4.30 too big for supercharger?

powermaxx · Mar 6, 2007

how big of gears do i go with a supercharged 4.6 are 4.30s too big? do i want 4.10 or higher?

ALLOY2007GT · Mar 6, 2007

You will never get traction in first gear with 4.10 or 4.30 with a supercharged car. If you are going to supercharge your car, stay with the stock gears or at most a 3.73.

Or you can get some 10.5" rims and 315 drag radials.

discofan · Mar 6, 2007

The best all-a-round gearing for a car with a supercharger is:

3.73 for automatics and 3.90/4.10 for 5 speeds..

I have the 3.73s in my car because I run an automatic...

Unless you are running some major sized slicks for the track, then maybe 4.30s but I haven't heard of anyone running 4.30s with a supercharger yet...

Of course 4.30s are a gas mileage no-no!!!

Dave

thump_rrr · Mar 7, 2007

I'm running 4.10's and a S/C.
I'm a track junkie with 800 1/4 mile runs on my car so the 4.10's combined with a 26" tire has me crossing the traps at 6300-6400rpm in 4th.
If I wanted to put power down on the street I'd probably go with a 3.73 of not the 3.55.
Our cold weather up here makes anything over 1/4 throttle a smoke show in 1'st ,2nd, and even sometimes 3rd.
Put the blower on before doing the gears and go from there.

bigcat · Mar 7, 2007

discofan said:
Of course 4.30s are a gas mileage no-no!!!

Dave

there is not much mileage difference between 4.10 and 4.30. 3.55 to 4.10/4.30 there will be a few miles per gallon, but the difference between 4.10 and 4.30 is minimal.

shhak · Mar 7, 2007

Well, I guess I'm the idiot who actually put 4.30's in a supercharged car. LOL!!

I just put 4.30's in my 03 Cobra. And if you're making the power I am (465 at the wheels) I'd have to advise against it. My gas mileage wasnt' effected much. With my 6spd I can still run 80 mph on the interstate at 2800 RPM.

However, 1st, 2nd, and 3rd gears are all useless. Might as well be driving on ice. 4th gear is ok as long as you ease into it. If you run it to about 3000 RPM and nail it, the tires slip pretty bad still yet.

But this is all on street tires. Some drag radials would definitly help, but I don't think it would cure the problem. But if you can find that sweet spot in the pedal and push it just hard enough to keep traction, that thing pulls like a mule. The 4.30's are excellent for the guy who thinks smoking the tires means he's got a fast car though.

I would have to recommend 3.73's or 4.10's at the most. I kind of think I liked my factory 3.55's better. But like I said, my only problem with the 4.30's is the traction issue. If I could run slicks all the time, I'd love the 4.30's.

discofan · Mar 7, 2007

Your explanation was perfect!!!

And thanks for responding to the "Gear Question"...

Good Luck and Happy Racing,

Dave

tom281 · Mar 7, 2007

Well you have to consider the type of blower...... for example I'll be using my 4.10s with the Vortech system and I think it will be a perfect match. If I was running a twinscrew or turbo, I would probably back down to 3.73s.

ALLOY2007GT · Mar 7, 2007

tom281 said:
Well you have to consider the type of blower...... for example I'll be using my 4.10s with the Vortech system and I think it will be a perfect match. If I was running a twinscrew or turbo, I would probably back down to 3.73s.

a turbo's power band be more similar to that of a centrifugal SC than a roots ? it would come in the mid upper range.

i can see 4.10s being fine with vortech. the HO system is still fairly conservative at about 470HP at the crank. i think that is just right. just get some good rubber and i think it will work out great for you.

Here is what i think. If you plan on running higher than 425rwhp, stay with a stock gear set up or 3.73 which is hardly a change from 3.55 so it would be a waste anyway.

SlideWRX · Mar 8, 2007

ALLOY2007GT said:
a turbo's power band be more similar to that of a centrifugal SC than a roots ? it would come in the mid upper range.

coming from 2.0l & 2.5l turbo world...

Most aftermarket tunes I've seen for WRX's & STi's usually have peak boost in the midrange, with it tapering off a bit toward redline. Even for the guys who are running 'big' turbos that don't get full boost until 4k+, boost will sometimes taper a psi or two towards redline. With the boost hitting peak at 3000-4000 rpm, that's where the torque peak is, with a curve shaped like this ^ , up one side & down the other. Mind you, redline is 7000 rpm stock, fuel cut at 7300. Er, 2.0l wrx. 2.5l is 6000ish because of the tiny turbo- it's dead above 6000 rpm with the extra displacement. The STi's & later WRX's can handle 7500 or 8000 redline with stock valvetrains, so the 3000-4000 is the midrange.

Tom

tom281 · Mar 8, 2007

ALLOY2007GT said:
a turbo's power band be more similar to that of a centrifugal SC than a roots ? it would come in the mid upper range.

i can see 4.10s being fine with vortech. the HO system is still fairly conservative at about 470HP at the crank. i think that is just right. just get some good rubber and i think it will work out great for you.

I wasn't referring to the powerband so much as I was referring to the additional overall torque produced by the turbos / TS compared to the centris. The additional torque, albeit at around the same rpm range, will make a steeper gear seem even more steep and traction hard to find.

Mike97gt · Mar 9, 2007

You can run 4.30's but you better run drag radials all the time, slicks at the track and depending on how fast you trap you will have to run taller than stock slicks. BUT the car will run faster et's and 60 ft's if you do the proper suspension mods and run slicks than it would with 3.55's or 3.73's

powermaxx · May 7, 2007

ok so it looks like i will be doing a roush charger and maybe 3:90 gears??
i want to have my head thrown back in the seat!!
the gears will probly be put on before the supercharger

cowtown · May 8, 2007

Just my opinion but I'd do the blower before the gears just to be sure. It's not cheap to put gears in (labour wise) so you may be best advised to see how it feels first and then do the gears when you know how the car launches and accelerates.

forensicsteve · May 14, 2007

My car is a daily driver. I have 4.11 gears and my street rears are 315 Nitto DRs on 10.5 deep dish 17s (MT ET Streets, 27.6 diameter, on 15 inch Bogarts, and skinnies.... for track only). That gives me an effective gear ratio of about 4.3. They're very good in the rain but lousy for traction. 1st gear was all but wasted and quite frankly it was becoming a pain to drive in traffic. Track launches were also difficult and erratic. So I decided to switch transm (I was going to have to beef-up the stock one anyway) to a fully manual automatic...no more clutch...no missed gears but it's not perfect either. I don't have the car back yet, but I've been told there will be a significant learning curve for both street and track.

4.30 too big for supercharger?

powermaxx

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discofan

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thump_rrr

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bigcat

start with the upper hole, and if more traction is

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