Anybody know the absolute redline for this engine? I know I've taken mine over the 7k mark. Seems like she'll rev forever.
thanks in advance

 

I reckon you know the answer...lemme see if you agree with this...

If by absolute redline you mean the RPM before the engine explodes - who cares right? The experiment is easy: (1) disable the limiter, (2) put the car in neutral, (3) open the throttle, (4) note the point of failure.

Step (4) will vary a fair bit I think - some cars would explode at 7,500 and others would go quite a bit higher. Cost of the experiment would be in the 10-12k range.

If by absolute redline you mean a safe limit that will not drastically shorten the life of the car, then I'd defer to the manufacturer. My car redlined at 6,500 RPM before the Works package went on, and I believe that now it's a bit higher - like 7k. The only time I hit it is in competition, and needless to say I am not watching the tach.

I bet there are folks here that have built their engines to sustain > 7k, but I also bet they have replaced rods, crank, and other high stress components to support that high rpm load.

I think our motors won't run as hard as some of the Honda engines (I see them at 8k and up rather frequently in the mod classes), and since we make max torque around 4k the overall increase in acceleration to be gained by shifting up in the stratosphere is pretty modest.

I use 6k once in a while on the street (coming up to highway speed here in Massachusetts can be quite a rush depending on where you are), but generally shift at 5k.

Mebbe I'm an old risk-averse wuss, but that'd be my suggestion to those that want their Motoring pleasures to last without breaking the bank in the process.

Cheers,

Charlie

 

hello charlie,
being my first mini, no, i don't presume to know the answer, which is why I asked: to learn something.

Yes, I mean the safe operating redline. I did not intentionally rev the engine that high, it just seemed to spool up there before I realized how high the revs were.

The Tach in my car shows the red starting at 6.5k and I'll use that as the upper limit.

Your answer is appreciated, thanks. It does make me wonder the relationship between torque and acceleration, since the car certainly will continue to accelerate past 4k. Can you explain? I live at 7k ft above sea level. Seems the blower doesn't really get going 'til 3.5k and the acceleration after that is rather strong right up to 6.5k rpm.

 

THe best explanation of what factors make the car accelerate hardest can be found in the accompanying thrust chart. This takes torque at the crank, the multiplication of torque at the gearbox and final drive, and dumps the whole thing out as thrust at the front wheel contact patches.

The left axis is thrust in lbs, the bottom axis is RPM, and there is a line for each gear. Note that the top line (1st gear) peaks at just over 1,900 lbs - which means wheelspin!

The front end of the MCS only weighs about 1,700 lbs on a level surface. Under max acceleration weight transfer reduces that substantially, and the limit of grip on even the best road tires is about 1:1 (one pound of resistance to slippage for each pound of downwards weight on the tire).

Even at 4k rpm (max torque) in 2nd gear wheelspin is inevitable except on the best surfaces and with good rubber.

My best observed acceleration using GTech data is about .5g, which means I was transferring about 1,300 lbs of thrust to the pavement against an approximate weight of 2,600 lbs for the whole vehicle.

One other thing that this chart shows however, is that the fastest overall acceleration may be achieved by shifting at redline in all gears. There is never a point where the next higher gear will generate more thrust - yes the engine torque falls off at higher RPMs, but the mechanical leverage provided by the lower gear more than offsets the loss of torque.

Cheers,

Charlie

 

A few vendors sell spring kits to use withcams to allow a higher rpms...
But....
The redline of the sc is about redline of the motor (you loose huge % effenency wise, and get a very hot output with a roots style sc when it is run harder....(resulting in retarting the ignition ...so less power).
A safer way to run the sc harder and not tear up a motor is to add a pulley...
Remember, redlining stresses mant parts to the absolute desgin limits...it may work one day....but not the next...boom!! Great fun though...

 

thanks Charlie and Zippy.

I am investigating installing a 17% pulley, which, by all accounts is the biggest reduction available for daily driving that won't overheat the engine. It would be great to get more torque at lower RPM and not run the engine to the redline: the car has 85k miles on her.

Will I have to "flash" the ECU or replace the software, or does it learn and adapt to changes?

 

As far as I know you do not have to alter the ECU software for a pulley - the resulting pressure and temperature changes are within the tolerances of the manufacturer's tables and therefore the Mini can adapt.

Just for your amusement, I hit the limiter three times yesterday on a fast course at Devens. That's a total now of six times in 167,000 miles.

Cheers,

Charlie

 

Now that must have been a surprise! Sounds like you were enjoying yourself. Thanks again for your posts.

 

Not too surprising. The limiter must just pull timing, as the engine note doesn't change - it just kinda flattens out suddenly.

I actually looked at the speedo as I crossed the line (plenty of shutdown area, so I could afford a glance) and it was indicating 71 mph in 2nd gear. In my car the speedo is about 4 mph optimistic.

A fast course - unusually so.

 

Normal rpm cruising with a 17% is fine....running wot (floored, or more than light throttle), can result in operation a bit leaner than ideal...so not the best option without a tune if yoy run beyond maybe 6000 rpm regularly (will alsobe pushing sc beyond desgin limits and possibly causing the water pump to cavitate, possibly making less hp at higher rpm), but you get more fun driving in the normal ranges ...many tuners will tell you a 15% will generaly make more hp on a dyno due to heat, but a dyno is just a tool....in my book driveability rules...so the 17% won.....belts with high rpms and a 17% can be an issue...usually on the track....i ended with with a 17, then did slightly bigger injectors and a tune...so ultra safe for the motor...great feel, nice tq band..but most folks in my area went with just a 17%...we do have 93 octane here..a pluss...if we had just 90 or 91, it might not work so well.
with a pulley, in loght cruising the o2 sensor is used by the computer to adjust the computer, but WOT, the computer uses stored maps for fuel delivery..the o2 sensor cannot respond fast enough. The stock S actually runs a bit rich than many folks think a forced induction motor needs to be run, so the 15% get most a better running motor, very safely....great option for folks who track/redline...can later added a +2% crankshaft pulley to get to the 17%, no belt issues if you want a bit more zip.

 

The R53 will only rev until it hits the programmed rev limiter. The rev limiter kicks in at a programmed RPM to protect from over-reving the engine. My 06 MCS JCW GP is programmed with a 7250 limit. If you car has the JCW engine package the rev limit should be about 7200 RPM.

You can safely take the car to the rev limit and you will feel/hear the engine cutting out at the limit. You can try is easily in first gear.

 

+1 on that. That's the whole point of the rev limiter, it's the RPM the engineers of the engine decided is the theoretical maximum safe RPM for the engine. Of course that doesn't mean you aren't going to blow something up if you drive around hitting the limiter on a regular basis, it just mean if you hit it once or twice, it shouldn't hurt anything. Most cars stop making usable power before they get there, so it's not often there will be any practical reason to actually hit it.

 

Hi Zippy, thanks for the info. I'm at 7,000 ft above sea level, so I rely on the computer to sense the O2 and compensate. But if it is indeed correct that a 60% or 80% open throttle means the computer is using stored information rather than actual O2 sensing, then it might explain why the acceleration seems better when I gradually increase the throttle rather than flooring it.

But won't the computer learn that it needs to create a leaner mix with a more open throttle? I feel like the response from the sc is not consistent: sometimes I'll feel a boost and others not. BTW, the best I can do here is 91 Octane and I wonder if I'm really getting that out of these vendors' pumps.

 

+1 on the "once or twice" advice.

I rarely use more than 5k, and over 6k hardly ever.

Racing is different, but that's a calculated risk, I get about 50-60 minutes a year in total, and even then most courses have me under 6k.

The blown cars will pull to redline and smile, unlike the conventionally aspirated (and nasally congested) cars I've known in the past.

And of course the good mileage (30-35 mpg) is found in the 2-3k range, and goes away muy pronto at about 3,500.

It's a philosophical question - how quickly do you wish to consume this goodness?

</blather>

Cheers,

Charlie

 

the o2 sensor is to measure the completness of the combustion....and the co.puter will adjust the "trim" or an overall adjustment...to my knowledge, this does not include wot, or no tune would ever be needed.
The computer uses to map/maf sensors to determine the airflow...and thus adjust th fuel needed....h
When i lived out in CO, the lower octane fuel was an isdue for many turbo/SC cars....afterall they are getting most of the performance, if not all the performance of lower elevations (like with a turbo), but with less wind resistance....
Seeing 85 octane at the pump always made me wonder....normaly asperated fine, but a motor with a blower should do better on more...
(matt, octane ?guy if i remember )did some testing out in CA a few years ago..it was posted online as part of an ic test, and published in a magizine if i remember right....found in warm weather, with 91 octane snd a pulley, timing was pulled a bit...(the computer was doing ehat was needed to protect the motor), but the elevation and cooler temps, my gut says you should be fine.

 

To make the descesion simple...go to your driving style, and car use...
If you like mostly cruise acceleration, the 17% is great....if you expect to track the car, run redline for more than a second (like many autox/track events)get the 15%....the reduced chance of a thrown belt, and better power at redline will likely benifit you.
I read tons, and researched a bunch...then made my choice..i orgionaly was gonna get a 15%, but my mini guy said go gor the 17%, it better for your style of driving....never looked back!!
good luck, and enjoy the high country, it can be beautiful, and some great roads with little traffic. Kinda miss it...did not have a mini back then....had a crx for the twistie. Basic car, but a blast.

 

For thr inconsistant boost...many cars have the spring in the bypass valve fail.


It vents the sc till the vac gets high enough to shut it, increasing mpg by making the sc drag nearly zero at idle/low rpms when boost is not needed...
Heat soak is also something some folks feel...like when you are at a light for a few minutes, then floor it...the ic postion gets hot....goes away in cool weather...the stock ic gets hot fast, but cools fast too....the boots (rubber) that seal the ic to the piping can get hard...resulting boost leakage too.

 

Found this:
https://www.northamericanmotoring.co...em-vgs-19.html

which details a VGS mod and talks about a Detroit Tuning BPV. seems like the DT BPV is a worthwhile approach.

 

I put a 17% pulley on my car. For the kind of autocrossing I do, it's great. I run with a local Miata club that likes to make very tight courses. I can leave the car in 2nd gear (I have the Getrag) through the whole course, save for a few REALLY tight hairpins, and even then, I seldom do it: 1st gear wheelspin guarantees tire sublimation.

On the highway, I don't need to downshift to 5th to pass most cars, either. I think the car is running a little lean towards the upper end, though. I tend to get some pinging past 5,000 RPM. I have programmed my UniChip accordingly, but it's looking like I need to call some time off work to install those Helix 450cc injectors I have sitting in a box at home.

 

I have hit the rev limiter where the ECU cuts fuel at about 7100rpm. I did it once, not realizing I was in the wrong gear and am thankful there is a failsafe for when I'm not paying attention.

 

I won't inquire regarding the nature of the distraction...

You weren't in Vegas, right?

 

I consistently hit the redline at the race track and the car seems to enjoy it. that little engine can rev higher than you think. I've done some engine mods and had RMW tune my car a couple times which included raising the rev limiter.

 

I hit the rev limiter a whole bunch. That's what it's there for, to keep your engine out of trouble

 

Let's just say I've attended a few AMVIVs.

 

8150 is the absolute max the factory ecu can be set at in the programming.
my factory bottom end has seen 8500 on a stand alone ecu.
only changed the rod bolts.