205 Si - fuel injection - timing questions

[natumbri]

Hi all,

In a 720 deg cycle, with 0 being TDC on cyl 1 immediately before the induction stroke begins:
- at what point does the injector on a SPI Peugeot 205 Si fire for cyl 1 (maybe BTDC?)?
- does it fire 4 times per cycle (ie once for each cylinder) or maybe 2 times (ie once for each half of a 720 deg cycle) or maybe just once per cycle or something else?
- does the timing of the injector opening change (eg relative to rpm or throttle position or manifold pressure)

Cheers
Nik

 

[PeterT]

I really have no idea, but given it only has a crank angle sensor and no cam position sensor, I'd suggest it fires twice per 720º. ie every time those missing teeth come around. Graham Wallis is the Si expert.

 

[natumbri]

I really have no idea, but given it only has a crank angle sensor and no cam position sensor, I'd suggest it fires twice per 720º. ie every time those missing teeth come around. Graham Wallis is the Si expert.

Yeah, that seems likely to me, too.

I was wondering if you could replace the SPI manifold with a GTi manifold, and some how wire up the injectors in some combination (maybe with a little bit of flip-flop logic) so that you could retain the standard ecu.

 

[matara]

I am thinking of putting DanST bike carbs on our Si engine to give it a better intake as I believe the SP manifold is a bit restrictive on the Si, and it might free up some ponies and give it a better sound. I would expect putting a GTi Manifold means your need all of the other Bosch mult-point injection stuff including ECU and wiring to get it to work properly.

 

[natumbri]

I believe the SP manifold is a bit restrictive on the Si

Yes, I think that is the conventional wisdom

I would expect putting a GTi Manifold means your need all of the other Bosch mult-point injection stuff including ECU and wiring to get it to work properly.

And I think that is also the conventional wisdom. But I just wonder if it couldn't be done another way...

 

[PeterT]

You can certainly bolt a GTi manifold and TB straight up. You'd need to split the injector pulse into four. Such a load would be too much for the injector driver in the ecu. There's probably a way to do it electronicall, but I don't know. I'd do it properly and fit an aftermarket ecu, which could fine tune both the fuel and ignition. Then where do you stop? Next you'll be wanting a GTi cam and then a 1.9L crankshaft. That would be nice though.

 

[natumbri]

Haha. Then where do you stop, indeed.

I was thinking
- 2 banks of 2 fuel injectors
- the 2 banks are fired 180deg out of phase
- each bank is fired once per crank revolution
- half the fuel required is delivered each fire

One bank could be fired based on the crank sensor, exactly the same as the SPI. But you'd need some logic to work out when you are 180deg around and then fire the other bank.

All a bit silly, when you can just get a perfectly good aftermarket ECU. Or use a GTI ECU with the Si ECU doing spark. Or bike carbs. Or throttle bodies. Or ...

Cheers,
Nik