Idle Adjustment-89 Carrera

[Mike Feinstein]

Since installing new chip, car idles at about 1000-1050. I removed yellow cap and turned the 7mm adjuster nut clockwise to reduce it but it made no difference. I turned it until it stopped and then turned it back about 1/2 turn just for the heck of it.

I don't mind the idle speed and the car runs great...but I had hoped to set it back to 880. I'm just wondering why the adjustment screw has no/little effect. I know there's a procedure for jumping the test port prior to adjustment but I'm not sure which pin sockets to jump...or if that can be the cause.

Any ideas?

[ewave]

The 84-87 spec book says to bridge B and C:

-A B-
* O *
--C--
(EDIT: I need a scanner!)

Who's chip did you install?

Did it do that after it was warmed up?

[Mike Feinstein]

Paul,

Your diagram did the trick. I jumpered B and C and the idle dropped substantially....I'd say to about 650. So, with the jumper in place I turned the adjuster counter clockwise until the idle reached my desired ~900 level. I then removed the jumper and it jumped up to about 1100 rpm's. So, with the jumper removed I turned it down as far as it will go and then back about 1/2 turn (just doesn't seem right to leave it at the end of its travel). Idle remains around 1000-1050.

Using Steve W's latest chip and yes, the engine is at normal operating temp. I know Steve's chip advances the timing, even at idle, just a bit above stock, but it seems I should be able to dial the idle down just a bit with the adjuster. Almost makes me want to leave the jumper in place, but I have a feeling that isn't the proper fix .

[Steve W]

Mike, I just went over your chip binary, and it looks like I had programmed your idle at 1040. My bad. I'm getting a revised chip to you to adjust this back to 880.

[Stuttgart951]

Originally posted by Mike Feinstein
Since installing new chip, car idles at about 1000-1050. I removed yellow cap and turned the 7mm adjuster nut clockwise to reduce it but it made no difference.

Bear with me... still learning the engine bay.. where is the "idle screw" located?

My car idles at about 650 RPM after its initial warmup... Bently says 800-900 is spec.

[Mike Feinstein]

Michael...it should be staring right back at you from behind a yellow plastic cap on the front of the throttle body. Here's a pic coutesy of Steve W (he helped me find it):



Steve...many thanks for the chip swap...and also for being my own personal Porsche guru for the past few weeks through this process!

[89911]

Steve, I'll give you a chance to express your opinion. (Steves currently doing a custom chip for my brothers 87 clubracing car!) What would you suggest/predict would be the benefit of redoing a chip on an 89 3.2 carrera with the following (Huntley Racing MAF and 4 way adjustable air/fuel that replaces the original intake, generic authority chip for 87-89 3.2, bored throttle body and adjustable boosted fuel pressure, SSI's and sport exhaust.) What gains would be recognized with further chip programming, (advancement, octane levels?). The car currently has no drivability problems, just looking for more without opening the engine. I know I can do this one to one but I wanted to show others your insight. Thanks.

[Steve W]

Sorry to get back to you guys so late. I got sick over the weekend over I believe some bad seafood. Anyways, I'm better now, but to answer your question, as you know a properly programmed chip optimizes the fuel and ignition maps for maximum power. The factory programs its chip conservatively to comply with U.S. emissions laws, contend with poor fuel which a owner may encounter, and potential poor engine maintenance by owners. This usually means retarded ignition timing to contend with low octane fuel or air leaks, lower NO emissions, and less fuel than optimal to minimize HC and CO emissions. In the case of the 84-87 Carreras, Porsche was especially conservative with the ignition timing because of the fuel crisis of the early 80s, and practically expected that their cars were going to be run on 87 octane fuel. This means that Porsche tuned our U.S. cars to run on 87 CLC octane unleaded. The CLC octane rating will usually be 4 to 5 points lower than the European standard RON rating and is the rating we see on our American pumps. It is the average of the RON and MON ratings. For example, the European Carrera with a 10.3:1 compression ratio requires 98/88 RON/MON octane fuel, which using our CLC averaging system equates to 93 octane. Our 9.5:1 CR engines requiring fuel quality of 87 CLC octane are rated by Porsche to produce 217 hp/195 ft-lb torque versus the Euro version at 231 hp/209 ft-lb peak torque. This means just optimizing ignition timing to work with 92 CLC octane will make quite a nice improvement in power efficiency.

On the car with a Huntley MAF and generic Autothority chip, and adjustable fuel pressure regulator, there are a multitude of variables that determine how much further gain can be achievable with further chip refinement. Gains could only be quantified by how well dialed in the fuel curves are in the current setup. Generally a 3.2 modified with SSIs require about 5% more fuel throughout to compensate for the increased flow and to realize the true potential of a set of SSIs, and the MAF sensor itself will need about 2.5% more fuel to make up for it's increase in airflow. There is quite a difference in performance between a chip for a stock exhaust, and one tuned for SSIs. Oftentimes, owners may notice little to no difference in performance when changing from a europremuffler setup to SSIs while retaining the original performance chip. My experience with MAF sensors has been limited to working with the Pro-M sensors and the Autothority sensors - which basically are one in the same, as Pro-M makes the sensors for Autothority. As in my car, with a standalone MAF sensor, all fuel and ignition maps are curved in the chip and not with external adjustable air/fuel modules or a modification to the stock fuel pressure regulator. I prefer it this way, as everything is cleaner, simpler, and more reliable. However, the Huntley system I believe is really manufactured by Pro-M also, and if it's similar to or the same as their programmable MAF setup, it's a good setup if dialed in correctly. Assuming that the fuel curves have been correctly dialed in to match the change in fuel pressure, the different fuel mapping of the Autothority chip, and the SSIs, there would be minimal to no further power refinement from tweaking the fuel maps. The only other parameters left to refine are the ignition maps. Your generic Autothority chip has a remapped ignition curve to make up for the ignition factor. While the standard Autothority ignition curves are not bad, I think there is some room for improvement, particularily in the part throttle regions where the majority of us spend most of out time. Comparing the ignition maps between the two of us, one would see quite a bit of difference, especially from 1000 to 4000 rpm, where I've remapped the ignition with a more advanced ignition curve, improving torque, response, and engine efficiency a bit. That's the best answer I can give you, as it is difficult to quantify a comparison such as this but perhaps can be more region specific as I have described. Of course the best way to know is just to try it, and you are welcome to risk free. Best way to proceed would be to remap a copy of your existing chip, retaining the existing fuel curves so as to not alter them, and if it doesn't work out, just return it. If you have further questions, feel free to ask.

[philippeF]

Hi steve
tried to contact you by mail, you should be busy

Do you have something that (would) suits a euro 3.2 87 carrera (octane 98) ?

many thanks

regards

Philippe (France)

[Steve W]

Philippe, have you tried my email address at stevekw@pacbell.net ? Anyways, yes I've have worked with and tuned a chip for the euro 3.2s. Your 87 however, could have a 28 pin or a 24 pin chip, as you'll need to verify. As the ignition timing in your car is already tuned to work with 98 RON octane, I'd leave the ignition maps alone and refine the fuel maps further with an increase of fuel in the high load acceleration and full throttle rpm regions. This should provide a boost in torque and hp without sacrificing your day to day usage around town.

[mm86911]

Originally posted by ewave
The 84-87 spec book says to bridge B and C:

-A B-
* O *
--C--
(EDIT: I need a scanner!)

Who's chip did you install?

Did it do that after it was warmed up?

What is the purpose of jumper the terminals since the chip programming is fixed (non-adaptable)??

[philippeF]

thanks for the quick answer

price ?

(always the same question... )

regards

philippe

[ChrisBennet]

Originally posted by mm86911
What is the purpose of jumper the terminals since the chip programming is fixed (non-adaptable)??

Jumping the terminals disables the idle stabilizer valve while you are adusting the base idle.
-Chris

[Steve W]

Hi Philippe, out of respect for Wayne's board, I sent you a p.m.

[philippeF]

sorry never had the idea to hurt somebody here.......

may you answer me : there's no need to modify firing with the euro 3.2, only injection delay ?

(arrgh i need to improve english)

philippe