Interesting, but troubling series of events!

No, not the lights. After I returned to my bright white gauges, I went to grab some grub.

On the way there, I was getting the run up from (what I later found to be) a 2000 Camaro (or Trans am forgot to look closely)

So I have a Weltmeister chip...and I haven't really explored every element of it since I put it in...

Anyway, we were both doing 40, and the kid wouldn't let it go, so I dropped to 2nd and we danced. I pulled and remained ahead of him.
Now he followed me into In-N-out drive through and pulled along side to chat a bit and ask the year of my machine, only to be stunned by my response: "84" and I likewise learned his machine a 2000 with 325 horsies ....but
Here's the problem.
I've always let my rev limiter guide my shifting. When it ticks off and stalls out, I shift. This used to occur somewhere in the red band way before 7k.
During that crunch this DID NOT Happen. It went to 7k and *I* just let off the gas half panicked, but it gave no indication of limiting itself at 7k and maybe over.

I know the chip adds 500 rpms...but is it possible they flubbed it and disabled the rev limiting completely? Does anyone have a similar experience or knowledge? I'm afraid I'll blow something if I do that again.


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Kurt B
1984 911 Carrera Cabriolet
75 914 1.8

Firstly, you may very well have lost your rev limiter with the chip. you should call the supplier and ask.

Second: You are slowing your car down by going all the way to the limit. Your car probably stops pulling hard around 5900, maybe 6200 if not sooner. You should then shift to put the car back into the "power band" of the RPM range. Of course while your WAY up there in the RPMs (and losing power) and then hit the rev limiter, your timing gets dumped and the car totally stops accelerating for a moment, much like an extra shift. You would be amazed how much quicker your car would be if you shifted just a little sooner...

Kurt,

Viprklr is correct. Many people feel that horsepower is the ultimate way to go faster and completely forget torque. Take a look at the specs on your motor and see where max torque and HP is go from there. Ask any drag racer and they live for torque...

Going higher in RPM will do no good if the max HP peaks out well before redline (or when the limiter kicks in) and when you hit the limiter and it shuts off the power to the fuel pump your motor falls flat on its face for the next gear.

If you are not sure if your chip has the correct max RPM limit in it, I would ask the supplier for another chip, or put the old one back in it and send the performance chip back to them to make sure. This is not an area to guess, especially if you are using the "burp" of the limiter to shift!

JA

Kurt,

The advice about shift points is correct; you want to shift at the max torque point, not the redline.

I have a Autothority chip in my '84 Carrera. Autothority raised the redline by 400 RPM over the OEM chip. The new rev limit (approx. 6850 RPM's) works in my Autothority chip; tested it on the track one day. Therefore, you should check with your chip manufacturer and find what the new rev limit is supposed to be. You could have a defective chip.

Regards, Bruce

2 points.
1) I also have a chip in my 87 and have found the same rev-limiter phenomenon. I can't figure if the tach is slow, or the limiter is north of 7K.

2)With the wide spacing in the 1st 3 gears on my G50, and the relatively narrow powerband on the 3.2, I find it alot quicker when I stay in it till 7000. If I shift at 64-6700, I drop momentarily out of the power.

There's also the idea of inertia.

I don't trust my tach until maybe 3rd gear on hard acceleration. I have literally seen the needle jump up when I clutched and given a little throttle blip that didn't take the car over 4000rpm - and that needle appeared to go *past* the 7000rpm range.

If you blip the throttle, or are accelerating hard, sometimes the inertia of the needle itself will overpower the magnets inside the tach, and it will continue swinging up even though a fraction of a second ago you let off the throttle and the engine has spooled down some.

Kurt: Camaros are tasty for lunch, aren't they? Mustangs are pretty yummy too.

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Mark Szabo
1986 911 Targa 3.2
1987 Escort 5-speed 1.9
The 911 Gallery

The inertia theory is a decent one except that, prior to the new chip, it cut out normally under the same kinds of conditions...I won't risk testing it again, but I'll write weltmeister and see what they have to say about it.
Oh, and a bit of information on the Camaro, there were a couple of girls in the back seat.
If you put a couple of girls in the back of my car, it would have been a different story!
Which reminds me of one of the advantages of having Asian fever--most of the girls I have in my car are under a buck!

All that aside, he began the race right in the middle of my sweet spot: 40mph, dropped into 2nd.

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Kurt B
1984 911 Carrera Cabriolet
75 914 1.8

I have an '85 with the Weltmeister chip. Mine cuts out around 7K, not sure exactly where tho. I only expereienced the ignition cut-out while auto-crossing in 1st gear. I never could get to red-line in 2nd gear at the auto-cross. I always had to brake before then.

Good luck
Nick

If you're hitting redline in 2nd gear while autocrossing....

...that's one HELL of a big course!

Kurt, you're probably right. Keep in mind it's not the acceleration overrevs that kill an engine, it's the mechanical ones that happen when you downshift into 2nd when you wanted 4th. I understand that stretches the connecting rod bolts, and that detorques them, causing wear and eventual failure and a case ventilation. Per B. Anderson in this month's Excellence.

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Mark Szabo
1986 911 Targa 3.2
1987 Escort 5-speed 1.9
The 911 Gallery

Old Skul,
I read that article too and I thought Mr. Anderson did not answer the question he was asked about the chip raising the rev limit.
He said “if you over-rev your engine, you run the risk of stretching your rod bolts” and later “The related risk is dependent on how much you over-revved when you missed a shift or whatever else happened to exceed the rev limit.” I am bring up the “whatever else”
I realize that a chip only raises the limit about 7%, I just thought the article avoided the question.
Comments please?

Best regards -Andy

I found the limit tonight racing around once again. This time, not paying attention, it topped out at around 7k. So, not worry. It's possible that last incident was a misreading as Mark suggested...it was probably lower than the gauge read at that instant I looked.

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Kurt B
1984 911 Carrera Cabriolet
75 914 1.8

Didn't see the article, but I'm guessing we can get 7000 even with our rev limiters, whetehr its due to the needle inertia effect or whatever. I too experienced the 'miss' at the top of first at autocross, so I know my rev limiter is working, and I don't worry abou tit. I mean about 'it.'

You guys are funny. Sweet spot. I just drive a lowly SC (try me) but I can imagine the foolishness of dancing with a Carrera that is cruising just inside the lower tip of its power band.

I am occasionally reminded of the HUGE role weight plays. Hauled a few Christmas presents home today. Big difference.

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'83 SC

Bruce didn't mention the rev limiter in this month's Excellence. He has mentioned it in past articles - and other authors have concurred with him - on the subject of rev limiters and mechanical overrevs. This month's answer to a reader's question was on the rod bolts.

I still haven't found the rev limiter in my car. I'm afraid to. I get visions of those 9mm rod bolts stretching and then one day while on the highway hearing a loud clunk followed by a stream of smoke and live oil behind me. And I have a non-stock chip in it that the DPO (dreaded previous owner) installed and who knows what it is. I should pull my DME and find out, but I'm afraid that I'll shock it or something with static electricity and blow it up. I'm such a wuss, sometimes.

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Mark Szabo
1986 911 Targa 3.2
1987 Escort 5-speed 1.9
The 911 Gallery

You ought to pull it Mark. It'll take just a few minute to unbolt it and take it apart. For my part, my board had obviously had at least one Carl's Junior spilled coke incident. I could see on the board the remains of some wetness!
I kept my stock chip. I was definitely determined to have the new chip, as my original chip was soldered in, and Weltmeister recommended leaving it alone in that case (my carrera is number 199 of the line, produced in 1983, so made before Porsche considered chip upgrades as a future option), but I got a desolderer at Radio shack and carefully removed the old one. Decided to have an someone solder new one in for me, and she fired right up after that.


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Kurt B
1984 911 Carrera Cabriolet
75 914 1.8