Engine mods needed to run safely past redline.
09-11-07, 08:13 PM
#1
Engine mods needed to run safely past redline.
I heard that you shouldn't have to go past 7k with a stock car because it does not make anymore power after 7. If you modify the carb and exhaust, what is the advantage? Is it justifiable to rev it to 8k? I heard that is when the E-shaft starts to bend and whatnot.
Just want some pointers to clear the confusion.
Just want some pointers to clear the confusion.
09-11-07, 08:20 PM
#2
Eats, Sleeps, Dreams Rotary
Join Date: Jul 2004
Location: Allentown, PA - Paterson, NJ
Posts: 3,247
Likes: 0
Received 2 Likes
on
2 Posts
I use to go close to that back when I had my modded nikki and RB exhaust w/ MSD set up. Never had any issues and seemed to pull strong. Someone (i forget who) posted a short video of there yellow rx3 hitting 8k......or was it 9k? I forget its been a while. Wacky was that you?
09-11-07, 08:24 PM
#4
I noticed that my car pulls way harder after 5.5k rpm. The chokes are bigger than they are supposed to be AFAIK. Reason my asking, Bad83 and I have both witnessed my car being able to one-wheel-peel first and bark second, but when I was leaving an old work place, My father wanted to see what it could do. Revved her to 6k and dumped it. Got both rears to spin all through first, and when the tach jumped to 8, I shifted to second and got the right wheel to peel all through 2nd as well. I mean all through it! I have to go down there and get a pic of it, I think Sam would be impressed. You can see two wheel marks, then one wheel, no hesitation like I shifted or anything.
I got skeptical because I dont want to cause any hardcore internal damage to the engine (like apex chatter).
I got skeptical because I dont want to cause any hardcore internal damage to the engine (like apex chatter).
09-11-07, 08:55 PM
#6
from what ive read, apex chatter is caused by sustained high rpms and shouldn't be much of an issue for momentary high revs. i think that most of the damage that comes from high rpm on our stock motors is shaft flex and the rotors making contact w/ the side plates. i know that hardened stationary gears and an upgraded oiling system is usually reccomended for high rpm motors too
Trending Topics
09-11-07, 09:49 PM
#12
chatter can start at about 7500rpms but usually under a heavy load. Spinning the tires shouldn't cause this since it is usually momentary and the motor isn't under a heavy drive load. I spiked the tach at 8k once at the track off the line. I didn't think the needle could move that fast LOL. Those were the days when the old girl could chirp 3rd.
09-11-07, 10:46 PM
#14
FB+FC=F-ME
Ive hit 8000 a few times in 1st or 2nd gear when the tires would start to spin free and the revs would catch me off gaurd.Did it the other day going up a freeway on-ramp with the backend fishtailing the whole way.
It actually hit the rev limiter this time,which I have never done previously.It cut in a 8000rpm,I just happened to be looking down at the time,although I should have been looking up in order to keep the beast pointed straight! Although I dont make a habit of doing it,I dont worry about hitting 8K with my ported S5 TII engine, since it has the same rotor weight as the S5 N/A and my turbo can move enough air to make some power up there.
The S5 N/A engines have a factory 8K redline,so there should be little problem taking the lightweight rotor equipped 12A's to 8K,if your making any power up there.The 83-85 12A rotors are almost exactly the same weight as the S5's and the 12A is shorter,so the Eshaft is stubbier.The only hang up would be the 3MM seals of the 12A being rougher on the housings than the multi-piece 2MM seals of the 2nd gens.
It actually hit the rev limiter this time,which I have never done previously.It cut in a 8000rpm,I just happened to be looking down at the time,although I should have been looking up in order to keep the beast pointed straight! Although I dont make a habit of doing it,I dont worry about hitting 8K with my ported S5 TII engine, since it has the same rotor weight as the S5 N/A and my turbo can move enough air to make some power up there.
The S5 N/A engines have a factory 8K redline,so there should be little problem taking the lightweight rotor equipped 12A's to 8K,if your making any power up there.The 83-85 12A rotors are almost exactly the same weight as the S5's and the 12A is shorter,so the Eshaft is stubbier.The only hang up would be the 3MM seals of the 12A being rougher on the housings than the multi-piece 2MM seals of the 2nd gens.
09-11-07, 11:16 PM
#15
I use to go close to that back when I had my modded nikki and RB exhaust w/ MSD set up. Never had any issues and seemed to pull strong. Someone (i forget who) posted a short video of there yellow rx3 hitting 8k......or was it 9k? I forget its been a while. Wacky was that you?
yup, 9K. thats my RX-3 (formerly chiquito banana RX-3). Been abusing racing it for years and continues to run strong.
09-11-07, 11:40 PM
#16
I noticed that my car pulls way harder after 5.5k rpm. The chokes are bigger than they are supposed to be AFAIK. Reason my asking, Bad83 and I have both witnessed my car being able to one-wheel-peel first and bark second, but when I was leaving an old work place, My father wanted to see what it could do. Revved her to 6k and dumped it. Got both rears to spin all through first, and when the tach jumped to 8, I shifted to second and got the right wheel to peel all through 2nd as well. I mean all through it! I have to go down there and get a pic of it, I think Sam would be impressed. You can see two wheel marks, then one wheel, no hesitation like I shifted or anything.
I got skeptical because I dont want to cause any hardcore internal damage to the engine (like apex chatter).
I got skeptical because I dont want to cause any hardcore internal damage to the engine (like apex chatter).
Revving and dumping the clutch like that can lead very quickly to broken drivetrain components if you know what I mean.
My last Se when I ran the S4 intake on it and the other mods would burn the tires thru 2nd then throw the car sideways in 3rd. I wasn't prepared for it to do that either. Needless to say my eyes were alittle wide.
09-12-07, 01:25 AM
#17
Double Ds for me to share
I've taken my old half bridge 12a to 9500rpm on the dyno and the strip. Only stopped there cause the ignition system couldn't keep up with the engine. So far on the 13b peripherial port it goes to 9000 rpm will be more once it is tuned, not making power past there with the old exhaust. Once we retune it i will let you guys know how far we take her up to.
09-12-07, 03:28 AM
#18
Junior Member
Join Date: Jun 2007
Location: arlington, tx
Posts: 35
Likes: 0
Received 0 Likes
on
0 Posts
first thing that popped into my head about supporting mods was a scatter shield for when a rotating item failed with pizazz but i guess it's not as necessary as i thought it was.
09-12-07, 06:14 AM
#19
Lives on the Forum
I believe that the main problem is the weight of the apex seals. Once you hit the higher (8000) rpms, the apex seals start to pull away from the housing surface resulting in the dreaded chatter. Carbon seals can do a better job due to their lighter weight, but you have to rebuild every 15-20 thousand miles with those...
09-12-07, 10:30 AM
#21
Yes.
In addition what others said about motor mods, plus the rotors need to be clearanced on the land (face) so they won't hit the plates. Then the rotating assembly balanced. You want 10psi of oil per 1000rpms to keep from seizing bearings. So the RB 85psi regulator is only reliably, consistantly good for 8500rpms by the book.
In addition what others said about motor mods, plus the rotors need to be clearanced on the land (face) so they won't hit the plates. Then the rotating assembly balanced. You want 10psi of oil per 1000rpms to keep from seizing bearings. So the RB 85psi regulator is only reliably, consistantly good for 8500rpms by the book.
09-12-07, 12:06 PM
#24
sellout
iTrader: (4)
Join Date: Jan 2005
Location: Lawrence KS
Posts: 3,078
Likes: 0
Received 0 Likes
on
0 Posts
last summer me and alex7 bought a $500 rusted out s5 that ran great. the s5 redlines at 8k anyway but we gave it hell. when the motor was tore down one of the rotor housings had a like a wash board texture if you ran your finger nail over it. still ran strong and made good compression til the day we pulled the motor, just made that one housing unuseable.
09-12-07, 12:30 PM
#25
Moderator
iTrader: (3)
Join Date: Mar 2001
Location: https://www2.mazda.com/en/100th/
Posts: 30,993
Received 2,691 Likes
on
1,905 Posts
chatter is a function of a few things.
1. rpm
2. lubrication of the apex seal/rotor housing, the higher the friction, the more the seal is going to want to skip across the surface.
3. apex seal spring
its not uncommon to see bad chatter marks on high mile engines that have just been driven normally.
1. rpm
2. lubrication of the apex seal/rotor housing, the higher the friction, the more the seal is going to want to skip across the surface.
3. apex seal spring
its not uncommon to see bad chatter marks on high mile engines that have just been driven normally.