An "exhausting" experience...

[LuLu]

I took LuLu out to the dyno today, to see what develops after adding "shorty" headers. Before I go into details, let me say out front that I did not expect great gains. Single digits at best, I just didn't want LuLu to lose any power. She didn't. So, starting at the top...

 

Rationale for change:

First...Any gasoline engine is nothing more than a big air pump, a compressor. Second...I thought about our SGT mods from SAI and FRP, asking myself a question. "If we have 90mm MAFs and low restriction fresh air kits, this equates to more air being introduced into the big pump". Third...If there's more air going in, there should be more room for air going out. Seems logical, yes?

 

Next...Not wanting to spend a lot of money on an experiment that may fail, I searched for headers based on costs, nothing more. I found these:

 

http://www.blueovalindustries.com/products.php?pid=99013292

 

Under 250.00 delivered to my door, and they are everything Pypes promises. 200.00 install labor, with a 50 buck tip to the tech at my dealership for a "job well done".

 

The install was fairly straightforward. From under the car, unbolt the engine mounts, loosen the tranny mount and jack up the engine just enough to get the mounts out. The shock tower brace did not have to be disturbed. From under the car, everything is accessible, but I have never seen any header install accomplished without a BFH. This install was no different, about a 3 hour job with the right tools.

 

Performance:

Well...LuLu got what I expected. Single digit improvement. Be advised that all numbers are 3 pulls totaled and averaged.

 

My base "bone stock" dyno produced 275.5 RWHP, 302.1 RWTQ

 

Post header install dyno produced 284.54 RWHP, 306.80 RWTQ

 

AFR unchanged, it nose-dives to 12.0 above 3000 RPM through 6200 RPM.

 

Not stellar gains, gents, I know. But, I wasn't shopping for stellar as promised by the big name header companies. I wanted "dirt cheap" first. Not only the did the aforementioned dyno numbers improve, I discovered a remarkable improvement in MPG.

 

Prior to the headers, my city MPG was 18-19 MPG and my highway was 22-23 MPG. After adding just the headers (no tuning) my MPG moved up to 22-23 MPG city, and a whopping 27-29 highway! This MPG gain was tested over 2 days, and over 300 miles of city and highway driving. At more than 4 bucks a gallon around here, I'll take it.

 

Well, here's the starting gate, gents. For about 500 bucks, you can gain a tad more power and some fuel efficiency. It's not a bad deal, and I like the "seat-of-my-pants" tickle too.

 

BTW...In the opinion of my dyno dude, Corey Simpson/Simpson Performance, my "muffler delete" mod had no effect on LuLu's performance gain.

 

Happy motoring, gents!

[68fastback]

I took LuLu out to the dyno today, to see what develops after adding "shorty" headers. Before I go into details, let me say out front that I did not expect great gains. Single digits at best, I just didn't want LuLu to lose any power. She didn't. So, starting at the top...

 

Rationale for change:

First...Any gasoline engine is nothing more than a big air pump, a compressor. Second...I thought about our SGT mods from SAI and FRP, asking myself a question. "If we have 90mm MAFs and low restriction fresh air kits, this equates to more air being introduced into the big pump". Third...If there's more air going in, there should be more room for air going out. Seems logical, yes?

 

Next...Not wanting to spend a lot of money on an experiment that may fail, I searched for headers based on costs, nothing more. I found these:

 

http://www.blueovalindustries.com/products.php?pid=99013292

 

Under 250.00 delivered to my door, and they are everything Pypes promises. 200.00 install labor, with a 50 buck tip to the tech at my dealership for a "job well done".

 

The install was fairly straightforward. From under the car, unbolt the engine mounts, loosen the tranny mount and jack up the engine just enough to get the mounts out. The shock tower brace did not have to be disturbed. From under the car, everything is accessible, but I have never seen any header install accomplished without a BFH. This install was no different, about a 3 hour job with the right tools.

 

Performance:

Well...LuLu got what I expected. Single digit improvement.

 

My base "bone stock" dyno produced 275.5 RWHP, 302.1 RWTQ

 

Post header install dyno produced 284.54 RWHP, 306.80 RWTQ

 

AFR unchanged, it nose-dives to 12.0 above 3000 RPM through 6200 RPM.

 

Not stellar gains, gents, I know. But, I wasn't shopping for stellar as promised by the big name header companies. I wanted "dirt cheap" first. Not only the did the aforementioned dyno numbers improve, I discovered a remarkable improvement in MPG.

 

Prior to the headers, my city MPG was 18-19 MPG and my highway was 22-23 MPG. After adding just the headers (no tuning) my MPG moved up to 22-23 MPG city, and a whopping 27-29 highway! This MPG gain was tested over 2 days, and over 300 miles of city and highway driving. At more than 4 bucks a gallon around here, I'll take it.

 

Well, here's the starting gate, gents. For about 500 bucks, you can gain a tad more power and some fuel efficiency. It's not a bad deal, and I like the "seat-of-my-pants" tickle too.

 

BTW...In the opinion of my dyno dude, Corey Simpson/Simpson Performance, my "muffler delete" mod had no effect on LuLu's performance gain.

 

Happy motoring, gents!

 

That's great results: nice pop in power and great milage improvement. Would it be possible to post the before/after dyno charts showing A/Fs? At WOT different tables are used that may/may-not show the milage difference but it's very interesting anyway. It would seem that at cruise (closed-loop) you're running much leaner but not clear why the ECU seems to not be retargetting the programmed A/Fs according to it's closed-loop tables. I assume there was no tweaking of the tune. The Shelby GT seems to run rich in stock form, so maybe this is just what she wanted

 

Dan

[69dejavue]

LuLu, would you expect even slightly more with equal length headers? What is the sound like in the car with straight pipes. Is there a constant drone while driving, while cruising?

[RogerS]

Nice results Mac.

 

Hey how about a pic and review of your mirrors?

 

Roger

[shelbytexan]

not to bad lulu.i've heard 10to12 hp from shorty's and you got 9hp so that's about right.these manufacturers all seem to boast a little to sell their product.these guys also say if you supercharge you will double your hp out of headers but another ? mark.i am really impressed with your gas mileage more than h.p.can you really feel a difference in your power with the extra horses.i'm contemplating headers myself.also contemplating a one piece aluminum driveshaft.my wife agreed if i pay my car off in july that i can use my excess money in october for a supercharger.don't know what direction i'm going yet.i would prefer my scoop problems be corrected before i spend anymore money on car.of course if i get a new supercharger in october then my wife wants a new ring in january.so much for a second job.glad you are happy with your new mod.

[mikewheels]

I have that same set of headers along with a Magnaflow catted x-pipe sitting in the garage right now. I also bought locking header bolts. I was thinking of installing them Wed. Thanks for posting the install tips. Saved me some grief as I'm doing it on my back. I've all ready installed Ford racing stinger axle-backs. Hopefully I'll get similar results in power and mpg increase.

[ilmor]

Thanks, that is good useful information. It also seems like a very good deal, comparing dollars to power. I really need to get those because my SGT is getting 27 to 28 mpg already on the highway; maybe I could hit over 30 mpg!

[69dejavue]

LuLu, did Corey lean the engine or is all of the increased miles per gallon just from the headers and straight pipes?

[LuLu]

Gents...I'll try to answer everyone's concerns, but I may miss one or two thoughts.

 

There was no tuning involved here. Simply bolted the shortys in place, leaving the original SAI/FRP tune unmolested. Corey said he could pull more power from LuLu if I would let him tune it, and I decided to wait for another time. Wouldn't be a fair "before" and "after" comparasion if I added a tune.

 

I cannot post dyno reports. My computer is much too old and slow, and it times out when I try to upload pics and things. However, I can say that at 3000 RPM, the AFR drops to 12.0 and stays flat through 6200 RPM. It is like this in the "before" and "after" reports and I credit the SAI/FRP programming plan. Hope this helps.

 

I installed the turn signal mirrors as a safety feature. IMHO, our front signals are too low in the facia to be seen clearly, and the mirrors were my answer. The lens wraps around to the side of the mirror, so, drivers next to me will also see my signal, but I do not see anything from inside the car and I sometimes forget they are present. If you feel as I do about the front signals, this may be your answer.

 

http://www.blueovalindustries.com/products.php?pid=99013190

 

The "muffler delete" mod does not have anything to do with improved MPG. This mod has been in place for several weeks with no remarkable change in MPG. If at all, my MPG dropped because I love scooting around the neighborhood terrorizing anything with a fart pipe.

 

Discussing exhaust sound in this medium can be confusing and misleading. What I enjoy may be a nusiance to you. That said, the "muffler delete" mod does not cause any howl, moan, groan etc., at any speed that I have noticed. Crusing at any speed with a light throttle produces a very pleasing mellow tone that seems not as loud as the factory mufflers. There are some added gurgles and pops on decelleration, very old school. However, under WOT...OMG! Folks will know you're coming, I've caused pedesterians to step back on the curb. Please note that if you attempt this mod, the exhaust tips need to be extended past the rear facia. Otherwise, exhaust vibration will telegraph back into the passenger compartment with unpleasant results.

 

Happy motoring, gents.

[clark17357]

Please note that if you attempt this mod, the exhaust tips need to be extended past the rear facia. Otherwise, exhaust vibration will telegraph back into the passenger compartment with unpleasant results.

 

Happy motoring, gents.

Hi Mac,

 

Do you have any photos of your exhaust tips with your present set up? Terlingua is too far away to wait to see it in person. Jim

[LuLu]

Check your e-mail, Jim.

[stump_breaker]

Hmmmm, minimal gains for the time and money spent. That answers my question on headers although with tune, headers and the Steeda Elbow we might hit the 350 engine HP mark on the SGT pretty easily.

 

It's amazing what we will do/spend to gain the power equivelancy of a good push mower.

 

So what tune will you be using eventually? Custom? Shelf?

[LuLu]

Hmmmm, minimal gains for the time and money spent. That answers my question on headers although with tune, headers and the Steeda Elbow we might hit the 350 engine HP mark on the SGT pretty easily.

 

It's amazing what we will do/spend to gain the power equivelancy of a good push mower.

 

So what tune will you be using eventually? Custom? Shelf?

What did you spend on 4:10s and the Hypertech tuner? What did you get for your money?

 

Yes, I got minimal gains, but I didn't expect anything different. There was a possibility of losing power too, these 281 CID engines can be very sensitive to a loss of exhaust system back pressure. As it turned out, my RWTQ improvement is very minor, but I can fix that with a custom tune.

 

My intent was to show what improvements can be had from hardware alone, and hopefully this will help others make an informed decision about their mod program. Anyone contemplating headers and exhaust mods should install the hardware first and see what gains were obtained on hardware alone, and then tune it. You'll get more for your money. If you tune first, and then add more hardware, you still may lose power and I don't imagine a re-tune will be free.

 

I'm happy with LuLu the way she runs today, and if I put a tune on her down the road, it will be a professional tune from Corey Simpson. I don't have much respect for canned tunes, seems they are always missing something. It might be a tad more expensive for a custom tune on a dyno, but you won't have to go back and do it again because a bench tuner in Califormia or Florida doesn't understand your local climate.

[stump_breaker]

What did you spend on 4:10s and the Hypertech tuner? What did you get for your money?

 

Yes, I got minimal gains, but I didn't expect anything different. There was a possibility of losing power too, these 281 CID engines can be very sensitive to a loss of exhaust system back pressure. As it turned out, my RWTQ improvement is very minor, but I can fix that with a custom tune.

 

My intent was to show what improvements can be had from hardware alone, and hopefully this will help others make an informed decision about their mod program. Anyone contemplating headers and exhaust mods should install the hardware first and see what gains were obtained on hardware alone, and then tune it. You'll get more for your money. If you tune first, and then add more hardware, you still may lose power and I don't imagine a re-tune will be free.

 

I'm happy with LuLu the way she runs today, and if I put a tune on her down the road, it will be a professional tune from Corey Simpson. I don't have much respect for canned tunes, seems they are always missing something. It might be a tad more expensive for a custom tune on a dyno, but you won't have to go back and do it again because a bench tuner in Califormia or Florida doesn't understand your local climate.

Sucks when someone belittles yours work, huh? I'm a bit surprised you got so defensive. It was ok to hammer me on my post but hey, whatever. I'm done. Got my point across obviously...

 

The 4:10's were never installed for HP/TQ gains only to better utilize the power the car already produces. You should know that. I gained a lot of drive-ability as well as fuel mileage increases - especially in town - with the 4:10's and it was well worth the money. I'm hitting 20-21 in town and 26 highway at highway speeds.

The Hypertech was never meant to do anything but change the gear ratio in the computer. The tune that came with it was an added bonus. I have also NEVER said I had a good or aggressive tune in fact I called it vanilla from the start. Now I have said it is better than the stock SGT tune. Your stock numbers compared to my tuned numbers show that, more-so in the HP range.

Regardless, there is no comparison between our mods because it's apples to oranges and I'm not going to get into a peeing contest. You're happy and I'm happy.

You want to know what I spent? Between $1100-$1200 for everything including the camber bolts and alignment so that would put the gears and tuner between $800-$900. Pretty respectable. I don't know exactly because I don't have the receipt in front of me and my wife bought some doo-dads on the same bill. QP also took care of new stripes and a fixed scoop which still looks good today.

[LuLu]

Sucks when someone belittles yours work, huh? I'm a bit surprised you got so defensive. It was ok to hammer me on my post but hey, whatever. I'm done. Got my point across obviously...

Belittled? Defensive?

 

Umm...No X2. I was wondering what you spent for your performance, and the question I asked you here, I asked because the financial 411 should be figured in when folks are trying to decide what to do next. Every mod has a "bang for the buck" and if we don't talk about the bucks, we're not helping each other. Obviously, you don't agree, but every question is not an attack, K?

 

The 4:10's were never installed for HP/TQ gains only to better utilize the power the car already produces. You should know that. I gained a lot of drive-ability as well as fuel mileage increases - especially in town - with the 4:10's and it was well worth the money. I'm hitting 20-21 in town and 26 highway at highway speeds.

MPG gain from 4:10s...IMHO, this is important 411, wish you had shared it with us.

 

The Hypertech was never meant to do anything but change the gear ratio in the computer. The tune that came with it was an added bonus. I have also NEVER said I had a good or aggressive tune in fact I called it vanilla from the start. Now I have said it is better than the stock SGT tune. Your stock numbers compared to my tuned numbers show that, more-so in the HP range.

Regardless, there is no comparison between our mods because it's apples to oranges and I'm not going to get into a peeing contest. You're happy and I'm happy.

You want to know what I spent? Between $1100-$1200 for everything including the camber bolts and alignment so that would put the gears and tuner between $800-$900. Pretty respectable. I don't know exactly because I don't have the receipt in front of me and my wife bought some doo-dads on the same bill. QP also took care of new stripes and a fixed scoop which still looks good today.

More good 411 on mods, thanks for describing your experience.

 

Yep, you got more power than I did, but beating your numbers isn't (wasn't) my intent. Like you said, our approaches to building power are from two opposite perspectives, and I think it's good to flush both out completely. "What did you get, and what did you spend". But, in the end we're close, yes? And close gives others something to chew on while considering their options.

 

I know you read this post, you replied to it.

 

http://www.teamshelby.com/forums/index.php?showtopic=28530

 

Here's an SGT owner asking "what do I do?". Is it not our responsibility to reply? You thought so...Bravo!

 

Feel free to pee on me anytime my friend, just add more "color" detail? Your post could be important 411 to someone else here who's caught in a 411 cloud.

 

That's the funny thing about "experience". Half of it, is getting it. The other half is sharing it.

 

Be safe.

[avidShelby]

I gained a lot of drive-ability as well as fuel mileage increases - especially in town - with the 4:10's and it was well worth the money. I'm hitting 20-21 in town and 26 highway at highway speeds.

 

I've been thinking about adding 4:10's but I was afraid they would cause my MPG to go down across the board. However, your experience appears to disprove my theory, how's that work?

 

I'm not trying to add to Operation GOLDEN FLOW, just trying to figure out if I should go with the gears...

[stump_breaker]

I've been thinking about adding 4:10's but I was afraid they would cause my MPG to go down across the board. However, your experience appears to disprove my theory, how's that work?

 

Pretty simple in theory. The gears not only allow the car to do more work with the energy it produces it also puts the car closer to it's "sweet spot" slightly raising the rpm's of the engine, making more power and struggling less.

City mileage increase should be obvious since it's not "lugging" the engine everytime you take off but highway is there because of the OD gear. If it were still 1:1 like old cars, you would loose mileage but since car manufacturers use high OD gears, the 4:10's just increase your final drive gear ratio.

It's like going up hill on a ten speed. You work really hard wearinging yourself out until you swithch to lower gears and then it's like butter.

 

Pro: Increase in mileage

Pro: The car feels like you added 50 horses under the hood

 

 

Con: you lose top end but I don't want to drive 140mph everywhere I go.

Con: You increase the rotational speed of the driveshaft - the speed at which the shaft will explode. Being a two piece shaft the critical speed is very high in comparison to a 1 piece so I'm not as concerned. I had a Dodge shaft explode at 85 mph from hitting critical speed after a gear swap. Dodge shafts are a coke can wrapped around a cardboard tube tough so there is no comparison.

Con: You may not get that mileage improvements stated above because it's so much more fun when you plant the right foot firmly.

 

This is my experience and your results may vary. If you want another opinion on 4:10's talk to mywickedshelby. He had them done recently and loves them as well.

 

Sorry Mac, not trying to hijack your thread.

[LuLu]

Sorry Mac, not trying to hijack your thread.

Not a problem, my friend. Share the 411.

 

I don't know where I am at with a gear change just yet. I've considered it, but I have concerns for it's affect on tranny ratios. Still thinking it out.

 

Any discussions of gear changes, driveshafts, etc. is what we need more of.

[ilmor]

I had a '97 M3 with 4:10 gears, and that's the one thing that always annoyed me about the car - the high rpm sound / noise during highway cruise. This is why I would be reluctant to do it on my SGT.

[fatboy]

Sucks when someone belittles yours work, huh? I'm a bit surprised you got so defensive. It was ok to hammer me on my post but hey, whatever. I'm done. Got my point across obviously...

 

The 4:10's were never installed for HP/TQ gains only to better utilize the power the car already produces. You should know that. I gained a lot of drive-ability as well as fuel mileage increases - especially in town - with the 4:10's and it was well worth the money. I'm hitting 20-21 in town and 26 highway at highway speeds.

The Hypertech was never meant to do anything but change the gear ratio in the computer. The tune that came with it was an added bonus. I have also NEVER said I had a good or aggressive tune in fact I called it vanilla from the start. Now I have said it is better than the stock SGT tune. Your stock numbers compared to my tuned numbers show that, more-so in the HP range.

Regardless, there is no comparison between our mods because it's apples to oranges and I'm not going to get into a peeing contest. You're happy and I'm happy.

You want to know what I spent? Between $1100-$1200 for everything including the camber bolts and alignment so that would put the gears and tuner between $800-$900. Pretty respectable. I don't know exactly because I don't have the receipt in front of me and my wife bought some doo-dads on the same bill. QP also took care of new stripes and a fixed scoop which still looks good today.

i always thought the 4:10's gear ratio would make it less fuel effecient than the 3:55's the SGT's came with.

i'm confused. :blink: wouldnt the 4:10's make the engine run at a higher RPM?

[shel-b001]

I would think so.

[stump_breaker]

i always thought the 4:10's gear ratio would make it less fuel effecient than the 3:55's the SGT's came with.

i'm confused. :blink: wouldnt the 4:10's make the engine run at a higher RPM?

It increased my cruising RPM's by about 300. 70 mph in 5th = 2500 rpm's

[tcrockstar]

LULU, thanks for the info. I have been building hot rods for over 20 years. To get 10 hsp with out a tune and for that money is great. Even with a big block chevy changing from manifolds to headers you cannot get those gains without jetting. So good work and keep us informed.

[avidShelby]

Stump, thanks for the explaination. Still not sure what I'm going to do...

[TClark1976]

Great information Mac!

 

I'm most impressed with the gain in MPG! Gain in performance, slight increase in smile factor "seat of pants" and a gain in MPG, how can you go wrong with that?!?

 

So my question is this. Can you add headers to your SGT now and then send it in later to one of the Mod Shops for supercharger. . . or should a person hold off on adding the headers until after the supercharger is installed/tuned? Installed at same time as supercharger??

 

I don't want to run into installing headers now, calling later to find out that before Quantum or SAI can work on my SGT I have to remove the headers.

 

Thanks again!

 

Trevor

[LuLu]

So my question is this. Can you add headers to your SGT now and then send it in later to one of the Mod Shops for supercharger. . . or should a person hold off on adding the headers until after the supercharger is installed/tuned? Installed at same time as supercharger??

 

I don't want to run into installing headers now, calling later to find out that before Quantum or SAI can work on my SGT I have to remove the headers.

If you install headers now, you may be banging your head afterall.

 

Not long ago, I got an e-mail from SAI introducing a new employee, Donnie Beeson. He covered this topic directly, here is a clip from the e-mail...

 

"2. If you have added performance modifications to your car, you MUST remove them before we can work on your car, For example, if you have headers, we cannot add our performance package for it would be in violation of EPA rules..and we would be subject to sever penalties. So NO supercharger IF YOU HAVE headers or have modified your exhaust or intake.

 

3. If you have aftermarket rear control arms, the brake ducts WILL NOT fit properly and we therefore cannot install them. You can either put your stock arms back on before we receive your car, or we will put your brake ducts in the trunk and you can have them put on after you receive the car."

 

Also...

 

"There is good reason why we must strictly adhere to #2 and #3. First, we must maintain a legal operation and not deviate from California Air Resource Board (CARB) and our commitment that our cars comply too. In addition, Shelby cannot disturb any parts that are not outside our process of upfitting your vehicle to a 40th Anniversary or Super Snake. Nor can we modify in any way a part that you have installed outside the factor build. I believe the reasoning for these lines in the

sand are obvious. Yes, we do modify vehicles. No, we cannot just do whatever we or our customers want. Yes, there are limits we must adhere to in order to protect you the consumer and us as Shelby Automobiles Inc. Enough said."

 

I suggest you inquire with SAI/Don Beeson for clarity before you install any mods if your intent is to have SAI upgrade your Shelby. I have no such intent at this time, but I have all my stock parts on hand in the event I change my mind.

 

Happy motoring, gents.

[motorjock205]

If you install headers now, you may be banging your head afterall.

 

Not long ago, I got an e-mail from SAI introducing a new employee, Donnie Beeson. He covered this topic directly, here is a clip from the e-mail...

 

"2. If you have added performance modifications to your car, you MUST remove them before we can work on your car, For example, if you have headers, we cannot add our performance package for it would be in violation of EPA rules..and we would be subject to sever penalties. So NO supercharger IF YOU HAVE headers or have modified your exhaust or intake.

 

3. If you have aftermarket rear control arms, the brake ducts WILL NOT fit properly and we therefore cannot install them. You can either put your stock arms back on before we receive your car, or we will put your brake ducts in the trunk and you can have them put on after you receive the car."

 

Also...

 

"There is good reason why we must strictly adhere to #2 and #3. First, we must maintain a legal operation and not deviate from California Air Resource Board (CARB) and our commitment that our cars comply too. In addition, Shelby cannot disturb any parts that are not outside our process of upfitting your vehicle to a 40th Anniversary or Super Snake. Nor can we modify in any way a part that you have installed outside the factor build. I believe the reasoning for these lines in the

sand are obvious. Yes, we do modify vehicles. No, we cannot just do whatever we or our customers want. Yes, there are limits we must adhere to in order to protect you the consumer and us as Shelby Automobiles Inc. Enough said."

 

I suggest you inquire with SAI/Don Beeson for clarity before you install any mods if your intent is to have SAI upgrade your Shelby. I have no such intent at this time, but I have all my stock parts on hand in the event I change my mind.

 

Happy motoring, gents.

 

GREAT information LuLu! Thanks for sharing with us that are planning mods in the future...it'll save us some headaches in the long run for sure! I'm wondering if they consider the Steeda Intake Elbow a modification to the intake...I'd almost bet that they do, so you'd have to put your old original elbow on to get anything done...

[ilmor]

i always thought the 4:10's gear ratio would make it less fuel effecient than the 3:55's the SGT's came with.

i'm confused. :blink: wouldnt the 4:10's make the engine run at a higher RPM?

 

I think the 4:10's will result in less MPG. I don't see any manufacturer's changing gears to 4:10's to increase MPG; if anything, they're going in the other direction. I am getting 27 - 28 mpg on the highway w/ the 3:55's.

[CH53Driver]

I think the 4:10's will result in less MPG. I don't see any manufacturer's changing gears to 4:10's to increase MPG; if anything, they're going in the other direction. I am getting 27 - 28 mpg on the highway w/ the 3:55's.

 

Yes, that was my understanding too. 3.31's in the GT500, if 4.10's were better for MPG then wouldn't Ford be putting those in the car? I understand the bicycle analogy, but I think maybe it was backwards? With the lower gears the car is getting to the higher RPM's quicker meaning that the engine is getting into the power band faster...i.e. the engine is working harder quicker. With the taller gears such as the 3.31's you can keep the RPM's down for normal shifting/driving and keep the engine from sucking fuel at a faster rate because you aren't working the engine as hard. Isn't this correct?

[stump_breaker]

You guys can believe what you want about gears. I'm not selling anything or have stock anywhere (Except CSBI so buy a lot from them! :happy feet: ) I'm just trying to help you understand.

Try reading this article to see if it helps. You have to get the "lower gears kill mileage" thoughts out of your head and be more open minded. Long gone are the days of 1:1 final ratios which did kill mileage because it resulted in excess engine speed. I have always tried to shoot for a 2.75-2.90 final drive ratio on my vehicles. The article above calls a 2.87 final drive ratio "fuel friendly" and from my experience I can concur. Currently my car is at a final drive ratio of 2.79 with the 4.10's up from the 2.41 from the 3.55's. A GT500 is a different monster because of the forced induction. On a N/A car I like a higher ratio but on a S/C'd car, I don't know. I do know a 500 final ratio is 2.09 with the 3.31's. With 4.10's it would be 2.58. 500's have 2 OD gears where the SGT has one.

Here's you a list:

 

GT500... with 3.31's...... 4.10's

 

1st 2.97... 9.83... 12.18

2nd 1.78... 5.89... 7.30

3rd 1.30... 4.30... 5.33

4th 1.0... 3.31... 4.10

5th .80... 2.65... 3.28

6th .63... 2.09... 2.58

 

SGT

1st 3.34... 11.86... 13.70

2nd 2.00... 7.1... 8.2

3rd 1.32... 4.69... 5.41

4th 1.00... 3.55... 4.10

5th .68... 2.41... 2.79

 

IMO just from the numbers I would think a GT500 would result in better highway mileage from a gear swap but with 425 horses (don't know the TQ) going to the ground with a 12.18 1st gear ratio, I think you would probably just sit and spin the tires for awhile. I can only speak for my SGT that the gears are a drastic improvement. I can not speak for others or other types of cars. When my "just put gas in it and drive it" wife is impressed by the gear swap, obviously it's a good improvement.

 

I do know there was a GT500 owner on here wanting to trade his 4:10 axle with a stock geared axle. He would have greater insight than anyone on 4:10's in a GT500.

 

This is just based on my experiences only. Hope this helps.