Having some problems with my xr8 running like crap, missing etc and blowing heaps of black smoke out the exhaust. It happens every couple of month or so. I use octane booster sometimes when I travel as there are no 98 octane fuels away from where I live and my car is tuned for 98 octane. I think that the booster is clogging up my injectors. I usually just chuck some injector cleaner in the tank and the problem goes away for a while. It just happens to seem like it is happening more frequently latlely so I am thinking of rather then getting the injectors cleaned I might just buy some new ones.

If I was to buy some new ones would I be better off just going and getting 24 pod injectors rather then the standard 19 pound or whatever they are. Would this get anymore power out of a standard engine? I am guessing I would need a tune to run them as well as possibly a bigger MAF and throttle body to actually get them working properly.

Basically is it worth getting 24s from BPT or somewhere? Is it a worthy upgrade? Or should I just get the standard ones cleaned? The car has only done just over 90,000 kms, I have had it since 57000 kms and I am pretty sure it hasn't been done in that time.

What sort of mods on your car? Any idea what power it is making?

If its power is pretty close to stock, then there is no value stepping up to bigger injectors.

As MAF are matched to injectors.....its not just one thing.
I have run low 14's on 19lb injectors.....

Its basically stock. I am just thinking that if I were to spend the cash on new injectors would it be a better idea to get bigger then stock injectors rather then to have to go out and buy them later on if I was to look into doing any performance mods to the engine.

It wouldn't hurt, but you would need to get a chip like the CAPA Eliminator chip (or Ciptorque J3) to reprogram your computer for the bigger injectors.

Factory MAF's are NOT calibrated for any particular injector size.

I wouldn't be so sure that the problem is your injectors. Could be fuel pressure reg? Or your MAF?

im running a EL XR8 II engine with about 115,000km's on it injectors are fine, if anything get em cleaned, if that doesn't work, me personally i'd go some bigger injectors, IMO might as well if you get new injectors.
and yes your right you can't just put them in.

i did have a problem with black smoke coming out the exhuast at times to, it all had to do with the maf, the sensor wasn't screwed on propley and there was a little hole where air was getting sucks in from the maf sensor coz it wasn't on very tight, but even if it's not that, might be a worth while thing to clean your maf/sensor out rather then spending money on injectors/cleaning injectors.
i forgot the name of the process....it's mainly for GAS cars coz thier engine gets cloged up faster then petrol cars do, but you rev it and that a tone of junk comes out of your engine and though your exhuast, that might help too, if anyone can remember the name of it post it up.

Bwahahahaaaaa.....WTF are you on about?

I think he's referrring to the EL GT and FBT MAF's?

MAF and injectors are matched, as a set, and technically you can trick the ECU with electronic wizardry to believe that the injectors are bigger or smaller. The MAF is a meter, it reads how much air is coming in, therefore telling the engine how much fuel it needs.....
You will most likely find your O2 sensors are shagged, and a new set of plugs wont go astray.
Check your TPS voltage too, could be out. .98 for manual, .93 for auto.

Thanks guys I will have to check it out. I think I will start with new plugs and leads and then probably get the injectors cleaned. How do I check the TPS voltages? Where do you put the multimetre probes?

The MAF sends a voltage signal to the EEC, and the EEC uses a lookup table to convert that signal to an air mass/time value....nothing more, nothing less.

The EEC is what calculates injector pulsewidth, based off that air mass value, and a bunch of other constants in that EEC strategy (including injector size, engine rpm, and fuel trims).

The signal from the MAF can be "calibrated" to trick the EEC into calculating pulsewidth for a different injector size....but what other parts of the EEC will this "calibrated" signal affect? Ignition timing, and basically anything else that references engine load or volumetric efficiency.

To be technically correct, aftermarket MAF's are not really "calibrated" for a particular injector size either. They are "calibrated" for an injector that is a particular ratio larger/smaller than the original injector size for the EEC calibration/processor code they where designed for.

347Stroker, if you dont understand any of this stuff then you should not be giving anyone advice on selecting a MAF.

Now that's funny!