NZConvertible

What difference would that make? And please don't say anything about secondary injectors...

13b4me

Honestly what is the point of this post? It's obvious the difference that would be made when you're running 4 injectors, as opposed to 2... If you have information suggesting otherwise please enlighten me, because I've always noticed a decrease in gas mileage above 3800 RPM's... Hmm wonder why...

You'll find anything to argue about won't you?

NZConvertible

Excuse my frustration, but I've explained how Mazda's staged injection works so many times it's not funny (twice just this week). When the secondaries come on, all four injectors are fired at half the pulsewidth the primaries were firing at before the transition. There is no sudden increase in fuel flow or change in AFR (unless something is wrong). If this were not the case you'd get a drop in power as the mixtures suddenly when rich. Obviously no car maker would deliberately do this.

Because you were going faster, which uses more gas. Not rocket science. It has nothing to do with what injectors are firing. The exception would be upgraded secondaries with no control or tuning.

I'm not arguing with you, I'm correcting you. If you have a problem with that (and your numerous digs at me suggest you do) then deal with it. I'm not going to ignore incorrect info because you can't handle being corrected.

DanicaTimesSeven

5th seems rather powerless only some times. It's up the long, gentle uphill runs you notice it, but for the most part, 5th pulls HARD compared to A LOT of other cars. This is an 86 GXL mind you. I do a lot of driving on I-85 at 80mph and faster, and there are some steeeeeeep hills. I've never had to downshift to prevent losing speed, but I don't gain it either and you have to practically be flooring it (Cruise will completely floor it)

Some times though, I can accelerate uphill at 50-60mph in 5th.

5th is adequate for MOST passing manuevers, so I dunno what some of you are talking about.

Rev match and drop to third? What's the highest speed you can go in 3rd without redlining?

Shifting through gears at 8k? You have an N/A , right? We redline at 7k, is it even SAFE to be entering your redline and maxing it like that?

tinvestor

No longer offered they emailed me this morning to tell me they are looking for a new place to supply them with modified ring and pinion.

Black91n/a

That's too bad that ISC doesn't offer the 4.8 anymore. Try asking ITS racers, as they'll commonly use the 4.8 or a 5.12. There's got to be other places that sell them, but it does require some custom machining, as it's not just a drop in swap.

As for the 5th gear passing and power, the earlier cars (86-87.5) had a shorter 5th (0.711) than the later cars (87.5-91 with a 0.697), so that makes a difference, along with some added weight. The turbo trannys have even shorter 5th gears (0.762 and 0.719).

I hope when you're talking of passing in fifth it's with a dedicated passing lane, and not on a 2 lane road, as that'd be stupid and dangerous. On 2 lane roads I always pass in 3rd and I get a run at it to minimize my time in the oncoming lane. Even if it is a dedicated passing lane it's good to get the pass done quickly so that others can get by too and to make sure that there's room for them when the passing lane ends.

DanicaTimesSeven

Don't you worry about it.

twilight slide

On my s4, 7k (redline) in 3rd was ~80mph
If he has an s5, redline starts at 8k. . .

DanicaTimesSeven

I thought only the Turbos redlined at 8? The S5 N/A is only 160hp...12 up from the S4. I cannot believe that would justify an extra thousand revs...

Black91n/a

The S5 NA is the only FC that has an 8000rpm redline (the turbo was still at 7k right?). You don't need more revs for more power and you don't always get more power with more revs. The increase in power and the increased redline are related in this case, the rotors changed amongst other things, and they got lighter with higher compression, allowing more revs and power. The power peak for the S5 NA is at 7000, so the extra 1000 aren't "needed" to get the power, but it helps with acceleration and such, plus it's just cool, and it makes a good marketing gimmick.

cbrinega

I put in a GTUs diff (4.3) after having my car for a couple of years. I immediately found that the car felt more peppy and "normal" in first and second gears driving around town (shifting at 3.5k is okay now), and I also liked that I could drive 55 MPH in 5th and not feel like the car was bogging out.

Several months later I switched to lighter weight wheels and slightly shorter tires giving the equivalent of about a 4.45 rear with stock tires (or roughly 10% more torque at the road). I consider these changes to be some of the best I've done besides exhaust and a true cool air box. I've noticed little to no gas mileage changes (gets about 25+ on the highway).

The car runs great with my setup, and passing is fine in 5th. Also, the gears are not so high that downshifting into 3rd on the highway is difficult, and getting into second when taking a corner about 40 MPH still works out well. If you can get the gears cheaply, then the 4.3s are a good upgrade.

My ideal setup would be a 4.8 rear, 215/45-17 tires, and a custom 5th gear for cruising. That way I would be set up for short road race courses, drag, and highway (especially since a 6 speed in the FC would be big $$). I've never met anyone with a 4.8 rear that drives their car on the street, so I can't comment on how the gas mileage would be. But it would be a blast to drive...

Terrh

iTrader: (7)

ME TOO!

it's really bad in my other car (civic) where 3000rpm is only 60mph. Doesn't need the power but it would be nice to lower the revs some at cruise.

I want my FC to have a 6th gear, I love how the first 5 are placed but cruising at 4000rpm down the freeway gets old.

peejay

The factory computer goes open-loop over 3800. Basically, full rich to protect the converters.

NZConvertible

It may go out of closed-loop over 3800rpm, but it doesn't go "full rich" unless you have your foot buried. An S4 TII (for example) only needs ~50hp to cruise at 85mph (3800rpm in 5th), which certainly doesn't require rich mixtures to protect anything.

peejay

Sure it does. They want the mixture way rich to ensure that there is *no* oxygen in the exhaust, so the converter isn't functioning. Converter life is one of the major priorities for an OEM's engine tune.

NZConvertible

"Full rich" in my book means the same mixtures as you see at full load when stock, i.e. a 10:1 AFR. Sorry but I don't believe that happens when cruising. If someone with a wide-band can back this up with actual readings then I'll happily stand corrected.

dest101auk

a lightweight flywheel and some race pulleys should help out ...If somebody already mentioned this sorry i only read the first few posts.