3.0 vs. 3.2

[tijnes]

I recently bought a '73 with a 60K miles '82 3.0 SC motor as a weekend commuter to replace my '78 3.2 so I can backdate it and do rust repairs. I've so far driven about 1k miles in the '73 and although I really enjoy the car (it looks awesome) I'm a little disappointed by the performance. The 3.0 ltr feels like it flattens out at 5K rpm ,most noticeably in 2nd gear, where the 3.2 would really keep accelerating all the way up 6K-7K. Overall it just feels more sluggish. Is this normal or is there something wrong?

[JP911]

A 3.0 in a lightweight car like that should be a blast. Does it have the stock exhaust? If so, a switch to headers or SSIs will make a big difference. Also, check to make sure that you're getting full throttle. To check this, have someone sit in the car and put the gas pedal on the floor while you check in the engine compartment to make sure that the throttle is in fact wide open.

[VaSteve]

I found in back to back driving with a Carerra that my SC was exactly as you described. In fact, the 3.2 seemed almost like a Turbo. Once it got going, I was going way too fast for the conditions. On the whole, I think I like my SC better. It was more useful on the streets to me. Then again, it wasn't a long test drive.

[RWebb]

take a look at the hp vs. rpm plots for both motors

CIS is just not a real sporty FI system

this month's Exclnc has an article on putting EFI on a CIS car.

[RWebb]

take a look at the hp vs. rpm plots for both motors

CIS is just not a real sporty FI system

this month's Excelence has an article on putting EFI on a CIS car.

[sleepy911]

A dealer friend of mine had purchased an 85' carrera and drove it for a few days before selling it to me. Need to mention he drives like he's on fire all the time. Well I dropped him off at home after buying the car and he called an hour later and said he left left something in the carrera and he would drive over to get it. He had told me earlier in the week he believed his stock 80sc was just as fast. He arrived at my house and he was visibly shaken up. I asked him what happened and he told me he jumped out to pass someone at 60 with not alot of room and instantly realized he wasn't in the carrera anymore. He had to nail the brakes and cut back in. He told me that he would have easily made it if he was in the 85.

[tijnes]

From your comments it looks like I'll have to make some changes. It has the SSI with stock exhaust and gets full throttle so that's not it. When I bought it I thought the weight difference between the '73 and '78 would make up for the displacement but that doesn't seem to be the case.

Haven't read the excellence issue yet. What efi system did they use? I've checked out Megasquirt and it looks easy enough to install but that's another $1500. Will this make a big enough difference? I'm not after huge HP or topspeed I just miss the feel I had driving the 3.2.


Martijn

[JohnJL]

I have a 3.0 in my 1971 and its a ripper. There might be something wrong there. The light weight should really show. I easily outrun 3.2s in the twisties and straights. Here's a video of running with 3.2s in Tassie and I am catching up at will...not allowed to pass unfortunately...
First, check everything is OK with the motor...what do the spark plugs look like? Have you checked compression and O2? Make sure your firing on all cylinders, getting full throttle and your mixtures/spark are right.

Once you have a healthy base engine you can go two ways. Given you already have a big backdating project on I suggest bolting on a set of Weber 40IDa30s or PMO 40's. Add SSIs, a flowmaster and you will be a happy guy. 57 idle jets, 180 airs, 140 mains. BPR7 plugs

If you want another project but fun on the way go with Megasquirt. I have a complete setup there I'm not using if you are interested. Be prepared, it takes work. The Webers or PMOs are the easier setup.

hope that helps

[mb911]

I driven quite a few varations. The sc to me felt pretty close to the 3.2 carrera's yes the 3.2 seems like it has a power band but not much more in the way of real world experience. Remember depending on mufflers on the cars it feel (sound ) faster or slower accordingly. Personally I would not change from CIS unless there is a problem with it. The EFI is ok but not a huge difference. My big change of course when adding a turbo

[JohnJL]

[Tom F2]

It depends on which 3.0 motor you have. The small port 930/16 motors (US market 1980 through 1983) are not great, in my opinion. A late Euro motor (930/10) with SSIs should be a screamer. That said, even a small port motor in your 73 should make for a plenty fast enough car.

[JeremyD]

Most people who drive a carrera shift too early. The power band is in 4500 rpms and up where the SC makes more usable power a little lower.

The small port SC engines definitely seem to run out of steam at higher RPM/s

[tijnes]

Good advise all. Compression is excellent, it runs smooth on all six cylinders. I haven't tested mixture yet and will do that before anything else.

I have a set of Webers that I could rebuild and install but that would just kill the gas mileage. This car is my weekend commuter, 200-300 miles each weekend. At almost $5 a gallon that starts to add up. It would be a lot of fun though. What mileage does a "Webered" 3.0 get? If I had more time I could just swap the 3.2 into the '73 and backdate the '78 with the 3.0 and Webers in it.

Back on the slippery slope, I bought this car so I could just drive and enjoy. I should just block pelican on all my computers.

[RWebb]

power expectations vary - you are not gong to be able to satisfy Mark Donahue

In order of ease:
- check the ignition and do a complete tuneup; you already checked comp.; new plug wires maybe & clean all connections, incl. gnds.

- use a stock early style muffler - 2 IN, 1 out - that makes as much power as anything short of tuned stingers (sport muffler)

- you surely have a fun level of torque & low-end grunt -- even a CIS 2.7L gives plenty of that in an early car (I had that setup for a while). IF the above are all ok, then you need to either:

- modify the 3L motor

- or sell it and install a complete 3.2L with the DME

the latter will give you better fuel mileage than the stock Carreras, so you should be in good shape.

I have not yet read the EFI article.

The more power you try to wring out of an EFI system, generally the more it affects driveability or fuel mileage, etc.

There are exceptions - when combustion is improved (DME vs. CIS; direct injection vs. "indirect") everything is improved.

OR you can live with it or put on your carbs (if legal in NY or NYC).

Good Luck.

[javadog]

If you want a little more power on the top end, you can retard the cam timing. The cams in the 911SC and Carrera are the same, only the timing differs.

You also need to make sure your injection system is working correctly. The CIS was changed a lot during the SC production run. If you are not running the stock exhaust and an O2 sensor, you may have a system that has been changed slightly and you may not be getting the right mixture at WOT.

I suggest you do a search, as both of these topics have been covered in detail.

JR

[Jay Laifman]

I'm voting on something not up to 100% on the car. My 73.5 CIS T used to be great all the way up to redline. I bought it 20 years ago with 40,000 on the clock. The at about 120k miles, I started having various drivability issues, starting with some bad gas and a blown airbox. It took about 5 years and three mechanics to fix it. During that time, it definitely ran out of steam at about 5,000 rpm. But, now that it's back to being right, it keeps on going all the way to redline like it used to.

I'm sorry though that I can't tell you what was ultimately wrong since so many things were replaced to fix it. Each may have made minor changes to get the car running so nicely now. So, it might have been the sum of many parts. But, the final thing that finally got it over the hump was a new fuel distributor and a change from the 73 warm up regulator and throttle position regulator with a newer warm up regulator and no throttle position regulator.

Good luck with your car. YMMV.

[Jay Laifman]

I should add one thing. One of the indicators that my car had when we were trying to figure out why it was running out of steam prematurely was that on the dyno it got too rich at high rpm. Adjusting it down made it too lean in other areas. I believe this part was definitely fixed by the new warm up regulator. That said, I went through FOUR rebuilt warm up regulators before it was right.

[otto in norway]

Last year, I tried a slightly modified 3,2 carrera.
My only comparison is my own 3.0 SC.

I was imediatly suprised by how the 3,2 seemed slow at higher revs. Even though this particular one had engine modifications to give a total of 250 HP.

I have a lightened SC, with a total weight og 1120 Kg. (Sorry for speaking metric, but that equals about 2100 pounds)
That said, my car was stock, except for a performance excaust outlet, short-shift, and sports suspension. (except from exteriour/interiour mods) Stock power was 188 HP.

I am sure that if we took them out on the track, mine would at least keep up with it, -or beat it...!

Anyway: This is my (of course) subjective opinion... But HP is HP, and the 3,2 has more.... -enogh said...!