for a supercharger as she doesn't understand how important it is to my happiness. We've spent tens of thousands of dollars in the last 4 years since we've bought our current house on remodelling and renovations. We vacation yearly. We bought a travel trailer. We're going to Europe next year. Et cetera. So, the money is available, but it is so hard to get my wife on board when it comes to spending anything on the car. She is finally realizing that I deserve to spend some money on my car, and she's tired of hearing my talk about superchargers, hence her recent blessings to buy one.

 

killbee, I think you may just have the right answer for my combo. I want to maximize power in the 4,300 to 6,500 rpm range, and the Paxton likely makes much more power than a roots/TS style blower would in that range. I don't need the bottom end torque anyway, as the gears and converter address that just fine (sixty foot times in the 1.80's at the drag strip on street tires).

While you have the Paxton 2200, isn't there a model below that in their lineup? I think I saw an 1100? Non-HO? While bigger is often better, I'm not convinced I need the biggest/baddest setup; just something to put my car consistently in the low 12's in the 1/4 mile.

 

Hey guys,
I totally love the Saleen Twin Screw with my Automatic. You can see my numbers in my sig.
I don't know if I would run it with a 4.10 or 3.73 or stall but with the setup I have, it runs great and is lots of fun with stoke gear and converter!
There are lots of options out there so the more info you can collect the better.
Just depends on what you are looking for.

 

My cars currently in the shop for a Vortech HO unit. The Vortech unit is good for 850hp and is equivalent to the paxton 1200(i believe). More then enough for a DD IMO and plently to blow the bottom end of any car. And later down the road when I go forged internals the blower can be upgraded to a much larger unit capable of sick power.

I know Brenspeed has a nice package for the non-cooled Vortech unit and other goodies. I'd look into them for a system. I didn't buy from them as I got a killer deal installed and custom tune from a local shop but they were a close 2nd.

I'll let you know my impressions when I get my car back either today or tuesday.