Easy Power Modifications
 

1984 928 Automatic

What are some not super expensive and easy to moderate (difficulty-wise) modifications that I can do to my 928 for some good HP gains?

Y-pipe exhaust

928 automatics are fairly fast cars, but none feel sporty like a 5 spd does, and nothing cheap makes them feel quick off the line.

There is nothing cheap about these cars. I bought the 928 for nice long comfy cruising and a 944T for fun.

Want to go fast:
right foot to right gas peddle!

All I've done to mine is a rear muffler bypass and a very slight (2 degree) timing bump and I can get rubber on the 1-2 and 2-3 shifts if I really have my foot in it.

Power Mods
 

Hi There,

As others have already mentioned, the best thing for ANY 928 is to replace that original exhaust system right away! Y-Pipe, Headers, and Cat Back...the whole 9 yards. That will give you a healthy boost in overall performance, with the least amount of money. Maybe 20-30 HP gain?? That said: It's not real cheap, however, it's the best way to go, and still the least expensive option.

You CAN get a supercharger for all years of 928's....but, at $6000, I opted NOT to do that. :) I don't have $6000 to throw away...

ALSO, jageng.com makes an electronic shifting kit for the automatic trans 928's. You may know that the 928 (from a dead stop) always starts in 2nd gear (for fuel economy), and this little kit enables you to override the kickdown, electronically. It attaches to your shifter button. Only $135 bucks! It's also handy for highway driving, because you can use it to kickdown if you need to pass someone, or, just enjoy some spirited driving.

No, I do not work for those guys, I just thought it was a pretty cool item to mention. :) I'm thinking of getting one, myself....Doesn't look very hard to install, either.

Where are the best quality and most affordable parts for the exhaust modifications? Y-pipes, cat backs and headers...anything else? Should I take it to any muffler shop around the corner to do those changes?? Or take it to a specialist? What to do?

Thanks everyone for your input so far.

I will definitely look into this, have you used it? Is THIS LINK what you were referring to?



What do you mean by rubber?

Definately advance your timing. Euro setting of 27-28 degrees works really well, and costs $0. Summit racing sells a kickass 2 into one Y pipe, and its cheap.
They also sell a myriad of different mufflers, (I'm partial to the magnaflow's), or if you like loud, a simple muffler delete sounds awesome. A true dual with an X pipe is a good setup but will cost more $, (my favorite). Synthetic fluids in your drive train, good for a few ponies, with better shifting to boot. And lets not forget a K&N air filter, not cheap, but very effective.
-Kerry

27-28 that seems like a lot but I am by no means an expert on the matter. I assume that I will need to run 92-93 octane?

And as for exhaust I think it already has a different muffler on it. I really don't want to change the exhaust because the note right now sounds really nice both in sound and volume.

The 2nd gear start didn't come into play till S4 (or was it 86.5) production. your 84 will have a normal 1st gear start.

The 928 wasn't designed as a stoplight racer so no cheap mod is going to launches like a drag car.

My suggestion would be to ensure the car is running optimally for the factory setup first. Also make sure your kick down cable is adjusted correctly, as well as the WOT switch below the pedal (which effects trans kick down).

Then after it is dialed start looking at doing mods. From what I've seems, that the exhaust is a good place to start.

I think he means that he gets slight wheel spin during the 1 to 2 and 2 to 3 shifts.

Ok, so shifter mod will do nothing for me. And what is everyones input on timing adjustment?

Yes, I mean tire spin. My car comes down to 1st gear at a complete stop on it's own. Also if I pull it into 2nd at a stop it will stay in 1st until I rock the shifter to 3rd and quickly back to 2nd, then it will shift to 2nd and stay there till I put it in to 3rd and so on.

Still need input on the timing debate. Also where do I go for performance parts such as sway bars, and stuff in the handling department.


wow check out this mod haha Quite sad what people do to these beautiful vehicles.

Porsche : 928: eBay Motors (item 170512797998 end time Jul-16-10 16:31:48 PDT)

Probably the most popular suppliers are:

928sRus
928 Specialists
928 International
928 Motorsports

I'm sure there are other sources, but these should get you atarted. By the way Roger at 928sRus prefers to do most of his communication by phone or email, his website is rather limited but don't let it fool you, he has a lot to offer.

So mainly, why is everyone saying y-pipe? Isn't the resonator the y-section currently?

No, the catalytic convertor exit is where the flow is combined on the 84 and there is lots of pressure drop.

They are suggesting eliminating the cat and its integral downpipes and replacing it with a Y-pipe.


A better set-up for 1984 starts at the engine.

Replace cast iron collector pipes with A) MSDS headers or B) 1985 or 1986 stock SS collectors which have higher flow than 16V units.

Then, depending on which are used, you probably want to add a pair of sport cats on the inlet to a Y that brings the two streams together.

Then probably a mid resonator like a same-side offset magnaflow.

Then pipe to the discharge point behind the driver's wheel.

(Duals are more expensive than single pipes and gain nothing.)

Here's a set-up similar to what is described. I think its 3 1/4 inch stainless tubing from the MSDS flanges. Sound is incredible but its a little loud for me. And it has the added issue of having no air pump and bullet mufflers instead of cats, so even though its not an emissions testing state, I can pass visual only if the inspection guy isn't looking. That's the struggle right now --- how to get inspected. Previous states where the car lived were more lenient, or else, their inspectors were....its federal law we are messing with when we delete cats.

The inspection guy is supposed to look at the EPA sticker under the hood and trace the emission lines, including air pump, and also check underneath for the connection of air to the cats. New port cats don't use an air pump, so there lies a dilemma. There is no provision for replacement of earlier generation emissions gear with newer generation gear. This is a twin-dizzy euro, so no sticker. Instead, federalization papers that show addition of an air pump and catalytic convertor. Which are no longer on the car.


YouTube - ‪Chris starts Chewy, Porsche 928‬‎

Removing the CAT is not an option. This is a daily driver and needs to pass inspection without any issues.

ctures of some systems. Can't find the one in the clip above.

Left is stock USA 84 exhaust.

Right is an $1100 system.
85 aftermarket replacement pipes and air cat (legal)
Magnaflow same side in/out resonators
Magnaflow dual-in, dual-out short muffler (still needs tip work)http://forums.pelicanparts.com/uploa...1281384464.jpg

I drive an 84 Automatic daily with the system in the right of the picture.

Its very nice. I doubt it provides power increase. (Only juveniles want lots of noise and wheel chirp. My message to them is buy a mustang.)

The 84 Automatic with standard timing is every bit as enjoyable as the 86 32V Automatic. The 86 is a little smoother, but both very powerful vehicles.

Adjust timing and leave everything else alone.

The only reason the 84 has this new system is that the old system was destroyed and I needed to replace everything. At that time, in early 2008, I had no network of folks to trade parts with. So I bought new and had it assembled.

The system on the left belongs to a third 84 car and is shown for comparison.

Try driving a stick in Chicago traffic and see how sporty it i'd

My '84 will start off in 2nd gear every time unless I pull it back into Drive 2, or I nearly floor it in Drive. According to my owners manual that is how it is intended to work, unless I am completely confused....and this would not be the first time for that problem:cool:

There's something wrong with it. Another guy on rennlist is having that problem too and hasn't found his cause.

Check your manual again.

You might have the pressure cable set so loosely that its upshifting very fast.

The change occured in summer 87 according to the 1988 service information documents, so it was in full force for 1988.

My 84 auto car has an 89 transmission transplanted in it. It starts in second unless given moderate throttle, then it starts in first or downshifts quickly to first.

My 84 trans (when it was installed), 85 and 86 all start in first no matter what.

Although, with a loose bowden cable, they rapidly upshifted and were sluggish. Other things can apparently cause this shift problem. Not sure what. Steve Cattaneo advised a guy recently that the B2 piston degradation might be the culprit. Not sure. I have changed one for other reasons, though, and its doable on jackstands.

That is the way mine works and from all the forums I have been at, these cars start off in second unless you put them in second and slow to a stop, or kick it down.. Some even start off in second even when manually pulled into 2 unless you pump the gas.

there are lots of treads on this

Your car is different. Its an 89.

You are not the first to report the transmission behaving like this. People have been confused by the 2nd gear start and erroneously thought that the later-year change was the answer to the problem they were having with the earlier transmissions, 84,5,6 and some 87.


These three pages describe how the 4 speeds should work prior to the change in 88.


http://forums.pelicanparts.com/uploa...1281396748.jpg


http://forums.pelicanparts.com/uploa...1281396762.jpg


http://forums.pelicanparts.com/uploa...1281396780.jpg

Landseer, it is good to know (I think) that my '84 transmission should normally start in 1st without an arguement...it doesn't. I did go back and review the '84 owners manual, that being the one I would swear said it would start in 2nd, and of course it does not....you are correct as normal. Thanks for the correction! But now I have something else to fix......:o

Here's the way later transmission shift, the reference being the porsche tech service information bulletin for the s4 cars which was phased in during the S4 production


http://forums.pelicanparts.com/uploa...1281397184.jpg

The ignition timing quoted was a dynamic setting (3000rpm w/ vac advance).
Static setting would be around 8deg btdc. Sound more resonable?
-Kerry:)

Thank you very much for that clerification Landseer.

I stand corrected

BTW awesome info :D

No problem, I'm sure the situation will be reversed many times.

I've had a little too much time on my hands this year and have been reading the CD set documents like a novel.

Dont mess with Landseer. He has been 'in this game' for a while.

Thanks for the 'chart' man that was pretty good info there. Looks like my car is working well, but not to derail this thread.. Is a symptom of 'hard' shifting a vacuum line leak?

It can be.....I had the problem last week.....and it shifted very hard. Solved the vac leak and it shifts smoothly....in my case the hose had come completly off the line going to the TT and transmission....and I have not solved my starting in second problem.....

Thanks. Figures I missed one . I did the vac lines last weekend. I have to get under the car again anyway. Wish I had a lift. :)

I found my coupling hose disconnected two weeks ago. Fixed it, put a fresh coupler at the tranny, fixed my hard shifting. Shifts very smoothly.

Could I replace Y-pipes and cat-back without doing the headers? A mechanic told me headers need adjusting repeatedly, so I wouldn't want to deal with that trouble. Does magnaflow make a y-pipe and cat-back for the 928S? Which brand is the best for the 84 928S?

Nobody makes anything fun for the 928 that is Calif smog legal. The only options I know of that are legal, as in a muffler shop with a license will install it, are factory and the direct fit replacement in the Calif section of the magnaflow catalog.

My muffler shop made a Y pipe to match the US 85/86 manifolds, and combined that with a generic, but Ca legal at the time magnaflow cat, and made a cat back single chamber (loud) magnaflow muffler.

Its really less of a technical question than what you can find a muffler shop willing to do, as they risk a very large fine for messing with smog stuff improperly.

Interesting...adjusting the headers??? I would like to see an adjustment mechanism? Anyone got a picture or a comment? I have never seen one...

Jon

I believe what the mechanic ment is that header bolts are always coming loose and if you don't continualy check them so that they stay tight, the gasket will blow.
I use two gaskets to get a better squash.
If you use a good quality header with a nice 1/4 or thicker flange then it is not so much a problem.
this page says they have heavy flanges.
Edelbrock.com - Exhaust - Headers - TES (Tubular Exhaust Systems)