S14 stock rear end ? RB25

[GT240R]

Is the stock rear end gears different from the stock gears of a manual car? I swaped an RB25DET into my 98 Kouki and the RPM at 70mph are at like 4,500RMP. MY gas goes very quickly, and I fill up once a week. Thanks

[MeanS14]

I have the same problem with my rb25 in my s14. You'll have to change the gear ratio if it bothers you too much

[eh?]

Your tach is off by 1.5x, you're really around 3k.

[GT240R]

^^
Actually I already calibrated it, but still run pretty high RPM and wondered what the gearing is in an auto 98 S14 compared to a manual if any difference. Also what does everybody use for gearing when swaping an RB25DET into a S14?

[g6civcx]

Is the stock rear end gears different from the stock gears of a manual car?

This question cannot be answered because I don't know what you're talking about.

Perhaps you should do some research on the rear diff and try asking again, or at least be more specific.

What is "stock rear end gears"? What is "stock gears of a manual car"?

Tell me what these things are and I'll tell you if they're different or the same.

[ANVIL]

do u have an adjustable fuel pressure regulator? what fuel pump are u using?

[drift freaq]

This question cannot be answered because I don't know what you're talking about.

Perhaps you should do some research on the rear diff and try asking again, or at least be more specific.

What is "stock rear end gears"? What is "stock gears of a manual car"?

Tell me what these things are and I'll tell you if they're different or the same.

Stock rear end gears on our Autos and manuals S14 and s13 are 4:08 . The rear end gears for a R33 GTST were 4:11 because the car was heavy enough it needed the gearing for off the line acceleration. Basically our gearing is fine for the engine.

As far as mileage goes? Its a 6 cylinder turbo engine designed in the late 80's. Its not about to deliver the kind of mileage a stock KA might unless you really keep your foot out of it. Otherwise it drinks gas get used to it. You want to go fast its going to drink gas.

On the other side the engine has enough torque to cruise out of boost relatively easily. It just means your not going to rev to much over 2200-2500 max.

[opponheimer]

calibrate tach to 3000rpm at 70mph

[s142jzkillav10]

The Q45 has 4.11 gears and is good for hwy.

[Zerolift Autolab]

I would recommend that you . . . Use the Dakota Digital calibration box, pace it with another car that you know is accurate.

[VQMaxFan]

The Q45 has 4.11 gears and is good for hwy.

4.11's are worse for highway than 4.08's

look into j30 diff or something i guess, it has like 3.9x. which would be better for highway

[drift freaq]

The Q45 has 4.11 gears and is good for hwy.

Dude, if your going to comment on gearing at least learn about it. Like Vqmaxfan said, which is true 4:11 gears are worse. Plus 4:11 gears are not good highway gears unless the transmission paired to them has a high overdrive gear.


People remember with Gearing low means numerically high and high means numerically low.
This is because a numerically high gear will get you off the line faster i.e. lowering the initial launch time i.e. quicker.
Vice versa for numerically low gears getting raising the initial launch time i.e. slower. Its way most American V8 cars came with average gears of 3:50-3:34 because they felt the engines had enough torque to launch them fair quick anyways. When they were building muscle car versions they stuck 3:70 and 3:90 gears in for crazy quick acceleration.

On the same point Honda sticks 4:32's in the Civic's to give them quick off the line acceleration to make up for the lack of torque most Honda engines have.

[GT240R]

do u have an adjustable fuel pressure regulator? what fuel pump are u using?

Yep and it's adjusted accordingly.

Stock rear end gears on our Autos and manuals S14 and s13 are 4:08 . The rear end gears for a R33 GTST were 4:11 because the car was heavy enough it needed the gearing for off the line acceleration. Basically our gearing is fine for the engine.

As far as mileage goes? Its a 6 cylinder turbo engine designed in the late 80's. Its not about to deliver the kind of mileage a stock KA might unless you really keep your foot out of it. Otherwise it drinks gas get used to it. You want to go fast its going to drink gas.

On the other side the engine has enough torque to cruise out of boost relatively easily. It just means your not going to rev to much over 2200-2500 max.

4.11's are worse for highway than 4.08's

look into j30 diff or something i guess, it has like 3.9x. which would be better for highway

Thanks, I was not worried about mileage just about the high RPM's in 5th gear. I will probably look into a J30 rear end.

[gmtech1978]

i have done a couple syko swaps and the first one i did i called gary and he walked me thru something very easy, takes a lil time but patience is a virtue. anyways remove your cluster, on the back of your tach is a black knob, a very small black knob. you can dial the tach in with this, however you need a scan tool or in my case i run aem ems, it reads true rpm, i let the car idle check what the ems says and kill the car and adjust the tach, it takes a lil trial and error, but i have been able to get all of mine within a 100 rpms which suits me, although i have got closer. no need to spend money on a dakota , imo. you can also do this with a cheap diagnostic scanner that gives data and pids, but thats over some peeps heads. ha and mileage well if your running a stocker and get 18 mpg your doing fair, again, imo

[GT240R]

i have done a couple syko swaps and the first one i did i called gary and he walked me thru something very easy, takes a lil time but patience is a virtue. anyways remove your cluster, on the back of your tach is a black knob, a very small black knob. you can dial the tach in with this, however you need a scan tool or in my case i run aem ems, it reads true rpm, i let the car idle check what the ems says and kill the car and adjust the tach, it takes a lil trial and error, but i have been able to get all of mine within a 100 rpms which suits me, although i have got closer. no need to spend money on a dakota , imo. you can also do this with a cheap diagnostic scanner that gives data and pids, but thats over some peeps heads. ha and mileage well if your running a stocker and get 18 mpg your doing fair, again, imo

Cool, I have already done that, but just wondered. I may have done it wrong. As for the milage, I was not too worried I didn't swap to save milage.LOL It's not completly stock either:

Freddy Manifold
Q45 throttle body
FMIC with 2.5" pipping
2.5" intake with cone filter
Apexi 3" max down pipe
Apexi 3" exhaust with test pipe
Greddy Profec B set at 12 psi
Nismo adjustable FPR with in line fuel guage
NGK Iridiums

[MeanS14]

At 70mph on the freeway the rpms are definitely higher than with the stock motor but its not too bad

[HYPNOTIK]

I have a 3.7 ring gear that would fix your problem. :)