bgrabner

This has been bugging me for a little while - My 1987 S4 is my first 928, so I really have no baseline as to how a "normal" 928 should feel. A 300 HP car is not rare these days, so maybe I am jaded, but it just feels like my shark should be faster, especially at the lower end. I know that my torque and HP don't really kick in until about 3K RPM, but I feel downright pokey from a standing start. My Jeep Grand Cherokee, with a 235 HP V8, feels a LOT faster off the line - granted, it has more torque, but its also 1 ton heavier.

I was looking in the owners manual, and it says that an A/T 928 should go 0-60 in around 6.3 seconds. Well, there is no way I can hit that - an informal test has me around 9 seconds, and that is with the kickdown engaged. I know the kickdown switch is working too.

I see stories posted from time to time here about how someone beat x car at a stoplight, when it was coming up behind them, etc...I am not looking to be a drag racer, but I have gotta believe that there is more power to be found. I had a Mustang Cobra challenge me a few weeks ago, and he DUSTED me - now, thats just not right! When I hit 3K RPM the car definitely feels lively, but again, 300 HP seems like a lot of HP - almost too much to handle, and I definitely don't feel like the car is getting out of hand when in that power band.

One other thing - I have found a few deserted stretches of road and gotten my car up to around 110 before I had to back off - I felt like it was hitting close to its limit, not like I had another 60 mph in it.

So my question to you all is, is this normal for a 928? I don't feel like I am missing a bank of cylinders - it's not that slow. I just replaced the plugs and fuel filter with no change in performance. The idle is a little rough, but that is a pretty recent development, and the car has always performed like this. Am I expecting too much from a 17 year old car? Is there any way to test to see if I am getting all the power I deserve?

Any and all opinions welcome!

Bill

hacker-pschorr

On the Mustang Cobra, depending on what year, nothing short of a SCharged or TT 928 would have a chance.

Do what I did, find a dyno, make a few pulls and know for a fact how your car is running.

Big Dave

Doesn't sound normal to me. My '85 still has some jump in her, and I posted 100mph speeds and 14.4 second times at the 1/4 mile last summer....matching the car's specs when brand new.

Start with the obvious stuff. If your idle is irratic, start hunting for vacuum leaks. A whole list of things could be robbing power...dirty fuel injectors, clogged catalytic converter, dirty old air filter, bad plug wires, wrong engine timing, etc. etc.

Jim R.

Definitely not normal. My GT spins the tires in first gear, and accelerates hard. There are many components that could be causing a power loss, and if they have never been replaced, they are due. My 89 had 2 bad knock sensors, which retards the timing by 6 degrees. It ran much better replacing them, as well as many old components and an injector cleaning.

Good luck,
Jim R.

Tony

in stock form they will for all purposes walk away from any 928, Run into one that has some mods, more psi and a tune and they will runaway and humiliate you. Remeber many of these guys have 370ish to 450ish gears vs your 220


There is a guy on the SOCAL board who has put a higher Stall converter in his S4 with marked improvement in performance from what i hear

Again, one of my favorite Cobra Vids. http://www.carvidhost.com/vids/venomous.mpg

Closet Mustang/Cobra fan here

Brent 89-GT

I would try a couple bottles of Chevrons "Techron" injector cleaner as a start. I think I would also seek out a chassis dyno and test the car. Even if you haven't done something like this before it is rather simple. The guys at the shop can easily lead you through the procedure and you will know for sure how the car is producing power after that.

Keep in mind that your 928 has 2.20 rear end gears. It was definately NOT designed as a stoplight drag racer. You are also right to point out that 300hp is no longer very unique, heck my diesel pick-up has more than 300hp. There are a ton of cars out there that are quicker, many fade though as the 928 gets its legs above 100mph. If yours still feels soft at those speeds, something is likely amiss.

geekapalooza

Ditto what Jim said. If you haven't done the Intake Manifold R&R yet, you'll need to do this one. In the case of my (Red also with the same wheels, did you steal my car? ) 87 S4, both knock sensors were bad (limited the timing advance at full throttle), plus the Throttle Switch was bad, and the Idle air bypass hose had a vacuum leak big enough to poke your finger in.

There's always more to check and do (eternally), but the intake job is a minimum baseline for a 17 year old Shark.

HTH

Weissach

Well, it was fast by yesterdays standards. Today, cars are much faster.

bgrabner

Thanks all - it sounds like from your collective experience that I may well have an issue (another on the long list!) to track down. I am going to start with the intake manifold and the catalytic converter - I did a search and it looks like Worf928 did a write up on the Intake Manifold R&R - does anyone have that? If not I will go directly to him. As for the cat I think I will take it off and see if that makes a big difference as well.

Can anyone point a novice to a good resource for checking vaccuum leaks? I read a lot about this on Rennlist, but I have zero experience doing so - I will research, but if you have any suggestions I am all ears.

Tony, I agree about the Cobra - the guy was really cool, and the car was breathtakingly fast. Not a Mustang fan myself, but that car may be able to turn me. BTW, your webpage is such a great, great resource for me - I have used it many times, and will continue to do so. MANY, MANY THANKS!!!

Bill

JKelly

Also, check for extra slack in the throttle cable. I regained a lot of power after tightening mine.

geekapalooza

Bill,

Dave C's article is a great data resource for doing the Intake R&R. http://928oc.org/journal/page2.html

And of course many other great writeups out there.

Jim bailey - 928 International

It is quite possible that the knock sensors are shot , the flappy does not flap , the hall signal generator is defective , the throttle cable does not pull wide open , throttle position switch is defective , the trans may shift too soon . You need an open clear road and a watch .....from a dead start hold the pedal to the floor and at 14 seconds see if you are doing 100 mph . I often have people ask me how to make their S-4 FASTER , my wise a$$ reply is be sure it is running like it is supposed too .

bgrabner

Good point Jim - I don't want to make my 928 a street racer at all - I just think that it is not running how it is supposed to and I am not getting full power - sounds like I have a lot to look for, but on the plus side digging into the engine will allow me to inspect and replace a lot of components that haven't been touched in a while. I imagine you will be seeing yet more orders from you guys - you are lifesavers!

Bill

Chris

Like all the other posts .. time for some maintenance, definately should be enough performance even in this day and age to feel like a powerful car.

Don'g expect a magic fix, probalby cumulative as Jim mentioned.

Chris

heinrich

MY 1987 928s4 5spd with 169,000 miles on the original engine and an Ott X plus chips, makes nearly 300RWHP and 300FT-LBS to the rear wheels, tested.

It accelerates from 0-60 in 5.9sec. I ran two runs only with a GTECH kind of device I had borrowed from a friend and am sure if I tried more than twice I'd likely get better figures.

Her rear tyres will not break loose if I drive her hard, but if I drop the clutch (I never do) or if I ride it, she will break them loose all day.

So .... your experience is entirely nontypical.