What Hilton said ^^^

If you don't have access to a Sharktuner, then stick with 19# injectors-- that's what the ECU's are calibrated to.

S4's are nicely balanced-- the intake, cams, and exhaust are all restrictive, and they play well together. And 19# injectors provide more than enough fuel. For the GT's they fixed the cam's, but the 19's are still OK with stock intake and exhaust. If you fix the exhaust then you an start to think about more fuel (i.e. 24# injectors) but you need a Sharktuner to make effective use of it. Otherwise you are stumbling in the dark.

It's a bit of a slippery slope, but a fun one!

 

So would a GTS benefit more (if any) with the 24# injectors?
.4 more of a liter and an X-pipe?

 

Hi Landseer,
Yes, I got the rebuilt ones. I got the seals from Roger. Now that I have done it once, I will be able to do it in half the time next time. It takes a little while for me to learn the tricks to doing it right.

That being said, something strange happened, the car runs perfectlly smoothe, but has no power. I am going to re-trace my steps today to see if I left a vacuum hose off somewhere. The transmission is also shifting very hard and I don't like it. I looked for 20 minutes for that line but with everything back on the car, you just can't see down there in the back of the engine. So, since my issue was not the fuel injectors, I am considering putting the orig ones back in...

 

IIRC, 19# injectors are good for up to 350ehp. If you have X-pipe, you
could be close to limits of your current injectors.

http://www.witchhunter.com/injectorcalc1.php4

With 4-hole 24# injectors, you also get better fuel atomization, which will give
smooth idle and slightly better mileage. Many advantages to go for 24# if
having GTS.

Simo

 

One of your vacuum splitters have been knocked off and your tranny isn't getting any vacuum. It might also be tied into your FPR so that would explain your lack of power.

 

A stock GTS is fine with the 19# the cams are very restrictive. A GTS with GT cams and an X pipe/headers would need 24# and a SharkTune.

A very nice combination

 

Thanks for the tip, going to buy 8 19# for my 89s s4(NA).
By the way, what else do I need except injectors?

 

I put new 19# Fords in my car last year (from Roger) and they work great.

Notwithstanding the above and everyone else's comments about cleaned injectors ... if anyone wants my old (probably original) units, send a PM with an offer ... glad to find them a new home ...

 

The 24's run perfectly fine with a stock LH/EZK....in normal day to day driving. You won't notice any difference (unless you have the fuel economy gauge in the 89 and up). When you go to WOT..then it will add more fuel than necessary (since the map in the LH is set for 19 lb inj.). Even then it's minor. I've been running the 24's in my GT (with x pipe) for years..and no real decrease in fuel economy..and I'm not billowing out black smoke either.

If you are going with a X pipe etc....and plan on a sharktune down the road..go for the 24's (if they are the same price)..

 

If you buy them from Roger Tyson then they come complete with the correct seals.

After changing the injectors and before you try to start the engine, jump the fuel pump relay and check you have no fuel leaks in the engine bay.

Also a good time to replace flexible fuel lines if you haven't done so already.

 

Hi John
Thanks , I did not get the parts from Roger Tyson, so I think I need to buy these injector seals. Can I buy that for Roger?
I live in Taiwan, I just got my 89 s4 for two months, it is a very very nice car.
By the way, can you tell me the flexible fuel lines parts number?
Thanks again.

 

there is no flexible fuel line part number, Porsche discontinued them, except the front one that connects the two fuel rails. You need to also get the fuel lines from Roger, he sells a rebuilt kit. If you search you should find a write up about changing fuel lines on a S4.

 

If you bought the Ford injectors they have the wrong bottom seal for the 928. Roger can supply. Roger also sells a kit of parts so you can refresh the flexible fuel hoses yourself. There are threads on here that show people doing this (you carefully cut the old hoses from the fittings and use new hose with the old fittings )

 

Thanks you guys help, I gauss I am the only one people in Taiwan, Taipei city driving 928.
It is so nice to meet you guys, thanks.