The car feels sluggish/guttless when I put her in 5th gear going 55mph. This forces me to drop it back to 4th (spinning 3500rpm) while cruising on the highway. I have free flowing exhaust and clock my 0-60 in 7.2 sec, average so why can't it do 55-65 mph in 5th gear, like there's no torque in that gearing. I only bitch cuz my Honda can climb a hill in 6th gear spinning a low 2200rpm, so what's the deal in the series 5 gearing?

 

Mine was teh same until I fried my clutch...now it's worse. I have a 90 GXL too also with wide open exhaust, and it is quite whimpy in 5th gear. But you know the NA makes zero torque down there and also remember at 3500 your 5 and 6 ports are still closed, so you have less power than you expect. then when you shift to 4th you get higher RPM and a little torque and your ports open and you get the extra power too, so it maks a HUGE difference.

 

Oh wait, my bad dude. You mean that AFTER you downshift you are at 3500, well dang that makes all kinds of sence! For real because in 5th gear 55mph is going to come around 2300-2400 rpm if even that high. ANd at rpm that low the NA rotary makes like a negative torque This is why I only use 5th as a high speed cruising gear. I never go below 65 in 5th gear it's just way too tall a gear to rive that slow in.

 

And I thought my compression was low when in fact series 5 has taller diff gears. I know my 87 gxl can pull nicely in similar situations. Good thing I ain't paying super at the pump like I do for my other cars. BTW, you got pix of your new catback?

 

No, not the diff gear...that's not tall.....the 5th gear in the tranny is tall.

And no I don't have any pics of it on my car. only the pic of it that corksport supplies on their page, but that is off teh car.

 

The only time I touch 5th is to cruise at like 100 and up, unless I am on a road trip, trying to save gas. N/A's have NOTHING below like 4k RPM.

 

Hmm, I recall my 90 top out around 40mph in 1st whereas 87 tops out at 30mph, both taching at 7000rpm, that's leads me to believe series 5 has taller diff. If I can pull out the spec sheet on these gear ratios....

 

No you can't compare the speed per rpm levels between the series 4 and 5 because the gear ratios INSIDE the tranny are different. They both have the same rearend but the difference in the speeds you see at redline are caused by the tranny. There are 3 rears stock for the FC 3.9=auto 4.3=GTUs 4.1=everything else.

 

All FC 5 speed N/A's have 4.10 diffs except for the GTUs which has the 4.30.

refer to link

diff

 

Ah no, the 88 and 91/92 vert had the 3.9 rear end regardless of 5 speed or auto

 

Hmmm, I didn't see that on the page, sorry.

 

I don't know man.....
I can accelerate in 5th going 50mph no problem.
This is the same before and after I got my racepipe + resonator installed. Car got better torque after I installed the pipe.

Get good power from 2.5k rpm and on till around 7500rpm. Probably could spin higher if I weren't running the stock catback.

I have CAI too, if that makes a difference.

1990 GXL, 40k km on mazda reman

 

When topping out I actually slow down when I go to 5th gear.

 

I did a high speed run last nite.
I shifted to 5th going 200km/h @ ~7500rpm in 4th
It kept on accelerating t0 210km/h in 5th and I let off because I ran out of road.

 

Right, it'll still pull in 5th if you shifted at 7500, going from 4 to 5 at 7500 will drop the RPM to about 5800 ANd at that RPM teh engine is making good power and torque, so no worries. But the car does feel a little meak at low speeds in 5th. I'm thinking I'll get new plugs and wires and that might help me a little, at least in my head.