When do you guys shift?!, Give it to me! Options

[Andyrew]

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

but thats a sbc for ya.

[Dr. Roger]

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.... (IMG:http://www.914world.com/bbs2/html/emoticons/barf.gif) (IMG:http://www.914world.com/bbs2/html/emoticons/aktion035.gif)

[chilli]

(IMG:http://www.914world.com/bbs2/html/emoticons/biggrin.gif) when it misses, (IMG:http://www.914world.com/bbs2/html/emoticons/rolleyes.gif) (IMG:http://www.914world.com/bbs2/html/emoticons/rolleyes.gif)

mike (IMG:http://www.914world.com/bbs2/html/emoticons/driving.gif)

[Dave_Darling]

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!!

(IMG:http://www.914world.com/bbs2/html/emoticons/finger.gif)





[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

[SGB]

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.

[McMark]

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. (IMG:http://www.914world.com/bbs2/html/emoticons/driving.gif)

[LvSteveH]

I shift just before it gets expensive. Of course I make sure the car is completely warmed up first. (IMG:http://www.914world.com/bbs2/html/emoticons/smile.gif)

[JohnM]

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

[Downunderman]

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.

[Brando]

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...

[cbenitah]

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 (IMG:http://www.914world.com/bbs2/html/emoticons/av-943.gif)

[jimkelly]

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