Tuesday, September 23, 2008

Considering upsized injectors

I'm seriously considering getting higher flow injectors to be able to run straight E85 with no CELs.

Figuring out what the injectors are, and what higher flow injectors are compatible, is no easy thing.

It seems that the stock injectors are Siemens part number 12790827. I've seen them quoted at 355cc/min, 32#/hr, 34#/hr, and 36#/hr. Not sure which they are, and I'm just going to assume 36#/hr.

These injectors are also used in the supercharger Cobalt SS.

Just doing the calculation, at 210 hp, with a .5 BSFC and 80% of capacity, you need 33#/hr injectors, so 36 seems right to me.

Now I need to figure out a compatible higher flow injector. Just comparing air-fuel ratios between gas and E85, I need about a 55# injector. Maybe a little less, since we know that the Saab injector is optimized for E10, not gas.

5 comments:

2.0T Boi said...

Can you look up the Saab part numbers for the injectors on a flex fuel engine? That would seem to solve the problem, especially since it's (almost) QED from your earlier post that the rest of the fuel system would accept e85. While you're at it, order up one of those yellow gas caps too.

buzzcut said...

Dude, you're frickin' brilliant. Seriously. That's a good idea.

Off to the saabcentral forums...

Dave said...

Don't know what the injectors would cost, but wouldn't it be easier to buy one of those conversion kits sold online. I'm just guessing that if the injectors were too big they might have a bit of trouble running on straight gas if you were suddenly unable to buy E85 at a time when you need some fuel.

buzzcut said...

Injectors are considerably cheaper than those kits. They might be half as much.

The choice of injector has to be done with a little engineering. But as long as your results keep you within the +-25% long term fuel trim window that the ECU has, I don't think you'll have any trouble running gas and E85. It will be a flex fuel vehicle.

And unlike those kits, you'll never need to flip a switch to change from one fuel to the other.

dave said...

I found a kit online that I can install on my car with a V8 that will still cost me under 400 dollars, and there is no switch to flip, its all automatically controlled by the kit. I'm thinking of getting one of those this next spring, as long as ethanol is still cheaper than gasoline.