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festy wrote:

Zedric wrote: And since when is 1 TB better than 2?

When the single TB is used with an MPFI setup, but the 2 are TBI

True, but MPFI with 2 TB's to even out airflow across the ports would be better. The setup I'm trying to achieve is not TBI, it's twin TB's with the injectors closer to the head although they would still be further away from the ports than I would like, the only option I have is to get injector bungs put on the manifold right next to the head port inlets, that would be best.

I did some research into Delco TBI options for my early headed 308 not so long ago, and came to the conclusion that although it seemed easier on the face of it, MPFI was the simpler (and cheaper) option when everything was added up.

VL400 wrote:An 808 can drive low impedance injectors using peak an hold - how many I dont know, its used on some local Camiras but they only use 1 I think?

Yes the 4 cylinder TBI cars only had one, from what I found I think it can run two, but...

Jayme wrote:you can set the resistors on thememcal to put it into TBI injeciton mode, which will fire once every ignition event and so give you the accurate fuelling in tbi setups.

you need to do this, which presents a problem with getting good fuel delivery from idle to WOT with only two large injectors. The GM V8 TBI setups in the US ran an ECU with two injector drivers and alternated the injectors at low RPM simply to deliver a small enough amount of fuel and keep decent control over it. Not sure if this would be less of an issue with a smaller engine, I wouldn't think it would make much difference...?

I don't know whether the VR auto ECU can do low impedance injectors and TBI mode, if so that could solve some problems. Otherwise if you came across a factory US ECU set up for TBI that might be a good starting point, but they don't come up often here and cost a lot more than a complete '808 setup.

For my own purposes I decided that on top of all that I wanted the benefits of MPFI over TBI anyway, so I got the manifold machined for injectors and will run an air-only 4 barrel throttle body.

VK_3800 wrote:I did some research into Delco TBI options for my early headed 308 not so long ago, and came to the conclusion that although it seemed easier on the face of it, MPFI was the simpler (and cheaper) option when everything was added up.

VL400 wrote:An 808 can drive low impedance injectors using peak an hold - how many I dont know, its used on some local Camiras but they only use 1 I think?

Yes the 4 cylinder TBI cars only had one, from what I found I think it can run two, but...

Jayme wrote:you can set the resistors on thememcal to put it into TBI injeciton mode, which will fire once every ignition event and so give you the accurate fuelling in tbi setups.

you need to do this, which presents a problem with getting good fuel delivery from idle to WOT with only two large injectors. The GM V8 TBI setups in the US ran an ECU with two injector drivers and alternated the injectors at low RPM simply to deliver a small enough amount of fuel and keep decent control over it. Not sure if this would be less of an issue with a smaller engine, I wouldn't think it would make much difference...?

I don't know whether the VR auto ECU can do low impedance injectors and TBI mode, if so that could solve some problems. Otherwise if you came across a factory US ECU set up for TBI that might be a good starting point, but they don't come up often here and cost a lot more than a complete '808 setup.

For my own purposes I decided that on top of all that I wanted the benefits of MPFI over TBI anyway, so I got the manifold machined for injectors and will run an air-only 4 barrel throttle body.

your right, I think modding the manifold for 6 injectors would be the best option.