F451

Hey guys,

With the 7.0 liter thread moving along nicely, I thought I would bring up a topic that I've been wondering about for a long time.

What is the ideal, real world, street legal, not-track car prepped, HP range for the 928?

For arguments sake, lets go with S4 and up with the bigger brakes, suspension bits etc. And brake, suspension, wheel, tire upgrades are ok, but not full blown track prep.

My S4 5 sp has some nice power and is fun to drive, but it sure seems like it could use a lot more get and go.

And personally, I'm not too interested in a tire shredding beast where you can't even touch the loud pedal for fear of losing the back end instantly and ending up in the weeds. For that, I'd go with an American Muscle car (or Australian - right mates?), or a rat rod style hot rod.

I want something easy to drive, but that moves out big time when you want it to.

Many of the modern sport bikes have serious hp available, but are very easy to drive, have nice linear power curves, and are very predicatable. I'm thinking something along the lines of that.

I recall Louie describing his stroker as being very easy to break the tires lose at some pretty high speeds. That sounds like too much "to me".

I'm thinking another 100 hp with corresponding torque increase biased toward the bottom end for street driving would be a nice setup. Something like 400 hp at the wheels I think would be good.

Thoughts from those that have upped the hp substantially??

Feedback would be greatly appreciated.

F451

And let me be the first to say:

It all depends on WHAT YOU WANT!

Ok, I think we all know that.

I guess I should have asked about the road going manners of the higher hp 928's out there.

How do they drive? How do you like them? What type of driving do you do?

Do you need even more HP now?

I'm really not interested in the top HP 928 personally, although I think they are great fun and I enjoy reading about them, admire the skill of those that build them, and would love to drive one one of these days.

Ok, lets have at it.

RyanPerrella

I was thinking about this as well. I need to dyno my car but if my car makes 290-300 rwhp completely stock. I may buy an x-pipe, maybe buy the blackbird airbox deal if they ever become available. Both claim 20hp. lets do what we arent supposed to ever do and add them up and get 340 at the wheels. I think I can assume depending on drivetrain loss that's over 400 at the crank and I can live with that number.

If you want more then you need to SC or turbo the car, or invest in a NA program which could be stroking and head work and so on and spend even more money.

How much do you want to spend, thats the real question?

Jim Nowak

My last car was 525 RWHP and I didn't think that was enough. I think 600 to 650 RWHP would be a good start.

Lizard928

Your question is missing one MAJOR factor.

How much power your car needs is a direct relation to how much your car weights.

my 81 928 weights just south of 3000lbs. It has 310RWHP. This car does move and get out of its own way, but IMO it is not enough, definetly more peppy that a stock S4 5 speed though.

One of the main reasons I am building the twin turbo setup for my car is so that the car remains completely driveable. I only will be in boost when I want to.

And increasing the low end torque alot is what will result in excessive tire spin.
So if you want a car to be able to accellerate faster but not have to overly worry about loosing the back end, imo turbos are the way to go. :P

As to how much power, well I am hoping to obtain 650RWHP and take alot more weight out of the car. I am hoping for 2700-2800 lbs dry weight. If I obtain this, I will have a power to weight ratio of 1RWHP:4.3lbs of car this is at 2800 lbs. That IMO should be enough to keep me in check.

bd0nalds0n

Be prepared for mission creep. It's human nature. You acclimate to the current environment, then begin to take it for granted, then start to think, Gee, maybe ANOTHER improvement would be sort of cool.

I'm pretty content with my twin screw running ~9psi of boost. The car has never really been tuned perfectly, but I still put out >400 HP at the rear wheels. I think there's more torque to be had through tuning, since my torque # is a bit lower than similar setups.

You can definitely light up the rear tires from the get go, but if I mash the gas once rolling, I don't get a lot of wheelspin...as long as you're not a complete dope about rolling on the power (it's not an on-off switch, after all), it's very manageable.

PorKen

I'm sure you meant '86.5, right? Or does that throw off the curve, because they are more powerful than S4s?

I'm chasing 320+ RW, and that's too much for my little 245's. I think it's plenty fast, with just me in the car. But put the A/C on, and/or put a passenger in, and it slows down a bunch.

Like Ryan, I'd like to have the magic 340/400, normally aspirated. Even if it's a just a dyno queen. After that, for regular driving, I'm going to advance the cams for more off-the-line torque, which is what makes a car feel 'fast' to me.

Louie928

That was just a comment. I didn't say that passing a truck on a two lane road with just a little wheelspin in 3rd wasn't fun. Did I mention the sound? Way fun. You don't always have to open the throttle all the way.

I think you are talking yourself into a supercharger.

Rick Carter

How much do you want to spend for diminishing returns? At least it is not as bad as boats where doubling the horsepower only gives you a very little more performance. Of course if you're racing every horsepower and ounce counts. When I first bought my car I wanted 400-500 horsepower and I haven't changed my mind. I want 400 at the rear wheels just to say I have it. I'm happy with what I have now and don't use what I've got very often, but it 's there just like money in the bank.

hacker-pschorr

IMO 450-500 at the wheels for a 928 is perfect. The chassis handles it well, so does the drivetrain and brakes.

The question is, how much is enough? When you can break the tires lose at 150mph in 5th, you are getting close

IcemanG17

Its a slippery slope......I'm sure that when you hit 400whp you will be quite happy....then you'll want 450, then 500, then ????

But seriously......400whp in a street car is A LOT.... with no real traction control on our 928's 400 will have no problem melting tires to the cords....... Anything past that just gets downright silly........

I think a stockish 928 with minor upgrades like brakes (GTS) suspension & slightly larger tires (say 275-295 rears) with somewhere above 350whp will be quite fun to drive....

I've driven and rode in several fast 928's.....ranging from Bills SC at about 350whp....all the way up to Louies Monster at 584whp......honestly you know what my favorite was.......Robs (928SS) street legal stroker....damm that thing was a beast....but 500lbs of torque at a shade over 2000rpm will be a monster..... Dennis K's race shark sure handles well......but so does Tim's Beast (slightly fast too!!)....mine feels like a barge in comparison to either of those!!!

Shane

Agreed! I had one at 400 which was good, but it still left me with wanting more...

500+ would be just about right for my needs.

Shane

And you can multiply that times three, since there is no way I'm going to have one that out does the other two that I own...

Ketchmi

I noticed the other day that I was getting complacent with the 550rwhp 89' I built. I was in second gear on an on-ramp on full boost, trying to keep it straight...with a cup of coffee in my right hand. (closed course of course...with a Starbucks in turn 4!)

Tom. M

You know Ed...I think the first thing you should do is to lighten your car as much as you can (all dependent on comfort level)...get rid of the AC and rear A/C..replace heavy stock seats with lightweight seats. Pull out all the underpadding etc etc...go as far as you feel you want. That alone will improve response. Then go after more stock power..x pipe, sharktuned chips..etc...These are cheap and really make the 928 more responsive. I feel in that form the 928 retains it's factory feel, but makes it snappier... Of course the next step if that's not enough is to go with more....see where this is going?..more more..LOL.. Just sell everything and buy an Aerial Atom...gonna be hard to beat that for power and weight.... Good luck in whatever you decide