This may totally seem stupid but I am extremely used to a valvetrain to set the limit of my rpms. What is the highest safe rev limit on a built FD motor with either a large street port or half bridge? I have looked around for some reading on this, but so far it kinda just seems like people put it at whatever they feel comfy at....8200, 8500, 9000....

 

My theory on any rotary motor w/any port is, dyno it, an see when the power falls off, an there you have your rev limit.

 

If you want a rev limit regardless of porting or power drop-off; rotating parts weight, dynamic balancing, rotor clearance, and hardened stat gears affect this.
My old 1995 Mazda Comp Racing Prep manual does not give any rpm limits.

But it is really useless to rev too much over maximum power as it does not accomplish anything.

I have almost stock ports with a GT35R, I shift 8000 in 1st and 2nd, and 7500 for the rest. My max torque is around 6500 with max power around 7000.

 

Actually, I'd like to know what is the highest revving 13b...that actually made power up there.

 

heres a high revin 20b. i believe the tach goes to 14k. i dont know if they have had it wraped up that tight but but they take it pretty high..

http://www.mpsys.ca/MPSv1.htm

hey Messinian7. im in fort collins to. me and some other rx7 owners are getting together soon. send me a pm if you would be interested in meeting up.

 

I actually cant send a PM till I hit 15 on my post count lol so many rules =P

I actually don't have an rx7 yet. Im looking to get a project FD going within a year. I used to have a white nissan s13 coupe with a silvia conversion and sr20det, etc etc, i drove it around a lot--in case you may have seen it...but i sold it just recently so no more...hence moving on to FD.

 

According to this article in Import Tuner, this guy got his FD to rev up to 11,000rpm by a bridge port, so maybe a ballpark estimate would be like 9500-10,000rpm.

http://www.importtuner.com/features/...rx7/index.html

Check the paragraph that starts with "Given the full go-ahead,..."

 

hah stupid forum rules.. so are you doing all the work yourself?

there are some areas that will effect max redline. some are obvious, but some are rotary engine specific. it really depends on how extensive your build is, but for a street car i really dont see the need to increase the redline much. fd's have a stock 8k redline, except automatics i believe. rotary engines take overreving fairly well provided that you supply the needed fuel. if you have a reason to increase it beyond 8.5k - 9k look into these topics.

~ rotor clearancing
~ balancing of rotating assembly
~ hardened stationary gear
~ eccentric shaft flex
~ big ports and a big enough turbo to pump that kind of air- seems obvious but rx7's like big tubos
~ fuel - pretty obvious

 

Check this thread:

https://www.rx7club.com/rotary-car-performance-77/12000rpm-crank-451889/

 

Yeah i want to try and do as much of the work myself, since it wont be a daily I dont really mind the downtime it will have.

I was thinking of going for a half bridge, maybe even full bridge on a GT42R, so I was thinking maybe a raise to 9K would be good...Im not looking for anything crazy that would require that 2 piece e-shaft.

 

I've been wondering the same thing (for turbo sizing).

Originally I was thinking that a GT4088R w/1.05 exhaust looked like it was probably a pretty good fit for a B rew w/headers and a big DP, but if a streetport can go all the way up to 9k without major modifications it may make sense for me to think about stepping up to the GT4049R and lose a little midrange.

It looks like we're working on similar projects, what's your HP goal for your machine? What kind of VE do you expect to get? I've assumed around a conservative 90 VE initially (w/an RPM of 9k that gives about 52 lb./min max)--but I'm still a month or two away from purchasing so that was just my initial guess and I need to do some more research. I didn't really consider either of the GT42's for what I'm doing with a street port because I was thinking they'd both be too big. Are you planning-on pump gas ECR's?

 

Actually, just noticed you're in Fort Collins. Won't surge be an issue for you up there at altitude with a GT42?

 

About the compressor surge at my altitude (roughly a mile above sealevel)...you know, I have no idea...i didn't even think of that. I would imagine it would only be at lower rpms with heavy throttle, correct? You should fill me in on what you know...

My goal is around 600whp on 91 w/meth injection. VE im assuming is volumetric efficiency...although I don't understand the context you are using it in (im sure its legit, I'm just not super smart). Are you saying a 13Brew with a streetport will give a VE of 90%? Also whats ECR? Im trying to play catch up here lol

 

I think the Travesio(sp, I'm sorry,really) video shows the tach hitting close to 11k.

:edited for clarity.

 

Yep, I was meaning because of your altitude the air density is lower so your volume throughput is less for a given spool time (compared to someplace like down here in Houston where we're near sea level), putting you further towards the left of the compressor map, potentially over the surge line if you allow it to spool up as fast as it could. I have a '93 FD single conversion that I've never driven becuase I bought it with a blown engine, so really I don't know if that's an issue or not... I don't have a good feel for how these things spool yet, expecially in relation to the exhaust AR selection.

The other issue is the volumetric efficiency. I've been searching on here and can't find a good answer to what the VE of a good medium street port will give you, and that number also gets dumped into the equation for figuring-out which compressor is going to give you what you want.

Sorry, I should have wrote it out, by ECR I meant "Effective" Compression Ratio. Actually I should have just written boost really. Water/meth injection should help with your 91 octane problem up there. I'm planning on a water injection system too and I'm especially excited because I've been wanting to run water on my Saab for a long time but the engine management is too smart and goes crazy. (there are no knock sensors, it uses the spark plugs as ion sensors, post combustion, like the new M5's are doing).

Anyway, and sort of related, I finally found it and it looks like the stock CR on these cars is 9.0:1 so that gives an idea of what boost can be ran with pump gas.

 

Also, I'm just using A. Graham Bells generic/rough equation and conversion for lb./min calcs.

CFM=L x rpm x PR/5660

multiplied by 0.07 to convert to lb./min...I assume he's using STP (standard temp. pressure) but haven't checked yet.

edit: and using 2.6 L as displacement.

 

<noobquestion>
what is the recommended safe rev limit for a newly installed 13b ?

</noobquestion>

 

what do you mean newly installed? if its a rebuild motor then you need to follow the break in procedure.