how to lower rpm range Options

[eldrewado]

hello all, im new here. im looking to save more gas with my 99 gt. i was wondering if there is another differential i could use to lower my cruising rpm.
if i want more power ill leave it in 4th gear. 3000 revs at 60 mph or so seems a little high, granted its good for power.


anyone have any ideas?

[azian_advanced]

the E153 (MR2 Turbo / Solara transmission) has a slightly taller final drive ratio of 4.285 over the S54 (94-99 Celica GT) of 4.176. The difference in gear ratios will lead to an increase of 5.8 mph cruising at a steady 3000 RPM on 5th gear. (source)

although, i have no idea whether the FD gears can be swapped, but it's probably easier to just swap the entire transmission and get the appropriate drive axles to get it working.

[Special_Edy]

The easiest way would be to install wheels and tires that are a larger diameter. I went from 1800rpm to 2400 rpm @60mph on my 64 chevy truck just by switching from 265 75 r15s to 285 60 r15s. Realize that by making the rollout of the wheels larger you will also throw off your speedometer(it will show a lower speed than your actual speed) and there is no telling how it will affect your Anti-Lock Brake System if equipped(in theory it shouldnt because ABS monitors individual wheel speed but hey I'm no expert).
Also I find that smaller wheels/tires tend to make the brakes feel stronger so putting larger tires on may decrease the efficiency of your brakes somewhat.
But its sooo much easier to swap tires/wheels than transaxles and differential gears.

Another mod to consider would be moving your camshafts one notch retarded on the timing belt(you need to pull the passengerside motor mount, remove the timing belt cover and make sure the Camshaft sprocket for the timing belt is one notch behind or slower than the crankshaft.) Retarding the camshafts one notch(maybe 5 degrees) will significantly improve low end performance and torque while decreasing power output at higher RPMs

[kurt95gt]

Im planning on swapping my 5th gear with one from a s51 trans from an older model camry
it swaps right in an will drop high way speeds (65) beliw 3000rpm
Down to like 27-2800

[stephen_lee]

easiset and most reversable option is as said before is go to a larger tire size. 205/60/15 would be cheaper and give you a higher speed per rpm, but checkl your actual highway speed with a gps so make corrections

[Special_Edy]

Im sure you could either buy or fabricate an adapter for the vehicle speed sensor(located on top of the rear of the manual trans. above the axle shafts). All you would need to do is alter the frequency that the speed sensor pulses.
Im sure some of the guys on the forums have the electrical experience to tell you how to design something like this.
All that said, its much more feasible to throw some 16 or 17 inch wheels with some larger diameter tires and buy/make a speed sensor adapter than try to swap transmission or final drive gears. Plus it would look good on a 6gc to have a little extra meat in the wheel well

[eldrewado]

thanks for everyone's replys, they were all good ideas.
i just got new (expensive) tires so ill be sticking with what ive got on that for now.
plus i don't want to diminish my braking capacity at all since i tend to have accidents.

i liked the ideas of retarding my timing and swapping the 5th gear from the older camry.
is there anything else i should know about in order to do these things?

[Special_Edy]

thanks for everyone's replys, they were all good ideas.
i just got new (expensive) tires so ill be sticking with what ive got on that for now.
plus i don't want to diminish my braking capacity at all since i tend to have accidents.

i liked the ideas of retarding my timing and swapping the 5th gear from the older camry.
is there anything else i should know about in order to do these things?

Well if you havent done a timing belt change you should go ahead and do one when you retard the timing. If you timing belt isnt in need of replacement then just follow the same procedure for replaceing it just dont bother to remove the lower timing belt cover or crankshaft pulley/harmonic balencer. Get the crankshaft to TDC compression stroke, which if you cant find which TDC is correct then remove the distributor cap and spin the engine(with a 3/4" or 19mm socket/wrench on the crank pulley bolt, clockwise not counterclockwise) until the crank pulley timing mark shows TDC 0° and the rotor inside the distributor is facing #1 cylinders point inside the distributor cap. Now loosen the tensioner bolt and spin the crank clockwise 5-10 degrees on the timing marks on the crankpulley until the belt is 1 notch behind normal on the camshaft sprocket. Make sure the belt is tight along the top and right side of the motor and reattach the tensioner spring and tighten down the tensioner pulley to make the left/lower side of the timing belt routing tight again.
When you finish reassembly you will have to recheck your ignition timing with a timing light and loosen/spin the disrtibutor until it reaches 10° advanced though you might try a few degrees less advanced and see how the motor performs there

[eldrewado]

ok, so to be clear. for good highway mileage i should advance or retard the timing?

[RabidTRD]

How about better quality plugs? I get over 30mpg highway on my stock (aside from an intake... which helps MPG too) 5s. I run NGK Iridium plugs and simply the quality burn helps with fuel mileage. Using mid grade helps too. Don't make things so complicated if you're just trying to gain a few MPG. Tried and true methods usually are more efficient and least expensive.

[mkernz22]

too bad you have a '99 cause I was going to say you could just adjust the distributor if you had a '94 or '95

[Special_Edy]

I dont think it would help mpg when your still running 3000rpm at highway speed. It will lower the powerband to a level that would be easier to drive around town. Just more low end torque and less top end horsepower

[eldrewado]

too bad you have a '99 cause I was going to say you could just adjust the distributor if you had a '94 or '95

do u mean that 99 distributors arent adjustable or 99s dont have distributors because i have a distributor


also i have really nice plugs already, run mobil 1 syntec. put it in 5th whenever i can. syntec in the gearbox... i still never get above 27 mpg

if i could do 65 at 2700 rpm that would be great