Safest/Best/Easiest way to find my engine's redline?
 

So I have a 1982 SC but a 1995 engine from a 993. I also have headers, intake, exhaust and a chip on this engine. I'm not sure what chip, and I'm not sure of the exact hp/tq numbers, but it's definitely quick. Problem is I have no idea what the redline is and I'm not sure the best way to find that out.

Do I just punch it until the fuel shuts off and then that's it? That sounds fun. :-)

I just want to make sure I won't do the engine any damage while doing this.

here's a pic of a tach from a '97 993 -- http://germancarsforsaleblog.com/wp-content/uploads/2013/07/Resized-Dash.jpg

Looks like factory redline is around 6700 rpm?

Be careful of going the fuel shutoff route as chip tuners can remove this limiter -- I'd be wary of going over 7k rpm without knowledge/confirmation that the engine has custom parts to accomodate

Yeah the stock the limit is 6700 rpm. Source: Excellence

Just wasn't sure if I should test that, or just stick with the stock limit. I am thinking about getting the tach redone so the redline matches the actual redline so I wanted it to be accurate. Perhaps sticking with stock is the safest way to go.

i would do like a a second gear pull up to red line. don't floor it and hope it kicks in. slow and steady. I would not go over 7k either.

Why not dino it, find the rpm max hp and torque then call it a day.
Your driving power range is between those two and it generally useless to go much above the max hp rpm. So that would be your “safe” redline.
M2c’s
Johan

Stock '95 max hp is @6100, stock rev limiter is 6700+/-20

there's really no reason to rev past 6500.

There's no telling what the rev limit might be w/ an aftermarket chip, but unless the rods and or rod bolts have been changed. But even w/ RS cams use 6700 as a max.

Lastly the tach is not particularly reliable, it generally lags the true rpm by a few 100

Doing this on a dyno with someone that knows what they are doing is the safe play.
As previously mentioned you don't know how that chip is setup. Pair that with the other mods and you could most likely figure it out safely. However if it goes wrong it could be an expensive mistake.

Anyway to get into the chip with some sort of eprom reader and determine the values? I'm sure that is possible but I haven't any clue how or who could do it. Maybe dial up your favorite performance chip supplier and ask if they could do it.

I can't imagine that any tuner would completely remove the rev limiter and I would also think that they set it to a value that wouldn't be out of the limits of the motor it was made for but I guess it could happen.

That being said, I've never owned a car where I hadn't found the limiter within the first few days of owning it. I have my 3.0 limiter set to 7100 and hit it almost every time I go for a fun-ride. Don't be too scared of it.

Took it for a spin today and hit 6800-6900 and it never cut me off. I backed off after that as I was scared to hit the 7k mark. So the factory limit has definitely been raised.

Maybe I'll try the dyno route.

Thanks all.

that's weird.
I have a sc with a 95 3.6 as well, I hit a hard red line around 6800RPM. same mods as you.

Wait, isn't red line set by calculating a safe RPM based on a build sheet of components and strength?

Are you looking for the RPM where it runs out of steam, or there theoretical limit that can be calculated before it explodes?

(sometimes a weak engine can't pull redline, and other times a strong engine can surpass it and break)

Well maybe our chip setup is different? Guess I'll have to try again. :D

I was just wondering what my particular car's redline was. I wasn't looking to increase/decrease it...just curious. Just wanted to make sure I was finding it safely. :-)

What if you engine revs past red line? What if your rv limiter doesn't limit it at red line?

I would set a red line for myself based on advice form those in the know, and then if you want, rev it up to that. If you don't hit the rev limiter, be aware that you need to be careful or, recalibrate the rev limiter

ultimately, think Bill V's advice is spot on -- the weak point on these engines is the connecting rods/rod end bolts. Unless you know these have been replaced with more robust / $$$ parts (e.g. carillo and/or arp), stick with the factory redline to avoid unduly stressing these.

this!

You mean besides spontaneous disassembly?

I never looked to my tach in a car or on a motorcycle I was familiar with as my ass, ears and good sense would tell me when the pull stopped, so then I shifted. if you don't have the engrained feel for a motor you are accustom too and are looking to a tach or a rev limiter to find it's limit I might just call you a fool. and suggest you gopro future "events" for our further evaluation.....

go to a track and find the useful power you are capable of summonsing and twist your tach back around to where you found it..

Yea, I never look at my tach either. Funny, though, I sometimes will hit my limiter when autocrossing........

I have a 1973 2.7 MFI. redline is supposed to be 7200.

I used to have a rotor with a counter weight in it that was supposed to shut down the ignition completely at this RPM. It did work well, but a complete shutdown of RPM that is a grounding of the ignition is like hitting a wall. Pretty crude in my estimation.

I took out the crappy Bosch CDI and installed a Daytona-Sensors CDI with coil and most importantly a soft rev limiter. I set it for 6600 RPM and can just rev up to it and know I am not going over 7000, and it does just start missing at 6600 RPM.

I am just not interested in 7200 RPM, especially if it limited by a mechanical set up.

I trust the Daytona-Sensors CDI and it has worked perfectly of 10 years.