what bigger injectors fit a mrk 1 plenum around the 280-330cc

i'll be on same quest soon, heres some info seen:

thanks to(benjy_2,steve NZ,Low131,cerveza)

Even 220cc will only fuel enough for 176HP and that is at 100% duty cycle.

That is based on the general rule of thumb 500cc/100HP.

I think you more want more around 250cc to get your 200hp safely.


look for these bosch injectors, the same style as your original:

hose tail inlet, long jap (nissan) style pintle cap.

0 280 150 135 (o.e Nissan Aussie assembled) 224 cc @ 3bar
0 280 150 152 (o.e Alfa 75 1.8T, Bmw early 6cyl) 279 cc @ 3 bar
0 280 150 163 (o.e Nissan/holden Australia) 222 cc @ 3 bar
0 280 150 205 (o.e JD camira) 232 cc @ 3 bar
0 280 150 214 (o.e fiat argenta) 222 cc @ 3 bar


and using a B.S.F.C formula for forced induction and a max duty cycle of 85% you'd need 330cc conservatively. And obviously once your talking about using an injector that much larger than the original, trying to get it to run smoothly at idle will be very difficult with the stock ECU and AFM. Steve would know about this the best though.

I personally still believe running the standard injecotrs and a 5th injector and controller (for when on boost) will be easier to settup if you want to keep the std ECU and AFM. Eliminates low rpm/idle rich running.


After extensive reading I have managed to locate a product for safely connecting hoses to bosch o-ring injectors so that is problem number 1 solved.

I intend to buy the bosch 0 280 150 712 injectors (Saab 9000T) 240cc/min and adapt the manifold to accept these.

As a temporary measure I will get it running with AFM and fuel pressure tweeking but I am seriously considering going for the megasquirt fuel only system. I am a little concerned that I do not have the knowledge to safely tune this myself though so this will rely on locating a local tuner who is familar with this ecu.

Does anybody know if it is possible to change the pintle caps on the Saab injectors to ones the same as the stock injectors with no o-rings? Will they still function the same if I do this? I could then just fit them straight in...

yeah thats easy, just cut off the old pintle cap, remove the spacer and o'ring, then fit a new jap/nissan style pintle cap, which normally use a square profile crush seal over the top.

you cant find any of the injectors I listed above, they would save any mods to how you fit the injectors.


I dont like the idea of using the 712's even with a piggy back. Thats me though, if you want to try, thats up to you. Im sure you will get it runnng and it will probably give enough fuel on boost. Thats the easy part though. Getting it to run right off full throttle is the hard part.

How well you want it to run is a question that needs to be asked. Run "good" is easy, run a good mixture is very hard. Engines will always run nice when rich. A lot of people fit larger injectors, let it run rich and are perfectly happy with that. Its of course not good for the engine though.

My 712's were tested at somewhere around 280cc. Other sets maybe lower, who knows. I dont see these getting a good mixture with a mk1 ecu, piggy back or not. The 240cc injectors were still too rich at idle, even if i held the AFM shut, let alone more. A piggy back wont fix that.

Good luck with the 712 pintle caps. I could not get them off, not that I tried very hard though. I decided not to use them becuase of the caps for a start and they were going to be too big. They were straight plug in option for my mk2 too.

Rated specifications of used injectors can be far from accurate too. Your 240cc injectors may have a true flow of 200 or 280. You wont know unless you get them tested. If they have not been cleaned for a while, you'll find they flow quite a bit less.

The injectors listed are not common here either, but you should find something. Point is there are many options. Getting exactly the correct injector for this type of mod is very important. It has the largest effect by a mile. If you want to get it at all close, it will require maybe a few different injectors to be tried and a few trips to the dyno. Whatever you do first is probably just a starting point. IMO, it needs to be a quick easy low cost solution to change if need be.


hope this helps you abit

im running omex 600 so ecu props would be okay ,but im looking to getting a mrk2 plenum an cutting it and weld the 4no of inlet to the mrk1 or weld a plate to bolt it together ,but need a mrk2 first to have a really good look into it ,,