Redlining: How bad is it really?

[Hangman]

Would be the same for any engine. If you redline it all the time, you'll start breaking stuff, as said above. But now and then shouldn't hurt it.

Also, as above, optimum power usually isn't found at redline, but before it.

 

[azazeldeath]

If you want to find the power band of your engine do some google searches for dyno sheets or stock, or near stock versions of your car. It wont give you an exact read, but it will give you an idea. Some cars peak very soon in their power.

 

[tHe_sTiG]

I know that it's a different motor, however my owner's manual for my Ecotec says that occasional redlining is not an issue, but constant driving at redline for extended periods, ie: holding throttle to the floor and letting sit at redline, may cause engine damage. (Or words to that effect)
So I would say the Alloytec should be the same?

That would probably apply to all engines. I suppose a more suitable phrase would be "it would shorten the life of the engine". I'm sure beyond the red line for extended periods is definetely not good, since the engine wasn't designed to handle such loads.

Cars have an optimum power band and you will find it's often a bit below red line.

Engine specs for VZ Commodore states: Max power: 175 kw @6000 rpm. So I'm guessing, the redline is either at 6000 rpm or slightly past that.

 

[heyitsEnricoPallazzo]

Redline for 175 with 4L60E is 5500rpm. Cut-out is 6100rpm.

 

[Hangman]

^ Mate everytime I see one of your posts with your username and avatar I laugh. I love those movies.

Ok, carry on.

 

[tHe_sTiG]

Strange that the engine would allow itself to go beyond the rev limit. Shouldn't the shift point then be at 5500 rpm?

 

[tHe_sTiG]

Hey guys! After much researching I managed to come across this site. Most of the information is greek to me, but I managed to find what I'm looking for. Might be of interest to some of the modders out there.

http://www.strokerengine.com/StrokedEngines.html

Here is the rule of thumb. Figure out the piston speed in feet per minute. (stroke X max rpm you want to run,devided by 6) never go over 3500 feet per minute for stock engines, 4000 feet per minute for modified engines and 5000 feet per minute for all out race engines. example, a 4.25 stroke length stroker motor should not go over 5600 rpm for a modified engine.

Safe rpm = (3500 ft/min x 6) / (85.6 mm x 0.03937) = 6231 rpm. About 6200 rpm.

Understand Stroke Limitations and Piston Speed
There have probably been more stroker motors built in the last 10 years than there were in the previous 90. The proliferation of inexpensive, stronger-than-stock cranks has brought an entry-level stroker kit within almost every hot rodder's financial reach. But there are limitations as to how much stroke can be used. Any time stroke length is increased we either have to accept increased piston/rod accelerations (and therefore loads) or a reduction in redline rpm. For the most part we can calculate about where to set the engine's redline rpm from a given mean piston speed. The formula is simple: Mean Piston Speed (feet per minute) x 6 divided by the stroke in inches. Fig. 1 shows the formula and an example.



Figure 1
Calculating Maximum Safe RPM

Max. Safe RPM = Mean Piston Speed (ft/min) x 6
Divided by Stroke in Inches

Example for a budget aftermarket forged crank in a 4-inch stroke small-block Chevy:
4,800 x 6 = 7,200 rpm
4

Maximum Mean Piston Speeds for Above Formula:
Factory cast-iron cranks 3,750 ft/min
Aftermarket cast-steel cranks 4,500 ft/min
Factory forged cranks 4,600 ft/min
Budget aftermarket forged cranks 4,800 ft/min
Typical race aftermarket cranks 5,500 ft/min
High-dollar custom endurance race cranks 6,000 ft/min
ProStock/Mountain Motors 7,500 ft/min
Formula One 7,500+ ft/min

Max safe rpm = (3750 ft/min x 6) / (85.6 mm x 0.03937) = 6676 rpm

Going by this method, we could say the max the Alloytec can tolerate before crapping itself is about 6600 rpm. Quite a realistic figure, considering the Alloytec 190's shift point is set at 6500 rpm under full throttle.

 

[heyitsEnricoPallazzo]

As stated earlier. The 175 is limited by the 4L60E tranny (claimed). Thats why it has a lower cut-out.

 

[VzVzVz]

Weather its a manual or auto, the limiter will stop the engine revving any higher. Unless you manage to accidently grab 1st at 100kph, then I'm sure something would go bang

 

[tHe_sTiG]

Weather its a manual or auto, the limiter will stop the engine revving any higher. Unless you manage to accidently grab 1st at 100kph, then I'm sure something would go bang

Yes, that is the sort of problem to worry about. Auto trans would eliminate that problem, seeing everything is electronically controlled. Manual trans, don't get over-excited and shift properly.

Other than that, it seems letting the car stretch its muscles once in a while can be good. Get rid of all that crap that gathers inside there.