Roy928tt

In my humble opinion, if you are not Turbocharging or Supercharging then you are just spending to much money chasing tiny percentages.

Otherwise where in Oz are you?

Cheers Roy

jcorenman

Something is screwy here, Bill. The factory tune for an S4 is silly-rich at WOT (AFR in the 11-ish range). An AFR of 12.5 to 13:1 at the top end is great and will make more power, but I don't know how you are getting there with stock chips.

Here's a typical stock S4 tune, a bit lean in the mid-load, lower-RPM range, and rich (11:1) on top. (This is a Sharplotter view of logged data from a stock S4, the horizontal scale is RPM and the vertical scale is load, increasing downwards. So the lower-right corner is max-load, max-RPM).

I think the reason that the factory set the tune up this way-- at least the high-load part-- is to be "safe" no matter how screwed-up the engine got. This was all done before they had sensors checking on sensors, with everything wired to the "check engine" light. So lots of extra fuel was the simplest way to protect against aging MAF's, broken WOT switches, etc.

Murray

Ok. This may seem like newbie type of question. But if you add xpipe and EIS and make the engine breathe bettter, will this effectively lean it out or will the LH just throw even more fuel at it?
I would love to see a set of s4 chips tuned for x and eis.

Bill Ball

Jim: I haven't seen AFR 11 on WOT in my car. Not even in the 12s. I have the X-pipe and no cats at the moment. Otherwise stock. I'll go out and watch the wideband more closely, but it's a surprise to me to hear the S4 runs so rich on top. The X-pipe was good for 30 HP and 32 TQ in my car without any tuning. I've used Sharktuner very successfully on cars with more mods, like superchargers (mine when I had it, George's, Paul Carver) and seen it used on other modified 928s (Dennis Kao's with hotter cams, others), but I wasn't aware there was much to gain trying to tune stock S4s or even ones with X-pipes, more in line with Roy's impression.

dprantl

That's probably because the increased power from the X-Pipe and no cats is using up that extra fuel in the stock maps. Those 30hp or so require more fuel and it has to be coming from somewhere in WOT open loop.

Dan
'91 928GT S/C 475hp/460lb.ft

killav

I didn't dyno before and after adding the EIS and X-pipe, but while on the dyno after I added the above items, I picked up another 10 RWHP by sharktuning during my three WOT runs. So I have no idea what the net was with the two bolt on's, and sharktuning.


All of the bolt on's you could possibly buy might total up to about $2,800 to $3,000 (excluding cam swaps). A base turbo kit with shipping is around $5,800. The base supercharger kit is probably within a few hundred of that. So, in the end, the user has to decide what is best for them. The latter will add more power, but will cost twice as much up front. Just don't do what I did and buy a bunch of bolt on's then go buy a turbo or supercharger kit!! LOL.

jcorenman

The amount of fuel that is needed depends on airflow, and with more air (i.e. better breathing) the LH needs to add more fuel. The good news is that the LH measures airflow directly, with the MAF (Mass Air Flow sensor). So in theory whatever you do to increase breathing will be measured by the MAF and compensated for by the LH.

The reality is that sensors and systems are never perfect, and no two production parts are ever quite the same. The S4 system does two things to compensate: For USA-spec cars there is a NBO2 sensor which measures AFR and lets the LH adapt its fueling if the engine is consistently running too rich or too lean, for example because of an aging MAF or component variations. (MAF's indicate less airflow-- leading to leaner mixtures-- as they age). For ROW cars without a NBO2 sensor there is a manual adjustment-- the CO-pot-- which sets idle/light-load fueling.

And the EZK incorporates knock detection and automatic ignition retard, to protect the engine against low octane, high compression (carbon build-up), high temps (e.g. heat-soaked intake, starting off from idle), etc. There is some margin there for adding advance, but it will vary from one car to the next, and without a Sharktuner you can't tell how much.

But the basic tuning (fuel and ignition maps) is still one-size-fits-all, optimized by the factory for the mythical average car, and it works pretty well. But you are still leaving some power and efficiency on the table, compared to Sharktuning for that particular car.

Making relatively small changes like an x-pipe or intake will change the airflow some, but are well within what the MAF and LH can compensate for. But whatever was left on the table by the factory tune, will still be left on the table.

So doing simple things like x-pipe and intake will pick up some hp without tuning, and tuning without any mod's will pick up some hp, and doing both will pick up more hp. And the farther you get from the stock configuration, the more hp you can pick up with Sharktuning.

At some point on this slippery slope, spending time on tuning becomes almost mandatory, or at least the path of least resistance. But also understand that tuning a car-- whether Sharktuning or changing jets and fiddling with advance weights in the "old days"-- is more than just turning a dial and adjusting for max hp. It takes time and energy, but in the process you will learn a lot about engines and what makes them go.

PorKen

Could be the MAF getting old, or is out of spec. Very small changes in voltage at high rpm result in a major change in WOT fueling.

Sub-13 AFRs should let you increase the amount of advance. I generally shoot for a 12.5-12.8 average as over 13 is difficult to make consistently stable (enough for high ignition advance). Low or sub-12s AFRs are very consistent, but reduce max power. The more fuel you dump at (very) high rpm, the less air gets in.



WOT AFRs are quite rich, as Jim says, to cover sensor, especially MAF variances, but weather conditions too. WOT AFRs will lean out when it's colder, there is higher air pressure, etc. etc.



Gear ratio is a factor too. Being that the base fueling table is quite small (16x16), and there is no road speed/gear input, fueling is different based on the gear you pick. The rpm/load relationship need only change slightly to make big changes in the injector time calculation. (EG. higher rpm, same MAF voltage.) Autos run leaner than manuals at WOT, with the same LH chip/MAF/exhaust/etc. Not only are the lower gear ratios different, but the torque converter changes the ratio, too.

Ideally, there would have been separate auto and manual tuned chips, but for whatever reason, Porsche supplied only one, and fueled WOT for the worst possible case.

PorKen

BTW, 'lots' of cam retard, 8-12 crank° (or more), will take advantage of airflow improvements (by keeping the intake valve open longer), and may show greater gains with spacers, EIS, etc. (but you have to lower the octane, or increase ignition advance significantly to suit).

Lizard928

You may notice a difference (even though not measureable on a dyno), with the intake side spacers from Roger.
This is because it increases plenum volume which will have a noticeable effect at lower speeds, but not at higher speeds.

jthwan22

I remember one side (forgot which side) of the IM spacer was very hard to install. Most people don;t think you will gain much HP. I have a super charger but don't have hard # if IM spacer gain HP. It does look cool.

antlee928

Hi Roy, I am located in Melbourne and active in the Lansharkoz scene, Tuesday night dinners and Frenzies

Cheers
Tony

antlee928

Guys, some great feedback here and my assessment and intuition suggest I should invest in a Sharktuner to first understand where my current state of tune is at - baseline. I can them make some the map refinements to extra a few more needies and Sir Issacs and then move onto the EIS and (maybe) intake spacers. Although I am tempted to get the EIS. It does look very cool!

BTW, I have a new (std) O2 sensor installed and the intake refresh was undertake by the previous owner at some stage in the last 3-5 years. Fuel usage on long trips (I travel regularly between Melbourne and Canberra - about a 1400km round trip) and fuel economy appears to be consistent and around the expected usage according to other sharkies. By deduction I have assumed the MAF is in reasonably good condition and operation.

To be honest I am not seeking to over HP this car. One thing leads to another and to another and to another. I know from tuning Saabs over many years that when you start to get any car into much higher horsepower and torque figures you start to stress other components which may need to be replaced. Engines are simply large airpumps and I am seeking more efficient breathing without spending huge $$$$ and having complex tunes, etc.

So many thanks to all so far for the very informative commentary.

Cheers

antlee928

Hi Jim, well it kinda looks like its gonna be the Sharktuner firstas first step. If I can stretch the budget a little further I may also try to get the EIS but do the Sharktuning first prior to install of EIS and then review with Sharktuner after EIS install.

Cheers

Bill Ball

Tony:

Keep us posted on your findings when you get the Sharktuner. I guess I'm the odd man out again, as I sure doubted there was much if anything to gain with stock S4s, unlike S3s which respond real well to tweaking.