RX 4 Speed

guys... just have a question for you all. I've heard both responses to whether or not it is actually good for our car's engine to be revved up when driving. Will the life of our engine actually LAST LONGER if it is revved up often? and if so, how often and how high? I mean, in spirited driving, I probably try to shift at 5k, but how often should I be doing this? 1x a week? 2x week? and how high for rpm's? I heard that the apex seals will actually get brittle and a big reason for them failing is because we "baby" our cars too much... which is true? thanks for the help.

BLKTOPTRVL

For the first few years I owned my 88, I revved the hell out of it at all chances. It seems to have survived well.

Mahjik

iTrader: (1)

Shifting at 5k?

As soon as my temp reaches 180F, I have no problems seeing 8k+.

badinfluencemp

i have heard nothing about this but with that said it wont kill it to get on it every now and then but dont go out and dog the **** out of it dont race stoplight to stoplight everywere you go. My engine lasted all 11 years i just got a stage 2 port and polished from atkins back in feb and my car was raced alot b4 that, but im no pro in this matter just stating my opnion. I say **** it drive it like you stole it. its an fd every where i go i like to put the fear of god in a honda owner.

broken93

If those revs drop below 5k at any point during your commute, you're wasting a perfectly good 13B.

95R2-89TII Ground Zero

your supposed to rev the car, and run heavy throttle occasionally to "burn the carbon" out of it...or so the porsche dealer told my mom when she bought her car.

RotorJoe

The only thing I heard is that if you baby the car (never rev over 3000) then you may have a chance of too much carbon build up and could cause issues. So they say rev it and drive the car how it should be to blow the cabon out. I don't think this is as big of an issue with turbo cars, but NAs you must rev it out sometimes.

Other then that 8000 rpms shifts all day long.

skunks

i totally agree, there is a reason why the red letters on your tach are so high, i mean your not driving a V8 or anything like that so you dont gotta worry about anything comming apart unless your boost is out of wack. as long as you warm her up to at least 180 and have boost at 10psi or are tuned for higher boost, rev it up, its good for you and your car

the only time id say its not good is if your in rain, snow/ice, or gravel unless you like sliding around

RX 4 Speed

8k rpm shifts??? Doesn't the tach red line at 7500???

Yeah, that's what I heard from most folks too... once in a while, you gotta rev it up. What rpm do you guys usually shift at then? I think 5 to 6 k is perfect. And then once in a while, bring the needle close to redline. I think a good balance is what is needed. Not excessively pushed, and not excessively babied. Wouldn't you all agree? I don't want to have blown apex seals because of one or the other...

skunks

for autos yes, for manuals, our revlmits are about 8.5k but i have seen many which have gone above that and have lived to tell the tales

acutally autos can probally go above that but i dont really know very much about autos. in anycase, after about 9k, you gotta worry about your clutch comming apart and cutting your foot off... get a scater sheild for this

jimlab

For the 5-speed cars, the shift buzzer sounds at 7,500. Redline is at 8,000 rpm where the solid red band starts. However, some people are just fascinated with high rpm and they're not aware that their engine isn't making any more power in that range. They'd be faster if they shifted at the proper rpm, but saying they shift at 8.5k rpm sounds cooler.

Engines are basically air pumps. The more air you can ingest and mix with fuel to burn, the more power you're going to make, all things considered. Smaller displacement engines have to turn more rpm to make reasonable power because they ingest so little air during each cycle. Big cube V8s, on the other hand, don't have to turn as fast because they ingest far more air with each cycle.

Forced induction helps in either case, but particularly with smaller engines, because it can help fill in the midrange where the engine wouldn't be pulling in nearly as much air naturally aspirated. This is very obvious when you compare the dyno charts of an FD and an RX-8 which have the same displacement.



Bottom line, if you're not making any more power, there's no reason to make the engine turn faster. High rpm puts more strain on the internals and accelerates wear. Find out what your power curve looks like and then calculate the proper shift points by finding the point at which maximum (peak) torque at the axles in the next higher gear exceeds torque at the axles in the current gear. It's as simple as that.

Beast From The East

That's a great answer, Jim. Now, since you seem to be a lightning rod for controversy, let's see if this thread doesn't degrade into flames before the next page.

Would the best way to figure out those peak torque marks to dyno pull in each gear? Is it possible to get accurate readings (i.e. everyone does dyno runs in 4th because it's 1:1)?

Beast

gotorx7

Years ago I read an article by a long-time rotary engine builder/tuner (forget which one now) that was emphatic that you should never start your engine unless it was going to be allowed to come up to proper operating temperature, and it should be red-lined at least once before you turned it off again.
I've had 12 or 13 RX-7's now, and have lived by those rules where possible
The ONLY motor failure I've had is on an FD, which I suspect was caused by an idiot ECU installer detonating it in the dyno..

BLKTOPTRVL

I get as close to the top as I can. If I don't occasionally hear the buzzer, I know I am not running it hard enough. I used to rev the '79 to 8K, I occasionally revved the vert to 8K, and the turbo has seen 7 too, but I try to stay

XSTransAm

i usually shift around 5 k for daily driving, its a rarity that i go north of 8... but when i do

RX 4 Speed

wow... thanks for all the responses guys. Jimlab, that was really helpful. I especially like this quote from your reply... "High rpm puts more strain on the internals and accelerates wear." Which really makes sense if you think about it. More rpm = more strain. So where did this notion that running it at high rpm is actually good for the engine and the seals? That was prolly never true then... pushing it once in a while to clean carbon is probably the good thing to do...

FDNewbie

iTrader: (10)

As much as I'd like to claim the same...I dunno where/how you guys accomplish this.

When I get some open road, I'll rip her thru 1st and 2nd, but that's about it. I CAN'T afford to redline 3rd, cuz by then 1) the exhaust has attracted the attention of every cop in a 5 mile radius, 2) I'm well over double the speed limit on almost every road in my state, minus the highway...but it doesn't matter, cuz 3) anything 20mph and over in my state is a reckless driving, ie 6 points, a few days in jail, and license suspended for at least a month (even on a clean record).

I do redline her every now and then thru 3rd, but that's when I'm in the "I don't care, I'mma have my fun" moods...but they gotta be well calculated and few and far in between (simply to help the odds of getting caught lol).

Not by choice...but I've seen at LEAST 10K once... There's a red light camera 2 miles before my house, I was in 5th, was gonna drop it into 4th, but somehow by accident it went into 2nd...OMG...sooo bad. Revs flew up like CRAZY, and I smelled (what I thought was) clutch burning. Not good lol

Jim, you're definitely right...not that my word weighs much lol. But I was gonna say the same thing...while it's fun to shift at higher rpm, you're gonna be experiencing some dramatic power loss by taking it to redline, unless you have some huge port and single, that only makes large power from like 5K and up. Otherwise, just as the beautiful graph that Jim posted, the torque curve starts to drop significantly around 6250 - 6500 rpm...

jimlab

Here's what I'm talking about. The same torque curve shown in the chart I posted on the first page for the stock FD is represented in the chart below as torque at the axles calculated as I described.

Note that the dark blue line representing torque in 1st gear does not overlap the pink line representing torque in 2nd gear at any point. That indicates that 1st gear should be held to redline for maximum acceleration.

However, 2nd gear does overlap 3rd, 3rd overlaps 4th, and 4th overlaps 5th. The point at which they cross is the ideal shift point for maximum acceleration. Holding the current gear past that point causes the rate of acceleration to fall off before resuming again at a higher rate after the shift.



Note: Speed was calculated using the stock P225/50-16 tires at the same rpm intervals as the torque measurements, and represents gear-limited top speed only. No wind or rolling resistance calculations were factored in.

RX 4 Speed

wow... I have learned so much about my car that I never knew. Jimlab, where the heck do you get all this info? You work for Mazda or something? jk. Seriously though, so looking at the graph, for maximum acceleration, you would want to redline first, then shift to 2nd, then shift to 3rd at ~70mph, then shift to 4th at ~100, then etc... etc... I see.

Although, don't mean to change the subject, but all in all, as my original post states, all this is still BAD for the engine right?????

SteveF

Driving your car how it is supposed to be driven isn't going to hurt it. Hitting 8000 RPM in an FD isn't going to hurt it. Yes there would be slightly more wear at 8K RPM than at 3K RPM, but who cares? I doubt if you have an engine failure on an FD it's going to be from wear.

As long as you don't drive like a grandma all of the time I don't see carbon buildup being an issue. If you do drive like a grandma all of the time I can't imagine why an FD would be your choice car in the first place.

Steve

jimlab

Not quite. The chart was just for illustration and mph was used to show where the torque curves intersect as the car accelerates. As I stated, the mph will not be exact, because of rolling resistance, wind resistance, tires not being perfectly circular in shape when loaded with the weight of the car, and so forth.

RPM is what you need to know, and as you can see, each line intersects with the line for the next gear midway between the last two data points. Without getting into the math involved, those last two data points represent 7,500 and 8,000 rpm respectively, so you can estimate the proper shift point just by looking at the graph.

For example, the yellow line representing 3rd gear passes through the pink line representing second gear at just about midway between the last two squares representing 7,500 and 8,000 rpm. Therefore, the ideal shift point would be about 7,750 rpm. The light blue line representing 4th gear passes through the yellow line between the last two triangles also, but it's closer to 7,500 than 8,000. The ideal shift point would be about 7,600 rpm, give or take.

The point is, you are not necessarily accelerating the quickest by holding a gear all the way to redline (let alone beyond).

neit_jnf

iTrader: (17)

Hey Jim, I got this graph from the Cartest2000 program. It's in Force (lbs) vs Speed and it's very similar to yours but according to it all gears overlap at the end...

Sled Driver

iTrader: (9)

You have been watching too many Castrol oil commercials............

Let me see a show of hands of people who have "worn out" their engines??? Anyone????

OK, how about water/oil seals? Boy, I see a bunch of hands.......

Now apex seal due to ping'in, lean conditions??? All the rest of you.

Rev away my man, life is too short, like the quote above states, go for it.

If your concerned about wearing your engine out, you'll never use the car to it potential. (buy a civic)

Now if IM just repeating what everyone else said, sorry. I didn't waste my time reading every reply, just scaned the 1st page.

jimlab

I have CarTest 2000 also. Note that each gear still ends at the same speed as the gear-limited speeds shown in my chart, including 5th gear peaking at 201 mph. Obviously that's impossible for a stock FD under real world conditions. I stopped using CarTest primarily because the aerodynamic calculations are inaccurate or ineffective.

The difference in torque curves can be attributed to the estimated curve that CarTest 2000 generates if you enter only the peak value and rpm, and the smoothing it applies. My values were taken directly from an actual dyno sheet for a stock FD.

neit_jnf

iTrader: (17)

I agree the program overly simplifies things in it's original form but you can build a custom power curve and have the program calculate the rest, also all the drivetrain, tire and aerodynamic losses can be changed. Notice how the imaginary car can't go past ~162mph because it's power matches the losses? I'd think it is a very close aproximation for a stock FD. I like playing with all the different parameters and see how the estimated ET and trap speed change.

Now back to topic, I redline at least once evry drive to help keep the engine clean and the plugs from fouling. Also I like to excercise the secondary turbo once in a while, I don't want it to quit working for lack of use.