Just a question, tried for a search but nothing..

For a -74 1.8l when is time to shift?! it sounds like my engine does not like high RPM's.. or is it just me?!

Right now the highest I have gone is 3800-4000..

usually around 3000 is when I shift..

any advice would be nice...

also a short shift story, what speed/gear/RPM are you at.. for you guys with the same motor..

thanks!

QUOTE (cbenitah @ Feb 7 2006, 10:30 PM)

Right now the highest I have gone is 3800-4000.. usually around 3000 is when I shift..

that seems low ...

max. HP is at 4800 for the EC and 5000 for the AN ...

Andy

QUOTE (SirAndy @ Feb 7 2006, 10:33 PM)

QUOTE (cbenitah @ Feb 7 2006, 10:30 PM) Right now the highest I have gone is 3800-4000.. usually around 3000 is when I shift.. that seems low ... max. HP is at 4800 for the EC and 5000 for the AN ... Andy

yea i know... I saw a post that said the car is alot better at 4500 ish.. hmm.. maybe i should go out and try it

5800

miles told me a long time ago that I should TRY to keep the car above 3k rpm's. The fan on the engine needs to stay that high to keep the car cool...

I generally kept it between 2500 and 3300rpm's.

that was a while ago..

Oh and I shifted at like 4800 cus my engine didnt like revving (cept once, right after a valve adjustment... twas nice..)

I shift when the valves start to float or after teh apex, whichever comes first

When I hear the valves float, I put my hand on the shifter...

When I hear a funny knocking sound, I count to ten... if I don't hear the 'tiny metal hammer' sound by the time I count to 15, I go ahead and shift anyhow.

Where is peak horses on a 1.8? Shift 500 above that, and cruise in any gear at around 2/3rd of that range.. you know, give-or-take a teeny.

If you find yourself under 2700, start looking for a downshift, at least, or lug it.. and lose it. It adds up.



M

I shift when metal parts spit out of the exhaust.

is that bad?

actually I shift at 5000 usually, unless i'm pissed off, then i'll double clutch it at 6000 (it doesnt like that much)....

b

Hmm, Street driving 3000 to 3200 light acceleration not racing nobody.
Autocross 5800 with barely a lift off the gas. I will rev it past that if I can save a shift and make it to the next feature. about 6800. But I'm balanced with dual valve springs yada yada.

QUOTE (cbenitah @ Feb 7 2006, 11:30 PM)

For a -74 1.8l when is time to shit?!

I think you came to the wrong place for that question....

QUOTE (Demick @ Feb 8 2006, 09:34 AM)

For a -74 1.8l when is time to shit?!

When the front end passes the back end on a winding mountain road with a dropoff on one side, a sheer cliff on the other, and an 18-wheeler coming the other direction.




But it is very hard to clean out of the basketweave.

Stock motor, normal driving--I try to keep the revs around 3000-3500.

AutoXing or trying to wring all the performance out of it I can--I shift between 5000 and 5600. Usually higher in the lower gears (except first; I'm never trying to get all the performance out of first gear!) and lower in the taller gears. For instance, I shift from 4th to 5th at about 5200 RPM, while I shift from 2nd to 3rd at the stock redline of 5600 (or, sometimes, when I hit the rev limiter).

--DD

QUOTE (Dave_Darling @ Feb 8 2006, 09:52 AM)

Stock motor, normal driving--I try to keep the revs around 3000-3500. AutoXing or trying to wring all the performance out of it I can--I shift between 5000 and 5600. Usually higher in the lower gears (except first; I'm never trying to get all the performance out of first gear!) and lower in the taller gears. For instance, I shift from 4th to 5th at about 5200 RPM, while I shift from 2nd to 3rd at the stock redline of 5600 (or, sometimes, when I hit the rev limiter). --DD

Funny... I thought you shifted after one of the rockers breaks........

agree with DD on this, normal driving you should shift around 3000-3500 or so. I think of it this way, at freeway speed I am running about 3500 rpm (varies with tire type) So thats about the max rpm I need to travel. To get up to freeway speed, any engine rpms higher than what I ultimatly need on the freeway i consider wasteful of fuel, and engine wear.

technically I suppose you coulod shift at or near the redline (5800 or so) however that will waste gas,a dn result in more engine wear/heat. It could kill a sick engine pretty fast also.

Now if you are racing or such, then gas use, and engine life may not be as big an issue, so you can accelerate faster with higher engine speeds before shifting, there is an optimal set of shift points for racing, but that would depend on your enigne torque and final gear ratio. The optimal shift point may not be the redline either, but goin g to redline is probably most wasteful of gas, and hardest on the engine, as is the opposite extreme of low low rpm lugging (1200 rpm or so0 again dependent on the engines torque curve.

The factory torque curves are printed in the owners manuals (the glove box sized book that came with the new car) You can look at it and find the optimal stock set up shift points based on torque (road slope, cargo wieght and such will change these numbers some)

Stay within the 3000-3500 limit and you can't go wrong, it is high enough to not lug the motor, and low enough not to over stress it.


Nice thing about these old aircools is you can hear them so well, you can shift without the tach by all the racket. Get in a smooth sound deadened new luxury car and you can barely hear if the nmotor is running, much less how fast it is spinning.

If you aircooled starts getting more loud, it's time to shift! 4000 rpm is loud enough for me, i can hear it, it sounds much more buzzy than 3000 rpm, good audio feedback on the 914!

Usually after a good cup of coffee in the morning...

From a physics point of view, it is a waste of Entropy and that is BAD, if the engine RPM exceeds that which you need as your max rpm at cruising speed in top gear? I think entropy would be consumed just from the fact pistons and cranks and such are moving at a higher peak velocity than otherwise would be needed., plus the acceleration deference in the cars enitre mass. ie I can get onto the freeway and cruise at 70 mph and never exceed 3500 rpm from start to fifth gear. that uses less entropy than if I get up to freeway speed faster by running up the rpms before shifts.

More energy is spent, entropy destroyed, and entropy we all know is a limited resource, when its gone its gone. At least 914's by their virture of a small relitive mass to the other cars, provides a conservation of entropy, a side benifit of limited crash protection.

Less entropy destruction will lead to longer engine life. And this can be shown by a cylinder head temp (CHT) gage. with one you will notice considerable instantanious temp increases when you put the peddle to the metal and race off fast revving it up. You can keep the head temp tens of degrees cooler by shifting at moderate 3000ish rpms. There is plenty of stuff on head temps and head life out there, so I say not more on that except cooler is better (if warmed up) for engine life. An oil temp gage would not detect the sudden quick head temp changes, so don't bother to use one to prove this, you'll melt your heads first trying to.

its twisted, but true. save entropy, and save your engine. folks that want to race or go fast don't worry about entropy as much. higher quality parts, build, and maintenance of an engine can help combat the ill effects of excess entropy destruction Its all physics.

5-5400

Or when I feel the valves float.

Rich

If I was worried about whatever that is ENTROPY ? I would still have my 89 Dodge Aries K car.

I have a Sports car which means I must go fast, As fast as possible. Plus I have spares, engines, transaxles brakes and the where with all to repalce them when I want.

So wring it's neck and go like hell.

That's the spirit "End entropy drive fast", I like it! just remember good parts, and maintenance for the most thrills per engine

Everyday stuff 3500-4000. when I mean it...when the rev limiter starts to "rattle"........

Currently im in 5th after 30mph, and I shift at 5.8 when I want it to GO..

but thats a sbc for ya.

QUOTE

Just a question, tried for a search but nothing.. For a -74 1.8l when is time to shift?! it sounds like my engine does not like high RPM's.. or is it just me?! Right now the highest I have gone is 3800-4000.. usually around 3000 is when I shift..

I'm just curious though, do you feel the power increasing once you get into the 3800-4K RPM mark? Doesn't it make you want to continue letting her rip up to redline? If power is dropping off at 4K RPM you have a problem that should be looked at.

i think the key is to have your engine in it's power band as much as possible if your doing on-ramps or A/X. If not, just cruise at lower RPM's to conserve everything. even entropy....

when it misses,

mike

QUOTE (ClayPerrine @ Feb 8 2006, 08:03 AM)

Funny... I thought you shifted after one of the rockers breaks........

Oh, I thought you meant when I shifted gears in my own car, not someone else's!!







[QUOTE=dmeche914]From a physics point of view, it is a waste of Entropy and that is BAD, if the engine RPM exceeds that which you need as your max rpm at cruising speed in top gear?[/quote]

A waste of entropy?? Come over here so I can slap the stupid out of you!!! If that's what you got from your physics textbooks, you really need to go back to school.

--DD

QUOTE (rogergrubb @ Feb 8 2006, 09:04 PM)

i think the key is to have your engine in it's power band as much as possible if your doing on-ramps or A/X.  If not, just cruise at lower RPM's to conserve everything.

thats it Roger. I work with the load requirements. I love on ramps. And off-ramps, too. I thnk if I could keep my foot out of it, just dealing with trafffic to work (15 miles about), so I could keep all my driving to just 2200- 3500 rpm, I would get great mpg, and the car would do it fine, but I'll bet I would get carbon build up and foul plugs. So to avoid carbon build-up, and b/c there are some fun curveymountainous roads around here, I make sure to wind it on up for a few minutes of continueous hard driving at around 4500, and winding on up to about 5400 before I shift. The car just loves it! It takes on a real sense of urgency- that flat four is slinging around alot of mass right behind you, and if everything is in tune it goes like a propeller! My engine is a little ragged at like 1500, smoothes out really nicely at 2400 or 2450, and gets eager at 3500 to push right to redline. So I don't apparently have a carbon build-up problem. Hehe hehe.

My engine doesn't start coming alive until 3500. So it's at the 5500 rev-limiter before I shift. I've pretty much decided to tear it down, replace the cam and beef it up for a 7000 redline.

I shift just before it gets expensive. Of course I make sure the car is completely warmed up first.

Entropy issues aside, if you want to shift for maximum acceleration and efficiency you'll want to shift at an rpm high enough so that when you engage the next gear you will pick it up at or just above the max torque rpm. Thus as you start accelerating through the gear you will already be at max torque and will be spinning the engine towards max hp rpm. Spinning the engine past the max. hp rpm can be a trade off of time spent doing this for little to no acceleration gain (natural momentum not mechanically assisted as you are past your peak mechanically assisted gains) against shifting to the next gear at or just above max hp rpm and possibly gaining more mph with more efficient acceleration for that same time. There can be some advantage to spinning past max hp rpm to engine rpm redline as when you shift to the next gear you will pick it up at a higher initial hp level and will reach the max hp rpm sooner. Again one's measured mph difference for the redline rpm shift vs. the max torque-to-hp rpm shift may be negligible and for an endurance race the more mechanically sympathetic max hp shift may be preferrable to the redline shift. In the standard shifter and powertrain 4cyl 914 a 1000 rpm drop between gears is typical. I am not familiar with the 1.8 peak hp and torque rpms, but for the 1.7 this would be 2700 rpm peak torque and 5000 rpm peak hp. I have found that while the 1.7 does not have the overwhelming number values in torque and hp, it reaches that peak torque at a fairly low rpm and seems to have a fairly flat torque curve out to peak hp rpm and so you can feel excellent response and acceleration over a 2300 rpm band, especially with the lower profile 50 series tires. For a car that hasn't got much off the line, I am often suprised how fast this thing can get up to its max speed from cruising at 65/70 on the fwy. John

Up at 7100 when the orange light comes on, down at 5000 when the green light comes on. Its that simple. The limiter is set at 7500 so I can stretch it if I have to.

The stock L-Jet cam profile stops making power at 5000 RPMs, any higher is a waste and you should be in the next gear. Seems to me my powerband is between 2000 and 5000. stock internals, 70k miles on the engine.

Here's how I drive:

When the car is not up to operating temperature (temp needle is not past the "e" on "Temp" gauge) I shift at 3000, 3500 at most if I need to pass in 2nd or 3rd.

When the car is up to operating temp (past the "e" on the "temp" guage) I shift at 4000 in normal traffic. This leaves plenty of powerband for passing. On the freeway I'll shift at 5000.

As stated, the engine won't make more HP past 5000, so why bother over-revving it? especially a boner-stock 1.8...

thanks guys, i'm loving the info you guys are giving me.. as to answer if i feel more power when i shit.. YES! it feels like it has alot more power... but coming from a car with no tach makes my ears listen to the engine.. maybe its b/c its so close behind us, maybesomething else.. but it seams like mine wants to go faster but then screams alot.. when i shift at 4000 it is still pulling but im affraid to break it...

also, im driving 70 in 5th gear.. RPM is showing 2900-3000 normal? as to when im driving 90 (not for long though) it shows 4000

it would be nice to see what speed you guys have and the RPM in what gear if you know what i mean..

maybe I should look into a Porsche 914 Swedish-English translator

If your car does not beg you to push the rpm past 4000 when you want to get on it - you may have a problem with your engine. 4000 is a healthy rpm for a gear change but when really pushing it 5000 should be giving more hp and things should be sounding nice too. If you are not getting more hp at 5000 and things don't sound nice/happy - find the problem before you further damage your engine. With that said, under normal driving conditions, aka transportation, I see nothing wrong with mild gear changes at 3000 to 3500. Jim