dukenukemx

What are some relatively cheap mods that can increase the performance of a 928 with electronic fuel injection? Any ECU upgrade chips that increase HP and MPG? Does deleting EGR seem worth it? I don't see anything that can be done to upgrade the air intake filter that would actually make it better. I know you can upgrade the exhaust headers with long tubes but how much HP can one expect and what's cheap? Also how hard is it to replace the headers on the 32V engines? I'm just wondering what mods are available for these cars?

Speedtoys

First, EGRs dont cost HP, they're in operation outside of cruise on any car..a common misconception.


You could spend $2-3k, and gain I dunno, 35 Hp mostly including the hardware, headers & exhaust, plus chips here: https://liftbars.com/
...not counting a top & front end engine refresh that should be -absolutely- relatively fresh before going down this route.

Maybe more..maybe less, but..nothing significant, and wont solve the real 'problem' that you're likely trying to fix.

EGRs don't cost HP, they're only in operation outside of cruise on any car..a common misconception.

It's really the wrong platform to hop up..without deep investment (Forced induction)...and then still its a GT highway geared design, not a city racer.

By 1985 standards, you own -the- fastest car on the road, and everyone know it. Soak it up..

You can pick up a C5 Corvette for $20k, that would be money best spent to race from traffic lights.

DeWolf

The best performance mod is....ditch the auto and fit a manual box.

The Forgotten On

Any 928 after 1980 in the US market doesn't have EGR, so you can't delete what isn't there.

You could stick in a set of chips from Porken and gain some solid low and midrange power. Other than that it will cost an arm and a leg to get any real power out of it.

Well, if you consider $6k a lot of money for a supercharger kit anyway...

Speedtoys

To go slower?

DeWolf

Well my 86 manual was a hell of lot quicker than the auto's I owned. After 12 928's and three of them manuals, I doubt I'd go auto again.

Speedtoys

I could be wrong..but weren't the 4spd autos faster than the 5spd?

I understand the preference, but torque converters are good for getting goin' from a stop.

gazfish

From a stop you would need to hold the engine at high revs and put the clutch through a lot of stress to match a torque converter up to a certain speed, after that the 5spd has the advantage of a more direct drive. Anyone who has mechanical sympathy for the car (most here I think) would be happier launching an auto on a regular basis.

Speedtoys

Agreed. But...I _believe_ the 4spd autos are still faster cars. The salt flats run was an auto on purpose...

Also..the parts availability demon...

DeWolf

By the speediness criterion, the 1985 Porsche 928S is a substantial improvement over its predecessor. Top speed is up 10 mph, to 154. Our five-speed test car rocket*ed from a standing start to 60 mph in 5.7 seconds and hit 100 mph less than eight seconds later; the old car required 6.2 and 17.8 seconds, respectively. And the new model burned through the standing quar*ter-mile in 14.0 seconds at 102 mph, com*pared with 14.7 seconds at 94 mph for last year's 928. We also tested the automatic version, and its performance is similarly improved. The automatic's 0-to-60 and quarter-mile times now match those of last year's five-speed, and its top speed is up 10 mph, to 152

Landseer

Fine adjustment of throttle cable and Bowden cable pay massive dividends. You have to do this first. Brings revs up before shifts, esp 1/2 and 2/3. And gives you good kick down control. Turns it from Buick to sports car.

Then add the porken chips if you want a bit more.

Alternate tune would be convincing one of a handful of experts here to uber tune with sharktuner tools. But pre 87 is sans knock sensors, a complication.

I alternated between 5 spd euro and 32V auto. Both are fun and a bit different. 5 spd is major PITA to drive in traffic on a commute. Cable adjust is best approach, free performance, big result. Auto can indeed be fun.

DaveK9 had a car with progressive nitrous. Not sure how difficult, as he is a genius, as is Bulvot, who built a turbo 32v 87. Some guys are world class modern hodrodders. At low cost..

Overall, these things are pretty fickle to hot rod. Any meaningful hp bump means money or super brainiac support. Porken chips are that way, but easily sent through mail, ie exported brainiac.

Beyond that, buy some other car, something Summit Racing can overnight bolt on parts.

GregBBRD

"Cheap" "Porsche" "Performance"

These are three words that can never be used together...

Pretty much the definition of an Oxymoron.

hacker-pschorr

The #1 rule of gaining more performance is making sure everything is functioning as the factory intended. There are a list of thinks many 928's have wrong that people fail to check when looking for more performance
1. Throttle linkage. It's a somewhat complex erectors set on these cars. If any of the rods are not set just right, you are not getting full throttle. It's very common as things age for this to be out of adjustment.
2. TPS (Throttle Position Switch) - If this is bad (and they all go bad) the car will run just fine but you won't be getting full performance
3. Has the MAF ever been rebuilt? If not it's probably not fueling properly. Also make sure the screens are still in place.
4. Toss out the K&N filter
5. Cam Timing - if someone didn't do this right it could be off a couple of degrees which isn't good for performance
6. 35 year old catalytic converters are not doing you any favors. Installing an X-Pipe with new high flow cats is about the cheapest / easiest mod
7. Fuel Pressure. You could have a bad regulator affecting the fuel mixture.
8. Plugs / wires, cap / rotor etc...
9. Transmission adjustments. As cables age and stretch this affects the transmission. If the bowden / kickdown cable isn't set right, you are not getting the most out of that transmission. Also the kickdown switch, is that working?
10. I'm sure I'm forgetting something, but you get the idea.

Headers are not crazy expensive and not bad to install. The difficulty is the exhaust after the headers. If you have the ability to fab up a full exhaust yourself then it won't be so bad. Paying a shop to make a complete exhaust can be a few thousand dollars to get a quality job and gains will be minimal over the X-Pipe mentioned above.

After that chips from @PorKen are about the only other "bolt on" mod that will make a difference.

Unless you have some sentimental attachment to this car, you're far better off selling it and buying one with a 5-speed if that is your ultimate goal. The conversion process is far from cheap for the pieces and it's a very involved transformation.

That would be true if the gear ratios were 100% the same, and they are not. 1st gear in a 5-speed is lower than the automatics. Also on top of that the low lazy stall speed of these torque converters makes for a fairly uneventful initial acceleration and low rev performance.

If I didn't have the means to install an 89 2.54 trans with a higher stall torque converter in my 87, I'd either be converting it to a 5-speed or selling it. If the gear ratios in the 85/86 auto are anything like the 87/88, the spacing between 2nd and 3rd is downright awful.

dukenukemx

I own a 2002 Corvette that I just replaced the cam, valve springs, and exhaust headers myself. I just wanted a bit more give when I drive my 928. Maybe better MPG too.

hacker-pschorr

You can always supercharge it

https://rennlist.com/forums/928-foru...s-new-car.html