Raising the safe rev limit on a 3.2?
 

Hi
How do I raise it to 7000-7200?
How much do the ARP-bolts do?

Its done on the PROM when you chip the brain. The PROM manufacture is in control of that element.
Bruce

ARP's are mandatory if you want to spin safely above the stock redline. The stock 9mm bolts are questionable at the stock redline IMHO.

related question: What max rpm is safe on the 3.2 with stock valves/springs without piston contact (ie, floating the valves)?

With stock valve train I wouldn't go over the stock redline. I've heard that the valves will float at around 6800 with stock springs and a 3.2/SC cam.

-Andy

But the Carrera Clubsport has the redline at 6750 with stock rodbolts?
They have a lighter valve train, but that wouldn't affect the rods, right?

The problem is that I had the engine on the dyno for mapping yesterday and it develops peak power ABOVE 6800.... Had to convince the dyno guy, "Don't pull above 6800!!!"

EDIT: It's a street car not a track car that pulls to redline in every shift.

Magnus,

I have seen too many dead 3.2 cranks that are out of street cars to recommend anything but stock. Try a different timing setting if you can to bring the power band down. Or install ARP bolts.

Cam timing? What can I do there to bring down the powerband?

Doesn't more overlap give you low end grunt? but sacrifice some top end? Its a question

Talk with your cam grinder to see what your options are with the grind you have. They should be able to give you what the limits are.

More overlap lowers displacement/ dynamic compression. This reduces torque and pushes usable power up the rpm band. Less duration and smaller overlap, like an SC cam produces usable power much lower than an S cam. Study the lobe center, timing specs from Wayne's book to help recognize the relationship. Higher timing specs and smaller lobe centers(more overlap) are for the high rpm applications.

You can advance the cam to give more low end torque. The spec for your car is around 1.2mm at overlap TDC. You could go to 1.5 or 1.6mm and lower the powerband somewhat.

If you are tracking the car all the time I'd replace the rod bolts with ARP. You don't have to split the case to do it if you don't want to.

-Andy

OK, I might try to advance the cam, but I think that will be a job for the next winter :)
Will advancing it bring the valves closer or further away from the pistons (euro 10.3:1 compression, stock cam)?

If I open her up for arp rod bolts and stiffer valve springs, is 7000+ safe?

Made my first you tube video :)
http://www.youtube.com/watch?v=mDjeGvaK0gs

I'm always annoyed how puny the sound gets through a camera.

Dyno sheet fo the pull.

http://forums.pelicanparts.com/uploa...1240525228.jpg

What do you know about your motor, cam, exhaust, chip?

Stock 3.2's make peak HP at 6200. There has to be some reason yours dose not do the same. For comparison, go to 911chips.com and look at there dyno stuff.

Did you check your Air Fuel Ratios with your dyno pull.

Euro pistons by them selves would not do this. Cam timing might.

It seems that somthing is not right. :)

Stock internal, OBX headers, 48mm ITBs, Emerald EFI.
AFR around 13:1 up to 5000 rpm then gradually lower to 11.5:1 at 6800.

Hmm the curves cross around 3500 rpm, is that because the test was done in IV?

Cool video Magnus! What is the dyno procedure, full throttle in IV and then clutch in at the redline?

Thanks, John!

Not sure why the curves cross at 3500, or if that is good or bad?
4th is top gear in my car. Yes, full throttle and clutch at readline.


The muffler is a stock -74 Bischof 2 in 1 out. I wonder if I have more power to gain by a better muffler?

Individual Throttle Bodies!

OK, this is not a mostly stock 3.2. Yes, you need rod bolts.

Yes, the stock 2/1 muffler is costing you HP.

I suspect the TQ and HP do not cross at 5252rpm because there are different scales on each side of the graph.

Not sure if the rod bolts are worth if if they don't make a significant increase in rpm-capability. It's a 20000 miles engine, so its very leak free and nice.

With all the work to change rod bolts, why not put in a set of new Carrillo-rods or equivalent? I'd like to be able to take it to 7500 and make good use of s
-cams in the future.


Unfortunately I have to comply to a 95db noise regulations, so many muffler choices are closed.

Also not your typical Foot Pounds to HP graph. It is a euro thing.

6800 is believed to be the safe limit w stock rod bolts. Some have gotten away with higher, some not.

If stock euro pistons, you can not run S cams with them with out having valve reliefs cut into them for clearance.

To spin a 3.2 long stroke motor to 7500rpm safely I believe you have to use race valve springs and cross drill the crank and make mods so it gets oil not just from both ends but from the middle.

Yes, Carrillo rods are a good upgrade for a 3.2 or 3.3 that is going to spin past 7k.

The best.

For fun I looked in my old Bruce Anderson Performance hand book.

They took a stock 3.2, put full racing exhaust, and 46mm Webber's on it at made 265hp at 7000rpm. I assunm this was a US compression motor.

If it is a street car I might be tempted to set the red line at 7k and not abuse it. Race car, no.
6800 should be safe on a race car.

You are leaving power on the table with the rev limit and the muffler so those are now your limiting factors.

As someone noted above, re-timing you cams might add some. I would look at early SC valve timing specs. This might fill in you mid range some and probably not cost you much up top. This might give you more total power under the curve between shift points.

Enjoy.

I might re-time the cams, if there is enough clearance for it with 10.3:1 pistons. I think I will hold of on that until I drop the engine next time and just enjoy it for now :)
I'm definitely leaving power on the table, to be exact 4.5 hp, cause it made 269.5 at 7000.....

Have to research a little if I can find a better muffler that's still reasonably quiet.

The HP difference may be more as you would roughly compair the HP at the extra 200rpm up top against the Hp at where the shift point begins. That is at 4500rpm you were in the 200hp range compared to the 265+hp. Thus, as much as 60hp difference over about 200+rpm of acceleration.

I hear is it difficult to beat the factory 2/1 stock mufflers when it comes to noise suppression v HP. You could add a second pipe to the left side of the muffler and cap it or put a remote valve. This is about 5-10hp at your HP range I would guess.

:)

Second pipe would be on the right side, sory.

I am not an expert buy you got me thinking.

I looked at a gear chart for my 85 Carrera to see what our shift points are.

Taking it to 7k may help the power between the first/second and second/third a bit. I do not see much advantage above that because the HP curve gets more flat at upper rpm and the shift points out of 3rd and 4th are above 5k rpm.

Want to go faster, do the gears and tighten up 1-2 and 2-3.

For example, if we shift at 6500 first to second, we drop down to 3632rpm. On my car if I could reduce this to 4500rpm I would have about 28% more power going into second.

http://forums.pelicanparts.com/porsche-911-technical-forum/464173-gear-chart-85-915-please.html?highlight=gear

;)

My rpm drop is a little bigger than on your car.

http://forums.pelicanparts.com/uploa...1240947032.jpg


I'll take it to the track for the forst time (with this engine) on june 7th.

I figured it out. The HP and Torque scales are different. It's only when they are the same that the curves cross at 5252.

John, you got it.

See post #18 & 20.

Gears my Friend, gears!

Instead of coming in at 3500rpm at 150hp you could be coming in a 5000rpm and 225hp.

It will transform your car.

Good luck at the track. :)