s1mpsons

iTrader: (5)

Can someone please advise on whether or not I can safely raise my rev limiter given that I have a lightweight flywheel and stock internals (never balanced for flywheel)?

If I understand correctly, the OE limit is 8300 rpm. Can I increase over that, should I decrease below that, or simply maintain OE limit? My goal is to be able to really rev out 2nd gear for autox purposes. On track and other high load / high gear /high performance driving instances I would shift at ~ 8K (when I see the needle pointing at 3 O'clock).

Cgotto6

iTrader: (8)

personally I see no reason to as the normal power curve is starting to taper off around 8k anyways. Why not change your rear end gear ratio so you can get more speed per gear. Like go to the auto's 3:90

s1mpsons

iTrader: (5)

Shifting take tenths of a second and down shifting even more so than up shifting. Additionally, a down shift is very tricky (can really compromise threshold braking and braking points) if it is not executed perfectly. In autox, you need to be perfect or you're SOL. I'd rather slowly increase RPM and speed in tapering off power band than bang the limiter or shift.

As far as a 3.9 rear end, that is the complete opposite of what I want for autox. Considering the 4.77 rear, actually, to get more acceleration.

Lastly, such high speed sections are few and far apart (if at all) at an autox. I would just like to know I have the RPM if I need it

Cgotto6

iTrader: (8)

Hmm...If you jump all the way up to the 4.77 no matter how high you wanna over rev the motor there is no way you will be able to stay in 2nd gear if you are already having problems with it. I would think the 4.22 would be a better option. If shift speed is a concern maybe an affordable dogbox would suite you well.

s1mpsons

iTrader: (5)

I'll bang the limiter, and thus stay in 2nd.

Shifting and rev limiter are NOT currently a problem with my 4.1 gears. In fact, I never get close to redline. A good compromise would be a 4.66 diff, but I would rather do the diff right with the 4.77 now and balance the motor later for a 9K redline rather than having to go back and redo the diff to match the engine capabilities post rebuild.

I appreciate your help and all, but none of this is answering my question. I just want to know what the safe rev limit would be given my flywheel. Please let me worry about shifting, final drive, and other issues.

seandizzie

iTrader: (1)

Will a 4.77 allow you to stay in 3rd instead of 2nd at similar speeds?? If you don't mind losing your topend and highway cruise rpm I say do it.

Or try a taller tire and maybe a 3.90, that should allow you to run a little more mph outa 2nd gear.

to take advantage of stock porting and APEX SEAL Springs you should shift around 7500 anyway, no need for the super high rpm with stock ports and parts. there is a reason mazda put the rev limiter where it is...chatterchatterchatter

Flywheel shouldn't be a issue. unless it is a pos

s1mpsons

iTrader: (5)

Reason was... Warranty.

s1mpsons

iTrader: (5)

Does anybody have experience with raising rev limiter?

adam c

iTrader: (2)

What class do you race in? It is illegal in most classes to change gearing. If it is legal, you might be better off getting taller rims & tires on the rear.

In seven years of autocrossing the FD, with 245/45/16 tires, I have never needed 3rd gear.

s1mpsons

iTrader: (5)

Do you run 4.77 gears? Did you see Lincoln NE airpark, site of Solo nationals?

Building SSM from ASP.

If you have jspec turbos as it reads in your signature then you are ssm and can change gearing, FYI.

Chadwick

iTrader: (12)

If the rotating assembly was still stock I would say you should have no problem turning up the rev limiter to 9k. Mazda does a pretty good job of balancing the rotating assembly at the factory, the only real issue is the fact that you have changed out the stock flywheel to a counter weight that is not balanced to the rest of the assembly.

I personally would not raise the rev limiter more then a few hundred RPM unless I had the internals balanced but I do lean towards the conservative side on issues like this.

For those that don’t understand the reasoning of a 4.77 and a higher rev limiter. It is simple; the goal is to keep the engine in its peak power band 100% of the time with as few shifts as possible. The stock gearing is to low when exiting low speed corners and you will lug for a few tenths while building boost. A 4.77 solves this problem but limits you at the top end which can be an issue on faster courses.

Hope this helps,
Dan

s1mpsons

iTrader: (5)

Dan to the rescue! So like 8500 rpm would be a safe bet.

Chadwick

iTrader: (12)

Safe? No idea, you may already have an issue and not know it. Best way I know to tell is monitor knock. Do a few pulls to 8k and get a base line of the engine noise between 6.5 and 8k. Then slowly bump up the rev limiter and monitor the knock. If the base raises past 8k then your engine internal are out of balance and you should probably not push it. If the base stays the same or decreases.... crank it up

Think of it like an out of balanced wheel, you know how at different speeds you will have a shimmy and at others all feels good. What you are watching for in the knock reading is the shimmy .

On my motor the knock sensor is super sensitive, my base at 7k is around 25 and it decreases as the rpm's go up to 10 at 9k.

Dan

Cgotto6

iTrader: (8)

Right, they only warranty it up to a certain point, then the parts start to fail after that point. Hence the warranty.

s1mpsons

iTrader: (5)

Dan happens to be the '09 SSM National Champion and a reputable tuner. FYI.

Additionally, it seems to be commonly accepted practice of most tuners to raise the rev limiter of stock motor to 9000rpm safely (w/ oe flywheel in place for proper balance). Forget mazda specs, rev'er up.

(Why do I always get into battles when I start threads here... )

adam c

iTrader: (2)

I now autocross on street tires, and mostly for fun. Our track never seems to see 3rd gear speeds. I used to race Pro Solo, and divisional autocross races with my 79 RX7. It was an all out CSP race car. Not a street car.

As I mentioned earlier, taller rear wheels & tires might help you. Are you installing wider fenders?

GoodfellaFD3S

iTrader: (213)

Um, who is telling you this?

I'd recommend checking out some dyno charts of FDs with stock ports and tell us what you find

Sandro

iTrader: (1)

Excellent advice Dan!

Monitoring knock as a simple and effective way for checking balance of the rotating parts at various rpm. Brilliant!

Jake may have already a problem at lower rpm because of the lightened flywheel - yet with higher frequency harmonics.

Jake, time to get a Datalogit now...

- Sandro

arghx

iTrader: (3)

people tach out the series 5 n/a engines all the time, it should be fine

Julian

iTrader: (14)

statement was partly true on the old 12A's. clould open exhaust and just let rpms increase. However without porting engine had a natural limiter.

Mazda told me not to worry about the engine, just the trans at 8k plus.

As to the FD's ??, I have used an 8500redline for years and yes in auocrossing and sole trials you tend to ride the limiter rather than lose time in a shift.

Tem120

iTrader: (5)

now I'm trying to increase my rev limiter so that I would never hit it . as I've heard horror stories about fuel cutoff rev limiter . I'm not sure if my motor has a stock flywheel it looked stock , but hte motor was rebuild so the PO might have installed one .

is the knock test a good way to try it ? its not about having a longer gear , but knowing how high I can make it so as to not bounce off of it until I get some sort of ignition cutoff system for the rev limiter

DaleClark

iTrader: (55)

In general, rotaries don't mind high revs for short stretches of time. When you get past 8500 or so you get into some weird harmonics from what I remember.

The other biggie is all the stuff you're spinning with the motor - alternator, power steering pump, water pump, etc. I've met a guy with an '89 GTUs who heavily autocrossed it and blew up the power steering pump from staying at high RPM.

Mazdatrix and Racing Beat have some good tech info on high RPM rotaries.

As stated, power will drop off big time at 8000 RPM, but if you're just needing some extra revs to keep from having to shift that's another story.

Dale

Tem120

iTrader: (5)

this and since my power FC only has fuel cut . which = blown up rotary until I get an MSD with ignition rev limiter . I'd like to have an oh **** I accidentally over reved but I didn't hit hte rev limiter , so basically i know after 8k the power does down but if for example my power FC's stock limiter is at 8100 , realisticly chances are if you try and get perfect shifts eventually you will over rev and in my car's case with fuel cut , risk going cablewie ! so I'd like a little free space to keep from bouncing off the rev limiter in certain moments , I've done 90 mph in an auto-x before but that was .. special .. LOL and in a miata.

I just want to protect my motor by making it rev higher LOL . my target shift will be 8k , but incase I pass that I dont want to be bouncing off the rev limiter . and risk a blow because of something so common as a missed shift point .


Thanks for hte advice I'll try 8500 , and look into those notes