There's a lot of threads being made by people wanting advice on which FI system to go with, blah blah blah, so maybe this little write-up will help them choose.

I had a Vortech last year with the 3.12 pulley on my 5AT coupe, stock everything else, and was putting out roughly 370/330. Although it was fun (my first boosted car), it wasn't everything I wanted it to be. My biggest gripe with the CSC (centrifugal supercharger) is that you have to be in the right rpm at the right speed to get the most out of it. For example, at 60mph, the 5AT is right at the beginning of 3rd gear and it takes a while to build boost and get going. On the other hand, 3rd gear at 80mph sends you flying.

When taking curvy roads, I always had to make sure to downshift right before I enter a turn so that I am in the upper portion of the rpm band when I exit the turn for optimum acceleration, otherwise I would be too low in the powerband and by the time I built boost, another turn would come and I'd have to slow down again.

The acceleration with the Vortech is very linear and although it doesn't knock you back into your seat, it gradually pushes you into it. It's a very predictable system and I can see why people like it.

This year, I built my block and went with Greddy twins. Due to issues with the transmission, I am currently on the wastegate spring at about 4lbs of boost(not a problem for a stock block). I think the numbers are somewhere around 320/300 on a hot and humid day.

The car is now completely different. I hit 4 lbs of boost at about 2800 rpm, maybe even sooner. I have instant tq when I want it. It doesn't matter what speed or what gear, when I get on it, the car takes off and I feel my front end lifting. To try it out, I got on it at 50mph in 4th gear and the car still moved. I don't need to downshift to pass cars on the highway; just put my foot on the pedal and go!

The twins pull hard all the way to redline. At 4psi, there is absolutely no drop off in power or tq. WHP goes up until redline and the tq is flat all the way to redline. I am pretty confident in saying that according to my butt dyno, the twins at 4 psi are easily just as fast if not faster my Vortech was. The fast influx of tq when I get on it is unreal (which is why the 5AT tranny slips sometimes). I now know what people mean by area under the curve

For the 5AT guys....the best thing about having an auto and twins is that the tq converter locks up right before full boost. I have almost ZERO turbo lag. As soon as I get on it, the needle jumps to about 2700 (stall point) and between 2700 and 3k, I build 4 lbs.

For comparison's sake, my 5AT with twins on 4 lbs and heavy 20's walked an 05 elise and put about 3 cars on a 335i from 40-90

For all you guys thinking if the twins are worth it...IT IS! I should have done this in the first place. And, this is only on 4 psi so all you stock block people can easily handle it.

Built tranny with 600whp coming soon

Edit: the 2 HKS SSQV's sound nice too

Also, I'd like to mention that your 5AT tranny will most likely be fine. I was having issues before the Vortech and beat the crap out of it while it was supercharged so my tranny is not an indication that yours will slip too.

 

Great write from real-world experience. You were dead on about the Vortech; however, the Vortech is much more fun with the 6mt I bet that 335i never knew what hit him.

 

If you can get over the cost hurdle I agree. Turbo its twice as much as a supercharger because most people can't do the turbo install themselves...

Vortech: 5k parts, no labor
JWT/Greddy: 7k+ parts, 2k+ labor

 

Great write up Andy.

 

Wonderful write up! Thanks!

 

good write-up! so how many pounds of boost can a stock block and stock tranny safely handle? and how much whp does that equate to?

 

depends on waht kind of f/i you are asking about. turbo and sc at diff pounds equate to diff whp.

 

^ on the greddy TT kit?

 

great write up, but like you said it's the butt dyno that makes you feel things the most. People say when you go drifting around a road course you feel like you're flying faster than anything can possibly go, but then a smoother car going though the course in the traditional way that doesn't feel as fast ends up being the faster lap time

my suspicion is that if you were doing 370/330 with the vortech, even though it might feel slower driving around town, it'd probably be the faster car than a 320/300 greddy TT if you were to actually race them

there's no question the greddy is going to be the more exciting kit to drive out on the street. Like you said, you can do everything in low rpms without having to practice normal downshifting techniques which is convenient in traffic

yeah I wouldn't expect an elise to be much competition 40-90, even with a stock Z. Once you're moving into the higher speeds, the light weight starts losing any advantage it had and hp starts to win

anyway, congrats on the switch and moving into the big power levels

 

Thanks I agree, the butt dyno is not very accurate, but it sure does feel good

I wish I made it to the track with the Vortech so I could compare, but it's alright. It's definitely a blast to drive. Unfortunately, the stock VB isn't very happy with all that sudden torque and it sometimes jerks a little 1-2, and 2-3.

Overall, though, I am very pleased with the performance. I decided to put the stock cats back on so the exhaust is pretty quiet now. Once I get an inspection, I'll probably put the test pipes back on. If I'm feeling eager, I may drive around at 8 or 9 lbs from time to time (yes, tuned); gotta love the EBC.

This has been debated non stop. I, personally would not go over 400whp. The amount of lbs required doesn't really matter. The tranny...who knows? VB and TQ converter are a must. I wish I had done that before the Vortech and saved my tranny I would also recommend a cooler. It behaves a little weird after a few hard pulls

 

Nice comparo !!!

When you up the boost a few pounds you'll make more whp than the SC and be more satisfied

 

I had the same experience when I went from the Vortech to the APS TT setup, even though I am boosting more than 4lbs but the bottom line is that the car is a lot faster than my Vortech was. I have uograded my TC and VB as it was begining to become an issue but so far so good with the new setup.

 

Can you PM me the make of your VB and TC and what stall you had it set at? Thanks. I heard Sharif is not doing the VB's anymore. I'm contemplating getting those before I build just to see if a full build is necessary.

 

Great write up.

I feel the same way about the Stillen Stage 4 I had before my Greddy twins. Unlike the Vortech the Stillen had lots of power down low but just wasn't enough. I wanted more power but keeping the low end power. Twins give you the best of both worlds.

 

Excellent right up,i like tim came from a stillen stage 4 and while i liked the pull of the stillen the greddy,s are a completely different animal it just dosent compare at all. .Btw what vb and tc are you using.