Rev Limiter...

[Hit an Apex]

Quick Questions,
A. At what point does the rev limiter kick in?
B. How does it kick in, i.e. does it shut down the engine or limit it? I know on the Champ Cars once the engine hits the rev limiter its limited, and sorta "bounces off it"..
Thx

[JoeCab]

The rev limiter in a 2.5L Milano kicks in at 6,400 with a pretty definite bang, not a subtle bouncing. There are actually 2 - one in the ECU shuts down fuel, and another in the spark box cuts out spark.

Joe

[Hit an Apex]

So it shuts the engine off or slows things down?

Thanks.

[papajam]

My understanding is that it shuts things down until the engine drops below the limiter setpoint then the engine kicks on again. Would make for a pretty rough ride in the lower gears I'd think.

If you're into a little electronics work, the rpm limit can be changed on the limiter.

[BlackAlfa]

I got to learn and experience this rev limiter thing some 15 yrs ago in my 2.5L while overtaking another car in the opposite lane on a 2 lanes country road. I believe I was in 2nd gear and was about to go to 3rd.

Basically, engine cut out (due to fuel cut off) and lost power for perhaps a second or so. Then it came back (when the rpm dropped).

Well, since then I have learned not to push it so close to the limit !

Bob

[JoeCab]

Quote:

I got to learn and experience this rev limiter thing some 15 yrs ago in my 2.5L while overtaking another car in the opposite lane on a 2 lanes country road. I believe I was in 2nd gear and was about to go to 3rd.

[Mezevenf]

When I hit in 1st it just reared up oddly and then I shifted to second and the power came back.

It happened rather fast and that was my first night driving on my license :S

[italcarguy]

How much is that Pandora's box? Where can I get it? Is the car still pulling at 7200?

[Hit an Apex]

Quote:

Originally Posted by italcarguy How much is that Pandora's box? Where can I get it? Is the car still pulling at 7200?

[JoeCab]

Anthony,

I usually shift my car at 6,800 rpm and yes it is still pulling. I never hit the 7,200 rpm rev limiter in the Pandora's Box, I just like the fact that I am not constantly hitting it like I was with the stock ECU.

The rev limiter is lower on 3.0 Pandora's Boxes, at 6,900 rpm. Basically, when the ECU and Spark Box is modified by Alfa Heaven and Jonathan Kirshtein, they do 2 things:

1) Swap in a new resistor in the ECU to eliminate the fuel rev limiter.

2) Modify something (sorry I don't know what) in the Spark Box to raise the spark rev limiter. I have been told it is not possible to completely remove this rev limiter.

Joe

[carlosvaz75]

I had a 75 TS, and I had the same problem, so I had a chip from EBspares and I had engine till 7000 (the end of the rev counter, and it was so much better, because I used to run it frequently till 6800/6900.

[Greg Gordon]

Most stock 2.5s have 2 rev limiters, one at about 6300-6400 in the fuel ECU and on post 1983 cars an ignition based limiter at about 6800. They are both hard limits which means they shut the engine down until RPM drops.
At my web site we offer an ECU mod which removes the fuel ECU limiter, we don't change the fuel mixture since it's easier, more effective and FREE to do that with other adjustments which are described on my web site.
Greg Gordon
http://www.oldebottles.com once there scroll down to the Italian car link

[75evo]

Guys,

IMHO, don't waste money on Jetronic. Been there done that.

Leave it stock if you are sticking with Jetronic. Or ask Greg Gordon to mod the box for you, he'll save you a ton of money.