What injectors for M50 Supercharger upgrade

[Herbmiester 909]

As it says I am looking to fit a centrifugal supercharger to my my M50B25TU. The supercharger is a Chinese made jobbie that I am still gathering info on but according to the guy I am getting it off is rated to around 400 HP. My goal is 280-300 WHP at 6-8 psi so I am not looking to go crazy here. I am looking at using a programmable War Chip and with some help from friends will tackle the mount and piping at home. So what size injectors will I need? I was thinking around 450cc's but as I am a bit of a novice on injectors I would be interested to know if there is a donor 6 cyl car I can get them from? A mate has is using Holden injectors from the Supercharged Ecotec motor for his M20 turbo build any other options out there that I might find cheap. I will get them serviced of course.

[Toast 117]

Browse the US BMW forums, I've read that there's a certain v8 that runs injectors that are a direct match. They were popular with turbo swaps on the US S50.

[jeffbebe 1559]

Plenty of M50 supercharger kits available. Why not see if one of the companies that offers these will sell a set of injectors separately?

[Herbmiester 909]

Yes I could just buy injectors of them but surely there are other cars that have higher flowing injectors that are compatible, I figure its just a case of working out what those vehicles are. I know Holdens use Bosch injectors and thats what I am researching now.

[Herbmiester 909]

Ok Holden looks like the solution, I found a set of Ecotec V6 s/C injectors just as mentioned above that are 42 lb (440 cc) rated and support 350 FWHP at 80% duty cycle.

[handgrenade 189]

At what fuel pressure?

[Herbmiester 909]

42- 59 PSI is what Holden specifies, from memory an E36 is 42 or 50 PSI cant remember exactly.

Edited March 6, 2015 by Herbmiester

[thorburn 120]

I'd like to be the fist to say this seems like a bad idea.
But I don't want to be too un-helpful so

There are plenty of injectors out there that will be a direct swap. Some might need adapters to fit but still not a tough ask. To find a high flowing injector look for a high powered engine with not a lot of cylinders. Personally if i were you i'd go for some type of motorbike injectors. They're readily available and are usually(on better performing bikes) some of the nicest injectors around. They probably will need an adapter and a plug swap(just make sure you get high impedance injectors).
There are plenty of fuel injector calculators. http://www.rceng.com/technical.aspx

Is this going to get a remap or aftermarket ecu?
Is the car automatic?

I would've thought the trickiest part would be guessing the pulley size needed for an unknown supercharger.

[Herbmiester 909]

As stated I will use a war chip these are fully programmable including vanos. I used one of the online programs to check the suitability of the Holden 42lb injectors and they will support up to 350 crank hp at 80% duty cycle. This was using Bsfc set up for supercharging. They are Bosch injectors and appear to have the same connectors as Bmw I will compare them over the weekend but the appear to be dimensionally identical, they just flow twice what the original BMW M50 injector does.

I used this page for the calculations.

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

Edited March 6, 2015 by Herbmiester

[handgrenade 189]

Considered a second fuel rail and another set of stock injectors?

[Herbmiester 909]

I guess its possible but considering I will be remapping it seems easier just to use bigger injectors.

[No name user 379]

Hate to be the downer but you wont make that power on 6-8 psi closer to 18psi maybe also if its belt driven blower you lose up to 33% crank power to turn the supercharger

[Herbmiester 909]

Yes probably a bit optimistic at those levels however 8-10 psi is getting 300 fwhp with both Rotrex and Vortech superchargers in the US with nice increases in torque so we will have to see what this Chinese supercharger is capable of. Its basically a T4 from with a gearbox on the back. A mate has stripped it down and had an engineer have a look at it and he said it looked well made, I guess I will find out. But I feel comfortable with the Chip as at least I can control spark fuel etc effectively.