What HP can you expect from a unmodded S4?
#16
Based on having seen somewhere easily over a thousand 928 dyno pulls, on a DynoJet, SAE corrected, not counting spikes from misses or lifting abruptly, no funny business manipulating the correction factors, very typical numbers are:
S4 5-speed- 265-270rwhp
S4 Automatic - 250-255rwhp
Some people are probably better off not dynoing their cars. I saw one car that looked great. The owner didn't have much or any experience with other 928s, thought the engine was in great condition and running strong. It wasn't. Slowest S4 I've ever seen. He was happy until he saw the dyno numbers. It did 175rwhp. Sometimes ignorance really is bliss.
S4 5-speed- 265-270rwhp
S4 Automatic - 250-255rwhp
Some people are probably better off not dynoing their cars. I saw one car that looked great. The owner didn't have much or any experience with other 928s, thought the engine was in great condition and running strong. It wasn't. Slowest S4 I've ever seen. He was happy until he saw the dyno numbers. It did 175rwhp. Sometimes ignorance really is bliss.
#18
Rennlist Member
Some people are probably better off not dynoing their cars. I saw one car that looked great. The owner didn't have much or any experience with other 928s, thought the engine was in great condition and running strong. It wasn't. Slowest S4 I've ever seen. He was happy until he saw the dyno numbers. It did 175rwhp. Sometimes ignorance really is bliss.
#19
Under the Lift
Lifetime Rennlist
Member
Lifetime Rennlist
Member
My 89 S4 auto bone stock except RMB (minimal to zero effect) was consistently 262 RWHP on a Dynapac over a couple of years at about 130-150K miles. I've seen as low as 250 and as high as 270 RWHP on decent S4 autos.
#20
Drifting
Thread Starter
#21
Former Vendor
I would think that if you got an "exceptional" engine, with everything at the "high end" of factory specifications, that might be real.
#22
Former Vendor
#23
Former Vendor
#25
Rennlist Member
I pulled 260 rwhp, best of three, 267.5 torque, stock. (With the top end refresh, and new sensors).
77 degrees farenheit, 28% humidity, 28.94 in.hg pressure....10:27 in the morning, engine fully heat soaked.
77 degrees farenheit, 28% humidity, 28.94 in.hg pressure....10:27 in the morning, engine fully heat soaked.
#26
Rennlist Member
#28
Rennlist Member
Rather than clog up someone else's thread I want to know what people think a factory correct S4 has nowdays. Let's say it has 125K and has just had intake refresh, tune up, and everything else reasonable to bring it back up to spec and drivable condition. No mods yet. Do you think under 300 or over 300?
I'm not giving you a hard time (much), and please don't dump a pile of crap all over me again. I'm just saying that your sudden interest in horsepower numbers is kind of amusing.
It doesn't matter what people "think" horsepower is, it is something that can be measured. The factory spec for the S4 (brand-new everything) was 316 bhp, that is SAE horsepower measured at the crank. If you take that number and figure 15% loss with a 5-speed that gives you around 270rwhp, and a Rogerbox with 18% loss would be around 260rwhp, that's rear-wheel hp on a chassis dyno with SAE correction. Which is pretty consistent with what's been reported here and elsewhere. So I think the factory number for the S4 is pretty good, on average. (GT's are different, but that's not what you asked).
That's for a new car. A 25-year-old car will be lower, depending on what sort of condition it is in. "Refreshing" the things that need refreshing is helpful, but doesn't add any horsepower-- it just gets you back towards where the car started. And don't overlook the MAF, it is the key component for fueling.
As for power-adders, don't believe everything that you read. Many folks report big numbers for x-pipes, but remember that they are swapping cats as well as adding the crossover. An x-pipe with new 100-cell cats (or no cats) will certainly outperform a set of melted, clogged factory cats. I do not know of anyone who has done the apples-to-apples comparison and just added the x-pipe without changing cats. I am not saying that x-pipes don't add hp, they do. But doing a proper before/after is not simple.
Will you be at Sharktoberfest? I think there is a dyno in Anaheim.
Last edited by jcorenman; 09-28-2012 at 01:47 AM. Reason: speling
#29