tom94RX-7

iTrader: (5)

I have a 5 speed with the 4.10s. Anybody install the 4.30 gears and then go to the drag strip and how much lower was your times? trap speed higher too?

Or anyone have an estimate on how much they could lower your ETs?

I have 24.9" Hoosier drag radials. I'm down to 11.28 @ 122.3 (19psi) and would love to get a 10.9x, without spending thousands on a single turbo, etc. I'm guessing I am at about 400 hp. I can't remember exactly but I think my rpms are at about 7k at the end of the track, so I should be good to keep it in 4th gear if the trap speeds increased a little with the 4.30 gears.

Best 60' times are 1.58 and 1.59.

So I'm wondering how much the lower gears would help. It's still a street car (although not driven very often) so I don't think I would want any gears lower than 4.3 or 4.33

Please let me know if anyone has any experiences at the track with gear changes, or an estimate. Thanks!

braindead

4.30 gears are not going to be a HUGE change from the current gears but you got to remember that with a boosted car the longer its in the powerband the better your times are going to be for instance with my cobra before it was boosted i had 4.56 rearend and with et slicks and only around 370hp it would lift the front end on a decent launch, but after i boosted it with the 4.56 gears when i came into the powerband since it was so short the tires would just break loose and i was geting slower times. after i swaped the 4.56 for the 3.73 and a few other little adjustments i knocked off over a full second on my time...looks like your 60ft and et is GREAT for your power lvl but i think you might of kinda hit a brick wall, seems like you have maxed out the potential of your stock twins. just my openion but if your really looking for a noticable diffrence in your times your next option would be a porting job or turbo swap

grimple1

iTrader: (1)

yeah i was gonna say i bet it's probably not gonna lower your 1/4 mile time. what you're gonna gain in 60 ft time you'll loose in trap speed.

tom94RX-7

iTrader: (5)

Thank you guys for your thoughts and opinions. I forgot to mention my experience with different size drag radials which closely relates to gearing. The first set of drag radials I tried was MT ET street radials, 26x10.5x16. When I put these on, my car got slower!, because the tires are an inch taller than the factory size, we all know that larger rear tires generally make your car slower right. I was getting similar ETs (only because I was able to get better traction, launches and 60ft times) and my trap speeds were much slower because the taller tire changed the gearing to equal 3.70s, my trap speeds were like 5mph slower than what I was doing with my 265/35-18 street tires, not to mention the 18" rims are much heavier than the sotck 16s. So I had to get rid of the 26" tires, so I got the 24.9" 225/50-16 hoosiers which were also not as wide as the 26" MTs, and my trap speeds were back up to what they used to be. I also started getting better 60ft times with the smaller tires even though they were not as wide, because they made the gearing lower, and get good traction.

So if I got the 4.30 gears, I'm thinking my car will be able to accelerate faster in 3rd and especially 4th gear, I will be able to rev out 4th gear longer, so I think they could improve my trap speeds which would improve my ETs, just like the smaller tires compared to the 26" tires.

If I get the 4.30s, and need more traction, then I could just get the 26" tires again which are wider and could provide better traction with more hp in the future. 26" tires and 4.30 gears is basically the same gearing as stock with stock size tires.

Anyone agree with me? or have any experiences with the gearing? thanks.

matty

kudos to u my friend for pushing the stock turbos. bunch of pussies on this forum....anyways....

quick question for you....i been running 15psi for 5 yrs now. for some reason when i turn up to boost on my power fc the car doesnt make anymore boost. even when the car had only 20k miles on it it wouldnt make more then 15psi so point is i doubt the reason is because something is tired. any idea why?

tom94RX-7

iTrader: (5)

I had a similar problem just this past week, i thought I couldn't make more than 17-18 psi anymore, but then realized I had forgot how to correctly turn up the boost on my profec b spec-2 boost controller, all year I was doing it wrong trying to turn up the boost and they wouldn't boost anymore, over the winter I forgot how to do it right. So make sure you are doing it correctly, I read the manual and realized I was turning up the start boost (set gain) instead. So mine will make at least 20, I hit 20 max psi my last pass down the track, but I spun like crazy in 2nd gear and still ran 11.37, it was cold out and I'm hoping the track lost traction because of how cold it was, and not because I turned up the boost alittle.

Maybe the PowerFC doesn't control the boost well enough up that high, I don't know since I set it very high in the PFC and use the greddy boost controller. Maybe Try using a manual or better electronic boost controller. I would guess your turbos will boost more if your car is pulling hard at 15psi, mine pulls hard at 20, stock turbos and engine with 105k miles.

By the way I'm still using the stock map sensor and was not leaning out, I was closely watching my PLX wideband going down the track at 19-20 psi, 11.1-11.4 afr, so don't be afraid at your boost level with the stock map sensor. I am going to order a plug-n-play apexi 3 bar map sensor tonight, then I could see just how much these stock turbos will boost lol.

matty

thanks for reply......do u recall what ur settings are in power fc?

tom94RX-7

iTrader: (5)

Ya, they are set way above what the PFC commander shows as the max boost after a run, I could check to tell you exactly, but I think they are at like 1.4 . The PFC doesn't do anything to control the boost because I have it set so high that way it will never do a fuel cut out if the boost goes above those settings, the greddy controller handles all the controlling.

RTS3GEN

Tom,
Well I will tell you I was running 4.10 gears and could only muster 12.2's at 113mph on my car at 14psi with 26 X9.5X16 ET streets at 18psi(air pressure in slicks), I installed the 4.30's and ran an 11.99 at 115mph at 12psi(boost). I wanted to be sure I didn't break anything so I ran lower boost. I turned the boost up to 15.6psi(1.1kg/Cm2) and ran 11.77 at 117mph. My 60' time was 1.75. I ran another run at the same settings but broke when I shifted into 3rd gear, ran a 1.72 60'. I blew the output shaft on the tranny so I was done for the day. I now have 4.77 gears but haven't been to the strip in 4 years, I got tired of replacing the damn transmission and axles!
Art

tom94RX-7

iTrader: (5)

Now that's more like I expected to hear from someone who has done the gear change. I'm sure you ran better because those 26" tires slowed you down, and the 4.30s put you back to stock gearing, I had a similar experience with tire changes. I was thinking my ETs could get a little better just like yours did with lower gearing.

Why did you put in the 4.77s? And does the car feel quicker with those and do you think it would probably produce a better time at the track? I'm also curious why you keep braking the tranny and axles, do they brake when you get wheel hop after switching into the next gear?

Thanks!

RTS3GEN

I think the main cause of my driveline failures was the unsprung clutch disc I was running. I have been running a sprung Clutch/Net disc for 2 or 3 years with 6 pucks of cintered bronze and it grabs very well but doesn't shock like the unsprung disc. I never had a problem with wheel hop with the ET streets, only street tires. I broke whenever I had the ET streets and could generate a few pounds of boost off the line. One time I broke both axles simultaneously! That was fun....Not. I put the 4.77 in because the 4.30 was just a little too tall for using 5th gear on the track(I road course alot!) and several tracks have long enough straights where I was running out of 4th gear but there wasn't enough usable torque in 5th gear to continue accelerating to the braking zone, so Cam at Pettit convinced me to put the 4.77 in. This makes 5th gear a usable gear. I can honestly say that I definitely felt the difference from 4.3 to 4.77. I didn't notice going from 4.10 to 4.3. If you put a 4.77 in you'd easily be in the 10's, and if you are mostly dragging the car this is what I would recommend! 11.28 is F'ing flying dude, are you still on the stock axles and diff? Surely not.
Art

tom94RX-7

iTrader: (5)

Thanks for all the info. Yes I am on stock everything! (engine, tranny, axles, diff.) I did get the parts from a launch kit, like the suspension pieces and solid diff. mounts.

I just ordered a banzai racing diff. brace to keep my stock stuff lasting even longer.

I never get wheel hop on launches, I don't drop the clutch either. I don't do anything stupid on the street to wheel hop. I may launch at 6-8k rpms, but it doesn't feel bad on anything. Sometimes it hops briefly or spins a little after I shift into 2nd gear, that's it.

I'm definately thinking about them 4.77 gears and maybe bigger tires for more traction in 2nd gear. I love the part where you said "you'd easily be in the 10's", that's my goal right now. thanks again.

smg944

iTrader: (34)

that is fast for the stock twins. nice job

RTS3GEN

That's even more impressive with stock axles! I have a Gotham diff brace that I had installed but removed because of the horrific vibration I get from the drivetrain on the roadcourse! If you're heating the slicks up I wouldn't think you'd need bigger tires, I'd go with the 4.77's (although they are about $250 more than the 4.30) and try them without changing anything else. You obviously know how to launch, shift and put down the power. I truly believe that you'd be well into 10's with just the gears! Nice job though dude, that's a true testimony to the actual robustness of these cars that so often get a bad rap for being unreliable and no good for drag racing. Bwah ha ha! Rock on!!!! Keep me posted on your decision and your progress.
Art

tom94RX-7

iTrader: (5)

I was thinking I might need bigger/wider tires, but only because I was spinning for like 2 seconds after switching into 2nd gear my last 2 runs at the track. It was a cold night, and getting a lot colder by that 3rd and 4th run, and I turned up the boost a small amount. So I think I might have just lost traction because of how cold it was, hopefully the track just lost traction at that temp. And I still ran 11.42 and 11.37 @ 122.3 spinning the back tires for like 2 secs before I got traction in 2nd gear.

4.77s and some 26/11.5-16s sounds like a real good combo. I'm going to see how I do at the track next time after adding a few more mods (meth/h2o inj. and 99 y-pipe and removed the outer A/C belt crank pulley). And then I may get those 4.77s.

Where can the 4.77s be bought? All I see is 4.30s for sale at the most popular vendors.

Ya the car is awesome and can be setup good for some fun drag racing, and I'd say it's pretty reliable since I have done probably over 100 passes down the drag strip without braking anything with a ton of stock drivetrain parts.

Thanks for the compliments. I will definately keep everyone posted.

tom94RX-7

iTrader: (5)

I found a thread with good info about the 4.77s - https://www.rx7club.com/3rd-generation-specific-1993-2002-16/best-place-get-104243/



Read the thread for more. I'm definately going to have go with 4.77s instead of 4.30s, and 4.30s would be pointless if I ended up getting 26" drag tires.

And darn I thought I might have had the best ET on stock engine and turbos, well it looks like I could be the next in 10s!

neit_jnf

iTrader: (17)

im impressed! are you seq or non-seq? I want to push my turbos to 18~19 just for some drag races but i'm seq and I hear the primary will fail really fast at those pressures...

can you share your pfc map? I have a gm 3bar map as well as 850pri and 1300sec that I haven't installed...

tom94RX-7

iTrader: (5)

Stock Seq. Both turbos are on when leaving the line since the rpms are above 5k, so non-seq would only help if there is better airflow from doing the full non-seq mod.

My primary turbo only puts out about 15 psi, then when the 2nd turbo kicks in the boost will jump up to 19psi (if I have it set for 19) and hold there because of the boost controller. Mine has not failed fast at all, it's been putting out the same amount of boost for like 2 years now.

You definately need to get that fuel system installed and turn up the boost! Ya I will post some of the inj. map and PIM settings.

silverTRD

iTrader: (37)

wow thats pretty impressive.

RTS3GEN

Call Ari at Rotary Performance in Garland TX. I am sure they have a set, if not call Gotham, I'm sure Steve would have some in stock. As for the turbo's, I think they are very robust. I think it's lack of oil or use of dino oil that kills them. I've been running 14psi + on mine at the road course for over 8 years with no probs. My turbos have 134K miles on them and still will make 17 or 18 psi if I let them.
Art

tom94RX-7

iTrader: (5)

Thanks. I emailed them all, and Gotham can get some used 4.44s, if they are in good shape then those would be a good deal and good ratio for me I think, better than 4.30s. Or I could get the 4.77s from FDNewbie Imports. Decision time..

mdpalmer

iTrader: (24)

Just want to say that it's pretty insane what kind of straight line performance you've got from your FD Props on pushing the stock turbos.

I wonder how different it feels in day to day driving with the higher ratio rearend (acceleration wise). I'm non-sequential, so anything to improve acceleration before 3800 rpm is kindly accepted

On another note: what size and offset are your wheels in the rear? Car looks great.

And another note: more details on your tune (i.e. the PFC/datalogit maps) would be greatly appreciated

tom94RX-7

iTrader: (5)

Thanks! You would probably benefit a good bit from a gear change, someone else non-seq. said they liked the 4.30 gears. The rears are 265/35-18 Moda R6 18x9 rims, i think Offset: 40mm, not sure cause they are not sold on tirerack anymore so I can't see the specs on them.

I will be glad to post the PFC settings, try to tomorrow, I'm trying to go to bed soon. I don't use datalogit, Its not needed for me, I just tuned with my PLX R-500 wideband with laptop for datalogging, can datalog 4 sensors at once, and just the PFC commander.

SPICcnmGT

4.44s?? I need to give them a call, what did they come out of?? I wanted some lower gears to help with AutoX and tracking, but 4.30 IMO isn't worth the money, and with 4.77 I'll be running 4000rpms on the interstate. And when I read about the 4.50s I just keep wishing someone would actually make them.

tom94RX-7

iTrader: (5)

He said "There is a used 4.44 i can get my hands on but dont know the exact condition", so I don't think there is more than one set available, and I'm thinking about getting those.