I know this is a highly debated topic, but I cannot decide for the life of me. I have searched and searched and my head is spinning from all of the different opinions and theories.

setup will be, 06 g35 automatic with a built motor with cams, springs, etc to rev to 8000rpm. im staying na, want a good autox setup and a good setup for canyons. will have the occasional shot of nitrous, but that will not be very often. i know by the rpms i am turning on the highway, the car currently has the 3.54:1 gears

3.7 seems like a good option, but i dont want to spend that much for not much of an overall gearing difference. 3.9s seem ideal given the higher rev limit, but are very pricey. 4.08s might be overkill with the auto, but are not that much more aggressive than the 3.9s, but are more affordable and quite a bit cheaper than the 3.9s

what i absolutely dont want to happen is for me to spend a bit of cash on this and have the car actually be slower accelerating, even though it may feel quicker. actual times and performance are much more important to me than what i "feel" in the car.

someone tell me what to do please...

 

3.7 would be my suggestion, try them out, if you don't like they can easily be sold off.

 

why would 4.083 or 3.9 not be ideal for high reving engines(8000rpm)?

 

I've swapped to 3.5 and would swap to 4.03 immediately
If given the choice. You should too.

Are you going to upgrade vb too?

 

How do you plan on making power to 8000rpm's? I have only seen a handful of cars that do that.

You cant have a perfect gear setup for auto-x, canyons, N20, dragging, etc, everything is a compromise.

Regardless of you choosing 3.7, 3.9, 4.0, the car wont be slower accelerating unless you dont have traction.

I think 3.9+ is too high for an auto G, even with your redline to the sky its too short IMO.

Id do the 3.7 and shoot to make power to 7500rpm's. Not to be a d!ck but at the end of the day, an NA built G with an auto is slow anyways, dont fry your brain over this decision.

Plus keep in mind once the autos hit 4th, they dog the fawk out. Ive driven my friends G coupe back in the day with a Stillen, and once it hit 4th - right at the end of the 1/4, it was done. The gears will help that gear pull some, but will also put you there quicker, again all a compromise.

 

you are right, i probably wont make peak power at 8000 or up close up to that, but im guessing that i will still be making more power at 7500-8000 than i will be at 5000-5500, so it will benefit me to hold the gear longer vs shifting, so even though power will likely drop off some, it will still benefit to hold the gear. im hoping with an exhaust cutout, BC stage 2 cams, and headgames working my heads, i will be able to keep the power dropoff to a minimum.

i know about the 4th gear being a dog, but why do you say that autos are slow? im faster than almost all manuals. autos will have slightly more drivetrain loss, but that can be changed with an aftermarket tq converter, which i will likely do, plus, in the lower gears, the auto has more torque multiplication with a tq converter. and i have the transgo vb upgrade, so unless im up against a pro racecar driver, i win with shift speed.

thanks for the opinions. i think im leaning towards the 3.7, but its just not that much different than what i have. and so many people are happy with the 3.9/4.0

 

so you are in the same boat i am now with 3.5s. what makes you want the 4.08?

yes, i have the transgo vb upgrade already

 

No headers on your build?

I am well aware of why you would want to shift slightly past redline, but again I havent seen many cars make power to 8000rpm's or even warrant a shift that high outside of a 1-2 shift.

What compression are you running? Why waste $$$ on headwork when our heads flow great? IMO the better spent money would be on a better intake manifold matched to your cams/setup.

I have been in, driven and drag raced a G Coupe with VB upgrades, I can tell you it is not faster than a decent driver down a 1/4, if you think it is you havent seen a good 6Mt guy.

What do you run now since you say you are faster than most manuals?

Keep in mind you have one less gear than the 6MT guys who love the 3.9 and 4.0 gears. Thats a big disadvantage unless you like cruising 5th gear at 3400rpm's at 65mph. <-----I dont know exactly where it would put you but you get my point....

 

autos have 5 gears instead of 6 like a mt, and the 5th gear in auto isnt geared as wide as 6th is in a manual. so an auto with 4.08s will be turning higher rpms than a manual at the same speed on the highway

 

yes, headers, megan headers, megan test pipes, and larger y pipe to a cutout, and many other things. im up to about 6000$ in parts alone, but ive been over all this before, power will drop off some, but it wont drop off that much, holding the gear, whether i make peak after 7500 or not, will be benefitial.

11:1CR
i have a 5/16 spacer now, will be getting a 1/2" spacer for this engine, all intake components are gasket matched, lower non-rev have some pretty extensive work done to it, and the upper plen has been worked some too.

i dont want this to be an auto vs mt thread, i dont have any timeslip, just some legal highway runs, everything unofficial.

so far 2 votes for 3.7, and 1 for 4.08

 

Im trying to help you, but you seem to have already chosen your path (incorrectly IMO).

Good luck.

 

i appreciate the suggestions and help, but it is impossible to listen to everyone, what is wrong with what im doing, in your opinion?

 

I'm running 3.7 and am happy with it. I believe 4.0+ would be to tall for an auto, it may have an adverse effect on the car's systems. (VDC...etc)

 

^ you still selling your 3.7s?

 

I still need to take it to a mechanic to have it looked over, haven't had the time recently. It takes more force to start turning then it used to.

 

i didnt mean to scare you off, im open to suggestions, but at the same time, i want to do my own thing. if you think im making a mistake somewhere, tell me now so i can at least consider it. most people say my headers are a bad choice, but i just cant justify spending over $1000 on headers. other than that im open to suggestions. cosworth plen has shown to lose power, so staying away from that. peak power is not what im after, id prefer a wider powerband, main purpose for the car is road course and canyons. thanks for your input

 

is there fluid in it still?

 

yes

 

You are wasting money on heads IMO. You cant justify spending money on better headers, but you do heads? Megan stuff for an NA build is garbage IMO. Your priorities arent straight. Compression barely going up is doing nothing for you. You dont have a good intake manifold picked out. You are thinking of adding N20, did you think about that when you picked out the cams? Did you think how a car with a 4.0 gear will likely never hook up on street tires with even a measly 100 shot?

Cam choice is for upper rpm's not midrange or canyon use IMO. Being an auto you need something to keep the TQ up, I dunno how this cam will be in an NA application.

Making claims like "my auto is faster than most manuals" with no proof doesnt sit well on this site.

You will spend over $6000 and end up with less than 300whp, factor in being a heavier G and being an auto and you will have a low 13 second car if you're lucky with a "built" NA setup.

I dont know if you are building because you damaged the stock motor or just because you want to but all I see are mismatched, not thought out parts. You are only as strong as your weakest link.

Not being a d!ck, just trying to help.

edit-one Q, did the 06' G's have the Revup motor like 06' Z's or standard VQ? If Revup I didnt know any cams existed to be honest with you.

 

2006 6mt g's had the revup, autos had the non-revup, so i have a nonrevup.

do you have part recommendations as opposed to just saying its all garbage?

i understand the idea of getting headers instead of head work. I will consider that. my reasoning for doing what i have planned is that a local guy wants $800 to assemble the heads and do a 3 angle valve job (he does 3 angle on all assembled heads, so taking out the 3 angle would not lower the price), which might net some gain, but also might net some losses since he has not done many, if any, vq heads before. he mainly does hondas and v8s and works with a local honda tuner a lot. im not a fan of generic work jobs, so for a little bit more cost, i can send to headgames and have worked and assembled heads with bench tested flow results guaranteed since he has done many and tested the results. so not a lot of extra cost there.

ive been using nitrous for quite a while, so im not considering adding it, i added it a long time ago. but like i said, i wont be using it very often, so i removed the n2o variable when making my cam choice.

maybe i will bump the compression a tad with machining the head, but as im sure you know, the higher you go with compression, the less and less the gains are, diminishing returns. plus, when i do shoot some limited nitrous, high compression can be dangerous. obviously i would pull timing and have colder plugs, etc. but, what do you suggest for a CR?

hooking up with n2o and getting traction can be manipulated with my window switch or progressive solenoids. or maybe ill just roll on drag radials when i know ill be using nitrous.

as far as the cams, i think they will prove a good mid to upper cam, which is what i want. if i am incorrect in this, then i read some bad info. about the torque, that can be done with a torque converter and the gears i originally asked here.

dont get all bent out of shape over my auto vs manual comment, its not a big deal, dont let it make your life shorter man

i can guarantee i will have quicker than 13sec quarter miles when im done, even at the 4500ft elevation im at.

im building because my current motor is on its last leg, using oil like crazy, no compression in a cylinder, its just time.

i appreciate the help, but maybe some suggestions on what to replace these components with would be nice too. i typed out my reasoning for what you listed as issues and garbage, not because im dead set on this, but just so you can understand my thought process and why i had these plans. i always like a good discussion on what would be best, cause who wants to spend this kind of cash and be disappointed. i dont have huge expectations, i am at a high elevation, do not have the variable cam timing a revup does, but i do want to be happy with the end result.