Redline Question
 

This may be dumb but I read in a writeup about manifold swapping that mazda switched the redline from 7k on the s4 to 8k on the s5. Is this true. if so what would my redline be? I have a s5 block in my s4 car. I only really ask because im just learning manual and i would like to know my limits/powerband ect.

S5 N/A's did have an 8k redline, this is true, and s4 N/A's had a 7k.

You say you have an s5 block. What ECU are you running? Does the s5 block have ALL s5 internals?

The reason I ask about the ECU is because s4 ECU's have a rev limiter that kicks in around 7500 to 8000 rpms (hard to say where exactly because the stock tach is inaccurate at that level).

Heh, neither is really the limit of the engines...

But yeah, S5s have an 8k redline... rev limiter at 9k I hear? Never hit it myself... so either I was shifting just barely in time or it's higher heh.

If you have an S5 block then mazda says your redline is at 8k. If you're using the S5 ECU then it won't bounce until after that too.

If you have an S4 I'm guessing the rev limiter is lower, and the tachometer in the car shows a redline at 7k.

--Gary

Yes the block has all the s5 internals. Im still running the s4 ecu. I asked friends of mine who helped me build this fc and he told me that since it was once an automatic it doesnt have a rev limiter. This sounds like crap to me but i figured i'd ask anyways.

Would it be possible to put a s5 ecu on without changing the harness and if so what are the numbers of the s4 and s5 ecus so i knwo what i ahve and what i need. This may seem reidiulous to some btu im tryign to change everything on my car to s5, i already got the exterior down and now im working on the engine by changing the manifolds to match the block.

More than the rotors determin what the redline is.

If you have S5 flywheel and Rotors with a S5 intake and ECU, you should be able to have a 8k Redline.

If you have a S4 ECU or Flywheel, or intake, then you are restricted to a 7K redline.

And remember the engine runs out of power (unless you have done some porting) at around 6.5-7K anyway.

Ok so if i have a s5 core with a s4 front cover, s4 ecu, s4 manifold i have a 7k redline. SO i would have to change the manifolds (plannign on doing anyway) and the ecu in order to have a 8k redline. Is it possible to put a s5 ecu on a s4 harness?
I dotn really care so much about having a higher redline since im told the powerband is almost exactly the same, im just wondering. This subject has intrigued me as of late sicn ei read the above mentions article and learned my friend raise his cars redline to 12k be adding aftermarket cams, rods pistons ect.

Is it also true thta the 13b's redline raises with porting. How do you tell your redline if i wasnt told to you?

I'm hoping your friend's car isn't a 7 because I would love to see him put cams in a rotary.

LOL no, its an integra type r

Rotaries can rev higher easier than pistons (at least to me) with some simple changes. First of all, if you're going to go higher than 8k (s5) then you have to go standalone (or carb, but standalone is better) because the stock ECU has the rev limiter.

You SHOULD do some oil mods to keep high enough pressure for high rpm driving. And it'd be a good idea to get Type II stationary gears from racing beat for sustained higher rpms. Of course people go above 8k with only oil mods, or none at all, and are fine. It's just safer to do it that way.

And the reason you may think porting makes for a higher redline is because our cars don't make power past the stock redline on stock ports. Once you port they *can* make power past the stock redline with proper setup and tuning.

^yep exactly. Also what icemark said, he knows his shit.

I got a question for you tho icemark. WHy does he need to have the S5 flywheel, is it more properly balanced than the S4, thus allowing it to be used in a 8k rpm? If its an s4 does it have the risk of exploding or something, or will you get some really messy vibrations that may shake things apart?

OK thanks. So having a higher redline wouldnt have any benefit to a stock ported fc..

Basically. Before I ported my motor I did shift at 7500 on the track, though, in my s4 but I did some other things that helped with shifting higher.

You were shifting at 7500 in a s4? So im assuming you had all the mods you advised above. Where would be the best place to shift ina stock s4 to gte the most of the power without risking the engine.

No I didn't. When I was talking to you about supporting mods to go past an 8k (s5) redline, I thought you were saying you wanted to go to 9k, 10k, or like 12k like you talked about with your friend.

500 rpms over the stock redline isn't a big deal you don't *need* those mods, oil mods would help though and possibly something like an MSD6a.

Best place to shift is dependent on the car, different mods will create different scenarios. When I was shifting at 7500 I had done a fair to my car already, before porting, and it would start to die off a little before 7500 but on the drag strip I got better times staying in lower gears shifting at 7500 than shifting at 7000. So it all depends.

in my cars i always dip slightly into redline, on my CRX it redlines at 6500rpm, i take it to 6800rpm.... on my 7 it redlines at.... well.... 7000rpm yet i take it to approx 7200rpm....

:devil:

You know shifting past the redline isn't so bad in these cars on occasion either.

Probably avoid it on high mileage engines... but as long as you're not bouncing around inbetween 7k and 8k for a minute or two straight (*cough*autox*cough*) it's not gonna be that hard on your car to occasionally shift 500 past the redline.

It's common sense, the way the engine is designed a quck and short-term passing of the redline isn't going to hurt anything... you just don't want to make it part of your every day driving style.

Besides, gets a little loud up there anyway. ;)

--Gary

The S5 flywheel is considerably lighter than the S4 and designed to go up to 9K.

So using a S4 flywheel and spending too much time at 8k is pretty much a death warrent if you don't have scatter shields.

I wouldn't spend too much time above 8500 with an s5 flywheel either without a scatter shield.

But you bring up a good point, I forgot to mention the importance of the flywheel, and furthermore a tranny that can withstand higher rpms. I know Mazdaspeed7 who goes to 9k+ regularly has gone through a couple TII transmissions himself.

my CRX has 389,000km's on the original everything and i shift at approx 6800rpm

no-go-boom

:devil:

And that has absolutely nothing to do with anything here and I wonder why you are even posting that.

just to show that if you go a little into the red it's not gunna hurt a damn thing and that no one should be worried about shifting a wee past redline....

:devil:

182,000 miles and Im still shifting at 9k at the track. I only do that through first gear though. Its a s5 conv. Rev limiter...didnt know it had one. hmmm. Mods include intake, full open race exhaust, S-AFC, e fan, and RP underdrive. Whats a CRX???

a CRX is a honda, you know, honda CRX.... "pocket rocket" 2seater....

:devil:

Will it really explode? at only 8k rpm? I thought you had to be at 10k before that shit happens.

I was told no here once before that without the scatter guard, you can actually get killed by the pieces! is this over exaggerated?

wow. whats a crx?? its a pocket rocket. A crx is a model made by honda from 1986-1992(i think) & they came in 2 different models(i think) & they were Hf & Si. The Hf came with a 4 piston 16 valve D15 motor which was pushing around probably 95 horses & the Si model came with a D16 motor which came with around 110 horses. since this is not a Honda Forum im not gonna get into it. just go on google or yahoo & type in "specs for a Honda Crx" & it should show up with pics & specs for the car.