engine power seems lacking at midrange
 

forgive my random writing... as I tend to think as I type.

First off... did a search on here for a similar issue and found some posts that seem to point to replacing the coil (unfortunately I'm not sure what this 'coil' is?)

I'm not familiar with what part is what... or what to even try replacing. As far as I know, everything is still original on my engine.

The issue is that at about 3000-5500 rpms, the car tends to lack power in the midrange.
When it hits over 5000rpm... it picks back up and starts gaining power again.

car always starts up great...idle is perfect... engine sounds fine (no coughing and no odd sounds).

The car doesn't actually lose power, nothing drops or anything that would be a concern. It's just that the car seems to pull slower through the midrange with WOT.

So... given I am new to my car and not familiar with what a car like this feels like when it is in perfect condition...
Is there a recommended gear, speed to test hard pulls in this car to see how it performs?
Is there a timed pull I can try? (ex. how fast should it accelerate from 40-60mph in 2nd gear? or 3rd gear?)

To me, and my experience, it seems as if the engine isn't 'opening' all the way when on WOT.

Any suggestions on what to replace first? New spark plugs? new plug wires? etc...

Try another air flow meter. I've tried several on my 87 and I can tell you none of them are created equal performance wise. If you happen to get a good one, you'll be smiling from ear to ear.


Cheers,

Joe
87 Carrera (and smiling from ear to ear)

i would normally say lack of power is fuel related, when you can hear the engine "gasp" as you rev it, but i think in your case it could very well be ignition as is your hunch, possiable air leak too.

I say don't replace anything willy nilly - diagnose it. You can check your spark plugs wires, coil, and rotor with a multimeter for resistance, start with that. You should also be able to check the air flow meter, buy a multimeter and get a porsche workshop manual, and systematically check. Normally the fault finding sequeance for any engine is

Step 1 - Verify/Check compression/leak down test
Step 2 - Check Igntion System
Step 3 - Check fuel system (i.e carbs, injection)

I always follow these steps, it works, and you will learn about your engine and verify its state of health as you do so.

The wrong muffler "upgrade" will do exactly what you're describing. You said you're new to the car and the engine is stock but is the exhaust?

A 3.2 is at its glorious best pulling hard from 3 to 5k

Even more glorious when it pulls from idle like a 996.


Cheers,

Joe

[QUOTE=McLaren-TAG;9470771]The wrong muffler "upgrade" will do exactly what you're describing. You said you're new to the car and the engine is stock but is the exhaust?

A 3.2 is at it's glorious best pulling hard from 3 to 5k[/QUOTE

That's exactly what I've understood the 3.2 to be strongest at... that's why I am guessing something isn't quite right. Maybe poor performing injectors?

yes... it's a stock exhaust... and original I'm sure based on the rustiness of it.

I plan on replacing the exhaust with a fabspeed catless 2 out design.

I was also thinking of going with some better performing spark plugs and magnacore plug wires and whatever other go fast parts I can put on it (including a chip)

My biggest problem (and I'm sure many of you can relate)... is that I want to do EVERYTHING NOW!!! But I need to go at this one step at a time.. fixing one thing before moving onto the next thing.

I guess, maybe the PO should sell his 87 3.2 and buy two or three 996s with the money. ;)

He could or another alternative, incorporate some of the tricks the 996 uses, like EV6 injectors and optimized fuel delivery and ignition. A much better option than dealing with IMS issues, you think?


Cheers,

Joe

Get a Steve Wong chip.

The problem with replacing the chip is that it only masks the underlying issue and does not deal with the problem. I have a stock chip in my 87 and have four air flow meters that behave very differently. The one I'm currently using that I have modified makes my Carrera pull like a freight train right off the line with loads of throttle response at all rpms. I also have an air flow meter that makes it fall flat on it's face that no amount of chipping will ever fix.

I feel that chipping is like a band aid and never deals with the real issue.


Cheers,

Joe

chipping is bad if it is used to mask problems but a properly running car can benefit greatly by chipping. Scarceller on this site is offering a chip and injector deal that i feel is an immense improvement on our cars. four hole modern injectors with a dme overhaul and a fresh modern mapped chip. i am doing this in about a month when I can actually drive where i am. he also sells a mass air flow system that is cool but i want to retain the stock look of the air flow meter. I carefully took my air flow meter apart and reindexed the wiper arm on the wear strip and it removed the midrange stumble completely. just my opinion, take what you will. Dan.

I've been using the much improved four hole Bosch EV6 injectors but find the five hole GM low impedance Multec injectors are even better performing and smoother. I also found that increasing the spring tension while reindexing the wiper made a huge difference on the AFM. Joe

stlrj. are the multec injectors ev6 connections also. if so then they require the ev1 adapter? would you have the part number of the multec injedtor please so I can compare at the Weiss injector site. thank you. Dan.

No adapters needed on any of these multecs. Right now I'm running high impedance multec six hole (Saturn) injectors, PN 17109448, with great results since they atomize the fuel even better (unable to find flow rates on Weiss site). For best results it's recommended that plug gaps be increased to 0.060" to avoid an intermittent miss.

Cheers,

Joe

Thank you very much Joe. Are you not worried about a lean or overly rich condition? Do you have an afr guage installed? I am very conscious of the cost to rebuild but people seem to try new injectors on the fly. Can the wrong injector be catastrophic? I do not know but I do know I want the benefit of modern injector drivability. Thank you again. Dan.

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Get it on a dyno to obtain a baseline power/torque/AFR reading

problem is.... where I live the nearest dyno is six hours away. i will buy an afr guage I guess. thank you.

I've been experimenting with different injectors on my Carrera for decades and have screwed up more times than I care to admit, so if you are not comfortable (or afraid of screwing up and screwing up is a garantee) or have never done anything like this before, I would do more homework and leave well enough alone. Keep in mind, even something as simple as removing the injectors on a Carrera can be beyond the capabilities of most on this board. Also, I might add, this procedure assumes you have the ability to make the necessary air flow meter adjustments to make these injectors work properly to your satisfaction.

Another I might add is that if you need dyno to tell you how much power you're making and unable to trust your instincts, I would not attempt this.


Cheers,

Joe

I have rebuilt a few motors in my time and have restored a few cars and trucks. I can do the fuel injector swap confidently. I would like the parameters of the injectors to be as close as possible. I also know that the DME will drive high impedance injectors with little difficulty. I am after finer atomization and smooth running. Maybe a few mile per gallon improvement. The air fuel guage will be adequate. A dyno to me is for competition engines and rebuilders. If I was smart and not stubborn I would just pull the trigger on sals upgrade injector deal. Remap dme , upgrade to 28 pin and injectors. He has done the work already. The exchange rate and the fact I want to play too! My car is at 97000 miles so the oil pump shafts bearings will need doing as well as top end. I know...... there will be more. But that's where the fun is. I really appreciate your words of caution. But I am beyond recovering from this addiction I am afraid. Cheers.

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From the description the problem is certainly not coil related-they only get worse with RPM
though higher range misses can be hard to detect.
And Can't be lack of fuel or that too would get worse higher up in the rev range.
I'll second trying a different AFM first.
Newer style injectors are nice but do cost $ and again I really cant see them being the root of the problem either.
And I will second using Sals stuff over SW any day. Though in the end the only real improvement
is adjusting maps to optimize fuel and timing curves for the current gas as opposed to what the DME was diligently mapped for in 1987.

That's just what I wanted to hear, now let the fun begin!

"I would like the parameters of the injectors to be as close as possible."

That's what I was looking for too initially but found that these new style highly efficient atomizing injectors do not need to flow the same as the old pintle style Bosch injectors and yet produce more power and torque more efficiently. To my surprise I found that lower flowing EV6 or Multec injectors performed much better than injectors of the same flow rate as the stock Carrera injectors.


Another hopelessly addicted soul,
Joe

I noticed that the 17109448 injector is rated for 180 cc per minute while the stock single Pintle injector flows 229.1 cc's as per Weiss. Injector rehab site says 296 cc's per minute for the 0280150158 stock porsche injectors. So conflicting data. I am inclined to go with Weiss. What you say makes sense because of atomizing efficiency. More bang. And resulting efficiencies across the board. More cooling affect. Improved mileage and drive response. You have done the wheelbarrow work for me. Now have a beer. A Westmalle trappist on me.

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I also noticed that Porsche downsized the four hole EV1 Bosch injectors on the 996 when compared to our 3.2 Carrera injectors. It seems since the 996 displacement is larger and putting out almost 100hp over our Carreras that the flow rates would be much higher. Yet the 996 injectors flow at 220 cc's while our 3.2 Carreras flow at 229 cc's. Considering the differences in displacement and hp you would think the 996 would have injectors flowing closer to 250 cc's. Hmmm.

Good point. An interesting Avenue for thought. It's seem with that analysis between our Carreras and the 993. We have some power left on the table. I would assume fuel pressure is adequate to provide volume but the efficiency of our volume is suspect. Your pick of the 9448's seems to be an a hint of proof in this by your reports of improved performance. They are reasonably priced on ebay too. Onwards...

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Getting the car to run well stock should be done before playing with chips and injectors.
When was the last time it had a tune up? Plugs, wires, distributor cap and rotor. How does the inside of the distributor look? Do the weights move freely. The 3.2 timing is controlled by the DME, but the distributor centrifugal weights keep the rotor in phase with the contacts. The felt should be lightly oiled on occasion.
You can also make sure the idle switch and full throttle switch are set right and working.
Are there any air leaks? Make sure the intake runner allen bolts are snug, and check to see if any vacuum lines are loose or cracked, along with the lines to the cruise control. I had a leak at the fitting circled in this photo.
http://forums.pelicanparts.com/uploa...1489245427.jpg

Another area to check is the AFM wipers. Some high mileage cars have the contact strip worn out, and re-positioning the contacts can make a big difference. The links in this thread seem to be dead now, but it should give you help in checking it out.
http://forums.pelicanparts.com/porsche-911-technical-forum/288603-fr-wilkes-afm-mod-success-easy.html

Good info... I'm planning on replacing all plugs and wires with a slightly better performance options. From what I've been told, vacuum leaks would affect idling, and my car idles absolutely perfectly?? I'll have to check the distributor.... it seems difficult to open up and didn't want to mess with it yet.
Nonetheless, I already have a set of new headers and exhaust on order as well as a new chip replacement to support the exhaust mods... but I know that this will only mask the problem and want to find the issue in case this leads to something more serious.
On a side note... could this be a symptom of a cylinder leak? I haven't had one, but I guess it wouldn't hurt to check the compression.

I obviously need to update my reference material since I was unable to find this flow rate on the Weiss site. Which site has this information?

Cheers,

Joe

Witchhunter. Com/flowdatapix/rp17109448.jpg states flow at 178 cc's .

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Www.injectorrx.com/rochester-fuel-injectors/ I just realized you are an engineer. I will now talk less and listen more. I hope this helps.

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Wow, I must be getting old. I have that site but didn't see it 'til you told me.


Joe

Correction: Stationary Engineer