Supercharger Advice

[xBlitzkriegx]

hey guys,

i recently purchased a 97 cobra vert with 20k miles on the clock. it is/was a garaged queen that still wore the factory tires from 1997 when i bought it. those have been reaplaced obviously =P. they were dry rotting around the bead and shoulders. anyways...

im interested in possibly supercharging this car for added street fun. im not looking to take it to the track to race though i might take it once or twice just to get kicked off for going too fast in a vert lol.

im not interested in modifying the car beyond the supercharger, so no deep gears or headers ect ect. basically, im interested in a stock appearing and nearly stock sounding car thats a bit faster than stock. i dont care about dyno numbers so long as the car is correctly tuned. i dont care if the car hits 400whp or not. i do care about having fun on the street, effortless passing, and maybe outrunning an FBod here n there. i dont want anything thatll cause me to lose the factory strut tower brace if i can help it. i will install a better clutch if needed.

i do plan on putting a decent shifter on the car. thats about it for extra mods. i might, MIGHT do a cat back exhaust just for extra noise. oh, subframe connectors are a given. those go on no matter what.

given those paramaters, should i even worry about a supercharger? the alternative is to stay N/A and go 4.10s, full exhaust to include long tube headers, catted x pipe, muffs, a decent CAI, and some sort of tune and call it a day. im not interested in running around on the highway at 2500rpm+ at 70 but ill put up with it if i have to. obviously this setup with be slower but it would probably satisfy me as well.

the ultimate goal is to have a reliable car thats fun to drive and isnt stupid slow. its not too bad now, but stock sucks. thanks in advance for the help.


p.s. im not entirely interested in centrifugal superchargers since they need rpm to work. since i dont plan on twisting the car to 6000rpm to see the hp gains imo theyre not the first choice for me. i have seen some dyno graphs that show before n after and it seems that the centrifugal 'chargers dont really help until 4000rpm, past where i drive normally anyways. seems a waste if youre not racing.

 

[wannaboost94gt]

Go with a kenne bell

 

[Mustang Mark]

^what he said

 

[IceMan]

The power range for all the superchargers will not be too different. Roots style blowers will make more torque in the lower RPMs. By reading you post I think that a supercharger is something that will not be the best idea for you. You want "this" but you don't want to do "that" to get "this". Just leave the car stock or put a small shot of nitrous on it, tune it and use it only when you feel frogy. I'm sorry I don't mean to sound like a dick, but you seem like one of those guys that just want to bench race and say that they have a supercharger on their car just because they think it will scare someone off and make you look cool. When I put my first supercharger on a Mustang I could not stay out of the throttle. Boost was like crack and I wanted more of it. BTW you need RPMs to go fast so you will have to give your car some chin music. Personaly I have had 6 boosted cars so far, 4 of them supercharged, and have had centrifugal and roots blowers, and I like the centrifugal blowers better. Roots blowers make a lot of heat and aditional stress to the motor. At the end it is up to you. Good luck in any way you want to take with your car. I say if you want a stockish car than do some bolt one and leave it alone. Don't supercharge it. Maybe put a small shot on it.

 

[xBlitzkriegx]

lol thanks for the advice.

im not really looking to race the car. been there done that with a Mopar and to a lesser extent a 4 banger Olds.

i just feel that the stock version Cobra is a tad slow and im worried about blowing the engine. i see people making around 400whp and some break thier engines and some are fine. i also read that most of the guys that break things at the low 400 mark seem to have bad tunes or improper tunes.

honestly, i might just go 4.10s and a full exhaust. id rather not lose my kick ass fuel mileage but performance is always a trade off. who knows, i might be fine with that and those items would always help later on. would be nice to keep the rpm down at 70.

my only gripe with nitrous is the cost to refill/short usage time. its obvously the cheapest route and has the most bang for your buck value.

conerning the centrigual blowers, i was only able to find about 3 dyno runs that showed what they made but they were all built engines [ they blew the stock bottom end which is what im trying to avoid ] that made 450-600+WHP. my goals arent that high.

the main goal is to have a "fun" car. it realistically might not require a supercharger. the goal is to not get laughed at when the loud pedal goes to the floor, vert or not.

 

[OnyxCobra]

I'd say definitely go with the KB, you'll lose your factory strut brace but that's fine since they say it doesn't do anything for the car anyways, but actually cost the car 8hp cause of the dip cut out of the intake tube. Subframe connectors will make the car plenty more rigid.

I drove a 97 Cobra with a KB and 4.30 gears and it's not something I'll easily forget.

 

[IceMan]

You have a a low mileage Cobra. Don't ruin it. Put some bolt ons and be done with it.

 

[OnyxCobra]

a KB setup won't ruin anything if he does it right.

 

[blown98gt]

a s/c wont ruin a motor, yes with any power mods on a stock motor you can apply stress to the motor AFTER a certain point. 8lb/10lbs from a KB is not going to ruin or hurt a motor when done correctly. you want to talk about runing a motor throw around 150 shot nitrous on it.. lol

my suggestion..
1. S/c whatever you can afford, be it kb, paxton, procharger, vortech.. all will make good power and all are belt driven so when not in boost all you are doing is basically adding another pulley into the mix...
2. 373 gears, not really deep but will beef up your lower rpm's just a tad bit without causing you to lose too much on the top end.
3. 42lb injectors, a 90mm lightning maf will be sufficent for what you are wanting and i'd recommend a 255lph intank pump..

also keep in mind, you can always put a smaller pulley on the blower so you don't have to spin the motor as high in rpm's to achieve more boost.. although i'd wouldn't go higher than 10lbs of boost on a stock motor.. a good tuned 10lb s/c on stock motor will give you some decent power and you'll be happy with it

 

[modo]

put a vortech on it and call it a day. vortech is cheaper, more efficient and comes with a 3 year warranty

 

[OnyxCobra]

you can always put a smaller pulley on the blower so you don't have to spin the motor as high in rpm's to achieve more boost..

KBs don't build boost with RPM, a smaller blower pulley is just going to give you more boost whenever you ask for it.

 

[xBlitzkriegx]

i was looking to jsut throw the s/c on the engine and call it a day. id prolly go with the 8psi pulley since we get decent gas around here. i didnt want to bother with deeper gears or really any other mods since the car wouldnt see more than about 2-3 track days ever. i know that deeper gear would be great but this car is my DD and it sees a good bit of freeway time.

since this car is a vert, i was just more interested in good street manners and some beef under the hood. i have a 69 notchback barracuda if i wanna have fun. its run a 12.12 @ 112 personal best. that was at memphis motorsports back in the day. i miss that track my point is that ive owned a fast car before so this car wont become my little obsession like the cuda did when i was 18 lol.

if i do go the s/c route, again, i just wanted to pretty much bolt on the s/c and subframe connectors and call it a day. i figured if i stayed stock with everything else, that would give me decent power until i bought LT headers and other supporting mods then go tune it in Dallas. im about 99% sure theres no one in Shreveport thats competent enough to tune a 4V Cobra.

ive gotten alot of good feedback here from all of you, thanks. nice to see that this forum is pretty helpful.

modo, i understand where youre comming from but im concerned about the powerband that ill generally be in which will be from idle to about 3000rpm most of the time. i know that the centrigual s/c will be more efficient up top but i dont plan on haulin ass everywhere i go. i mean, i would but police dont like ppl shifting at 6800rpm from a dig at green lights. not to mention, my wife would be driving this car from time to time. hmmm....maybe i should go centrigual after all lmao.

does anyone know about what rpm a positive displacement and centrifugal s/c would cross over in terms of torque production? in other words, when the the centri catch up?

 

[OnyxCobra]

I think it would vary on the centrifugal blower and boost levels, I'm no expert but I'd probably guess around 4000rpm. Like I said just a guess.

 

[modo]

modo, i understand where youre comming from but im concerned about the powerband that ill generally be in which will be from idle to about 3000rpm most of the time. i know that the centrigual s/c will be more efficient up top but i dont plan on haulin a*s everywhere i go. i mean, i would but police dont like ppl shifting at 6800rpm from a dig at green lights. not to mention, my wife would be driving this car from time to time. hmmm....maybe i should go centrigual after all lmao.

does anyone know about what rpm a positive displacement and centrifugal s/c would cross over in terms of torque production? in other words, when the the centri catch up?

do you know how to read a compressor map? every model (trim) centrifugal is different and has a different use. Too many people think the only difference in trim is the amount of boost. Boost means nothing. CFM, adiabatic efficiency are what matters. You keep bringing up the point that you want it in low power bands but unless your at WOT at those low rpm bands no supercharger is going to be doing anything. The S/C will not build boost unless the motor is at zero vacuum and that only happens at WOT (regulated by the bypass valve).

A Vortech Si or T-trim / Paxton 1220 would give you everything you want, be cheaper, come with a 3 year warranty and walk a similar equipped kb car every time. But it sounds like you already have your mind made up.

 

[modo]

I think it would vary on the centrifugal blower and boost levels, I'm no expert but I'd probably guess around 4000rpm. Like I said just a guess.

varies on the compressor map, and its a lot sooner then 4000

 

[KWClutch]

If you're worried about MPG as stated by not wanting to put 4.10's on your car a S/C is going to be worse. Also just make sure that you have the money to build the motor if it blows. Most motor builds cost about 5k. Yeah you "should" be fine with only 8psi and a good tune but I wouldn't bank on it. These motors are known for spinning bearings even in stock trim. If it were me and had a low mile Cobra I'd either garage it/weekend drive it and buy me a play Cobra or do only bolt ons and gears. That'll give you about 350 to the wheels with a good tune and that's plenty for what it sounds like you're wanting to do.

 

[OnyxCobra]

The S/C will not build boost unless the motor is at zero vacuum and that only happens at WOT (regulated by the bypass valve).

I've driven a few s/c cars that boost without being WOT, which s/c needs WOT to boost?

 

[Lee12609]

The S/C will not build boost unless the motor is at zero vacuum and that only happens at WOT (regulated by the bypass valve).

I've driven a few s/c cars that boost without being WOT, which s/c needs WOT to boost?

LOL, all of them. the bypass valve is held open with vacuum, the only time vacuum isnt present is during WOT, at which point the bypass valve shuts because of no vacuum, and then boost starts and holds the bypass closed, when you let off instant vacuum and the bypass opens again.

if a car is boosting at less than full throttle it has a problem somewhere.

 

[OnyxCobra]

no, that's absolutely not true at all. Superchargers also boost under load, they do not only boost under WOT.

 

[Lee12609]

no, that's absolutely not true at all. Superchargers also boost under load, they do not only boost under WOT.

centrifugals wont start building boost until 0in of vacuum, the only time you see that is WOT.

with an Eaton ive seen small boost numbers at high loads without WOT, I would imagine all positive displacement blowers would be similar, but all centrifugals with the plastic Bosch bypass need WOT.