Fsharp9

Kept mine in without the belt on it after the bearings went last year , and just removed the pump assembly last week when I installed the Porken tensioner, my cat is hollow anyway so I don't think it will be missed

Alan

if you leave the air injection ports uncapped you wil have an exhaust leak(s) - not an option.

This isn't really something you just do for grins.. its a lot of work and it doesn't cost much HP. If you just care about the HP or the pump is just too noisy just cut the belt for it (until you decide what to do long term).

Usually this is removed to address the redundancy if you go to new cats that don't need supplementary air injection, to reduce weight for a track car or to make space for something else (scavenge pump, vacuum pump...).

Alan

928newb

OK, I should have clarified that I have installed the xpipe and used a 21" belt for the fan. The pump is still in because in order to remove it completely, I would have to remove the timing belt tensioner.
I have disconnected the vacuum line to the diverter valve and plugged it, but I have not done anything to the air pump hoses. The blue one is still connected to the valve and the one that went to the cats is not plugged.

Jetdriver69

I deleted the air pump, cat, diverter and both stock fans. This job is much easier when the engine is pulled for a rebuild. Replaced fans with an electric set up from FFDynamics. Makes for a very clean and uncluttered front of the engine. I don't know if I noticed any more HP without the pump and cat but the engine runs much cooler with the electric fan and the exhaust is very throaty. I like very much!

GlenL

Got the parts to remove it from my 2nd '80 Euro S. This has it piped into the heads. Got the shorty belt already on it. Now removing weight and clutter. I'll probably rebuild the engine before too long and nice to have it gone previously.

The Fixer

I only have 1 belt up front.

The much improved throttle response was worth the effort.

GM Engineers recently found that adding a wider alternator belt by 1 rib to run a higher output alternator,
sapped 5 HP from there new NASCAR motor.
It definitely adds up turning all these accessories off the crank.

Living in Arizona you need your A.C. though.

Avar928

Upgrade to a Porkentensioner on your next TB/WP job and get the "without Air Pump" version which knocks out the support bracket for the air pump. If you have a PKTensioner with the Air Pump bracket, you can still delete the air pump and you'll just have a threaded support bracket.

demetan

Hey Jetdriver69, do you still own your 928? just wanted to have more details about your electric fan swap. I have an 89 S4, so I don't know if the mod would be the same & I'm also planing on changing the original belt tensionner for a porken & I was wondering if it's worth the labor time to delete the air/smog pump. THNKS

FredR

No idea whether Mr Jetdriver is still around or not. The stock fan setup is pretty robust and Roger does replacement motors for them. They are however built like brick outhouses and there are more elegant installations out there for those so inclined. When I purchased my current 928 some 16 years ago it had two very noisy fan motors and a shroud that was cracked. I decided to replace it with a Spal dual 12 inch fan unit that Ipurchased from the following outfit:

https://the-fan-man.com/product/12-s...ric-fan-s2130/

The SPAL fans are very compact and very quiet and whereas I doubt they will last as long as the stock items in terms of run hours it is relatively easy to replace the bearings in them. Fitting the shroud takes a bit of effort and in my case, as the stock shroud was done for I pirated mine to use the inlet shroud and on first glance thus looks very much like a stock setup but with bags of room between the fans and the engine. This unit moves a bit more air than the stock setup and the way I have mine configured it is "gone in 30 seconds". I paid something like US$275 for my setup from the outfit listed above- today they are listed by them at $350 which is still way cheaper than other outfits seem to list them for.

If your air pump is working I see no reason to delete it as the PKT has an option to retain the air pump. I guess it all depends on your position regarding social responsibility. The 928 fleet over here was supplied without CATS as leaded gasoline was only phased out in 1994, the year I joined the local refinery as Chief Engineer. The air pump on my 90S4 was abandoned just before I lost the car after the bearing failed. The local agents reckoned it did little other than satisfy US regulations that were not applicable over here so we abandoned the setup. I rather felt omitting the thing left the motor somewhat smelly at idle but whether it makes any difference during cruising I do not really know. The local team advised me that it was designed to pass certain legislative tests carried whilst the car was stationary for whatever that may be worth- doubtless others from your side of the pond will know better about the consequences of deletion. I took the point of view that it takes a little power to drive the thing but nothing one would would ever notice unless your name happens to be Lewis Hamilton who seemingly can detect a frog farting in the wrong direction whilst doing 200 mph [the car that is- not the frog- unless it was Romain Grosjean }!

Speedtoys

If you remove the pump, install an idler.

Porsche put that opposite the alternator for a reason.

demetan

Thk'iou FredR, very interesting reply. For the moment, I'll keep the pump installed, since there's no real reason to delete it. As for the fans, one is not working, but I suspect an electrical bug & yes, my fan shroud is cracked at many places & the previous owner did minour patching. It is in my intend to purchase a new one in a future project but then again, I noticed that 928Motorsports has 2 models: one for a air/pump still on & the other for a a/p delete, if I decide to change the cats for free-flow ones & add an x-pipe while I'm at it. At first, when I acquired the S4, one of the thing I had in mind was to install a new exhaust syst'm, with headers, but it seems a PITA for the $ spent.
I also bought, a few yeas ago, a Sharktuning kit & 25 lbs injectors, but I only have changed the chip yet & I will need to ask Jim again for all the wiring connections when I decide to go throuht with the job. Do you manage to have good gains with yours? What's your set-up on your S4 (if you don't mind sharing of course
demetan

FredR

My engine was noted by the local dealers chief mechanic as being quite strong but it took a fair bit of sorting out of the usual culprits before I got it to run correctly. In its current situation I mated the GTS inlet cam with the S4 exhaust cam and also made a custom exhaust wherein the front section has a Louie X pipe, the intermediate resonator was replaced by a large Bullett muffler and for a long time I had the RMB on the rear- this gave a rorty but not over bearing exhaust tone. The local procedure is such that cars over 10 years old have to be inspected by the Oman police annually to get registration. A friend tipped me off that they were getting more stringent on noisy exhausts so last year I put the original rear muffler back on and whereas I planned to remove it post inspection to my surprise I preferred the quieter drone. The RMB makes no difference that I can tell of power delivery wise. The inlet has a oiled filter element each side of the engine that came as a set from Roger. I found it seemed to help the engine breath a little easier. The sharktuning was interesting and I am probably still a bit soft on advance. I fitted new design two 4 hole 30lb injectors and I wanted to know whether I could learn to use ST2 which I did to some extent. At the time I only had access to 95 RON. Today I can get Super 98 and really need to get ST2 out and advance the timing some- probably a couple of degrees across the board. With stock wheels/tyres the motor used to pull a healthy top end. The handling side of the car is substantially modified and with 265 rubber up front the cornering is awesome but I reckon the wider rubber has more rolling resistance and thus there will be a top end penalty. Since I lost my 90S4 some 16 years ago I have little inclination to go ballistic given what I went through crashing hard at 70 mph due to some tw*t on a mobile phone. The ST2 gains come from the ignition advance rather than the fuelling. I do not access to a dyno so can only guess the difference they make but I reckon they must be worth 20 to 30 bhp in total. I understand the latest x-pipes have a noticeable improvement over the earlier versions like mine.

If you do change over the injectors it is helpful if you know the opening time for them and set that when updating as well as the poundage. Even so it is not too critical when using ST2 and one is tuning to the measured AFR. I understand it is possible to determine the injector opening time with ST2 - Jim is the authority on that one.

Darren nicolson

mmm ok...well they cant put it all on one side???? im reading comments on ''CRANK SIDE LOADING'' a crock ''IMO'' we are talking a production v8 engine.with 400hp..NOT A 10.000HP.top fuel dragster..the crank will naturally have ''LOAD'' on the left...YES??? the ''belts'' for ''AC'' and ''AIRPUMP'' dont do miricals and tighten.to counteract crank loads..DO THEY..???

Alan

I believe the air pump (even if fully functional) only aids catalytic function when the cats are cold (e.g. idling & low rpms after starting before the engine & cats warm up). After 15-20 years I suspect most un-rebuilt air pumps (e.g. ~all of them) probably actually pump close to nothing. So unless they are noisy or binding - as they wear they should load the engine less so they'd act more like an idler anyway. Good reasons to remove would be to use the space for something else* - otherwise indeed no strong reason to make any change.

*vacuum pump or oil scavenger pump are examples of what people have done there - these would still have a crank belt there with ~similar loading. The space could be used for other non driven uses (e.g. maybe a Provent-400 or similar). I'd also not worry much about crank loading in that case if it were me.

Alan

Darren nicolson

cut my belt.seems quieter and ''LESS SMELL''& more response...''IMO'' 88S4.ALSO CUT THE METAL PIPES..OFF TO THE ENGINE BAY...undo at the exhaust....then ground down a ''bolt head'' that fits in the 17mm nut..put gasket cement both sides screw back on...''NO LEAKS''.